I am fascinated by heliostats.<p>Heliostats (sun tracker) can provide natural light indoors. This is useful especially during dark winter months. A more advanced application is to capture the natural light using fibre optics and use natural light in place of artificial lights.<p>The principal advantage here is that the colour spectrum of light changes during the course of a day. This has a significant affect on your sleeping patterns and mental health. It is known for example that in early summer months there is a rise in suicides. This is attributed to people feeling like they have lots of energy from nowhere, but they still are stuck in the winter/spring (natural) depressed state. The rise in energy coupled with low mood produce spur of the moment suicidal behavior.<p>Logically one can use this information to ameliorate mental health problems of anxiety, depression. I foresee a household system that anticipates your mental state accurately, perhaps using a combination of facial recognition coupled with scent analysis, and then deploys some subtle aromatherapy and adapts the natural lighting to something more conducive. This would also be useful for enhancing productivity more generally.<p>Did I mention that natural light is free of charge? :-)<p>There are actually very few heliostat natural light solutions out there, and certainly not for the average person. On the other hand it makes for a great DIY project.<p>Heliostats can also delete your heating bill with simple methods (they make it sound complicated in commercial literature, but it is just pointing a fucking mirror at a tank of water painted black.)<p>There are lots of homemade heliostat systems out there but to my knowledge, no books on how to do it. In my view every home should have a natural light solution, it seems fair somehow. Besides how cool is it that you can point natural light 'up' or in any direction using fibre cable? That will never get old for me and I'm not even an optics geek.