Review and critical comparative evaluation of moist air thermophysical properties at the temperature range between 0 and 100 °C for Engineering Calculations Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-12-15 P.T. Tsilingiris
Although a broad range of heat transfer and engineering calculations require the use of thermophysical and transport properties of humid atmospheric air at the temperature range between 0 and 100 °C, there is a relatively considerable gap in the scientific literature concerning their precise evaluation. Even though numerous theoretical procedures and formulas have been developed for the mixture property evaluation, relatively very few devoted to the dry air/water vapor binary mixture can be found in the literature. In an earlier publication, simple procedures were employed to evaluate and investigate their influence on the heat and mass transfer calculations, while a decade ago alternative, more refined kinetic theory procedures were presented for the calculation of moist air properties. These which were found in a fairly good agreement with the very few and incomplete earlier published measurements, were algebraically fitted to allow the evaluation of saturated mixture properties of moist air. The present investigation aims at the validation of the proposed moist air properties based on comparisons with results from numerous theoretical procedures or data derived by employing commercial computer software and more recent experimental measurements. However, since no recent experimental results have appeared in the literature in the meantime, the validation was based on extensive comparisons and critical consistency evaluation of calculated results from various developed models. It was found that the proposed moist air properties are in a fairly good agreement with data from most of the numerous calculation processes reported in the literature, while certain methods and models appear to be physically invalid. The so derived results were fitted by algebraic correlations, allowing the accurate evaluation of moist air thermophysical properties at any relative humidity ranging from dry conditions up to saturation level in 10% steps. These are recommended until new precise validating measurements appear in the literature.
Modeling techniques used in building HVAC control systems: A review Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-12-12 Zakia Afroz, GM Shafiullah, Tania Urmee, Gary Higgins
The appropriate application of advanced control strategies in Heating, Ventilation, and Air-conditioning (HVAC) systems is key to improving the energy efficiency of buildings. Significant advances have been made in the past decades on model development to provide better control over the energy consumption of system components while simultaneously ensuring a satisfactory indoor environment in terms of thermal comfort and indoor air quality. Yet it is an ongoing challenge to select and implement the best-suited modeling technique for improving the control strategy of HVAC systems. For the development of modeling research it is important that the building research community is informed about the role, application, merits, shortcomings and outcomes of different modeling techniques used in HVAC systems. Even though several review articles have been published on modeling techniques, the weaknesses and strengths of these modeling techniques, along with performances of developed models associated with research studies, have rarely been identified. This study presents a critical review of current modeling techniques used in HVAC systems regarding their applicability and ease of acceptance in practice and summarizes the strengths, weaknesses, applications and performance of these modeling techniques. Additionally, the performance and outcome of some of the developed models used in real world HVAC systems have been discussed. From the extensive critical review it is evident that almost every model has a major/minor shortcoming generated from assumptions, unmeasured disturbances or uncertainties in some system properties. This review aims at highlighting the shortcomings of existing application-based research on HVAC systems, and accordingly, recommendations are presented to improve the performance of building HVAC systems.
Integration of electric vehicles and management in the internet of energy Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-12-08 Khizir Mahmud, Graham E. Town, Sayidul Morsalin, M.J. Hossain
Due to the environmental and energy crisis, many countries around the world are electrifying transportation, which will significantly change the way the current power grid operates. It is expected that the deployment of future smart grids will allow two-way energy and information flows through plug-and-play operation of small distributed mobile power generators like electric vehicles (EVs) to benefit the prosumers and at the same time make the grid more efficient and robust. However, the issues associated with the energy and information transfer, battery technologies, battery charging schemes, their standards and management need to be addressed in order to achieve the full benefits of EV integration in the future smart grids and internet of energy (IoE) with local renewable generation. As the current grid with existing infrastructure cannot ensure maximum benefits from EVs, this paper reviews the EV technologies, their connectivity, impacts on grid and standards required for the efficient and economic operation of EVs with distributed energy resources in the IoE. The evolution, comparison, and storage potential of EV technologies are thoroughly discussed. This paper also extensively reviews the connectivity issues, for example current EV charging schemes, software tools required to design smart charging, associated challenges, and possible solutions. The architecture of distributed energy management schemes with EVs and the IoE is discussed in detail. Finally, the standards related to EV integration, energy transfers, and safety aspects are provided. Based on the comprehensive review, future directions are put forward which will be useful for researchers and engineers working with EVs.
Testing environmental Kuznets curve hypothesis in Peru: The role of renewable electricity, petroleum and dry natural gas Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-12-08 Manuel A. Zambrano-Monserrate, Carlos A. Silva-Zambrano, Jose L. Davalos-Penafiel, Andrea Zambrano-Monserrate, Maria Alejandra Ruano
This paper analyzes the relationship between GDP (gross domestic product), carbon dioxide emissions from the consumption of energy, total renewable electricity consumption, dry natural gas consumption, and total petroleum consumption (all variables are in per capita terms) for Peru during 1980–2011. The Autoregressive Distributed Lag (ARDL) methodology was used to test a cointegration relationship, and the Granger causality test, based on the vector error correction model (VECM), was used to test for causality. An innovative criterion proposed by Narayan and Narayan (2010) was employed to test the Environmental Kuznets Curve (EKC) hypothesis. The study does not support an inverted U-shaped EKC relationship. For this reason, it is urgent that Peru designs environmental policies that minimize the emission of greenhouse gases (GHG) using alternative energy sources e.g. solar, wind, hydraulics, among others. In addition, we found an unidirectional causality relationship between CO2 emissions and their determinants.
Real options analysis of investment in solar vs. wind energy: Diversification strategies under uncertain prices and costs Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-12-06 Ardjan Gazheli, Jeroen van den Bergh
In this paper we study a community or firm considering to diversify its investment in two distinct renewable energy technologies, namely wind and solar PV electricity. We assume technological learning curves as a function of cumulative capital investment. A real options approach is applied as it takes into account uncertainty about prices and learning, as well as irreversibility associated with investment decisions. We investigate three different cases, dealing with uncertainty about future electricity prices, and uncertainty about the speed with which learning drives the costs of wind and solar electricity down. We assess the minimum threshold for the stochastic price and the maximum electricity production cost that makes it optimal for the firm to invest in the two technologies. The results show that the learning rate affects the option to invest in but reducing critical threshold for exercising it. The greater the amount of capital invested, the more learning stimulates earlier exercising of the option to invest. The firm will then anticipate the option to invest and exercise it for lower critical threshold values if all capital is invested in one technology. If capital investment is diversified, the option should be exercised at a higher critical threshold. More uncertainty in energy prices or technology costs postpones the option to invest. Although investing in both solar and wind may be profitable under particular conditions of price and cost uncertainty, the theoretically optimal strategy is generally investing in only one technology, that is, solar or wind, depending on their relative initial costs and learning rates. This suggests that the practice in most countries of diversifying renewable energy may reflect a mistaken strategy.
Fuzzy rough set based energy management system for self-sustainable smart city Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-12-06 Sumedha Sharma, Amit Dua, Mukesh Singh, Neeraj Kumar, Surya Prakash
A smart city (SC) is a modernized urban community, which incorporates information and communication technology (ICT) into the existing physical infrastructure. It offers reliable and uninterrupted services such as-intelligent transport and energy conservation to its residents. Among the various services offered, a continuous and widespread supply of electricity draws the maximum attention. Moreover, a substantial amount of this electricity is utilized by heating and cooling loads, making them significant contributors of global warming. Keeping focus on these points, a SC is modeled in this paper, wherein electricity consumption is minimized by modifying the traditional heating and cooling system. The proposed system collects solar heat and recovers industrial waste heat to deliver heating and cooling services to the SC residents. For the purpose of storing the heat energy, a seasonal thermal energy storage (STES) system has been proposed. The proposed STES system supplies stored thermal energy to heat-driven cooling and heating equipments. Moreover, central energy management system (CEMS) is also modeled for monitoring, regulating and controlling the flow of thermal energy. The designed CEMS consists of a Fuzzy rough set controller for scheduling heat to cater the instantaneous thermal energy requirements. Fuzzy rough set has been used because it eliminates the issues of vagueness, uncertainty, and ensures efficient real-time computations. Results depict that the heat energy obtained from solar thermal collectors and industrial wastes is able to meet the requirements of the SC after scheduling it using Fuzzy rough set algorithm.
Comparison of 100% renewable energy system scenarios with a focus on flexibility and cost Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-12-06 Wesley Deason
In this study, a particular class of energy system scenarios assuming 100% renewable energy (RE) are selected and compared. The purpose is to compare the relative characteristics of the scenarios, focusing on the amount and types of flexibility used and the predicted electricity generation cost. The approach included the screening of 45 studies (some of which contained multiple scenarios) to down-select to 8 studies, which used high-fidelity short-term energy system models. The compared scenarios applied many strategies for providing flexibility, which was found to be a crucial and significant component of a 100% RE system. Accordingly, only two of the fifteen examined scenarios contained a variable generation fraction greater than 65% of total scenario capacity (73% and 69%). Predicted electricity costs varied drastically in all regions. Some studies provided multiple scenarios (including business-as-usual scenarios and costs) that could be compared. In 3 out of the 4 studies including a business-as-usual cost, the 100% RE scenarios were found to be between 41% and 104% more expensive. The fourth study showed electricity costs to be the same for a 100% RE system and business-as-usual system, and the 100% RE system to be 62% cheaper when externalities are included.
