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Compressed Air Energy Storage Makes a Comeback

Only a handful of compressed-air energy storage (CAES) plants have been installed since the 1970s. This week, SustainX is bringing the technology back to the U.S. electricity grid, albeit in a vastly different form.

The startup, based in Seabrook, New Hampshire, began operating a full-scale demonstration system that stores energy as compressed air in pipes and supplies 1.65 megawatts of power. The company will use the machine to gather data on performance and and to show off the technology to potential investors and customers. The project was funded by $5.4 million from the Department of Energy and at least that much from SustainX, according to a representative.

Conventional compressed-air energy storage uses a compressor to pressurize air and pump it into underground geological formations. The first two plants of this type put into operation—one in McIntosh, Alabama in 1991, and the other in Huntorf, Germany in 1978—use salt caverns as storage tanks, pumping compressed air in at night, when energy demand is lowest. During the day, the air is released, heated with natural gas, and forced through a turbine to generate power. The appeal of this technology is that it’s relatively low cost and can store many kilowatt-hours of energy.

SustainX takes a different tack: it uses compressed air as the energy storage medium, but holds the air in large pipes, the same used in natural gas pipelines. That means utilities or even commercial customers could place a storage device in a range of industrial locations, rather than only where there’s an underground formation available.

At the base of SustainX’s machine, called the S165, is the bottom half of a diesel engine normally used to propel ships. To store energy, a permanent magnet motor-generator turns the engine's crankshaft, driving six pistons located above it. The pistons, each of which is taller than a full-grown man, compress a combination of air and foamy water, which is then pumped into storage tanks. When power is needed, the air is released, driving the pistons and turning the generator to create a current.

A key difference between SustainX's technique and conventional CAES technology is that the compression and expansion of air are done at near-constant temperature and the process doesn’t require natural gas. And unlike conventional batteries, this system can vary the amount of energy independent of the power output. In other words, you can expand the amount of energy it stores simply by installing bigger pipes. That's different from a battery designed to deliver, say, 1 megawatt for 2 hours. If you wanted four hours of storage, you'd have to buy another battery--a more expensive approach, the company says. 

The target market for these systems is renewable energy project developers looking to firm up the output of wind and solar farms or to store excess wind energy at night for sale during peak times. Utilities could elect to install air energy storage instead of making upgrades to transmission and distribution lines to meet growing demand. SustainX expects that a typical configuration will offer between 10 and 20 megawatts and store four to six hours of energy, according to a representative.

The first customers are likely to be in Asia, in places where the price of natural gas prices is higher than it is in the U.S., electricity demand is growing rapidly, and there are problems integrating renewable energy, says Richard Brody, the vice president of business development. He expects the first systems to be installed next year in China. At volume, he projects price of energy can get to $500 per kilowatt-hour and the system can operate for 20 years.

There are at least two other compressed-air energy startups looking to get a toehold in the market for long-duration energy storage. Berkeley, California-based startup LightSail Energy is building a device designed to store compressed air in steel tanks, while General Compression of Newton, Mass., has a compressor operated by a wind turbine that stores air in underground caverns. Late last year, General Compression opened a two-megawatt CAES facility connected to a wind turbine in Gaines, Texas.

All of these companies hope to demonstrate that their technologies cost less and last longer than a host of battery alternatives. With few commercial systems for bulk storage currently online, it’s hard to evaluate which technologies will win out. But many companies are betting they can achieve a technical breakthrough that will make multi-hour energy storage cost-effective. 

Image: SustainX

Updated 17 September 2013: Changed to reflect the opening of a CAES plant last year. 

Alleged German EV Spies Arrested in l'Affair Autolib

Intrigue on the streets of Paris. Two German automakers stand accused of industrial espionage after France's digital crimes squad and counter-espionage agents scooped up two German nationals jacking into a French electric vehicle (EV) network. This isn't the latest international crime thriller, and Matt Damon will not be making an appearance. This is la vraie vie in which European automakers, entrepreneurs, and governments step up investment in electric mobility, and rising stakes beget rising tensions.

