Solar Domestic Hot Water Systems
Photo Courtesy: www.avisplumbing.com
Solar hot water systems collect energy from the sun in panels or tubes to produce domestic hot water used in a home or building. Hot water produced for use in a home or building is stored on site in tanks. A domestic solar hot water system can be a cost-effective way to reduce energy costs from gas, electric, or propane sources. They can be used in any climate, and the fuel they use -- sunshine -- is free.
Types of Systems
Solar water heating systems include storage tanks and solar collectors. There are two types of solar water heating systems: active, which have circulating pumps and controls, and passive, which don't.
Active Solar Water Heating Systems
There are two types of active solar water heating systems:
- Direct circulation systems - Pumps circulate household water through the collectors and into the home. They work well in climates where it rarely freezes.
- Indirect circulation systems - Pumps circulate a non-freezing, heat-transfer fluid through the collectors and a heat exchanger. This heats the water that then flows into the home. They are popular in climates prone to freezing temperatures.
Passive Solar Water Heating Systems
Passive solar water heating systems are typically less expensive than active systems, but they're usually not as efficient. However, passive systems can be more reliable and may last longer. There are two basic types of passive systems:
- Integral collector-storage passive systems - These work best in areas where temperatures rarely fall below freezing. They also work well in households with significant daytime and evening hot water needs.
- Thermosyphon systems - Water flows through the system when warm water rises as cooler water sinks. The collector must be installed below the storage tank so that warm water will rise into the tank. These systems are reliable, but contractors must pay careful attention to the roof design because of the heavy storage tank. They are usually more expensive than integral collector-storage passive systems.
A fundamental requirement for a solar system is to have a sunny location where solar collectors can function properly. Locations were the sun is blocked from the collectors by the slope or aspect of the land, trees, neighboring buildings, or other obstructions will reduce efficiency. Solar collectors need to be placed where plenty of sunshine strikes the surface of the collectors, year round.
Determine the correct system size of your solar water heating system by calculating the total collector area and the storage volume you'll need to meet 90%–100% of your household's hot water needs during the summer. Solar system contractors use worksheets and computer programs to help determine system requirements and collector sizing.
Prior to making the decision to install a solar system, determine if there are restrictions to placing solar collection panels on your home, by checking with your homeowner’s association, local building codes and zoning ordinances.
Cost & Maintenance
A solar hot water system will cost more than a conventional water heating system. The overall cost is determined by the size and complexity. The homeowner or a licensed solar contractor can estimate the cost. An online tool is located at www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12780.
Tax incentives and rebates may be available. Check with your local government and utility company to determine what incentives or rebates they may offer, as well. Long-term cash flow analysis should be considered before a decision is made.
A basic system will cost several thousands of dollars per collector to install, and there are some ongoing maintenance costs to consider. It is very important to have your system properly maintained to optimize its performance and to avoid maintenance problems. Regular maintenance on simple systems can be as infrequent as every 3-5 years. Learn more about solar water heating system maintenance and repair.