Gas and Solar to Ease California Hydro Shortage, Says CAISO

Substantial new gas-fired and solar generation that have been added to the California grid over the past year are expected to take up the slack this summer as an ongoing severe drought has led to substantial limitations on hydroelectric generation, according the summer 2014 assessment from the California Independent System Operator (CAISO).

According to the California Department of Water Resources, 2014 is shaping up as one of the driest years on record. Statewide hydrological conditions are well below normal: snowpack in the Sierra Nevada mountains, which serves as a key water resource during the summer, is currently at 19% of historical average, while state reservoir storage is at 63% of average and far below capacity.

The result, according to the CAISO assessment, is that at least 1,370 MW of hydroelectric capacity will be unavailable this summer, with potentially as much as 1,669 MW offline. In addition, limitations on cooling water withdrawals may lead to the shutdown of up to 1,150 MW of thermal capacity.

This challenge comes on the heels of last year’s early retirement of the San Onofre Nuclear Generating Station, which took another 2,200 MW of capacity off the grid.

Despite all this, CAISO says it should be able to maintain a healthy 23.8% reserve margin this summer as a result of more than 3,500 MW of new grid-scale capacity the state has added since last summer. Of this, about two-thirds is solar and most of the rest is natural gas–fired. The assessment dryly notes, “It is worth mentioning that the operating reserve margin projected for 2014 is the second largest in the past ten years.”

California led the nation in both new gas-fired and new solar capacity in 2013, according to the Energy Information Administration (EIA). The state added 2,621 MW of solar (counting both grid-scale and residential) last year, with several large solar plants coming online in the past few months, such as the 392-MW Ivanpah concentrating solar plant near Las Vegas and the 250-MW California Valley Solar Ranch. It also added more than 4 GW of gas-fired capacity in 2013, according to EIA data, with six new combined cycle plants being commissioned last year.

Peak summer demand in CAISO is expected to hit 47,351 MW, with 53,950 MW of net qualifying capacity available.

—Thomas W. Overton is a POWER associate editor (@thomas_overton, @POWERmagazine)

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