Binary cycle power plants – One small part I don’t get

[thenewmans]

I don’t get how a http://www1.eere.energy.gov/geothermal/powerplants.html#binarycycle" keeps the fluid flowing in one direction. My guess is it has something to do (1) with the condenser and (2) with a pump thrown in. The problem with a pump is that it must use up as much energy as the heat puts in.

1 – Why would you have a condenser cool the fluid if you’re just going to heat it up again?
2 – A binary cycle power plant is very much the inverse of an air conditioner. But an air conditioner contains a http://en.wikipedia.org/wiki/Expansion_valve" . The opposite of that is a pump. (There’s no pump in the diagram.)

 

[mgb_phys]

You probably have a pump to send the cold water down and get th ehot water up. You could arrange it so the different densities of the water made it flow naturally but I suspect a pump makes control easier. there is almost certainly a valve for control and safety.

The reason for the condenser is that the turbine doesn't run on hot water - it runs on the pressure created when water turns into steam, you need to condense the steam back into water to use it again. In fact in a real systme the condensor creates a partial vacuum which increases the flow of the steam through the turbine.

The pump uses very little energy, the water is being heated by the ground to very high temperatures for 'free'.