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Advanced adiabatic compressed air energy storage (AA-CAES) has been recognised as a promising approach to boost the integration of renewables in the form of electricity and heat in integrated energy systems. Nevertheless, the uncertainty and variability of renewables spark the consideration of the off-design thermodynamics of AA-CAES, particularly when the heat exchanger is equipped to collect and recycle air-compression heat. Here, the authors propose a general off-design thermodynamic simulation model of AA-CAES incorporating the part-load characteristics of heat exchangers, and validate the effectiveness of the proposed model on a practical AA-CAES demonstration pilot. The results indicate that the simulation model offers an acceptable approximation for the practical operation behaviour of AA-CAES facility and decreases the modelling error from 20.8 to 6.28% compared with the existing model. The proposed simulation model is expected to provide insights into the investigation of the dynamic characteristics of AA-CAES in the future integrated energy system.

The development of renewable is becoming a new trend to cope with the shortage of fossil fuels and environmental pollution, but the inherent uncertainty and volatility pose great challenges to power system operation with high share of renewables. Energy hub which incorporates multiple energy production, conversion, and storage facilities can play a noteworthy role in renewable accommodation and energy saving. This paper proposes a multi-stage robust optimization model for day-ahead scheduling of energy hub composed of wind generation, advanced adiabatic compressed air energy storage (AA-CAES) system, and heat pump in the presence of wind uncertainty. To overcome the computational difficulty, the multistage model is decomposed into two stages. The first stage minimizes the operation cost under the predicted scenario, and the second stage determines real-time dispatch in response to the observed wind power generation. Dynamic lower and upper bound variables for two correlated state-of-charges (SoC) are added as the first-stage decision variables with ramping limit constraints, so that the second-stage decision can be made period-by-period without jeopardizing robust feasibility. This is an important difference compared to the two-stage robust optimization whose second-stage decision is anticipative and thus non-causal. Finally, the day-ahead scheduling problem is reformulated as a mixed-integer linear program (MILP) guaranteeing the robustness and non-anticipativity of real-time dispatch. Case studies verify the effectiveness of the proposed method.

As a fundamental infrastructure of energy supply for future society, energy Internet (EI) can achieve clean energy generation, conversion, storage and consumption in a more economic and safer way. This paper demonstrates the technology principle of advanced adiabatic compressed air energy storage system (AA-CAES), as well as analysis of the technical characteristics of AA-CAES. Furthermore, we propose an overall architectural scheme of a clean energy router (CER) based on AA-CAES. The storage and mutual conversion mechanism of wind and solar power, heating, and other clean energy were designed to provide a key technological solution for the coordination and comprehensive utilization of various clean energies for the EI. Therefore, the design of the CER scheme and its efficiency were analyzed based on a thermodynamic simulation model of AA-CAES. Meanwhile, we explored the energy conversion mechanism of the CER and improved its overall efficiency. The CER based on AA-CAES proposed in this paper can provide a reference for efficient comprehensive energy utilization (CEU) (93.6%) in regions with abundant wind and solar energy sources.

The comprehensive utilization technology of combined cooling, heating and power (CCHP) systems is the leading edge of renewable and sustainable energy research. In this paper, we propose a novel CCHP system based on a hybrid trigenerative compressed air energy storage system (HT-CAES), which can meet various forms of energy demand. A comprehensive thermodynamic model of the HT-CAES has been carried out, and a thermodynamic performance analysis with energy and exergy methods has been done. Furthermore, a sensitivity analysis and assessment capacity for CHP is investigated by the critical parameters effected on the performance of the HT-CAES. The results indicate that round-trip efficiency, electricity storage efficiency, and exergy efficiency can reach 73%, 53.6%, and 50.6%, respectively. Therefore, the system proposed in this paper has high efficiency and flexibility to jointly supply multiple energy to meet demands, so it has broad prospects in regions with abundant solar energy resource.

This paper studies the dynamic operation of a residential electric energy system with distributed renewable generation. Energy streams among the power grid, local renewable plant, storage unit, and demand are considered; the temporal volatility of renewable generation is described by an uncertainty set, and the optimal operation problem gives rise to a multi-stage robust optimization. To deal with the non-anticipativity issue, the robust model is solved via robust dual dynamic programming (RDDP) approach. The the cost-to-go function is approximated by iteratively updating the upper and lower bounds, which can be obtained from forward-pass and backward pass procedures. Case studies validate the performance and advantage of the proposed method.

