The BP-backed solar developer Lightsource sees a very compelling case for deploying energy storage in the Western U.S.

All major utility-scale solar developers have added storage development talent, and some have begun regularly bidding on combined projects. But few have actually won bids for, much less constructed, hybrid plants. That makes it hard to determine just how central that kind of project is to their business models.

Not so with Lightsource, the largest European solar developer, which launched its U.S. branch last year and soon after received $200 million from oil and gas giant BP in exchange for a 43 percent ownership stake.

North America Chief Commercial Officer Katherine Ryzhaya affirmed the company's view on storage in a keynote interview at GTM's Solar Summit in San Diego last week.

"For a utility-scale solar developer, we’re not putting forward any proposals without storage, currently, to anybody west of the Colorado," she said. "Every utility process, every bilateral at this point, at least on the West Coast, is looking at solar-storage hybrids."

The American West enjoys a considerable solar resource, such that states like California and Arizona are starting to worry about a surfeit of solar on the grid at midday, with steep ramp requirements to meet peak demand in the evenings.

That dynamic has driven groundbreaking solar and storage contracts, like the NextEra project for Tucson Electric Power and the First Solar plant to deliver evening power to Arizona Public Service (the cartographically inclined may counter that most of Arizona lies east of the Colorado River, but it does sit west of the river's source in the Rockies, so I'm going to count it for the purposes of this article).

So far, though, developers have kept their commitment to dispatchable solar more vague than "every proposal in the West."

Co-location isn't strictly necessary; on an interconnected grid, an offsite battery can store surplus solar power. Developing both resources together, however, creates savings on interconnection and installation costs, and improves system efficiency through DC coupling, which simplifies the power conversion process.

In grids with extremely high solar penetration, though, adding any new solar can disturb the balance of grid operations. Hawaiian islands have reached that point, turning to solar self-consumption for new rooftop solar customers and utility-scale solar-plus-storage on Kauai.

The aggressive use of energy storage follows from Lightsource's strategy of customer-driven project development.

Traditionally, solar developers would start by nabbing a site and securing interconnection, then look around for an offtaker, Ryzhaya said. That worked fine in the early days when renewable portfolio standards and PURPA contracts drove most large-scale solar deals.

"You could almost think of a PPA as the last of the three pillars of development: If you had a great site and you had an interconnection, of course you were going to get a PPA," she said. "I don’t think that’s the world we’re dealing in today. Today, it’s entirely flipped: It’s a customer-led business."

The old way prioritized least-cost development; under the customer-driven mentality, Lightsource crafts projects tailored to specific customer needs. Such a perspective is more amenable to the higher cost inclusion of storage, provided that it solves a problem that standalone solar can't.

Lightsource tracks the retirement of conventional power plants, Ryzhaya said, and seeks opportunities to backfill that gap with solar and storage. This combination is particularly attractive when plants retire in dense urban load pockets, where permitting a new gas plant would be exceptionally difficult.

The company isn't solely looking at the Western markets. It recently signed a 25-year power-purchase deal for a 20-megawatt solar farm in Kansas, slated to be the largest solar farm in the state.

In the absence of policy drivers for clean energy, the utility customer Mid-Kansas Electric Company chose the solar plant to relieve some of the peak congestion on an overloaded transmission line.

"We’re going to places like Kentucky and Kansas and Tennessee, and we’re putting in solar numbers that they haven’t seen," Ryzhaya said. "They still think solar costs $100 per megawatt-hour in a PPA, and we’re showing them numbers that are competitive on day one, not to mention over a 20-year term, and not to mention that there is virtually no opex; there is no fuel risk. It’s really eye-opening for customers."

In many markets, storage economics still don't pan out. As a result, Lightsource is exploring alternatives. Specifically, the company is working with BP to create a synthetic firmed solar product, Ryzhaya noted. This would leverage BP's energy trading desk to deliver load-following energy to a customer.