S. Hemming, H.F. de Zwart, G.L.A.M. Swinkels, H.J.J. Janssen
Two new greenhouse concepts have been developed and evaluated which combine electricity production with plant production, while different principles are used to separate sunlight into a part for plant production and a part for energy production. An important principle in Dutch greenhouse production is: Make maxi-mum use of natural sunlight. It gives free energy and light to crop production. Only in case solar energy provides more light than favourable for crop production, solar energy can be harvested and transformed into heat and/or electricity, crop production remains to be the primary function.
In the first greenhouse concept, energy is produced from sunlight surpluses that are normally reflected by shading screens and therefore not usable for crop pro-duction. This is realised by focussing the direct part of the sunlight by linear Fresnel lenses in the greenhouse roof to a focal line. There the concentrated sunlight is con-verted into electricity and heat by a Concentrated Photo Voltaic (CPV) collector. The collector moves automatically depending on the position of the sun. The diffuse part of the sunlight is used for the crop. Light levels in the greenhouse can be controlled by moving the collector in or out of focus. An advanced prototype of that principle has been investigated the last three years on a 500 m2 scale in Bleiswijk, The Netherlands.
In the second greenhouse concept, sunlight is split into PAR and NIR by a NIR reflecting film placed on transparent lamellae inside the greenhouse. The lamellae are curved to create a focussing mirror. They are turned depending on the position of the sun to focus the direct NIR radiation on a CPV collector placed in the ridge facing downwards. PAR passes the lamellae and provides light for the crop. A prototype of that principle has been realised and tested last year on a 100 m2 scale in Wageningen, The Netherlands.
In both greenhouse concepts the practical working of the systems was evaluated and measurements of thermal and electrical output of the CPV collectors, heat and electricity production and daily light integral in the greenhouse have been carried out.
Hemming, S., de Zwart, H.F., Swinkels, G.L.A.M. and Janssen, H.J.J. (2014). DEVELOPMENT OF ELECTRICITY PRODUCING GREENHOUSES - TWO CASE STUDIES. Acta Hortic. 1037, 129-136
DOI: 10.17660/ActaHortic.2014.1037.12
NIR reflection, Concentrated Photo Voltaics, heat collector, Fresnel lenses, diffuse light, light regulation, tropical pot plants

Acta Horticulturae