Of all the solar technologies, the one least talked about in financial markets is thermal. When mentioned, solar thermal is usually followed by a long list of ‘inconvenient truths’ such as that plants are complex and take too long to build, that land is a problem, mirrors must be cleaned and can break, and that heat stored as molten salt will turn to stone and destroy the plant. Perhaps the greatest canard of all is that energy efficiency is low relative to costs.
We came away from Andasol 3, the third of three plants built successively, each one better than the last, realizing that misconceptions were rife. This technology is not new. As far back as 1911, parabolic mirrors were being tested in Cairo, Egypt and in Pennsylvania. The use of conventional power blocks and energy capture with mirrors is technology that has been around a long time and yet only today is its extraordinary potential being realized.
Solar Millennium is turning out standardized solar thermal plants, replicating Andasol-type solar storage across the globe. The Blythe project in California and Desertec in North Africa are enormous projects but there are many smaller ones. And the time to build one is being reduced exponentially. Completion of one plant the size of Andasol 3 today takes just 24 months but is projected to take 18 months in the near future.
Amortization of the power used to build a thermal plant is short, 5 months versus 2-5 years for PV. A 100MW plant costs 340ME, cheap for its size and speed if compared to conventional power and obviously much cheaper than PV farms.
Land is not an issue, especially when plants can be built on uninhabited land with little agricultural potential or in deserts where absolutely nothing can grow. Aesthetics are also less of an issue as the mirrors are far less obtrusive than wind turbines or a field of PV panels.
Andasol mirrors do not require systematic cleaning and are difficult to break. Mirrors are made of tempered glass and can resist sand storms and gale winds (in sleeping position).
Insulation of the pipes and salt tank keeps the salt at an optimum 385°C for 45 days in the event of turbine failure.
Efficiencies, while already good: 50% average annual for the solar field, 30% for the turbine circuit, and 15% annual average and 28% peak for the entire plant, are bound to improve with technology upgrades as plants proliferate. The turbine at Andasol 3 is 10% more efficient than turbines at Andersol 1 and Andasol 2. That efficiency improvement took just 2 years to achieve.
Andasol’s total investment cost was 310M€ or cost/kwh of 1.73€/kwh. Spanish government funding (offering a choice: fixed tariff or premium plus market price, both guaranteed for 25 years) has made solar thermal an extremely attractive investment proposition.
With solar thermal costs forecast to fall 50% by 2025 and total MW produced projected to increase from 2500 MW last year to 25,000 MW , the future of this technology is boundless.