Last week France's Paris-based IT crimes squad—the brigade d'enquêtes sur les fraudes aux technologies de l'information—arrested two German men who claimed to be working for automaker BMW, according to reporting by French daily Le Figaro. The pair, employees of Aachen-based engineering firm P3-Group, were caught tampering with charging stations belonging to Autolib, the Paris-based EV car sharing program. France's counter-espionage organization, the DCRI, is also on the case, adds Le Figaro.

This week, Bolloré, the French industrial firm that created and operates Autolib, filed suit in Paris charging P3-Group with industrial espionage. Its complaint claims that the P3-Group technicians plugged unauthorized electronic equipment into Autolib charging stations.

Autolib provides swipe-and-go access to 1800 small electric cars at any of 4000 charging stations in the Paris metro area. As we report in the current issue of IEEE Spectrum, Autolib is easy to use, affordable, and popular, and the concept is spreading. Paris mayor Bertrand Delanoë yesterday tweeted the announcement that Autolib had registered its 100 000th subscriber since its December 2011 launch. 

Bolloré aims to push the car sharing program worldwide. Today it announced a partnership with French automaker Renault to accelerate the international rollout based on the systems Bolloré developed for Autolib. Most notable are the innovative lithium metal polymer batteries that power its EVs and the proprietary tracking and scheduling systems that coordinate the car sharing network.

German automakers recently stepped up investment in EVs, after relying almost exclusively on diesel engines to meet demand for higher fuel efficiency. BMW also operates a car sharing program that includes a growing number of EVs.

As for the alleged intellectual property theft, BMW's response has been shifting, according to Paris-based news channel TF1. The company initially denied conducting or ordering tests on Autolib, then issued a statement earlier this week admitting it hired P3-Group but denying the spying charge. P3-Group's activities are, it says, part of "routine" testing intended to ensure that BMW's EVs are compatible with charging stations across Europe.

French media this week added Volkswagen to what they've dubbed Affaire Autolib. VW admitted that it too had engaged P3-Group to test Autolib's system, according to Le Figaro. As with BMW, the Wolfsburg-based automaker denied that it was spying, calling the testing "entirely normal." At this week's Frankfurt Auto Show, Volkswagen announced an agressive EV ramp up that CEO Martin Winterkorn vowed would deliver "market leadership in electric mobility" by 2018.

Photo: Antoine Antoniol / Getty Images

For Shame: Chicago Will 'Out' Energy Hogs To Drive Reductions

Which would you pick as your place of residence or business: the nice, energy efficient building, or the energy sink with a giant scarlet letter E on its side?

Chicago wants to start using such public shaming—more properly known as energy benchmarking—as a way to reduce energy usage in its biggest buildings. The city council passed an ordinance this week that will require operators of the 3500 or so buildings in the city with more than 4600 square meters (50 000 square feet) of floor space to track and verify energy consumption and report it directly to the city.

“Do you check the mileage before you purchase a car?," Mayor Rahm Emanuel asked in a Chicago Tribune article. "Do you check the energy-efficiency of a utility before you purchase it? Do you do comparative? What is wrong with providing people information?” Emanuel reasoned.

Opponents of the measure have said it would discriminate against older buildings, but that's kind of the point: Chicago wants to cut energy use by 30 percent by 2020 in half its buildings. And those older ones are the most likely energy hogs.

The measure includes a delay in the start of reporting in order to give building owners a chance to improve; any residential building between 4600 square meters and 23 225 square meters will first begin reporting in June 2016. Building energy use will be tracked using an online tool administered by the Environmental Protection Agency known as Portfolio Manager; apparently, buildings that use the tool reduce energy needs by an average of 7 percent. In the press release announcing the ordinance, the city claims that if the buildings covered by the measure save only 5 percent each, the result would be a savings of $250 million and an emissions reduction equivalent to taking 50 000 cars off the road.

