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Good Vibrations Boost Solar Cell Performance

If you feel the energized by the sounds of your favorite band, you are not alone.

Solar cells, it turns out, could have the same reaction. Music vibrations boost the energy output of solar cells that contain nanorods. So says a new study from Queen Mary University of London and Imperial College London.

The high frequency of pop and rock music cause vibrations that increased the energy generation of solar cells with clusters of nanorods. Scientists had already known that straining zinc oxide materials could increase voltage outputs, but the effect had not been tested extensively on solar cell efficiency. Other scientists are looking to use other nano materials such as nanowires to boost the efficiency of solar cells

The British researchers grew billions of zinc oxide nanorods and coated them with an active polymer that could convert sunlight into electricity. They discovered that when the solar cells were exposed to sound, the photovoltaic efficiency increased by as much as 45 percent.

"We thought the sound waves, which produce random fluctuations, would cancel each other out and so didn't expect to see any significant overall effect on the power output," study co-leader James Durrant, professor of photochemistry at Imperial College London, said in a statement.

"The key for us was that not only that the random fluctuations from the sound didn't cancel each other out, but also that some frequencies of sound seemed really to amplify the solar cell output - so that the increase in power was a remarkably big effect considering how little sound energy we put in."

The researchers noted significant improvement in solar cell performance with levels as low as 75 decibels, a sound level similar to busy street traffic. They didn’t go as far as to compare the benefits of one band versus another, but did find that not all musical genres offered the same benefits. 

"We tried playing music instead of dull flat sounds, as this helped us explore the effect of different pitches. The biggest difference we found was when we played pop music rather than classical, which we now realize is because our acoustic solar cells respond best to the higher pitched sounds present in pop music," said Durrant.

Rather than streaming music to solar panels, the research would more likely be used to develop power sources for products that are already exposed to high-frequency acoustic vibrations, such as cars or air conditioners.


Image: iStockphoto

Pre-Paid Microsolar Coming to the Philippines

When Filipinos on the island of Alibijaban need to charge the car batteries they rely on for electricity, they take an eight-minute boat ride to the mainland to recharge the batteries at a local shop.

Alex Hornstein, an MIT-trained engineer, is looking to cut out the boat ride and a lot of the cost. Hornstein is piloting cellular-connected microsolar in Alibijaban, according to a report in Fast Company.

The project, Tiny Pipes, has installed 60-watt solar panels on the roof of about 20 homes in Alibijaban in conjunction with the local utility, Quezelco. The panels come with a connection to a cellular network that controls the power flow from the panel.

For houses with a panel, Tiny Pipes will own the panel and customers rent the panels and pay for the power they use through a cellphone payment. If customers don’t want unlimited charge for the battery, they can set up a prepaid plan for a set amount of energy daily or weekly.

In the United States, the falling price of solar panels and innovative financing methods, primarily solar leasing, have led to a solar boom. There are both similarities and differences in some of the projects being piloted in the developing world, which also rely on some innovative financing schemes and lower hardware costs. 

Generally speaking, remote villages pay a far higher percentage of their income towards power than developed or grid-connected regions. Fast Company reported that the residents of Alibijaban consume about one penny per day of electricity, yet they pay about US $1.50 to $2 per week to charge batteries.

In many poor regions, homes also rely on dirty kerosene lamps to provide light at night. Peru has a pilot to move 126 communities onto solar panels, with a goal of moving 500 000 rural households onto solar power. Other projects, such as SunBlazer, provide solar charging stations on wheels that are operating in some remote villages in Haiti.

Another group, SharedSolar, wants to go one step further and provide solar-powered microgrids that are connected to mobile payments so communities can not only have lights in homes but also power small businesses, such as selling ice. Some solar projects are looking to power other basic services, like clean water in India

Hornstein and his co-founder Shawn Frayne first wanted to make microsolar a reality in remote areas by lowering the cost and extending the lifespan of the hardware. They developed a small machine, Solar Pocket Factory, which makes microsolar photovoltaic panels that can power small electronics. They claim their panels have a 10-year lifespan, five times the life of traditional microsolar.

