Introducing a novel liquid air cryogenic energy storage system using phase change material, solar parabolic trough collectors, and Kalina power cycle (process integration, pinch, and exergy analyses)

https://doi.org/10.1016/j.enconman.2020.113653Get rights and content

Highlights

  • A novel liquid air cryogenic energy storage system is developed.

  • Integrated Kalina-based combined cooling and power unit and gas turbine power cycle.

  • Phase change material and solar collectors are used to supply heat to the cycle.

  • The round-trip and electrical storage efficiencies were obtained 45.44% & 57.62%.

  • Pinch method, exergy and sensitivity analyses are used to develop the structure.

Abstract

Today, using new energy storage systems for peak shaving and load leveling with the approach of maximizing the efficiency of energy systems is inevitable. In the present study, a cogeneration integrated structure of power and cooling using liquefied natural gas regasification and solar collectors is developed and analyzed. In this regard, the purposes can be achieved by producing liquid air at an off-peak time and storing it as a cryogenic energy storage system and recovering it on-peak time. This new integrated structure generates 11.66 MW power and 4.502 MW cooling at the on-peak time. A Kalina-based combined cooling and power cycle and a gas turbine power generation unit are used to generate power from liquid air. Phase change material is used to store the heat from the compressed air entering the liquefaction stage (at the off-peak time) and recovering it at the on-peak time as the heat source of the Kalina cycle. Also, the solar parabolic trough collector provided with Zahedan climatic conditions the heat required for the direct expansion section. The electrical storage, round-trip, energy storage, and exergy efficiencies of the proposed energy storage system are 57.62%, 45.44%, 79.87%, and 40.17%, respectively. The most exergy destruction belongs to the heat exchangers section, which accounts for 50.85% of the total exergy destruction. One of the important results of the parametric study is the increase of round-trip and electrical storage efficiencies up to 47.59% and 61.60%, respectively, by minimizing the pressure of the inlet air to the liquefaction stage while maximizing the pressure of the liquid air inlet to the power generation stage.

Introduction

In recent years, the use of renewable energies in developed and developing countries is increasing every day to satisfy the demand for clean energy [1]. Because of the low capacity and stochastic nature of these units, with increasing their influence, there might be many problems such as power quality or imbalance between supply and demand in microgrids (MGs) [2]. Energy storage systems (ESSs) are considered as a solution to the challenges that are introduced to the power grids [3]. Also, because of sudden changes in power, ESSs are vital in eliminating fluctuations [4]. Therefore, the main focus in the energy research field is to search and study to find a large-scale, safe, reliable, efficient, and economical energy storage technology [5].

Because of the importance of ESSs, over the last few years, various methods of energy storage have been considered. Flywheel energy storage system (FESS) is one of the energy storage technologies that have long operational life, low environmental impact, high power density, and high round-trip efficiency [6]. A compressed air energy storage (CAES) and various methods to accomplish this process were introduced [7]. In this method, at an off-peak time, electrical energy was used to store air, and then at the on-peak time, the compressed air was applied to generate electricity through a turbine generator. Cryogenic energy storage (CES) is a method of energy storage using low-temperature thermal energy. This recently developed method allows network operators to use excess power for liquefaction of a gas, which is then stored in a tank with thermal insulation. During peak time, liquid gas (cryogen) was used for generating electricity [8]. Different methods of storage, hydrogen production, and economic analysis were examined [9]. The hydrogen storage system is an energy conversion system that converts the chemical energy stored in hydrogen to electricity. A brief overview of hydrogen as an ideal sustainable energy carrier for the future economy was investigated. The problem of achieving optimal planning of the pumped storage hydroelectric plant in combination with several interconnected power systems was studied [10]. Another energy storage system is the battery energy storage system (BESS). An accurate model for batteries with a specific program is required for proper analysis and simulation. Several models of electrical batteries and classified them into six categories were reviewed by Mousavi et al. [11]. Cryogenic energy storage is a promising idea because of its high potential for storing bulk energy with a much higher volumetric energy density than compressed air and pumped hydro energy storage [12]. A exergy-based methods to determine the effective quantity of cold storage on the thermodynamic performance of six liquefaction processes and to determine the most cost-effective process were investigated by Hamdy et al. [13]. The results showed that cold storage merging reduced the specific power consumption by 50–70%. The cost of an adiabatic CES system that is expected to have round-trip efficiency (RTE) of higher than 50% was estimated by Morgan et al. [14]. Three types of CES systems for load leveling, peak-shaving, and cryogenic energy extraction applications were optimized [15]. The results illustrated that in the peak-shaving system, CES was blended with the natural gas combined cycle (NGCC), then while using helium or oxygen as the blending gas, the exergy, and the electrical energy storage efficiencies were obtained 70 and 67%, respectively. The cryogenic energy storage characteristics of a packed bed in which liquid nitrogen as a working fluid was subjected to different pressures were investigated by Chai et al. [16]. The most modern cryogenic-based energy storage and blending it with domestic and external heat sources were discussed [17]. It is concluded that seven different integrated CES systems are designed and simulated in which regasified liquefied natural gas (LNG) resulted in the highest exergetic efficiency of 55.5%. Cold energy of the LNG regasification process is used for producing many valuable products such as extracting liquid oxygen [18].

