CHP systems... so many possibilities!

A combined heat and power (CHP) system is one where either the byproduct (or waste) of a power system is used to generate heat or vice versa. By using waste products as the source for heat or power, the efficiency of the system as a whole is raised and it presents new revenue possibilities for an existing powerplant or industrial heating system. But is the concept behind CHP systems just limited to large systems, or can it be efficiently used in more common, smaller applications around the home or workplace environments?

In the true sense of CHP, the waste energy of a system is reused to create a more thermally efficient system. I can think of quite a few systems at home that have produce large amounts of waste heat every day, to name a few there are ovens, showers, cars, appliances and air conditioners but I'm sure if you dig into it some more you could find loads of different systems in your home that just sit there wasting energy. Ovens and showers are good examples because we typically actually physically extract the heat as part of their use anyway through ceiling fans and kitchen extractors. Where does this heat go after we extract it... nowhere! Just into the roof and then it's lost to the atmosphere. Now I know the idea of using this energy is not new, there are plenty of places around the world where it is commonplace to use secondary heat sources to keep the house warm. The problem in Australia is that we mostly have the other problem of trying to cool our houses down. But there are still ways we could use this waste heat, by using it to heat our hot water for example or by converting it to electricity, it would even be possible (in a cleverly designed system) to use this waste heat to actually cool the house down!

But I would like to see systems designed to reuse waste energy down to a small appliance level. For example, how could you use the heat from your toaster or light energy from your tv to power/heat/cool your home? Perhaps we could use light and heat sensitive products (paint would be a good one) to capture this energy... I realise that per appliance this would amount to a very small quantity of energy but in a whole house over time I think it would add up. Another idea might be to gather this energy while the appliance is on to power it while it is off, instead of wasting energy from plugged in, unused appliances.

To me this kind of design and thought process embodies the key to green/sustainable engineering, while it is nice to be saving the planet the more interesting part is about making our existing, wasteful systems more efficient and hence do more with less energy.