I joked about the idea of a Martha Stewart designer solar panel a few days ago and now I am eating my words… and lov’n it! While these nano dyed solar panels will not replace the efficency of the standard silicon panels they will offer a unique market for astheitcs and going green!

Here is an excerpt from the ScienceDaily article…

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Screen-printed Solar Cells In Many Colors And Designs, Even Used In Windows
ScienceDaily (Jan. 31, 2008) — Newly designed solar cells can be screen-printed in a wide array of colors and patterns to allow them to be attractively incorporated into building design. The solar cells also can be used on windows, providing shading from glare while generating electricity.

The key component of the new modules is an organic dye which in combination with nanoparticles converts sunlight into electricity. Due to the small size of the nanoparticles, the modules are semi-transparent. This aspect makes them well suited for façade integration. The new solar cells are being developed by members of the Fraunhofer Institute for Solar Energy Systems ISE, who will be presenting their new technology in Tokyo at Nanotech 2008, the world’s largest trade fair for nanotechnology.
The solar module prototype is amber in color. It is possible, however, to produce the modules in other colors, or even to print images or text on the module so that it serves as a decorative element. These design options open up an entirely new range of possible applications. Instead of mounting the solar module on the roof of a building, the electricity producer could be integrated into windows. Used in this way, the new technology not only prohibits direct sunlight from entering the building interior but also generates electricity at the same time.
“We don’t see the dye solar cell as being a rival to the conventional silicon cell,” says Fraunhofer ISE physicist Andreas Hinsch. The module prototypes only achieve an efficiency of four percent, which is not sufficient for rooftop applications in comparison to the performance of crystalline silicon solar cells. On the other hand, dye solar cells have a clear advantage when it comes to façade integration.

Fraunhofer-Gesellschaft press release

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Maybe they could even be made to match the existing color and design of the extisting roof and dispell the astheic concerns from HOAs or Histoic Commisions. Here is a simulation of that idea (not an actual product yet)

Great news for Massachusetts’ residents!

Boston, Massachusetts [RenewableEnergyAccess.com]
Massachusetts Secretary of Energy and Environmental Affairs Ian Bowles has announced that Commonwealth Solar, the state’s new program of rebates to encourage the installation of solar photovoltaic (PV) power is now accepting applications from businesses and homeowners looking to reduce the cost of putting solar panels on their roofs.

“Solar energy is a key component of the clean energy economy we are developing here in Massachusetts, and a rebate is the most efficient, cost-effective way we can make solar power more affordable. Now is the time for businesses and homeowners to find out what Commonwealth Solar has to offer.”
–Ian Bowles, Massachusetts Secretary of Energy and Environmental Affairs

Announced in December, the program, which makes use of existing renewable energy funds, is expected to result in the installation of more than 27 megawatts (MW) of solar power capacity over the next four years. Commonwealth Solar is part of Massachusetts Governor Deval Patrick’s pledge to increase installed solar power from 5 MW today to 250 MW by 2017. This was made in April in connection with Evergreen Solar Inc.’s commitment to locate its first full-scale U.S. manufacturing facility in Massachusetts.
“Commonwealth Solar is open for business, and that’s good news for the economy and the environment,” Bowles said. “Solar energy is a key component of the clean energy economy we are developing here in Massachusetts, and a rebate is the most efficient, cost-effective way we can make solar power more affordable. Now is the time for businesses and homeowners to find out what Commonwealth Solar has to offer.”
Information on how to get a Commonwealth Solar rebate can be found at www.commonwealthsolar.org.

In this interview, San Francisco scientist Dr. Donald Aitken (www.donaldaitkenassociates.com), talks about the inevitability of a future with renewable energy, and insists that we have to stop thinking about how much oil and natural gas we have left, but just start converting to renewables. He makes a very positive and responsible point that the transition to renewables can be done very gradually and economically, using the gift of the current remaining supply of fossil fuels.

“The resources are here in great abundance. The technologies are fully developed now. We are not waiting for new technologies.”

In about 30 minutes he covers almost all kinds of renewables: solar, wind, biomass, tidal, hydrogen, and particularly efficiency. Dr. Donald Aitken trained as a nuclear physicist, but is now a solar architect and former lead scientist at the Union of Concerned of Concerned Scientists.

