Half a croissant, on a plate, with a sign in front of it saying '50c'
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Solar powered triple expansion combined power and heat system

This exists, shirley ?
  [vote for,

Photovoltaics aren't very efficient.

Solar collectors heat water (and can provide space heating) but don't produce electricity.

The idea is simple and obvious but a Web search showed nothing much like it.

A tubular solar collector is mounted in an appropriate location. It is fed with liquid octane (B.P. about 150C) from a feed/expansion tank.

When the panel gets hot, the octane vapourises. The vapour passes through a triple expansion reciprocating piston engine which converts the energy to mechanical rotation which drives a generator.

The exhaust gas passes to a condenser located in a large tank of water. Since the water cannot exceed 100C without boiling, the octane is always condensed. This provides hot water from "waste" heat.

The liquid is pumped back into the feed/expansion tank through a non-return valve. The feed pump is powered either by power tapped off the generator, or (better) directly off the engine's driveshaft.

The working fluid circulation is a closed system.

Octane is widely available and its physical chemistry is well understood.

8th of 7, Jul 08 2010

Energy available from sunlight http://www.google.c...%3DN%26tbs%3Disch:1
How big is your roof? [Twizz, Jul 08 2010]


       Have you considered the scale of any of this?   

       What you are suggesting is a solar powered stirling engine with waste heat going to provide domestic hot water.   

       The link shows how much energy you might expect to get from a square metre of collector.   

       Have a look at your electricity bills, add up the annual total and divide by the energy per square metre figure to tell you how big your collector needs to be.
Twizz, Jul 08 2010


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