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Thermophotovoltaic Device Has Potential to Reach Huge Solar Efficiencies

Traditional photovoltaic solar cells have an inherent limit on the efficiency at which they can convert sunlight into energy. This limit—based on the bandgap of the material used and known as the Shockley-Queisser limit—is about 33.7 percent for standard solar cells. It is essentially due to any material's inability to respond to all wavelengths of sunlight; so what if there was a way to change the wavelengths that actually reach the cell to those it converts best? MIT researchers have unveiled the best-yet version of that idea, known as solar thermophotovoltaics. 

These modified solar cells place an absorber/emitter device above the cell itself. Sunlight is absorbed by this layer, it heats up—a lot—and emits light tuned directly to the bandgap of the PV cell beneath it. That means that much more of the energy in the sunlight can turn into electricity. According research in Nature Nanotechnology by graduate student Andrej Lenert and colleagues, this idea offers the benefits associated with both solar thermal power and traditional photovoltaics, and the ability to harness much of sunlight's spectrum and thus achieve extremely high efficiencies.

In theory, these devices could climb all the way toward 80 percent efficiency and beyond, though for now we'll have to settle for a mere 3.2 percent. Still, that is more than triple the efficiency of previous efforts, which have peaked at around 1 percent.

Among the reasons for the huge gap between potential and reality is heat. The new device's absorber-emitter reached a temperature of 962°C; at those temperatures, the devices are difficult to optimize and operate. The 3.2 percent achieved is a result, the investigators say, of the specific materials and design of the absorber-emitter: the outer layer uses an array of multiwalled carbon nanotubes, and the emitter portion is a photonic crystal layer made of silicon and silicon dioxide .

"Our device is planar and compact and could become a viable option for high-performance solar thermophotovoltaic energy conversion," they wrote in the Nature Nanotechnology. And it also has the potential to aid in energy storage, since heat is an easier stored form of energy than electricity. The prototype has reached 3.2 percent, but the group thinks 20 percent, which would put it in range with standard PV modules, is well within reach. In an e-mail, Lenert told me that "efficiencies beyond this level will require improvements in low-bandgap cells, as well as even better control of the thermally-driven spectral conversion process using wavelength and angular selective surfaces." The research center at MIT is pursuing those and other angles to bring this idea into popular use.

China’s Water Scarcity Aggravated by Shrinking Wetlands

China’s wetlands have shrunk by nearly 9 percent in recent years, and the loss could continue if the government doesn't intervene. Officials from China's State Forestry Administration (SFA) told reporters on Monday that 340 000 square kilometers of wetlands, an area the size of the Netherlands, has disappeared since 2003.

The loss of wetlands is not only a blow to the flora and fauna that thrive in the critical habitat, but also to the Chinese population, which already faces increasing competition between agriculture, energy and development.

According to a report in Reuters, the officials said the loss was due to a combination of agricultural needs, large infrastructure projects, and climate change,  In particular, Zhang Yongli, vice director of the SFA, told reporters on Monday that the wetland loss due to infrastructure projects has increased tenfold in the past decade.

Northern China has the most acute water shortages. Nearly half of China’s population lives in the north, but it has only 14 percent of the water. Across the entire country, 85 percent of water is used by agriculture and industry, according to the nonprofit China Water Risk.

About 70 percent the nation's electric power comes from coal-fired generators that require massive amounts of water to operate. And the needs of the energy industry are only expected to increase. World Resources Institute (WRI) reported that China has plans for 363 new coal-fired power plants that will all require water for thermal cooling. Although new coal plants require less water than older plants, they still require more water than natural gas combined cycle plants, solar PV, or wind power. About half of the proposed plants are in areas of high or extremely high water stress, according to WRI.

The story of China’s shrinking wetlands has been ongoing. A 2012 study [PDF] found that China lost 23 percent of its freshwater marshes and 51 percent of its coastal wetlands over the previous 60 years.