Green concrete partially comprised of rice husk ash as a supplementary cementitious material – A comprehensive review Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-12-06 Blessen Skariah Thomas
The production of cement depletes natural resources, consumes high energy and emits huge amounts of green house gases. It accounts for almost 7% of the global carbon dioxide emissions, as the production of one ton of ordinary Portland cement releases approximately one ton of carbon dioxide. Due to the severe environmental pollution and health hazards associated with the cement and construction industries, they are under the strict scrutiny from the governments and environmentalists. Rice husk is an agricultural waste, whose natural degradation is restricted due to the irregular abrasive surface and high siliceous composition. It is not appropriate to be used as a feed for animals due to the low nutritional values. If dumped as landfill, they can take a lot of area and become a major challenge to the environment. If they are disposed by burning, the ashes can spread to the surrounding areas, create pollution and destroy the natural beauty. One of the possible solutions for the disposal of rice husk is to convert them into rice husk ash and incorporate them into cement based materials. The partial inclusion of rice husk ash (RHA) for cement is found to be durable, environmental friendly and economically viable. This paper presents an overview of some of the published results on the successful utilization of rice husk ash as a supplementary cementitious material and the properties of such concrete at fresh and hardened stages. Studies indicate that there is a promising future for the use of rice husk ash in normal, high strength and self compacting concrete as it shows high strength, low shrinkage and permeability, high resistance to carbonation, chloride, sulfate and acidic environments. The summery and discussions provided in this paper should provide new information and knowledge on the applications of greener and sustainable rice husk ash concrete.
Enhanced boiling heat transfer by nano structured surfaces and nanofluids Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-12-06 C.G. Jothi Prakash, R. Prasanth
In order to meet the future energy demands many interesting techniques have been reported in literature for improving boiling heat transfer using nanoparticles and nano-structured surfaces. The mode of heat transfer and efficiency of water cooled reactors, direct steam generators can be substantially modified by this new technology. Boiling heat transfer is an area of increasing interest in many engineered heat transfer and cooling applications. Nucleate boiling is the efficient heat transfer region in pool boiling. The critical heat flux changes boiling mechanism from efficient mode to inefficient mode by forming a vapor film over the heater surface that leads to boiling crisis. The actual mechanism that creates this boiling crisis still remains a grey area. The CHF parameter cannot be avoided in boiling heat transfer applications; instead it can be postponed by adopting fluid and surface modification techniques. This review analyzes the present status of nano-modification for enhancing the pool boiling and critically compares the experimental results with the theoretical predictions. The existing theoretical models are not satisfactorily explaining the experimental investigations. New investigation techniques and better correlation between the modified surface properties to the heat flux is inevitable for further improvement.
Natural convection induced by the absorption of solar radiation: A review Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-12-02 I. Amber, T.S. O'Donovan
Natural convection primarily driven by the absorption of thermal energy known as penetrative or thermo-convection is a topic that generates attention due to its importance in various physical systems. A very common example of where this process can be found in geophysical systems such as lakes, where radiation induced natural convective transport have been seen to influence water temperature, biological activity and water quality. The present paper reviews previous analytical, experimental and numerical studies reported in literature concerning natural convection driven by absorption of thermal radiation. Many of the reviewed studies were motivated by the interest of investigators to understand the physical processes in volumetric absorption thermal radiation in a fluid layer process and its associated energy transport. In this class of problems, temperature fields are generally described as non-linear and the associated fluid flow is considered rather complex owing to coupling between the direct absorption of radiation and fluid flow. Parametric investigations for the effect of various parameters of interest such as the Rayleigh numbers, Prandtl numbers, spectral nature of incident radiative flux, optical depth, fluid absorptivity, aspect ratio, albedo and boundary emissivity on natural convection have been investigated. The overall aim of the current review is to present a comprehensive review of the previous and recent approaches applied in the investigations of radiation induced natural convection in reservoirs. The paper also aims to contribute to improving the understanding of the physical processes, heat transfer and fluid dynamics associated with the thermal energy deposition into a fluid layer. The paper is also highlight the potential application of this concept to help keep solar energy capture costs to a minimum and inform efficient designs of energy systems based on the concept of direct absorption of thermal energy inside a fluid layer.
Review of water based vapour absorption cooling systems using thermodynamic analysis Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-29 P.S. Arshi Banu, N.M. Sudharsan
Heat based vapour absorption cooling technology is the most appropriate, efficient and eco-friendly way of harnessing solar heat energy, as many cooling load requirements are always in phase with the accumulated solar heat. The performance improvement of such systems has currently become a high research priority, to ensure conservation of electrical energy. Performance of these systems depends on two important factors: i) selection of suitable working fluid pair and ii) adopting appropriate configurations and multiple cascaded ‘effects’ of the absorption cycles. The Thermodynamic analysis (TDA) or the first law analysis is the broad indicating tool to predict the performance behavior and suitability of a vapour absorption system for a particular application. In the present work, a detailed literature survey has been conducted on various water based working fluid pairs and their cascaded effects; single-effect, double-effect, triple-effect, 1.5-effect and half-effect vapour absorption cooling systems based on TDA. This review paper focuses on two areas: (1) the importance of conducting TDA and choosing right parameters in TDA for performance enhancement in order to overcome the drawbacks of conventional systems. This will help in finding out system for solar based applications, air-cooled applications and determining solutions to overcome crystallization, corrosion, compactness and initial cost; and, (2) as generator temperatures represent the amount of solar heat energy required, considered as key parameter. For various water based vapour absorption systems, the possible range of generator operating temperature requirements and its corresponding attainable COP values has been reviewed and tabulated. This review data can serve as a source of reference in selecting a suitable solar collector with available fluid pair and configuration or vice-versa.
Bioremediation of textile wastewater and successive biodiesel production using microalgae Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-26 Tahir Fazal, Azeem Mushtaq, Fahad Rehman, Asad Ullah Khan, Naim Rashid, Wasif Farooq, Muhammad Saif Ur Rehman, Jian Xu
Microalgal biodiesel has emerged as an environment friendly alternative to the existing fossil fuels. The commercial production of this biodiesel is still challenging due to several technical and economic issues, which span from mass cultivation of microalgae to the biodiesel production. Mass cultivation is the most critical step in terms of water and nutrient requirement. Industrial wastewater such as textile wastewater (TWW) is a cheap source for water, which additionally contains necessary nutrients (phosphate, nitrates, micronutrients etc.) and organic dyes (potential carbon source) for algae cultivation. The application of microalgae for biodiesel production employing single objective strategy is not sustainable. Microalgae can be effectively employed to bioremediate TWW (dyes and nutrients removal) and to produce biodiesel from grown microalgae. This process integration (bioremediation-biodiesel production) can potentially improve biodiesel production and wastewater treatment. However, this process coupling needs to be thoroughly investigated to identify and optimize critical process factors (algal species, cultivation and harvesting methods, bioremediation mechanism etc.). This study has reviewed the status of TWW as potential source of water and nutrients, role of different algal species in the bioremediation of TWW, different cultivation systems, harvesting and biodiesel production methods. This review also suggests future research and development challenges for coupled textile wastewater treatment and microalgal biodiesel production.
Solar energy dust and soiling R&D progress: Literature review update for 2016 Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-26 Suellen C.S. Costa, Antonia Sonia A.C. Diniz, Lawrence L. Kazmerski
The objective of this literature review and survey is to provide a compilation and assessment of recent published reports for solar-electric device soiling R&D, to extend and update the compendium covering 2012–2015 we published last year. This review provides a comprehensive listing of the publications with references for 2016—with some preliminary 2017 publications that have appeared at the time of this writing. Photovoltaics (PV) and concentrating solar (thermal) power (CSP) technologies are covered. To guide the reader, tabulated information on the investigative focus of the studies, the location, the duration (if pertinent), the solar-device type, key findings and other useful information within the report is presented.
A review on heat and mechanical energy harvesting from human – Principles, prototypes and perspectives Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-23 Maoying Zhou, Mohannad Saleh Hammadi Al-Furjan, Jun Zou, Weiting Liu
The rapid development of smart electronics has enabled their applications into such fields as portable instruments, wearable electronic devices, implantable medical devices and even assistive biomedical devices. As a result, power requirements of these devices continuously increase to such a degree that currently used batteries can not meet. Recently the heat and mechanical energy available in human daily activities have received increasing attention by researchers as alternatives. This paper looks into the physical mechanisms, materials and devices involved in possible energy harvesting from human motion. Heat and mechanical energy available in human daily activities are summarized to give an overview of the potential of energy harvesting from human motion. In addition, different energy transducing principles are discussed. Moreover, various proposed or demonstrated energy harvesting prototypes related to human motion are reviewed and discussed with respect to their working principles, device structures, implementations and performances. Finally, trends, challenges, applications and future developments of energy harvesting from human motion are discussed.
