solar water heaters make electricity

As I said before in another post water heating is viable proposition and also for heating air.I placed a mirror on the west side of the house at Gundagai to heat the freezing room in the morning and it worked.It increased the temperature about 5 to 10 degrees ( the thermometer was broken and the scales moved so this is a guess) What would happen if more mirrors were placed and directed to a focal point and all the heat heated water, maybe a boiler to run a steam engine to generate electricity..I could use a 2inch x2inch engine to drive a car alternator to charge batteries and these could pump water. Just dreaming but it would work...What if it were done on a big scale? cheers Stewart