A solar thermal system for home, or solar water heating system, is a technology that uses the sun’s energy to provide hot water.
Environmental_Impact
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FAQs
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Does_adding_a_system_affect_my_property_tax?
Are_solar_water_heating_systems_reliable?
Will_a_solar_water_heater_cover_all_my_hot_water_needs?
Can_I_use_a_solar_hot_water_system_to_heat_my_house?
Can_I_install_a_solar_water_heater_without_professional_help?
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Success_Stories
Environmental Impact
A solar thermal system for home, or solar water heating system, is a cost-effective way to supply hot water for your home, since sunlight reduces the amount of electricity or gas necessary to heat water. In addition to significantly lowered utility bills, carbon emissions associated with water heating are reduced and even eliminated. In the U.S., an average household with an electric water heater uses about 6,400 kilowatt hours of electricity per year to heat their water, which translates into approximately 8 tons of carbon dioxide (CO2) or almost double that emitted by a standard car.
Solar water heating systems come in a variety of configurations, depending on design, cost and level of complexity, but a typical system consists of a solar collector, a fluid system to move the heat from the collector to its point of usage and a hot water tank.
An Active system employs electrical or mechanical equipment to create forced circulation, and in the case of a passive, or thermosyphion, system, water flows by natural convection. Both usually include a supplementary energy source to serve as a back-up system when the water falls below a minimum temperature.
Available solar energy in the U.S.
Your solar water heater has to perform 3 basic operations in order to provide you with hot water:
1. The sunlight is collected and converted to heat energy via the solar collector mounted on your roof or another location with a southern orientation if you are in the Northern Hemisphere or a northern orientation if you are in the Southern Hemisphere and good solar visibility. The solar collector contains a conductive media, such as copper, which absorbs the sunlight in the most efficient manner and highly emissive glazing to help capture and retain the heat.
2. The collected energy is then transferred to a fluid, usually water that travels in channels through the copper panel. It flows to a storage tank where it is used either directly or indirectly via a heat exchanger. In active water heating systems, heat transfer fluid (water or an anti-freeze mixture) is pumped from the collector to the storage tank. In passive systems, the sun heats the tank directly, causing the transfer fluid to circulate through natural convection.
3. The solar-heated water goes to an insulated storage tank, which is larger in size than water tanks for conventional water heaters to ensure that a sufficient amount of water is collected for evening and night use. Some solar water heaters use a two-tank system, where water is preheated in one tank before it enters the conventional water heater.
There are 3 types of solar collectors used in solar water heaters – flat-plate collector, evacuated-tube solar collector and integral collector-storage system.
- A glazed flat-plate collector is a rectangular box that has a glass or plastic top to cover a flat black plate, which is attached to a set of parallel tubes or one winding
tube through which air, water and other heat transfer fluids pass. Unglazed flat-plate collectors (i.e. without a cover) are not as common, and are used mostly for pool heating.
- An evacuated-tube solar collector includes several glass tubes, each containing a metal absorber tube, through which the heat transfer fluid passes.
- Integral collector-storage systems, or batch systems, consist of one or more black tanks or tubes in a glass box. Cold water is preheated by being passed through the solar collector, and then continues on to the regular backup water heater. Since the pipes can freeze in cold weather, these systems should be only used in milder climates.
In active solar water heaters, heat transfer fluid is used in so called indirect circulation systems. In direct circulation systems, water is circulated directly from the collectors into the home.
Pool and Spa
Solar energy systems are a very good match for pool and spa heating. They are more economical as they are striving to provide lower temperature heat than is used for domestic hot water. Those systems typically do not have glazing and use a PVC plate medium for transfer storage. Additionally, they often use the existing pool pump for circulation, reducing the installation cost.
Passive design systems – thermal storage
Passive solar energy design uses the house itself as a storage vehicle for the energy collected. A house that has a large amount of mass (such as stucco or concrete) can retain a great deal of heat. Solar heated water can transfer its energy to the mass, heating the home through cold winter nights. During warm periods, the mass in the house can help cool the home, as there is a long lag time between the equalization temperature of the mass and the air. Passive design allows using the sun's energy directly, where the winter sun directly heats the mass of the home, and indirectly, where a fluid solar energy system transfers the sun's energy from collectors to the mass. Many passive solar home designs have been built and monitored. If you are considering building such a home, search 'Find a Supplier' or contact the Solar Energy Industry Association for a referral.
