Solar plus storage: Hybrid renewables become new normal in US

Last year was a bumper year for ‘hybrid’ power plants across the US, thanks to falling battery prices and the growth of varied renewable energy generation, according to a new report by the Lawrence Berkeley National Laboratory.

A hybrid plant is any power plant that combines either multiple different types of power generation (say wind and solar) or a combination of power generation and storage.

At the end of 2021 there were nearly 300 hybrid plants operating across the US, totalling nearly 36GW of generation capacity and 8.1GWh of energy storage, Berkeley says. That’s up 74 plants from the previous year, 67 of which combined PV (photovoltaic) energy generation plus energy storage.

For comparison, the US had a total of 1,143GW generation capacity at the end of 2021, meaning hybrid plants make up 3% of the country’s total capacity.

The report tracks and maps operational and proposed hybrid plants, in combination with synthesised data from power purchase agreements (PPAs). It excludes ‘virtual’ hybrids that are not co-located, as well as smaller plants with less than 1MW of generation capacity.

PV plus storage was the standout configuration for hybrid plants last year: PV plus storage plants hosted twice as much battery capacity as standalone storage plants (7GWh versus 3.5GWh, respectively).

These types of plants can be found across the breadth of the country, but major plants are found particularly in California and the West Coast, as well as Texas and Florida – no surprise in sunnier climes.

But despite the breakout performance of PV plus storage, there are nearly twenty other hybrid plant configurations making waves, including some that combine a fossil fuel component.

Interestingly, among the generator and storage hybrids, PV plus storage dominated in terms of plant number, storage capacity, storage to generator capacity ratio and storage duration.

That suggests that the PV plus storage plants are providing both resource adequacy (keeping the grid stable even during periods of renewable intermittency), and enough power for energy arbitrage (the buying of power during off-peak hours to bolster energy provision during expensive peak hours).

And data on plants under development suggests the trend of hybridisation is likely to continue: the report found that at the end of 2021 there were more than 670GW of energy from solar plants in the nation’s queues, 42% of which would come from hybrids. For wind, 247GW of capacity was waiting in the queue, just 8% of which would come from hybrids, most often wind plus storage.

There’s a caveat here, though, because many proposed plants never make it to commercial operation.

The report also found that while PV plus storage PPAs are falling in cost over time, levelised storage costs have recently increased, which may reflect both the higher ratio of batteries to PV capacity, as well as the growing global supply-chain crisis.

Though Australia lags behind on hybrid plants, capacity is touted to grow: production began at the country’s biggest hybrid facility, the Port Augusta Renewable Energy Park, in April this year, while the Asian Renewable Energy Hub, a proposed mega-plant that could supply the equivalent of 40% of Australia’s overall electricity generation, is still in its planning phase, with fuel giant BP taking a 40.5% shareholding in the project.