Developing a Solar Heating System for a Sweet Colour Pepper Greenhouse

摘要

The objective of the present study was to evaluate the effect of a solar heating system on the microclimatic conditions of a sweet colour pepper greenhouse during the winter season of 2009-2010. The use of the solar energy system for greenhouse heating in winter and cold days helped to save fossil fuels and conserve the green farm environment. It also enhanced the quality of greenhouse products, reduced production costs and limited the release of greenhouse gases. Inside and outside air temperatures, solar radiation flux incident, and relative humidity of inside and outside air for the last five years were collected and used to calculate the total night time heat loss from the greenhouse. Using these data the solar collector area and collector configuration were calculated so that the optimal surface area of was adequate to heat the greenhouse sweet colour pepper crop. The thermal performance analysis was experimentally determined by measuring the temperature increase at various water inlet temperatures and intensity of solar radiation, under clear sky conditions. A complete solar heating system (two solar collectors and storage tank) was utilised for heat- ing 300 litres of water. The daily average overall thermal efficiencies of the solar collector and the storage system during the experimental period were 71.6 % and 91.3 %, respectively. Over a 181-day season the solar heating system collected 3,813 kWh of energy or 70.5 % of the total heat energy used to heat the greenhouse. This percentage could be increased by reducing heat losses from the greenhouse. Due to the microclimatic conditions of the greenhouse being at or near the desired level, the sweet colour pepper had optimal vegetative growth rate, stem length, number of fruits being seated, and fresh yield.