DER - Storage

Batteries helped (mostly) as California’s grid endured record demand

Batteries helped (mostly) as California’s grid endured record demand
(Credit: AES)

As a power crunch precipitated by an extended heat wave eased, the California Solar and Storage Association (CALSSA) said that the state had more than 80,000 customer-sited batteries connected to the electric grid capable of providing 900 MW of solar power.

It said that while not all the batteries were set to discharge during the peak hours of 4pm-9pm on September 6, an estimated 76% were, capable of providing up to 684 MW of power at any given moment. The trade group said that 50% of these batteries’ aggregate power was put into use during peak hours.

But the Bloomberg news service reported that batteries also were discharging at times when they were not really needed. The mismatch diminished the power source when more critical demand periods arrived. A call for conservation made by the California Independent System Operator (CAISO) helped to cool demand and avoid widespread outages.

The news agency reported that a pricing mechanism used by CAISO triggered grid-connected batteries, rather pure demand levels. In at least one instance, batteries began discharging in the middle of the afternoon. Market prices had hit the storage-trigger level of $1,000/MWh, but solar and other resources were still in adequate supply.

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CALSSA said that consumer batteries charged by on-site solar panels can be pre-programmed to discharge at set times and on set days. It said the most common setting is for the battery to charge in the morning, and then discharge starting between 4-6 pm, depending on local utility rates and consumer settings.

CALSSA estimated that California utilities spent an extra $450 million in spot market purcahses on September 6, compared to a “normal” hot day. 

The group said that programs that operate distributed behind-the-meter batteries were proven effective during the hot spell. Several companies have arrays of batteries located on customer properties that also are enrolled in programs such as the Emergency Load Reduction Program. CALSSA said that Tesla, for example, had 4,500 consumer batteries that discharged 32 MW during peak hours on September 6.