Ceramic materials help manufacturers of thin film photovoltaic cells achieve greater efficiency

The earth benefits from an impressive 125,000 terawatts (TW) of solar energy. While the future energy needs of the planet will undoubtedly be met with a combination of technologies, many believe that solar – in the form of photovoltaic (PV) cells – is the only renewable energy source with the capacity to make a significant impact on global energy production.

As a result, the race is on to push the performance of PV cells to a level where the total cost of the electricity generated is as cheap (if not cheaper) than that from carbon-based sources.   Some predict that grid parity, as it is called, could be achieved in some locations within as little as a few years.

Most of the effort in this direction is now centered on thin film deposition, rather than wafer-based modules, although there is still discussion around the relative merits of both.  The main arguments in favor of thin film are that it uses less material, and is much faster and simpler than the complex and delicate process of slicing, dicing and placing of silicon wafers.  This means that if the cost of deposition can be reduced, and the efficiency of the resulting PV cells increased sufficiently, the goal of grid parity will be achieved.

What most commentators and manufacturers do agree on is that, for significant increases in efficiency, all components of the equipment and all steps of the process must be considered; there is no one panacea that will achieve the goal in a single step.

Thin film deposition process

Thin film deposition has been used for some years for a variety of applications, including semiconductor and optical components, decorative and low-emissivity architectural glass, and most recently in the manufacture of flat screens for TVs and computers.  In solar cell production, the process offers a simpler and cheaper alternative to using silicon wafers.

Manufacturers continue to experiment with various materials and refinements of the thin film deposition process for solar cells based on silicon and other materials.  The direct band-gap semiconductors cadmium telluride (CdTe), copper indium diselenide alloy (CuInSe2) and copper indium gallium diselenide alloy Cu(InGa)Se2, have high optical absorption coefficients (>105cm-1) are now emerging as the most popular materials for the photo absorption layer in thin film  photovoltaic (TFPV) cells.  More than a dozen companies worldwide are already actively producing these cells, or are in a start-up phase.

Creation of the TFPV layers can be achieved by various methods; using a physical or chemical vapor deposition processes, particle sintering or electro-deposition for example.    Reports suggest that the best results are achieved using high temperature (up to approx 500°C) deposition and post-growth anneal of the TFPV layers.

While the processes are complex, and manufacturers continue to research, develop and refine, the essential features remain – high temperatures, aggressive and corrosive process materials.

Quality is key

To date TFPV cells have only achieved approximately 20% efficiency (which is the current benchmark for Crystalline Silicon PV cells manufactured in production quantity) over small areas and under laboratory conditions. In production quantities and large panel sizes the best efficiencies that manufacturers currently achieve is in the range of 10-12%.

In the push towards achieving the goal of grid parity, the manufacturing challenge is to create reliable and consistent process conditions that can reproduce laboratory quality in large quantities.

This is an area where manufacturers of PV cells and their equipment suppliers can benefit from the huge investment in materials research that has already been done over the years in the manufacture of semiconductors and flat screens, both of which have been through large-scale, fast ramp-ups in volume manufacture.

Ceramic – the perfect choice

Technical ceramic materials feature high hardness, physical stability, extreme heat resistance and chemical inertness.  As such, they are highly resistant to melting, bending, stretching, corrosion and wear – and ideal for use in environments of extreme heat and aggressive chemicals, like that of TFPV deposition.

Morgan Technical Ceramics, a division of the Morgan Crucible Company plc, is a world leader in specialist engineering of ceramic components.  A global business, the company is working with leading players in PV cell manufacture in USA, Europe and Asia, supplying a wide variety of components for both silicon-based and non-silicon based thin film solar cells.

Non-silicon thin film solar cell manufacture

In an application borrowed from the manufacture of architectural glass, fused silica rollers are used to move the hot glass panels through the deposition process.  The thermal stability of silica is exceptional; it has a coefficient of thermal expansion (CTE) of <1 x 10-6/°C – lower than any other ceramic material.  This low CTE combined with its chemical compatibility with glass make fused silica rollers an ideal choice for ensuring the glass remains perfectly flat during the process.

Morgan Technical Ceramics are supplying precision machined fused silica rollers for use in continuous flow TFPV deposition machines from its locations in Fairfield, NJ, USA and Yixing, China.

In TFPV deposition equipment, precursor vapors and gases are transported from a source vessel through a deposition zone onto a heated glass substrate to deposit the PV layer.  Morgan Technical Ceramics produces a number of components used in this part of the TFPV process.

