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Plug-in HVAC Cogeneration.
by Hakan Falk, "Energy Saving Now", Dec. 2003
Cogeneration is already big in the industrial sector and for larger facilities, it is however scalable and would fit in smaller home level systems. Multi source Cogeneration could be extremely interesting for home level systems and with available technologies it could compete well with the larger generation and distributing systems. If every inefficient burner/boiler system was replaced by Cogeneration units, which maybe even was combined with transportation needs, spectacular energy savings could be achieved. A site who describes this and the results of home made generation with Cogeneration is "Renewable energy and sustainable living" by Steve Spence.
The majority of Cogeneration of today, is concentrated on the use of heat as a byproduct of electricity generation or energy generation (Heat/electricity) as a byproduct of an industrial process. In comparison it is very little on the issue of small scale Cogeneration. The power pack for a hybrid car, have the potential to supply several homes with HVAC and electricity. The fact is that in the right combination of "ready for use" technologies, Cogeneration on "one household" basis, is already economically and a pratically competitive alternative.
In UK the Gas and Electricity distributors, started with a Cogeneration alternative.This aternative is based on heat and a stirling engine, called AC WhisperGen, which provides heat and electricity. Energy source is Natural Gas (NG). Consumption is 1.1 cubicmeter gas per hour and the output is 8 kWatt heating and 1,2 kWatt electricity, which is used for net metering and/or surplus purchased by the electricity company. Service interval of WhisperGen is around 20,000 hours. The unit is too small for a house in colder climates, but would work in Central/South Europe with a very small normal home or medium size well insulated home. A very interesting sleak solution and it will for certain be available in different sizes in the future.
It is several ways to do this Cogeneration, with better sizing flexibility and efficiency. A standard diesel (biodiesel/vegetable oil compatible) genset of 3.5 kW have about the same energy use as WisperGen (10.5 kW) and combined it with AC/Heat pumps, it will then deliver the same or more output than the WisperGen. The service intervals are the same. It is however more flexible and will on average also deliver more electricity to the grid, from not used heat. Scaling is also easy, with standard units of different sizes. To size it to a normal house in Central/South Europe, we would prefer a 6 kW water cooled genset, combine it with DC driven AC/Heat pump with a total consumption of 5 kW (which is 15 kW heat), it will also deliver minimum 1 kW surplus for netmetering and/or purchase by electricity company. The cooling of the genset (about 4 kW) is used for hot water and additional heating. Consumption for such genset is around 1 to 2 liter per hour and compatible with a standard burner/boiler for a larger size of not so well insulated house. The size of the equipment will well cover the needs and give a larger total surplus to the grid. Considering the normally higher prices for NG and most local policies, the cost to run the NG version of WhisperGen and the specified larger diesel, would probably be about the same.
A very interesting suggestion from Dan Maker, a member of the Wastewatts discussion group, was to convert diesel driven cooling/heat pump units for trucks. They have mechanical driven compressor and often a smaller electricity generator for battery charging. A very good idea, that could give a better efficiency on the cooling/heating. Since they are made in larger serie production, it could give price advantages. A very large plus for diesel based solutions, is the opportunity to run it on Biodiesel, Straight Vegetable Oil (SVO) or Waste Vegetable Oil (WVO).
An other example of the principles, but so large that it would service 3 to 4 homes, can be find at,
Polar Power Inc..
The WhisperGen is however a definite sign on that the attitudes to energy use are changing in Europe. More effective equipment, energy saving attitudes and an "active distribution grid", must be very good news for the future.
Hakan Falk
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