Transparent solar materials on windows could gather as much energy as bulkier rooftop solar units, say researchers.

The authors of a new paper argue that widespread use of such highly transparent solar applications, together with the rooftop units, could nearly meet US electricity demand and drastically reduce the use of fossil fuels.

“Highly transparent solar cells represent the wave of the future for new solar applications,” says Richard Lunt, an associate professor of chemical engineering and materials science at Michigan State University. “We analyzed their potential and show that by harvesting only invisible light, these devices can provide a similar electricity-generation potential as rooftop solar while providing additional functionality to enhance the efficiency of buildings, automobiles, and mobile electronics.”

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Using unique design and building methods, researchers have created a prototype for an ultra-thin, curving concrete roof that will also generate solar power.

The self-supporting, doubly curved shell roof has multiple layers: the heating and cooling coils and the insulation are installed over the inner concrete layer. A second, exterior layer of the concrete sandwich structure encloses the roof, onto which builders install thin-film photovoltaic cells.

Philippe Block, a professor of architecture and structures at ETH Zurich, and Arno Schlüter, a professor of architecture and building systems, led the team. They want to put the new lightweight construction to the test and combine it with intelligent and adaptive building systems.

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SolarEngineers working to make solar cells more cost effective ended up finding a method for making sonar-like collision avoidance systems in self-driving cars.

The twin discoveries started, the researchers say, when they began looking for a solution to a well-known problem in the world of solar cells.

Solar cells capture photons from sunlight in order to convert them into electricity. The thicker the layer of silicon in the cell, the more light it can absorb, and the more electricity it can ultimately produce. But the sheer expense of silicon has become a barrier to solar cost-effectiveness.

So the engineers figured out how to create a very thin layer of silicon that could absorb as many photons as a much thicker layer of the costly material. Specifically, rather than laying the silicon flat, they nanotextured the surface of the silicon in a way that created more opportunities for light particles to be absorbed.

Their technique increased photon absorption rates for the nanotextured solar cells compared to traditional thin silicon cells, making more cost-effective use of the material.

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By: Joshua M. Pearce, Michigan Technology University

SolarAs the U.S. military increases its use of drones in surveillance and combat overseas, the danger posed by a threat back at home grows. Many drone flights are piloted by soldiers located in the U.S., even when the drones are flying over Yemen or Iraq or Syria. Those pilots and their control systems depend on the American electricity grid – large, complex, interconnected and very vulnerable to attack.

Without electricity from civilian power plants, the most advanced military in world history could be crippled. The U.S. Department of Energy has begged for new authority to defend against weaknesses in the grid in a nearly 500-page comprehensive study issued in January 2017 warning that it’s only a matter of time before the grid fails, due to disaster or attack. A new study by a team I led reveals the three ways American military bases’ electrical power sources are threatened, and shows how the U.S. military could take advantage of solar power to significantly improve national security.

A triple threat

The first threat to the electricity grid comes from nature. Severe weather disasters resulting in power outages cause between US$25 billion and $70 billion in the U.S. each year – and that’s average years, not those including increasingly frequent major storms, like Hurricanes Harvey and Irma.

The second type of threat is from traditional acts of crime or terrorism, such as bombing or sabotage. For example, a 2013 sniper attack on a Pacific Gas and Electric substation in California disabled 17 transformers supplying power to Silicon Valley. In what the head of the Federal Energy Regulatory Commission called “the most significant incident of domestic terrorism involving the grid that has ever occurred,” the attacker – who may have been an insider – fired about 100 rounds of .30-caliber rifle ammunition into the radiators of 17 electricity transformers over the course of 19 minutes. The electronics overheated and shut down. Fortunately, power company engineers managed to keep the lights on in Silicon Valley by routing power from other sources.

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Renewable grideThe U.S. Department of Energy (DOE) released a report Wednesday night on electricity markets and grid reliability, stating that the decline in coal and nuclear production has not impacted grid reliability, instead the rise in a diverse energy portfolio has increased the grid’s stability.

The study, commissioned by Energy Secretary Rick Perry in April, also states that coal plant closures across the country have been due to market pressure and competition from low-priced natural gas plants, not policy changes that support renewables such as wind and solar.

(MORE: Listen to our interview with former U.S. Energy Secretary and Nobel Laureate Steven Chu.)

“America is also fortunate to have a variety of fuel sources. We need to consider how to use each effectively while recognizing our differences and unique state and regional circumstances,” Perry says in the report’s cover letter. “We must utilize the most effective combination of energy sources with an ‘all of the above’ approach to achieve long-term, reliable American energy security.”

While the report does not state that there is a current concern with grid reliability, it does warn that future problems could arise if coal and nuclear plants continue to close at the current rate. Many environmental advocates cite this as a last-ditch effort for these companies to remain relevant in the energy landscape. However, the report does go on to highlight the role of renewables in developing a diverse energy infrastructure.

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Solar PanelResearchers have created a concentrating photovoltaic (CPV) system with embedded microtracking that is capable of producing 50 percent more energy per day than the standard silicon solar cells.

“Solar cells used to be expensive, but now they’re getting really cheap,” says Chris Giebink, an assistant professor of electrical engineering at Penn State.