Integrated effects of PM2.5 deposition, module surface conditions and nanocoatings on solar PV surface glass transmittance Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-22 Ke Sun, Lin Lu, Yu Jiang, Yuanhao Wang, Kun Zhou, Zhu He
Aerosol deposition is highly concerned recently due to its significant impact on surface glass cleaning, glass transmittance and energy conversion of building-integrated photovoltaics (BIPV). Thus, this paper reviewed direct transmittance degradation works of PV module surface glasses, and employed several integrated and improved experiment and model methods to investigate the correlation effects of PM2.5 deposition dynamics, tilt angles, surface conditions and self-cleaning TiO2 nanocoating on glasses. Series of physical models from ambient aerosol concentration to deposition density and transmittance reduction were extended or newly developed. Measured and modeled data could inter-validate with each other and literature results. The usage condition of Al-Hasan model was discovered as 0 < a p < 0.10 for particle projected-area fraction under clustering particle projected-area fraction a p c p ≤ 5 % . Ranging from 0 to 18.7 μg/cm2, deposition densities with the most reductions (50–91%) were found under the combination of wet and nanocoating conditions due to effects of water film and low adhesive force. Generally, the average deposition densities decreased 19–47% with the increase of each 30° tilt angle for different surface properties. Finally, six linear empirical models were obtained with decreasing slopes of 0.001544–0.001841 between fine aerosol deposition density and transmittance ratio. These observed phenomena and derived models would be useful for solar energy, building illumination or heat-transfer, and BIPV industries.
Planning in a changing environment: Applications of portfolio optimisation to deal with risk in the electricity sector Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-22 Rodrigo Pérez Odeh, David Watts, Yarela Flores
Today's quickly changing world forces society to deal with uncertainties that produce high levels of environmental, social, and economic risks, thereby jeopardizing sustainable development. Portfolio optimisation is an effective tool for formally dealing with such uncertainties, because the social and private optimum is not found by analysing cost/returns and risks of individual assets, projects, actions or plans, but rather requires analysing them all together in the form of a portfolio. This paper presents a review of portfolio optimisation applications from the perspective of energy regulation in an attempt to guide the electricity sector towards sustainable development. Liberalized electricity markets have different sources of uncertainties, ranging from the traditional (e.g. fuel prices, electricity demand, and resource availability, etc.) to the latest sources of risks linked to a society that is more concerned about sustainability. We have found multiple research opportunities, especially in spatial modelling, transmission, and renewable generation, as well as others related to new social and environmental impacts and risks. The portfolio literature available to date excessively simplifies the power system. Supply, demand, and transmission modelling in portfolio analysis are not consistent with planning models, and therefore produce conflicting results. Additionally, despite abundant literature that analyses renewable complementarity, actual portfolio optimisation models ignore this effect, which leads to suboptimum portfolios. Environmental and social costs and risks, such as air and water pollution, land use, community values, and public opposition, among others, have also been ignored.
Production of hydrogen from biomass and its separation using membrane technology Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-22 Gaweł Sołowski, Marwa.S. Shalaby, Heba Abdallah, Ahmed.M. Shaban, Adam Cenian
Hydrogen is an important raw material for chemical industry and feasible renewable energy carrier that could replace fossil fuels. However, the specie seldom exists in a form of pure H2. Therefore, to obtain hydrogen in volumes suitable to be used as a raw material it is necesary to decompose hydrogen-rich compounds. The carbohydrate-rich biomass can be an important source of hydrogen by applying the process of dark fermentation. In this paper potential ways of hydrogen production from organic wastes (biomass) by means of dark fermentation are reviewed and discussed. The bacteria used for dark fermentation are enlisted, characterized and compared. The pretreatment processes and various reactor designs are analyzed and discussed. The hydrogen separation by membrane method (which can provide the most pure hydrogen) are presented. The paper describes recent achievements in optimizing parameters, conditions and reactors used to industrialize dark fermentation.
A review on distributed generation allocation and planning in deregulated electricity market Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-21 A.K. Singh, S.K. Parida
Currently, distributed generation (DG) based on conventional energy sources and renewable energy sources (RESs) have played a vital role throughout the world. Energy policies are promoting distributed energy resources such as energy efficiency, increasing the number of DG installations and RESs planning. It can be observed that the load growth rates of countries are rapidly increasing. However, uncoordinated management of these alternative energy sources can put a severe stress on the power grid. To overcome from this problem, DGs are the best options for managing the need of energy. In this work, the robustness, sustainability and reliability of DG has been discussed with various aspects including different contingency scenario. Contingency analysis of a power system is a major action in power system planning and operation. This review covers the recent works done in the area of integration of DGs with various scenarios in electrical power systems. The main objective of this work is to study how to achieve a better integration of flexible demand as demand response, demand side management (DSM) with DGs and make the grid proficient. It then reviews the key results in this field and some of the interesting research challenges can be addressed are also acknowledged.
Imported technology and CO2 emission in China: Collecting evidence through bound testing and VECM approach Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-21 Danish, Bo Wang, Zhaohua Wang
Several studies have investigated the determinants of CO2 emission; however, prior research has been neglected to examine the emission of CO2 due to the trade of goods and services and royalty and licensing fees. To do so, the present work contributes to research stream by investigating the relationship between imported technology and environmental degradation within the time span of 1980–2011 in the case of China. Based on the Auto Regressive Distributive Lag (ARDL) model and Vector Error Correction (VECM) Granger causality approach we draw an inference that imported technologies mainly contributes to CO2 emission in the long run path for China. The long run causality results originates bi-directional causality between imported technology and CO2 emission. Moreover, in the long run, feedback hypothesis is also detected between energy consumption and CO2 emission. To ensure the stability of model and reliability of results for policy implication numerous significant tests are carried out. This study suggests that Government of China needs to expand input in R&D for higher technological strength and intellectual property rights management capacity, which will be favorable for the protection of the environment.
Advances and challenges in water management within energy systems Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-21 Omar J. Guerra, Gintaras V. Reklaitis
Energy systems face a growing vulnerability to the availability and quality of water sources as a consequence of rising energy demand and increasing climate variability. The vulnerability of energy systems to water utilization constraints could be mitigated by the effective design and implementation of water management strategies in energy conversion process and supply chain systems. Based on a broad literature review, this study provides a comprehensive examination of the recent advances in methodologies to support decision-making processes involving water management in the energy sector. Water management issues which require more attention by the research community, include: (i) development of decision-support models for biofuel supply chains that deal with water scarcity scenarios, (ii) integration of wastewater quality variability into the design and planning of water management strategies for the development of unconventional fossil fuels, (iii) improvements in the efficiency of cooling systems, and (iv) integration of decision-support tools with climate and weather models for the optimal design, planning, and operation of integrated water and energy supply chains, especially power systems. The systematic targeting of the aforementioned issues in the near future is critical and requires the joint efforts of the energy modeling as well as the weather and climate research communities, which to date have principally addressed water management issues from their own individual perspectives.
Enhanced thermophysical properties of multiwalled carbon nanotubes based nanofluids. Part 1: Critical review Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-21 Hessam Taherian, Jorge L. Alvarado, Ehsan M. Languri
Recently reported anomalous thermal conductivity enhancement in carbon nanotube nanofluids is in disagreement with the known physical theories for heat transfer fluids. Many researchers have modified existing theoretical models using recent experimental data to highlight the importance of certain physical mechanisms that should be prevalent at the nanoscale. In this study, available experimental data have been mapped and the discrepancies among them have been highlighted and compared using the available physical models. The proposed theories seem not capable of predicting the experimental data with reasonable accuracy. Analysis reveals that the measurement techniques used by researchers in the area of nanofluids should be standardized. In Part 2 of this study, collected experimental data indicate that the Maxwell's theory predictions can accurately be used to determine the effects of using nanoparticles on thermal conductivity.
Energy storage system: Current studies on batteries and power condition system Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-20 Chao Zhang, Yi-Li Wei, Peng-Fei Cao, Meng-Chang Lin
To maximize the introduction of renewable energy, introducing grid energy storage systems are essential. Electrochemical energy storage system, i.e., battery system, exhibits high potential for grid energy storage application. A battery energy storage system is comprised of a battery module and a power conversion module. This paper starts by reviewing several potential battery systems, as well as an advanced aluminum-ion battery that currently has promising prospects in the electrochemical energy storage system. The characteristics of the batteries are reviewed and compared, including the materials, electrochemistry, performance and costs. The application prospect of the batteries is discussed. The paper summarizes the features of current and future grid energy storage battery, lists the advantages and disadvantages of different types of batteries, and points out that the performance and capacity of large-scale battery energy storage system depend on battery and power condition system (PCS). The power conversion system determines the operational condition of the entire energy storage system. The new generation wide bandgap semiconductor for power electronic technology is discussed from the perspective of performance, topology, model and non-linearity and is compared to the traditional silicon-based semiconductor. Finally, the application prospect of the new generation semiconductor technology in the energy storage system is indicated. This paper concludes the application status of the energy storage system in the renewable energy power generation and indicates the critical problems that need to be addressed during the construction and operation of the storage system.