This scarlet-letter route is catching on, with Chicago being only the latest to join in. Philadelphia passed a similar law in summer 2012, and the first compliance deadline is approaching this October. Washington, D.C., was out in front with a bill passed in 2008; the first reporting deadline arrived in April of this year. New York, San Francisco, and Boston, also have benchmarking regulations in place.

The interesting thing about this plan is that there isn't any particular idea for improving energy use contained within the laws. They're just intended to get people embarrassed enough to do something to improve. Of course, possibilities for upping the efficiency of buildings abound—including some of the provisions included in the Shaheen-Portman energy efficiency bill currently being debated in Congress—so maybe just the prospect of having bottom-of-the-barrel status once reporting begins is enough.

And though the laws only look to big buildings, there is plenty of opportunity even among those: the Tribune notes that though only 1 percent of Chicago's buildings will be covered under the ordinance, they account for 22 percent of the city's total building-related energy use. And more generally, buildings certainly are energy guzzlers: commercial, industrial, and residential buildings in the U.S. accounted for 7 percent of the world's total energy consumption in 2010. Just in the United States, buildings accounted for 41 percent of all the energy we use, ahead of transportation and industry.

No one wants that big red E on their building; we'll see if benchmarking really ends up making a dent in our energy use.

Storing Energy From Solar and Wind Isn't Always the Best Idea

Energy storage is often considered an ideal scenario when it comes to renewable energy. Saving up energy generated in bright and windy conditions and using it when the sun stops shining and the wind stops blowing feels like a no-brainer. But a new paper by researchers at Stanford University suggests that in certain circumstances, simply curtailing, or slowing down, that wind turbine can be a better deal—energetically speaking—than storing up the power.

"Curtailing renewable resources results in an immediate and obvious forfeiture of energy," the investigators wrote in the journal Energy & Environmental Science. They cite the example of Texas, where as much as 17.1 percent of wind generation was curtailed each year between 2007 and 2012; that totals a massive 13 terawatt-hours of electricity. "However, flexible grid technologies [including storage] can also consume significant amounts of energy in their manufacture and operation. These embodied energy costs are not as immediately apparent, but they are an energy sink from a societal perspective." In other words, storage technologies cost energy in various ways as well, and it is no guarantee that building and deploying them will represent energy savings in all scenarios.

The researchers calculated the energy return on investment (EROI) for various storage technologies in combination with solar and wind power. First of all, when it comes to solar, all technologies considered, including compressed air storage and batteries like zinc-bromine and vanadium redox, worked better than curtailing the generation. So, for solar: always store what you can, no matter what storage medium you've got lying around. The best energy returns come from compressed air and pumped hydroelectric, but lithium-ion batteries aren't bad either.

Wind power is another story. While compressed air and hydroelectric storage make sense, no battery technology out there is good enough to yield an EROI for which storage would beat out curtailment. Li-ion is closest, but still lags far behind compressed air and pumped hydro. The battery tech brings EROI down well below the curtailment level (see bottom graph), but interestingly, the wind-plus-battery combo still has a higher overall EROI than solar photovoltaic power does on its own; that's thanks to wind having a roughly10-fold better EROI than solar.

This means that purely from an energy perspective—and thus an emissions perspective as well—certain storage technologies are not worth pairing with a wind farm. Notably, this analysis does not take economics or other factors into account, but if energy is the point here, then batteries and wind are a no-go at the moment. The study's authors recommended that research should work on battery  cycle life: increasing the number of cycles a battery is capable of by a factor of as much as 20, so they can handle 10 000 to 18 000 cycles. That level would bring the EROI numbers up to make curtailment the worse option. For the moment, though, this means that an increasing focus on compressed air in particular is probably the right move.

Photo: Janet Ramsden/Flickr

Germany Could Face Electricity Customer Revolt

Der Spiegel, Germany's leading weekly news magazine, reports this week that Germany's aggressive renewables program "has come with a hefty price tag for consumers," especially the poor. Though no immediate action is expected before national elections in two weeks, there may be new initiatives soon after, as "government advisors are calling for a completely new start."

