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California to nearly double wind, solar energy output by 2020 -regulator

Nov 14 (Reuters) - California is set to nearly double its wind and solar power generation over the next seven years as utility companies try to meet the state's requirement to source 33 percent of energy from renewables by 2020, reliability regulators said.

The state is expected to add 8,000 megawatts of renewable energy by 2020 and needs to build or keep in service gas-fired power plants to cover changes in wind and solar availability, the North American Electric Reliability Corp (NERC) said in an assessment released on Wednesday.

NERC, the power reliability coordinator for the United States, Canada and parts of Mexico, worked with the California Independent System Operator (ISO), the state grid operator, to determine what the ISO is doing to integrate the new renewable plants and recommend steps to keep the system reliable.

As variable resources become a larger part of a system's resource mix - on the order of 20-30 percent - NERC said reliability services, such as frequency response, voltage control, transient stability, load-following and ramping capability can be impacted.

There are currently 10,700 MW of wind and solar power connected to the California ISO grid, which is expected to rise to 18,700 MW in 2020, according to the report.

One megawatt powers about 1,000 homes.

Fossil-fueled, large-scale hydro and nuclear power plants have traditionally provided electricity supply to the grid.

Unlike traditional power plants, which grid operators can run for as long as needed to meet demand, wind and solar facilities are generally only available when the wind is blowing or the sun is shining.

One of NERC's recommendations was for generators in California to build or keep in service flexible power plants like gas-fired units that can quickly ramp up and down in response to changes in renewable power output.

"Renewable generation provides a great basis for greening the grid and reducing the electric industry's greenhouse gas footprint," California ISO President and CEO Steve Berberich said in the statement.

"Their intermittency can be supported by a clean and flexible gas generation fleet, which California is currently transitioning to." he said.

Over the next decade or so, generating companies expect to build about 6,400 MW of new gas-fired generation in California, according to a Reuters survey.

The biggest power companies participating in the California electric market include units of Edison International, PG&E Corp, Sempra Energy, NRG Energy Inc , Dynegy Inc and AES Corp.