Local sharing of cogeneration energy through individually prioritized controls for increased on-site energy utilization

All over the world, including Japan, there are targets to decrease building energy consumption and increase renewable energy utilization. Combined heat and power (CHP) plants increase energy efficiency and are becoming popular in Japan. CHP plants produce both heat and power simultaneously, but there is not always a need for both. A cluster of several different buildings can increase total efficiency and reduce primary energy (PE) consumption by sharing excess heat and electricity between neighboring buildings. If the generated energy comes from renewable sources, energy sharing makes it easier to reach the net zero energy balance. By adjusting CHP sizes and operation patterns, the wasted heat and primary energy consumption can be minimized. Energy sharing has been explored in situations with identical buildings and centrally administered energy systems before, but not with different building types with separate systems. In this study, a cluster of Japanese office and residential buildings were combined to allow heat and electricity sharing based on cogeneration, using individually prioritized control (IPC) systems. TRNSYS simulation was used to match energy generation with pregenerated demand profiles. Absorption cooling was utilized to increase the benefits of local heat generation. Different CHP operation modes and plant sizes were tested. The benefit of surplus energy sharing depends on the CHP capacities and the fuel type. When using biogas, larger CHP plants provided lower total primary energy consumption, in the most extreme case lowering it by 71%, compared to the conventional case. Using natural gas provided only a 6% decrease. The savings resulting from energy sharing were between 1% and 9% with biogas and between 1% and 6% using natural gas. The least amount of PE was consumed by having large CHP plants with biogas, due to the value of renewable electricity. Using natural gas, thermal tracking had the lowest PE consumption. (C) 2014 Elsevier Ltd. All rights reserved.