Solar Water Heaters. How they Work

By the Department of Energy

Solar water heaters—also called solar domestic hot water systems—can be a cost-effective way to generate hot water for your home. They can be used in any climate, and the fuel they use—sunshine—is free.

How They Work

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.

Most solar water heaters require a well-insulated storage tank. Solar storage tanks have an additional outlet and inlet connected to and from the collector. In two-tank systems, the solar water heater preheats water before it enters the conventional water heater. In one-tank systems, the back-up heater is combined with the solar storage in one tank.

Three types of solar collectors are used for residential applications:

• Flat-plate collector

  Glazed flat-plate collectors are insulated, weatherproofed boxes that contain a dark absorber plate under one or more glass or plastic (polymer) covers. Unglazed flat-plate collectors—typically used for solar pool heating—have a dark absorber plate, made of metal or polymer, without a cover or enclosure.

• Integral collector-storage systems

  Also known as ICS or batch systems, they feature one or more black tanks or tubes in an insulated, glazed box. Cold water first passes through the solar collector, which preheats the water. The water then continues on to the conventional backup water heater, providing a reliable source of hot water. They should be installed only in mild-freeze climates because the outdoor pipes could freeze in severe, cold weather.

• Evacuated-tube solar collectors

  They feature parallel rows of transparent glass tubes. Each tube contains a glass outer tube and metal absorber tube attached to a fin. The fin’s coating absorbs solar energy but inhibits radiative heat loss. These collectors are used more frequently for U.S. commercial applications.

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.

Download high-resolution diagram:
JPG (ZIP 101 KB) | EPS (ZIP 210 KB)

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.

Download high-resolution diagram:
JPG (ZIP 89 KB) | EPS (ZIP 206 KB)

Solar water heating systems almost always require a backup system for cloudy days and times of increased demand. Conventional storage water heaters usually provide backup and may already be part of the solar system package. A backup system may also be part of the solar collector, such as rooftop tanks with thermosyphon systems. Since an integral-collector storage system already stores hot water in addition to collecting solar heat, it may be packaged with a demand (tankless or instantaneous) water heater for backup.

For more information about solar water heating system components, see the following information:

• Heat Exchangers for Solar Water Heating Systems
• Heat-Transfer Fluids for Solar Water Heating Systems

Selecting a Solar Water Heater

Before you purchase and install a solar water heating system, you want to do the following:

• Consider the economics of a solar water heating system
• Evaluate your site’s solar resource
• Determine the correct system size
• Determine the system’s energy efficiency
• Estimate and compare system costs
• Investigate local codes, covenants, and regulations.

For information about specific solar water heater models and systems, see the Product Information resources listed on the right side of this page (or below if you’ve printed the page).

Installing and Maintaining the System

The proper installation of solar water heaters depends on many factors. These factors include solar resource, climate, local building code requirements, and safety issues; therefore, it’s best to have a qualified, solar thermal systems contractor install your system.

After installation, properly maintaining your system will keep it running smoothly. Passive systems don’t require much maintenance. For active systems, discuss the maintenance requirements with your system provider, and consult the system’s owner’s manual. Plumbing and other conventional water heating components require the same maintenance as conventional systems. Glazing may need to be cleaned in dry climates where rainwater doesn’t provide a natural rinse.

Regular maintenance on simple systems can be as infrequent as every 3–5 years, preferably by a solar contractor. Systems with electrical components usually require a replacement part or two after 10 years. For more information about system maintenance, see the following:

• Solar Water Heating System Maintenance and Repair
• Solar Water Heating System Freeze Protection
• Scaling and Corrosion in Solar Water Heating Systems

When screening potential contractors for installation and/or maintenance, ask the following questions:

• Does your company have experience installing and maintaining solar water heating systems?
  Choose a company that has experience installing the type of system you want and servicing the applications you select.
• How many years of experience does your company have with solar heating installation and maintenance?
  The more experience the better. Request a list of past customers who can provide references.
• Is your company licensed or certified?
  Having a valid plumber’s and/or solar contractor’s license is required in some states. Contact your city and county for more information. Confirm licensing with your state’s contractor licensing board. The licensing board can also tell you about any complaints against state-licensed contractors.