Liquid air energy storage (LAES) is a promising solution for electricity energy storage and grid load shifting. The storage and application of cold energy can significantly affect the performance of LAES systems. A stable and sufficient source of cold energy in the liquefaction process is the key factor for the stable and efficient operation of an LAES system. Hence, a novel hybrid LAES system combined with organic Rankine cycle (ORC) systems based on the utilization of liquefied natural gas (LNG) cold energy is proposed in this paper. In the charging process, the LNG helps cool the compressed air, and the cold energy of the liquid air and excess compression heat are utilized in a two-stage ORC system to generate additional electricity during the discharging process. A mathematical model comprising energy and exergy analyses was developed to analyze the performance of the proposed system and the influence of key parameters. Compared to standalone LAES systems, the cold energy storage system is extremely simplified in the proposed system, and higher electricity storage efficiency and density are obtained. Therefore, the proposed system has a promising prospect in LNG terminals owing to its stability and ease of implementation.

Compressed air energy storage (CAES) is a large-scale energy storage technology that can overcome the intermittency and volatility of renewable energy sources, such as solar and wind energy. Although abandoned mines can be reused for underground CAES of large scale, their feasibility requires further investigations. This study performs a comparative study on the effects of two construction and plugging schemes on the thermo-mechanical responses of an abandoned drift for the 60-MW CAES project in Datong Yunggang Mine, China. The first scheme uses only the drift as the air container, and the shaft is plugged with concrete. The second scheme uses the drift and shaft. A coupled 3D model is established, and the interaction of the temperature field, displacement field, and air state is fully considered. The numerical model is validated via previous analytical and numerical methods. The simulations indicate that air temperature and air pressure evolve “up-down-down-up” in one CAES cycle. The two schemes have roughly consistent air temperature, and relative huge difference exists for the air pressure. During the charging stage, relatively high tensile stress is induced by the air injection into the caverns. The first scheme shows less stress concentration and lower tensile stress, indicating that the concrete plugging at the intersection between Drift 1080 and North-5 Shaft is effective to reduce the stress concentration. This study can serve as reference for CAES design in similar engineering and studies.

The extremely non-uniform solar flux distribution in the solar power tower plant can badly cause some crucial problems for the solar receiver such as the local hot spot, the thermal stress, and the thermal deformation. Homogenization of the solar flux distribution is an effective method to avoid these problems, and has become an important research topic. The objective of the present study is to homogenize the solar flux distribution on the inner surfaces within the cavity receiver while keeping the optics loss as low as possible by replacing the conventional single-point aiming strategy with optimal multi-point aiming strategies. Multi-objective optimizations of the aiming strategy for the solar power tower with cavity receivers are performed by using the non-dominated sorting genetic algorithm. The distribution of the aiming points on the cavity aperture and the allocation of the aiming points for each heliostat are optimized simultaneously. The following conclusions can be made: (1) The uniformity of the solar flux distribution on the aperture does not always signify the uniformity of the solar flux distribution on the inner surfaces, where the later one is what we are truly concerned about. Therefore, the optimization of the aiming strategy should take charge of the solar flux distribution on the inner surfaces rather than on the aperture. (2) The multi-objective optimization can provide the trade-off between the non-uniformity of the solar flux distribution and the optics loss in the form of Pareto optimal fronts. (3) The optimal aiming strategies provided by the multi-objective optimization can significantly homogenize the solar flux distribution on the inner surfaces within the cavity at a minimum cost of optics loss. (4) For the optimal aiming strategies at all time except the noon, there exists a west-east asymmetry of the aiming point distribution on the aperture. Moreover, the asymmetry gets less obvious as the time gets closer to the noon.

Liquid air energy storage (LAES) is a promising energy storage technology in consuming renewable energy and electricity grid management. In the baseline LAES (B-LAES), the compression heat is only utilized in heating the inlet air of turbines, and a large amount of compression heat is surplus, leading to a low round-trip efficiency (RTE). In this paper, an integrated energy system based on LAES and the Kalina cycle (KC), called KC-LAES, is proposed and analyzed. In the proposed system, the surplus compression heat is utilized to drive a KC system to generate additional electricity in the discharging process. An energetic model is developed to evaluate the performance of the KC and the KC-LAES. In the analysis of the KC subsystem, the calculation results show that the evaporating temperature has less influence on the performance of the KC-LAES system than the B-LAES system, and the optimal working fluid concentration and operating pressure are 85% and 12 MPa, respectively. For the KC-LAES, the calculation results indicate that the introduction of the KC notably improves the compression heat utilization ratio of the LAES, thereby improving the RTE. With a liquefaction pressure value of eight MPa and an expansion pressure value of four MPa, the RTE of the KC-LAES is 57.18%, while that of the B-LAES is 52.16%.