The article is notable not only for its length and depth, but also because Der Spiegel is generally characterized as left-liberal in its inclinations and, therefore, would not be expected to be so critical of a program advanced by its very readers—the socialists and Greens who adopted the program more than a decade ago.

But first let's accentuate the positive: The "feed-in tariff" put in place at the end of the 1990s has been a hugely powerful lever in driving development of renewable energy in a country that is itself one of the world's major markets and a top incubator of new technology. The law and its successors established schedules such that anybody installing any of several types of renewable generation can sell the electricity they generate into the national grid at prices guaranteed over time. The premium prices are covered out of a pool funded by an electricity surcharge levied on all German power consumers.

To a remarkable extent, Germans so far have been willing to pay those prices, for the sake of making the country a world leader in environment-friendly power technologies. But today, says Der Spiegel, the prices are beginning to look not just intolerably high and unsustainable, but in some ways unfair and perverse in their effects. The surcharge, already high at 5.3 euro-cents per kilowatt-hour, is slated to rise 20 percent to between 6.2 and 6.5 cents/kWh, according to the government. In large part because of the surcharge, Germany's electricity costs are among the highest in Europe and could soon be among the highest anywhere in the world.

Without a change in course, says the government, costs could rise to 40 cents/kWh by 2020. At present-day prices, the average German family of three pays about 90 euros per month for electricity, the equivalent of about US $135—about twice as much as in the year 2000.

The high rates have been affecting less-advantaged members of society disproportionately, argues Der Spiegel, . "…[R]enewable energy subsidies redistribute money from the poor to the more affluent., as when someone living in a small rental apartment subsidizes a homeowner's roof-mounted solar panels through his electricity bill."

There are other perverse effects. Though authoritative studies suggest that Germany's expansion of renewables will require as much as 30 billion kilowatt-hours of energy storage by 2050, in the short run, wind and solar installations have sometimes led to shutdowns of storage facilities. Der Spiegel provides examples of long-standing pumped hydro installations that may be taken offline because the growing amount of power being generated by solar plants means there is less demand for their output during daytime peaks.

A major steel mill near Hamburg sometimes has to suspend operations because energy from nearby intermittent sources fails to materialize as expected. Meanwhile a major offshore wind farm in the area is behind schedule getting its transmission link to the mainland completed (as reported here).

An additional and predictable development results from Germany's post-Fukushima nuclear phase-out: Old and dirty coal-fired plants like the one at Grosskotzenburg [photo, above] are being used more rather than less, leading for the first time in two decades to an increase in the country's greenhouse gas emissions.

To be sure, Germany's GHG emissions are 25 percent lower than in 1990, in contrast (for example) to those of the United States, which are 10 percent higher. But U.S. emissions have declined in the last five years, whereas Germany's experienced an uptick last year, by 2 percent. "This development cannot become a tendency," Germany's environment minister has said.

Der Spiegel proposes that the solution may be at least in part to adopt what it calls "the Swedish model" as a successor to the feed-in tariff. In Sweden, says the magazine, the government sets greenhouse gas reduction targets for each economic sector but leaves it to the players in each sector to decide how to make the cuts. But whether such a system could work in an economy the scale of Germany's remains to be seen. In the meantime, Germans are left with the environment minister's rather lame, band-aid suggestions: Don't preheat before cooking; keep lids on your stove-top pots; and turn down the brightness and contrast on your televisions.

Photo: Dmitry A. Mottl

How to Harness the Power of 70,000 Suns

Stacked solar cells are already the most efficient solar cells available, but researchers at North Carolina State University have found a technique to boost the cells' effectiveness even further.

The electrical engineering team from NC State focused on the connection junctions between the layers of the stacked cells, also known as multi-junction cells. The research appeared in a paper published in the online September 5 issue of Applied Physics Letters.

Stacked solar consists of layers of cells that can capture a larger portion of the solar spectrum because photons not absorbed by the first cell are transmitted to the second and sometimes third cell, where some of the remaining solar radiation is then absorbed. 

