Can sunlight be used to drive a steam engine? How big a collector to provide 1 kw ?

Answer 1

It most certainly can.A Fresnel lens mounted with a solar tracker will do just as you ask. Fresnel lenses designed with Stirling engines and linear generators will be on the market in 2008 on latest estimates. These systems are presently being packaged in the 3 to 5 Kw power range. Try the following link for a home built Fresnel lens with solar tracker design to heat water for various purposes. Be careful this design will produce over 20,000 BTU of usable heat at the focus point. This is equivalent to about 6Kw of electrical heat so be aware.

http://www.ida.net/users/tetons/solar/solarhom.htm

Answer 2

For something like that, I wouldn't use a photovoltaic cell. You want to minimize the energy transformations, especially because solar cells are barely 10% efficient. I would consider an array of mirrors pointng at a pitch black container on a very sunny day. This will probably get the water to boil, you would then have to have that steam travel through a turbine. Generating that small of an amount of power would be less efficient then generating huge amounts of power where you could do it in multiple stages (which helps to recapture some of the energy you'd lose to cooling the steam back to water to boil again).

Answer 3

Steam is a form of water. To heat water to steam directly from sunlight would be difficult for any appreciable amount of water for a practical steam engine. You might try solar cells and an electric heater.

What does your 1 kW refer to? The output of the steam engine? Certainly it depends on the details of your system and not just the efficiency of the solar cells.

Answer 4

Under average conditions you can get about 700 w/m^2 normal to the sun. In practice you'll reduce this by some factor to account for imperfect tracking and collection. If your 1 kW is net output power then you need to factor in the efficiency of your generator too. So maybe a minimum of 6 m^2 to get 1kW in full sun, assuming 80% collection efficiency and 30% thermal efficiency.