DEVELOPMENT OF TECHNOLOGICAL PROCESS SOLUTIONS IN MODULAR SYSTEM OF SOLAR ELECTRICITY AND HEAT SUPPLY FOR GREENHOUSES

Considering the recent rapid increase of the energy costs for heating commercial greenhouses, solutions for more efficient use of the solar energy are needed. In this study there is investigated application of solar energy for greenhouse heating with a joint equipment, which consists of 8.0 kW solar photovoltaic panels (PV), coupled with a 5.0 kW air-to-water heat pump, 15.0 kW solar collectors (SC), a 10 kWh solar energy accumulator (SEA), and 1600 litre water heat accumulators (WHA). The tests of the joint equipment were made in a 50 m² experimental greenhouse (EG) in several stages: testing of heat accumulation in the water-based heat tanks, testing of the amount of the solar energy, produced by the photovoltaic panels, used for direct water heating and for the operation of the air-to-water heat pump with and without the solar accumulator; and in the periods with insufficient solar energy directly from the grid. Surplus heat from the system was used to heat the irrigation water or to drive the biomass dryer. The temperatures in various points of the heating system were measured and analysed together with average temperatures and the data about the heat and solar energy. The results of the 2022 study showed that in EG, at the average annual solar intensity of 1227.4 kWh·m^-2, 6762.7 kWh of electricity was produced by PV panels, and 12385.2 kWh of heat energy by SC. In the industrial greenhouse (IG), where the total energy consumption during the period, when natural gas was used, was 17.95 m³·m^-2 or 163.73 kWh·m^-2, causing climate change-promoting gas emissions (GHG) of 30.29 kg CO2·m^-2; the experimental greenhouse (EG) emission factor was not detected. We concluded that, without a long–term energy storage system, covering several weeks of heat consumption, the solar energy system should be supplemented with external energy sources to cover the extended periods with insufficient energy supply at the beginning and the end of the vegetation season.