Capacity design of a distributed energy system based on integrated optimization and operation strategy of exergy loss reduction

Highlights: • Exergy loss rate is reduced in the off-design operation of components. • Hourly energy generation, storage, and supply are optimized by objective function. • Capacity of distributed energy system is designed by integrated optimization method. • Good energy efficiency, cost saving, and emission reduction are achieved. With the increase in the energy demands for heating, cooling, and electricity for buildings, the distributed energy system (DES), which is driven by renewable energy and natural gas, has become an economic and environmentally beneficial option for energy generation and supply. This paper presents a method for the integrated optimization of component capacity and annual operation of DES. In the outer cycle optimization, the capacity of energy generators and energy storages is optimized together to match the fluctuating energy demands of the whole year. In the inner cycle optimization, the hourly operation of energy generators and energy storage is managed following the operation strategy that reduces the exergy loss rate. Case studies of DES design under different grid connection modes for an office building demonstrate the feasibility and flexibility of the proposed method. A traditional centralized system is employed as a baseline of performance, and two other capacity design methods are utilized for comparison. Results show that DES designed by the proposed method reduces carbon emissions by 0.170 kg/kWh, energy consumption by 0.392 kWh/kWh, and operation costs by 0.123 CNY/kWh, on average. In contrast to DESs designed by other methods, the performance of these parameters is improved by 0.019 kg/kWh, 0.078 kWh/kWh, and 0.031 CNY/kWh, respectively. Moreover, the DES design exhibits advantages in exergy saving, uncertainty resistance, and power grid independence.