One of the limitations of how much solar energy can be converted to electricity is the connecting junctions between the cells. The junctions absorb some portion of the solar energy and also siphon off the voltage produced by the cells, according to the researchers.

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Illinois Regulators Discount Smart Meter Fires

Having investigated several fires that broke out following installation of smart meters, the Iliinois Commerce Commission (ICC)—the state electricity regulator, among other things--has concluded that loose wiring and corrosion in the meter bases and not the meters themselves were to blame.

"Installers … received additional training to swap the analog meters for the digital ones, but they [were] not trained to perform extensive repairs to the old and deteriorated bases to which the meters are connected," the Chicago Tribune reported. "Regulators [said] the fact that installers did not recognize, repair or report the poor conditions contributed to fires and overheating."

Though the meter fires have made for bad publicity and provided ammunition to local activists opposing smart meter installation [see photo], the problem as such is obviously highly addressable. ComEd, the major Illiinois utility, has assured regulators that it is beefing up training so that installers will recognize and fix possible problems in the future. What is more, ComEd told the ICC, the new digital meters can take temperature readings and report overheating to the utility—something the older analog meters certainly could not do.

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Personal Comfort Systems Could Slash Office Energy Use by 30 Percent

No one ever seems happy with the temperature in the office. Someone has a sweater stashed away in a drawer to throw on when the air conditioning blasts in summer, while another worker, seated one desk over, is always sweating in winter.

Researchers at the University of California at Berkeley’s Center for the Built Environment (CBE) recently received a US $1.6 million grant to tackle this long-standing problem. Their solution: a Personal Comfort System (PCS) that not only keeps individuals happy at their desks, but also provides feedback to the building’s facility managers so they can fine-tune the heating, ventilation, and cooling (HVAC) system.

“It’s even better than having a thermostat at every workstation, if that were possible,” Edward Arens, the center's director and the project’s co-principal investigator, said in a statement.

The PCS has foot warmers, fans and low-wattage devices embedded into office chairs to warm or cool an office worker on demand. The system focuses on the most thermally sensitive parts of the body, such as the head and feet, which is more efficient than maintaining one temperature for an entire office space.

On average, the PCS uses 2 watts for cooling and 40 watts for heating, far lower than the 1500 watts that a conventional space heater uses. The entire system operates on a rechargeable lithium ferrophosphate battery and turns off when the user leaves his or her desk.

The PCS's sensors don't just yield benefits in terms of comfort. The information they relay to facilities managers give greater control over the building’s energy consumption. The goal of the project is to integrate occupant information with cutting-edge energy controls and computer sciences to cut energy use. The researchers have found that for a typical California commercial office space, the systems can cut HVAC electricity use by up to 30 percent and cut natural gas use by 39 percent. The team will put together about a hundred prototypes of the special heating-cooling chairs for pilot studies.

The researchers are working with architectural and engineering firms and also the local utility, Pacific Gas & Electric. Even with a multitude of stakeholders, there are plenty of challenges. There are issues with integrating new technologies into legacy HVAC systems, and competition from other technologies that can also save energy.

Advanced occupancy sensors, for instance, can fine-tune HVAC output and lighting level based on how many people are in a room. Social networks can help building managers engage tenants in energy efficiency programs. Other upgrades, such as sensors on key pieces of equipment, can also save energy without involving fickle tenants at all. New technologies for HVAC and chiller systems can slash electricity use when they replace older, less-efficient systems.

For the average office worker, however, the idea of personal comfort system is a welcome concept. It might even free up the sweater drawer for another use.

 

Photos: Center for the Built Environment

Carbon Emissions: Tax or Regulate?

Harvard economist N. Gregory Mankiw, an adviser to former President George W. Bush, made an eloquent case for enactment of a national carbon fee in the Sunday issue of the New York Times. Democrats in the House of Representatives, led by Henry Waxman of California, have made the same proposal. Does the conjunction of a highly respected Republican intellectual and Democratic legislators suggest that gridlock is about to be broken on the immensely controversial subject of carbon taxation? Not a chance.

