Canadian energy firm AltaGas has won a $45-million contract with Southern California Edison to build a 20-MW energy-storage system at its Pomona natural-gas-fired plant in Southern California. The project will be among the largest battery-storage facilities in North America when it comes on line in December, the company said. AltaGas owns six natural-gas-fired power plants in California. The Southern California Edison deal is its first for energy storage.