Rutronik News

Heat Management for Horticulture Lighting - Cooling an Artificial Sun

  Knowledge

A home or a farm? It’s a difficult choice, with population growth and climate change causing ever more arable land to disappear. This is why innovative forms of agriculture and modern technologies are needed. Effective heat management is especially needed when using “LED suns”.

Alternative farming capacity is required to be able to produce enough grain, fruit and vegetables regardless of weather conditions and the location. "Urban farming" involves the repurposing of decommissioned underground tunnels or bunkers as well as buildings' roofs and walls. However, the nature of these locations means that they often lack the sunlight required for plant growth, which is why LED lighting systems are increasingly being used as alternative sunlight sources, allowing for the cultivation of plants as needed. Using appropriately controlled light frequencies, it is even possible to optimize plant growth, resulting in larger plants, larger yields, fewer harmful substances - and this method also allows the color and taste of the crops to be adjusted. UV LEDs can also protect plants against micro-organisms, spores and bacteria.

Heat Management for Longer LED Lives

LEDs are much more efficient than conventional halogen bulbs, using up to 50% of the electrical energy to generate visible light, but this means that they also still discharge around half of the energy they consume as heat. As LEDs get ever smaller while requiring more and more energy, so too does the heat output. This affects the life of the LEDs in the long term.

Current LEDs have a life of 2,000 to 4,000 hours. Excessive temperatures mean that they can lose up to a sixth of this, so heat management solutions play a major role in prolonging the performance of LEDs as much as possible. This means that they also significantly reduce the need to replace and maintain them during operation.

Customized Cooling Elements

There is no off-the-shelf solution for heat management, as there are numerous factors to be taken into consideration. Are low-power, mid-power or high-power LEDs being used? What temperatures are to be expected? How much space is available in the application? Is noise output a factor?

Generally speaking, there is a choice of passive and active solutions. Passive solutions include heatsinks and heat-conducting foils from suppliers such as Assmann, Fischer Elektronik or 3M. Active solutions are fans and blowers such as those offered by Adda, Delta and Jamicon.

Design-Friendly Heatsinks

Heatsinks differ primarily in terms of their material. Fin heatsinks made of aluminum are ideal when you need to effectively dissipate a relatively large amount of heat. They are also suitable for cost-sensitive applications due to their attractive purchase price. Suppliers also offer them as customized solutions, adapting their size precisely to the heat dissipation needs.

Plastic heatsinks conduct heat, but are electrical insulators and - depending on the plastic composite - can also offer high levels of light reflection. The plastic can be used directly as a housing, eliminating the need for any additional cooling element. The reflectivity of the plastic means that the light rays do not lose any of their brightness. Plastic heatsinks are - like aluminum heatsinks - design-friendly, but much lighter, making them especially suitable for applications where every gram counts.

One plastic that is especially well-suited to heat conductivity and dissipation is boron nitride, also known as "white graphite". This synthetic material with a graphite-like structure is pure white and an electrical insulator. If the material properties are maintained, boron nitride has a heat dissipation index of up to 15W/m∙K. The cooling fillers of boron nitride are designed to be redirected easily in any direction, making it possible to control which direction heat is dissipated in - vertically or horizontally. Boron nitride is especially well-suited to thin-walled and complex geometric forms - 3M offers heatsinks to match.

Regardless of the cooling method and material used, solutions are practically always custom-developed, as the requirements and local conditions are too specific - this makes professional support all the more important to find the ideal solution for the application at hand.

 

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