Solar Hot Water
How it works:
The solar heater installed on the roof heats up antifreeze. Once it gets hot a pump turns on and brings the antifreeze down into a transfer tank where it travels through coils like a radiator. The heat is transferred to the surrounding water which can be used directly, or in most cases is pumped into a standard water heater to ensure that there is always a ready supply of hot water.
There are a number of types of systems: evacuated tubes, flat plate collectors, batch collectors, etc. Info can be found online. At Chewonki we use evacuated tubes because of the cold climate we live in. They are very efficient at retaining the heat gained from the sun. These provide year round heat, except when covered in deep snow.
A typical system costs $4000-6000 and has a payback period of 4-6 years. This means that the energy savings over the course of 4-6 years equals the cost of putting the system in. In Maine, and many other states rebates and tax incentives lower the cost by a quarter to a third. There are also Federal Tax incentives which will offer a tax rebate of 30% for renewable technologies. These programs combined would typically cut the cost of a system, and the payback period, in half.
Systems are designed to last about 15 years. That means an average of 10 years of free hot water. Damaged evacuated tubes can be replaced individually and do not effect the functioning of other tubes.
At Chewonki we use evacuated tubes from Apricus, and a control system by Purist Energy. The Purist Energy system allows the entire system to be installed by plumbers and roofers and avoids the costs associated with a solar specific person being involved in the installation.