In their Kickstarter campaign, they also claim their panels can be produced locally for a lower cost than traditional microsolar because it is automated instead of made by hand. As they developed the Solar Pocket Factory, however, they realized that the circuitry they developed to connect the panel to mobile networks was ultimately a more significant breakthrough. Currently, there is not a panel maker that offers a wirelessly controlled panel from the factory.

Hornstein told Fast Company the panels have already withstood two typhoons and expects to expand to another 200 homes on Alibijaban and 1000 homes in another province next year.

“I want to be able to deploy Tiny Pipes at a scale that makes a dent,” said Hornstein in the article. “I'll start feeling like we're reaching that scale when we've hit a million installed panels.”


Photo: Alex Hornstein



Climate Monster Found Lurking in Ocean Depths

An article appearing in the November 1 issue of Science magazine analyzes mid-depth Pacific Ocean temperatures going back 10,000 years and finds a drastic increase in the amount of heat being absorbed and stored by ocean waters during the last 60 years. The study, by authors at Rutgers University, Columbia University's Lamont-Doherty Earth Observatory, and Woods Hole Oceanographic Insitution, reconstructs the history of temperatures in the western Pacific roughly 500-900 meters down through chemical analysis of shells from a species of single-celled organisms called foraminifers (or "forams").

The ratio of magnesium to calcium in the particular foram selected for study and found in ocean sediment cores, Hyalinea balthica, is a precise indicator of ambient temperature at the time the organism lived and died--a standard technique in paleoclimatology.

The three researchers found that the prevailing trend through most of the 10 000 year period was toward cooler temperatures. The cooling rate increased markedly during what's called the Little Ice Age of the European late Middle Ages, only to stop and reverse around the year 1600. After that the rate of Pacific warming was very gradual until about 60 years ago, when it leaped by a factor of 15. "Over a long time, the ocean's interior acts like a capacitor and builds up large (positive and negative) heat anomalies that reflect and, more importantly, affect the global climate," the article says.

There have been times in the ocean records that the three researchers compiled when water temperatures have been considerably higher than they are today, let it be said. The researchers emphasize the rate at which heat can be absorbed or ejected, and the big increase in the uptake rate during recent decades. “We may have underestimated the efficiency of the oceans as a storehouse for heat and energy,” commented Yair Rosenthal of Rutgers, the principal author of the study. “It [that heat storage] may buy us some time—how much time, I don't really know—to come to terms with climate change. But it's not going to stop climate change.”

The thinking is that storage of heat from a warming atmosphere represents a kind of lurking, growing monster that eventually will surface and return to the atmosphere.

Offshore Wind Farms Just Need a Little Stagger to Generate More Power

Neat rows of wind turbines dot seas and oceans across the world. But setting offshore wind turbines in straight lines may limit their power production, according to a new study.

Whether wind farms are on or off shore, there is a tradeoff between getting maximum energy from each individual turbine and packing a greater number of turbines into the space. As each turbine pulls energy from the wind, there is less energy in the downstream wind, which causes array losses for the entire wind farm. (Turbines not only affect their immediate neighbors, they can also affect other arrays miles away.) 

But there may be a simple solution to boost energy production without expanding the boundaries of offshore wind farms. Researchers at the University of Delaware found that staggering turbines in the ocean can improve annual power capacity by 13 to 33 percent. The study appeared in the September issue of Geophysical Research Letters.

“Staggering every other row was amazingly efficient,” Cristina Archer, associate professor of physical ocean science and engineering and geography in University of Delaware's College of Earth, Ocean, and Environment, said in a statement.

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Could Energy Costs Doom Aereo’s TV Streaming Service?

Back before Netflix, Hulu, or even cable television, we all relied on antennas to capture video signals. What's old is new again with Aereo, a TV streaming service that takes the concept of rabbit ears into the 21st century.  

Most of the news about the start-up has centered on its legal battles with incumbent broadcast networks, but according to a report in the Wall St. Journal, it's the company’s hardware that could pose the biggest challenge as it tries to grow.

