In 2008 I published an essay called Solar Solutions that predicted the rapid rise in importance of solar power, and especially concentrating solar thermal power (CSP). Photovoltaic panels have seen exponential growth over these last few years, and now CSP is starting to take off. The early pioneering SEGS system in Southern California developed in the 1970’s and 80’s proved the technology worked. Spain made huge strides forward during the first years of this millennium, until the Rajoy government abandoned support. On this blog in February 2013 I posed the question, where next for CSP, and listed a number of countries where it was likely to be developed. Progress has been made in several countries, notably Morocco, Chile and South Africa. I’ve written before about projects in Morocco and Chile, so today I’d just like to highlight some of what is going on with CSP in South Africa.
South Africa has many problems, from corruption to unemployment. At 9.3 tonnes it has high per capita carbon emissions, especially given the low standard of living of most of its people, the lack of any electricity for many people and the frequency of power cuts for those who are connected to the grid. It has many old inefficient and polluting coal fired power stations that need to be closed down. However it has considerable renewable energy potential, and a new wave of investment. The hot arid lands of the Northern Cape Provence are seeing a cluster of half a dozen or so new CSP projects being built. It is two of these I’d like to highlight.
In March this year Bokpoort started production. It’s a 50MW parabolic trough system. What makes this system remarkable is the large thermal storage capacity, meaning it can produce electricity at full load for 9.3 hours after the sun has set. This means 24 hour per day generation is possible, but in practice it is the key evening and early morning times of high demand that will be covered, as well of course all the hours that the sun is shining.
The above picture shows Redstone, which is currently under construction. It is a 100 MW system using heliostats and a central receiver tower, and will have 12 hours of thermal storage capacity. Alongside it are the 75 MW Lesedi and 96 MW Jasper photovoltaic systems, giving the total solar park a generating capacity of 271 MW. Lesedi and Jasper photovoltaic systems will produce electricity when the sun is shining and the Redstone CSP plant can flexibly increase production to cover the early morning and evening periods. This combination of CSP and PV is proving cost effective and suitable to match energy demand, if as in these examples sufficient thermal storage capacity is added.
In both these examples, Redstone and Bokpoort, giant insulated tanks full of molten salt are heated in the day so that after the sun has set water can be converted to steam to drive turbines and so create solar electricity through the night. It is this thermal storage that gives CSP a great advantage over PV or other renewables, and why we will see very many more of these CSP with storage systems in many of the world’s hot arid lands over the coming years.