It is simple physics: All energy loss is ultimately dissipated as heat to the ambient. Reducing or re-using that hot air is key to designing efficient energy-using products. In the figurative sense, 'hot air' in the form of exaggerated safety factors and age-old oversizing-habits may possibly offer an even bigger potential. With our engineering background, VHK has ample experience in dealing with both.

Re-using dissipating heat

What do condensing boilers, heat recovery ventilation units and compressor cooling liquid for space heating have in common? They can all save massive amounts of energy by re-using the heat from the main process, energy that was previously lost as 'hot air'. In a condensing boiler, a secondary heat exchanger cools down the hot flue gases to temperature levels near the dew-point, thus releasing significant quantities of latent heat that reduce the heating bill by at least 10%.

In heat recovery ventilation units there is a heat exchanger between in the incoming cold fresh air and the outgoing warm and the hot stale air. That heat exchanger can save over 80% on the ventilation heat loss of a dwelling or building.

In a lubricated compressor, the physical process generates unavoidably large quantities of heat in the compressed air which is currently cooled down by an oil circuit. The heat from that circuit can either be dissipated as hot air in a liquid-to-air heat exchanger or can be used for low-temperature heating.

 

 

Reduction at the source

While re-using 'hot air' is important, reducing 'hot air' at the source is better. Most R&D engineers are well versed in optimising the primary process and know about electrical, thermodynamic and fluid dynamic losses of motors, fans, pumps, etc.. Yet, especially optimising conditions preceding or following the core process can bring extra savings when using the latest design tools. There are control solutions that allow clients to pick heaters and motors that are more powerful than the highest peak load they can ever expect in practice, but at the same time have the ability to tune down -at still good energy efficiency- to the load levels they can expect in real-life.

Another issue is that of exaggerated safety factors and outdated standards that lead to massive oversizing. Especially a legal instrument like Ecodesign can tackle such issues and overcome legacy practices. And there are technical solutions, too. Modulating boilers, variable speed drives, brushless DC and Switched Reluctance motors allow products to deal with the highest peak loads and at the same time address low-load operation. These developments started at the smaller heater and motor types, but are now also spreading to bigger heaters and motors, amongst others due to lateral influence from the automotive sector developing electric cars with new motor types up to 75 kW or more.

Track record

VHK has been dealing, as policy consultants and as engineers, with technical energy efficiency issues for 30 years and for a very wide range of products. Products for which we have investigated design options range from domestic appliances to industrial components and from HVAC-products to light sources. Our strength is in empathy with the R&D departments in industry and a deep interest and understanding in the challenges they face. From there on we can advise a mainly non-technical audience of policy makers of what is possible and at what pace. We do not pretend that we can do a better job than lifelong engineers and designers in those R&D departments, but we can help them, their industries and eventually society in showing policy makers appropriate ways to mobilise current and latent innovative thinking into successful products.

 

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