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Minnesota Finds Net Metering Undervalues Rooftop Solar

Utilities should be paying more for their customers' surplus solar power generation according to a solar pricing scheme approved by Minnesota's Public Utility Commission last month and expected to be finalized in early April. Minnesota's move marks the first state-level application of the 'value of solar' approach, which sets a price by accounting for rooftop solar power's net benefits, pioneered by the municipal utility in Austin, TX.

Minnesota is one of 43 U.S. states that requires utilities to pay retail rates for surplus solar power that their customers put on the grid. Utilities across the U.S. are fighting such net metering rules, arguing that they fail to compensate the utility for services that their grid provides to the distributed generator. So last year pro-solar activists and politicians in Minnesota called the utilities' bluff, passing legislation tasking the state's Department of Commerce with calculating the true value of rooftop solar power.

Now the verdict is in, and the state's 'value of solar' formula -- affirmed by the PUC -- finds that distributed solar generation is actually worth more than its retail power price according to John Farrell, an economist and senior researcher at the Institute for Local Self-Reliance, a Minneapolis-based economic think tank, and the principal architect of last year's solar legislation.

What put solar's benefits over the top was the state's decision to adopt the U.S. EPA's value for avoided carbon emissions -- the social cost of carbon in EPA's lingo. At $37 per metric ton of carbon this is worth almost 3 cents for every kilowatt-hour of natural-gas fired generation displaced by rooftop solar power in Minnesota, according to a preliminary analysis of the PUC's formula by Xcel Energy, the state's largest utility.

Still bigger benefits come from more obvious savings, such as displaced fuel for power plants (about 5.5 cts/kwh) and avoided construction of new power stations (about 3.4 cents/kwh). In sum, solar values in at 14.5 cts/kwh, which is 3-3.5 cents more per kilowatt than Xcel's retail rates.

As for the grid costs utilities are complaining about, such as managing the variability of solar power flows, the PUC found they were essentially zero and would remain so until solar generation exceeds about 15 percent of the state's power supply. That could take a while. Solar currently provides less than 0.1 percent of Minnesota's power, and would rise to just 1.5 percent by 2020 under state mandates.

Despite the appearance that utilities lost and solar generators won, Farrell says the new value of solar rate plan is actually a boon to both. The rate works like the feed-in tariffs popularized by Germany, whereby generators would get a 25-year contract at a set rate. Farrell says guaranteed pricing will benefit consumers by easing the financing of new solar installations. "It’s a contract from the utility. That's a pretty good security to bring to the bank to finance solar," he says.

Solar value pricing could be good for utilities too because the cost of net metering is rising as they push up their retail power rates. Farrell says that Xcel's rates rose 4.5 percent per year over the last decade, and they have proposed steeper rate increases for the years ahead. Unless natural gas prices spike, he says, valuing solar will soon be a better deal for utilities. "In 5-6 years value of solar should be lower than the retail rate," says Farrell.

For now the value of solar rate is an option available to Minnesota utilities. No word yet as to whether any plan to abandon the net metering rules they so dislike.

Photo: iStockphoto

Wind More Favorable Than Solar For Grid-Scale Storage, Study Finds

Low-cost, grid-scale energy storage is often described as the holy grail of the renewable energy industry.

Wind and solar resources have come down dramatically in price in recent years, and installations have increased significantly, but the intermittency of the two energy resources remains a challenge for grid operators. So Utilities are ramping up testing storage technologies that can help balance and capture wind and solar energy when it’s not needed and save it for times of high demand. In 2013, California passed a law calling for 1.3 gigawatts of storage capacity from its largest utilities by 2020. 

But not all storage and renewable pairings make sense when evaluating the energetic cost of the full lifecycle of the technologies, according to new study from Stanford University.

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Korean Island Plans for All Cars to Be Electric by 2030

South Korea's Jeju Island has spent years building out its electric vehicle (EV) infrastructure to encourage residents to make the switch from gas-guzzlers to battery-powered cars.

Soon, the small resort island will have the cars to match the infrastructure. This week, Jeju is hosting its inaugural International Electric Vehicle Expo [PDF]. At the event, several prominent domestic and foreign carmakers announced that they would start selling their all-electric vehicles on Jeju starting this year. The increased availability of EVs comes at the same time as new federal subsidies to help lure drivers to purchase EVs. Jeju Island has a goal for all its vehicles to be electric by 2030 as part of its “Carbon Free Island Jeju” plan, which was first announced in 2012.  