One of the issues is adequate enforcement of safeguards for the wetlands. According to Reuters, 9 billion yuan ($1.5 billion) was earmarked for wetland protection between 2005 and 2010, but only 38 percent of those funds were actually allocated. For the period beginning in 2011 and ending in 2015, that figure has risen to 12.9 billion yuan.

China is not without water; it has the world’s fifth largest store of freshwater, according to the Brookings Institution. However, that is not a lot when split amongst more than a billion people—especially taking into consideration that much of the water is in the sparsely populated southwest, rather than the bustling north.

To meet the rising demand, says the Brookings Institution, the Government has plans for a water transfer project from the south to the north—despite various technical and humanitarian challenges. In 2010, the government also drew three red lines to establish “clear and binding limits” on water usage and to increase agricultural efficiency by 60 percent in specific regions. But for wetlands, the Forestry Administration's Zhang told reporters, China still lacks a strong national policy.

"Current regulations and rules have some clauses on wetland protection, but most are in fragments and disorganized, far from meeting the need of our work,” Zhang told ECNS. “Provisions for investigation and supervision of land use, the punishment for lawbreakers and better performance of International conventions are still nearly blank. Thus, a set of practical and binding regulations, especially for wetland protection, is badly needed."

Photo: Sean Gallagher/Getty Images

Obama Administration Wants to Speed Up Hydrogen-Powered Vehicles

The “hydrogen economy” just got a nice push from the Obama administration, which is now partnering with the private sector to facilitate a fresh wave of fuel cells that can be used to power the transportation sector.

The U.S. Department of Energy announced at year end that it would spread a US $7.2 million investment across four states: Georgia, Kansas, Pennsylvania and Tennessee, all to support projects that fuel vehicles and support power systems. The administration says that it is part of its “all-of-the-above” energy strategy.

The winners:

  • The Center for Transportation and the Environment, which will get $3 million. Based in Atlanta, it is developing a fuel cell hybrid electric walk-in delivery van that has a 240 km range before it would need refueling. The project will also retrofit 15 UPS delivery vans with fuel cell hybrid power trains.
  • FedEx Express, which will receive $3 million. Headquartered in Memphis, Tenn., it is building a hydrogen fuel cell delivery truck with a range of up to 240 km on a full tank.
  • Air Products and Chemicals, which will get $900 000. The hydrogen supplier is located in Allentown, Penn. and is constructing a cost-effective tube trailer for hydrogen delivery and storage that can withstand high pressures.
  • Sprint, which will receive $250 000 to use hydrogen fuel cells as backup power for its rooftop cellular sites. In a press release the company says that it will focus on lightweight fuel cell system that can be easily installed without heavy cranes and that can be refueled from the ground, eliminating the need for transporting fuel to the rooftops.

At present, fuel cells are being adopted for materials handling equipment such as forklifts as well as in powering telecommunications infrastructure. As for the transportation sector, Honda, Hyundai and Toyota are all creating small numbers of fuel cell-powered cars that they say will be available by 2015 in Southern California. For its part, Toyota has said that it expects to produce “tens of thousands per year in the 2020s.” Cost for fuel cell vehicles have dropped by 50 percent since 2006 and 30 percent since 2008, according to the U.S. Department of Energy. Meanwhile, fuel cell durability has more doubled since 2005.

The advantages of hydrogen are that it is abundant, renewable and non-polluting. Water vapor is the only byproduct of a fuel cell and hydrogen-fueled vehicles have more twice the range of today’s electric vehicles. But it is difficult to store hydrogen, and it is about 30 percent more expensive to carry the hydrogen via pipelines than to carry natural gas.

The know-how exists but the cost of creating a new hydrogen-powered auto sector is prohibitive. By partnering with the private sector, the Obama administration thinks that it can create some success stories and speed up the process.