Purchasing and installing a solar water heating system in your home will normally cost you more than a conventional system (from $2,000 to $6,000 depending on the type of system), but it begins paying for itself right away with your reduced energy bills. According to the US Department of Energy, your energy bill should decrease by between 50 and 80 percent on average. The amount you save will depend on many factors, including:
- How much hot water you use
- Your system’s performance
- Your geographic location and amount of available sunlight
- Local cost of conventional fuels
- Available incentives and financing
Federal and state tax breaks, rebates and other incentives will allow you to make an upfront investment to cover the initial cost of your water heater. For example, you can get up to $2,000 in federal tax credits and many states offer property tax exemptions for solar systems and/or tax deductions for interest on loans for energy efficiency systems. To be qualified for tax incentives, your system must be certified by the Solar Rating Certification Corporation or a comparable entity endorsed by the state government in which the system is located.
Do I need special permits?
Does it affect my property tax?
Are solar water heating systems reliable?
Will a solar water heater cover all my hot water needs?
Can I use a solar hot water system to heat my house?
Can I install a solar water heater without professional help?
Do I need special permits?
You will need to obtain special permits before installing your solar water heater. Zoning and building codes relating to the installation of solar water heaters usually reside at the local level, so be sure to do your research and hire a certified installer familiar with local requirements. Most municipalities require a building permit for the installation of a solar hot water on an existing house. Often, the solar contractor will apply for the permit as part of their costs.
Does adding a system affect my property tax?
Having a solar water heater system in your home allows you to become qualified for a property tax exemption, currently offered by 26 states in the U.S. What it means is that your renewable energy equipment cannot be valued at a higher cost than conventional equipment when your property is assessed for tax purposes. In some states, the value of your solar water heater system is not included in the assessment, and in other states property tax assessments are conducted on a case-by-case basis.
Are solar water heating systems reliable?
Although today’s solar systems are considered highly reliable, you will still want to keep your conventional water heater for a back-up to further raise temperatures and to provide hot water during inclement weather (in many areas, local building codes require conventional back-ups). A solar water heating system may overheat or freeze if it is not properly selected, designed, and installed. Should the system freeze with fluid inside, there is the potential for pipes bursting. Make sure to do your initial homework before making a purchase and use professional help to install your system. Active solar water heater systems are best for areas where freezing temperatures are to be expected.
Will a solar water heater cover all my hot water needs?
In general, a correctly sized system will supply a range of 75 to 90 percent of your household’s hot water needs, taking into consideration overcast weather and periods of additional hot-water use. In the summer, your system might provide 100 percent of your hot water.
Can I use a solar hot water system to heat my house?
Yes, you can use a solar hot water system to heat your home. Instead of transferring the heated water to a domestic hot water heater, the solar hot water system (with oversized storage capacity) is connected to a radiant floor and/or panel radiator. This design is most cost-effective for new home construction rather than as a retrofit.
Can I install a solar water heater without professional help?
Although it is possible to install a solar water heater on your own, it is best to find a qualified licensed contractor to set up your system. This will save you the headache of figuring out various aspects of proper installation – protecting your roof integrity, local building code requirements, safety issues, etc.
Finding the right type of solar water heater system for your home will depend on a) calculating the total collector area and the storage volume to meet your hot water needs, and b) evaluating your home’s solar resource. Many companies that sell solar products offer free or low cost evaluation of your home and will help you choose the right system. A good place to start is the Solar Rating and Certification Corporation’s website, which lists all companies participating in their certification program. 'Search for a Supplier' of visit solar-rating.org Purchasing your solar water heater from a participating vendor ensures that your system meets industry standards, and helps you become eligible for tax credits.
Hawaii is the nation’s leader in per capita use of solar energy, due to its successful solar water-heating program. Almost one in every four single-family homes uses solar as a primary water heating system. Residents of Hawaii will save about $90 million on their electricity bills over the life span of their systems, which reduces greenhouse gas by more than 400,000 tons of CO2 and saves 1.35 million barrels of imported oil, enough to power Honolulu for two months.
In India, due to the low-cost financing provided by many commercial banks in the urban and rural parts of country, the market for solar water heaters expanded dramatically. In the 1990's an increase in the number of manufactures and involved banks resulted in solar water heating systems becoming a popular household item among ordinary citizens.