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Attack on Nine Substations Could Take Down U.S. Grid

There are more than 55 000 transmission substations in the United States, but an attack on less than 10 could plunge the entire nation into darkness, according to a study by the Federal Energy Regulatory Commission (FERC) that was obtained by the Wall Street Journal.

According to people familiar with the report, the Wall St. Journal reported that just nine substations could take down the transmission grid for the entire country. Currently there are no regulations that require protection for key substations, but that could change.

Earlier this month, FERC directed the North American Electric Reliability Corporation (NERC) to develop reliability standards for grid operators to address physical security threats.

“Today's order enhances the grid’s resilience by requiring physical security for the facilities most critical to the reliable operation of the Bulk-Power System,” FERC Acting Chairman Cheryl LaFleur said in a statement. “It will complement the ongoing efforts of FERC and facility owners and operators to ensure the physical security of the grid.” 

The order has three steps: owners and operators must perform a risk assessment to identify facilities that are critical; once those facilities are identified owners must evaluate potential threats to those sites and then they must develop and implement a security plan.

The focus is protecting the transmission substations from a physical attack, which could be just as damaging as a cyber attack. Last April, snipers targeted a Pacific Gas & Electric substation in California, which did not cause an outage, but did raise questions about the vulnerabilities of the grid.

"There are probably less than 100 critical high voltage substations on our grid in this country that need to be protected from a physical attack," former FERC chairman Jon Wellinghoff told the Wall Street Journal in an email. "It is neither a monumental task, nor is it an inordinate sum of money that would be required to do so."

The steps sound easy enough, but many seemingly simple procedures were not in place to prevent the 2003 blackout, or the cascading outage in Southern California in 2011. There are many more tools and data sources to help identify outages, but a lack of planning and the novelty of the technology means that it is not always leveraged by grid operators.

In some ways, protecting against a physical attack may be easier than protecting against a cyber attack. Since the grid was first built, utilities have been physically protecting facilities, where as cyber threats are a more recent development that utilities are less familiar with addressing. A recent survey from Utility Dive found that cyber security was on the bottom of a list of pressing challenges for utilities, with grid reliability only somewhere in the middle.

Better coordination between utilities and grid operators will be key in preventing cascading outages in the future. FERC and NERC are evaluating whether mandatory reliability standards may be necessary to physically protect the grid, and the government agencies are also encouraging more cooperation between utilities to address grid vulnerabilities.

The new standards for critical transmission substations are due from NERC in June.

Chinese Automaker Adopts New Efficient Engine Design

With all the buzz surrounding electric cars, it’s worth remembering that internal combustion engines remain an active area of technology development. For example, a Michigan-based start-up called EcoMotors has created a new type of engine that could improve fuel economy by 20% compared to conventional turbo diesel engines—and be built at a lower production cost. Yesterday, EcoMotors announced the creation of a joint venture to start building these engines in China.

The company's Opoc engine breaks with conventional designs in a number of ways to reduce weight and volume while saving fuel. It has two cylinders, which each house two pistons. That increases the power density because pistons need to travel half the distance, according to the company. The two-stroke engine also uses electrical control systems in place of mechanical components to precisely regulate combustion, it says.

An electrically controlled clutch, for example, allows the engine to operate with both two-cylinder modules operating, or with one turned off to save fuel while driving. Although EcoMotors plans to initially manufacture diesel engines, the basic architecture can also work with gasoline, natural gas, or biofuels.

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Earth’s Infrared Radiation: New Renewable Energy Frontier?

The Earth continuously emits 100 million gigawatts of infrared heat into outer space. That’s enough to power all of humanity many thousands of times over. Capturing even a fraction of that would mean an end to our energy woes. Harvard University researchers are now proposing a way to harvest this untapped source of renewable energy.

They have come up with two designs for a device they call an “emissive energy harvester” that would convert IR radiation into usable power. Today's technology isn't sufficient for an efficient, affordable harvester, the researchers say. But they've laid out a few different paths towards such devices in the journal Proceedings of the National Academy of Sciences.

It seems counterintuitive, but the devices generate power by emitting infrared radiation. "The [device] is emitting much more radiation than it receives," says Steven Byrnes, a postdoctoral researcher working in applied physicist Frederico Capasso’s laboratory at Harvard. "This is the imbalance that we can take advantage of to create DC power."

The first design, which they admit is not the most promising, is a heat engine running between the Earth’s surface and a cold plate. The heat flowing from the ambient surface air to the cold plate, which radiates it out into the atmosphere, would be used to do mechanical work. The concept is simple, but cooling the plate efficiently to a low enough temperature is tough, Byrnes says.

