Once a hopeful IPO candidate, solar thermal developer BrightSource has had two of its contracts cancelled this year. Last week BrightSource and PG&E mutually agreed to terminate an agreement for PG&E to buy solar from two 250 megawatt planned solar plants in Nevada.

It’s just very difficult for solar thermal developers right now, particularly as the technology has been somewhat of a work in progress (I read recently that an early Florida Power and Light solar thermal plant was designed to generate power for 11,000 homes but is only generating enough for 2,000.)

But really the biggest problem for solar thermal has been the plunging price of solar panels, a result of subsidies in China and depressed silicon prices. Utility scale solar installation actually grew by 134 percent last year, a sign of growing deployment of solar technology. But it’s been a challenge for solar thermal companies to capitalize on the growth.

The solution? BrightSource is trying to add energy storage technology to its projects, which would solve a key problem for utilities revolving around how to feed power to the grid when the sun isn’t shining. That would be a big competitive advantage for solar thermal but it also sounds like the kind of tech that will require a fair amount of R&D capital to perfect, something that’s in short supply right now from the venture community.