Gas Energy Storage System Research Articles

Thermodynamic analysis of novel one-tank liquid gas energy storage system based on ammonia-water mixture fluid

Given the growing focus on energy storage systems, liquid gas energy storage (LGES), which is globally applicable, is being rapidly developed. However, the liquefaction issue of efficiently liquefying the working fluid within LGES remains a significant constraint on its development. In this study, the ammonia-water mixture is used as the working fluid in LGES to address the liquefaction issue, and the number of storage tanks is reduced to one to improve the energy density. Two different one-tank liquid ammonia-water mixture energy storage systems (one-tank LAWES) are proposed and compared. Configuration 1# (C1) features a simple condenser, whereas configuration 2# (C2) incorporates a modified liquefaction process that is similar to some LGES systems. The energy and exergy performances of these two configurations are evaluated and compared. The parametric sensitivity analysis is conducted, and the relationship between the one-tank LGES and Carnot Battery is discussed. The results show that C1 with a simple condenser has better performance, and its roundtrip efficiency and energy density under baseline condition are 48.65 % and 55.03 kWh∙m−3, respectively. Moreover, based on the exergy analysis, thermal energy storage unit 2 is the first priority for improvement in both configurations. The ammonia concentration of the fluid in the storage tank has a slightly positive effect on the roundtrip efficiency of C2, whereas it has a slightly negative effect on the roundtrip efficiency of C1. The one-tank LGES is a Carnot Battery because electricity is stored as thermal exergy rather than mechanical energy.

5E (energy, exergy, energy level, exergoeconomic, and exergetic sustainability) analysis on a carbon dioxide binary mixture based compressed gas energy storage system: A comprehensive research and feasibility validation

Recently, the application of carbon dioxide binary working fluids in compressed carbon dioxide energy storage systems has been proposed to improve the system characteristics, especially for the condensation problem of carbon dioxide. Based on the previous research, a more comprehensive 5E (energy, exergy, energy level, exergoeconomic, and exergetic sustainability) analysis on a typical transcritical compressed carbon dioxide energy storage system using carbon dioxide binary working fluid is carried out. Propane, propylene, R32, R161, R1234ze, and R1234yf are chosen to compose the binary working fluid with carbon dioxide, respectively. The effect of changing parameters, including pump pressure ratio, compressor isentropic efficiency, and heat exahcnger1 outlet temperature on system performance, is also analyzed. In addition, the feasibility of applying carbon dioxide binary working fluid at high ambient temperature is investigated. According to the results, the performance of heat exchanger1, heat exchanger2, and pump decreases while the performance of the turbine is improved with a higher refrigerant mass fraction from the point of energy level. The compressor, pump, and turbine show potential for optimization according to their higher process energy level difference. The pump power and system operating pressure is reduced at the cost of reducing round trip efficiency when using carbon dioxide binary working fluid. A 1% improvement in compressor isentropic efficiency leads to an increase of nearly 0.4% in round trip efficiency, albeit with reduced turbine power. Increasing the heat exchanger1 outlet temperature from 305 K to 315 K results in a 1% increase in round trip efficiency but with a decrease in the performance of heat exchanger1. Both increasing compressor isentropic efficiency and heat exchanger1 outlet temperature benefit the system economy and exergetic sustainability. A noticeable decrease in system performance is observed when the ambient temperature shifts from 293 K to 303 K. However, this deterioration can be mitigated by raising the pressure of saturated working fluid gas at the compressor inlet. Propylene, R32, and R1234yf are suitable candidates to address the condensation issue, considering the system performance at high ambient temperatures. This paper extends research on the compressed carbon dioxide energy storage system based on carbon dioxide mixtures and provides a reference for the working fluid selection and system optimization for related research.