In recent years, many researchers have studied the extraction of energy from power cycles and low-temperature heat sources, and LNG cold energy as a heat sink. Lee et al. [19] proposed an integrated structure and used the cold LNG exergy and the waste heat from the conventional steam cycle, which resulted in producing more power. The typical steam cycle produced only 42 MW of power, while an analysis of the proposed combined cycle based on the first and second laws of thermodynamic shows that this combined Rankine power cycle produced twice as much power as the normal steam cycle, while consumed the same amount of fossils fuel. A combined power plant system using low-temperature waste heat, cold LNG energy, and ammonia-water mixture Rankine power cycle was proposed [20]. The results showed that the energy and exergy efficiencies were reported 33% and 48%, respectively. The cascade Rankine power cycle to recover LNG cold energy was used [21]. Also, LNG can be used as cold energy in hydrogen production systems along with power generation. The LNG cold energy to produce pure oxygen in the coal gasification system was applied [22]. It is concluded that blending this process improved the system's thermal efficiency by reducing consumed power. An auto-cascade absorption refrigeration cycle that used a low-temperature heat source for pre-cooling LNG production was proposed by He et al. [23]. The energy, exergy, and economic analyses of a water-ammonia cooler combined with the power generation cycle were studied [24]. The waste heat cycles and the LNG cold energy used as the low-temperature heat source and the heat sink, respectively. Among the proposals for the storage of electrical energy, CES and especially liquid air energy storage systems (LAES) have received more attention. Energy stored in the liquid phase in a cryogenic fluid, largely reduced the required tank volume compared to a conventional CAES system [25]. LAES technology has advantages such as: high energy density, no geographical constraints, high storage capacity, low investment costs, long service life, the possibility of recovering wasted heat from industrial plants, and it has no environmental hazards [26]. An air liquefaction cycle with a typical combined cycle power plant was combined [27]. The results showed that when power demand was at the peak, the plant operated in energy recovery mode in which compressed air entered a gas turbine's combustion chamber by a cryogenic pump and the compressor used the liquefied air stored in an insulated tank instead of conventional air, also its round-trip efficiency was higher than 70%. A liquid air storage plant based on the Rankine power cycle with a round-trip efficiency of 43% was studied by Ameel et al. [28]. A LAES system combined with a nuclear power plant was developed by Li et al. [29]. The results demonstrated that recovery and liquefaction using a cold storage system consisting of a pair of thermal liquids (propane and methanol) were associated with relatively high heat capacity. By blending the recovery and liquefaction sections into a turbine configuration, the round-trip efficiency reached over 70%. One of the most efficient methods of storing thermal energy is phase change material (PCM) which allows the use of latent heat to storage thermal energy [30]. Therefore, latent heat thermal energy storage systems (LHTES) are of great importance in various fields such as solar energy, waste heat recovery systems, and green buildings [31]. PCMs are naturally isothermal, therefore, they offer high-density energy storage and the ability to operate in a variable range of temperature conditions. A comprehensive assessment of the application of PCM for the use and storage of solar energy such as water heating systems, solar cookers, and solar dryers was provided [32]. Six different materials as high-temperature PCMs were introduced by Liu et al. [33]. The results of their study showed that the carbonate PCM and chloride PCM as heat storage materials were recommended. The applications of PCM in buildings by some practical solutions were studied and assessed [34]. The exergy analysis of the PCM as a heat energy storage device in a desalination plant was investigated by Asbik et al. [35]. An integrated structure using CAES as the thermal energy storage and a multistage PCM as the thermal energy storage was presented [36]. After calculating the energy and exergy balances, the RTE of the system and the total exergy efficiency of the system reached 70.83% and 80.71%, respectively. Nowadays, the use of solar energy in power generation, refrigeration, and desalination plants has received so much attention. Using solar collectors in integrated structures is one way to generate power and reduce carbon dioxide. A solar collector is a device that absorbs solar radiation and converts it into heat [37], [38]. An integrated system for the simultaneous generation of electricity, refrigeration, and freshwater using solar collectors was proposed [39]. The results showed that the integrated structure had an overall exergy efficiency of 66.05% and an overall thermal efficiency of 80.7%. An integrated system that used flat plate solar collectors, multi-stage desalination, and Kalina cycle to produce freshwater and heat was proposed [40]. It is concluded, the thermal and total exergy efficiencies of the structure obtained 44.64% and 90.40%, respectively. Javidmehr et al. [41] used A integrated structure including CAES, solar collectors, desalination process, and organic Rankine cycle (ORC) to simultaneously produce power, freshwater, and heat were investigated. The results showed that the integrated structure had a thermal efficiency of 65.2% and an exergy efficiency of 41.67%.

