A project to generate solar energy from glasshouses while also allowing crops to grow underneath has failed to prove cost-effective, researchers at Wageningen UR have said.
The Elkas phase 2 project incorporated spectrally selective filters under the roof of a 120 sq m Venlo-type glasshouse. These reflected near-infrared radiation (NIR) back towards a collector at the ridge, while allowing photosynthetically active radiation (PAR) to pass through to the crop below.
Between June and October last year, the format worked successfully, and suggested that electricity production per year would amount to 6-14 kWh/sq m.
But the project report concluded that the concept "is not economically feasible", citing the relatively low efficiency of solar energy harvesting coupled with the amount of PAR which the filters blocked.
"The concept is not expected to be feasible in the (near) future because conventional PV [photo-voltaic energy] is getting cheaper in relation to concentrated PV (CPV)," it added.
"In addition, CPV in greenhouses suffer from shading caused by constructional elements and require an alternative electrical wiring."
The costs and technical demands of the filtering panels and concentrators also proved prohibitive, it said, concluding: "Although the working principle of the Elkas phase II has been proved, the concept has a low prospect for application in Dutch greenhouse horticulture."
Horticulture accounts for around 10 per cent of the Netherlands' entire natural gas consumption - a figure which the government-backed "Kas Als Energiebron" (Greenhouse As Energy Source) programme aims to reduce.