In some instances, solid materials are melted and vaporized from ceramic crucibles or boats to form a flux that is deposited on the heated glass substrate.  It is critical that the ceramic crucible or boat be dimensionally stable and chemically non-reactive to the molten source material.  Pyrolytic boron nitride (pBN) ceramic is an excellent material for this application due to its high corrosion resistance and non-reactivity with the source materials used in PV deposition.  Morgan Technical Ceramics’ Hudson, NH USA site supplies pBN crucibles and evaporation boats made via a chemical vapor deposited (CVD) process that are ideal vessels due to the ultra-high purity nature of the CVD pBN material.  Further, Morgan Technical Ceramics provides pBN-coated graphite heating elements used for material vaporization.

In other configurations, vaporized precursor materials are transported from the source to the deposition zone via a vapor distribution manifold.  The manifold is formed from a perforated tube made of ceramic because it is one of the few materials with the chemical stability to operate without problems with these very toxic, hazardous chemicals, at high temperatures (above 500°C).

Morgan Technical Ceramics produces these tubes in mullite and in alumina, at its specialist extrusion facility in Waldkraiburg, Germany. Tubes are up to 2.5m (100inches) long x 105 mm (4inches) diameter, with multiple vapor exit points, for uniform deposition across the glass.   They are extruded, fired in large kilns, and then precision machined to achieve final product tolerances within +/-0.15mm (0.005inch).

Silicon-based thin film solar cell manufacture

Oerlikon Solar, a European manufacturer of thin film deposition equipment for PV panel production, is using precision-engineered, high-purity ceramic bars in some of its higher temperature thin film deposition machines, for lifting, stacking and aligning components and the glass panels inside the chamber.

The ceramic is semiconductor-grade 99% alumina, chosen for its excellent thermal and chemical stability as an alternative to stainless steel, which has a tendency to buckle and bend at high temperatures.

Morgan Technical Ceramics is able to produce consistent flatness of less than 0.01mm over the 1.2m length of the bar and parallelism of less than 0.05mm, with a polished mirror finish.  In fact, these tight specifications are well within the capability of the company’s specialist manufacturing facilities at Rugby, UK, where skills have been honed and refined through years of supplying critical components for the semiconductor, aerospace, laser and other demanding industries.

Ceramic pins, also made of high-grade alumina, are used as locators and separators between key components inside the TFPV deposition reaction module chamber.  Shaped like a drawing pin, the component is about 15mm in length with tightly controlled dimensions to enable consistent deposition of the thin film layers within the reaction module.

Morgan Technical Ceramics’ Stourport plant, also in the UK, produces several thousand of these pins per month, and is expecting to double its production volume within the next 12 months.

Summary

In all these examples, two things are key.  First, in these applications the very high quality engineering ceramics are not operating any where near the boundaries of their thermal and chemical stability.  TFPV manufacturers are free to continue experimenting with higher temperatures and different thin film materials, safe in the knowledge that these components of the system will not have any adverse effect on the efficiency of the process or the finished PV panel.  In such a rapidly developing market, this level of reliability is vital.

Second, Morgan Technical Ceramics has proven ability to produce consistently high specification components of this kind in large volume, and to be able to react quickly to sudden increases in demand on both sides of the Atlantic.

The manufacture of PV cells using thin film deposition processes is one of the fastest moving and most exciting manufacturing industries of our time.  The global market is growing at a rate of 50% per year and estimates are that growth will continue at this rate until 2010, then increase even more rapidly for a couple years before ‘settling down’ to a steady 25% year on year growth.  Clearly, the race is on, and the big money is there for PV manufacturers who can perfect their processes fast and take the lead.

Proven in other sectors, technical ceramics can make an important contribution to helping this roller-coaster of a developing industry achieve its goals of consistent quality in both the process and the finished product, for better PV cell efficiency in volume productions, and ultimately, parity with other sources of grid energy.

About Morgan Technical Ceramics

Morgan Technical Ceramics (MTC) has comprehensive range of Ceramic materials, from which its products are manufactured. Supplying to a variety of demanding markets, MTC has established an enviable reputation for providing value-added solutions through world-class research and development, innovative design and, perhaps most important of all, application engineering.

Morgan Advanced Ceramics, together with Morgan Electro Ceramics forms Morgan Technical Ceramics, a division of the Morgan Crucible Company plc.   From manufacturing locations in Australia, North America, Europe and Asia, Morgan Technical Ceramics supplies an extensive range of products, including ceramic components, braze alloys, ceramic/metal assemblies and engineered coatings.

For more information on Morgan Technical Ceramics visit www.morgantechnicalceramics.com

Southern California Edison Awards 36 Contracts for Utility-Scale Solar Rooftop Project

Southern California Edison (SCE) awarded 36 contracts to independent power producers for a total of nearly 60 megawatts from photovoltaic solar panels that will produce emission-free energy for SCE customers. The panels will be installed on 31 unused rooftops and five ground-mount sites in SCE’s service territory.