As a case study the researchers looked at how much power such a device would generate in Lamont, Oklahoma, where a facility has been measuring IR radiation intensity. They found that they would get an average of 2.7 Watts from the IR radiation emitted by a square meter of Oklahoma over 24 hours, which is pretty low for large-scale power generation.

So the researchers turn to rectifying antennas, or rectennas, devices that absorb electromagnetic radiation and convert it into direct current electricity. A rectenna is an antenna coupled with a diode. Radiation induces an AC voltage across the antenna, which the diode rectifies to DC.

The researchers argue that rectennas can be run in reverse, generating DC power while emitting radiation, rather than absorbing it. In their design, a nanoscale antenna very efficiently emits Earth's infrared radiation into the sky, cooling the electrons only in that part of the circuit. Because the diode is at a higher temperature than the antenna, current only flows from the diode to the antenna. And because the antenna acts as a resistor, this results in a voltage.

Rectennas are traditionally used to generate power from microwaves, but can be used for higher frequency radiation, all the way up to visible light. Infrared frequency rectennas are a developing technology and the proof-of-principle devices demonstrated so far would generate very little power. But technological advances could improve their efficiency, Byrnes says.

Applying solar-cooking techniques such as reflectors to heat up the rectennas could also increase efficiency. For example, in the Lamont, Oklahoma case study, raising the temperature of a rectenna-based harvester from 20° C to 100° C using solar-cooking techniques would increase the power density of a rectenna from 1.2 W/m2 to 20 W/m2. “Solar panels for heating and cooking are already used in much of the world,” he says. “You could easily couple that to the (infrared) harvester.”

The researchers say that IR antennas should be easy to make on large areas at a reasonable cost. The critical challenge will be making diodes that would work well at the low voltages that would be expected in the harvester. The researchers suggest a few options to get around this problem. One is to use specially designed low-voltage diodes such as tunnel diodes and ballistic diodes.

Needless to say, this vision of IR energy harvesters for renewable power rests on engineers overcoming several technical challenges. But Byrnes says that this is a new energy frontier to tackle. He imagines one day a sheet printed with thousands of tiny infrared-harvesting rectennas that could be laminated on a solar panel or integrated into a solar water heater.

Two New Ideas in Wave and Tidal Power

Waves and tides offer some of the most predictable, consistent, and just generally big energy resources available. Rollouts of actual wave and tidal power installations, however, have been slow and generally limited to pilot projects so far. Part of the reason for this—along with straightforward but difficult problems like transmission—is that there is no consensus at all on what represents the best device designs to actually harness waves and tides. A couple of interesting ideas—one wave, one tidal—were on display this week at the ARPA-E Innovation Summit in Washington, D.C., that offer some clear advantages over many of the other attempts at drawing energy from the oceans.

The wave power idea is closer than the tidal energy one to rollout, with a planned open-water test for this summer. M3 Wave dispenses with all the problems that come with buoys or other above-and-below-the-surface designs by mooring a simple device to the ocean floor. The device, pictured above, involves two air chambers: as a wave passes over the top of the first chamber, the pressure inside increases, forcing air through a passageway to the second chamber. Inside the passageway is a turbine, so the passing air is actually what generates the electricity. As the wave continues on, it raises the pressure inside the second chamber, pushing the air back through the turbine—importantly, it is a bidirectional turbine—and back into the first chamber. Another wave, another cycle. Repeat.

The primary selling point here is its simple and small footprint. There is no impact on ocean view, on shipping or fishing traffic, and rough seas above won't endanger the system in any way. M3 is selling it as "expeditionary" wave power, meaning it might be brought along on a ship and deployed for things like disaster relief; the company suggests such a deployment could produce 150 to 500 kilowatts. The system will undergo open-water testing at a U.S. National Guard facility, Camp Rilea in Oregon, in August.

On the other side of the country, a group at Brown University has developed what they call an oscillating hydrofoil, intended to minimize some of the impacts of tidal power devices and increase efficiency. The hydrofoil is mounted on to the sea floor—it resembles a car's spoiler attached to a pole, essentially. As the water flows past that spoiler it oscillates, generating electricity. It is designed so that the pole can actually fold down and out of the way if necessary, allowing for ships or even wildlife (detected with sensors on the device) to pass by without incident. The team received US $750 000 in funding from ARPA-E in 2012, and will soon move to a phase II involving a medium-scale, 10-kw prototype. They have calculated that the device can achieve much better energy conversion efficiencies in tides flowing very slowly than any of the devices that are on or close to market.

