Energy savings of 50% in horticulture under glass by application of a new glass foil combination, pilot application in the horticultural plant business, determination of energy savings and beneficial effects on the cultivation of plants
Objectives
An area of 5,000 hectares under glass in Germany and about 90,000 hectares in total in the EU point out the high potential of savings in heating energy in horticulture. The new covering system is to reduce the heat losses by one half.
A new covering system for green houses, which combines a higher transparency with a halved heat transfer, fulfils this requirement. Additionally to the saving of heating energy, the higher and spectrally more favourably distributed daylight corresponds to a better plant development.
Apart from the principal purpose of the BMBF research programme, to mitigate CO2 emissions (part A), the following aspects of the planned project are also to be considered:
- Diffusion of technologies beyond industry borders
The improved coverings for greenhouses are favourably applicable also in the architectural area for all other kinds of transparent cover surfaces.
- Visionary concepts, long-term effects
The respective specific advantages of glass and foil are united to a synergetic component, which deduces thereby new characteristics beyond the sum of the component characteristics. During the typical life time of decades for greenhouses and building facades, we must expect sustainable energy saving.
- Application-orientated projects: implementation in the near future
In a practical application case, the new system will come into operation as a pilot scheme in the beginning of the project period; it will then be further developed and gradually improved with feedback from the experiences during the practical operation.
- Starting support for self runners
The project will have a fast practical start and a systematic scientifically accompanied evaluation phase. The evaluation of the measuring data for heating energy consumption will provide relatively fast for further comparable constructional measures.
Results
A new glazing system was developed by combining the materials glass and foil in a glass-based foil cushion glazing system. This system of high transparent ETFE foil with low-iron, anti-reflective coated solar glass was presented as a prototype from the Research Center Juelich and the companies Centrosolar Glas and Siedenburger Gewächshausbau at the International Plant Fingair (IPM 2005 and 2006). It offers for the first time in horticulture the possibility to increase the transparency of the cover and to simultaneously reduce the heat transfer by up to 50 %. Both materials are highly UVB transmissive, which is favourable for the quality and the hardening of ornamental plants. In addition, the thermal insulation of the glass foil combination is switchable by taking out the air from the cushions and therefore offers the possibility to free the roof area from frost or snow by heating. This is not possible for conventional insulating covers often leading to light loss and thus to a lower production yield.
First results were obtained by a prototype system at the Research Center Juelich. As a first commercial project at Cramer company in Bad Salzuflen, a greenhouse area for the cultivation of ornamental plants of approx. 1,000 m² was completely equipped with the glass foil combination.
According to simulation calculations and first measurements approximately 50% of the heating energy can be saved. To determine the latent energy flow caused by condensation of humidity at the greenhouse cover, hot box equipment is actually prepared for systematic measurements of several roof elements.
It could be proven that the plants developed faster due to the beneficial light conditions. The resulting reduced cultivation time implies significant economic advantages through the improved use of the production area. Additionally, the increased amount of UVB radiation leads to a stronger plant constitution and to a more intensive colour development.
As a first result it can be summarised that at present the technical costs cannot yet be amortized by the energy savings alone, but the additional benefit by the better plant development will lead to a high acceptance of these energy saving measures.
Project partners
Subproject “System test and coordination“
Research Center Jülich
Institute of Chemistry and
Subproject “Industrial development“
Contact
Prof. Dr. Andreas Ulbrich
Institute of Chemistry and Dynamics of the Geosphere
ICG-3: Phytosphere Research Center Jülich
D-52425 Jülich