Opportunities for greater energy efficiency in government facilities by aligning decision structures with advances in behavioral science Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-20 Laura Delgado, Tripp Shealy
In 2007, Executive Order 13423 mandated 30% energy and emission reductions for all government facilities by 2015. Unfortunately, the government fell short of their goal by 9%. Their approach through mandates and federal legislation focused predominantly on new construction and major retrofits to existing facilities. To meet future energy and emission reduction goals, more emphasis on facility management is needed. The government manages over 370 million square feet of facilities each year. The daily decision process for government facility managers is full of competing interests, such as maintenance needs (preventative and corrective), limited operating budgets, time constraints to make decisions, and bounded rationality about energy consumption and savings. By understanding how these decisions are made and the cognitive bias that may occur, advances in facility management decision making can reduce energy consumption. Cognitive biases to the decision making process such as loss aversion, anchoring, and status quo bias are explored and an approach to overcome them is offered, a tactic called choice architecture, meaning restructuring decision environments to align with behavioral decision theory. Examples of choice architecture, such as, enabling procurement systems to query green products, changing default settings in mechanical systems, and requiring the use of pay back period calculators to account for cognitive limitations of the decision maker, are suggested and supported by behavioral science research to help direct facility managers towards energy efficient choices. This approach, through choice architecture, holds potential to yield relatively low-cost solutions (they do not require new mandates or laws) to support greater energy reduction in government facility management. This merging of literature from behavioral science to facility management is meant to open new avenues of interdisciplinary research.
HVDC links between North Africa and Europe: Impacts and benefits on the dynamic performance of the European system Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-20 Mokhtar Benasla, Tayeb Allaoui, Mostefa Brahami, Mouloud Denaï, Vijay K. Sood
In the last decade, there have been several initiatives for the deployment of cross-Mediterranean HVDC (High Voltage Direct Current) links to enable the transmission of electrical power from renewable energy sources between North Africa and Europe. These initiatives were mainly driven by the potential economic, environmental and technical benefits of these HVDC interconnections. In previous studies on these projects, some technical aspects of critical importance have not been addressed or studied in sufficient detail. One of these key aspects relates to the impact and possible benefit of these HVDC links on the dynamic performance of the European system which is the major focus of this paper. Several issues relating to the dynamic performance of the system are addressed here. Based on the experience gained from existing AC/DC projects around the world, this paper shows that the HVDC links between North Africa and Europe can greatly improve the dynamic performance of the European system especially in the southern regions. In addition, some challenges on the operation and control of these HVDC links are highlighted and solutions to overcome these challenges are proposed. This review paper, therefore, serves as a preliminary study for further detailed investigation of specific impacts or benefits of these interconnections on the overall performance of the European system.
Modified waste egg shell derived bifunctional catalyst for biodiesel production from high FFA waste cooking oil. A review Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-20 Nasar Mansir, Siow Hwa Teo, Umer Rashid, Mohd Izham Saiman, Yen Ping Tan, G. Abdulkareem Alsultan, Yun Hin Taufiq-Yap
Global energy crisis are as a result of gradual depletion of fossil fuel reserves, coupled with population growth in developing countries. Besides, fossil fuels are not environmentally benign as they are associated with problems, i.e. global warming, high toxicity and non biodegradability, hence it is considered as non sustainable source of energy. Without doubt, biofuel-based energy is a promising long-term energy source that can reduce the over dependence on fossil fuels as a result of feedstocks availability and renewability. However, biodiesel production from vegetable oil using the traditional homogeneous catalytic system is no longer defensible by industries in the near future, particularly due to food-fuel rivalry and ecological problems related to the conventional homogeneous catalytic system. This review presents a comprehensive step by step process of converting waste cooking oil (WCO) to biodiesel, using modified waste egg shell catalyst. The modified waste egg shell derived bi-functional catalyst could easily be removed from the fatty acid methyl esters (FAME) with limited environmental effects. The new modified catalytic system is able to convert the high free fatty acid (FFA) content waste cooking oil to FAME efficiently under moderate reaction conditions. Utilization of waste cooking oil as a feedstock for biodiesel production will reduce the food security issues that stem the biodiesel production from food-grade oil. Moreover, it will reduce the total production cost of the FAME due to its low cost. The major objective of this article is to demonstrate the current state of the use of heterogeneous bifunctional acid/base catalyst to produce biodiesel from green and non-edible waste cooking oil. At the end of the article, perspectives and future developments are also presented.
The renewables cost challenge: Levelized cost of geothermal electric energy compared to other sources of primary energy – Review and case study Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-20 Christoph Clauser, Markus Ewert
Comparisons of fix and variable costs for converting different forms of primary into electric energy performed by national and international agencies as well as by a major German electrical utility consented in concluding: geothermal electricity produced from natural steam or permeable hot water reservoirs is among the cheapest renewable forms of electricity. However, in years to come, geothermal electricity may find itself restricted to the limited number of regions worldwide which feature these particularly favorable reservoirs. This would exclude most of the continental land mass of the earth which is hot but lacks natural steam or hot water reservoirs. This is due to the current lack of proven technology for engineering man-made geothermal reservoirs where natural ones do not exist. At the same time, proven technologies for generating wind and solar electricity are readily available. This may turn out to be a serious competitive disadvantage for geothermal energy as fossil primary energies are being replaced by renewables. Therefore, dedicated and proactive funding of geothermal technology development is required at much larger scale than previously for making geothermal electricity competitively available almost everywhere.
Advanced low-carbon energy measures based on thermal energy storage in buildings: A review Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-16 Jesús Lizana, Ricardo Chacartegui, Angela Barrios-Padura, Carlos Ortiz
Thermal energy storage and management in builtable dings play a major role in the transition towards a low-carbon economy. Buildings are the largest energy-consuming sector in the world, where heating and cooling are around 60–70%. This paper provides a comprehensive review of advanced low-carbon energy measures based on thermal energy storage technologies for heating and cooling applications in buildings. With the aim of structuring and identifying the most promising solutions towards low-carbon energy buildings, a global classification of technologies for thermal storage and management is carried out. The most advanced commercial solutions, emerging technologies, and recent research activities reported in the literature and international projects are analysed. The main achievements are reported together with the status of research and the most promising solutions in the short- and long-term. It is a comprehensive review of the most outstanding applications, operation modes, implementation techniques and their potential benefits. Solutions based on sensible and latent heat storage show a higher development status and the best performance, through the use of aerothermal energy in free-cooling ventilation systems, solar energy through small-scale thermal energy storage units, and large-scale underground thermal energy storage systems. For an optimal integration in buildings, they should be combined with heating and cooling generation technologies through smart demand-side management strategies. Regarding thermochemical storage applications for buildings, despite the high energy density of thermochemical storage materials and their reduced heat losses, at the current research stage, the final volume of prototypes is highly penalized by the required auxiliary components. Moreover, recent studies report low-to-moderate efficiency values and poor heat transfer rates after a relatively large number of storage cycles. Therefore, although promising developments are expected in this field, at the present time the greater advances with thermochemical storage processes have been obtained on cooling applications based on solar sorption cycles and large-scale systems.
Environmental efficiency for 192 thermal power plants in the Yangtze River Delta considering heterogeneity: A metafrontier directional slacks-based measure approach Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-16 Xingle Long, Chao Wu, Jijian Zhang, Jing Zhang
This study investigated environmental efficiency considering heterogeneity for 192 thermal power plants in the Yangtze River Delta of China from 2009 to 2011. We evaluated environmental efficiency using metafrontier directional slacks-based measure. We also testify whether heterogeneity for environmental technology increased or decreased among different provinces. We proposed a regional, time, and coal intensity effects hypothesis to explore the determinants of environmental efficiency through bootstrapped truncated regression. We found that heterogeneity for environmental technology widened from 2010 to 2011. Shanghai had the highest environmental efficiency. Environmental efficiency increased from 2009 to 2010, and declined in 2011. Coal consumption intensity negatively impacted environmental efficiency. It is critical that we should decrease the rate of coal use, and expand technology spillover of production technology and environmental technology among different provinces and power plants.
Energy efficiency of a micro-generation unit of electricity from biogas of swine manure Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-15 Felipe Pinheiro Silva, Samuel Nelson Melegari de Souza, Danilo Sey Kitamura, Carlos Eduardo Camargo Nogueira, Rodrigo Bueno Otto
The containment in pig farming generates a large volume of effluent that can be treated by anaerobic digestion. To use the biogas generated in the process, in electricity generation, a better understanding of the variables involved is necessary. The objective of this study was the evaluation of biogas production parameters, power generation, performance of the generator group in the biogas conversion into electric energy and the avoided cost of electric energy of a pig farming property. Parameters of concentration, biogas production and consumption, and generation of electric energy were monitored, and the information generated was stored in a database. The results have indicated an average daily production of 443 m3, with an average of 0.10 m3 of biogas per pig and an average concentration of 68% methane. The average of electric energy generation was 324.5 kWh/day, and the efficiency of the generator was 17% with an average active power of 70 kW and a daily operation of 6.5 h. The avoided cost by self-consumption of electric energy generated in the property was R$ 13718.20, and during the monitoring period there was a total generation of electric energy of 70.5 MWh, of which 26.6 MWh were exported to the distribution network. The study also emphasizes that the appropriate choice of sensors and the methodology for monitoring and collecting data continuously could lead to an important data to use in correlated studies concerning generation of electricity from biogas.
