Electricity stored in new industrial-scale batteries at Belco will provide a back-up system that can deliver ten megawatts of power at a moment’s notice.

It is believed that could be enough energy to power about 6,500 households, based on US data. The battery supply can be discharged for up to 30 minutes.

The power stored in the lithium-ion batteries would automatically kick in to the grid within 50 milliseconds, three times faster that a standard back-up engine, which Belco said will “help to avoid the load shedding often associated with such events”.

Reserve capacity is needed to maintain power-generating stability during emergency operating conditions and unforeseen load swings.

Belco said the battery energy storage system is part of its capital plan to reduce costs and ensure a more reliable energy supply. It is estimated there will be a $2 million saving on fuel and maintenance costs by using the batteries rather than running reserve engines that are not adding power to the grid, but can do at a moment’s notice.

The batteries have a 20-year lifespan and are recyclable. They are housed in six containers and weigh approximately 100 tonnes in total.

The battery energy storage system includes four transformers and power conversion system equipment. The entire facility covers an area of 2,000 sq ft.

Stephanie Simons, Belco mechanical engineer, said: “The Bess facility is an important project for Belco that will have many benefits including a more reliable system, less wear and tear on our engines and, most importantly, savings on fuel and maintenance costs of approximately $2 million.

“The investment in the project is expected to be paid off in four years and the batteries are built to last for 20 years. This is just one part of our capital plan that will ensure reliable and cost-effective electricity for our customers for many years to come.”

Belco tendered the design and building of the Bess facility and chose Saft, a subsidiary of Total.