It is so nice to see this type of work being done for folks without the means to go green.

It means we can all help folks financially and help the planet environmentally at the same time. We all win. What is just as exciting is to know that Citizenre will have 5% of it’s production going toward sustainable projects. As the Citizenre brand becomes a household name and we start doing community sustaining projects like these we will have so much to be thankful for. Just imagine these projects being done on a massive scale all over the country!

Yea America,

In-joy,

Bruce

TreeHuggerTV climbs to the roof to see how Grid Alternatives is helping to bring solar energy to low income communities. Powerful solar arrays bring huge financial savings to new home owners in need, as a single community shows the promise of a cleaner future.

_______________________________________________________________________

And here is another installation by Habitat reported by ABC news…

Habitat For Humanity Goes Solar (video on this link)

January, 26, 2008

By Maureen Naylor

Excerpt from article:

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KFSN — A brand new Habitat for Humanity home was dedicated Saturday to a Fresno family in need. But this donated home will be helping more than just the family for years to come.

The Ayala family of 9 walked into their brand new five bedroom home for the first time Saturday. A welcome move from the three bedroom apartment they were living in.

Augustine Ayala says he’s proud to call this house home. It’s nestled in the Crossroads Community made up of 89 homes all built by Habitat for Humanity.

But the Ayala’s home will get something extra thanks to a $150,000 donation from PG&E ten habitat homes are getting solar panels.

The utility estimates it will save each family about $500 a year in energy costs. Al Galvez, PG&E Public Affairs Manager, says “But not only that- it’s the environmental issue- carbon dioxides will be saved from going into the atmosphere. Big plus for the environment, big plus for the family.”

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Is this blog post accountable for even more CO2 in the atmosphere? Yep.

Two student entrepreneurs decided to do something about it. Now with over 1 million visitors they are having an impact and are looking to take the next step by finding green advertizing dollars to. empowured.net is proud to support them.

In a related article from earth2tech.com

by Stephen Lacey, Staff Writer
Peterborough, New Hampshire [RenewableEnergyAccess.com]
A growing body of opinion research shows that Americans are concerned about how consumption of dirty fossil energies is impacting the environment, threatening national security and hindering long-term economic growth. But when the time comes for action, renewable energy and climate change are not yet true priorities for the everyday consumer.

