OREANDA-NEWS. The board of California's power grid agency rushed to approve tools to avoid potential power interruptions this summer as southern California deals with the loss of Aliso Canyon's natural gas storage capacity.

Without access to stored gas from SoCal Gas' 86 Bcf (2.4bn m?) Aliso Canyon underground facility near Los Angeles, supply problems are likely to disrupt electric service this summer for millions of southern California residents.

Power plants in the Los Angeles basin need more gas than is readily available in the SoCal pipeline system to ramp up electric output each afternoon to meet peak-hour demand as solar generation falls. Gas from storage usually fills that need.

But summer is the time SoCal conducts required inspections and pipeline maintenance, creating constraints on its system.

Four state agencies have warned that supply constraints created by summer demand and planned maintenance are very likely to disrupt electric service at least 14 days over the summer. SoCal Gas has warned that the gas system will be most challenged when the amount of gas burned differs from what customers have scheduled to burn, such as days when temperatures are hotter than forecast.

The tools, expected to be implemented after 1 June, are designed to give power grid operators more flexibility to dispatch generation based on daily changes in the gas market.

The new rules should also help owners of gas-fired generation in southern California recover rising gas costs and avoid costly penalties when SoCal Gas issues orders for tighter daily balancing.

Aliso Canyon represents 63pc of SoCal's storage capacity and 51pc of its daily withdrawal capacity. The facility supplies gas to 17 Los Angeles-area power plants with combined capacity of 9,800MW.

Under the changes, the ISO will be able to restrict generation in the Los Angeles basin area in the day-ahead market or in real-time when gas supply is limited. The ISO will reserve transfer capacity on the high-voltage transmission system so that electricity can be imported from northern California when Los Angeles-area power plants cannot meet local demand.

The grid operator will provide an advisory two days ahead of schedule so that market participants can better prepare for gas conditions, establish a day-ahead gas price index and allow generators to rebid commitment costs in the real-time market when gas prices change.

The ISO staff has been working with stakeholders since late March to identify areas of concern ahead of summer when gas use for power generation rises. Even with the tools, the ISO will have to "learn as we go," said Greg Cook, ISO director of market and infrastructure policy.

Owners of gas-fired power plants said they wanted more details on how the tools will work in practice and urged the ISO to commit to replacing these short-term provisions with market-based, fuel-cost recovery solutions before the winter season when additional gas supply for home heating will further tax the SoCal system if Aliso Canyon remains unavailable.

ISO board member Ashutosh Bhagwat said he sympathized with generators who will likely lose revenue until Aliso Canyon's future is determined. "This may be a long-term issue that needs to be addressed with a long-term solution," he said.

The ISO changes are temporary and will end on 30 November, the same date stricter gas rules being sought by SoCal Gas are set to expire.

Los Angeles-area generators include NRG Energy, Southern California Edison, the Los Angeles municipal utility and numerous smaller municipals.

The California Public Utilities Commission is considering SoCal's request for modifications to its existing high and low operational flow order (OFO) procedures to better balance supply on its system.