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

Solarbuzz predicts U.S. solar market could grow tenfold by 2014

 

photo: courtesy of Curtis Morton-Lowerlighter

Solarbuzz’s latest report, “United States PV Market 2010,” reveals that the U.S. solar market grew 36% in 2009, responding positively to the economic downfall. These results rank the country’s solar photovoltaic market third largest in the world, behind Germany and Italy.

“2009 marked a year of transformation for the U.S. solar market,” said Craig Stevens, president of Solarbuzz. “Changes in the roles of utility companies, new market entrants, lower cost PV modules from Asia and new direct-to-market approaches became more prevalent. As a result, solar companies doing business in the States will need to adapt quickly to these challenges while also being responsive to frequent adjustments in the fragmented incentive and regulatory environment.”

California is still driving the solar power market in the U.S., accounting for 53% of on-grid installations in 2009 and maintaining this position into 2010. While SunPower remained leader for PV installed, Chevron Energy and SPG Solar moved up to the number position in California in 2009. Installers REC Solar, SolarCity and Real Goods Solar led the residential field.

The large number of state policy initiatives has created a fragmented regulations and incentive environment. However, states are doing their job of stimulating local markets. The dispersed funding sources mean the U.S. market does not does not carry the same level of risk compared to countries driven by a single national policy. Federal incentives are therefore due to play a much larger role in stimulating demand into 2012. Solarbuzz forecasts the market will grow to between 4.5-5.5GW depending on this given scenario. This is an average annual growth rate of 30% per annum.

The U.S. order book for photovoltaic systems currently stands at 12GW.

via http://www.pv-tech.org/

 

Department of Energy awards $27m to cut solar costs

3 hours ago

 

 The Department of Energy is awarding $27 million in projects to support the development, commercialization, and manufacturing of advanced solar energy technologies.

The award is part of the Department’s “SunShot” initiative to reduce the total costs of photovoltaic solar energy systems by about 75 percent so that they are cost competitive at large scale with other forms of energy without subsidies before the end of the decade.

By reducing the cost for utility scale installations by about 75 percent to roughly $1 a watt – which would correspond to roughly 6 cents per kilowatt-hour – solar energy systems could be broadly deployed across the country.

This will increase American economic competitiveness and help the U.S. regain leadership in the global market for solar photovoltaics.

Energy Secretary Steven Chu said on Friday: “America is in a world race to produce cost-effective, quality photovoltaics. The SunShot initiative will spur American innovations to reduce the costs of solar energy and re-establish U.S. global leadership in this growing industry.

“These efforts will boost our economic competitiveness, rebuild our manufacturing industry and help reach the President’s goal of doubling our clean energy in the next 25 years.”

The SunShot program builds on the legacy of President Kennedy’s 1960s “moon shot” goal, which laid out a plan to regain the country’s lead in the space race and land a man on the moon. The program will aggressively drive innovations in the ways that solar systems are conceived, designed, manufactured and installed.

In addition to investing in improvements in cell technologies and manufacturing, the SunShot initiative will also focus on steps to streamline and digitize local permitting processes that will reduce installation and permitting costs.

To achieve the SunShot goal of reducing the total installed cost of large scale solar electricity by about 75 percent, DOE will be working closely with partners in government, industry, research laboratories and academic institutions across the country.

SunShot will work to bring down the full cost of solar – including the costs of the solar cells and installation – by focusing on four main pillars:

• Technologies for solar cells and arrays that convert sunlight to energy;
• Electronics that optimize the performance of the installation;
• Improvements in the efficiency of solar manufacturing processes;
• Installation, design and permitting for solar energy systems.

As part of the launch of the SunShot initiative, DOE is also announcing $27 million in awards to nine new projects. This funding includes support for five projects that are receiving $20 million to further develop U.S. supply chains for PV manufacturing.

This includes support for companies across the solar energy supply chain, including U.S. material and tool suppliers and companies that are developing technologies that can be adopted directly into current manufacturing processes.