A step towards dynamic: An investigation on a carbon dioxide binary mixtures based compressed gas energy storage system using energy and exergy analysis

A dynamic model of a compressed gas energy storage system is constructed in this paper to discover the system's non-equilibrium nature. Meanwhile, the dynamic characteristics of the CO2 binary mixture (i.e., CO2/propane, CO2/propylene, CO2/R161, CO2/R32, and CO2/DME) based system are first studied through energy and exergy analyses. Performance indicators are considered, including round trip efficiency, exergy efficiency, energy density, discharge time, and average power output. The effects of tank volume and ambient temperature on the system performance are analyzed. According to the results, although the round trip efficiency of the CO2 mixture system is reduced by about 0.68%–11.97% compared to pure CO2, the compressor performance and the system pressure stability are improved. When the tank volume increases from 10,000 m3 to 15,000 m3, the system round trip efficiency increases by 0.16%–0.33%. A further improvement of round trip efficiency for the CO2 mixture is found compared to pure CO2 at higher ambient temperature. This paper demonstrates the dynamic operational characteristics of the compressed gas energy storage system when using different CO2 binary mixtures, providing a reference for optimizing related systems. Potential scenarios and applications for the CO2 binary mixture are discussed for future research.

A new type of bladeless turbine for compressed gas energy storage system.

Nowadays, energy storage engineering is an important means to relieve the problem of energy shortage. In this investigation, we design a kind of vaneless turbine originating from a Tesla turbine with a diameter and an air gap of 250 mm and 0.5 mm, respectively. Importantly, such a vaneless turbine removes the feature of an air outlet in the middle and adopts other ways of entering and leaving on both sides, so as to strengthen the rotor, because there is no need for a large hole in the middle of the rotor. Furthermore, the rotor dynamics characteristics of the vaneless turbine are calculated by six different modes. We also obtain the critical speed in different modes. Moreover, the flow field performances, such as the velocity and pressure of fluid (air), are investigated using the finite element simulation method. In addition, the bench test is built to obtain the output characteristics of a vaneless turbine. The maximum output torque is about 5.56 Nm at 992 rpm, and the maximal rotational speed of the vaneless turbine can reach 3200 rpm. Our work provides new ideas and guidance for the design and research of the new generation of the vaneless turbine.

Thermal parameter optimization design of an energy storage system with CO2 as working fluid

This paper presents a optimization design method on the compression ratio of the compression process and the expansion ratio of the expansion process for the compressed gas energy storage system using carbon dioxide as the working fluid. On this basis, from the thermal parameter perspective of the stage design, compression ratio/expansion ratio design, and compression heat temperature, the thermal characteristics are analyzed using round-trip efficiency and heat storage efficiency as measurement indicators, and a better design scheme for energy-saving and efficiency improvement is obtained. The results show that it will have a positive role in the improvement of the system performance with a three-stage compression-three-stage expansion design structure, an un-equal compression ratio-equal expansion ratio design scheme, and a compression heat temperature of 388.15K. In addition, the round-trip efficiency is up to 74.07% and the heat storage efficiency is up to 51.95%, which has good thermal performance and energy-saving effect for the energy storage system.

Components design and performance analysis of a novel compressed carbon dioxide energy storage system: A pathway towards realizability

To improve the penetration level of renewable energies can give strong support to the development of low-carbon society. Energy storage technologies with excellent performance are benefit to handle the associated problems arise from the fluctuation of renewables. Carbon dioxide is now recognized as a favorite working medium in compressed gas energy storage system. In order to approach the realization of a preferable carbon dioxide based energy storage system, the components design and performance analysis of a novel compressed carbon dioxide energy storage system is proposed in this paper. Firstly, the carbon dioxide compressor and all heat exchangers are designed by considering the real physical properties of carbon dioxide. Then, the system performances under design and off-design conditions are investigated according to the designed heat exchangers, compressor predicted performance maps and the models of other components. Results show that the charge time is 2.02 h, and the discharge time in constant pressure mode and variable pressure mode are 3.64 h and 2.88 h, respectively. The roundtrip efficiency in constant pressure mode is 64.96% with a stable output power, whereas the roundtrip efficiency in variable pressure mode can reach 67.37%. In constant pressure mode, the increased load level results in a raised energy density and a parabolic trend with optimal value at 65.16% in roundtrip efficiency. In variable pressure mode, the turbine inlet temperature has a positive effect on system energy density, whereas the roundtrip efficiency has a parabolic trend.