When you sign up for Aereo, you are assigned a tiny remote antenna and DVR that can record live broadcasts and play them back as streaming video. If you want to record Parks and Recreation on NBC, for instance, that miniature antenna tunes into the right frequency for your location. Even if other people record the same show, the recording for each customer is unique. The signal goes to Aereo’s transcoding equipment that converts the signal to one that can be sent over the Internet. 

The problem is that each antenna uses about five to six watts of power. That’s less than many set-top boxes consume, but the difference is in who pays the energy bill. With cable, the customer, not the cable company, pays for the power consumption of the set-top box. The Wall St. Journal noted that if Aereo were to scale its New York subscription base to about 350 000 customers, the energy cost would be roughly US $2 million per year. New York, which has relatively high energy prices for the United States, is also not its only market. Chet Kanojia, CEO of Aereo, told the Wall St. Journal he hoped to be in nearly 20 markets by the end of the year. 

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Ethiopian Wind Farm Adds Five Percent of Country's Total Electricity Capacity

The 120-megawatt, 84-turbine Ashegoda Wind Farm in Ethiopia opened this week in an arid region about 765 kilometers from the capital, Addis Ababa. The farm was completed in three phases and has actually been generating power for some time now, but was formally inaugurated by the prime minister on Saturday.

Those 120 MW actually represent about 5 percent of Ethiopia's entire installed electricity generating capacity based on the Energy Information Administration's latest data (and a more recent interview with the head of Ethiopia's state-run utility). Scaling up Africa's energy supplies is considered an enormous priority for helping to draw many millions of people out of poverty, and doing so with renewable energy is a no-brainer. Ethiopia alone has an estimated wind power potential of more than 1000 gigawatts (roughly the installed electricity capacity of the United States, from all energy sources). And while only a few projects are in the works in that country, an African Development Bank study from earlier this year reported that about 10.5 gigawatts of wind power currently in the pipeline across the continent.

The big controversy with electricity expansion in Africa relates to another renewable resource: hydroelectric power. Ethiopia already gets 90 percent of its existing electricity from dams, a source obviously fraught with environmental concerns of its own. And the country is moving ahead on a truly massive project, the Grand Ethiopian Renaissance Dam, which, at nearly 6000 MW, will triple the country's total capacity. Egypt has concerns that the dam, which will create a massive reservoir on the Blue Nile, will affect the downstream flow of the Nile to an extent that will affect both its own power supply and cause other water-related issues.

And then there's the ever-present threat of the Grand Inga Dam, a hydroelectric behemoth still under consideration on the Congo River. If built to its full capacity, it would be nearly double the size of the biggest hydroelectric project on the planet, China's Three Gorges Dam, at around 40 000 MW. The latest news on that project has construction for pieces of it beginning in 2015.

The quick-hit potential of such massive electricity development is hard to resist in a continent where 500 million people lack access to power. But it is exciting as well that wind power projects like the one in Ethiopia are starting to take hold, along with the ever-present potential of Saharan solar power. And the money for these projects is starting to flow as well, highlighted by U.S. President Barack Obama's announcement earlier this year of a US $7 billion grant for the Power Africa project; much of that cash will go toward renewable energy projects.

Photo: Kumerra Gemechu/Reuters

California's First-in-Nation Energy Storage Mandate

California has adopted the United States' first energy storage mandate, requiring the state's three major power companies to have electricity storage capacity that can output 1325 megawatts in place by the end of 2020, and 200 MW by the end of next year. The new rule issued by the California Public Utilities Commission (CPUC) will be key to implementation of the state's ambitious renewable portfolio rules, which calls for 33 percent of delivered electricity to come from renewable sources by 2020 and virtually guarantees that California, along with Germany, will remain in the world vanguard of those aggressively building out wind and solar.

[Editor's note: For an explanation of why the mandate is expressed in units of power instead of energy follow this link.]