NREL

Additionally, DOE’s National Renewable Energy Laboratory is investing $7 million to fund the latest round of the successful PV Incubator program, which helps to shorten the commercialization timeline for promising emerging solar technologies.

The companies work closely with DOE national laboratories to scale their technologies and manufacturing processes and move the products from pre-commercial and prototype stage to pilot and full-scale manufacturing operations.

The PV Technology Incubator program has the primary goal of advancing the timeline and commercial potential of new manufacturing processes and products with the potential for dramatic price improvements.

“The startup companies awarded under the Incubator program will truly benefit the manufacturing processes and products in the United States through rapid commercialization of these innovative technologies,” NREL Incubator Manager Martha Symko-Davies said.

This is the fourth installment of the successful PV Incubator program where companies benefit from close partnership with the national laboratories.

Previous awardees including Calisolar and Abound Solar successfully developed new PV technologies with DOE support and are now rapidly scaling their domestic manufacturing operations while creating jobs in their communities. Calisolar currently has about 190 employees in California and 75 MW of capacity with plans to expand to 220 MW. Abound currently has about 350 employees in Colorado and 65 MW of manufacturing capacity with plans to expand to 775 MW with a recently announced $400 million federal loan guarantee.

Projects

In this current round, companies were selected in one of two categories: Tier 1, representing the development of commercially viable prototypes, receiving up to $1 million over 12 months; and Tier 2, representing the development and manufacturing scale-up of pilot-scale processes receiving up to $4 million over 18 months. Funding will be issued through the DOE’s National Renewable Energy Laboratory.

The Tier 1 projects, subject to negotiation:

Caelux, Pasadena, Calif., is developing a novel flexible solar cell manufacturing process and design, which will dramatically reduce production costs by minimizing the amount of semiconductor material used while also having vast potential to surpass standard device efficiency.

Solexant, San Jose, Calif., is developing a new thin film material comprised entirely of materials that are non-toxic and abundant on the Earth, including copper, zinc, tin, selenide, and/or sulfer (CZTS). These devices will be constructed with a non-particle ink that can be printed and will result in commercially viable efficiencies using scalable, low-cost processes.

Stion, San Jose, Calif., is developing a thin-film technology that will allow two high-efficiency thin-film solar devices to be stacked, allowing for much better absorption of light and creation of power. The devices are constructed in a way that significantly reduces cost, simplifies manufacturing and reduces material utilization over traditional designs.

The Tier 2 project, subject to negotiation:

Crystal Solar, Santa Clara, Calif., is developing a new technology for the fabrication, handling, processing and packaging of very thin single-crystal silicon wafers (four times thinner than standard cells). This solution uses much less silicon, eliminating many of the wasteful and expensive wafer-processing steps and addressing the problem of handling very thin wafers.

NREL is the Department of Energy’s primary national laboratory

Solar Industry Playing Critical Role in Creating Jobs, Driving Innovation and Maintaining US Competitiveness

January 25, 2011

 

WASHINGTON, D.C. – Rhone Resch, president and CEO of the Solar Energy Industries Association released the following statement today in response to President Obama’s State of the Union Address to Congress:

“Tonight we heard President Obama’s commitment to creating jobs and keeping America competitive in the global marketplace. The U.S. solar industry is playing a critical role in meeting both of these objectives.

“Tomorrow morning, nearly 100,000 Americans in all 50 states will go to work as they do every day – at solar manufacturing facilities; on the roofs of homes and business installing the latest solar technology; at offices offering support in finance, legal and marketing departments. More are finding work in solar every single day.

“At tonight’s address were Gary and Robert Allen from Rochester Hills, Michigan. Their company, LUMA Resources, utilized funding from the American Recovery and Reinvestment Act to transform their roofing company into a manufacturing facility of state-of-the-art solar shingles, creating new manufacturing jobs for Michigan workers. They are one example of thousands of companies that are finding new opportunity in the solar industry. With the right policy support, the U.S. solar industry is scaling up and allowing America to innovate and compete in the global marketplace. Congress should take notice of success stories like LUMA Resources when considering how to create new jobs and keep America competitive in the 21st century.”

