Posted Jun 10, 2014, 5:18 PM
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New class of nanoparticle brings cheaper, lighter solar cells outdoors
Posted on June 9, 2014
TORONTO, ON — Think those flat, glassy solar panels on your neighbour’s roof are the pinnacle of solar technology? Think again.
Researchers in the University of Toronto’s Edward S. Rogers Sr. Department of Electrical & Computer Engineering have designed and tested a new class of solar-sensitive nanoparticle that outshines the current state of the art employing this new class of technology.
This new form of solid, stable light-sensitive nanoparticles, called colloidal quantum dots, could lead to cheaper and more flexible solar cells, as well as better gas sensors, infrared lasers, infrared light emitting diodes and more. The work, led by post-doctoral researcher Zhijun Ning and Professor Ted Sargent, was published this week in Nature Materials.
Collecting sunlight using these tiny colloidal quantum dots depends on two types of semiconductors: n-type, which are rich in electrons; and p-type, which are poor in electrons. The problem? When exposed to the air, n-type materials bind to oxygen atoms, give up their electrons, and turn into p-type. Ning and colleagues modelled and demonstrated a new colloidal quantum dot n-type material that does not bind oxygen when exposed to air.
Maintaining stable n- and p-type layers simultaneously not only boosts the efficiency of light absorption, it opens up a world of new optoelectronic devices that capitalize on the best properties of both light and electricity. For the average person, this means more sophisticated weather satellites, remote controllers, satellite communication, or pollution detectors.
“This is a material innovation, that’s the first part, and with this new material we can build new device structures,” said Ning. “Iodide is almost a perfect ligand for these quantum solar cells with both high efficiency and air stability—no one has shown that before.”
Ning’s new hybrid n- and p-type material achieved solar power conversion efficiency up to eight per cent—among the best results reported to date.
But improved performance is just a start for this new quantum-dot-based solar cell architecture. The powerful little dots could be mixed into inks and painted or printed onto thin, flexible surfaces, such as roofing shingles, dramatically lowering the cost and accessibility of solar power for millions of people.
News Release NR-2714
NREL Finds Up to 6-cent per Kilowatt-Hour Extra Value with Concentrated Solar Power
The greater the penetration of renewables in California, the greater the value of CSP with thermal storage capacity
June 9, 2014
Concentrating Solar Power (CSP) projects would add additional value of 5 or 6 cents per kilowatt hour to utility-scale solar energy in California where 33 percent renewables will be mandated in six years, a new report by the Energy Department’s National Renewable Energy Laboratory has found.
The report, “Estimating the Value of Utility-Scale Solar Technologies in California Under a 40% Renewable Portfolio StandardPDF,” finds that CSP, with its ability to store energy for several hours or more, helps maintain firm capacity in the hours when the sun is below the horizon. Compared to variable generation technologies this translates to an increase in value of 5 cents per kilowatt hour under a 33% renewable standard – the mandate for 2020 – or 6 cents per kilowatt hour under a 40% renewable standard. The added value means that at peak demands, CSP can help lower electricity bills.
“CSP adds significant additional value when compared to less flexible generation sources,” NREL CSP Group Manager Mark Mehos, co-author with Jennie Jorgenson and Paul Denholm of the study, said. “As the penetration of renewables rises, so does the relative value of CSP. CSP could also allow greater penetration of PV by making the grid more flexible and reducing curtailment of PV by generating energy after the sun sets. We intend to investigate this in more detail for the remainder of this year.”
While photovoltaic modules capture the sun’s light and turns it into useable electricity, CSP technologies concentrate the sun's energy and capture that energy as heat, which then drives an engine or turbine to produce electrical power. However, the thermal energy CSP generates can be held back for several hours via storage systems such as molten salts – and then used after the sun sets when demand is still high for, say, air conditioning, television, and lighting.
Rooftop solar now 2% of Australia’s total generation
By Giles Parkinson on 10 June 2014
This graph below caught our eye – showing not just the increase in installed capacity of rooftop solar PV in Australia in recent years, but also the increase in individual household system size.
This data – included in the International Energy Agency’s Photovoltaic Systems Program annual report – is taken to the end of 2013, although recent figures show that the accumulated total is now 3.4GW on around 1.4 million homes.
A couple of key points emerge. The first is that the size of residential rooftop solar PV systems increased from 1kW in 2009 to 4kW in 2013. In just the last three years, the size of the system has more than doubled, and the total capacity has risen three-fold.
