We all have heard about solar power.
And now comes concentrating solar power.
What exactly is concentrating solar power?
Concentrating solar power is just that – it concentrates sunlight onto a small area so that area gets exceptional amount of light and heat.
Such a high concentration of sunlight falling on a small area implies an enormous amount of light and heat falling on that small area. A simple way to understand concentrated sunlight is to recall an experiment many of you would have done as a child – use a lens to focus sunlight on paper, causing the piece of paper to burn!
For solar power plants, depending on the type of receivers/collectors on which the concentrated sunlight falls, either high-efficiency power or high temperature heat can be generated.
Concentrating Solar PV
If the concentrated sunlight falls on photovoltaic cells (usually done using special lenses to concentrate the sunlight onto the cells), it results in a much higher efficiency of sunlight conversion – much higher than the 20-odd % which is the highest as of mid-2016 for standard solar cells. Conversion of concentrated light into power is termed concentrating solar power (CPV) and in real life pilots, an efficiency of up to 35% has been reached.
CPV has the following advantages over conventional solar PV technologies:
- It requires less photovoltaic material to capture the same sunlight as conventional PV. As PV materials are expensive, this implies lower costs.
- It makes use of high-efficiency but multi-junction cells. While these may not be economically viable for large area capture that happen in traditional PV, use of expensive multi-junction cells becomes economically viable for concentrating PV owing to smaller space requirements.
Concentrating Solar Thermal (a subset is called Concentrating Solar Power or CSP)
Concentrated sunlight can also be used to generate significantly higher temperatures than can normal sunlight. When sunlight, concentrated through the use of reflectors (mirrors) or in some cases lenses, falls on a medium that can capture the heat, it can heat fluids to very high temperatures and enable the operation of a steam turbine – not very different from how steam at a conventional thermal power plant.
Conversion of concentrated heat into power is termed concentrating solar power (CSP). As it is more economical to store heat than electricity, some CSP power plants also come with a good amount of storage incorporated. These power plants can thus provide more “firm” (reliable) power than can conventional solar PV power plants can – well, solar PV power plants also can provide firm power if they use batteries, but batteries are a very expensive way of storing energy and hence are rarely, if ever, used in large scale solar farms.
Both CPV and CSP have their advantages over conventional solar power plants. As mentioned above, CPV results in much higher efficiency, while CSP provides more reliable power through the use of storage.
If you are wondering why, with such advantages, CSP and CPV have not yet grown into much larger markets, you are not alone.
To a certain extent it has to do with the relative immaturity of both the concentrating technologies when compared to a far more stable conventional solar PV technology. The other reason is the high cost of both these concentrating technologies.
While I have seen solar PV technology mature significantly over the past 5 years, and costs crash dramatically, I am yet to witness something similar for either CPV or CSP. These two concentrated technologies still are considered evolving, though CSP is relatively mature than CPV.
The result is that we see conventional, non-concentrated solar PV having a super growth worldwide, while the two concentrating technologies are pretty much idling currently.
I recall having at least 3 detailed business discussions in just the past 2 years with entrepreneurs from three different continents who had come up with some interesting concepts to make CPV more economically viable. Sadly, I am yet to see any of these ideas grow to a stage where they could be applied commercially.