Operation optimization and improvement analysis of multi-energy system

Abstract

With the ongoing economic development, the energy demands increase constantly in China. However, the environmental pollution and energy consumption conflict with each other. The traditional combined cooling heating and power (CCHP) system combined with renewable energy is becoming a key point of pelples′s discussion in recent years because of its clean, efficient, reproducible and other prominent advantages. In this paper, an operation optimization model for the energy system coupled of the photovoltaic system, the distributed energy system, energy storage system and the heat pump system is introduced. The cool-storage technology is applied in this construction object. Therefore, the cooling energy can be supplied through cool-storage equipment in the cold load peak time. Firstly, a regional multi-energy system is introduced and the running characteristics of the multi-energy system were analyzed considering the power consumption of main equipment and the optimal operation cost which was objective function. This main generator unit includes two ICE which the generating capacity is 625 kW. The part-load characteristic of ICE, heat recovery boiler, the receiver refrigerator are demonstrated for the multi-energy operation model. Secondly, an intelligent optimization algorithm (firefly algorithm) is introduced to solve the operation parameters based on the multi-energy model, and the system operation parameters were obtained according to different typical daily load demand. The simulation program is compiled in Matlab, and the population size of firefly algorithm is 50, maximum number of iterations is 200 and the number of convergence is about 120. Moreover, the operating cost and the equipment contribution in typical days are showed in the results to analysis the running characteristics of multi-energy system. In the last, a case study is introduced to demonstrate the feasibility of the firefly algorithm and the aim of the economic analysis is to verify the effectiveness of improvement measures. The main power source includes power grid and ICE generator. The main cooling source includes screw type refrigerator, absorption refrigerator and cool-storage. The heating source includes ground source heat pump which runs all days on account of its less operating cost, gas-fired boiler and heat recovery boiler. The annual operation cost is about 11.77 millon yuan when the capacity of ICE is 2000 kW, and is reduced 6.1% compared with original design. A ratio of electricity buy-back price to electricity price is introduced to increase the economic of the multi-energy. therefore, there are some benefits of sell electricity to back power grid. Moreover, The annual operation cost is about 11.12 millon yuan when the capacity of ICE is 2500 kW and the ratio of electricity buy-back price to electricity price is 0.8, and is reduced 11.3% compared with original design. The static payback period is about 4.43 years. In summary, the improvement analysis to further reduce the system operation cost was completed according to change the original design scheme. The results show that the optimization algorithm based on the firefly algorithm could more accurate solve multi-energy system running status parameters optimization, the typical day energy cost could be significantly reduced by increasing the capacity of the gas internal combustion engine units and the reasonable feed-in tariff policy could further reduce the operation cost.