The report says that around 850MW of solar PV was installed in 2013, mainly small- scale residential systems. Despite increased restrictions on PV power exports to the grid, and low or zero rates now paid for exported power, solar PV system sizes have continued to increase.
The second major point is that rooftop solar PV now accounts for around 5% of electricity capacity and 2% of electricity generation in Australia. As we have seen, this is eating into the earnings of incumbent generators and is one of the main reasons they want support for rooftop solar to be removed.
The report notes that module prices continued to drop from $1.30 per watt in 2012 to around 75c/watt and installed prices for small residential systems dropped from an average of around $3/watt to around $2.50 watt.
“With continued increases in grid electricity prices, PV is a cost effective option for homeowners across Australia and is of increasing interest to the commercial sector.”
Solar Power in Canada: The Secrets Behind Ontario’s Solar Success
Posted on June 9 2014 by Gary Hilson
[Editor’s note: This is the second in our ongoing series of articles on solar power in Canada. The first post covered solar power in British Columbia.]
If there’s a shining beacon of hope for solar power adoption in Canada, it’s the country’s most populous province of Ontario.
The province has been at the forefront of developing policies and incentives to foster the adoption of renewable energy, particularly as an alternative to coal-burning plants, which are being phased out. However, Ontario’s solar success achieved under the provincial Liberal government may be unraveled should the Liberals be unseated by the Conservative party, which favors reinvestment in nuclear facilities, said Jose Etcheverry, co-chair at York University’s Sustainable Energy Initiative. If the Liberals retain power after the June 12 election, he expects Ontario will continue with its integrated energy supply plan, while the province will likely change course toward nuclear if the Conservatives win.
Reinvesting in nuclear does have some barriers to expansion, however, which bodes well for continued support of renewable energy in Ontario even if the Conservative party is in charge. A recent federal court ruling threw out the preliminary approvals for a series of new nuclear power reactors, including Ontario Power Generation’s 2006 plan to extend the Darlington facility with four new reactors. A panel will have to redo an assessment that the court ruling says did not examine the environmental effects of radioactive fuel waste, a Fukushima-type accident or hazardous emissions.
According to the September 2013 report “Renewable Is Doable: Affordable and Flexible Options for Ontario’s Long-Term Energy Plan,” co-authored by the Pembina Institute and Greenpeace, the electricity generated by new reactors is estimated to cost more than 15 cents per kilowatt hour (kWh), while a portfolio of green alternatives could provide the same energy for just over 10 cents per kWh. The report noted the cost of renewable energy technologies, and especially solar power, is dropping dramatically, and this is why jurisdictions across the United States and Europe are canceling planned nuclear projects in favor of renewable alternatives. The continued rapid decline in solar costs makes it increasingly likely that residents and businesses across Ontario will look to produce power themselves.
06/09/2014 03:07 PM
Pakistan Breaks Ground On One of the World’s Largest Solar Parks
Last month, Pakistan began construction on its first major solar park, starting out with one of the largest solar PV projects in the world.
Until now, this land of sun hasn't produced even a kilowatt of solar energy.
Being built in phases, the first 100 megawatts starts generating this year and by 2016, the 400,000-panel project will produce 1 gigawatt (GW) of electricity. Then it will become even larger, eventually covering 15,000 acres and pumping out 1.5 GW.
Smaller solar projects are also being built around Quaid-e-Azam Solar Park, with a road and transmission structure that make it convenient.
Islamabad-based Safe Solar Power, for example, is building a 10 MW project, and about 20 companies are planning projects from 10-50 MW, reports The Express Tribune.
To support solar development, Pakistan is also inaugurating a feed-in tariff for solar PV. Rates vary based on geography, but they are around $0.20 per kilowatt hour, reduced to $0.083 after 10 years. It is limited to PV plants between 1-100 MW.
What is now a barren, parched desert will gleam with solar panels, spurring the economy with it. "You will see a river of panels, residential buildings and offices - it will be a new world," site engineer Muhammad Sajid told The Express Tribune.
Buffett Ready to Double $15 Billion Solar, Wind Bet
By Noah Buhayar and Jim Polson
Jun 9, 2014 9:00 PM PT
Warren Buffett briefly lost track of how many billions of dollars his Berkshire Hathaway Inc. (BRK/A) is spending to build wind and solar power in the U.S. That didn’t stop him from vowing to double the outlay.
Describing the company’s increasing investment in renewable energy at the Edison Electric Institute’s annual convention in Las Vegas yesterday, Buffett had to rely on a deputy, Greg Abel, to remind him just how much they’d committed: $15 billion.
