The first time you see a solar panel create steam when bleeding the air from the system, as your filling it with water for testing, you and any others working nearby will be shocked. To think the sun will do just that- is amazing. But the first step in the process of a solar installation is site development as it is necessary to place the collectors on a roof, wall or a platform of some type. The different systems require different amount of space. Shading and orientation is also an important consideration. The south, southeast and southwest orientations are the easiest slopes to make work as the different telescoping and adjustable brackets allow many different configurations. To take full advantage of the sun, shading should be very limited. Chimneys, dormers, trees, and other buildings may block the sunshine or severely restrict the fuel source, sunlight. The three most commonly installed systems are the integral collector storage system, flat plate collectors and the evacuated tube collectors. The integral collector storage system is simply a tank placed in a black box and water from the water heater is circulated through the tank. This system is limited to areas where the temperature does not go below freezing. The evacuated tube collectors are generally installed in commercial applications. The flat plate collectors with a heat exchanger is by far the most common system seen on homes throughout the country for its ability to function year round producing domestic hot water. Even with temperatures as low as the single digits, a properly installed solar system will produce substantial quantities of hot water. The following information pertains primarily to the flat plate collector system.
A solar system, the number of collectors and size of the water heater, is designed as to the number of occupants the system would serve. Most systems are designed to supply 100 % of hot water in the summer. As a general rule of thumb for a flat plate collector system, 20 square feet of collector surface is needed for each of the first two occupants. For each additional occupant 8 square feet is added for those living in the southern US and 14 square feet is added for those living in the colder regions of the US. After determining where the system will go, you need to obtain the panels and a heat exchanger or solar water heater.
When placing the solar panels on a roof, the roofing material should be replaced with a high quality, long lasting roofing material so the panels would not need to be disassembled to replace the roofing anytime soon. Make sure you add this cost into the system installation budget. For example, rubber roofing should be installed on flat to slightly sloped areas and a heavy, asphalt shingle with at least a 30 year service life on a shingled roof
As most areas of the country experience some cold weather, you need to install a system that either automatically shuts down the system and drains when temperatures reach freezing or a piping and panel system that is a separate loop from the domestic hot water system. Self draining systems do not need a heat exchanger, are connected directly to the domestic hot water heater, but are not as common as the self contained systems with a heat exchanger. Self draining systems tend to be more problematic.
A solar system configuration is a simply a loop consisting of components and piping. When the solar panels are connected on the roof, an insulated feed and return piping is installed from the panels through any attic space to the water heater and/or utility area. In a two story home, it is best to find closets that are aligned above and below each other, on each floor. In a single story house find a closet or any room may be used where the piping and wiring can be installed in the corner and then enclosed in a chase. With a platform system, the feed and return piping is insulated and buried underground from the panels to the house. A small gauge wire is also installed along the piping as a sensor is located in the solar panels to gather and send temperature information. The sensor informs a control and circulator to pump fluid through the loop when the temperature at the panels exceeds the water heater or heat exchanger temperature.
After the collectors and piping are in place, a heat exchanger needs to be installed. A heat exchanger is needed to transfer the solar heated fluid to the domestic hot water. The heat exchanger needs to be located in the utility area or a (solar) water heater is purchased with a built in heat exchanger. To picture a heat exchanger, think of a large hollow, metal spring shaped device (a coil) that is installed at the interior of the solar water heater. The solar heated fluid can travel through the interior of the coil and exchange temperatures with the water outside the coil yet inside the heater. A separate heat exchanger functions in the same method yet another loop is needed to circulate water from the hot water heater through the heat exchanger and back to the water heater.
So the heat is transferred and the fluid is circulated back to the panels to be re-heated through the return piping. The fluid is generally a mix of non toxic antifreeze and water. The cycle repeats itself as long as the sun is shining and temperature in the panels remains adequate. Some systems that were installed in the 70’s are still functioning today and with regular simple maintenance, a new system should last well over 20 years.
With the odd energy market and the cost of fuel unpredictable, the future costs for fuel does not look encouraging. Producing heat for domestic hot water is often 15% to 20 % of the average household energy budget. Long term savings with a solar installation has proven reliable and is an energy conscience decision.
