Filtering Natural Light by the Greenhouse Covering Using Model Simulations - More Production and Better Plant Quality by Diffuse Light?

Self Cite

In greenhouse horticulture, energy costs form an increasingly larger part of the total production costs. Energy is primarily used for temperature control, reduction of air humidity, increase of light intensity and CO 2 supply. Use of fossil energy can be reduced by limiting the energy demand of the system and decreasing energy losses, by intelligent climate control, by increasing the energy efficiency of the crop and by replacing fossil energy sources by sustainable ones. Energy requirement of the greenhouse can be lowered up to 20-30% by using greenhouse covers with higher insulating values and the use of energy screens. A prerequisite is that these materials should not involve considerable light loss, since this would result in a loss of production. In energy efficient greenhouse concepts, durable energy sources should be included. In (semi-)closed greenhouses, the excess of solar energy in summer is collected and stored in aquifers to be reused in winter to heat the greenhouse. Ventilation windows are closed, with specific benefits to the crop: high CO 2 levels can be maintained, and temperature and humidity can be controlled to the needs of the crop. Development of new greenhouse concepts is ongoing. Current examples are greenhouse systems which convert natural energy sources such as solar energy into high-value energy such as electricity. Given a certain technical infrastructure of the greenhouse, energy consumption can be further reduced by energy efficient climate control and crop management. Essential elements are to allow fluctuating temperatures, lower crop transpiration, allow higher humidities, make efficient use of light and create fluent transitions in set points. Consequences for plant growth are related to rate of development, photosynthesis, assimilate distribution, transpiration and the occurrence of diseases or disorders. Since processes involved are complex, knowledge exchange between researchers and growers is essential to realize the goals set to reduce the energy consumption. INTRODUCTIONIn current greenhouse horticulture, next to high production levels, quality and timeliness of production are important. This can be reached by optimal control of greenhouse climate for which energy is of major importance. The need for (energy) cost reduction has become higher, since with increasing prices of natural gas in the last decade, energy forms a substantial fraction of the total production costs. The liberalisation of the energy market for growers since 2002 has increased the growers' awareness of the energy consumption of their cropping systems. This free market implies that growers do not pay a fixed price per unit of natural gas anymore, but that prices are greatly determined by the maximum supply capacity of the gas contract. Therefore, it is important to reduce peaks in energy use. In view of the Kyoto protocol several governments have set goals for energy use and CO 2 emission. In the Netherlands, the horticultural sector and government have agreed to improve the energy efficiency (p...

Section: Lightmentioning

confidence: 99%

Energy Saving: From Engineering to Crop Management

Dieleman¹,

Hemming²

2011

Self Cite

“…Modern greenhouse coverings are able to transform most of the light entering the greenhouse into diffuse light. A quantitative foundation for the potentials of diffuse light in Dutch greenhouses was given earlier by Hemming et al (2005Hemming et al ( , 2008a. It was shown in modelling and experimental studies that crops such as fruit vegetables with a high plant canopy as well as ornamentals with a small plant canopy can utilize diffuse light better than direct light.…”

Section: Diffuse Lightmentioning

confidence: 99%

Use of Natural and Artificial Light in Horticulture - Interaction of Plant and Technology

Hemming¹

2011

Self Cite

In intensive horticultural cultivation natural light levels often limit crop production during several periods. For an optimum plant production and product quality light intensity, spectrum and photoperiod have to be adapted to the needs of the crops at every moment. Light has to be optimised together with all other growth factors like temperature, humidity and CO 2 . For a sustainable greenhouse production the use of freely available sunlight has to be preferred. New transparent greenhouse covering materials, like ETFE, glass with new anti-reflection coatings or materials with micro-surface structures, transmit a very high amount of light into the greenhouse. Other new materials are able to scatter the incoming light and make it diffuse. Diffuse light penetrates deeper into the canopy, increases light interception by the crop, influences micro-climate and increases crop production by 6.5-9.2% in The Netherlands, the potential in lower latitudes is even higher. Other materials manipulate light spectrum. Photoselective nettings have been developed in different colours influencing morphogenesis and crop production. Fluorescent plastic films combine effects on morphogenesis with high light transmission, especially important for higher latitudes. When sunlight is optimized it can still be necessary to add artificial light to ensure a year-round supply of horticultural products. There is still room for improving the crop energy efficiency under artificial lighting by changing duration and intensity of lighting, different growing systems and plant densities. Since artificial lighting requires a high amount of energy, new artificial lighting systems have been developed, such as interlighting and light emitting diodes (LED). LED give the possibility for true light spectrum control in the future. The (partial) replacement of HPS lamps by LED systems is currently under investigation in Dutch greenhouses. Integration in current growing systems has full attention. In order to reach a high sustainable and economic beneficial production the factor light has to be integrated and optimized within the total horticultural system.

“…Covering materials which diffuse the incoming light, at equal overall transmission and insulation values, improve crop production and energy efficiency (Pollet et al, 2000;Jongschaap et al, 2006;Hemming et al, 2006b). For conditions with high solar radiations, the use of Fresnel lenses is considered to separate the direct from the diffuse radiation and using the surplus of direct radiation into electricity (Souliotis et al, 2006).…”

Section: Maximize and Modify Radiationmentioning

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.