Without missing a beat, Buffett responded: “There’s another $15 billion ready to go, as far as I’m concerned.”
Such bold remarks are common for the Berkshire chairman and chief executive officer. He frequently talks about hunting for “elephant”-size acquisitions and making multibillion-dollar stock purchases.
Still, the comment speaks to the kinds of investments that are increasingly appealing to the billionaire now that his Omaha, Nebraska-based company is the fifth-largest in the world by market value. With dozens of units spinning off cash, Buffett has been allocating funds to regulated, capital-intensive businesses such as railroad BNSF and power companies.
“Buffett has always steered Berkshire toward the future,” said Lawrence Cunningham, a professor at George Washington University and author of the forthcoming book “Berkshire Beyond Buffett.” “Lately, that has meant intensifying the company’s focus on rudimentary, long-lasting businesses.”
While utilities don’t offer the returns of businesses that Buffett, 83, favored earlier in his career, he has said he likes the industry because it provides opportunities for reinvestment and further acquisitions. He bought control of an energy holding company in Iowa in 2000 and helped bankroll its expansion.
The unit, now called Berkshire Hathaway Energy, operates electric grids in the U.K., natural gas pipelines that stretch from the Great Lakes to Texas and electric utilities in states including Oregon and Nevada. Its renewable investments include wind farms in Iowa and Wyoming, as well as solar farms in California and Arizona.
Unlike other utility-holding companies, Berkshire Hathaway Energy retains all of its earnings. That probably will continue, Buffett said yesterday, estimating that the unit could reinvest about $30 billion into its business in the next decade.
“We’re going to keep doing that as far as the eye can see,” he said. “We’ll just keep moving.”
Boosting Solar Cell Efficiency
U Engineers Design New Optical Element to Sort Sunlight
June 10, 2014 – University of Utah electrical engineers have designed a thin layer made of a transparent plastic or glass that sorts and concentrates sunlight to boost the overall efficiency of solar cells by up to 50 percent. This layer, called a polychromat, can be integrated into the cover glass of a solar panel. It could also be used to boost power efficiency in a cellphone or improve low light conditions for a camera.
“Currently, high-efficiency solar cells are very expensive because they have to be carefully manufactured in a complex environment and are only cost-effective for space or defense applications like the Mars Rover,” says Rajesh Menon, a Utah Science Technology and Research (USTAR) assistant professor of electrical and computer engineering at the U. “We have designed a very cheap optical element that can be incorporated into the cover glass of a solar panel that will separate sunlight into various colors.”
Solar cells absorb light from the sun and convert it into electricity. Despite its tremendous potential as a limitless resource of energy, solar power is currently a small fraction of the global energy supply, due to its high cost compared with conventional power sources. In addition, challenges in materials have further limited solar power’s wide reach.
Solar cell performance is directly linked to the efficiency of converting sunlight into electricity. Solar cells operate on the concept that one absorbed bundle of light from the sun, called a photon, generates electrical charge carriers in a layer of material within the solar cell that then becomes electricity.
However, sunlight is made up of different wavelengths of light, ranging from ultraviolet to visible to infrared. Light at different wavelengths is made of photons at different energies. Conventional solar cells only absorb a narrow range of wavelengths very efficiently. The energy at other wavelengths is not absorbed at all or is converted into waste heat rather than electricity. As a result, a solar cell can only convert so many photons into electricity, up to a theoretical limit of about 33.5 percent efficiency (called the Shockley-Queissner limit).
In this new study, Menon and electrical engineering graduate student Peng Wang designed a polychromat. The polychromat was 50 millimeters wide by 10 millimeters long, with 3 micrometer wide grooves to sort incoming light. The polychromat was made using photolithography for this study, but Menon says it can now be made cheaply by creating a mold of the polychromat and then stamping it out like a DVD.
The team placed the polychromat on top of a photovoltaic device, which is a device that generates a voltage when exposed to energy, especially light. The photovoltaic device is made of two absorber layers: gallium indium phosphide to absorb visible light, and gallium arsenide to absorb infrared light. When the University of Utah polychromat was added, the power efficiency increased by 16 percent.
“These colors can be absorbed by appropriate solar cells to increase the efficiency of the overall process without increasing the cost,” says Menon.
The researchers also developed computer simulations of a polychromat placed on a solar cell with eight different absorber layers to show a theoretical efficiency greater than 50 percent.
Last edited by amor de cosmos; Jun 10, 2014 at 6:21 PM.