Feasibility study for combining cooling and high grade energy production in a solar greenhouse

Throughout the world greenhouse horticulture is expanding and intensifying. The expansion is driven by the much higher production levels that are achieved in greenhouses compared to open fields. This provides increased income for farmers and a positive effect on rural development. Intensification is driven by the demand for better control of the production process resulting in higher yield but, more importantly, higher product quality. As a result products can meet the standards of the fast expanding consumer market for high quality fresh products, driven by the booming new economies.However greenhouse horticulture also faces major problems. In northern countries, with cold winter climates, greenhouses have to be heated for optimal growing conditions so energy supply is an important issue. In the southern countries with the combination of high global radiation and high outdoor temperatures during summer, cooling of greenhouses is needed during this period. Solutions for energy supply in winter and cooling in summer can be combined applying seasonal storage of excess solar energy and exploiting this for heating in winter. The advantage of this system is cheaper cooling, and energy savings of about 35% compared to heating by furnace. The disadvantage is that the excess solar energy is converted to low grade thermal energy which is stored at a temperature level of about 18 °C. This can only be exploited for heating in winter by a heat pump, driven by high grade energy such as electricity. Here, the feasibility of a novel approach is investigated of a greenhouse design combining cooling with energy supply in such a way that excess solar energy is directly converted to high grade electric energy. A prototype greenhouse according to this design is under construction. In a following paper the experimental results of this prototype greenhouse will be presented.