Optimization of a Wood Pellet Boiler System Combined with CO2HPs in a Cold Climate Area in Japan

Abstract

Hot water supply is one of the leading consumers of energy in the building sector in cold climate areas. The use of woody biomass is effective in reducing CO2 emissions in hot-water supply systems. This report deals with a system that combines a wood pellet boiler (PB) and a heat pump system with CO2 (CO2HP) that is used in a facility for disabled people. The following research was conducted. The operation of a hybrid system combining a PB and CO2HPs was investigated. While operating the system, four specific operations were developed as countermeasures to save on costs and reduce system troubles while reducing CO2 emissions. The processes and results are introduced. Numerical simulations were carried out to optimize the operation. The hot water temperature, water volume, and hot water loads were simulated. The influence of the water volume ratio on the cost and primary energy consumption under the requirements for safe system operation was studied. The regional economic ripple effects (REREs) of this system were studied. The wood pellet boiler is not only a measure for reducing primary energy consumption but can also play an important role in a regional economy for sustainable development in countries that import energy resources such as Japan.