Liquid air energy storage (LAES) is a promising large-scale energy storage technology in improving renewable energy systems and grid load shifting. In baseline LAES (B-LAES), the compression heat harvested in the charging process is stored and utilized in the discharging process to enhance the power generation. Due to the low liquid air yield, a large amount of compression heat is wasted. In order to improve the round-trip efficiency (RTE) and extend the application field, a novel combined cooling, heating and power system based on the LAES (LAES-CCHP) is proposed and investigated. In the proposed system, an organic Rankine cycle (ORC) is employed to recover the high-temperature surplus compression heat to generate electricity and an absorption refrigeration system (ARS) is introduced to utilize the low-temperature compression heat to realize district cooling and heating. Based on a mathematical model, performance evaluation and exergy analysis of the system is performed. It is found that the effective and cascaded utilization of the compression heat could significantly improve the efficiency and performance of the system. With optimal operational parameters, the RTE and exergy efficiency of the LAES-CCHP could reach 69.64% and 57.02%, respectively, which are 37.66% and 12.71% higher than those of the B-LAES.

Factories in China are faced with peak-valley electricity prices and carbon reduction policies nowadays. As the adiabatic compressed air energy storage has a potential to store electricity and provide combined cooling, heating and power, in this paper, a cogeneration system based on it is first proposed to meet the comprehensive energy demands of a latex factory. A new assessment method based on daily energy cost savings is also proposed to evaluate its economic performance. Four novel energy supply strategies based on the cogeneration system and two contrast strategies were analyzed and compared. Results show the energy efficiency of the cogeneration system ranged from 89% to 95%. Besides, energy efficiency and exergy efficiency responded oppositely to the heat-to-electric ratio. In addition, the daily energy costs of the novel strategies were significantly lower than those of the contrast ones. Moreover, the air storage pressure affected the economy the most. Given the ceiling storage pressure of 10 MPa, the optimum floor storage pressure for the air storage was 4.5 MPa. Furthermore, when the cogeneration system provided electricity and dry steam only during the peak load period, its assumed internal return rate reached as high as 10.37%. Therefore, this energy supply strategy is suggested as the most promising choice for the latex factory.

As an effective approach of implementing power load shifting, fostering the accommodation of renewable energy, such as the wind and solar generation, energy storage technique is playing an important role in the smart grid and energy internet. Compressed air energy storage (CAES) is a promising energy storage technology due to its cleanness, high efficiency, low cost, and long service life. This paper surveys state-of-the-art technologies of CAES, and makes endeavors to demonstrate the fundamental principles, classifications and operation modes of CAES. Critical subsystems of CAES are elaborated exhaustively. The application prospects and further research directions are summarized to promote the popularization of CAES in smart grid and energy internet.

Cogeneration is becoming increasingly popular in building and community energy systems with demands on electricity and heat, which is suitable for residential and industrial use in remote areas. This paper considers a stand-alone cogeneration energy hub. The electrical and thermal energies are produced by a combined heat and power (CHP) unit, photovoltaic panels, and a solar thermal collector. Since solar units generate no electricity and heat during the night, energy storage units which shift demands over time can promote the usage of solar energy and reduce the fuel cost of the CHP unit. This paper proposes a method to retrieve the optimal operation cost as an explicit function in the capacity parameters of electric and thermal energy storage units, reflecting the value of energy storage in the cogeneration energy hub. The capacity parameter set is divided into a collection of polyhedrons, on each polyhedron, the optimal value is an affine function in the capacity parameters. Furthermore, the optimal sizes of system components are discussed. The capacity of the CHP unit is determined from a linear program, ensuring supply adequacy, the capacities of solar generation and energy storage units are calculated based on the cost reduction and the budget. Case studies demonstrate the effectiveness of the proposed method.

As a promising solution for large-scale energy storage, liquid air energy storage (LAES) has unique advantages of high energy storage density and no geographical constraint. In baseline LAES, the compression heat is surplus because of the low liquefaction ratio, which significantly influences its round-trip efficiency (RTE). In this paper, hybrid LAES systems based on the cascaded storage and effective utilization of compression heat is proposed and analyzed. In order to improve the storage temperature, cascaded-storage of compression heat is proposed. Meanwhile, the organic Rankine cycle (ORC) and Kalina cycle (KC) are considered to utilize the surplus compression heat to generate additional electricity. Based on the same conditions, the performances of the subcritical ORC using dry fluids, supercritical ORC using wet fluids, and KC are calculated and compared. It is found that the cascaded storage of compression heat can significantly increase the storage temperature and further improve the RTE of the system. Moreover, the RTE of the LAES system is increased by 10.9–19.5% owing to the additional power generation. The subcritical ORC using dry fluids is found to be more suitable in utilizing the surplus compression heat for its simple configuration and excellent performance.

