Techno-economic analysis and multi-objective optimization of a novel solar-based building energy system; An effort to reach the true meaning of zero-energy buildings

https://doi.org/10.1016/j.enconman.2021.113858Get rights and content

Highlights

  • A novel smart building including photovoltaic thermal cooling panels with two-way interaction with energy grids is proposed.

  • Techno-economic comparison against PV-based systems integrated with battery and heat pump is performed.

  • Multi-objective optimization is applied to the proposed model to minimize the initial cost and bought energy.

  • Photovoltaic thermal cooling panels can produce an annual cooling of 125.6 MWh during the night.

  • The proposed novel model has the lowest payback period and an initial cost of 6.6 years and 457,000 $.

Abstract

In the present work, a novel hybrid solar-based smart building energy system is introduced and studied. The system comprises innovative photovoltaic-thermal-cooling (PVTC) panels integrated with hot and cold storages with two-way interaction with electricity, heat, and cooling networks (if any). The proposed system is compared with PV-based systems integrated with battery and heat pump for a case study complex building in Aarhus, Denmark. The comparison is conducted by evaluating the performance and economic indicators and investigating the effect of significant parameters on each scenario via a parametric study. Furthermore, the optimal operating conditions and sizing of the proposed system are determined using the genetic algorithm method considering initial cost and traded energy with local energy networks as the objective functions. The comparison results show that the proposed solution is the most cost-effective scenario with the lowest initial cost of about 457,000 $ and a payback period of 6.6 years. This is mainly due to the simultaneous interaction with electricity/heat/cooling networks as well as the elimination of the battery and the heat pump, which are offered by the proposed scenario. It is shown that, in comparison to PV panels, the PVTC can produce 328.7 MWh and 125.6 MWh extra heat and cooling annually. The scatter distribution of significant parameters shows that the panel area and heat storage capacity are not sensitive parameters, and keeping the cold storage capacity at the lower bound is a techno-economically better option.

Introduction

Greenhouse gas emissions and global energy consumption are becoming more serious, with 49% and 43% jumping until 2035 compared to 2007 [1]. Although effective actions have been taken for the green transition in Europe, 70.4% of the energy need is still supplied by fossil fuels [2]. Buildings account for a considerable amount of energy consumption and pollution. From the entire buildings’ energy demand in Europe, 63.6% is related to space heating, 14.8% for domestic hot water, and 0.4% for space cooling [3]. Hence, reducing the required energy of buildings can effectively reduce greenhouse gas emissions and contribute to an efficient European energy matrix [4]. A promising solution for this may be a renewable-based smart building energy system with two-way interaction with district energy systems (electricity, heat, and cold). By this approach, the building can genuinely attain a net-zero energy level and contribute to the energy distribution grids effectively. These distributed resources could be used for further peak shaving of the grids, which is a vital need for energy systems [5].

In the literature, various research papers investigate the two-way interaction of the electricity grid with solar electrical building systems comprising PV panels (with and without battery) and heat pumps. Considering the case of Muscat, Oman, a techno-economic comparison of a grid-dependent and -independent PV/battery power system for a residential building was investigated by Al-Saqlawi et al. [6], finding out the superiority of grid-connected system. They showed that a significant portion of the initial and annual operating costs is associated with the battery. Baneshi and Hadinfard [7] compared a PV-based power generation system with and without battery. They showed that the grid-connected system is better than the off-grid one from an economic aspect, and using a battery leads to a 33% higher levelized cost of electricity. Liu et al. [7] studied the feasibility of a PV-based system integrated with a battery and heat pump. They concluded that the electricity price increases dramatically as the size of the panel and the battery price increase. Performance assessment of a PV-based power system integrated with battery for a building apartment located in Australia interacting with the local electricity grid was studied by Syed et al. [8]. They concluded that a renewable-based system supplies the electricity demand of 75% of the total electricity, and two-way interaction with the grid results in a better performance compared to a standalone off-grid system. In another study, for three different climates in Ethiopia, the interaction of a PV/battery system with the electricity grid was investigated and compared by Azerefegan et al. [9]. The aim here was to decrease the pressure on the grid in peak demand hours. Sharma et al. [10] proposed a grid-connected building integrated with PV panels and a battery for Norway, finding out that there is a robust relationship between the PV electricity generation and grid supply to minimize the building’s energy costs. Pinamonti and Baggio [11] used TRNSYS software to compare different configurations of solar-based building energy systems against the conventional air to air heat pump connected to the electricity grid. Their results revealed that the PV-assisted heat pump system is the most profitable solution because of the highest energy reduction and lowest annual costs. In another study, Saleh et al. [12] concluded that the most economical option is integrating PV panels with battery interacted with the electricity grid among various configurations of solar-based building power systems.

