Deciding what type of collectors to use and the question of economics requires a little education on the subject. Go there to learn about large scale solar water heating potential with Powermats as well.
Anyone with a hot water tank can use solar energy. Keep in mind these things don't pay for themselves quickly so you want to get more out of it than a reduced energy bill. Add valves so you can take hot water directly off the coil (#10 below) in the solar tank. If its been sunny you can shower, wash the floors , car etc with free heated water from the sun directly. The temperature won't be as hot as the hot water tank usually and as its used up you'll notice the temp. dropping. This tells you you've used up the free heat and you can switch the valves back and take hot water from the hot water tank again. This system is the heart of any residential solar heating system. If you want to heat space its best done with separate coils in the floor (in floor heating). Just pump the low pressure solar water through the floor when you want to add heat to the space. You can add yet another pump to circulate the hot water tank through the coil in the solar tank. This allows you to heat the space with the hot water tank! This is a great solution for a house with some back rooms that don't currently have heat. I really don't recommend these systems to people who just want a quick return on their investment. You have to find joy in heating at no cost and using the earth's resourses in a sustainable responsible manner. Remember the environmental movement?
As shown in the diagram cold water picks up heat from the solar storage tank(7) before entering your hot water tank(9). A differential temperature thermostat (5) turns the solar pump (4) on automatically whenever the roof temperature is higher than the tank temperature. At night or once the maximum tank temperature is reached the pump shuts off and the collectors(1) fully drain back to the 65 gallon tank (7). As a result this system can be applied in freezing conditions as long as all the piping slopes back to the tank and there is no exposed piping below tank level. Insulating outdoor piping doesn't prevent freeze damage. It just increases the time it takes to freeze.
The vacuum breaker (2) is standard with any solar system. It allows air to enter so the collectors can drain when the pump(4) is off.
The vacuum breaker (3) is existing in some plumbing codes It protects the hot water tank (9) from negative pressure (vacuum).
The float valve (6) kills power to the system if the tank level drops too low. When the lights on the differential thermostat go off its time to top up the level of water in the tank. This feature protects the pump in the event of a leak in the system.
An overflow tube (8) vents the tank and prevents overfilling.
A thermometer (11) is a simple way to monitor the temperature of the water leaving the solar tank.
A coil of copper pipe(10) in the tank allows the pressured cold water to exchange heat from the water in the solar storage tank.
The solar storage tank (7) is insulated to R-12. Even at 60C (140F) the tank will lose only a few degrees over night. Morning showers can take advantage of yesterday's sun.
Our standard PMI-65 solar domestic water pre-heating system includes 2) 4'x10' Powermats (7.6 square meters) and 65 gallons (290 l) storage. Unfortunately my honest sales approach has killed the market for these and we're not making them anymore. However they are simple enough to fudge together yourself. I'm giving you the best design possible right here at no charge. many variations are possible. I'll be glad to help you find all the parts you might need.
In almost any household you will get more heat from a boxed and glazed or evacuated tube system of the same area. If you check you will find that usually competing systems are using far less collector area. If your hot water consumption is low enough a smaller, more expensive collector type system may be a better choice. As the load increases and economics start playing a role the Powermat system will deliver the most bang for the buck in many cases. As the load becomes huge Powermats are the only way to achieve the good economics that become possible. If you don't get much sun through cold winter months, usually the Powermat collectors will be the best choice. E-mail me with questions etc. Always check with local suppliers first. See if you can get a tank like the one above locally. There are plenty of old used systems around.