Integrated grid, coal-fired power generation retirement and GESS planning towards a low-carbon economy

To cope with climate change and achieve sustainable development, power systems need a low-carbon transformation. The use of renewable energy and the retirement of traditional coal-fired power plants (CFPP) are two essential transition pathways for power system de-carbonization. How to gradually retire CFPP or install renewable energy generation while maintaining system security and reliability in the energy transition is an emerging yet important research topic. This paper proposes a power grid augmentation planning model based on low-carbon targets, aiming to plan the retirement of CFPP and the installation of renewable energy. In this model, carbon tax is used as an effective limit on greenhouse gas (GHG) emissions. In order to make renewable energy coupled well with the existing grid, gas energy storage system (GESS) is also considered. GESS is an integrated system that combines Power-to-Gas (P2G) technology with hydrogen turbine (HT), which can store electricity generated by renewable energy and reuse it when appropriate. In this way, the system operating pressure is alleviated effectively, and the overall CO2 emissions can be reduced at the same time. In case studies, this paper attempts to find the optimal emission reduction per unit cost by comparing the ratio of carbon emission reduction to total system cost. Based on the numerical results, the proposed model can provide a useful transformation roadmap for the transition towards low-carbon energy grids.

Integrating gas energy storage system in a peer-to-peer community energy market for enhanced operation

Increased use of distributed generation technologies such as photovoltaics (PVs) has transformed passive consumers into active prosumers. While prosumers can contribute to emissions reduction efforts by using PV energy, the utilization of these technologies can also bring about several problems in the grid such as congestion and voltage variation. These problems could be mitigated if intermittent energy can be consumed where it is produced or alternatively converted to gas using power-to-gas (P2G) technology. In this regard, a peer-to-peer (P2P) energy market with an integrated gas-energy storage system (GESS) is relevant to enhancing the utilization of locally produced energy. This can also minimize grid congestion and other problems due to reduced import (export) from (to) the grid. GESS consists of a P2G unit, gas storage unit and hydrogen fuel cell unit for storing surplus PV energy in gaseous form. Prosumers and GESS purchase surplus PV energy with proposed P2P market mechanism. It is observed that GESS integration increases the community’s economic social welfare and reduces the reliance on the electricity grid.

Justification of CO2 as the working fluid for a compressed gas energy storage system: A thermodynamic and economic study

Abstract The compressed carbon dioxide (CO2) energy storage (CCES) system has been attracting more and more attentions in recent years. The CCES system leads the way of green solutions to accommodating the intermittency of renewable power generation systems in a large-scale energy storage pattern. Particularly, the usage of CO2 as the working medium for CCES successfully offers a green solution to massive carbon capture and storage. This paper aims to further analyze the applicability and feasibility of a novel CCES system with the merit of efficiently and economically utilizing pressure energy and thermal energy. Thermodynamic and cost evaluation on the energy conversion cycle were carried out. Genetic algorithm was employed to perform multi-objective optimization on the novel energy conversion cycle with thermal energy storage towards maximizing exergy efficiency and economic profits. Results reveal that the net output power monotonously increases with turbine inlet temperature, but the unit product cost monotonously decreases with turbine inlet temperature. The multi-objective optimization recommends a 60.5% for the overall exergy efficiency and 0.23 $/kWh for the unit product cost. Moreover, scattered distribution of decision variables suggests always a higher outlet pressure for compressor.

Thermodynamic Analysis of a Novel Compressed Supercritical Carbon Dioxide Energy Storage System

To improve the thermodynamic efficiency of compressed air energy storage system, a novel compressed gas energy storage system using supercritical carbon dioxide was proposed. Energy and exergy analyses were used to study the thermodynamic performance of the novel energy storage system. The thermodynamic analysis results show that the energy storage system based on supercritical CO2 has a better performance and simpler system configurations compared with CAES (Compressed Air Energy Storage, CAES). The exergy efficiency and round trip efficiency of compressed supercritical CO2 energy storage system are 57.02% and 73.02%, respectively. And the highest exergy destruction occurs in the recuperator, accounting 36.51% of the total system exergy destruction, followed by the heater (32.33%) and then turbine, low-pressure reservoir etc.

