G.L.A.M. Swinkels

Conversion of NIR‐radiation to Electric Power in a Solar Greenhouse

The scope of this investigation is the 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 reflectivity of these materials has 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 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 or TP...

Static linear Fresnel lenses as LCPV system in a greenhouse

A low concentrating PV system with water cooling (LCPVT system) will result in electrical and thermal energy output from the solar energy excess entering a building or greenhouse. All the direct radiation could be converted, which corresponds to 75% of the incoming solar energy. This will significantly reduce the demand of cooling of the building. For an optimal performance it is beneficial to construct asymmetric roof elements with a steep inclination at the north side (the exact angle of course depends on the latitude of the building site). The Fresnel lens structure is oriented in upwards direction. In the current design, two of them are placed between an AR‐coated double glass structure to prevent pollution and condensation on the lenses. Compared with a previous system, the number of lenses is reduced from 3 to 2 lenses, which reduces the costs of the system by limiting the number of receivers. By the upward facing of the lens structure, the focus quality is preserved over a much broader range of ang...

A CPV system with static linear Fresnel lenses in a greenhouse

A new CPV system with a static linear Fresnel lens, silicon PV module suitable for concentrated radiation and an innovative tracking system is integrated in a greenhouse covering. The basic idea of this horticultural application is to develop a greenhouse for pot plants (typical shadow plants) which don’t like high direct radiation. Removing all direct radiation will block up to 77% of the solar energy, which will reduce the necessary cooling capacity. The solar energy focused on the Thermal Photovoltaic (PV/T) module generates electric and thermal energy. The PV/T module is tracked in the focal line and requires cooling due to the high heat load of the concentrated radiation (concentration factor of 50 times). All parts are integrated in a greenhouse with a size of about 36 m 2 . The electrical and thermal yield is determined for Dutch climate circumstances. Some measurements were performed with a PMMA linear Fresnel lens between double glass. Further improvement of the performance of the CPV‐system is possible by using a PDMS lens directly laminated on glass and using AR‐coated glass. This lens is developed with ZEMAX and the results of the Ray‐tracing simulations are presented with the lens structure oriented in an upwards and downwards position. The best performance of the static linear Fresnel lens is achieved with upwards orientation of the lens structures. In practice this is only possible with the Fresnel lens placed between a double glass structure, which will keep the lens clean and free of water.

The Effect of Shadow Lines on a Low Concentrating Photovoltaic System

In order to reduce the energy losses caused by shadow lines, three options are investigated. These are: 1. the use of two types of diodes; 2. the use of an “ideal” diode based an active bypass by using MOS‐FETs [4] and 3. parallel switching of a number of cells between two shadow lines. The first method can reduce the voltage losses of the diode to about 300 mV when oversized Schottky diodes are used. With the second method it is possible to reduce the voltage losses further to about 60 mV for FETs with a resistance of 3 mω. This method has as disadvantage that more electronic components are required to control the FET. With the third method about 10 cells are placed in parallel in one module. In that case only one shadow line appears on each module. Series connection of these parallel modules will result in zero energy losses because no bypass diodes are needed at all. This method has as a disadvantage of very high current output of the module of up to 200A. In a model, the three methods are further ana...

PV System Integrated in a Solar Greenhouse With NIR Selective Coating

The scope of this investigation is the 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). 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.