That may point to one of the keys for marketing renewable energy to the general public: while efficiency and conservation are very important in the entire energy picture, many consumers care more about what the product can give them, not take away.
That’s because many consumers see renewable energy as a major change in lifestyle, not an ordinary product choice, say analysts. Until the industry better addresses concerns about cost, reliability and ease of use, it will simply be easier for Americans not to buy clean energy.
“People will say that they support the environment, that they support clean energy…but when it comes down to real action it has to be easily accessible, and so people don’t want to make complete tradeoffs,” says Ron Pernick, co-founder and principal of Clean Edge, a clean tech research and publishing firm.
In a 2007 analysis of 21 opinion polls on American attitudes toward climate change and renewable energy, American Environics found that there is “widespread agreement that global warming is occurring and that the government should take action to address the problem.” However, when asked specifically about their priorities for Congress and the President, global warming ranked far below issues such as the Iraq War, heath care, education and immigration. Another poll from the Pew Research Center reported climate change ranking 20th out of 23 choices.
The analysis also found that “the public overwhelmingly supports investment into renewable energy technologies,” when the conversation is focused around energy independence, national security and stabilizing energy prices over the long-term.
This research suggests that Americans should be willing to purchase renewable energy. But while clean power offerings from utilities have expanded and sales of solar photovoltaics (PV) and small wind systems are increasing, the numbers aren’t matching up with what people are saying in surveys.
“We looked that this issue and asked, ‘why are they lying to us?’” says Brian Keane, President of SmartPower, a non-profit marketing firm for the renewable energy industry. “Why are people telling us that they support clean energy and then not buying it?”
Of course, upfront cost is a major issue, especially when purchasing on-site generation technologies like PV. However, the broader issue, says Keane, is that the industry hasn’t quite gotten it’s sales pitch down. Because consumers are faced with confusing language, hear contradictory statements about reliability and have fears about making drastic lifestyle changes, they find it much easier to do nothing.
SmartPower has been studying this issue for many years and has undertaken a nation-wide media campaign that addresses consumer confusion in the marketplace. The pitch: selling clean energy not on its environmental attributes, but on it’s ability to be a reliable part of the nation’s energy mix, which in turn will create a more secure, prosperous nation. The organization also provides important information on how consumers can purchase clean energy from their utility.
“We believe that people…will want to buy clean energy if they understand what it is, how they can get it and where they can get it,” says Keane.
Clean Edge’s Pernick agrees with SmartPower’s approach. In his book, The Clean Tech Revolution, he and co-author Clint Wilder lay out five factors necessary for mainstreaming renewable energy. One is Don’t Lead with the Environment.
“That’s something that all clean energy marketers should look at,” says Pernick. “Not just playing on the environmental and green heart strings, but what are all the other benefits? Does it give me energy security? Does it make my life easier? Lead with all the other value propositions.”
An October 2006 poll from Rassmussen Reports found that 73 percent of Americans strongly favor developing new sources of energy, with only 21 percent of Americans saying they favored conservation efforts. That may point to one of the keys for marketing renewable energy to the general public: while efficiency and conservation are very important in the entire energy picture, many consumers care more about what the product can give them, not take away.
Consumers are very reluctant to make an extra effort to purchase a product that they already get easily, says Keane. SmartPower’s research shows that a large number of people think purchasing renewable energy means they must live off the grid and completely change their lifestyle.
“In the mind of the consumer, when they think of clean energy they never equate it to actually being grid connected. They always assume that we are telling them to buy 100 percent solar power and put panels on your house and that’s how you’re going to live,” says Keane.
Now the big challenge for organizations like SmartPower is making sure that Americans understand that buying clean energy is easy, reliable and does not mean sacrificing lifestyle. Only when those issues are addressed, says Keane, will the environmental attributes of clean energy really start to matter to the consumer.
“There continues to be huge confusion about clean energy by, really, the majority of Americans. We need to actively work to clear up the misconceptions about this product. When that happens — when you properly educate people about the buying process and the product — it will really take off. We’re already seeing it in the [media] markets SmartPower serves.”

article

Tidal Energy has a huge potential to provide long term, secure, low cost, supply of electricity. Especially for island coastal communities like Nantucket Island, Massachusetts. The local community has been split on it’s support of a wind farm in Nantucket Sound but appears to be very supportive of a Tidal Energy generation system.

The proposed installation would provide around 4.2 times the amount of energy flowing into Nantucket right now…very exciting!

Below is an article from one of the local papers as well as a number of interesting links and information about the different forms of tidal energy generation. While tidal energy has not has as much attention as solar and wind it has the potential to provide a very substantial piece of the renewable energy solution for energy independence and weaning ourselves from the addiction to fossil fuels.

In-joy,
Bruce

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Nantucket Island’s Planning and Economic Development Commission supports tidal energy project
Nantucket Independent - Peter Brace January 2008