“As a result, the solar cell is no longer the dominant cost of the energy it produces. The majority of the cost increasingly lies in everything else—the inverter, installation labor, permitting fees, etc.—all the stuff we used to neglect,” he says.

This changing economic landscape has put a premium on high efficiency. In contrast to silicon solar panels, which currently dominate the market at 15 to 20 percent efficiency, concentrating photovoltaics focus sunlight onto smaller, but much more efficient solar cells like those used on satellites, to enable overall efficiencies of 35 to 40 percent.

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SolarScientists have created a nanoscale light detector that can convert light to energy, combining both a unique fabrication method and light-trapping structures.

In today’s increasingly powerful electronics, tiny materials are a must as manufacturers seek to increase performance without adding bulk. Smaller is also better for optoelectronic devices—like camera sensors or solar cells—which collect light and convert it to electrical energy.

Think, for example, about reducing the size and weight of a series of solar panels, producing a higher-quality photo in low lighting conditions, or even transmitting data more quickly.

However, two major challenges have stood in the way: First, shrinking the size of conventionally used “amorphous” thin-film materials also reduces their quality. And second, when ultrathin materials become too thin, they are almost transparent—and actually lose some ability to gather or absorb light.

The new nanoscale light detector, a single-crystalline germanium nanomembrane photodetector on a nanocavity substrate, could overcome both of these obstacles.

“We’ve created an exceptionally small and extraordinarily powerful device that converts light into energy,” says Qiaoqiang Gan, associate professor of electrical engineering in the University at Buffalo’s School of Engineering and Applied Sciences and one of the paper’s lead authors. “The potential applications are exciting because it could be used to produce everything from more efficient solar panels to more powerful optical fibers.”

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SolarResearchers have developed a new kind of semiconductor alloy capable of capturing the near-infrared light located on the edge of the visible light spectrum.

Easier to manufacture and at least 25 percent less costly than previous formulations, it’s believed to be the world’s most cost-effective material that can capture near-infrared light—and is compatible with the gallium arsenide semiconductors often used in concentrator photovoltaics.

Concentrator photovoltaics gather and focus sunlight onto small, high-efficiency solar cells made of gallium arsenide or germanium semiconductors. They’re on track to achieve efficiency rates of over 50 percent, while conventional flat-panel silicon solar cells top out in the mid-20s.

“Flat-panel silicon is basically maxed out in terms of efficiency,” says Rachel Goldman, a professor of materials science and engineering, as well as physics at the University of Michigan, whose lab developed the alloy. “The cost of silicon isn’t going down and efficiency isn’t going up. Concentrator photovoltaics could power the next generation.”

Varieties of concentrator photovoltaics exist today. They are made of three different semiconductor alloys layered together. Sprayed onto a semiconductor wafer in a process called molecular-beam epitaxy—a bit like spray painting with individual elements—each layer is only a few microns thick. The layers capture different parts of the solar spectrum; light that gets through one layer is captured by the next.

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By: Joshua D. Rhodes, University of Texas at Austin; Michael E. Webber, University of Texas at Austin; Thomas Deetjen, University of Texas at Austin, and Todd Davidson, University of Texas at Austin

SolarU.S. Secretary of Energy Rick Perry in April requested a study to assess the effect of renewable energy policies on nuclear and coal-fired power plants. The Conversation

Some energy analysts responded with confusion, as the subject has been extensively studied by grid operators and the Department of Energy’s own national labs. Others were more critical, saying the intent of the review is to favor the use of nuclear and coal over renewable sources.

So, are wind and solar killing coal and nuclear? Yes, but not by themselves and not for the reasons most people think. Are wind and solar killing grid reliability? No, not where the grid’s technology and regulations have been modernized. In those places, overall grid operation has improved, not worsened.

To understand why, we need to trace the path of electrons from the wall socket back to power generators and the markets and policies that dictate that flow. As energy scholars based in Texas – the national leader in wind – we’ve seen these dynamics play out over the past decade, including when Perry was governor.

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By: Jens Blotevogel, Colorado State University

Solar fieldWithout knowing it, most Americans rely every day on a class of chemicals called per- and polyfluoroalkyl substances, or PFASs. These man-made materials have unique qualities that make them extremely useful. They repel both water and grease, so they are found in food packaging, waterproof fabric, carpets and wall paint. The Conversation

PFASs are also handy when things get heated. Consumers value this property in nonstick frying pans. Government agencies and industry have used them for decades to extinguish fires at airports and fuel storage facilities.

However, widespread use of PFASs has led to extensive contamination of public water systems. Today, these substances can be found in the blood serum of almost all U.S. residents. Exposure to PFASs has been linked to kidney and testicular cancer, as well as developmental, immune, hormonal and other health issues.

But removing them from the environment is not easy. Chemical bonds between fluorine and carbon – the backbone of PFAS molecules – are extremely strong. PFASs can be removed from water by filtering them out, but the used filters have to be disposed of afterwards, and landfilling only transfers the problem to another location. The best solution to the problem is to break down PFASs completely – and on that score, we’re making progress.

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