In comparison to PVs, the use of PVT panels is more beneficial due to not only a higher useful energy gain (electricity plus heat) from a certain panel area but also a lower energy cost as a result of increasing the share of building in the energy supply of the network, if applicable. Moreover, recovering the waste heat of panels, which leads to a lower average temperature (and thus, a higher electrical efficiency), is another superiority of PVT panels against PVs [13]. The integration of PVT panels with battery and heat storage for providing the heat and electricity of smart buildings has also been studied in the literature. In a recent study, Zarei et al. [14] compared thermodynamic and economic aspects of a novel PVT-based multi-generation system and a PV-based power system for a residential building. They observed 11% higher efficiency as a result of cogeneration of heat and electricity from the PVTs. Techno-economic comparison of PVT panels and a hybrid PV system integrated with a solar thermal collector to provide the electricity and domestic hot water need of an office building in Hong Kong was performed by Tse et al. [15]. They demonstrated the excellence of PVT panels by a lower payback period and higher performance efficiency because of exploiting the waste heat of panels. Kamel et al. [16] concluded that a lower net present value and higher combined cooling, heating, and electricity efficiency are achieved using PVT panels instead of side-by-side PVs and solar collectors for domestic applications. A hybrid building system integrated with PVT panels, thermal, and electricity storage units interacting with the electricity grid was modeled and simulated by Buonomano et al. [17] using TRNSYS software. They concluded that the primary energy saving and CO2 emission reduction of 68.8% and 90.2% is obtained. A PVT-based smart building system was investigated by Behzadi and Arabkoohsar [18], concluding that a considerable reduction in building energy costs is obtained due to the simultaneous production of heat and electricity.

On the other hand, researchers' critical finding is climate change that results in an emerging summer cooling and winter heating demand across the world. It comprises a 30% higher cold demand and 20% lower heat demand by 2050. In this regard, it is also anticipated that in Europe, until 2050, the cooling demand will increase by three times larger than the cooling demand of 2006 and six times larger than in 1990 [19]. Considering these rapidly growing needs, especially in cooling demand, there should be increasing attention to the natural source of cooling. In addition to electricity and heat production of PVT panels in days, their cooling potential via the radiation toward the cold sky at night is left untapped and has been only investigated in a limited number of research works. Analytical and experimental investigation of PVT panels' radiative cooling potential for the Scandinavian climate was studied by Pean et al. [20]. Considering the city of Madrid, Spain, as the case study, Eicker and Dalibard [21] studied the night radiative cooling of a building system integrated with PVT panels, resulting in an average cooling production of 60–65 W/m2. Hosseinzadeh and Taherian [23] studied the radiative cooling potential of flat plate collectors for a residential building. They concluded that the average cooling production of 52 W/m2 is obtained for water temperature decreases of 8 °C.

To sum it up, the literature on the smart energy building topic is still suffering from a couple of important gaps. First, there is a lack of two-way interaction of smart energy buildings with district heating and cooling networks. Second, a significant portion of the investment costs of solar-based building energy systems is associated with batteries and heat pumps, which discourage building owners from having their own unit and contribute to the energy matrix. Third, after so many wide-ranging studies focusing on the electricity and heat production of PVT panels, there is insufficient research on the capability of cold production of PVT panels via cold sky radiative cooling. This work aims to introduce a secure and feasible pathway for developing smart energy buildings by addressing all the gaps mentioned above. For this, it proposes a new configuration of a multi-generation building energy system integrated with PVTC panels and heat/cold storage units having two-way interaction with district heating, cooling, and electricity networks. The proposed system is also not equipped with battery and heat pumps as two primary sources of initial costs. In this way, the buildings’ owners can provide part of their own heating, electricity, and cooling demands and compensate the buildings’ energy costs by selling their excess production to the grids. Furthermore, for getting a better insight into the excellence of the proposed novel configuration, it is compared with two other widespread PV-based building energy systems equipped with battery and heat pump interacting with electricity and heat networks from performance and economic points of view. The comparison is carried out via investigating the effects of main decision parameters and extracting time-dependent diagrams. Finally, multi-objective optimization using the genetic algorithm approach is applied to the proposed novel configuration to obtain the optimal operating conditions of the system.

Section snippets

System description and assumptions

The schematic diagram of each analyzed smart building system is presented in Fig. 1. Fig. 1(a) illustrates the first scenario, the most extensively used system in solar-based buildings. It comprises PV panels and battery and has a two-way interaction with the electricity grid. As shown, based on monitoring the PV production and building’s electricity demand, the surplus electricity can be either stored in the battery or sold to the electricity grid. When the battery is full, and there is no

Methodology

Using MATLAB software with a time resolution of 1 h, thermodynamic modeling of every component of each scenario is performed transiently under the weather data information of Aarhus, Denmark. Furthermore, considering conflictive economic and performance indicators as objectives, multi-objective optimization using genetic algorithm approach is applied to the best scenario.

Results and discussion

MATLAB software is implemented to model and compare the performance and economic aspects of the proposed novel configuration (scenario 3) against other standard PV-based building systems (scenario 1&2). To distinguish the best scenario, first, time-dependent diagrams, daily and monthly, are extracted. Afterward, a comparative parametric study is performed to evaluate the influence of main decision parameters on the economic/performance indicators of each scenario. Finally, considering initial

Conclusion

This work introduces a novel design of a solar-based building energy system comprising PVTC panels integrated with heat and cold storage tanks with two-way interaction with district heating, cooling (if any), and electricity networks. The proposed novel system's technical and economic aspects are evaluated and compared with other conventional solar-based building energy systems consisting of PV panels integrated with battery and heat pump interacting with the electricity grid. Developing MATLAB

CRediT authorship contribution statement

Ahmad Arabkoohsar: Software, Investigation, Writing - review & editing, Supervision. Amirmohammad Behzadi: Visualization, Methodology, Writing - original draft, Writing - review & editing. Ali Sulaiman Alsagri: Resources, Writing - review & editing, Data curation.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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