Experiments on solar thermal collection date back to the eighteenth century, but the specific technology for use in homes and other buildings was developed in the late nineteenth century. The first patent for a solar-powered device to heat water was issued in 1891, and the technology was very popular for several decades, particularly in places with significant year-round sunlight. By the 1920s, tens of thousands of systems had been installed in North America. Like other uses of solar power, however, this variety faced the huge problem of cost efficiency—as the price of coal and gas fell, there was little incentive to install a solar energy system. Like other sources of solar power, this system enjoyed a resurgence in popularity in the 1970s and beyond, and it is widely used today. Indeed, Alberta is home to a unique and innovate project drawing upon solar thermal technology, the Drake Landing Solar Community near Okotoks. Completed in 2007, the fifty-two houses in the community draw upon an integrated solar thermal system that
provides for up to 90% of the community’s space heating needs. Each house is also equipped with solar panels that provide energy for up to 60% of its hot water needs, and is designed and built to prioritize energy efficiency. By combining solar energy and energy efficiency, this award-winning project reduces greenhouse gas emissions by 236 tonnes (260 tons) per year.
Solar collectors can also be used to generate electricity, though in a very different way than photovoltaic technology. Photovoltaic cells use the sunlight to directly produce electricity in semiconductors. Thermal collectors can produce electricity by super-heating water and turning it into steam to drive an engine that generates electricity. To achieve this, solar collectors need to be capable of producing heat up to 600°C (1,112°F) (unlike thermal collectors for hot water use, which need to produce heat up to only 80°C (176°F)), and thus require a system of lenses and/or mirrors to concentrate the solar energy.