Good, this is.
EnergyTorrent Releases Open-Source Documentation Of Its Solar Concentrators
Renewable energy has just become a closer option for everyone. And it is not about the price but rather about the access to the very technology of using solar energy. In this case, it is about solar concentrators — devices allowing you to obtain high-temperature heat (and with some tinkering, electricity). Now one can produce such devices right in their home workshop using open-source blueprints and documentation from the EnergyTorrent project. All of the documentation, with detailed step-by-step manufacturing instructions, can now be downloaded at the EnergyTorrent Wiki.