Background Resources:

• Nearly 100,000 Americans in all 50 states work in solar according to The Solar Foundation’s National Solar Jobs Census. In 2011, solar firms are projected to add more than 24,000 new jobs nationwide with the fastest growth in manufacturing: http://www.thesolarfoundation.org/sites/thesolarfoundation.org/files/TSF%20Jobs%20Census%20Executive%20Summary.pdf

• So far in 2011, new solar manufacturing facilities have been announced in Oregon, South Carolina and Mississippi that will create as many as 2,500 jobs. The Recovery Act supported construction or expansion of 58 more solar manufacturing plants in 17 states.

• Today, there are more than 4,300 solar energy companies across the supply chain operating in the United States. Michigan and Oregon lead the top solar manufacturing states that include California, Massachusetts, Ohio and Washington.

• According to U.S. Solar Energy Trade Assessment 2010, a joint report from SEIA and GTM Research, the solar industry is a significant net exporter of solar products, with 2009 net exports totaling $723 million. Additionally, U.S. solar installations created $2.6 billion in direct value for the U.S. economy: http://seia.org/cs/news_detail?pressrelease.id=1144

• The solar industry had a record year in 2010. While Q4 numbers are still being compiled, the solar industry installed roughly 1,000 megawatts of total solar capacity in 2010 in the U.S. (enough to power more than 200,000 homes), double the amount installed in 2009: http://www.seia.org/galleries/default-file/SEIA_Q3_2010_EXEC_SUMMARY.pdf

• The solar industry employs Americans in all 50 states. Meet some of the faces of the solar industry and learn more about specific state data: www.SolarWorksforAmerica.org

• See how solar is working for Americans all across the country: www.SolarGenerationUSA.org

Media Contacts:
Jared Blanton, 202.556.2886, jblanton@seia.org
Brian Mahar, 703.302.8393, bmahar@tigercomm.us

About SEIA®:
Established in 1974, the Solar Energy Industries Association® is the national trade association of the U.S. solar energy industry. Through advocacy and education, SEIA and its 1,000 member companies are building a strong solar industry to power America. As the voice of the industry, SEIA works to make solar a mainstream and significant energy source by expanding markets, removing market barriers, strengthening the industry and educating the public on the benefits of solar energy. www.seia.org

New Report Finds U.S. is Net Exporter of Solar Products

December 14, 2010

According to an independent study by GTM Research, U.S. solar installations created $3.6 billion in direct value to the global economy in 2009. Of that, nearly 74 percent, or $2.6 billion, directly benefited the U.S. economy. Eighty-one percent of the domestic value created in the solar industry came from the photovoltaic (PV) sector, with concentrating solar power (CSP) and solar heating and cooling (SHC) making up the remaining 19 percent. The U.S. was a net exporter of solar energy products in 2009, led by the $1.1 billion in exports of polysilicon, the primary feedstock in most PV cells. For PV, China and Mexico contributed most to imports, while Germany, Japan and China were the most prominent export destinations.

View the full report and factsheet.

View the press release here.

Design Race in Wind Turbine Drivetrains

By Aedan Kernan / Published on Mon, 2011-01-10 11:15

The silhouettes of three-rotor offshore wind turbines on the horizon is familiar to millions of people in coastal regions around the world. But there is no universal design for the drivetrains within the wind turbines’ streamlined nacelles that sit on top of the turbine towers. A fascinating race – based on very different engineering philosophies – is developing as wind turbine manufacturers seek to upscale from the current 1.5 – 5MW offshore wind turbines to the 15MW super wind turbines with rotor diameters of around 145 meters planned for 2015.