Nantucket’s Planning & Economic Development Commission voted unanimously last week to support Edgartown’s proposed tidal generation project between Muskeget and Martha’s Vineyard.
At its Jan. 3 meeting, the NP&EDC endorsed the permit issued to Edgartown by the Federal Energy Regulatory Commission (FERC) to install tidal generators in Muskeget Channel. Commissioners also supported the University of Massachusetts at Dartmouth’s request for a $5 million grant from the Renewable Energy Trust of the Massachusetts Technology Collaborative to establish a Federal Marine Renewable Energy Center for the East Coast.
Such a center could provide technical assistance to Edgartown for tidal generation projects and all other renewable energy projects proposed for the Outer Continental Shelf, said Planning Director Andrew Vorce.
Generically known as in-stream energy conversion devices, tidal generators are set in channels where tidal currents, ideally, turn the rotors of the generators at three to eight knots or 2.6 to 6.9 miles per hour. These underwater turbines are typically unidirectional, meaning that their rotors can change direction with the tides. They come in a variety of configurations, including short tubes, double-ended funnels, or open rotors anchored to the bottom. Generators in a specific location would be connected to a nearby power grid with submarine cables.
The NP&EDC also voted unanimously at the meeting to direct Blue Wave Strategies of Boston, Mass. to xapply to the Minerals Management Service for a lease of one square mile of ocean south of Tuckernuck Island for the installation of a data collection tower to be used to determine the viability of building an offshore wind farm.
Both actions are in line with the Planning Commission’s and Nantucket’s belief that alternative energy installations are good for the Cape and islands, but not for Nantucket Sound.
“We’re working together with them [Edgartown and UMass Dartmouth],” said Vorce. “The whole idea is this is a collaboration with the two islands on the waters between the two islands. They’re applying to FERC and UMass is applying for a grant.
“Out of that funding would be funding for Edgartown and, hopefully, Nantucket to investigate renewable energy alternatives in this area.”
The grant money referred to would go toward such explorations, but would not cover the costs of tidal generator and wind turbine installations.
A data collection tower for potential wind turbines south of Tuckernuck, said Vorce, could start collecting data on wind speed, gusts, direction, wave heights, barometric pressure and air temperature in about three years.
At its July 2007 meeting, the commission had endorsed a plan for Nantucket, Edgartown and the University of Massachusetts at Dartmouth to jointly file an application with the Federal Energy Regulatory Commission to build tidal generators between the two islands. But the Planning Commission is now focusing on wind turbine-generated power south of Tuckernuck, one of several alternative sites suggested for Cape Wind Associates’ 130-turbine installation that is now proposed for Horseshoe Shoal in Nantucket Sound.
Edgartown filed its preliminary permit application on July 30 with FERC and has since received its permit. Edgartown’s reasoning for doing such a project with UMass-Dartmouth is to secure renewable energy for Edgartown at the cheapest possible rate, rather than one set by one of two private companies - Natural Currents Energy Services and the Oceana Energy Company - already surveying island waters for possible tidal energy generation sites.
Natural Currents Energy Services, LLC, a Highland, N.Y.-based firm is proposing to generate three gigawatts of power by installing tidal energy generators in Nantucket Sound between Nantucket and Chappaquiddick on Martha’s Vineyard. That is about 4.2 times the amount of electricity - around 70 megawatts - flowing to Nantucket right now.
Calling it the Nantucket Tidal Energy Plant, Natural Currents Energy Services is in the preliminary permitting phase of the project that - under ideal review and permitting conditions - would have its tidal generators online by 2011.
The Oceana Energy Company of Washington, D.C. received a preliminary permit from the FERC last summer to test the waters of Vineyard Sound in an area bounded by the southwest end of Naushon Island and extending northeast on both sides of Lucas Shoal and Middle Ground, according to Oceana’s preliminary permit filing with FERC.
Oceana, which is going to be building its own underwater turbines, told the FERC it would install 50 to 100 units with propeller diameters of around 35 feet in water as deep as 75 feet.
Theoretically, Oceana would like to generate 25 to 100 megawatts, with each generator producing 500 kilowatts to two megawatts of electricity, enough
power for about 750 homes.

Article
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Oceana Energy Company

Marine Current Turbines

News coverage of the worlds most efficient water current turbine, the Davidson-Hill Venturi Turbine

Gavin Harper of ECOGEEK.com Discusses Tidal Power with attendees of the All Energy Conference in Aberdeen Scotland

New Guidelines for Hawaiian Ocean Energy Projects
Nov.2007 -RenewableEnergyAccess.com

OTEC News -Clean Energy, Water and Food

UK energy and power experts meet to discuss the latest developments and initiatives in wave and tidal power technology across Britain.

Oregon hopes to catch energy wave.
-The Portland Tribune- Anne Distefano, July 24, 2007
“The push to make Oregon a center for ocean wave energy is rapidly gaining.
3 Ways of Using the Tidal Power of the Ocean
There are three basic ways to tap the ocean for its energy. We can use the ocean’s waves, we can use the ocean’s high and low tides, or we can use temperature differences in the water.

