More ideas from Fonte Santa
Ground level solar water heater made with irrigation pipe. Water comes out of the underground cistern, into the pipe where it is heated by the sun, and then goes into the house on demand. This is in Hawaii, in colder climates more insulation would be needed.   http://www.thesietch.org/projects/solarthermalpanel3/index.htm

This is a super simple, super effective, budget DIY solar thermal for hot water. It is so effective it can heat water to a temperature that scalds. The system can heat five gallons of water and due to the high temperature of the water, this is more.