The National Renewable Energy Laboratory has estimated that in the United States alone there are wave power resources totaling 252 terawatt-hours/year, with tidal power adding another 17 Twh/year. Those are big numbers, and they come without the intermittency complaints that plague wind and solar power. Any new way to catch the ocean's energy is worth a look.

Can Internet Infrastructure Pay for LED Street Lights?

From Birmingham, UK to Shenzhen and Lyon to Los Angeles, cities across the world are installing light-emitting diodes (LED) street lights to save money and increase safety.

Such retrofits can require a lot of upfront capital that many municipalities do not have. To entice more cities to make the switch, Philips and Ericsson have teamed up to offer a lighting-as-a-service model that pairs Philips’ LED street lights with Ericsson’s small cell mobile networks.

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Huge Offshore Wind Farms Could Tame Hurricanes

What happened when the hurricane ran across thousands of offshore wind turbines? It sounds like a climate scientist's idea of a joke, but a new study has found that offshore wind farms could protect coastal cities by slowing hurricane winds and reducing storm surge.


The spinning turbine blades of offshore wind farms can sap a hurricane's strength by slowing the rotating winds in the outer edge of the rotating storm—an action that leads to smaller waves and eventually slows the wind speeds of the entire hurricane. Simulations have shown that such effects could have significantly dampened the impact of real-life hurricanes Sandy, Isaac and Katrina, according to a new paper detailed in the 26 February 2014 issue of the journal Nature Climate Change.

"We found that when wind turbines are present, they slow down the outer rotation winds of a hurricane," said Mark Jacobson, a professor of civil and environmental engineering at Stanford University, in a news release. "This feeds back to decrease wave height, which reduces movement of air toward the center of the hurricane, increasing the central pressure, which in turn slows the winds of the entire hurricane and dissipates it faster."

Jacobson worked with his colleagues at Stanford and the University of Delaware to simulate hurricane collisions with tens of thousands of offshore wind turbines, based on a computer model that can account for air pollution, energy, weather and climate. They then ran simulations based on the real-life cases of Hurricane Sandy's impact on New York in 2012, Hurricane Isaac's strike on New Orleans in 2012, and Hurricane Katrina's devastating blow on New Orleans in 2005.

In Katrina's case, an array of 78 000 wind turbines off the coast of New Orleans slowed simulated wind speeds by 130 kilometers per hour and decreased storm surge by up to 71 percent. In Isaac's case, the same array of turbines could have decreased peak wind speeds by up to 92 kph and reduced storm surge by up to 60 percent.

Other simulation runs found that even bigger arrays of 272 000 turbines or even 543 000 turbines—located offshore of Cuba and stretching from Florida to Texas—could have dropped Katrina's wind speeds by 158 kph and reduced storm surge by up to 79 percent.

An array of 112 000 turbines stretching from New York City to Washington D.C. could have slowed Sandy's peak winds by 130 kph and decreased storm surge by up to 21 percent. A larger array of 414 000 turbines along most of the U.S. East Coast could have dropped Sandy's wind speeds by almost 141 kph and decreased storm surge by up to 34 percent.

The huge wind farms would do more than just slow down the hurricanes. The largest wind turbine arrays could have extracted up to 2.65 terawatts of peak power from Hurricane Sandy and up to 1.18 terawatts of peak power from Hurricane Katrina—peak power representing the most power extracted at any time during the simulations.

Such simulations suggest that huge wind farms have an edge over traditional coastal city defenses because they slow both wind speeds and decrease storm surge. By comparison, seawalls can only stop storm surge. The cost of building seawalls can also run between $10 billion and $40 billion per installation, whereas expensive wind farms could pay for themselves through energy generation over time.

Hurricane damage to the huge arrays of wind turbines is a risk, Jacobson said. But he pointed out that current wind turbines can stand up to wind speeds of 180 kph within the range of category 2 or 3 hurricanes. And the presence of the huge wind farms could help prevent hurricanes from ever building up to superstorm wind speeds. (The study assumed the wind turbines had a cut-out speed of 180 kph in most of the simulation runs to prevent damage to the turbines.)

Huge arrays of offshore wind turbines remain a far cry from today's reality when the U.S. has yet to build any offshore wind farms. But the new study raises the possibility of hurricane protection as added incentive for building offshore wind farms. Policy planners could consider storm protection as the cherry on top of wind power's known benefits involving renewable power generation, national energy security and the reduction of the human impact on climate change.

Photo: iStockphoto


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