A second life for electric-drive vehicle batteries

The National Renewable Energy Laboratory (NREL) is looking to give batteries from electric drive vehicles (EV) a “second life.” Possible secondary uses for lithium ion (Li-ion) batteries include residential and commercial electric-power management, power-grid stabilization to help provide reliable electricity to users, and renewable energy system firming—which in this case involves using batteries to make power provided to the grid by variable resources such as wind and solar energy more usable.

The project will begin with a comprehensive technical and economic analysis addressing all aspects of a battery’s lifecycle in search of the best second-use strategies, followed by a comprehensive test program to verify findings, particularly battery lifetimes. For the field test, researchers will deploy aged EV batteries at the University of California, San Diego’s campus-wide electric power grid.

The cost of Li-ion batteries also currently affects the affordability of EVs for consumers. Researchers will do a technical and economic investigation to see if the potential for reusing Li-ion batteries could lead to consumers obtaining a cost credit for the remaining value of a used battery, potentially offsetting a portion of the initial cost to the EV buyer. It might be the case that while a battery no longer has sufficient power for an EV, it still has the capability to meet the needs of other less demanding applications.

Allocating used electric vehicle batteries to second-use applications also could benefit the environment by delaying the recycling or disposing of batteries, and by supplying a service that improves the efficiency and cleanliness of other industries.

The NREL award to the CCSE team leverages an ongoing UC Davis-CCSE-TSRC study funded by the California Energy Commission on the repurposing of used EV batteries for home energy storage. The total budget for the NREL-CCSE second use battery project is approximately $1.3 million with 51 percent of the funding coming from CCSE and its partners.

WPE

NREL to explore legal routes to state feed-in-tariffs

In a technical report NREL issued, “Renewable Energy Prices in State-Level Feed-in Tariffs: Federal Law Constraints and Possible Solutions,” the organization discusses how state legislatures and their utility commissions seeking to attract renewable energy projects are considering arrangements called “feed-in tariffs.” These would obligate retail utilities to purchase electricity from renewable producers under standard arrangements that specify prices, terms, and conditions. This standardization simplifies purchasing, provides revenue certainty to generators, and is said to reduce the cost of financing generating projects.

However, two statutes — the Public Utility Regulatory Policies Act of 1978 (PURPA) and the Federal Power Act of 1935 (FPA) — limit the discretion of state-level tariff designers. So the National Renewable Energy Laboratory (NREL) was asked to explore how states can lawfully implement feed-in tariffs.

There is no official definition of “feed-in tariff, “ but a technical report issued by NREL assumes the tariff is the result of a legal mandate. A state wishing to create that mandate has two options: rely on the purchase obligations under PURPA, shaping the state-level requirements to satisfy PURPA’s constraints (sellers under this approach don’t need to comply with the FPA). Or, the state can rely on a state statute independent of PURPA (where sellers must comply with the FPA unless the Federal Energy Regulatory Commission (FERC) has exempted them).

For states relying on the PURPA mandate, certain feed-in tariffs are possible without action by FERC or Congress. The problem is that utilities can now seek exemption from the PURPA purchase requirement. Under PURPA amendments enacted in 2005, FERC has exempted some utilities from their PURPA obligation to buy power from qualifying facilities with capacities greater than 20 MW. If states with jurisdiction over these utilities wish to establish feed-in tariffs, they will have to create a mandate under state law and the sellers will need to comply with the FPA.

Given FPA requirements, a state-level feed-in tariff outside of PURPA isn’t legally possible in the United States today. But, a clear path to state-level feed-in tariffs, outside of PURPA, would open for small qualifying facilities if FERC clarified or modified its precedents.

The report concludes there are paths to non-preempted, state-level feed-in-tariffs under current federal law. These paths would either be available now with no further action available by FERC, would become available if the FERC clarified or modified its precedents, or would become available if the FERC issued new rules, declaratory orders, or both to provide guidance that rendered state-set tariff prices lawful under the FPA.