Exploring the marketability of fuel cell electric vehicles in terms of infrastructure and hydrogen costs in Spain Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-14 J.J. Brey, A.F. Carazo, R. Brey
This paper aims to analyze the costs associated with the initial transition to the use of hydrogen as a fuel for road transportation in Spain from a double perspective: that of the investor in the required infrastructure, and that of the end-user who will have to pay for the fuel. To this end, different types of hydrogen refueling stations are taken into consideration, as are strategies for production and delivery of the gas. Scenarios of distributed production (at the actual hydrogen fueling stations) and centralized production (at medium or large-sized plants that produce hydrogen that is subsequently delivered to different fueling stations) are contemplated. Hydrogen production systems based on the reforming of fuels and also on the electrolysis of water are analyzed; renewable and non-renewable systems are compared. Lastly, the case of a Spanish city is analyzed from both perspectives. This analysis allows estimation of the magnitude of the gap between fuel cell road vehicles and gasoline vehicles in terms of fuel price for this country.
Maize ethanol production in Brazil: Characteristics and perspectives Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-14 C.T. Eckert, E.P. Frigo, L.P. Albrecht, A.J.P. Albrecht, D. Christ, W.G. Santos, E. Berkembrock, V.A. Egewarth
This paper propose the inclusion of a raw material in Brazilian fuels sector. The corn is used in other countries to produce ethanol, in Brazil has other business demands, not being employed as proposed. The work also highlights the energy, economic, social and environmental role in production ethanol from corn, especially for the country´s development, minimizing losses in logistics and grain exports. Comparatively corn is more expressive as bioenergy associated with sugarcane in the Brazilian conditions, because other raw materials have limitations: sugar beet does not have viable cultivation; rice, cassava and wheat are insufficient; and sweet sorghum requires technological adjustments to have significant production. The co-products that arise from the production of ethanol are nutritionally rich, causing less pressure on corn commodities trading.
Potential thermochemical conversion of bioenergy from Acacia species in Brunei Darussalam: A review Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-14 Ashfaq Ahmed, Muhammad S. Abu Bakar, Abul K. Azad, Rahayu S. Sukri, Teuku Meurah Indra Mahlia
As the demand for energy increases and fossil fuel resources are depleted, the search for clean sources of energy has intensified worldwide. This is coupled with a strong global desire to reduce CO2 emissions to curb global warming. Brunei Darussalam is committed to reduce its CO2 emissions but currently utilizes fossil fuels to meet almost all of its energy requirements. This situation provides good incentives to search for renewable and sustainable resources to produce energy in the country. Acacia species are exotic species that have invaded and spread to natural habitats in Brunei Darussalam. Acacia species are a sustainable source of high quality biomass feedstock to produce bioenergy in the country. Hot tropical weather of the country is highly suitable for the rapid growth of Acacias without requiring any major agricultural input. This study reviews the thermochemical conversion of Acacia species especially; Acacia mangium and Acacia auriculiformis to produce biofuels and bio-products. The prospective of using Acacia biomass as feedstock in pyrolysis, gasification, liquefaction and combustion is also discussed. Acacia biomass is a sustainable and renewable energy resource for Brunei Darussalam to be exploited for energy requirements and can be beneficial for the economy of the country by providing new investment and employment opportunities.
Hierarchical structure and bus voltage control of DC microgrid Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-14 Zhikang Shuai, Junbin Fang, Fenggen Ning, Z. John Shen
Compared to AC microgrids, DC microgrids have the advantage of higher reliability and efficiency and are convenient to connect with various distribution energy resources (DERs). Concentrated in different time-scale control objectives, a multi-level control structure can guarantee that none of the control objectives affect each other. Considering this, an extensive review on the hierarchical structure of the DC microgrid is applied, and two typical control structures are presented in detail: two-level control architecture and three-level control architecture. Furthermore, the primary, secondary, and tertiary control levels are systematically analyzed and classified according to different control objectives. In order to improve the control capability of the primary control level, an energy efficiency improved DC bus voltage control strategy is proposed to increase the energy efficiency and system reliability. Finally, a distributed DC microgrid model is established and simulated in the RT-LAB to verify the effectiveness of the proposed control strategy.
Control techniques and the modeling of electrical power flow across transmission networks Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-14 Konstantinos Syranidis, Martin Robinius, Detlef Stolten
The ever greater share of renewable energy sources (RES) in the European energy market stresses the transmission grid to its limits with rising frequency. Therefore, there is a pressing need for a spatially and temporally detailed model of the European power system to serve as a basis for investigating the efficient integration of RES. Here we outline a far-reaching description of transmission grid operation and present a review of approaches developed for modeling the physical power flows and the respective congestion management techniques that control them. By this, we hope to equip the interdisciplinary energy research community with a better understanding of power systems and corresponding modeling tools, thus enhancing their respective efforts. Additionally, a literature review and classification of existing studies on these topics is included in the paper as well. The analysis shows that the fundamental modeling components determining power flows across power systems include the electricity market, the inter-zonal power trading and the intra-zonal congestion management models, where a complete incorporation of all of them requires an iterative or multi-level approach. However, due to the high complexity of such an approach, most common and computationally efficient strategies apply integrated approaches using linearized descriptions for the physical flows.
A review of performance modelling studies associated with open volumetric receiver CSP plant technology Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-14 Jean-Francois P. Pitot de la Beaujardiere, Hanno C.R. Reuter
Open volumetric receiver (OVR) concentrating solar power (CSP) plant technology may hold a number of significant advantages over other CSP technologies, as a consequence of its use of air as a heat transfer fluid. Yet the technology faces some key technical challenges that need to be overcome in order for its potential to be realised. As documented in prior literature reviews, these challenges have attracted substantial research attention in a variety of disciplines. However, literature specifically concerned with the performance modelling of OVR plants and their constituent systems has not been comprehensively reviewed in a standalone body of work. The objective of this study, therefore, is to provide a resource that catalogues modelling studies associated with overall plant performance, as well as the performance of those elements of the technology that are still undergoing technical maturation. Based on the classification and dissemination of these studies, the state of OVR plant technology and the developmental challenges that remain have been reported. In addition, future avenues of research that have yet to be properly addressed in the literature have been identified.
Improving the performance of refrigeration systems by using nanofluids: A comprehensive review Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-14 Atul Bhattad, Jahar Sarkar, Pradyumna Ghosh
In view of energy security and environmental concern, the performance of refrigeration system needs to be improved, which can be done by modifying either the systems or the properties of primary and secondary working fluids. Recently, the nanofluids or hybrid nanofluids have gained interest in many engineering fields due to its excellent thermophysical properties, which can be easily used in refrigeration and air conditioning systems by many roles for performance improvement. This review summarizes the researches on preparation and characterization of nanofluids, various thermophysical and electrical properties (density, heat capacity, viscosity, thermal conductivity, surface tension, electrical conductivity, freezing characteristics, etc.) of nanofluids. Applications of nanofluids in the refrigeration systems as refrigerant, lubricant and secondary fluid are well-grouped and discussed. Finally, the challenges and opportunities for future research are identified, which will be useful for the newcomers and manufacturers in this field.
What makes consumers adopt to innovative energy services in the energy market? A review of incentives and barriers Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-14 Anna Kowalska-Pyzalska
The paper provides a review of the incentives and barriers of a successful adoption of innovative energy services (IES) in the energy market. Although IES can have different attributes and roles, they still have a lot in common with each other. On the other hand, the literature suggests that to achieve large market penetration rates of IES, the consumers must be firstly aware of them. They must be also supported by the access to reliable information and advice to limit their confusion of choice. The perceived difficulty of adoption has to be reduced to encourage consumers to get interested in the services. Also the distribution channels of the innovations, namely social influence in the consumers’ social networks and advertisement in mass-media should be effectively used to boost the diffusion. We analyze a great number of research studies, field experiments and mathematical models in order to firstly summarize the findings related to incentives and barriers of IES adoption among customers, then to recognize recent trends in examining these services and modeling and finally to propose some strategies that could boost the diffusion of IES. We argue that to overcome the barriers of adoption, the entities involved in creating and offering IES (e.g. policy makers, energy suppliers and power system operators) should find a way to offer and promote these services together. Such a strategy can bring a synergic effect and increase the financial and non-financial benefits to the consumers and hence increase their interest and engagement.
