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Harnessing free energy

When we think of managing the environment inside our buildings, we typically look to air conditioning and mechanical and natural ventilation strategies. It seems that as our buildings become better insulated, overheating and ventilation becomes a greater issue and we employ more efficient and elaborate methods of tempering our environment.

If you consider an environment where temperature and cost management are of the upmost importance, such as a data centre, cooling and ventilation is an intelligent and refined art. Elaborate building structures, energy recycling schemes, careful rack design and even extreme locations are just some of the numerous steps taken in the quest for the most efficient way to maintain an optimum operating environment. Talk to any data centre owner about this and the magic words “peak load shifting” and “free cooling” are likely to be high up the list of priorities.

In much the same way that elite motorsport technology funnels down to consumer cars, these kind of intelligent strategies are slowly finding their way into our commercial buildings. Beginning with the basic heat recovery concepts of capturing waste heat leaving the building and using it to temper intake air in order to reduce heating bills, the concept of making better use of peak load shifting and free cooling is now readily available for commercial builds in the form of phase-change material (PCM).

The core ideology of using PCMs is simple – adding thermal mass to a building slows down the rate at which the internal temperature can fluctuate. An example of this is to consider the different rate at which a greenhouse would heat up and cool down when compared with a thick-walled concrete structure throughout the day.

The excess energy is stored as latent heat in the solid-liquid phase change of the material, typically at between 18°C and 28°C, and PCMs are able to store between five and 14 times more thermal energy per unit volume than more conventional thermal storage materials.

Not only does this relieve a large amount of strain on the building’s heating and cooling systems, but it also creates a large energy store within the building as a by-product. It is this energy store that innovators are starting to manage and use effectively to not only retain but also to release into systems and areas where it is required.

The beauty of this is that all of the energy is renewable, as it is harvested from both the internal and external environments, and is stored organically as latent heat in the PCM. No electrical battery or wiring is required for the energy storage; it could be transferred via conduction to water or air and used to heat or cool other parts of the building without using energy-expensive mediums found in more conventional heating and cooling technology.

Marry this with an intelligent control system and the result is that in many countries with moderate climates, we could be using night temperatures to cool buildings during the day and day temperatures to warm buildings at night.

James McGowan is the product designer at Monodraught

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