Gamesa, the Spanish wind turbine manufacturer, announced at the end of November that it will enter the race to develop a 15MW wind turbine. It hopes to have a prototype ready in 2015. In early December Mitsubishi Power Systems Europe announced plans to invest around €120 million in a Scottish offshore wind R&D centre to develop their 15MW turbine. Mitsubishi also aims to have their turbine ready for 2015.

The technical challenges of the scale-up are daunting. Upwind, an EU-funded project with participation from many of the major industry players including Gamesa, concluded that substantial R&D and industrial effort is still needed to conquer all technical barriers. The new generation of wind turbines need to be more reliable and available, they need to make better utilisation of the wind, and they need to reduce their manufacturing costs, if they are to deliver the ultimate prize – electricity at prices equal to or below the cost of fossil fuel generation.

The only company to attempt the development of a 15MW wind turbine to date – Clipper Windpower – announced in the Autumn that it had run into ‘liquidity’ difficulties, despite the fact that it had already sold its prototype to an agency of the UK government. Clipper’s ‘Britannia’ wind turbine project was subsequently rescued by a 100% acquisition of Clipper’s shares by the engineering multinational UTC.

Top-heavy towers

Reducing the weight and size of the drivetrain housed in the nacelle at the top of the wind turbine tower is a crucial area of research for scale-up to 15MW. Today’s standard wind turbine nacelle houses a high-speed generator driven through a three- or four-stage gearbox. That design stacks a lot of heavy, complex technology at a great height. It is difficult and expensive to cconstruct. Larger nacelles tend to be less aerodynamic, affecting efficiency. The nacelle is exposed to considerable forces and vibrations. And maintenance – with the need for specialist vessels – is a major element in an offshore wind turbine’s total life costs.

Direct drive systems can simplify things in the nacelle. Removing the gearbox should deliver improvements in reliability and efficiency leading to reduced maintenance. But direct drive systems that deliver 15MW require very large diameter generators and it has proven difficult to produce direct drive technology that is lighter or more cost-effective than conventional geared drive trains. Today, Enercon is one of very few manufacturers supplying direct drive generators that have an electrical rotor with windings rather than permanent magnets.

In 2007, American Superconductor Corporation (ASMC) began work in partnership with industrial motor manufacturer TECO-Westinghouse on the design of a 10 MW wind turbine that would use high temperature superconducting materials in a direct drive generator system to remove weight from the nacelle. ASMC’s initial data indicates that the 10 MW wind turbine generator will weigh around 120 tonnes, compared to an estimated 300 tonnes for a permanent magnet direct drive 10 MW generator. However, the development timescales for the ASMC solution are unclear. Engineers at the US Department of Energy’s National Wind Turbine Centre, who work with ASMC, have estimated that it may take ten to 15 years to develop commercial HTS solutions for wind turbines.

Because of commercial sensitivities, Clipper did not publicize the details of the drivetrain for their 175-meter Britannia wind turbine with its three 72-meter rotors, each weighing 30 tonnes. Commentators expect the drivetrain to be a development of the ‘hybrid’ drivetrain developed for Clipper’s successful 120-meter high, 2.5 MW Liberty wind turbine.

The Liberty drivetrain is compact, with some of the advantages of a direct drive approach. The shaft from the rotors is connected to a fixed-ratio gearbox that drives four permanent magnet generators. Permanent magnet generators are simpler than the variable speed standard. There are no brushes or slip clutch for instance. The Liberty is reported to have about half the number of parts found in today’s standard turbines.

Each of the four generators is small and light enough to be handled by an internal hoist. The Liberty can continue to generate power when one or more of its generators is out. To improve reliability further, the Liberty’s powertrain is protected by a monitoring system that can detect wear or damage that might need unscheduled maintenance. The monitoring data enables the wind turbine’s managers to limit the possibility of further stress until the problem can be sorted.