Photo: Chuck Burton/AP Photo

Polar Vortex Cripples Power Generation, But Grid Survives

As record cold temperatures plowed across much of the United States earlier this week, no piece of infrastructure was left unaffected. Trains were stalled, flights were cancelled, and schools were closed.

Although most people might not have noticed, the electrical grid was not immune to the effects of the cold snap. PJM Interconnection, the largest U.S. grid operator, hit a new record winter peak use of 141 500 megawatts. The peak energy use came at a time when nearly 20 percent of the generators in PJM's territory were down due to the frigid weather. On Wednesday morning, nearly 40 000 megawatts of PJM’s 190 000-MW installed capacity were offline.

Some of the generation losses were due to natural gas pipeline constraints, which caused gas price spikes across much of the United States. Natural gas is also the most predominant heating fuel in the U.S.; as more utilities build gas generators, they must compete with other natural gas needs during cold spells.

But natural gas availability was only a small part of the picture. Steam-cycle fossil fuel-fired power plants (primarily coal) made up about half of the outages, with diesel generators making up the second largest portion. 

 

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"Rhubarb" Flow Battery Could Bolster Renewables Storage

Rhubarb battery, anyone?

A group at Harvard University has created an aqueous flow battery that uses a quinone, a type of organic molecule that happens to have favorable electrochemical properties. The particular quinone they used is nearly identical to one found in rhubarb.

Flow batteries, which date back more than three decades, replace the solid electrodes of standard batteries with two liquid electrolytes. The liquids, contained in separated tanks, flow through a cell stack, letting ions and electrons move through a porous membrane in order to discharge and recharge the battery. They are considered good candidates for large-scale renewable energy storage because you can scale up the tank size of a flow battery in order to increase the megawatt-hours of storage available without being forced to also scale up the power capacity; with more traditional batteries like lithium-ion, the components come as a package deal, meaning to achieve 50 megawatt-hours of energy storage you also need to pay for 50 megawatts capacity.

That said, flow batteries haven't yet taken the world by storm. The problem, generally, is cost. The most commercially advanced flow battery uses vanadium, an expensive metal; the team at Harvard, led by senior author Michael Aziz, eliminated metals entirely from their version of a flow battery.

“The whole world of electricity storage has been using metal ions in various charge states but there is a limited number that you can put into solution and use to store energy, and none of them can economically store massive amounts of renewable energy,” said another study author, Roy Gordon, also of Harvard, in a press release. “With organic molecules, we introduce a vast new set of possibilities. Some of them will be terrible and some will be really good. With these quinones we have the first ones that look really good.”

The team used a quinone known as 9,10-anthraquinone-2,7-disulfonic acid, or AQDS. According to their paper, to be published tomorrow in Nature, "AQDS undergoes extremely rapid and reversible two-electron two-proton reduction on a glassy carbon electrode in sulfuric acid." Using cheap carbon electrodes, they created a flow battery that essentially matches the performance of existing vanadium flow batteries.

The battery has also run through a hundred or so cycles so far, and the researchers acknowledge that much more testing and tweaking is still required to optimize their design. But in those few cycles, they saw essentially no losses: the galvanic discharge capacity retention, measured as the number of coulombs extracted in one cycle divided by that number in the previous cycle, is above 99 percent. The prototype they made is quite small, but the authors imagine more practically sized versions; a battery with a tank the size of a home heating oil tank, for example, could store a day's worth of solar-generated power and keep a house running through the night. A partnership with fuel cell manufacturer Sustainable Innovations aims at a battery "the size of a horse trailer" within three years, capable of connecting to solar arrays on large commercial buildings, for example.

“I think the chemistry we have right now might be the best that’s out there for stationary storage and quite possibly cheap enough to make it in the marketplace,” Aziz said. “But we have ideas that could lead to huge improvements.”

