subject: The Basics About Solar Water Heating System For Homes [print this page] Solar water heating systems for homes can be seen on more and more roofs. These systems preheat the incoming cold water to be used in baths, kitchen and to do laundry. When sized correctly, a solar water heating system will supply about 40-70% of your hot water needs. In order to qualify for the currently available federal tax credits however, your system must provide at least 50% of your water demand. Combine these tax credits with the increased efficiency of modern systems, and it has become affordable for many homeowners to install a solar water heating systems.
Domestic solar water heating systems are either an open loop system or a closed loop system. Open loop systems are used in areas where temperatures don't drop below freezing and where the water is soft. The domestic water loop is open to the solar collectors in these systems, and the incoming cold water is run directly through the solar collectors and from there to the solar storage tank. In a closed loop system, the domestic water is isolated from the solar collector loop by a heat exchanger. The liquid running through the collector loop is freeze proof and is usually a glycol solution. Unfortunately, the closed loop systems required in colder areas and regions with hard water, cost more because of the added heat exchanger.
Number and size of solar collectors will be determined based on the type of collectors, where you live and on your hot water demand. Solar collectors for water heating most frequently installed are flat plate or evacuated tube collectors. Evacuated tube collectors have a higher efficiency than the flat plate collectors and are recommended for colder or cloudy climates and regions with hard water. You will pay a premium however, for the higher efficiency evacuated tube collectors.
You will need to keep your domestic water heater, or add one in your new home, even with the solar water heating system. It is a must to have this back-up full-sized water heater to ascertain that you have enoughsufficient hot water, even in the event of numerous days of overcast or snowy weather. A solar hot water storage tank is also installed, in addition to the standard water heater mentioned above. Consider the solar water heating system as a system that PRE-heats the incoming cold water on most days. It will be heated to the required temperature in the regular water heater. With a correctly designed system, enough hot water will be made in the solar collectors on sunny days to not require the regular water heater to be used. When you have several days of overcast weather however, that is when the regular water heater kicks in.
The most important decision made for a solar water heating system installation is the location of the solar collectors. Even the best evacuated tube collectors will perform poorly if they are mounted in an area that is shaded half of the time. Tools are available to measure or calculate the solar radiation in your location. Some calculation programs, available online, are free. All will require you to do some of the work yourself, such as collecting some data and entering it into tables or forms. You can also buy an instrument to measure the solar radiation at your location. Or you can try your friendly local solar system installer. They might give you a free analysis.
Now on to the roof itself. Will it need strengthening? How exactly will the collector support system be attached to the roof? What about the pipe penetrations? What will be needed to make sure that the roof is still completely waterproof after the solar system has been installed. Talk to a trusted contractor.
Ok, let's look what is needed in the house. Here you will need space for the solar storage tank, pump and possibly a small expansion tank, if you will have a closed loop system. How much space? To be on the safe side, allow at least 2 1/2 times as much space as your existing water heater has. This needs to be right next to the water heater. Allow enough space for easy access for maintenance.
Almost done. One more thing. The pipes. How and where can you run them between the solar storage tank and the solar collectors on the roof? You have to find either two locations that can each accommodate a 1" pipe with 1" insulation, or install them next to each other in the same chase. Hint: closets or walls behind toilets, if the first floor toilet is below the second floor bathroom. Avoid having to build pipe enclosures in the living room or dining room. Expensive and not very nice looking, unless you can be creative and hide the pipes behind a shelf.
That's it. You have done a lot of the important up-front work. Hopefully you now know enough to be dangerous, can make educated decisions and ask the right questions about how to plan, design, purchase and install, or have installed, a solar water heating system for your home.