A review on bismuth telluride (Bi2Te3) nanostructure for thermoelectric applications Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-13 Hayati Mamur, M.R.A. Bhuiyan, Fatih Korkmaz, Mustafa Nil
Bismuth Telluride (Bi2Te3) is basically known as an efficient thermoelectric material. Nowadays, it has been attracted a great deal of interest in energy harvesting, chip cooling, chip sensing and other field of material science because of its potential applications. In order to produce Bi2Te3 nanostructure, a number of methods such as solvo and hydro thermal, refluxing, straight forward arc–melting and polyol methods have been employed. Among of them, the solvothermal method has been one of the most common methods to fabricate Bi2Te3 nanostructure in thermoelectric applications. But the development of device–quality material has been a challenging task for the researchers, yet. For this reason, this paper provides a review of current research activities on Bi2Te3 nanostructure growth by several methods and its characterization through theoretical and analytical aspects. Moreover, the paper handles a systematic and intensive research work to develop and understand the materials in nanostructure forms.
The insight views of advanced technologies and its application in bio-origin fuel synthesis from lignocellulose biomasses waste, a review Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-11 Kifayat Ullah, Vinod Kumar Sharma, Mushtaq Ahmad, Pengmei Lv, Jurgen Krahl, Zhongming Wang, Sofia
The present research article notably describes the evolution of biofuels while its preliminary attention will focus on the next generation biofuel from lignocellulose biomasses wastes. Categorically, the biochemical, thermo-chemical technologies particularly the chemicals, heat, microorganism, fermentation, enzymes and technical processes are addressed. In biochemical technologies, the topics concern to hydrolysis, pre-treatment, microorganism based fermentation and the integration techniques are also discussed. While, in thermo-chemical technologies, different research parameters particularly the developmental process and systematic analysis will be dealt with. The mandatory and technical aspects of R&D, available technologies, economic study, limitation and understanding of certain technologies etc. will also be presented in detail in the proposed review article.
Recent progress in flexible perovskite solar cells: Materials, mechanical tolerance and stability Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-11 Idris K. Popoola, Mohammed A. Gondal, Talal F. Qahtan
Portable electronic devices with standalone power sources are increasingly demanded. Flexible photovoltaics devices for solar energy conversion remain the most attractive option to cater for this demand. Flexible solar cells have the advantages of light-weight, roll-to-roll processing, conformability, bendability and wearability. Following the excellent power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) on rigid substrates, flexible perovskite solar cells (flex-PSCs) have gained remarkable research attentions. Successes have been recorded for flex-PSCs with conversion efficiency reaching 17.3%. Attainment of commercialization of flex-PSCs and integration into electronic gadgets require proper materials selections and processing techniques coupled with good resistance to deformation and long-term durability. This work reviews (i) comprehensively, materials and processing techniques used for the fabrication of flex-PSCs; (ii) mechanical tolerance of flex-PSCs and (iii) stability of flex-PSCs in different environmental conditions.
Development of bubble absorption refrigeration technology: A review Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-11 Xi Wu, Shiming Xu, Mengnan Jiang
This study reviews the developments of bubble absorption refrigeration technologies. Firstly, the principles of the bubble absorption refrigeration systems as well as bubble absorbers were introduced; And then bubble behavior characteristics during the absorption process were observed and expressed graphically; Thirdly, available bubble absorbers were investigated, modeled and compared; In addition, current and potential refrigerant-absorbent pairs in the bubble absorption refrigeration systems were analyzed, and about fifty fluids were involved totally. What’s more, methods of enhancing bubble absorption performance were researched, and also the influence mechanisms of these physical and chemical methods were explained; Finally, the development of bubble absorption refrigeration technologies were discussed from the aspects of driving energies, performance enhancement and application extension. The tendency of bubble absorption refrigeration technologies is expected to be high efficiency, miniaturization, and intellectualization. The expressed contents in this paper are expected to be useful for readers in the fields of absorption refrigeration technologies and the medium-low grade heat utilization technologies, especially for the equipment operating in the unsteady conditions (e.g. swing, bump, jolt, scram, etc.).
Geothermal energy resources in Poland – Overview of the current state of knowledge Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-10 Anna Sowizdzal
Geothermal energy, which is one of renewable energy sources, is the internal heat of the Earth. Currently in Poland hydrogeothermal resources are utilized, for which the energy carrier is hot groundwater produced with the wells. Petrogeothermal energy resources, i.e. resources of heat accumulated in rocks for which the energy carriers are media injected through wells into the hot rock formations has not yet been utilized in Poland. However the research work tending to assess the possibility of utilization of this type of energy was carried out. The results are particularly important in the context of forecasts of geothermal energy sector development. Although technology of petrogeothermal resources utilization is in the experimental stage, is considered to be the technology of future. In Poland, low-temperature geothermal resources occurs, related mainly to sedimentary rocks – sandstones, limestones, dolomites, rarely with igneous rocks (crystalline, volcanic). Depending on the hydrogeothermal parameters these resources may be used for different purposes: first of all for heating, but also for therapeutic and recreational purposes. Research of the possibilities of using geothermal resources (both petro and hydrogeothermal) for electricity production are carried out. The article presents the actual state of knowledge about geothermal resources in Poland as well as possibility of them utilization for different purposes. In many parts of the Poland significant unused potential of geothermal waters and energy exist.
Isothermal membrane-based air dehumidification: A comprehensive review Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-10 Ming Qu, Omar Abdelaziz, Zhiming Gao, Hongxi Yin
Isothermal membrane-based air dehumidification (IMAD), a recent emerged air dehumidification technology, separates the moisture from the humid air by using a selective membrane, through which only vapor molecules can transfer from the one side of the membrane at a high concentration to the other side at a low concentration. The IMAD process has superior performance potentially in energy and economic than other traditional dehumidification technologies. This paper comprehensively reviews the literature on IMAD including membrane characteristics, membrane configuration, membrane-related mass transport mechanism, and system design and operation, as well as the mass transfer modeling. State of the art in the IMAD is presented and finally the recommendations of future research are provided.
Metabolic engineering of microorganisms for biofuel production Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-10 Parastoo Majidian, Meisam Tabatabaei, Mehrshad Zeinolabedini, Mohammad Pooya Naghshbandi, Yusuf Chisti
Microorganisms directly and indirectly contribute to production of diverse biofuels. Heterotrophic microorganisms are being used for commercial production of biofuels such as biogas and fuel alcohols from organic matter. Photosynthetic microorganisms convert inorganic carbon and water to potential fuels (e.g. fuel alcohols, biohydrogen) and fuel precursors (e.g. biomass, starch, lipids). Only a few microbial processes are used for commercial production of biofuels, but this will certainly change with the enhanced production capabilities being achieved through microbial metabolic engineering. Processes that previously required multiple steps of feedstock pretreatment and subsequent conversion to fuel are being consolidated into single-step microbial processes using metabolically engineered species. Microorganisms with the ability to produce fuels from feedstock they could not use previously, are being engineered. This review discusses some of the metabolic engineering approaches being used to enhance the commercialization potential of microbial biofuels including fuel alcohols, biodiesel and biohydrogen. At present, all biogas production relies on native populations of methanogens and this does not seem likely to change in the near term. Potential fuels from microalgae, cyanobacteria and other photosynthetic bacteria, whether native or engineered, have distant prospects of commercial use. Metabolically engineered yeasts surface displaying various hydrolytic enzymes appear to hold the greatest potential for near term commercial use in generating bioethanol from starch, pretreated lignocellulose and other polysaccharides. The bacterium Zymomonas mobilis metabolically engineered to make bioethanol from pentose sugars is already being commercialized. Other similar examples are likely to emerge as more engineered microorganisms become available.
A review of human thermal comfort experiments in controlled and semi-controlled environments Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-10 Stijn Van Craenendonck, Leen Lauriks, Cedric Vuye, Jarl Kampen
There are three main methods to improve thermal comfort in existing buildings: modeling, experiments and measurements. Regarding experiments, no standardized procedure exists. This article provides an answer to the question: “What is the most common practice for human thermal comfort experiments in (semi-)controlled environments?”. A total of 166 articles presenting results on 206 experiments were collected and analyzed to extrapolate the most common practice. The results are arranged in five main themes: subjects (e.g. number and age), climate chamber (e.g. surface area), thermal environment, experimental procedure (e.g. phases and duration), and questionnaire. A typical experiment was found to employ 25 subjects and to take place in a permanent climate chamber with a floor area of 24 m2 During the experiment, 3 air temperature variations are used. The test itself takes 115 min, but is preceded by a preconditioning and conditioning phase. The subject is given a questionnaire at regular intervals of 15 min, with questions highly dependent on topic, but including thermal sensation and comfort vote rated on a bipolar 7-level scale. Number of subjects, gender distribution, type and floor area of the climate chamber and utilization rate of the scale for rating thermal comfort and sensation are all linked to topic, as well as number of different air temperatures, whether conditioning is employed and questions in the questionnaire. Several links between experiment characteristics reciprocally are also identified.