The group was partially funded by the Advanced Research Projects Agency—Energy (ARPA-E), and the ARPA-E program director praised the result. As we've written here, ARPA-E has focused sharply on energy storage tech, and that seems to yielding some truly promising results. The rhubarb-flow battery—a name I strongly encourage the creators to adopt—is still likely years from commercialization, and of course any number of "breakthrough" technologies don't end up breaking through much of anything, but novel approaches rather than incremental improvements are desperately needed in order to continue the rapid scale-up of renewable energy.

Photo credit: Eliza Grinnell, Harvard School of Engineering and Applied Sciences

All New Generation in Australia Will Be Renewables Through 2020

All new electricity generation in Australia will come from renewable energy through 2020, according to a new report from the Australian Energy Market Operator (AEMO) [PDF].

The bulk of the new power will be wind, with large-scale scale solar photovoltaics comprising about about 13 percent and biomass making up the rest at 3 percent. There are nearly 15 800 megawatts of proposed wind generation projects, according to the AEMO. More than 780 MW of the wind power is expected to come online in 2014-2015.

australia generation

carbon tax has been in effect Down Under since 2012, but the government could repeal it.  Even without the tax, coal power will still be retired as more renewables come online, according to the report. By 2020, there could be 3700 MW less coal-fired generation, about 13 percent of the country's total coal power production.

In the short term, however, AEMO is focused on the challenges of bringing renewables online, which can introduce transmission and distribution issues onto the grid. Intermittent renewable energy can cause instability and can require more ancillary services such as frequency regulation to offset the variable power coming from wind or solar. The AEMO will include transmission connection point forecasts into its electricity forecasts moving forward and is reviewing transmission projects.

The market operator is also developing an independent assessment of the short- to medium-term transmission needs in New South Wales and Tasmania. Although renewables have to be connected to the grid, AEMO also reports that the average utilization of existing transmission lines are down as electricity consumption has dropped, and it will be important not to overbuild. The operator expects most of the investment to be in asset replacement, rather than building entire new networks.

AEMO is planning for far more renewables in the medium term, but coal is still king in Australia and will “continue to dominate over the 25-year outlook,” the report states.

The continuation of coal domination is a far different picture than a report from a non-profit three years ago that found Australia could be completely powered by renewables by 2020. In the long term, gas is likely to gain prominence in Australia’s energy mix. At the end of the 25-year period outlook, AEMO expects the addition of some geothermal resources and more open cycle gas turbines to provide peaking generation.

 

Photo Credit: AEMO, Morne de Klerk/Getty Images

2013 Renewable Energy Recap: A Year of Record Setters and Energy Storage Momentum

Looking back is substantially easier than predicting the future. One year ago, I wrote the following: "This time, though, I am more confident: in 2013 the first offshore turbine in U.S. waters will start spinning. (Probably.)"

I wasn't wrong! (Technically.) In June, a modest 20-meter-tall (65-foot) floating turbine began feeding power to the grid from a harbor in Maine. It wasn't much, and the big offshore wind farms all gunning for first place remain tied up in pre-construction quagmires, but it was a turbine, and it was offshore. Cause for celebration! And more generally, offshore wind does appear poised to actually make a leap; early efforts by Cape Wind in Nantucket Sound suggest that long-cursed project may qualify for a tax credit based on construction starting by the end of this year. And a number of other big wind farms, particularly off the coasts of Rhode Island, New Jersey, and Virginia, may soon get under way. In spite of the positive signs for the industry, though, I have learned my lesson: I will make no promises of spinning offshore turbines in 2014. We'll just have to wait and see.

Back onshore, 2013 was marked by a steady march toward practical, utility-scale energy storage, as well as a series of short-lived record setters in solar and wind generation. One after another, big concentrating solar thermal plants claimed largest-in-the-world status: Abu Dhabi's Shams 1, Arizona's Solana (more on that one in a moment), and finally California's Ivanpah plant. CSP has been considered the most viable way to bet big on solar—and these 100-plus-megawatt plants seem to back that up—but the ever-dropping prices on photovoltaics has slowed some of  CSP's momentum, and perhaps delayed some of the grandest of desert solar plans.

