Baseload (24/7) Solar is here!

The Andalucia region of Spain has developed many solar firsts: the world’s first commercial solar power tower (PS10), the largest (PS20), as well as the world’s first solar power plant that generates solar electricity past midnight.  Andalucia will soon add another first to that shiny list: the world’s first commercial baseload solar power plant.

Cobra’s (ACS Group) Andasol-1 plant near Granada, which officially went online in July 2009, is a 50-MW plantwith a 7.5 hours battery.  This ‘battery’, built by Spanish engineering giant Sener, consists of two tanks of molten salt thermal storage that helps the solar plant generate on-demand electricity in the evening, during rain or cloud cover.  Total plant production is about 280,000 GWh per year—about enough power for 170,000 people. (1)

Andasol’s capacity factor is 41%. That is, it can generate electricity 3,600 hours per year. For comparison, the Hoover Dam has a capacity factor of just about 23% while China’s Three Gorges hydro-electric power plant generates has a capacity factor of about 50%. (2)

Solar Salt Batteries

Molten salt energy storage (MSES) or ‘solar salt’ batteries are thermal not chemistry-based batteries (like Lithium-Ion).  MSES uses a combination 60% sodium nitrate and 40% potassium nitrate which retains 99% of the heat for up to 24 hours. Another way to put this number: this battery loses just 1% of the heat energy per day.

Potassium nitrate happens to be environmentally safer and cheaper than most chemical-based battery alternatives.(3)  In the Middle Ages, this ingredient was used to preserve food and it is still used in the production of corned beef. Potassium nitrate is also used in toothpaste (for sensitive teeth) as well as in garden fertilizers.(4)  MSES is also relatively cheap, clocking in at $50 to $100 per kWh, compared to about $1,000 for a Li-on battery.

24/7  Solar

Drive back to Seville on the Autovia del Sur (A-4 highway) and you’ll find the world’s first commercial large-scale baseload solar power plant: Gemasolar.

Built by Sener, Gemasolar is a 17-MW solar power tower plant with 15 hours of molten salt energy storage. Yes, a solar power plant that will deliver solar electricity round-the-clock: at 10 pm., at 1 am., and at 4 am.  Gemasolar is scheduled to open in about two months, according to former Sener USA President Jose Martin.

Gemasolar’s capacity factor is 75%. For comparison, the capacity factor of nuclear reactors in Japan, France, and the US were in the 65% to 72% range (in 2003) according to Clemson University Prof Michael Maloney .

Solar CSP has solved the energy storage challenge in an economical, elegant, and environmentally safe manner.  Round-the-clock (baseload) solar is here.


(1) “Solar Trillions – 7 Market and Investment Opportunities in the Emerging Clean-Energy Economy”, Tony Seba, January 2010,

(2) Wikipedia, Capacity factor,, as of Mar. 14, 2011

(3) “Solar Power and Salt Batteries,” Energy Matters, December 29, 2008,

(4) Potassium Nitrate, Wikipedia, , retrieved June 21, 2009

(5) Michael T. Maloney, “Analysis of Load Factors at Nuclear Power Plants”, , as of March 12, 2011

Skip to toolbar