So far, several hybrid structures have been developed and assessed to utilize liquid air cryogenic energy storage systems. The main objective of the presented studies is to produce liquid air at an off-peak time and storing it as a cryogenic energy storage system and recovering it on-peak time. A large part of the wasted heat during an off-peak time can be applied in storage systems for consumption at the on-peak time. Also, the energy stored during off-peak can be used as cogeneration of power and cooling during the on-peak time. This research aims to fill the knowledge gap of previous investigations. Based on a review of recent literature, no systematic investigation has been carried out on the development of the use of heat waste of a liquid air storage system at off-peak and its use for cogeneration of power and refrigeration at on-peak time. In this paper, a new integrated system for the generation of power and refrigeration developed using liquid air energy storage systems as cryogenic energy storage and heat energy in PCM for applying at the on-peak time. The developed integrated system through employing LNG regasification and solar parabolic trough collectors according to the climatic conditions of Zahedan in Iran is provided the required energy. Furthermore, after reviewing conducted studies in this field, a detailed discussion about the proposed integrated cycle, its validation, and pinch, exergy, and sensitivity analyses are provided, and the results are assessed and reported.

Section snippets

Description of the integrated cycle

A new integrated structure for the generation of power and refrigeration was developed for use in peak energy consumption. Air liquefies at very low temperatures and under high pressure. The air is compressed in several stages and then liquefied using LNG regasification and propane refrigeration cycle at an off-peak time. The heat dissipated during compression is stored in the phase change material using the output current from the intermediate cooling of the compressors. As a result, energy is

Assumptions and system simulation

The Aspen HYSYS software is used to simulate the proposed integrated structure. Peng-Robinson and PRSV equations of state are used to calculate the thermodynamic properties with high precision. Also, the simulation of PCM and the solar parabolic collector have been done in MATLAB programming. Finally, the cycle is analyzed using obtained data and the assumptions governing the integrated structure:

  • Pressure drop, kinetic, and potential energy are negligible.

  • All systems are in steady-state.

  • Air is

Results and discussion

At the off-peak time, 33.33 kg/s air is compressed to 6670 kPa pressure in several stages using the excess power of the grid. Then, it changes to liquid form by transferring heat to 10.30 kg/s LNG through its regasification. Then most of the produced liquid air (24.59 kg/s) is stored as a cryogenic energy storage system and the rest is used to provide the cooling required for the cycle. The specific power consumption for generating liquid air in this study is calculated by 0.2286 kWh/kg Liquid

Conclusion

In this study, a new integrated system for generation of power and refrigeration with the compression system, liquefaction system, Kalina-based cogeneration unit, gas turbine power generation cycle, phase change material unit, and parabolic trough collectors was developed and exergetically assessed. Wasted heat of the air compression section is stored in the phase change material unit, and this heat is used to supply inlet heat to the ammonia-water combined cooling and power cycle at on-peak

CRediT authorship contribution statement

Armin Ebrahimi: Methodology, Investigation, Writing - original draft, Software, Validation. Bahram Ghorbani: Supervision, Conceptualization, Methodology, Investigation, Software, Validation, Writing - original draft. Fatemeh Skandarzadeh: Methodology, Investigation, Writing - original draft, Software, Validation. Masoud Ziabasharhagh: Methodology, Investigation, Software.

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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