By common expert consent, wind and solar can only reach their full potential if storage is provided for, as otherwise little-used generating capacity must be held in reserve for the times the wind does not blow and the sun does not shine. California's landmark rule was written by Commissioner Carla Peterman, newly appointed to the CPUC late last year by Governor Jerry Brown.

"This is transformative," Chet Lyons, an energy storage consultant based in Boston, told the San Jose Mercury News, the state's most tech-savvy newspaper. "It's going to have a huge impact on the development of the storage industry, and other state regulators are looking at this as a precedent."

Though the new rule was adopted by the five CPUC commissioners unanimously, two expressed concerns about the strorage mandate's being achieved at reasonable cost to consumers, especially as large pumped storage (hydraulic) facilities do not qualify. There are a wide range of technologies that do qualify, including batteries and flywheels, but costs are generally high. Pike Research has concluded that the United States as a whole could have as much as 14 GW from storage by 2022, but only if storage costs come down to the vicinity of to about $700-$750 per kilowatt-hour.

This post was modified on 7 November for clarification.

Photo: PG&E

China to Invest in Britain's Nuclear Sector

Stranger things have happened in the world of electricity restructuring and deregulation. Five years ago, when the Philippines privatized its national transmission organization, the winning consortium included the State Grid Corporation of China, an organ of the PRC’s communist state. Around that same time, some residents of Brooklyn, N.Y., (this writer among them) were dismayed to discover that they were now buying their natural gas not from a trusted local company but from the operator of a faraway country’s electrical transmission system. The company in question, National Grid of the U.K., was created after Margaret Thatcher’s Britain “unbundled” electricity and sold much of the world on the idea of competition in electric power.

But late last week, Britain’s Chancellor of the Exchequer—the country’s finance minister—announced during a visit to a nuclear power plant in China that the tables have turned. Apparently, Chinese companies will now be welcome to take stakes in nuclear power projects in Britain and eventually even take majority ownership. And according to the New York Times, French power utility Electricité de France (EDF) confirmed today it has has gotten the go-ahead from the U.K. government to build the proposed Hinkley Point C plant in Somerset, UK [illustration, above]. The facility, which will be the first new nuclear power plant to come on line in the country in almost 30 years, is expected to cost £16 billion (about US $26 billion). EDF's partners in the venture include China’s General Nuclear Power Corporation and the China National Nuclear Corporation. The two Chinese entities will together hold a stake totaling between 30 and 40 percent of the project, says the New York Times.

The Financial Times previously reported that the agreement might be the impetus for British companies such as Rolls Royce and International Nuclear Services to invest and participate in Chinese nuclear power projects.

In contrast to some continental European countries like Germany, Austria, and Italy, the British government wishes to stick with nuclear energy and pave the way for a second generation of atomic power plant construction. Its philosophy and approach is essentially similar to that of the current U.S. government’s. But whereas the Obama administration has provided big loan guarantees for two new nuclear projects in the U.S. Southeast, the British government eschews direct subsidies and instead will set a price floor for electricity generated by nuclear power plants.

In all, the official British plan calls for construction of 12 new nuclear power plants by 2030, to replace or supplant the 15 facilities currently operated in the UK by EDF. Britain’s so-called “strike price” for nuclear electricity is expected to be set at £92.5 per megawatthour (roughly 15 U.S. cents per kilowatthour), which is reportedly about double the current average wholesale price in the UK. The strike price approach appears to be a way of protecting the British government and public against cost overruns and delays like those that have plagued EDF’s initial second-generation reactor project at Flamanville, France. If the government were subsidizing Hinkley directly and things started going wrong, it would be tempted to throw good money after bad; the strike price basically tells the industry it can expect so-and-so much return from the project but no more—if something goes badly, that’s the builders’ problem, not ratepayers’.

Illustration: EDF Energy

X-Rays Shed Light on How Li-Ion Batteries Fail

Standard lithium-ion batteries, like the ones in everything from your cell phone to your plug-in electric vehicle, have electrodes that contain intercalation compounds. They are capable of charging and discharging without substantial change in volume or structure, but are limited with regard to energy density. Recently, much work has been done on battery materials with significantly higher energy densities, but these materials typically degrade extremely quickly. Now, for the first time, researchers have found a way to see clearly what is really happening inside the electrodes that leads to that short lifespan, potentially opening a way to engineer our way around the problem. They published a study Thursday in the journal Science.

