IN RESPONSE: The solar reliability gap

Tax incentives, subsidies make it easier for investors to embrace status quo.

NV Energy is struggling with a big challenge, as described by the Review-Journal’s July 23 editorial (“Promised green energy savings yet to materialize”). The utility must compensate for solar power’s biggest flaw: the night-time reliability gap. The proposed solution? NV Energy would spend $350 million — charge its customers $350 million — on natural gas turbines to deliver power at night, when solar power shuts down cold.

“Reliable power” has an industry definition. “Reliable” means “always available, 24-7.” Every second of every day. Solar power falls far short of the standard, with non-productive dark hours making it more expensive than it should be. For solar to deliver on its promise, the reliability gap must be closed, and the true cost of solar must be acknowledged.

Why is the reliability gap allowed to persist? More about that in a moment.

There are people working right now to close the reliability gap (I’m one of them). We’re trying to answer the question: Can stored solar energy be part of the solution?

Closing the reliability gap could be fairly uncomplicated, using a system that couples Nevada’s abundant solar resources with a geothermal booster. Clean and reliable geothermal has long been an underappreciated workhorse in our state’s energy portfolio.

The system works by collecting the sun’s energy with thermal solar panels and injecting the heat into underground aquifers, creating millions of gallons of hot water. This produces an “earth battery” — stored energy that can be tapped any time. When the sun stops shining, the hot water can be used to generate power.

The concept of using stored solar heat has been refined over many decades, and the technology is being adapted for this purpose now in Salt Wells. Fully developed, this renewable solar-plus-geothermal method will be useful far beyond Nevada.

For seven years I’ve evangelized renewable geothermal as the missing link for solar reliability. A new green project invites skepticism. If this is a real solution, people ask me, then why isn’t it already in use? Great question.

We — the team working to perfect the technology — suspect two main factors, Neither is related to practical potential. One is short-term decision-making that drives policy. The other is that solar’s true cost is hidden.

From the industry perspective, closing the gap would require power providers to think differently. It’s easier to put up solar panels, count the renewable energy credits and claim public praise for a job well done. Then later, introduce a separate project to address the reliability gap with natural gas turbines, which, however deficient, are a known quantity in the industry.

From the investor perspective, tax incentives and other subsidies make it tolerable to shrug off the reliability gap. Why insist on maximum performance when political pressure has created an easier path?

In a 24-7 world, our power sources must perform 24-7. We know the solar performance gap can be closed, and we hope proponents of clean, reliable energy will become more curious, and get involved in making it so.

Mark Hauenstein is a registered professional engineer, holds multiple patents in energy and grid solutions, and has represented independent geothermal power producers before the Nevada Public Utilities Commission.