For contractor information, see the Professional Services resources listed on the right side of this page (or below if you’ve printed it out).

Improving Energy Efficiency

After your water heater is properly installed and maintained, try some additional energy-saving strategies to help lower your water heating bills, especially if you require a back-up system. Some energy-saving devices and systems are more cost-effective to install with the water heater.

Solar water heating systems explained

solar water heating systems

 If you are like many of our customers who found us by doing internet searches and have an interest in investing in the environment and lowering your monthly home energy bill. Now may be a good time consider installing a solar water heater with Charlotte Solar Power. Solar water heating systems come in an array of different makes and configurations and can be applied in many different scenarios. If you are interested in reducing your energy costs, and want to use the suns natural radiant energy to heat your pool or hot water, consider installing a solar water heating system with us. Solar water systems are efficient and don’t cost a penny to run when compared to the alternative “conventional” electric water heating systems.

 Conservatively speaking, we have found that in 99% of the installs we have done, our customers can count on reducing running (energy) costs by approximately 50-80%. This is great news, considering a significant part of energy cost for your home comes directly from heating hot water.

How do solar water heating systems work work? Solar water heating systems use absorber panels to harvest the sun’s energy. These absorber panels are in many cases installed on the roof of your home or garage. As the sun shines on the absorber panels, water is heated in tubes located in close proximity to the panel system or in a storage unit connected to a conventional water heater. Solar water heating systems give in many cases allow homeowners use the solar source as their main system and the conventional system as their back-up. Optimally placed absorber panels, with conventional methods as a backup will yield you many years of use and dramatically lower energy costs all while lowering your carbon footprint and contributing to a greener world.

 Interested in using the sun to run your hot water system?

Here are a few questions you’ll need to consider before hiring a professional to install your system. Naturally, we are available to assist you if you have any questions or need direction in any way.

 Is your current system running efficiently?

Some newer homes are equipped with Energy Star, or on demand water heating appliances which dramatically cut back on energy costs.

 Do you have the initial investment capital to purchase a solar powered system?

Right now Local, State, and Federal tax credits and incentives can be applied to help offset the costs of your installation by up to 55-60% making the up front cost more affordable. Contact us if you have any questions.

 Are there enough solar experienced installation and repair professionals in your community to keep your system up and running?

SolarNC has been an industry leader here in North Carolina and South Carolina for years and takes a customer centric approach to installs. We operate on a 24 hour clock and have certified technicians and experts on standby to address any need.

Massive Growth Ahead for USA Solar Installers/System Integrators/EPC Companies

8 Mar, 2011

First Solar,MEMC,Sharp,Solar Energy,Solar EPC,Solar Panels,Solarworld,Sunpower,Suntech,USA,Yingli

 

The US is the world’s largest electricity producer and consumer with a total electricity capacity of around 1 Terawatt.The share of Solar Energy in the US Electricity Production is negligible compared to around 19% for Nuclear Energy and around 2-3% for Wind Energy.However Solar Energy in the US is set to grow at high double digits over the next 2 decades as the Costs of Solar Energy Decline with prices of other Energy Forms set to rise.In some states like Hawaii and California,solar energy prices are already at grid parity with retail electricity prices.Some states like New Jersey,Colorado,Arizona have seen sharp increases in solar energy adoption over the last 2-3 years boosted by state specific government policies and subsidies.With the US Federal  30% Cash Grant on System Costs and falling systems prices for solar systems,the growth in inevitable.The US Solar Market has seen the rise of a number of innovative and fast growing system integration and installers.Some companies have come up with innovative financial solutions to solve the high initial investment hurdles in solar systems through leasing and financing plans.Here are a list of Top US Installers/System Integrators.Note the list will keep expanding in the coming years as the size of the US Solar Energy Market Grows.

The Large Vertically Integrated Solar Panel Installers

1) SunEdison/MEMC – US Polysilicon and Wafer Producer MEMC bought Sunedison which was one of the largest solar installers in 2008.Now MEMC is strongly expanding the system installation business not only in the US but other parts of the world like India,Europe,Korea,Canada and other places.The company recently installed one of the biggest solar plants in the world in Rovigo,Italy

2) Sunpower – Sunpower is a vertically integrated solar energy company known more for its highest efficiency solar panels.The company bought Powerlight a few years ago to enter the solar systems market and has bolstered the business constantly to become a major global installer.Sunpower is present in all 3 segments of the solar sytems business namely a)residential b)commercial and c) utility. It is one of the largest US installers and has recently won a number of large utility contracts for building solar farms.

