United States

United States

Grids - Forecaster hired to boost integration

US: California's electricity grid operator has selected New York-based meteorological consultancy AWS Truewind to provide its weather forecasting services following a yearlong competition.

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The California Independent System Operator (CAISO) hopes the appointment will improve the state's ability to efficiently integrate the increasing amounts of renewables expected in the next few years.

In the forecasting competition, AWS Truewind showed it could provide a 20% improvement in forecasting wind energy production over a standard system last year. "With wind resources expected to double over the next five years or so, accurate forecasting is imperative to maximise the usage of these new green resources," says Debi Le Vine, CAISO's director of operations.

Considering capacity factor, California sees an average of 1GW of wind from the 2.8GW of installed projects connected to the grid, says Jim Blatchford, CAISO's senior policy issues representative. If the state were to reach its goal of deriving 33% of its energy from renewables by 2025, that represents another 26GW of renewables resources, with wind playing a large role.

Managing a mismatch

All this new variable electricity capacity will need to be accommodated to maximise the efficient balance of all electricity generation resources. The challenge with wind, says Blatchford, is that the California wind resource tends to be strongest at night, when electricity demand is low.

"We're concerned about electricity demand going up in the morning as wind comes off from its night cycle," says Blatchford. "So we have a little mismatch here, and we have to find out what's happening with wind so we can dispatch conventional generation."

Conventional generation power plants, usually gas plants in California, can take four to five hours to warm up to their operational levels and once there it is most efficient to keep them running. The state would like a more precise view of how much wind generation can be expected in the hours and days ahead so the grid operators can more efficiently balance resources.

Mismatches can be wasteful and Blatchford says that the spring months may provide an example. The winter in California has been a particularly wet and snowy one. In the spring a heavy snow pack will melt, putting hydroelectric dams into full service, and conventional generation will back off to accommodate the increased hydropower. But if wind generation picks up during this time of high demand, the power could be wasted.

"Then we have too much energy," Blatchford says. "This can be a problem where we're effectively giving energy away, or giving money to people to take power." During electricity oversupply, CAISO has market mechanisms to offload the power to heavy energy users.

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