Thread: interesting non water steam power.

You could use mercury, but it would not be all that healthy if there was a leak.
Refrigerant cycles are done with non-water fluids, so it can be done. Typically a fluid must vapourise/ condense at a useful temperature (typically above any reasonable ambient)/ pressure, be cheap and easy to replace if some is lost (leaks etc) and preferably be 'safe'. For example, ammonia refrigeration plants are not used so much any more because ammonia leaks can be nasty things.
From memory Mercury boils at 200+ degrees and is expensive and toxic, so not the best thing to use.

Michael

There are solar power systems that use mirrors to heat up various salts to a molten state which then turns a turbine to generate power. Apparently the advantage is they can continue generating for several hours after sunset.

Originally Posted by petersemple

There are solar power systems that use mirrors to heat up various salts to a molten state which then turns a turbine to generate power. Apparently the advantage is they can continue generating for several hours after sunset.

Yeah they can store the hot salt in a big tank just like hot water but without having to pressurize anything. But I thought there is still a water steam loop between the salt and the turbine?

Originally Posted by petersemple

Apparently the advantage is they can continue generating for several hours after sunset.

But then maybe it takes a few hours to get it started in the morning.

There are plenty of power plants that use fluids other than water to drive turbines.

Usually they will have a gas turbine as the first stage then the heat recovered from this is used to heat something other than water to drive turbines.

Also geothermal power plants sometimes use a fluid other than water in a secondary system which is heated by water in a primary that is heated by the hot rocks.

The advantage with water is the great increase in volume between liquid and gas (steam) states - in the order of 12x? - most other liquid/gas conversions have a smaller change in volume.

The liquid salt heat battery that the CSIRO is working on is used in conjunction with an ingenious solar concentrator made from stainless steel rings, and is used to power a Sterling heat cycle engine which in turn runs a generator. Sterling cycle engines are considered less 'efficient' than steam engines but they can be run on any heat source - even fermenting grass clippings - don't have to be pressurised or use exotic materials (they do work better filled with compressed nitrogen, its just not necessary). The heat battery means that the unit can run all night & does not have to wait to heat up in the morning.

thanks guys.

the increase in volume is very handy then. the liquid salt heat battery is like a heat reservoir?
not a new idea. I hope it has more success that the Howard's quicksilver engine.