3) First Solar – First Solar is the largest producer of solar panels in the world using its properietary thin film technology.The company is also one of the biggest utility solar system developer in the world focusing mainly on the North American Market.The company has built and sold the world’s largest solar farms in Sarnia,Ontario.The company has beefed up its solar installation business by buying project development teams and pipelines from Ausra,OptiSolar Turner etc.

4) Sharp/Recurrent Energy – Sharp recently bought Recurrent Energy one of the large independent solar power developers and system integrator in the US.Sharp already had a big presence in the California market where it is now facing increasing competition from the low cost Chinese players like Trina Solar,Yingli etc.

5) REC Solar - The Norwegian based Solar Company REC has started it solar system in the US a year or two ago and has managed to win some contracts..It is targeting all the 3 segments and is present in the major solar states of the US like New Jersey and Californa.It claims to be the largest residential solar installer in California with 17 MW of installations in 2010.

6) Solarworld - Another European company like REC,Solarworld is mainly targeting the utility and big commercial market recently winning a 11.6 MW order from LADWP.The company has a big manufacturing facility in Oregon and has aggressive expansion plans in the US as its domestic German market slows down.

7) Mitsui/Sunwize - Mitsui,the giant Japanese tradings house bought Sunwize in 2006 to enter the solar system market in the US.Note Mitsui is not a big solar panel producer like Sharp,Panasonice and others.The company sells mainly in Oregon and Californai and targets all the 3 segments of the market

The Solar Financing/Leasing Companies

8 ) Sungevity - Sungevity is a California company targeting the residential market through a solar leasing plan.It extensively uses the Internet to design the system and has a JV with US Bank to provide financing to its customers.

9) SolarCity - SolarCity is a full-service solar provider for commercial and residential customers and does solar power system design, financing, installation and monitoring services from a single source.SolarCity is introduced  a new solar lease option, called SolarLease.It also has other options like PPA .The company’s footprint extends to Arizona, California, Colorado, Maryland, Massachusetts, New Jersey, New York, Oregon, Pennsylvania, Texas and Washington D.C.

10) SunRun – SunRun is one of the newer solar installation and solar financing companies that target the residential market mainly.The company is present mainly in the Western  part of USA operating in 7 states Arizona, California, Colorado, Hawaii, Massachusetts, New Jersey, and Pennsylvania.The company uses a PPA model to sell solar systems and has partnered with a number of pure play solar installers

 

Solar EPC/Installation Companies

11) Akeena/Westinghouse Solar (WEST) - The first US Solar Installer to list on the US Stock Exchange,the company’s operations are based mainly in California.The company also sells solar sytems through retail outlets which was a first.The company also has a unique solar system which reduces solar installation costs called Mandalay.

12) Real Goods Solar (RSOL)- The second US Solar Installer to list on the Stock exchange,Real Goods Solar is present in California and Colorado and it targets the residential and commercial segments of the market

13) Verengo Solar - The company also provides solar financing solutions and is present in the California market.

14) Borrego Solar - The company is similar to Verengo Solar but mainly concentrates on the commercial market.The company signed a deal with Chinese solar panel producer Yingli for procuring solar panels.The company is headquartered in California like most others.

Summary

The US Solar EPC Market has a good mix of large vertically integrated solar companies as well as independent solar installers.The leasing and PPA companies have added another dimension to the Solar System Market by making it easier for customer adoption of solar energy.There a a large number of solar system installers in the US and its tough to include most as most of them remain private companies.Solar Installation is a huge growing business and has also attracted a number of shady companies.It pays to understand what is involved in the solar installation since customers are easily fleeced by a myriad of regulations and procedures.

Note Suntech,LG,Posco,Samsung are some of the other major foreign companies looking to build a major solar installation business in the US.Suntech has already won a utility deal and OCI and LDK have bought small US installers to accelerate their penetration of the US Market