The solar rooftop project, approved by the California Public Utilities Commission in June 2009, calls for a total of 500 megawatts of  solar generating capacity, most of it on otherwise unused large warehouse rooftops. Half of the 500 megawatts will be from independent power producers who respond to SCE’s request for offers under competitive solicitations; the remaining 250 megawatts will be owned and operated by SCE. It is expected that this project will create about 1,200 jobs for Southern Californians.

“These contracts make significant strides toward distributed renewable generation for one of the most innovative solar programs in the country,” said Marc Ulrich, SCE vice president, Renewable and Alternative Power. “We’re working to help California meet its Million Solar Roofs goal and supply even more renewable energy to our customers where and when it’s most needed, without the added time and expense to construct major new transmission facilities.” The contracts awarded today are the first executed under the competitive solicitations for independent power producers.

SCE believes that its solar rooftop project will be a boon for the solar industry and consumers alike, with the resulting cost per unit significantly more cost effective than more common residential photovoltaic installations in California. Eventually, this could help drive down installation costs of photovoltaic generation for everyone. When complete, the solar panels will cover an area totaling 4 square miles on about 250 otherwise unused warehouse roofs. The total power production will rival a utility-scale power plant, enough electricity to serve 325,000 average homes at a point in time. SCE has already installed panels on three rooftop warehouses in California’s Inland Empire that are delivering – or are in line to deliver – electricity to the grid.

SCE is the nation’s leading utility for renewable energy. In 2009, SCE delivered 13.6 billion kilowatt hours of renewable power to its customers, about 17 percent of its total power portfolio.

One Block Off the Grid (1BOG) Launches New Solar Group Purchase Program in Denver

One Block Off the Grid (1BOG), the nation’s largest solar group purchase provider, today announced the launch of a new solar group purchase program in the Denver area. The program offers Denver homeowners a solution that reduces the cost and confusion traditionally associated with the solar buying process.

After an intensive selection process, 1BOG has selected REC Solar as partner to conduct the group’s solar system installations. Homeowners who join the 1BOG community are eligible for online and offline support, information and fixed discounted pricing. With zero down financing options, homeowners can install systems for free and save money from day one.[1]

After a month-long process of vetting local installers, 1BOG selected REC for their excellent group pricing, proven record of successful installations nationwide, premium products and long-term warranties.

“Colorado is one of the country’s leading solar states, so we are excited to bolster local solar adoption with a group program that makes going solar easy and affordable for homeowners,” said Dave Llorens, CEO of 1BOG. “Our 2009 Denver 1BOG campaign with REC Solar was a huge success. We are confident that this one will make a significant dent on the state’s goal of 100,000 solar rooftops by 2020.[2]”

“We are thrilled to have been selected as 1BOG’s partner for the upcoming Denver program,” said Cary Hayes, Senior Regional Manager at REC Solar. “We have worked with 1BOG in several markets around the country and have found the group model to be great for our business and our customers.”

The 1BOG Denver solar program is available now to local homeowners from Fort Collins to Colorado Springs including the cities surrounding the Denver area through October 14, 2010. For more information, details about pricing and products or to sign up, visit the 1BOG Denver homepage at www.SolarDenver.1BOG.org.

About One Block Off the Grid

One Block Off the Grid (1BOG) helps you buy solar panels for your home by researching local solar installers, negotiating group discounts and managing the entire solar buying process from beginning to end—at no cost. 1BOG membership is free and gives homeowners access to exclusive, pre-arranged group discounts, educational tools and advice from an experienced team of solar advisors. Homeowner members are confident that 1BOG’s installation partners have been carefully vetted on products, install practices, long-term stability as a company, as well as a great group discount rate. 1BOG was founded in 2008 in San Francisco, California and has active solar programs in 15 markets across the United States. For more information, visit www.SolarDenver.1BOG.org.

About REC Solar

REC Solar, Inc. specializes in grid-tied solar electric design and installation, offering affordable solar solutions for all residential, commercial, government and utility customers. With a local presence in all major solar markets in the USA and millions of watts installed, REC Solar is committed to lowering the cost of solar power through efficient processes, innovative products and outstanding customer service. REC Solar has installed more residential solar electric systems in the US than any other company. REC Solar is among the nation’s largest solar integrators and currently has over a dozen offices throughout five states (AZ, CA, CO, HI, and OR). For more information, visit www.RECsolar.com.

