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Jon Bennett
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Posted: 19 March 2008 at 9:46am | IP Logged Quote Jon Bennett

Hi Has anyone played with this sort of thing?

Solar Turbine Group

Quote from Article on Popular mechanics website;
"The Solar Turbine Group (STG) is taking an entirely different approach, scaling its equipment way down so that it can be installed in remote locations. Orosz and three partners recently spent a year in the Lesotho mountains working with locals to install a prototype solar turbine at a remote girls’ school.

They kept prices low by using junk auto parts. The ORC’s turbines are made from a salvaged turbo charger, which is coupled to an alternator to create electricity. A radiator serves as the engine’s condenser, cooling the refrigerant before a power-steering pump returns the fluid to the boiler."

Other articles say that they are using an Auto Air Conditioner Compressor as the motor rather than a than a turbocharger.

YouTube Clip shows something that looks more like an AC compressor linked to the alternator at about 35 seconds.

regards
jon

Edited by Jon Bennett on 21 March 2008 at 6:45am



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GWatPE
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Posted: 19 March 2008 at 1:22pm | IP Logged Quote GWatPE

Hi Jon,

I played with this type of system in the late 70's. This is a quite simple process. I bypassed the heat exchanger they mention between the glycol and the refrigerant. I pumped the condensed refrigerant[NH3] to the top of an evaporator. Heat was absorbed directly into the refrigerant to form the vapour. Some superheating was achieved in the design.

The efficiency is determined by the relative temperature difference between the heated vapour and the condensate in degrees Kelvin.

The Example you have given has an approximate maximum efficiency of 30% on a temperature basis. Of course there will be losses in the heat exchangers and the turbine and the generator and plumbing etc. The waste heat recovery to heat water, offsets some of these losses.

The choice of working liquid is important. Best to have high specific heat, to reduce pumping losses. Lubrication of the turbine and condensate pump can be an issue. Hermetic sealed working fluid path is critical if using halogen type refrigerants.

I think that solar panels for water and solar voltaic panels for electricity offer a better small scale option.

Good luck if you still persue a Rankine system.

cheers, Gordon.

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Jon Bennett
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Posted: 21 March 2008 at 6:15am | IP Logged Quote Jon Bennett

Thanks Gordon

At a bit of a loss to a couple parts;
1. When the working liquid is heated it creates high pressure which then has a pressure/heat drop in the motor, further Pressure/heat in secondary energy system (hot water etc). You then have to pump the working fluid back against the pressure created in the heating process, doesn't that chew a lot of energy up?

2. What is the advantage of the further cooling after energy is used, I'm guessing it is to make the working fluid as dense as possible but I can't quite see the upside when you are just going to need to add nmore energy to re-exapand/heat it again.

I gues any pics or drawings of the system that you played with would be out of the question.

regards
jon

Edited by Jon Bennett on 21 March 2008 at 6:34am
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Posted: 21 March 2008 at 8:55am | IP Logged Quote GWatPE

Hi Jon,

you need to understand thermodynamics and how work can be done by a fluid using transitions of state.

1. liquid is heated to form a vapour. This absorbing of energy occurs in the evaporator.

2. The vapour passes through the turbine where energy is extracted as electricity. Work is done by the pressure drop. The vapour then has to be condensed to maintain the pressure drop. This happens in the condenser. The liquid pump completes the cycle by returning the condensate back to the evaporator.

This is pretty much simplified. This is not really in the scope of DIY. I would suggest studying the principles and getting some local expertise from a university if you plan on continuing.

cheers, Gordon.

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