The integration and accommodation of the wind and solar energy pose great challenges on todays power system operation due to the intermittent nature and volatility of the wind and solar resources. High efficient large-scale electrical energy storage is one of the most effective and economical solutions to those problems. After the comprehensive review of the existing storage technologies, this paper proposes an overall design scheme for the Non-supplementary Fired Compressed Air Energy Storage (NFCAES) system, including system design, modeling and efficiency assessment, as well as protection and control. Especially, the design principles of the multistage regenerative, i.e. heat recovery system which is used to fully recycle and utilize the waste heat from compression are provided, so as the overall system efficiency evaluation method. This paper theoretically ascertains the storage decoupling rules in the potential and internal energy of molecular compressed air and reveals the conversion mechanism of gas, heat, power, electricity and other forms of energy. On this basis, a 500-kW physical simulation system of CAES system (TICC-500, Tsinghua-IPCCAS-CEPRI-CAES) is built, which passed a system-wide 420-kW load power generation test with less pollution and zero carbon emissions. Besides, the multi-form energy conversion of multi-stage regenerative CAES and storage efficiency is verified, especially its incomparable superiority in solving the uncertainty problem in wind and solar power generation. Finally, the propaganda and application scenario of the CAES system in China is introduced.

Using multiple energy resources greatly enhances system operating flexibility and efficiency. An energy hub is a vital facility, producing, converting, and storing energy in different forms...

In the view of the complex environment of high altitude areas, a solar chimney power plant experimental setup with a chimney 15 m in height and a collector 15 m in diameter was built. The temperature and velocity of air flow within the collector were tested and analyzed. The results show that the variation of air flow temperature and velocity are similar to the solar radiation. Furthermore, the energy storage layer provides an efficient energy supply for supporting continuous operation at night. The air flow temperatures at different locations inside the collector are different. From the comparison results of air temperature within the collector along each direction, the air temperature in the west side is relatively large and the temperature in the north side is relatively low due to the geographical reason.

International audience; Non-uniform solar flux may lead to negative effects in the receiver of the linear Fresnel reflector (LFR), including the failure of the receiver and the fluctuating operation. For reducing these effects, an aiming strategy optimization approach is presented by combining a multi-objective Genetic Algorithm (GA) and Monte Carlo ray tracing to homogenize the flux distribution in current work. Both the flux non-uniformity index and the optical loss (ηloss) are used as the objective functions. Based on the approach, first, the flux distributions in the Multi-Tube Cavity Receiver (MTCR) and the Single-Tube Receiver with a Secondary Collector (STRSC) are optimized at a typical condition. Optimal results indicate that the GA optimization strategy (S2) can reach a compromise between the flux non-uniformity and the optical loss in both MTCR and STRSC systems. Furthermore, the optimal strategy obtained at a specific transversal incidence angle can be applied in a relatively large range around it. Moreover, parameter study indicates that the aiming line number (naim) has little impact on the efficiencies of the two systems. naim has almost no effect on the flux non-uniformity in the MTCR, but the effect is visible in the STRSC. Finally, the application of S2 under a real-time condition indicates that fluxes in the two receivers can be homogenized efficaciously in the whole time range with a small drop of 0.2–3.8 percentage points in efficiency compared with those of traditional one-line aiming strategy (S1). It is also found that the flux non-uniformity indexes of the MTCR are greatly reduced from 0.77–1.09 to 0.02–0.06 when S1 is replaced by S2, and those of the STRSC are steeply reduced from 0.59–0.70 to 0.29–0.37. It is concluded that the present approach is effective and suitable for homogenizing the fluxes in the receivers of LFRs.

The impedance match is important for the efficiency and available acoustic power of thermocompressor (TCP). The filling pressure, hot end temperature, reservoir volume and opening of orifice were changed to test the optimum load impedance for the maximum acoustic power by RC (Resistor and Capacitor) load method. To make use of the acoustic power efficiently, a pulse tube refrigerator (PTR) was designed based on this impedance to match the TCP and relative coupling experiments were conducted for the first time. The refrigerating performance of PTR was observed and the lowest no-load temperature of 70.4 K was obtained at its optimum working frequency 5.6 Hz. Also, the performance characteristics and total impedances of three different PTRs were compared to verify the rationality of the impedance matching method in this paper. The calculation results agree well with the substantial experiments and further optimization methods were also proposed.

This article describes the application of cryogens in liquid fluid energy storage systems and compares liquid fluid energy storage systems with conventional compressed air energy storage systems. The study focuses on the thermodynamic characteristics of different cryogens used in liquid fluid energy storage systems. It is found that liquid fluid energy storage systems have competitive factors like high energy density and no geographical limitation. A comparative analysis is conducted to present the advantages and disadvantages of different cryogens. The results show that liquid fluid energy storage systems have a promising future in large scale energy storage.