1 Wave Energy
Kinetic energy (movement) exists in the moving waves of the ocean. That energy can be used to power a turbine. In this simple example, (illustrated to the right) the wave rises into a chamber. The rising water forces the air out of the chamber. The moving air spins a turbine which can turn a generator.
When the wave goes down, air flows through the turbine and back into the chamber through doors that are normally closed.
This is only one type of wave-energy system. Others actually use the up and down motion of the wave to power a piston that moves up and down inside a cylinder. That piston can also turn a generator.
Most wave-energy systems are very small. But, they can be used to power a warning buoy or a small light house.

2 Tidal Energy
Another form of ocean energy is called tidal energy. When tides comes into the shore, they can be trapped in reservoirs behind dams. Then when the tide drops, the water behind the dam can be let out just like in a regular hydroelectric power plant.
In order for this to work well, you need large increases in tides. An increase of at least 16 feet between low tide to high tide is needed. There are only a few places where this tide change occurs around the earth. Some power plants are already operating using this idea. One plant in France makes enough energy from tides to power 240,000 homes.

3 Ocean Thermal Energy Conversion or OTEC
Energy
This is an energy technology that converts solar radiation to electric power. OTEC systems use the ocean’s natural thermal gradient—the fact that the ocean’s layers of water have different temperatures—to drive a power-producing cycle. As long as the temperature between the warm surface water and the cold deep water differs by about 20°C (36°F), an OTEC system can produce a significant amount of power, with little impact on the surrounding environment. The oceans are thus a vast renewable resource, with the potential to help us produce billions of watts of electric power. This potential is estimated to be about 10 13 watts of baseload power generation, according to some experts.
The distinctive feature of OTEC energy systems is that the end products include not only energy in the form of electricity, but several other synergistic products.
Fresh Water
The first by-product is fresh water. A small 1 MW OTEC is capable of producing some 4,500 cubic meters of fresh water per day, enough to supply a population of 20,000 with fresh water. OTEC-produced fresh water compares very favourably with standard desalination plants, in terms of both quality and production costs.
Food
A further by-product is nutrient rich cold water from the deep ocean. The cold “waste” water from the OTEC is utilised in two ways. Primarily the cold water is discharged into large contained ponds, near shore or on land, where the water can be used for multi-species mariculture producing harvest yields which far surpass naturally occurring cold water upwelling zones, just like agriculture on land.
Cooling
The cold water is also available as chilled water for cooling greenhouses, such as the Seawater Greenhouse or for cold bed agriculture. The cold water can also be used for air conditioning systems or more importantly for refrigeration systems, most likely linked with creating cold storage facilities for preserving food. When the cold water has been used it is released to the deep ocean.

by Karim Yergaliyev
Solar power might be the most up-and-coming renewable energy source, but one of the biggest drawbacks to solar power plants is their inability to generate electricity at night or during cloudy days. But now, a new venture called SolarReserve hopes to change all that using salt! Their program would save and store captured solar energy in molten salt, the new solar plant will produce up to 500 megawatts of peak power — comparable to what a regular coal power plant can produce, only with no greenhouse gas emissions.

solar power, solar power, salt, solare technology, solar innovations, solar power innovation, new solar power technology, solar salt

Unlike other solar power plants, SolarReserve’s will be able to produce electricity at night or in inclement weather. You can see the commercial potential here if you note that just one megawatt is enough power roughly 1,000 U.S. households. The company hopes to build 10 plants over the next 10 to 15 years.

The concept behind new concentrated solar power plant is very similar to Seville’s solar power tower where hundreds of solar panels reflect the sun’s light to heat the water inside the tower, which later evaporates into steam that passes through series of turbines to generate electricity. However, instead of tower that holds water, SolarReserve’s holding tank will have molten salt. Huge array of mirrors will reflect light onto the tank; heated 1,000 degrees Fahrenheit liquid is then pumped into a steam generator that will turn a turbine to make electricity.

“Due to the unique ability of the product to store the energy it captures, this system will function like a conventional hydroelectric power plant, but with several advantages,” says Lee Bailey, managing director of US Renewables Group, SolarReserve parent company. “This product is more predictable than water reserves, the supply is free and inexhaustible, and the environmental impact is essentially zero.”

