EVALUATION OF ROOF SPRAYING AS A LOW COST SYSTEM FOR SUSTAINABLE ENERGY COLLECTION

In case a greenhouse is heated by means of a heat pump, fossil fuel consumption of greenhouses can be diminished. In nowadays research and development projects around heat pumps in horticulture, the evaporator is fed by a storage system that stores thermal energy in aquifers at depths of some 50 m. However, such a storage system must be charged. Recently, a number of charging methods are studied. At the one side of the options, projects can be mentioned that focus on regenerating the storage system while cooling the greenhouse to such an extent that it can be kept (almost) closed. In those cases the heat collection is at least triple the amount of heat that is needed for charging the storage facility. At the other side of the range of options, as in this paper, research is focussed on collecting only the amount of heat required to compensate for the low temperature heat demand of a suitably sized heat pump. This paper shows that a sprinkling system, as a modification on already existing systems, potentially collects more than 500 MJ per m² per year, which gives the opportunity to save this amount of fossil fuel (about 16 m³ of natural gas per m² per year)