Generating Electricity From a Heating Boiler

Powergen, a utility company in the U. K., says it has invented a central heating boiler which generates electricity for households. Powergen is looking for hundreds of customers prepared to buy these personal power stations in a limited launch this winter. When the electricity isn't being used it will be fed back to the grid. The boiler fits under the kitchen counter. It makes a slight humming noise and has an LCD display showing the temperature of the heated water and that its generating 850 watts of electricity. The boiler is based on the Stirling engine, created up by the Scottish inventor Robert Stirling in 1816. There's a gas burner at the top. It heats up four cylinders, each of which contains nitrogen gas and a piston. The gas expands as it warms up, pushing the pistons down. The pistons are cooled on the central heating water, which passes underneath, so they go up again. The resulting rotation is 1,600 times a minute, turning a generator and producing a constant supply of hot water. It's known as an external combustion engine. The technical name for this particular application is "Micro Combined Heat and Power" or "Micro CHP". The drawback is the cost of the boilers and installation, which currently costs between £2,500 ($4,660) and £3,000 ($5,593). Powergen is hoping that the cost will go down if the system becomes popular. :: Powergen via BBC News [by Justin Thomas]

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