A study on solving the production process problems of the photovoltaic cell industry Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-10 Sang-Bing Tsai, Jian Yu, Li Ma, Feng Luo, Jie Zhou, Quan Chen, Lei Xu
The failure mode and effects analysis (FMEA) is a mode that adopts systematic methods to determine the possible problems in products or processes, and analysis of the impacts of these problems on products or processes can facilitate the adoption of improvement and prevention measures. Nevertheless, FMEA focuses on factor problems, and can only solve problems according to the importance of the factor. If several failure mode factors take effect or interact simultaneously, it will be difficult to evaluate the analysis. Taking the examples of Chinese photovoltaic cell manufacturing companies, this study integrated three research methods and proposed a new FMEA-IPA-DEMATEL analysis model. First, FMEA was applied to identify the factors to be improved. Second, IPA was employed to discuss the improvement of the importance and performance of the factors. Third, DEMATEL was used to explore the causal relation and interaction among the factors. Finally, this study helped decision-makers identify the core problems to be improved and gave suggestions on the problem-solving sequence. The FMEA-IPA-DEMATEL model combined the strengths of the three methods, and uses the minimum resources to prioritize the projects to be improved, in order to enhance management performance.
Applications of the infrared thermography in the energy audit of buildings: A review Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-10 Elena Lucchi
From a wide range of bibliography (148 publications composed by books, guidelines, scientific papers, and other documents), the study presents a critical review of the use of the infrared thermography (IRT) survey in the building energy audit. After explaining its historical growth, the applicability of passive and active approaches has been described, considering well-established and emerging techniques, general procedures, types of IR-camera used, technical issues, and limitations. The passive approach is the most common to detect thermally significant defects. Thus, a specific procedure for the energy audit has been reported, matching different standards, guidelines, and professional advice. Similarly, recurring energy related problems are toughly presented (i.e. thermal characterization of buildings; thermal bridging, insulation level, air leakage and moisture detection; indoor temperature and U-value measurements; human comfort assessment). Finally, advantages and potential sources of errors as well as future trends in the use of IRT for the energy audit have been described. The research aims to serve as a reference for energy auditors and thermographers, to decide upon the best procedure for detecting specific energy defects.
Multi-model ecologies for shaping future energy systems: Design patterns and development paths Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-10 L.A. Bollinger, C.B. Davis, R. Evins, E.J.L. Chappin, I. Nikolic
As energy systems grow more complex, modeling efforts spanning multiple scales, disciplines and perspectives are essential. Improved methods are needed to guide the development of not just individual models, but also multi-model ecologies – systems of interacting models. Currently there is a lack of knowledge concerning how multi-model ecologies can and should be designed to facilitate adequate understanding of energy system complexity and its consequences. Via an analysis of twelve multi-model initiatives both within and outside the energy domain, this paper elucidates possible design patterns and development paths for multi-model ecologies. The results highlight two broad paths to developing energy system multi-model ecologies, one prioritizing interoperability and the other prioritizing diversity. The former path facilitates the efficient development of models spanning multiple scales and (to a degree) disciplines, and can ease systematic testing of assumptions. The latter is suited to bridging traditional disciplines and perspectives and advancing knowledge within the interstices of different knowledge communities. It is furthermore suggested that a combination of diversity, connectivity and hierarchy in multi-model ecology composition is central to enabling the development of complex webs of models capable of addressing the complexity of real-world energy systems.
An assessment of recent multilevel inverter topologies with reduced power electronics components for renewable applications Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-10 Jagabar Sathik Mohd.Ali, Vijayakumar Krishnaswamy
The combination of multilevel inverter with renewable energy source power generation is paid more attention among the researchers, because multilevel inverters are widely accepted power converters in for high-power applications. The conventional multilevel inverters are highly implemented in industries, and the success of this has motivated to create newer topologies with the reduced overall power electronics components. In this paper, recent multilevel inverter topologies with reduced number of switches are taken into account and to find a suitable topology for photovoltaic (PV) and wind energy applications. Finally, this paper gives a pathway for the upcoming researchers to consider the design issues and challenges in the development of new multilevel inverter topologies.
A review on challenges in the assessment of geomechanical rock performance for deep geothermal reservoir development Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-10 Ingrid Tomac, Martin Sauter
This review paper summarizes recent advances and challenges in the assessment of rock behavior and performance in deep low-permeability and high-temperature geothermal reservoirs. Geothermal energy systems for electricity production target deep rock between ca. 2 km and 5 km depth to obtain sufficiently elevated temperatures. Rock permeability enhancement faces many challenges, and therefore the development of Enhanced Geothermal Systems (EGS) still represents a pioneering effort. The potential and advantage of EGS above conventional geothermal reservoirs is its independence of the location that supplies sufficient heat and fluid. Several issues prevent the successful application of EGS technology. First, the effects of non-uniform in-situ stresses and loading history on rock fracturing are not well understood. Second, the role of rock anisotropy, heterogeneity and thermal effects on rock properties in the design of hydraulic fracturing operations is not clear. Third, the reduction of induced seismicity effects raises safety and public acceptance issues. This manuscript formulates outlines for future research directions. Specifically, the recommendations focus on the development of tools for better understanding and mitigating problems, which occur during stimulation of deep geothermal reservoirs.
Experimental analysis of thermal performance of solar collectors with different numbers of heat pipes versus a flow-through solar collector Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-09 E. Azad
This paper presents a comparative study of the experimental analysis of two heat pipe solar collectors with different numbers of heat pipes and a flow-through collector. For this purpose, three collectors were designed, constructed and tested side-by-side under various environmental conditions. In this study the three collectors selected were: first, a collector with six heat pipes, type(I); second, a collector with twelve heat pipes, Type (II); and third, one flow-through solar collector, type (III). These collectors were simultaneously tested outdoor according to ASHRAE standard 93–1986. Tests showed that the efficiency of collector type (II) was higher than the other two. The thermal efficiency of flow-through solar collector (III) at mid-day was higher than collector type (I); however, the efficiency of collector type (I) was higher than the conventional collector type (III) in the morning and in the afternoon. There are two methods to increase the efficiency of heat pipe collectors, the first is to increase the number of heat pipes and the second is to increase the effective absorber area by proper design of the heat pipe condenser.
Fermentative biohydrogen production and its byproducts: A mini review of current technology developments Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-09 Chiu-Yue Lin, Thi Mai-Linh Nguyen, Chen-Yeon Chu, Hoang-Jyh Leu, Chyi-How Lay
This work highlighted the latest studies on fermentative biohydrogen production and its byproducts from (1) the APEC-BPT/ABBS-2015 Conference (held on September 2015 in Taiwan) with partly from (2) the ABBS 2016 Conference (held on October 2016 in South Korea) and (3) recent journal publications. Some novel technologies for enhancing biohydrogen production and integration systems for agricultural or industrial waste/wastewater treatment and bioenergy production were shared and discussed by ten keynote speakers. It has shown that the recent research trends are focusing on biohydrogen production enhancement, via a two-stage of photo-dark fermentation, a photosynthetic bacteria biofilm or an integration system of effectively using fermentation effluent. Real wastes/wastewaters such as palm-related biomasses were used as the feedstock for future application purpose. Moreover, some other recent journal reports indicate the importance of developing biohydrogen technology for generating sustainable biohythane, in enhancing energy recovery via two-stage anaerobic digestion and having the potential gradually to become a major hydrogen-generating technology for future development of green economy. In commercializing the biohydrogen technology, some key issues need to be solved are feedstock source exploration, improving bio-H2 production, developing H2 separation technology, utilization of bio-H2 and recovery of fermentation bioproducts. The role of algae in bio-H2 production technology was also discussed.
Towards sustainability in water-energy nexus: Ocean energy for seawater desalination Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-09 Zhenyu Li, Afreen Siddiqi, Laura Diaz Anadon, Venkatesh Narayanamurti
Seawater desalination is an important option for addressing the world's water supply challenges. Current desalination plants use enormous quantities of energy and cause a number of environmental issues. Renewable energy options, mostly solar and geothermal systems, have been examined in detail to supply the energy needed for water desalination. The co-location benefit of energy derived from the ocean to power seawater desalination processes is appealing. However, the promise and potential of ocean-based power generation for desalination systems has not been investigated in detail. The development of such systems has been limited due to technological and economic limitations of energy harvesting and transport as well as device maintenance under water. In this paper, we review the state of the art of ocean energy in desalination. It explores different sources of energy from the ocean that include electricity generation, as well as mechanical force and thermal energy and salinity gradients that can also be directly harnessed for powering the desalination processes. We also examine recent advances in scaling up for commercial deployment, and discuss relevant cost, environmental and social concerns. The great potential of ocean energy for seawater desalination in terms of diverse energy forms, flexible integration methods and various deployment strategies can provide important environmental, water and social benefits for seawater desalination, thus promote sustainability in water-energy nexus. The use of ocean energy in desalination applications could benefit the future development of ocean energy technology in renewable energy sector.