This is not because the case for setting a carbon fee is weak on its merits, or because the case against administrative regulation of carbon is so strong. If energy prices properly and uniformly reflected the social cost of emitting carbon dioxide, as Mankiw spells it out, you might respond with a number of money-saving actions that include: buying a smaller, more fuel-efficient car, swapping your traditional car for one with new technology, car pooling to work using public transportation, moving closer to your job, buying a smaller house that requires less energy to heat and cool, adjusting the thermostat to keep it cooler in winter and warmer in summer, putting solar panels on your roof, buying more energy-efficient home appliances, eating more locally produced foods, and so on. Having enumerated the many merits of a fee and decried the manner in which the U.S. government has tried to change consumers' behavior, Mankiw zeroes in on U.S. automotive fuel-efficiency rules (the CAFE standards) as an example of regulation gone awry. Quoting former GM executive Robert M. Lutz, Mankiw describes the whole idea of requiring automakers to sell more fuel-efficient cars as a bureaucratic nightmare. "CAFE is like trying to cure obesity by requiring clothing manufacturers to make smaller sizes," Lutz has said.

Had he been given more space in the Times, Mankiw would not have had any trouble citing multiple other examples of alleged excesses of the regulatory model: the tangled procedures states have adopted to implement renewable energy portfolio standards, typically involving clean energy credits with "carve outs" for specially favored types of generation; or the tightening clean-air rules that have prompted Republicans to accuse Democrats of conducting a "war on coal."

A news report in today's Wall Street Journal describes a small tempest raging over a newly issued Department of Energy standard related to the efficiency of microwave ovens. Energy Secretary Moniz boasted about the standard last week in a presentation about President Obama's climate action plan. What's at issue is the estimated social cost of carbon emissions. The DOE set the cost at $36 per ton ($39.6 per tonne) in justifying the microwave standard, up from $21 per ton ($23.1 per tonne) in 2010. The Journal spells out the pros and cons of the estimated $36 carbon cost, but obviously there's no "right answer" to the question of where a perfect market would price greenhouse gas emissions.

Mankiw suggests that a carbon fee might be enacted roughly as Waxman et al. have suggested "if the Democratic sponsors conceded to using the new revenue to reduce personal corporate tax rates." Dream on. Tea-Party Republicans will not agree to introduction of a new tax, whatever it is called, unless possibly there were a net reduction in total taxation; Democrats from the states that would be hardest hit by a carbon fee will not agree to the fee unless the tax code provides their constituents with a net offset. The gridlock will not be broken unless next year's midterm elections improve the president's position, contrary to the usual pattern, and the president's negotiators return from Paris at the end of 2015 with a global climate agreement that Americans like a lot better than the Kyoto Protocol.
 

 

Renewable Energy to Be Price Competitive in Western U.S. by 2025

Renewable energy installations are an active business in most of the Western United States, in part due to renewable portfolio standard (RPS) mandates, which require a certain percentage of installed capacity to come from renewable sources.

But most of those RPS requirements will be met by 2025, which leaves the “what’s next?” question. The National Renewable Energy Laboratory (NREL) aims to provide the answer in its latest report [PDF], "Beyond Renewable Portfolio Standards: An Assessment of Regional Supply and Demand Conditions Affecting the Future of Renewable Energy in the West."

The report concludes that there won’t necessarily be a precipitous drop in renewable deployment after the mandates are met. There will still be population centers such markets in California, the Southwest and the Pacific Northwest whose demand for additional renewable energy will make financial sense, .

NREL found that if utility-scale solar and wind are deployed in prime areas that haven’t by then been exploited to meet the RPS mandates, the renewables, including transmission costs, could be cost competitive with new combined-cycle natural gas-fired power plants in 2025.

"The electric generation portfolio of the future could be both cost effective and diverse," said the report's lead author, NREL senior analyst David Hurlbut, in a statement. "If renewables and natural gas cost about the same per kilowatt-hour delivered, then value to customers becomes a matter of finding the right mix.”

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