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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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Weakness of Indian Nuclear Regulation Manifest in Reactor Accident

It is no secret that India still lacks a politically independent nuclear oversight authority that is well separated from the industry it oversees. The Fukushima nuclear catastrophe was a recent reminder of just how important it is to have independent nuclear oversight, a lesson already driven home a generation before by the serious U.S. accident at Three Mile Island (TMI). The stubborn refusal of India's government to set up the kind of regulatory authority that is so obviously needed means, in effect, that one cannot have real confidence in a nuclear program that could in principle be one of the world's most important.

A telling but little-known and little-discussed example of what can happen under weak regulatory circumstances was a serious accident that took place at India's Narora reactor in March 1993, an incident that "came close to joining Chernobyl and Fukushima in the annals of industrial civilization," as writer Madhusree Mukerjee put it in a recent review of M.V. Ramana's The Power of Promise: Examining Nuclear Power in India (Penguin/Viking, 2012).

In that accident, which Ramana describes and discusses in detail in his book, two blades broke off a steam turbine and ruptured cooling system pipes, leading to a hydrogen leak, hydrogen fire, and oil fire. Though operators managed to shut down the plant manually, they then had to desert the smoke-filled control room for 13 hours, so that during that time they were "flying blind." Fearing that heat still being generated in the dormant fuel rods might lead to a recriticality, workers heroically climbed atop the reactor vessel to pour reactivity-quenching boron into the core.

All that is disconcerting enough, but what is really disconcerting about the story as Ramana tells it, is that the plant's owner-operator and Indian regulatory authorities were well-aware of issues having to do with the fragile turbine blades and possible oil fires well before the accident and yet did nothing to address those concerns. What is more, there is little or no evidence they did anything after the accident, either. Further incidents, less serious, took place.

Neither Ramana nor Mukerjee, both Ph.D. physicists who have contributed to Spectrum magazine, discusses the Narora reactors' somewhat unusual design and whether the reactors might have a feature that contributed crucially to the Chernobyl catastrophe. The two Narora units are pressurized heavy-water reactors, which means they are a kind of hybrid of the standard U.S. pressured water reactor and Canada's CANDU heavy water reactor. The CANDU, like the RBMK units at Chernobyl, has in certain operating regimes what is called a "positive reactivity coefficient," meaning that if coolant is lost at certain power levels, reactivity drastically escalates rather than de-escalating. It was this feature and operators' disregard of it that was the basic cause of the Chernobyl explosions (as I described in detail in the June 1989 issue of MIT's Technology Review).

What Ramana does do additionally, however, is deliver some telling stories about how the two questionable Narora reactors got built in the first place. When it became clear that the regional grid system was not really big enough to justify and support construction of a nuclear power plant, Indian planners took inspiration from the story about Mohammed and the mountain, as Ramana nicely puts it: That is, instead of deciding not to build a reactor too big for the grid, they instead cooked up hair-brained schemes to make the grid much bigger—with considerable technical support from Oak Ridge National Laboratory, let it be said.

From its earliest inception, as Mukerjee spells out in her review, India's Atomic Energy Commission and Department of Atomic Energy (DAE) have reported directly to the prime minister, enabling them to function largely in secrecy. Thus, when it comes to nuclear safety, "DAE never shares its emergency plans with locals," "does not reveal the health records of its workers," "does not even monitor the health of temporary workers," and "never reveals the quantities of radioactive substances released into the environment by accidents or routine operations."

photo: NPCIL

200 000 EV Fast Chargers by 2020?

The number of fast-charging stations for electric vehicles (EVs) will balloon to 200 000 by 2020 from about 2000 today, according to a new report from IHS Automotive.

The explosive growth is already underway, the study finds. The number of DC chargers are expected to triple to nearly 6000 between this year alone. Fast chargers use high-voltage DC power and can charge a car in less than a half hour instead of the hours it takes with lower voltage AC chargers.

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Energy Secretary Elaborates on Obama's Climate Action Plan

If the most notable thing about President Obama's recent climate speech was the way he gave it, then the most telling thing about his energy secretary's elaboration on that speech, yesterday in New York City, was the size of the audience he attracted. On the last Monday of the North American summer, you'd think that anybody with the means would be in the mountains or at the beach. But some 200 people showed up to hear Secretary of Energy Ernest Moniz talk about the U.S. climate action plan at Columbia University, many of them standing around the walls.

Plainly, climate policy matters to members of the more highly educated public.

Moniz's approach to the subject was matter-of-fact and undramatic. Regarding the general issue of human-induced climate change, he said he has been accurately quoted before as having said that he "was not here to debate what's not debatable." As for the impacts of global warming on Gulf oil extraction, power stations, water availability, fuel transportation, and electricity transmission, he drew attention to a July energy department report on climate change and energy infrastructure.

Reminding his audience that the most bang for the buck can be obtained from improvements in energy efficiency, Moniz said that the department is formulating new standards for appliances on a schedule, starting with microwave ovens and halide lighting, to be followed by commercial refrigeration and electric motors.

Taking exception to the charge that the administration is waging a "war on coal," he said that taking action to reduce carbon pollution from coal is required by the president's "all of the above" approach to climate action. He said $8 billion has been earmarked for carbon capture and sequestration (CC&S).

Noting that energy subsidies almost inevitably prompt allusions to the Solyndra bankruptcy, Moniz said that Tesla obtained a high-risk, half-billion-dollar loan from the energy department in mid-2009. Now Tesla, having paid off that loan ahead of schedule, is making a car that's been rated the world's best and safest—one that's attracting, despite its high price, large numbers of orders abroad.

On renewables, Moniz presented slides showing sharp increases in deployment and sharp decreases in installed prices for wind, solar, LED lighting, and batteries. The cost of photovoltaic modules has come down so much, he said, that future solar gains will have to come largely from improvements in non-PV system components—a conclusion spelled out in a recent report from the Lawrence Berkeley Laboratory, "Tracking the Sun VI."

It turns out that "the future is not always ten years away," he said, surveying those dramatic gains.

On the controversial subject of natural gas fracking, the matter of overwhelmingly greatest concern to his Columbia University audience, Moniz observed that because of the revolution in gas, recent U.S. reductions in greenhouse gas emissions have been much greater than they otherwise could have been. We are already half-way to meeting Obama's 2020 pledge for such reductions, and half of that advance is attributable to utilities' switching generation from coal to gas. Still, he said, serious safety and water issues must be effectively addressed: "saying they are manageable is not the same thing as saying they are being managed."

On the next most controversial subject, nuclear waste, he said the administration supports a consensual, dual-track approach involving consolidation of spent fuel in regional dry cask facilities and development of a national repository for long-term geologic storage. Regarding the two new nuclear plants being constructed in South Carolina and Georgia with Federal loan guarantees, Moniz said the department will be watching closely to see if they are built on schedule and on budget.

Photo: Kevin Lamarque/Reuters


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