Filtering Natural Light at the Greenhouse Covering - Better Greenhouse Climate and Higher Production by Filtering Out Nir?

Self Cite

Wageningen UR investigated the potential of several NIR-filtering methods to be applied in horticulture. In this paper the analysis of the optical properties of available NIR-filtering materials is given including a calculation method to quantify the energy reduction under these materials and to estimate the contribution for greenhouse cooling. It can be concluded that the optimum NIR-filtering material is still not found but there is good potential for further developments. NIR-filtering multilayer coatings applied to plastic film or glass filter out NIR most effectively. NIR-filtering is not desirable during winter-time in most climatic regions. Therefore, NIR-filtering coverings should not be used in unheated greenhouses since they cause an undesirable temperature drop. NIR-filtering white washes still reduce PAR too much. NIR-filtering (moveable) screens could be an alternative in the future. Future studies should also investigate whether it is possible to use the reflected NIR energy for other processes or cost-effectively storage.

Section: Resultsmentioning

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Greenhouse Cooling by Nir-Reflection

Hemming¹,

Kempkes²,

Braak³

et al. 2006

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“…Materials reflecting part of the sun's energy not necessary for plant growth (the near-infrared radiation, NIR) show promising results (e.g. Runkle et al, 2002;GarciaAlonso et al, 2006;Hemming et al, 2006c) and may be applied either as greenhouse cover or as screen material. The use of this NIR energy and its conversion into electric power to run a pad and fan cooling system is an example of combined passive and active cooling to be used in the future (Sonneveld et al, 2006).…”

Section: Energy Efficient Coolingmentioning

confidence: 99%

Innovative Technologies for an Efficient Use of Energy

Bakker¹,

Adams²,

Boulard³

et al. 2008

Efficient use of energy in greenhouses has been subject of research and development for decades. The final energy efficiency, e.g. the amount of energy used per unit of product, is determined by improvements in energy conversion, reductions in energy use for environmental control and the efficiency of crop production. The new European targets on reduction of CO 2 emission have resulted in a renewed interest in innovative technologies to improve energy efficiency in greenhouses designed for North-as well as South European regions. In this paper an overview of the recent developments is presented from both the Northwest European as well as the Mediterranean perspective. The developments range from new modified covering materials, innovative and energy conservative climate control equipment and plant response based control systems, to integrated energy efficient greenhouse designs.

“…The designed spectral reflection of this film is given in Figure 3.This film shows a total NIR reflection in the area of 750-2500 nm of 97% combined with a PAR reflection (400-700nm) of only 7%. Implications for the climate conditions in greenhouses with a NIR reflecting film are given by Hemming et al (2005) and Sonneveld et al (2006).…”

Section: Separation Of Visible and Thermal Radiationmentioning

confidence: 99%

Solar Energy Delivering Greenhouse With an Integrated Nir Filter

Sonneveld¹,

Swinkels²,

Holterman³

et al. 2008

The scope of this investigation is the design and development of a new type of greenhouse with an integrated filter for rejecting near infrared radiation (NIR) and a solar energy delivery system. Cooled greenhouses are an important issue to cope with the combination of high global radiation and high outdoor temperatures. As a first measure, the spectral selective cover material, which prevents the entrance of NIR radiation, is investigated. The special spectral selective properties of these materials have to block up to 50% of the solar energy outside the greenhouse, which will reduce the needed cooling capacity. The second measure is the integration of a solar energy system. When the NIR reflecting coating is designed as a parabolic or circular shaped reflector integrated in the greenhouse, the reflected solar energy of a PhotoVoltaic (PV) cell in the focus point delivers electric energy. With a ray tracing computer program the geometry of the reflector was optimally designed with respect to the maximum power level. The PV cells mounted in the focal point require cooling due to the high heat load of the concentrated radiation (concentration factor of 30-40). The properties of different materials, Ge, GaSb, CIS and Si cells were investigated to find the optimal cell for this application. All parts are integrated in a greenhouse structure with a size of about 100m 2 .