Global modern monitoring systems for PV based power generation: A review Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-09 M.Mahbubur Rahman, J. Selvaraj, N.A. Rahim, M. Hasanuzzaman
Photovoltaic system is widely installed to increase the share of renewable energy as well as to reduce the environmental impact of fossil fuel based energy. Photovoltaic (PV) is one of the most potential renewable energy based power generation systems. Monitoring of PV system is very important to send information that allows owners to maintain, operate and control these systems to reduce maintenance costs and to avoid unwanted electric power disruptions. Different monitoring systems have been introduced with the time following different requirements. Circuit complexity, availability of friendly graphical user interface, easy to understand system architecture, maintenance facility and customization ability for end user differ from system to system along with cost issues. This paper provides an overview of architectures and features of various PV monitoring systems based on different methods. There are various technologies for PV monitoring and control, developed as for commercial use or research tasks. It has been seen that a large portion of the work is done on classifications, for example, Internet based Monitoring using Servers, TCP/IP, GPRS and so forth. There are various methodologies for data acquisition, for example, PLC (Power Line Communication), PIC, Reference cell, National Instruments etc. Various requirements are considered while selecting a proper monitoring system for an application. Review of various monitoring technologies with system attributes and working structures have been discussed to get a clear view of merits and demerits of existing PV monitoring systems. All the systems discussed in this paper have pros and cons, and these systems were developed following different requirements. In the end, a particular cost effective monitoring system using Arduino microcontroller has been proposed considering both research and user level requirements from perspectives of cost, availability of parts/modules and features, compatibility with sensors and end-devices etc.
Heterogeneous sulfur-free hydrodeoxygenation catalysts for selectively upgrading the renewable bio-oils to second generation biofuels Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-09 Xin Li, Xingyi Luo, Yangbin Jin, Jinyan Li, Hongdan Zhang, Aiping Zhang, Jun Xie
Biodiesel as a substitute of traditional petroleum-derived liquid fuels has been put into use in recent years. However, the first generation biodiesel (fatty acid methyl esters) with high oxygen content is inconvenient for large-scale use due to its incompatible nature with fossil fuels. As a result, green biodiesel (the second generation biofuel) prepared from catalytic hydrodeoxygenation (HDO) of the first generation biodiesel has been gradually developed. The biodiesel after deoxygenation which has a great number of advantages is similar to petroleum fuel in composition, so it can be employed directly in fuel industry. To obtain the expected products, accessible production processes and suitable catalyst systems are needed. In this review, we first make an analysis on the pathways and processes of deoxygenation reactions including hydrodeoxygenation, decarboxylation and decarbonylation. Selectivity to reaction pathways has a close relationship with raw materials, catalysts or reaction conditions. The special goal of this review is to highlight the advances in the heterogeneous sulfur-free catalysts used for deoxygenation, including the sulfur-free noble metals, non-noble metals, metal phosphides, metal carbides and metal nitrides. We thoroughly discussed the different performances of these developed catalysts in the deoxygenation reactions, such as activity, selectivity and stability. Fundamental mechanisms over sulfur-free catalysts, including experimental comparison of different active phases and calculations by Density Function Theory (DFT), were also addressed. This review also involved effects of different support materials, composition, structure optimization, water and H2 pressure on the HDO activity and silectivity, and detailed information about catalyst deactivation. It is expected that this review can provide some new design and modification strategies for fabricating highly active,selective and durable earth-abundant HDO catalysts for the substainable production of green bio-diesel.
Sweet sorghum-a promising alternative feedstock for biofuel production Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-09 Rouf Ahmad Dar, Eajaz Ahmad Dar, Ajit Kaur, Urmila Gupta Phutela
The key principle in resource management is sustainability which consists of operational robustness, attenuation of environmental footprint and socio-economic considerations. Dependence on fossil fuels is unviable due to their continuous depletion all over the world and also the inexperienced greenhouse gas emissions related to their utilization. Therefore, the continuous initiatives geared towards developing various renewable and probably carbon neutral biofuels as energy resources are being taken up. Alternate energy resources such as 1st generation biofuels derived from terrestrial crops like sugarcane, sugar beet, corn and wheat place a colossal stress on global food markets, but this potential food versus fuel conflict is palliated by using sweet sorghum as a bioenergy crop. It can be processed into both biofuel and valuable co-products, thus meeting the various requirements of food, fuel and fodder. This paper mainly reviewed the technologies for bioethanol production from sweet sorghum, focussing on its potential benefits as feedstock for ethanol production over other substrates and recent advancements to enhance ethanol yield. It also reviewed the advances in pretreatment along with the novel process of ethanol production from sweet sorghum stalks, biogas production from sweet sorghum and environmental cum socio-economic aspects. No doubt, there are outstanding issues related to ethanol production and yield, still sweet sorghum derived bioethanol could progressively substitute a significant proportion of the fossil fuels required to meet the growing energy demand.
Metaheuristic algorithms for PV parameter identification: A comprehensive review with an application to threshold setting for fault detection in PV systems Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-08 Dhanup S. Pillai, N. Rajasekar
Precise model parameters being the prerequisite for realizing accurate PV models, parameter identification techniques have gained immense interest over the years among the researchers specializing in PV systems. The application of various promising metaheuristic algorithms to optimize the model parameters have lightened up the scope of further enhancements in this field. Ever since, numerous metaheuristic algorithms have deployed for this purpose. With handful of techniques available in this regard, this paper takes up an initiative to review the existing metaheuristic algorithms based parameter extraction techniques with an emphasis on their compatibility, accuracy, convergence speed, range of parameters set and their validating environment. Based on the analysis conducted, accurate models available for 17 different industrial solar cells/modules are identified. Inspired by this review, an unidentified gateway between parameter extraction and fault detection in PV systems have been identified; and has further extended this review to differentiate some models that can help the researchers to achieve accurate, efficient and rapid fault detection. This review is a valuable gathering of statistics from the various researches carried out in PV parameter extraction which can assist enhanced researches for fault detection in PV systems as well.
Inter-fuel substitution path analysis of the korea cement industry Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-08 Sung-Yoon Huh, Hyejin Lee, Jungwoo Shin, Donghyun Lee, Jinyoung Jang
Many countries have employed various policy measures to reduce industrial CO2 emissions. The cement industry plays a crucial role in emissions reduction because it accounts for a substantial proportion of global emissions. This study analyzes the inter-fuel substitution paths for the cement industry, along with its impacts on emissions reduction. A mixed multiple discrete-continuous extreme value (MDCEV) model is used to accommodate for the heterogeneity of firms’ preferences for fuel mixes. The proposed model is empirically verified using firm-level data collected from 1998 to 2011 for Korean cement production firms. The results show that firms’ marginal utilities from using bituminous coal are still larger than those from other alternative fuels. The determinants of the firms’ alternative fuel choices are different according to the individual fuel types, but the price of bituminous coal has a primary impact, generally speaking. Scenario analysis shows that 10% and 20% increases in bituminous coal prices will lead to roughly 1.30 million and 1.58 million tons of CO2 reduction for the Korean cement industry, respectively. This study analyzes the selection and consumption patterns according to fuel types among cement producers, and also predicts its impacts on emissions reduction. Further, our study also provides policy implications for the government, which plays a crucial role in designing incentives for firms to use alternative fuels more often.
A state-of-the-art review of sustainable energy based freeze proof technology for cold-region tunnels in China Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-07 Jinxing Lai, Xiuling Wang, Junling Qiu, Guozhu Zhang, Jianxun Chen, Yongli Xie, Yanbin Luo
To cope with tunnel frost damage, studies on prevention methods are routinely conducted to improve environmental protection and energy saving. Based on field investigations, the main available thermal insulation methods and their application are discussed and analysed in this paper. The results show that passive measures, such as a thermal insulation layer or door, cannot completely avoid frost damage. Construction investment of the electric heat tracing (EHT) system is lower at the early stage, but a large investment in operation and pollution problems are needed in the later period. As renewable, clean and environmentally friendly primary energy, geothermal energy can realize energy-saving and emission-reduction. Furthermore, our research team proposed the optimization design method for tunnel heat insulation and anti-freezing by using geothermal energy and presented the challenges for future applications of the ground-source heat pump (GSHP) system in tunnels. The results regarding energy conservation from this review can provide useful technical support in design, operation and management of tunnels in cold regions.
Critical review of latent heat storage systems for free cooling in buildings Renew. Sust. Energ. Rev. (IF 8.05) Pub Date : 2017-11-07 Rami Zeinelabdein, Siddig Omer, Guohui Gan
Buildings have a major contribution to the global energy consumption. Heating, ventilating and air conditioning systems (HVAC) are responsible for most of the energy use in buildings. Thus, clean and sustainable alternatives such as free cooling of buildings have recently gained much attention as means to reduce the operation hours and capacity of the conventional cooling and heating systems. The free cooling could be provided by collecting the natural cold energy during night time in appropriate thermal storage form and this could be retrieved when needed. Phase change materials are exploited by a number of investigators as a storage medium in free cooling applications, as these substances possess high energy densities, and absorb and release heat at a narrow temperature range, hence, the comfort temperature can be maintained day and night. The objectives of this article are to provide a comprehensive review on recent development on free cooling technologies incorporating latent heat storage and to shit lights on the most significant parameters affecting the performance of these materials in free cooling strategy. The outcomes of this review would be helpful in providing clear insight information on potential improvements that can be applied to the storage materials. All the reviewed studies demonstrated that the night cooling strategy using PCMs has the capacity to maintain the indoor temperature well within the comfort zone whilst providing a considerable reduction in cooling loads in all considered climates.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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