Analysis of woody biomass utilization for heat, electricity, and CHP in a regional city of Japan

This study analyzes a regional biomass energy system in Japan. Herein, based on local characteristics, such as the heat load and distribution, we compared the woody biomass used for heat, electricity, and combined heat and power (CHP) with or without a district heating system (DHS). In this study, target demands were selected from the actual residential and commercial sectors of Koriyama City in Fukushima Prefecture using two maps of heat density. A heat pipe network between each buildings was designed using Dijkstra's algorithm, and the amount of woody biomass used in each case was fixed such that it satisfied the heat demands of heat-only boilers. Therefore, there were no meshes with unit heat densities >4.2 TJ/ha. However, we found areas with the required heat densities and selected 90 buildings for the DHS. The case that both CHP and DHS were installed and the CHP operational model followed the heat demand (i.e., the “CHP follow” case) was the most effective to reduce CO₂. When individual heat-only boilers were installed in buildings, the CO₂ reduction was substantial; however, the capital costs associated with heat-only boilers were much higher than the those of the other scenarios. When a heat-only boiler and DHS were installed (i.e., the “Heat DHS” case), the CO₂ reduction was competitive with the “CHP follow” scenario, however, total cost was more expensive. Furthermore, the cost of reducing CO₂ would be larger than that of “CHP follow” case even if the CO₂ emissions factor of grid electricity was less than half of its current value.