SolarReserve says that their use of molten salt, a mixture of sodium and potassium nitrate, instead of water or oil, allows the heat to be stored for use when sun is not present. The National Solar Thermal Test Facility conducted several studies and concluded that molten salt is the most efficient fluid when it comes to transporting sun’s heat. The study states, “molten salt is used in solar power tower systems because it is liquid at atmosphere pressure, it provides an efficient, low-cost medium in which to store thermal energy, its operating temperatures are compatible with today’s high-pressure and high-temperature steam turbines, and it is non-flammable and nontoxic.”

+ SolarReserve (US Renewables Group, parent company)
full article at: inhabitat.com

Scientific American Magazine - January, 2008
By 2050 solar power could end U.S. dependence on foreign oil and slash greenhouse gas emissions
By Ken Zweibel, James Mason and Vasilis Fthenakis

High prices for gasoline and home heating oil are here to stay. The U.S. is at war in the Middle East at least in part to protect its foreign oil interests. And as China, India and other nations rapidly increase their demand for fossil fuels, future fighting over energy looms large. In the meantime, power plants that burn coal, oil and natural gas, as well as vehicles everywhere, continue to pour millions of tons of pollutants and greenhouse gases into the atmosphere annually, threatening the planet.
Well-meaning scientists, engineers, economists and politicians have proposed various steps that could slightly reduce fossil-fuel use and emissions. These steps are not enough. The U.S. needs a bold plan to free itself from fossil fuels. Our analysis convinces us that a massive switch to solar power is the logical answer.
Solar energy’s potential is off the chart. The energy in sunlight striking the earth for 40 minutes is equivalent to global energy consumption for a year. The U.S. is lucky to be endowed with a vast resource; at least 250,000 square miles of land in the Southwest alone are suitable for constructing solar power plants, and that land receives more than 4,500 quadrillion British thermal units (Btu) of solar radiation a year. Converting only 2.5 percent of that radiation into electricity would match the nation’s total energy consumption in 2006.
To convert the country to solar power, huge tracts of land would have to be covered with photovoltaic panels and solar heating troughs. A direct-current (DC) transmission backbone would also have to be erected to send that energy efficiently across the nation.
The technology is ready. On the following pages we present a grand plan that could provide 69 percent of the U.S.’s electricity and 35 percent of its total energy (which includes transportation) with solar power by 2050. We project that this energy could be sold to consumers at rates equivalent to today’s rates for conventional power sources, about five cents per kilowatt-hour (kWh). If wind, biomass and geothermal sources were also developed, renewable energy could provide 100 percent of the nation’s electricity and 90 percent of its energy by 2100.

The federal government would have to invest more than $400 billion over the next 40 years to complete the 2050 plan. That investment is substantial, but the payoff is greater. Solar plants consume little or no fuel, saving billions of dollars year after year. The infrastructure would displace 300 large coal-fired power plants and 300 more large natural gas plants and all the fuels they consume. The plan would effectively eliminate all imported oil, fundamentally cutting U.S. trade deficits and easing political tension in the Middle East and elsewhere. Because solar technologies are almost pollution-free, the plan would also reduce greenhouse gas emissions from power plants by 1.7 billion tons a year, and another 1.9 billion tons from gasoline vehicles would be displaced by plug-in hybrids refueled by the solar power grid. In 2050 U.S. carbon dioxide emissions would be 62 percent below 2005 levels, putting a major brake on global warming.
Photovoltaic Farms
In the past few years the cost to produce photovoltaic cells and modules has dropped significantly, opening the way for large-scale deployment. Various cell types exist, but the least expen?sive modules today are thin films made of cadmium telluride. To provide electricity at six cents per kWh by 2020, cadmium telluride modules would have to convert electricity with 14 percent efficiency, and systems would have to be installed at $1.20 per watt of capacity. Current modules have 10 percent efficiency and an installed system cost of about $4 per watt. Progress is clearly needed, but the technology is advancing quickly; commercial efficiencies have risen from 9 to 10 percent in the past 12 months. It is worth noting, too, that as modules improve, rooftop photovoltaics will become more cost-competitive for homeowners, reducing daytime electricity demand.

article continues here…

January 17, 2008

In the race to make solar cells cheaper and more efficient, many researchers and start-up companies are betting on new designs that exploit nanostructures — materials engineered on the scale of a billionth of a meter. Using nanotechnology, researchers can experiment with and control how a material generates, captures, transports, and stores free electrons — properties that are important for the conversion of sunlight into electricity.