Wind also went big this year, with the United Kingdom's London Array switching on to become the world's biggest offshore wind farm, beating out the Irish Walney site. Big wind plans abound, both on and offshore, though the London Array's full gigawatt capacity may be tough to beat any time soon.

But generating all this clean solar and wind energy is only one aspect of renewable power. Intermittency and dispatchability have long plagued efforts to scale renewables, and 2013 was the year that energy storage really began to take the spotlight. California now has the country's first energy storage mandate, a law requiring storage capacity that can output 1325 megawatts by the end of 2020, and 200 MW by 2015. How the state will achieve this is currently up in the air, but they should have several options: it seemed that the year was full of news on new approaches to storing power.

At the Advanced Research Projects Agency—Energy summit in February, storage projects dominated the exhibit hall floor. Ideas ranged from improved flywheels to iron-flow batteries, but more established approaches are likely to win out for the foreseeable future: improved lithium-ion batteries and old ideas like compressed air energy storage. Several compressed air companies are starting to actually ship units (or will soon start) that can help wind farms max out on their capacity. In the U.K., a largest-yet pilot project will test a huge Li-ion battery installation in Bedfordshire.

And power plants are starting to include storage from the outset as well. That Solana plant in Arizona, built by Abengoa Solar, incorporates molten salt storage that lets the plant produce power for six hours after the sun goes down.

All of this sounds like great news for renewables, and it is. But when facing the magnitude of the climate change challenge, a few gigawatts here or there aren't remotely enough. A report from the International Energy Agency laid out the problem in a nutshell: the overall share of energy attributable to coal, oil, and gas today has not changed one smidge from the late 1980s. Renewables will need to grow at a staggering pace in order to make a significant difference in emissions.

We'll check back next year to see how the effort is going.

Global E-Waste Will Jump 33 Percent in the Next Five Years

All of those cell phones, computers, tablets, toys, and toaster ovens really add up. Not only are consumers gathering more and more electrical and electronic equipment, but we are also tossing much of it in the trash.

The piles of electronic waste, or e-waste, is rising rapidly across the globe, according to a new study by the Solving the E-Waste Problem (StEP) Initiative. The United States and China were responsible for nearly half the world’s total in market volume of e-waste in 2012, which includes anything with a battery or electrical cord.

The figures per capita, however, are far different. China generates about 5.4 kilograms per person, compared to 29.8 per capita in America. The United States has the highest figure of major countries, but it is behind a handful of other places including Singapore, United Arab Emirates, Qatar, Switzerland, Hong Kong and Luxembourg.

The StEP Initiative, which is a partnership of United Nations organizations, industry, governments and non-governmental organizations, wants to help countries better understand their e-waste streams and help build legislation and processes to deal with it. There is a great deal of variability in the effectiveness of e-waste programs between and within countries. 

"Although there is ample information about the negative environmental and health impacts of primitive e-waste recycling methods, the lack of comprehensive data has made it hard to grasp the full magnitude of the problem," Ruediger Kuehr, executive secretary of the StEP Initiative, said in a statement. "We believe that this constantly updated, map-linked database showing e-waste volume by country together with legal texts will help lead to better awareness and policy making at the public and private levels."

The StEP Initiative’s interactive map has details on each country’s e-waste numbers and regional or federal rules about how to dispose of the waste. The timing is critical as global e-waste is expected to rise 33 percent to about 72 million tons per year by 2017.

Another new study [PDF] by MIT and the U.S. National Center for Electronics Recycling took a deeper dive into the e-waste generated in the United States. The researchers found about two-thirds of the used electronics in 2010 were collected, yet only about 8.5 percent of those collected units were exported. The researchers say that is likely a low figure. It also does not account for most of the components that are exported after initial recycling in the United States.

One of the problems with exports is that there is not explicit tracking of the products as they move into secondary markets. Also, the country something is exported to is often not the final resting place. A smartphone may first go to Hong Kong, but then be pulled apart with components going to other countries in the region.

