The revolution will be renewable

President Obama is definitely serious about transforming the U.S. energy system. His Administration is clearly placing the emphasis on accelerating the development and deployment of renewable energy technologies. Industry leaders are sitting up and taking notice. Two key cabinet members are leading this charge": Secretaries Steven Chu and Ken Salazar of the Departments of Energy and Interior respectively.

One of the key infrastructure challenges that will have to be addressed is how to integrate significant amounts of new renewable energy into the nation's aging grid. (GW)

Integrating Renewables

By Bill Opalka

EnergyBiz Insider

March 4, 2009

Consumers want to buy more of it. States are demanding utilities buy or supply ever-increasing amounts. Policymakers see it as the best hope of reducing carbon emissions. And the power industry is trying to adjust to all of these pressures.

Renewable energy is hot, for all these reasons. While demand for power from all sources increases, overlaid on this issue are more worries about transmission capacity, aging assets and the effect all of this has on reliability.

Reliability drives much of the discussion when utility planners and renewable energy advocates meet to devise a coherent strategy for integrating ever-larger amounts of wind, solar and other energy sources into the transmission grid. Wind, for example, has less than one percent of the electricity production market. But what if it were 20 percent?

Many renewable energy projects, particularly wind and solar, require large amounts of land. The challenges are moving power from a massive multi-megawatt farm in the nation's midsection to population centers maybe 1,000 miles away. Solutions are also needed to solve the challenge of integrating a few kilowatts of juice from a single homeowner's rooftop solar array to distribution network measured in a few square blocks or miles.

Mandates are now underway. With solar set-asides in a few states with renewable portfolio standards, the issue becomes more urgent for utilities from New Jersey to California. While the move toward renewable energy is unrelenting -- nearly 30 states are requiring utilities to purchase energy on an ever-growing sliding scale over the next decade or more -- its twin drawbacks remain: intermittency and the energy's distance from load centers.

"I prefer to call it a variable output resource. Intermittent implies it comes and goes rather quickly and that's not the case. While an individual turbine or turbines may stop spinning, the output over an entire area in the aggregate tends to balance the load," says Charlie Smith executive director of the Utility Wind Integration Group.

One policy aid that could benefit renewable energy is the organization of markets into regional transmission organizations. Smith says wind integration has worked best in large geographic areas where a "balancing authority" can tap into areas where varying levels of electrical output have to be evened out. A consideration is the possibility of sudden ramping up or down of wind generation in a weather event. Handling large output variations and steep ramps are more challenging in smaller areas as a result.

As the percentage increase in generation capacity, an imperative is the improvement in wind forecasting. Well-functioning day-ahead and real-time markets are seen as a way of dealing with wind variability.

Newer Technologies

On the equipment side of the scale, newer technologies have helped reduce one of the drawbacks. National Wind Technology Center at the National Renewable Energy Laboratory Brian Parsons says: "The hardware is getting more grid-friendly. Perhaps the greatest example is in the old days if there was fault the entire system would go off. Now, low voltage raided through is developed into all hardware."

This has been encouraged, even mandated by the Federal Energy Regulatory Commission and National Electricity Reliability Corporation over the last couple years.

Many utilities now request that wind farms ride through grid disturbances, remaining on-line and continuing to support the system whereas before they had requested the wind farms trip. The solution the industry came up with is low voltage ride through, which allows the turbine to keep operating with a voltage drop of 10 percent. And it is becoming a requirement for new turbines connected to transmission.

Much of what the industry says it needs to do was laid out in its 20 percent by 2030 study coordinated by the Department of Energy

A recent study, conducted for Xcel Energy by EnerNex Corp., examined the cost of meeting 20 percent of electricity needs with wind energy on Xcel's Public Service Company of Colorado system. Studies in the U.S. and Europe have concluded there are no insurmountable technical barriers to the reliable integration of wind energy. The cost of adjusting power system operations to accommodate wind energy is typically low. Most studies have found that these costs are under $5 per megawatt-hour, or about 10 percent of the typical wholesale price of wind energy, according to the American Wind Energy Association.

Solar generation is largely confined to house rooftops with a few exceptions. As this source moves toward larger power plants, it will face many of the same obstacles as wind. One issue in the west is that large-scale megawatt projects require vast amount of land that most likely under the jurisdiction of the federal Bureau of Land Management and have lengthy and difficult site hearings and siting requirements.

"Photovoltaic, prior to 2006, was about 99 percent distributed and almost all of that less than a megawatt or two," says Mike Taylor of the Solar Electric Power Association. But now that California utilities have signed power purchase agreement contracts with developers of 200 megawatt projects, the transmission grid will face the same issues it has with wind projects.

Other challenges while it may not require the scale of large transmission projects to bring the output to market, it has the burden of being integrated into existing systems because so much of it is generated on the customer's side of the meter.

So whether it's a few kilowatts of solar energy coming from someone's rooftop, or a 1,000-megawatts wind plant contemplated by the Pickens Plan, integration of renewable energy sources by utilities will be part of the utilities agenda as they comply with new mandates and customer preferences.