“We initially thought that the best we might do is get results as good as the sum of the two, and maybe if we didn’t make this right, we’d get something worse. But surprisingly, these materials were much better.”

–Jin Zhang, Professor of Chemistry at the University of California, Santa Cruz

Two nanotech methods for engineering solar cell materials have shown particular promise. One uses thin films of metal oxide nanoparticles, such as titanium dioxide, doped with other elements, such as nitrogen. Another strategy employs quantum dots — nanosize crystals — that strongly absorb visible light. These tiny semiconductors inject electrons into a metal oxide film, or “sensitize” it, to increase solar energy conversion. Both doping and quantum dot sensitization extend the visible light absorption of the metal oxide materials.

Combining these two approaches appears to yield better solar cell materials than either one alone does, according to Jin Zhang, professor of chemistry at the University of California, Santa Cruz. Zhang led a team of researchers from California, Mexico, and China that created a thin film doped with nitrogen and sensitized with quantum dots. When tested, the new nanocomposite material performed better than predicted — as if the functioning of the whole material was greater than the sum of its two individual components.

“We have discovered a new strategy that could be very useful for enhancing the photo response and conversion efficiency of solar cells based on nanomaterials,” said Zhang. “We initially thought that the best we might do is get results as good as the sum of the two, and maybe if we didn’t make this right, we’d get something worse. But surprisingly, these materials were much better.”

Zhang’s team characterized the new nanocomposite material using a broad range of tools, including atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman spectroscopy and photoelectrochemistry techniques. They prepared films with thicknesses between 150 and 1100 nanometers, with titanium dioxide particles that had an average size of 100 nanometers. They doped the titanium dioxide lattice with nitrogen atoms. To this thin film, they chemically linked quantum dots made of cadmium selenide for sensitization.

The resulting hybrid material offered a combination of advantages. Nitrogen doping allowed the material to absorb a broad range of light energy, including energy from the visible region of the electromagnetic spectrum. The quantum dots also enhanced visible light absorption and boosted the photocurrent and power conversion of the material.

When compared with materials that were just doped with nitrogen or just embedded with cadmium selenide quantum dots, the nanocomposite showed higher performance, as measured by the “incident photon to current conversion efficiency (IPCE),” the team reported. The nanocomposite’s IPCE was as much as three times greater than the sum of the IPCEs for the two other materials, Zhang said.

“We think what’s happening is that it’s easier for the charge to hop around in the material,” he explained. “That can only happen if you have both the quantum dot sensitizing and the nitrogen doping at the same time.”

The nanocomposite material could be used not only to enhance solar cells, but also to serve as part of other energy technologies. One of Zhang’s long-term goals is to marry a highly efficient solar cell with a state-of-the-art photoelectrochemical cell. Such a device could, in theory, use energy generated from sunlight to split water and produce hydrogen fuel (see earlier press release). The nanocomposite material could also potentially be useful in devices for converting carbon dioxide into hydrocarbon fuels, such as methane.

The new strategy for engineering solar cell materials offers a promising path for Zhang’s lab to explore for years to come.

“I’m very excited because this work is preliminary and there’s a lot of optimizing we can do now,” Zhang noted. “We have three materials — or three parameters — that we can play with to make the energy levels just right.”

In essence, the team has been trying to manipulate materials so that when sunlight strikes them, the free electrons generated can easily move from one energy level to another — or jump across the different materials — and be efficiently converted to electricity.

“What we’re doing is essentially ‘band-gap engineering.’ We’re manipulating the energy levels of the nanocomposite material so the electrons can work more efficiently for electricity generation,” Zhang said. “If our model is correct, we’re making a good case for this kind of strategy.”

Sources of funding for this research included the U.S. Department of Energy, the National Science Foundation of China, and the University of California Institute for Mexico and the United States (UC-MEXUS).

artile at: www.renewableenergyaccess.com