Different technologies also have vastly different paths from the United States. Larger items, such as televisions and monitors, are more likely to end up in Mexico, Venezuela, or Paraguay, while mobile phones are more likely to go to Asia or Latin America. Overall, Latin America and the Caribbean are the most common destinations for products, with Asia following and then Africa being the least common destination for North American e-waste.

The studies help provide a clearer picture of the fate of global e-waste, but much more can be done. “We cannot possibly manage complex, transboundary e-waste flows until we have a better understanding of the quantities involved and the destinations. This research is an important first step in that direction,” Joel Clark, founder of the Materials Systems Laboratory at MIT, said in a statement. The researchers recommend creating trade codes for electronics products to enable better tracking, gaining more access to shipment level trade data, and getting greater reporting of re-export destinations.

 

A Second Big Boost for Modular Nuclear Reactors

Illustration: NuScale
NuScale’s modular reactor can self-cool indefinitely in the event of an outage.

It's long been recognized that nuclear energy will achieve its full potential only if much smaller, inherently safer reactors are developed, so as to be an attractive option in a much wider range of situations. A variety of interesting concepts for compact modular reactors have emerged in the last decade, and now some of them are starting to attract real money. This week, the U.S. Department of Energy announced it would award one such developer, NuScale Power of Corvallis, Oregon, up to US $226 million to support design work.

This was the second such DOE grant. Last November, the Energy Department made its first grant of its $452 million modular reactor program to Babcock & Wilcox, to support its mPower concept. The mPower project is considered to be “a step ahead of NuScale’s because it has a preliminary agreement with a customer, the Tennessee Valley Authority,” according to Matthew Wald of the New York Times.

In the NuScale concept, as described in Spectrum’s round-up on modular reactors two year ago, “the nuclear fuel assemblies sit inside a long core vessel, which in turn is housed in a secondary containment vessel immersed in water. Unlike conventional light-water reactors, which require large pumps to circulate water through the core, the NuScale reactor is based on convection.”

The United States, having given birth to a handful of innovative ideas for small reactors, seems to be well ahead of the rest of the world in this particular technology. But it does not have the field all to itself. Russia's reactor company has developed a small floating nuclear power plant, which appears to be on the threshold of commercial application, most likely in offshore oilfield settings, initially.

Battery Startup Envia Is Accused of Fraud

Early last year the Bay Area startup Envia Systems momentarily got a lot of attention with claims that it had developed a lithium ion battery with three times the energy density and perhaps half the electricity cost of standard lithium ion batteries on the market. (We advised caution at the time) Now Envia stands accused by three former executives of having stolen intellectual property, misrepresenting itself to investors … and of firing them when they started to raise embarrassing questions.

Dana Hall of the San Jose Mercury News reported the rather sensational developments concerning Envia a week ago, noting that the company had received $4 million in funding from ARPA-E and an investment from GM, which hoped to license the technology if it panned out. Subsequently, GigaOm's Katie Fehrenbacher picked up on the allegations about Envia and discussed them in some detail.

This is not the first time Envia has stood accused of misrepresenting itself. Last year the tech business blogger John Petersen pointed out that the company had doctored a chart from Lux Research, to make itself stand out more from competitors. Interestingly, however, Lux itself is reserving judgment about the new charges against Envia.

Lux notes that both Envia and the company it allegedly stole IP from were trying to further develop a technology pioneered at Argonne National Laboratory (ANL) . "Both NanoeXa [the alleged victim company] and Envia had tried to improve upon ANL’s technology, but only Envia successfully patented the work," notes Lux. "The courts will have to determine whether any stolen IP played into these developments, but it’s certainly not a given that NanoeXa’s claims are true."

Of course we are no more able than Lux to pass judgement on the details of the case. However, we stand by our previous warning that any supposedly revolutionary development in storage technology should be treated with extreme caution.

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