Using solar and wind to produce power from steam as needed?

Question

How practical would it be to store near boiling hot water - kept hot from solar and wind - and use small amounts of grid electricity to produce steam from this on demand .

This steam could drive a steam turbine to produce green power for the grid- and supply power at high demand periods - at a profit!

This would simplify linking multiple wind turbines and solar panels- and the hot water could still be utilised for showers and hydrothermal home heating.

Answer 1

You have a good idea.  But it works a little different.

Solar thermal power plants use the sun to boil water and drive steam turbines  and generate electricity.  They can then store energy as hot water or hot oil or molten salt, to make steam after the sun goes down, thereby being able to make electricity at night or on cloudy days.

http://www.sciam.com/article.cfm?id=a-so...    

Scientific America article about a proposal to convert the U.S. electric grid to 65% solar by 2050 and nearly all solar by the end of the century.

At a cost in public money that is a small fraction of what we now give oil companies in the way of subsidies and tax credits.  

Green Wombat has several articles about progress already being made in California with solar thermal power plants.

The articles are easy to find, just scroll down.

http://blogs.business2.com/greenwombat/

Here's what one of the companies says:

"Solar thermal power plants such as Ausra's generate electricity by driving steam turbines with sunshine. Ausra's solar concentrators boil water with focused sunlight, and produce electricity at prices directly competitive with gas- and coal-fired electric power."

"Solar is one the most land-efficient sources of clean power we have, using a fraction of the area needed by hydro or wind projects of comparable output. All of America's needs for electric power – the entire US grid, night and day – can be generated with Ausra's current technology using a square parcel of land 92 miles on a side. For comparison, this is less than 1% of America's deserts, less land than currently in use in the U.S. for coal mines."

They say 1% of the Sahara Desert could power the whole world.

Answer 2

Stone would make a much more efficient means of storing the heat energy and some solar plants do this already. During hours of darkness they vent heat from that storage area to keep the turbine turning and cranking out power. Heat dissipates quickly from water but slowly from stone or earth. If you needed hot water you could vent some of the heat to a water storage tank instead. The utility companies may not pay you enough to make this profitable but it would be useful if you wanted to live 'off the grid' and I'm sure some people already do this.

With a wind turbine you'd need to convert that energy back into heat to store it this way which isn't efficient. There is a new type of solar energy plant going up in Nevada, see the link below. If they start selling a home kit for this I'm in. It uses mirrors to heat a liquid in a pipe which turns the turbine to produce electricity. No exotic materials needed and the mirrors don't require the same level of care as solar panels.

Answer 3

Wind turbines generate electricity directly, in the turbine body, and this is then fed into the grid.  Large scale solar plants either do this using photovoltaic cells, or they operate by powering a turbine with steam.

In this latter case the plant used parabolic trough reflectors to concentrate sunlight onto tubes that are carrying a synthetic oil.  This super-heats to over 400 degrees celsius.  This heat is then transferred to a tank in which special salts absorb the heat.  These are called phase change salts.  They melt when the heat is put in, then release the heat when needed and turn solid again.

In this way the power plant can keep producing steam for the turbine(s) throughout the night hours as well as when the sun is shining.

Answer 4

great idea!

Answer 5

Collecting solar energy and producing steam to drive turbine generators is a good idea. There have been many experimental plants doing this over the years. There have also been many experiments done on the best medium to use for storing the heat during the night. My understanding is that the most favorable system at this point in time is using a large array of parabolic mirrors focused on a collector which has a salt slurry or other solution which circulates to a boiler to produce the steam. I followed one test plant in the 70's, and it worked, but finding a good heat absorbing medium that would not corrode the pipes and boiler was the biggest problem. Maybe they have resolved that now. I also understand there are some large scale plants now in service and more planned.

Wind turbines are another matter. They are passive in that they (the wind generator) just turns when the wind blows over about 8MPH and produce electricity directly.

Both are great sources of power, but also both depend on nature and weather cycles. Sometimes the wind doesn't blow and the sun doesn't shine. Many areas of the world are not well suited for these forms of power, and there is a limit to how far you can transport power over wires, so other more reliable sources will also be required for the 24/7 reliability we require.