Techno-economic analysis of hybrid adiabatic compressed-air and biomass gasification energy storage systems for power generation through modelling and simulation

Diyoke, Chidiebere

Abstract

Energy storage has gained an increasing attention as a technology to smoothen out the variations associated with renewable energy power sources and adapt them into a dispatchable product to meet variable demand loads. An energy storage system can be a hybrid or stand alone. There is a rising interest for hybrid energy storage systems cited close to local consumers which is able to exploit the amount of local renewable sources on site, to provide demand side flexibility and also help to decarbonize the heating sector. The thesis is based on modelling and simulation of overall thermodynamic performance and economic analysis of an integrated hybrid energy storage system consisting of adiabatic compressed air energy storage (A-CAES), biomass gasification system with a wood dryer coupled to a syngas-diesel fuelled electric generator for the dual production of electricity and low temperature hot water for domestic use. The first part of the research work involves the modelling of the latent heat (LH) thermal energy storage (TES) for the A-CAES component. Implicit finite difference technique was applied to discretize the energy equations of the heat transfer fluid and phase change material and the resulting equations solved using a developed Matlab computer code. The developed model of the LH TES was validated using experiment measurement from literature and its performance assessed using charging rate, energy efficiency and exergy efficiency. The second part consists of modelling of biomass gasification through a developed Matlab computer code. Kinetic free stoichiometric equilibrium modelling approach was adopted. The developed model showed good agreement with two different experimental measurements. Predictions that can be done with the model include syngas yield, temperature profiles of the pyrolysis, oxidation and reduction zones respectively including syngas yield, carbon conversion efficiency and lower calorific value of the syngas. In the third part, thermodynamic modelling of the overall novel integrated system is developed. It combines the models of different components of the integrated system earlier developed. The system designed for a maximum capacity of 1.3 MW is to utilize the high syngas temperature from the biomass gasifier and the relatively hot dual fuel engine (DFE) exhaust temperature to heat up the compressed air from the A-CAES component during the charging and discharging modes, respectively. Also, the heat contained in the DFE jacket water is recovered to produce low temperature hot water for domestic hot water use. Key output parameters to assess the performance of the hybrid systems are total system efficiency (TSE), round trip efficiency (RTE) of the A-CAES, electrical efficiency, effective electrical efficiency, and exergy efficiency for the system. Furthermore, exergy destruction modelling is done to ascertain and quantify the main sources of exergy destruction in the systems components. Finally, an economic feasibility of the overall system is presented using the electricity and heat demand data of Hull Humber region as a case study. The results of this study reveals that it is technically possible to deploy the proposed system in a distributed generation to generate dispatchable wind power and hot water for domestic use. The total energy and exergy efficiency of the system is about 37.12% and 28.54%, respectively. The electrical and effective electrical efficiency are 29.3 and 32.7 %, respectively. In addition, the round trip efficiency of the A-CAES component of the system is found to be about 88.6% which is higher than that of a standalone A-CAES system, thus demonstrating the advantage of the system to recover more stored wind electricity than in conventional A-CAES system. However, the TSE of the system is less than that of a conventional A-CAES system but comparable to similar hybrid configurations. The exergy destruction of the hybrid system components is highest in the biomass gasifier followed by the DFE and the least exergy destruction occurs in the HAD. Furthermore, economic analysis results show that the system is not profitable for commercial power generation unless a 70% of the total investment cost is waived in the form of subsidy. Expectedly, the cost of electricity (COE) of £0.19 per kWh is more than the range of the mean electricity tariff for a medium user home in the UK including taxes which is £0.15 per kWh. With a subsidy of 70%, the system becomes profitable with a positive NPV value of £137,387.2 and COE of £0.10 per kWh at the baseline real discount rate of 10%. The main contribution of the thesis is that it provides an intergraded realistic tool that can simulate the future performance (thermodynamic and economic) of a hybrid energy storage system, which can aid a potential investor to make informed decision on the profitability and financial outlays for the investment

Citation

Diyoke, C. (2018). Techno-economic analysis of hybrid adiabatic compressed-air and biomass gasification energy storage systems for power generation through modelling and simulation. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4500256

• Thesis Type: Thesis
• Deposit Date: Jan 4, 2024
• Publicly Available Date: Jan 4, 2024
• Keywords: Engineering; Energy storage; Renewable energy; Gasifier; Net present value; Cost of electricity; Hybrid power system
• Public URL: https://hull-repository.worktribe.com/output/4500256
• Additional Information: Department of Engineering; University of Hull
• Award Date: Sep 1, 2018