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What size solar system do I need?
For residences with a dishwasher and an automatic clothes washer, a rough rule of thumb is 10-square-feet of collector area, per person, and 20 gallons of water storage, per person. Thus, for a family of four, two CPC2000 collectors and a storage tank of 80 gallons are typical. It must be noted that if you use gas as a backup Duke Solar systems will include two tanks, the solar system tank preheats the water that goes into the gas auxiliary tank.
Families can also purchase a solar-assisted system that uses a single CPC2000 collector that is retrofitted to their existing 40-or 52-gallon water heater. Due to the reduced storage tank capacity and smaller collector size, these systems will only provide 50-60% of the hot water used. The installed price will of course be lower since the existing tank and only one collector are used.
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Do I have to change my habits to use a solar water heater?
No. Solar water heaters are always installed with a backup heating system in the storage tank to ensure that hot water is available at all times. However, to maximize solar utilization and your savings, you should attempt to use the most hot water in the late morning and early afternoon when the solar system is operating at its peak due to the available sunshine. Also, your solar system will be more effective if your use of hot water is spread more evenly over the week. For example, if you use hot water for laundry, instead of washing seven loads of clothes in a single day, wash one load each day. This will reduce the amount of backup energy required for your solar system.
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How much does a solar water heater cost?
In most parts of the country, an installed solar water heating system can cost anywhere from $1,500 to $4,500. Why the large range? System cost depends upon certain variables, such as the following:
- Size of family to be served
- Size and type of solar system
- Type of financing available
- Type of roof on which the collector is to be installed
- Amount of possible utility rebate incentive
- Building code requirements
- Professional versus do-it-yourself installation
Solar water heating is economically competitive with electrical and propane heating. During the winter of 2000-2001 the price of natural gas spiked and put the cost of gas and electricity close to the same. Duke Solar Systems are also competitive with dedicated heat pumps and heat recovery units, depending upon the individual situation.
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Does government offer any financial incentives?
Federal tax incentives are available for commercial and industrial solar hot water systems. These include a 10% investment tax credit and a 5-year MACRS with a 50% bonus depreciation in the first year. Other state and local incentives may also be available. North Carolina, for example, has a 35% income tax credit up to a limit of $1400 for a residential and $250,000 for a commercial or industrial solar hot water system. These incentives are important and can reduce the cost of buying a solar hot water system by up to two-thirds, so consult the Data Base for State Incentives for Renewable Energy at www.dsireusa.org.
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How do I finance a solar water heating system?
The best way to finance a solar energy system is to include it as part of your home mortgage. In long-term loans of 20 years or more, the monthly solar savings will normally be greater than the monthly mortgage payments for the solar system. In new construction you will save much more on your monthly energy bills then the increase in the house payment. It provides a positive cash flow for the day you move in.
If you are buying an existing home with a new mortgage, you may be able to include a new solar water heater in the mortgage. Check with your local lending office. Also, many local and national lending institutions offer short-term loans for solar systems, based upon the applicant's personal credit rating.
We’ll even allow you to charge it to your credit card account.
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Since there are several different types of solar water heating systems, how do I know which one is right for me?
Your choice depends on what works best for your home. If you want a simple passive system, one that has no moving parts you will want a thermosiphon system. You must also be aware, that the storage tank is located above the collectors and will be on the roof or on a ground mounted rack.
If you do not want a storage tank on the roof and prefer to see only the collectors, you will want the active system that requires a circulation pump and controller to transfer the heat from the solar collectors to the storage tank location inside the house or garage.
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What is the proper orientation of the solar collector?
Collectors should be mounted on an unshaded area of a south-facing roof. They can face up to 45 degrees east or west of south without a significant decrease in performance.
For all shingle and tile roofs that generally have pitches greater than 3 in 12 (i.e., 14 degrees), collectors should be mounted parallel to the roof. Collectors mounted in this manner are more aesthetically pleasing. However, for flat or very low-sloping roofs, collectors should be tilted at an angle (to the horizontal) that is approximately equal in degrees to the local latitude. Since the sun is lower on the horizon during the winter months, tilting the collector at an angle up to 15 degrees greater than latitude will increase winter performance, which is desirable in most cases.
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How do I protect my solar system from freezing weather?
Freeze protection is an absolute must for any solar system because a single freeze can destroy a collector. Even in Miami, FL or Houston, TX, collector tubes have frozen and burst during hard winter freezes.
In order to avoid problems, we recommend that all direct solar systems be designed and installed with two freeze protection methods. Or use an indirect system that incorporates a heat exchanger and uses antifreeze and the heat transfer fluid.
In the southern climates, direct systems use flush-type freeze prevention valves are being used. These valves open when the air temperature approaches freezing. Water pressure forces water from the storage tank through the collectors and out through the valve. The valve closes when the water leaving the valve reaches 50° F. This process prevents the water in the collector tubes from freezing and rupturing the tubes. Though water is purged from the system and lost, only a few gallons are needed to protect the collector from freezing.
Another method of freeze protection is achieved by water recirculation. When the temperature drops below 40° F, a collector freeze sensor activates the pump to circulate warm water through the collectors. A second level of protection in this system, in the event of power failures, is provided by manual drain valves that are opened to drain the collector or the freeze protection valve mentioned above.
An indirect system is the right choice for cold climates where freezing temperatures are recorded either during the night or during the day. An antifreeze solution, similar to that used in automobiles, is circulated through the collector. A heat exchanger between the collector and storage tank transfers heat from the antifreeze to the potable water. Although this system is usually more expensive and less efficient than direct systems (in which the water used for bathing, etc., is the same water circulated through the collectors), it provides better automatic freeze protection in colder climates.
Duke Solar- Indirect pumped system using antifreeze solution
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Are solar water heating systems reliable?
Properly designed and installed systems with glass-covered collectors should perform well for more than 20 years. Controllers, like other electronic devices, may require servicing during the life of the system, and the pump and hot water tank may have to be replaced after 10 years. Since conventional water heaters have the same expected lifetime, water tank replacement costs are not regarded as unique to solar energy systems.
Normal maintenance consists of checking pipe insulation, roof penetrations and collector mounting, pump operation and tank flushing. The latter is also recommended for conventional water heating systems, as is periodic replacement of the water heater sacrificial anode rod.
Many installation firms provide yearly maintenance checkups of their solar systems similar to annual air-conditioning system maintenance programs. These can be beneficial in extending the life of the system and ensuring optimum performance.
It is important to request that the installer put an indicator on your solar system showing that the system is working. It can be as simple as a small light that comes on when the system is operating.
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If I order a solar system, what do I get?
We will sell you our packaged system that includes almost everything you need to complete the job. Collectors, storage tank control and pump, roof flashings, valves and air vent as described on the diagram above. You or your installer will need to supply the ½” copper pipe and insulation to connect the collectors to the heat exchanger on the storage tank.
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What other costs can I expect?
A crating charge to protect the collectors and shipping/freight charges are the only other costs. If you pick it up at one of our distributors or at our warehouse you can save these fees.
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Where can I buy a solar system?
Call the Duke Solar office at 919-871-0423 we will sell it to you or direct you to one of our qualified dealers in your area.
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