A popular concept is that of using the Sun for power.  Many simple systems can be solar powered, and some can be made from scrap or surplus materials.  Of course, it all depends on when and where you need the energy.

   Solar cell panels (also known as photovoltaic panels) can convert sunlight directly into electrical power.  This can be very handy because electricity can easily be converted into many forms.  Electrical power is arguably the most flexible power source since it can operate virtually any type of device, from radio equipment to water pumps, battery chargers to air conditioning.

   The problem with solar cells is that so far, their efficiency is not very good and they have a limited life span.  Also, if you need power at night, you have to rely on charging batteries from the cells or some other type of storage technology.  Still, the technology is improving.

   There are some applications for solar power that demand raw heat in quantity.  The trick is to collect and concentrate the power so that it reaches useful energy levels.  Sunlight can easily make any metal surface too hot to touch, but it is one thing to feel how hot something can get, and another thing entirely to apply that power in a useful manner.

   Here are three simple solar heat engines that can be used for small, high temperatures applications.  All have been made from surplus materials as an illustration of how simple, cheap, and effective solar power can be.  Just remember that they only work on clear, sunny days.  At the bottom is a new turbine device that can provide electrical power. 

High temperature solar furnace - can boil steel (DANGEROUS)

Cheap variable focus heat source - can cause remote ignition (FIRES)

High temperature research solar furnace - video of lava being made -

Compact Solar Turbogenerator - produces electrical power from sunlight (early)

My solar thermal generator prototype - 14 kilowatts of sunlight from lenses power it

More solar thermal details - seeking investors to make this concept available to you

Solar furnaces and other products you can order - for primary heat, lighting, pyrolysis or power