G.E. van der Heyden, J.K. Neinhuis, A.P. Verhaegh
The main purpose of economic research is to evaluate various competing technologies. A high investment in new technologies will reduce expenditure on energy and the decision to use a specific kind of energy will be determined by the expected future prices.

It was suggested that the prices of oil and gas were determined mainly by political factors, whereas the price of coal was determined by its market value. Thus the maximum price of coal set an upper limit on the prices of other sources of energy. The need to remove pollutants was an additional cost when coal was used. District heating schemes provided an economic supply of heat to growers close to the source.

Thermal screens had been highly developed in northern latitudes where they gave annual energy savings of 40%. Further economic benefits could be obtained by improved methods of control, e.g. higher night and lower day temperatures, and economic optimization. In southern latitudes the absolute energy savings were smaller, but solar energy stored in the soil could increase greenhouse temperatures at night if screens were used, giving increases in production.

Passive use of solar energy was cheap and the technologies were easy for the grower to understand and use. Further research would improve their effectiveness and thus improve their economics. Active solar heating generally required a high electricity input and was unlikely to become economic until the heat requirement of the greenhouse had been reduced by insulation.

The use of low temperature energy supplies (reject heat, etc), offers reductions in unit energy costs. But the heating systems differ from those normally used. It was pointed out that heating has two functions, to heat the greenhouse and to manipulate the plant. The latter required a high temperature heat source. Problems which have to be solved before dual heating systems, using both high and low temperatures, become satisfactory include, integrating the two systems, assessing the size of the base heat load for the low temperature source and the peak heat load using a more expensive form of energy, the transport of heat and the arrangement between supplier and consumer.

It is important for the economists to obtain information on the performance of the techniques being developed. They can then develop economic models to provide realist economic comparisons of the systems available to growers.

van der Heyden, G.E., Neinhuis, J.K. and Verhaegh, A.P. (1989). DISCUSSION ON THE ECONOMIC EVALUATION OF ENERGY REDUCTION/SUBSTITUTION TECHNIQUES. Acta Hortic. 245, 599-599
DOI: 10.17660/ActaHortic.1989.245.83

Acta Horticulturae