[1] Financing subject to credit approval
[2] http://www.colorado.gov/cs/Satellite/GovRitter/GOVR/1251575069016

Envision Solar Announces the LifeVillage, a ‘Solar City in a Box’

Envision Solar International, Inc. (OTCBB:EVSI), a leading solar planner, architect and inventor of clean energy systems, announces its newest solar innovation, the LifeVillage, which offers rapid and widespread deployment of safe, system-built, solar-integrated buildings that provide shelter and clean energy in times of crises.

Using the most cutting-edge and efficient solar photovoltaic (PV) panels, Envision Solar’s LifeVillage offers clean energy and durable steel-framed buildings where traditional electrical power generation and the associated transmission and distribution infrastructure cannot go. At 3,500 square feet of habitable area, the LifeVillage has the unique potential to provide a solar powered clinic and/or schoolhouse, residences, purified water, refrigeration and modern communications facilities.

The LifeVillage can also be tailored to an extensive array of applications, depending upon the situation and need. At up to 50kW of generation capacity, the LifeVillage can provide electricity to the surrounding community, offering power for such needs as charging cell phones, solar lanterns, and batteries for hundreds of families.

Integrated with large battery systems, the LifeVillage provides clean and reliable power at any hour of the day or night which is especially beneficial in times of crisis. These solar integrated buildings can be rapidly installed on site in just a few days by unskilled workers.

In an effort to build the best possible product that could be shipped to remote locations, Envision Solar partnered with Nuconsteel to frame each LifeVillage using light gauge steal. Envision Solar’s partnership with Nuconsteel includes access to the Mobile Framing Solution, roll former and light gauge steel technology, all of which offer a distinct and easily-deployable feature for the LifeVillage product.

By assembling the LifeVillage onsite, Envision Solar can cut down on the need for a manufacturing plant, costs, time, and labor significantly. Fabricating onsite also considerably reduces costs associated with shipping, and allows commoditized steel to be sourced in-country, if available.

“In light of the recent earthquake activity and rebuilding efforts in countries like Haiti, it is crucial for under-developed nations to have a quick, reliable energy solution, like the LifeVillage, in times of crises,” said Robert Noble, CEO of Envision Solar. “The LifeVillage is comprised of very simple, moderately-sized buildings that can do very big jobs – like provide purified water, refrigeration, medical facilities and transmission capabilities for cell phones, Internet, radio and television – in a time when recovering communities need help the most.”

For more information on the LifeVillage or other solar parking arrays created by Envision Solar, visit envisionsolar.com

Andes village runs on solar energy

A remote village in the Argentinian Andes mountains runs on solar energy. As a result, Misa Rumi is one of the first villages in the world to switch over to 100 percent sustainable energy.

How to Install Solar Panels

The proper installation of solar panels is one of the most important elements of your solar energy system. Although the sun provides its energy at no charge, the purchase and setup of your panels is a big investment. Whether you mount the panels on your own, or hire a company to do the job
for you, here are some tips for the best installations:

Most homeowners have a limited amount of space in which to place large solar panels. Your roof is a likely location. The solar panels must be installed in an area or areas of your roof that attract the most possible sunshine. There are many web sites that provide the amount of sunlight
received in any area of the world. They allow you to effectively track the sun’s position through the year.

Your solar panels must be placed where they will receive direct sunlight. An ideal spot is one that receives the sun’s rays at noon, typically the time at which your solar panels will operate with the greatest efficiency. Check to see if there are tree branches, satellite dishes or any other objects that might obstruct the path of the sun on your solar panels.

If you are installing solar panels on your roof, you will probably use a flush mount or a roof-ground mount. Flush mounts are typically used for smaller homes. Roof-ground mounts are somewhat more expensive and occupy more space, but they can be adjusted to follow the path of the sun during
the year. Roof mounts are often supported by your roof’s rafters, so use a stud finder to ascertain the position of your rafters.

When you have determined the best location for your panels, draw an outline of their position on your roof. Drill small holes in your roof/rafters before placement of the mounts to allow for easier drilling later. When you have placed the mounts in their exact locations, drill holes in the mounts and secure them with lag bolts. Secure metal rails to the roof. Attach the solar panels. Connect the panels to the electrical inverter with a conduit.

About the Author
Shannon Bell writes for Residentialsolarpanels.org a non commercial blog focused on her Photovoltaic experiences to help people understand how and why they should save energy investing in solar power. She writes on Solar Panels for Homes to help people learn how to start save energy from the scratch and then apply those experience to the next level.

Solar Energy Combats Poverty in Guatemala

A small solar panel lets Rufino Pablo Jeronimo, a Guatemalan farmer, run a tailoring business and keep in touch with his brother in America.

From Time.com