One of the big questions about solar power is how to supply sun-driven electricity at times of peak demand. Demand spikes in the early morning, before the sun is high enough to hit solar panels, and in the early evening, when solar panels operate at only at half efficiency in the low light. Cost-effective storage has been a major issue to be solved.
Electric batteries have been used, but they’re expensive and have a limited lifetime, so they are usually online to even out a plant’s production, not to store large amounts of solar energy overnight.
Now, Solana, a $2 billion solar project near Phoenix, is pioneering a new method of solar storage. A network of mirrors focuses sunlight onto black-painted pipes, which carry heat to tanks of molten salt. At night, the plant draws heat out of the molten salt to continue making steam and electricity. Solana gathers heat almost twice as fast as its steam turbines can use it, so on a sunny day, the plant turns out power steadily.
Its production can be throttled back at hours when photovoltaic cells are producing current, or at night, when demand is low. Arizona Public Service buys 100 percent of Solana’s power and decides when to use it. Another project in California, Ivanpah, has developed a similar means of solar storage. It uses a field of mirrors mounted on pillars to focus sunlight on a black tower, which reaches very high temperatures and from which heat can be drawn.
These solutions to solar power storage are so promising that last week the California Public Utilities Commission approved a rule that requires the state’s three big investor-owned utilities to install solar storage by 2024. That’s real progress toward renewable energy as the power of the future.
Article by John Howell, appearing courtesy 3BL Media.