Advanced technologies in cogeneration and polygeneration processes

In the context of Directive on energy end-use efficiency and energy services, cogeneration and advanced technologies on energy conversion take a relevant role in the energy landscape.

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Stirling engine gadgets

Running with the heat of your hand

The American Stirling Company manufacturers Stirling engine gadgets and models for educational and demonstration purposes. Their newest model is the MM-7, powered by the heat from your hand. It needs only a 4 °C temperature differential to run. The FAQ page of their Web site presents a very clear explanation of the working principle of the Stirling engine, as well as comprehensive facts on its history and applications.

Stirling engines hardly qualify as new technology. Robert Stirling received a patent for his first air engine all the way back in 1816. At that time however, the only readily available metal was cast iron, which oxidizes rapidly when left in a very hot flame. So Stirling engines started life with a metallurgical if not technological disadvantage.

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MicroCHP power station with Stirling Engine

In this award-winning LIFE project, results from a long-term test (30,000 hours) of a microCHP unit with Stirling Engine are reported in layman terms. A 3 kWe/15 kWth system is evaluated, serving a 42,000 kWh heat / 8,800 kWh electricity demand in a semi-detached house:

• Compared to a gas condensing boiler, the CHP unit costs 7500 euro more.
• The system runs in heat-driven mode, feeding its electricity into the grid. Annually, 9882 kWh is generated, i.e. more than the home's demand.
• The house continutes to take its electricty demand of 8800 kWh from the grid. I.e. in winter, the house will be a net generator, and in summer, a net consumer.
• The payback on investment is 8 years, mainly through electricity feed-in, tax incentives and a 'CHP Act Bonus'.
• No CO₂ measurement is reported, although the 'potential reductions are 33% to almost 50%'.

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