Development and evaluation of combustion-type CO2 enrichment system connected to heat pump for greenhouses

The exhaust gas from combustion has been extensively used for greenhouse CO2 fertilization. However, its toxic gases and thermal energy would generally limit the proper applicability. The aim of this study is to develop a technology to supply toxic gas-free CO2 and to recover exhaust gas thermal energy. A combustion-type CO2 generator was manufactured and connected to a heat pump system for greenhouse heating and cooling. Control algorithm for effective operation of the system was also developed and implemented. Greenhouse operation was run at the conditions under which values for CO2 concentration and indoor temperature were maintained at 1200-1300 ppm and 25-27 °C, respectively. Technical performance of the system was evaluated in cold, moderate and hot seasons.