Liberty’s fixed ratio gears mean that the generators speed up or slow down with the rotors. Clipper Windpower developed advanced power electronics to deal with this constant variation, fixing the frequency of the power, ready to be fed into the grid. Scaling up their power electronics is likely to be one of many major challenges facing the Britannia project team. The power levels will exceed the capability of power electronic components currently available.

Floating Challenge

The Norwegian SWAY consortium have worked with the German company Areva Multibrid, developing Areva’s M5000 turbine design for their 10MW offshore wind turbine. Its drivetrain takes a similar approach to Clipper’s in the search for compactness and less weight in the nacelle. A permanent magnet synchronous generator is directly installed in the machine housing. The generator’s rotor shaft is mounted on the output shaft of the gearbox so that it needs no own bearings.

The key area of innovation in the SWAY project is a floating tower. By placing their rotor on the downwind side of the tower, SWAY’s design team have found a way to allow the tower to tilt by more than 5 degrees while its 145-meter diameter rotors remain horizontal, without colliding with the tower. When the wind direction changes, the whole tower turns. Cables on the windward side reinforce the tower, so that a lighter structure can be used.

Game Changer

The latest 15 MW development project announcement, from Mitsubishi, promises a drivetrain that will be “game-changing”.

The Mitsubishi Digital Displacement Transmission (DDT) removes the generator and gearbox from the nacelle, replacing them with a series of much lighter hydraulic pumping modules working in parallel. The hydraulics turn a generator (or series of generators) housed at ground level. Because most of the critical equipment would be at ground level, maintenance costs are slashed. There could be other advantages. Hydraulic systems are much more reliable than mechanical systems in extreme environments. Torsional vibrations generated at the rotor hub would no longer affect the generator. That would improve reliability still further. DDT also enables the use of many common parts that could be easily handled by an internal crane.

However, there are certainly design challenges. A hydraulic system was tried before on a wind turbine and abandoned. Hydraulic systems are likely to be up to 30% less efficient than a mechanical system in moving energy from the turbine blades to the generator input shaft.

But one commentator writing in machinedesign.com before Mitsubishi’s announcement made the case for a DDT type solution:

“Hydraulics offer power density unmatched by any other technology, and power density is precisely what is needed in a wind-turbine nacelle. The efficiency gap may eventually succumb to new technologies like more-efficient fluids to reduce line losses and electrohydraulic-control systems to optimize performance.”

News: Greener Product Internationally Listed with Ecolabel Index

News /Ecolabel

 

LEED & NAHB Compliant Products Database Launched

Posted 3 January 2011 by Anastasia O’Rourke to Ecolabel News.

If your New Years resolution is to green your building and be recognized as such by LEED and/or NAHB; a new certification has been launched that can help get you part of the way there. The “Greener Product Certification Seal” covers LEED compliant products and NAHB approved products.

A product carrying the seal demonstrates that it has been evaluated against the LEED, LEED for Homes and NAHB green building standards using internationally recognized third-party certification organizations, laboratory test results and/or other supporting documentation.

Certified products are then listed online; and users can search by product category and environmental attributes (such as whether the material has recycled content, or low VOCs).

It is a great interface and useful service geared primarily towards a US audience. It will be interesting to see if it expands to other Green Building Councils and practitioners internationally.

Greener Product is Inviting Green Building Professionals to Join Expert’s Program

Experts Program

Greener Product LLC, the industry leading search platform, has established an expert’s program.  These certified green building professinals experts are listed online at www.greenerproduct.com and there is no cost to apply or participate in the program.

Experts will share their expertise and be promoted regularly to Greener Product data base of over 100,000 green professionals including architects, contractors and manufacturers.

To Learn more prospective experts can apply here.

Greener Product LLC

Greener Product LLC has developed the world’s first online platform that creates a vast marketplace for the analysis of sustainable and healthy building products. This one-stop resource is used by thousands of dedicated green professionals to research environmentally preferable building materials and to study vital information on how to use advanced building design to build green more effectively.