At the 2000 Olympics in Sydney, more than 8000 photovoltaic panels covering over 6000 square metres will provide 650 kilowatts of electricity to power the Olympic Village. Hot water for the village will also be supplied by solar thermal heating systems. Such systems work by aiming large, black metal solar collectors at the sun. Black and other dark colours absorb more sunlight than light colours. Solar energy makes the collectors very hot, much like the surface of a black road on a bright, sunny day.
Water passing through the collectors is heated naturally and then can be used in the village houses.
Solar thermal heaters typically reduce water heating costs by about 50 percent. Many solar heaters also use natural gas heating as a backup for cloudy days when the sun isn't shining. Put the tip of a thermometer in a container of black dirt inside the greenhouse, then place the house in the sun or under a floodlight. Check the temperature every 15 minutes to see how much hotter it is inside the greenhouse. Open the top or sides of the box and see what effect that has.