Additional paths are also possible if Congress amends PURPA or the FPA to remove or reduce existing statutory constraints. Detailed discussions involving states, FERC, renewable producers, utility buyers, and possibly congress will be necessary to create a legal context in which states can enact feed-in-tariffs.

Congress could modify PURPA and the FPA to allow states to establish feed-in tariffs unconstrained by current federal law. The intent behind such an amendment would be to create exceptions from PURPA, the FPA, or both, for renewable sellers in states that make known tariffs having certain characteristics. The result would be to entrust in the sellers an automatic right to sell under state programs.

National Renewable Energy Laboratory

www.nrel.gov

NREL Study Shows Power Grid Can Accomodate Substantial Increase In Wind & Solar

The National Renewable Energy Laboratory (NREL) recently released an initial study assessing the operational impacts and economics of increased contributions from wind and solar energy producers on the power grid. The Western Wind and Solar Integration Study examines the benefits and challenges of integrating enough wind and solar energy capacity into the grid to produce 35 percent of its electricity by 2017. The study finds that this target is technically feasible and does not necessitate extensive additional infrastructure, but does require key changes to current operational practice. The results offer a first look at the issue of adding significant amount of variable renewable energy in the West and will help utilities across the region plan how to ramp up their production of renewable energy as they incorporate more wind and solar energy plants into the power grid.

The study focuses on the operational impacts of wind, photovoltaics, and concentrating solar power on the power system operated by the WestConnect group of utilities in the mountain and southwest states. WestConnect is a group of transmission providers, which includes Arizona Public Service, El Paso Electric Co., NV Energy, Public Service of New Mexico, Salt River Project, Tri-State Generation and Transmission Cooperative, Tucson Electric Power, Western Area Power Administration, and Xcel Energy. Though wind and solar output vary over time, the technical analysis performed in this study shows that it is operationally possible to accommodate 30 percent wind and 5 percent solar energy penetration. To accomplish such an increase, utilities will have to substantially increase their coordination of operations over wider geographic areas and schedule their generation deliveries, or sales, on a more frequent basis. Currently generators provide a schedule for a specific amount of power they will provide in the next hour. More frequent scheduling would allow generators to adjust that amount of power based on changes in system conditions such as increases or decreases in wind or solar generation.

The study also finds that if utilities generate 27 percent of their electricity from wind and solar energy across the Western Interconnection grid, it would lower carbon emissions by 25 to 45 percent. It would also decrease fuel and emissions costs by 40 percent, depending on the future price of natural gas.

Other key findings from the study include:

• Existing transmission capacity can be more fully utilized to reduce the amount of new transmission that needs to be built.
• To facilitate the integration of wind and solar energy, coordinating the operations of utilities can provide substantial savings by reducing the need for additional back-up generation, such as natural gas-burning plants.
• Use of wind and solar forecasts in utility operations to predict when and where it will be windy and sunny is essential for cost-effectively integrating these renewable energy sources.

The study was undertaken by a team of wind, solar and power systems experts across both the private and public sectors. The study complements the recently released Eastern Wind Integration and Transmission Study, which examines the feasibility of integrating up to 30 percent wind in the eastern states.

The report is an important first step in assessing the impact of solar and wind energy on the electrical grid.  Under the American Recovery and Reinvestment Act, the Department of Energy is investing more than $26 million to further study the Western transmission interconnection, which will help states, utilities, and grid operators prepare for future growth in energy demand, renewable energy resources, and Smart Grid technologies.

The study can be downloaded at http://www.nrel.gov/wwsis.

NREL & Samsung Obtain Decades of Wind Power Data in Two Months of Testing

In a coupling of giants recently, the 2.5-megawatt dynamometer at the U.S. Department of Energy’s National Renewable Energy Laboratory blasted 12.6 million inch pounds of torque at Samsung’s 185,000-pound wind turbine drive train.