Integrated power-to-gas and power generation system through chemical looping combustion: a conceptual design

Fossil fuel energy usage will continue to be dominant in the future. Greenhouse emissions will continue to rise unless an alternative way to generate electricity is utilized. Renewable energy sources presents a clean way to produce electricity. However, the intermittency nature of renewable energy sources causes unstable energy production. Energy storage concepts, especially power to gas conversion provides a clean and efficient way to store the overproduced electricity. This paper presents a concept of power to gas energy storage system that is coupled with a chemical looping combustion power generation to provide base load power from the unused electricity in the grid based on a real case of Indonesia. Enhanced process integration is employed in order to achieve an optimal heat and exergy recovery. Preliminary results from simulation using ASPEN Plus V8.8 suggests that a 350 MW power intake for the solid oxide electrolysis system will generate hydrogen that can be utilized for 140 MW power generation with an overall efficiency of 55%. Furthermore, parameters of the system are also evaluated to further improve the system’s total efficiency by changing the key design parameters.

Experimental study of carbon dioxide as working fluid in a closed-loop compressed gas energy storage system

This paper investigates the utilization of carbon dioxide gas available in mass pressurized storage caverns as a working fluid for a modular low pressure compressed gas energy storage (CGES) system. The system is made up of three 7 L cylinders that discharge into an air turbine to convert the system potential energy into kinetic and eventually into electricity through an onboard generator. The operating pressures are kept low (around 3 bar) in order to maintain the adiabatic operational assumption and not necessitate the usage of heat exchangers. The gas is then rerouted back into the storage cavern after expansion. The reported energy conversion efficiency is 46.2% for the three active cylinders operating in tandem and 76.4% for them operating in unison. The main advantage of the proposed system is its flexibility to function under high power density for the latter or high energy density requirements for the former arrangement, respectively. This level of discharge control allows the system to serve in ranges that previously required independent storage systems addressing narrow power/energy density needs. This charge/discharge cycle takes advantage of the availability of the stored and pressurized carbon dioxide, which is denser than air and hence produced higher power output and required 65% less space than its air-operated counterpart.

Thermal analysis of near-isothermal compressed gas energy storage system

Due to the increasing generation capacity of intermittent renewable electricity sources and an electrical grid ill-equipped to handle the mismatch between electricity generation and use, the need for advanced energy storage technologies will continue to grow. Currently, pumped-storage hydroelectricity and compressed air energy storage are used for grid-scale energy storage, and batteries are used at smaller scales. However, prospects for expansion of these technologies suffer from geographic limitations (pumped-storage hydroelectricity and compressed air energy storage), low roundtrip efficiency (compressed air energy storage), and high cost (batteries). Furthermore, pumped-storage hydroelectricity and compressed air energy storage are challenging to scale-down, while batteries are challenging to scale-up. In 2015, a novel compressed gas energy storage prototype system was developed at Oak Ridge National Laboratory. In this paper, a near-isothermal modification to the system is proposed. In common with compressed air energy storage, the novel storage technology described in this paper is based on air compression/expansion. However, several novel features lead to near-isothermal processes, higher efficiency, greater system scalability, and the ability to site a system anywhere. The enabling features are utilization of hydraulic machines for expansion/compression, above-ground pressure vessels as the storage medium, spray cooling/heating, and waste-heat utilization. The base configuration of the novel storage system was introduced in a previous paper. This paper describes the results obtained from a transient, analytical, physics-based thermodynamic system model used for the system design and evaluation of three design configurations (including base configuration). The system model captures real gas effects and all loss mechanisms. The model demonstrates an energy storage roundtrip efficiency of 82% and energy density of 3.59MJ/m3. Experimental evaluation of system performance and detailed cost-analysis will be presented in future publications.