Making Horticulture More Efficient by Recycling Energy Waste from LEDS.

One of the often-cited advantages of LEDs over tungsten filament and fluorescent lights is their high efficiency. A good quality white LED can convert around 40 percent of the electrical energy to light. While this sounds impressive when compared to other light sources it still means 60 percent of the electricity is wasted as heat. Of LEDs that work in the visible spectrum green devices are the least efficient, maxing out at around 20 percent, while UVC LEDs struggle to achieve double figures.

The heat produced by LEDs has to be removed by conduction. Failure to do so gives rise to problems with the quality of light produced and operational lifespan. The conventional solution is to mount the LEDs on a metal PCB and use a suitably large heat sink to dump the heat to the atmosphere.

Greener LEDs, Greener Flora
A new and rapidly increasing opportunity for LED lighting is in horticulture. While we all know that plants need light to grow (with the possible exception of mushrooms), scientists are just beginning to understand how to tune the light spectrum through a plant's lifecycle to alter factors such as growth rate, crop yield, color and even taste. Some scientists have even predicted LED lights used in this manner will trigger a revolution in horticulture. Perversely, one of the few wavelengths plants do not respond strongly to is green, so the poorer efficiency of 560 nm LEDs is not an issue in this application.

Installing banks of LEDs in greenhouses and sheds might seem like a good idea until the electricity bill for the first month arrives. High brightness, tunable spectrum LED lights are expensive to run, particularly when lit 24×7. But light is not the only energy requirement. Many plants grow better when cosseted and in particular when the roots are kept warm. So not only does the plant growing space need to be expensively lit, it needs to be expensively heated as well.

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