Using the tomographic x-ray microscopy beam (TOMCAT) at the Swiss Light Source, researchers showed that a tin-oxide electrode expands during charging thanks to an influx of lithium ions. That influx-induced increase in volume turns out to cause irreversible damage by forming cracks within the electrode particles. Martin Ebner, one of the study authors and a PhD student at ETH Zurich, said in a press release that the crack formation is not random; the cracks form at spots where defects already exist. During discharge, the tomography imaging showed that the volume does decrease, but the cracks prevent the electrode from returning to its initial state. The image above shows the tin oxide particles undergoing such structural deformation during charge and discharge.

Specifically, the electrode they measured started life at 50 micrometers, and expanded more than 100 percent to 120 µm during charging; it then shrank back to only 80 µm. The average particle volume fraction, meanwhile, decreased back to a level below where it started, which the authors write implies the polymer binding the particles and the conductive matrix are distorted after just the one charge. "This distortion of the conductive matrix, together with particle fracture, is known to electrically disconnect particles from the rest of the electrode leading to capacity loss," they write.

Importantly, this technique could be repeated using other materials, potentially leading the way to better batteries in general. "Visualizing batteries in operation was essentially impossible until recent advances in x-ray tomography," said senior author Vanessa Wood, also of ETH Zurich. The researchers conclude that "the type of quantitative three-dimensional, and time-resolved images of particle lithiation introduced in this work will provide the experimental data necessary to comprehend the complex electrochemical and mechanical interactions in silicon and related materials."

Photo: Martin Ebner/ETH Zurich

Higher Electricity Costs Raise Alarm Across Europe

British government predictions of sharply increased electricity prices in the next decades are getting renewed attention these days, as the country's opposition leader Ed MIlliband promised to freeze rates if elected prime minister. A March report from the Department of Energy and Climate Change found that with current policies subsidizing green power, electricity costs will rise 33 percent by 2020 and 41 percent by 2030.

In Germany, according to reports issued this month by IHS Inc. in Denver, Colo., green energy developers received $19 billion in subsidies last year, six times the comparable figure for the UK. Germany has pushed low-carbon and renewable energy technology harder than any other European country, with impressive results: Last year it produced 22 percent of its energy from "green" sources, five times as much as twenty years before. But the costs of those green advances have proven to be unsustainably high, from a political point of view.

In Germany's feed-in tariff system, developers of green technologies are guaranteed specific rates of return well into the future, with the costs of those subsidies distributed among all ratepayers, nationwide. Those subsidies are putting a heavy burden on the country's less well-off ratepayers and threatening economic growth, at least as industry sees it. Figuring out how to redistribute those burdens without sacrificing the green policies themselves is a major element in negotiations to form a new government in Germany, which are expected to be protracted.

On Oct. 10, the chief executives of ten energy companies accounting for half of Europe's electricity production called for an end to subsidies for wind and solar power. They also called on Europe to develop a system to reward companies that maintain standby reserves, to compensate for power shortfalls when the wind doesn't blow or the sun doesn't shine. Industry leaders complain that the growing shares of wind and solar have undercut their revenues from baseload coal and nuclear while requiring them to maintain surplus capacity.

The companies are not going to see an end to green subsidies, but some kind of reform is plainly needed. Across Europe, the cost of electricity to homeowners has increased 17 percent in the last four years, and to industry, 21 percent. How to minimize those costs without giving up the objectives of reducing dependence on fossil fuels and cutting greenhouse gas emissions? it's rather like squaring the circle.

In England, the government's "contracts with difference"s program, which is roughly similar to Germany's feed-in tariff system, is not expected to take a hit. Instead, ironically, opposition critics are taking aim at programs encouraging better energy efficiency, according to the Financial Times.




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