If you're installing a solar thermal system in a location that gets a lot of direct sunlight and you're doing it on an industrial scale, you might want to consider concentrating collectors. Unlike normal collectors, these won't work with indirect sunlight, but they're a lot more efficient than any of the other types if your location, scale and budget allow their use.  Concentrating collectors use the simple scientific principles of focusing light to concentrate the sun's energy onto a single point. It's like using a magnifying glass to burn holes in paper in summer, but in this case a parabolic surface concentrates the sunlight onto the absorber plate. The result is extreme temperatures... and by extreme, we mean extreme - the hottest temperatures ever recorded on Earth were created at the focal point of a massive concentrating collector!

Unfortunately, concentrating collectors aren't a viable option for residential use. Although they have been used to great effect in large installations around the world – notably to generate steam in solar power stations by CSP (Concentrating Solar Power) – the technology isn't reliable for common, everyday use.

This is because the collectors must track the sun very accurately to generate heat, whether by moving (imaging reflectors) or clever designs that work throughout the sun's daily course without moving (non-imaging reflectors). The technology required to do this is still too expensive and hard to maintain or, when produced at reasonable cost, not tough enough to withstand the rigors of home use.

The good news is that there's a lot of research going on in this area because it's so effective on a grand scale. Given the speed at which modern materials advance and the amount of innovation being directed at the renewable energy field, there will hopefully be some breakthroughs to bring this superb technology to the home market soon.