23 September 2011

PERSPECTIVE ON THE USE OF AIR-SOURCE HEAT PUMPS TO REDUCE CO2 EMISSIONS FROM GREENHOUSES BASED ON LIFE CYCLE ASSESMENT


In protected horticulture, the use of heat pumps in place of combustion heaters, which are widely used in Japan is expected to achieve energy conservation, cost reductions
and CO2 emissions reduction. We estimated the amount of CO2 emissions from energy and so on inputted per plant body in the raising of seedlings and cultivation of tomatoes in
greenhouses. Based on LCA, CO2 emissions can be reduced by 6.31 kilograms per plant body on average in cases where both heat pumps and combustion heaters are used together as heat sources compared with those cases where only combustion heaters are used. This is equivalent to a 38% reduction. In cases where all combustion heaters are replaced by heat pumps, an estimated 65% reduction is to be expected. Moreover, we found that the temperature and high CO2 concentrations in greenhouses were maintained at levels suitable for the growth of tomatoes by closing the roof windows of greenhouses and cooling the greenhouses with heat pumps during the winter daytimes. These results provide multiple usages of heat pumps in greenhouses.