The King Kong of wind turbines battled the Godzilla of dynamometers to a draw.

It was the greatest amount of power ever measured at NREL’s dynamometer lab, and the largest full-scale dynamometer test of a wind turbine drive train ever done in the United States.

Samsung officials wanted to learn how well their 250-foot-high wind turbines would survive 25 years of gales, gusts, rain, rust, cyclones and dust.

They turned to NREL because its dynamometer can simulate worst-case wind conditions 24 hours a day. In a few months of testing, a manufacturer can learn whether its gear boxes, bearings and cog wheels will stand up to real-world conditions.

NREL’s 2.5-megawatt dynamometer is outfitted with a powerful 3,550-horsepower electric motor coupled to a three-stage epicyclic gearbox. The motor can produce speeds up to 30 revolutions per minute, simulating everything from soft breezes to backbreaking gales.

Decades of Data in Two Months of Testing

“If we tried to get this information out in the field, it would take years to acquire this kind of data,” Ed Overly, master research technician and dynamometer gatekeeper at NREL’s National Wind Technology Center (NWTC), said. “We run the turbine under test conditions for 24 hours a day, seven days a week at 2.1 megawatts. We can monitor how all the fluid and bearing temperatures equilibrate at their maximum points. We see how well the inverter operates under different load conditions to detect if there are any unknown faults.”

“Doing this test with Samsung has given us the experience of testing a very large machine at the Dynamometer Facility, which we’ve never done before,” Overly said.

Samsung already has a similar sized (2.5-megawatt) wind turbine running in Lubbock, Texas, that can provide electricity for 1,800 homes, said In-kyu Kim, manager of the Wind Turbine Development team at Samsung. But the company had never tested one of its turbines above 600 kilowatts.

Jaedoo Lee, manager at Samsung Heavy Industries, said his company chose NREL “because we needed to test for performance and we know NREL is prestigious. We like to simulate and test all the tough and extreme conditions that would happen in the real world.”

“We wanted a third-party test for quality,” Lee added. “NREL is the perfect test facility for us. We’d like to keep working with them as we develop wind turbines for off-shore uses.”

Moving 185,000 Pounds: A Herculean Endeavor

How did the huge wind turbine drive-train make its way into the dynamometer’s test bay?

“It was a monumental task,” Overly said. “We had to move 200,000 pounds of equipment out of here and clean up the whole high bay, then move in the Samsung turbine – within a week.”

A 185-foot-long, 19-axle rig hauled the drive train and electrical equipment from Houston to the NWTC. Then a 400-ton crane moved the drive train onto a track and cart system, temporarily laid just for the move. “We off-loaded it and brought it into the dynamometer in one piece,” Overly said. It’s the largest piece of equipment ever installed in the Dynamometer Test Facility.

The software used by NREL and Samsung tells the dynamometer what kind of torque it should give the drive train.

“We want to provide an accurate reproduction of loads the drive train will see in the field,” NREL senior engineer Robb Wallen said as the dynamometer put the Samsung drive train though its paces last month. “The tower, rotor and blades are represented by computer models which interact in real-time with the drive train and turbine control system just like their real counterparts.”

Using a virtual wind-speed profile the computer model calculates what the main shaft torque should be and sends the torque commands to the dynamometer. “The end result is the drive train responding to a variety of wind conditions as it would in the field,” Wallen said. It’s a very sophisticated test and it’s never been done here before.”

The tests, which ran for a couple months early this year, “accelerate the startup, the actual checkout, as well as spotting any kinds of deficiencies,” Overly said.

NREL is the only place in the nation where “you can run a wind turbine under load conditions, watch it operate real-time, be standing near to it and hear how it operates,” Overly said. “You can’t accomplish that up in a wind turbine in the field.”

Meanwhile, NREL is taking the next giant step – designing a 5-megawatt dynamometer that will be capable of testing most of the large turbines expected to roll off humungous assembly lines in the next decade.

www.nrel.gov