Big solar with storage - a very happy birthday

Santiago Arias and his team at Torresol Energy should be congratulated for the dream run that their baby, the world's first baseload solar thermal plant, has been having since it started full operations two years ago. The plant has sold more electricity supplied to the Spanish national grid than it was ever designed to deliver.

The plant was built by Abu Dhabi state-backed renewable energy investment vehicle Masdar and SENER, Spain's leading aerospace engineering company. The plant, one of the great engineering wonders of the modern world, was inaugurated by the King of Spain Juan Carlos I and Sheikh Mohamed bin Zayed Al Nahyan, Crown Prince of Abu Dhabi, showing the cooperation between the two countries on the project.

The Gemasolar solar power tower is the most automated concentrating solar thermal plant in the world and it relies heavily on the control systems developed by the aerospace engineering company that designed it.

Prior to commissioning two years ago the plant underwent a testing and calibration phase where some final issues with the plant's automation and operations were resolved. The remaining issues were with regard to the cooling effect of heavy wind across the receiver surface. Once this was solved and dealt with and other production and process issues ironed out the plant has been able to consistently dispatch more electricity than was expected in the design phase, a boon to bankers and investors and a huge thumbs up for the technology.

Under the hood

Doing the grunt work at the top of the central tower is the receiver that takes all the light energy from the 2500 mirrors and converts it to heat. The receiver is made of the super-alloy Inconel, which is used in jet engines. There were really only two companies in the world that had the know-how to build this, and they both carry the weight of the world's airlines. SENER chose the company closest to home, British firm Rolls Royce, to partner on this most important part of the production chain.

The molten salt storage systems of most of the world's solar thermal plants have been built and/or designed by SENER. With Gemasolar, the temperatures being dealt with have increased to 565 degrees from the 400 degrees in most other plants. In order to cater for this, the hot tank was upgraded to a stainless steel tank rather than just a basic carbon steel tank, and a number of other components had to be redesigned and/or sourced for higher temperature operation.

Where to now?

Gemasolar was an expensive project if you ignore the fact that it was the first of a kind molten salt power tower. However, the learnings from this first effort have achieved a dramatic cost reduction in future plants. The next solar tower with molten salt, being constructed by SENER’s main competitor Solar Reserve, is shaping up to be more than 30 per cent cheaper per unit of electricity generated. 

As the cost of solar photovoltaics (without storage) have plummeted, the value proposition in solar thermal plants is in their ready storage capability and the flexibility that delivers in plant operation of being a peaker, intermediate or baseload.

Although new projects in Spain have stalled due to the conservative government's war on renewables, there is some good news for the progression of the technology in the Middle East, South Africa and the US. The main problem at the moment with these new entrant countries is their focus on older, less scaleable and more costly trough plants. SENER has been picking up some of these contracts but really needs more power tower projects to get the technology well down the cost curve.

Let’s hope to see something in China, the Middle East or Africa soon. Or even better, in Australia. Our economy is strong, the solar resource is excellent, and the capability of our engineers and scientists and electricity supply industry is such that a baseload solar tower would integrate nicely.

SENER/Torresol Energy's next move will be to build a molten salt power tower with a receiver at twice the capacity of the current one, at least 250MWth, and they could do that here in Australia with a little Direct Action from Prime Minister Tony Abbott, Environment Minister Greg Hunt and Industry Minister Ian Macfarlane.

Matthew Wright is the executive director of Zero Emissions Australia.