Concentrated Solar Power (CSP): the energy for the future

Solar energy is the most abundant energy resource on earth. Its main worth and value is that it represents the key to the solution regarding the decarbonization of our energy system. So, the question is, what is preventing us from fully developing Concentrated Solar Power?

In fact, access to clean, affordable, abundant and reliable energy is the cornerstone of global economic prosperity and growth. However, energy is not merely a random or « variable» fueling of a technical system. The choice of energy source is necessarily a social responsibility, which involves relevant institutions, – including  political, economic and social systems, and most especially the citizens who are involved in this decision making  with its adherent consequences.

In 2008, the physicist Joseph. J. Romm wrote an article entitled “The technology that will save humanity” and described Concentrated Solar Power (CSP) as  the one best suited to generate clean electricity for generations to come. But how does it work?  Let us consider…


Solar Energy

Solar energy, as mentioned above, is the most reliable and available energy resource on earth, with about 885 million terawatt hours (TWh) reaching the planet’s surface each year. This energy comes from the thermonuclear reactions that occur in the sun, causing the emission of very high-powered electromagnetic radiation. It is then partially reflected and absorbed by the atmosphere, so that the radiation received on the ground has both a direct part and a diffuse part.

It is estimated that solar radiation reaching the Earth’s surface varies between 200 W / m2 per cloudy sky and 1 kW / m2 in clear conditions when the sun is near its zenith. But only the direct radiation of the sun makes it possible to obtain exploitable temperatures  in order to produce electricity thermodynamically i.e. the diffuse radiation not being able to be focused. At present, it is possible to convert solar energy into two forms: heat – in the form of thermal energy – or directly into electricity thanks to solar photovoltaic technology.

The principle of solar thermodynamics is to convert solar energy into heat, then into electricity as a secondary consequence. The concentration of solar radiation at the origin of heat production is effected by means of optical concentration devices. The solar thermal electricity thus produced and injected into the network – solar thermal electricity (STE) – is decarbonized, renewable and available in infinite quantities.


Concentrated Solar Power Technologies

The first CSP plant in Europe – Thémis – was built in France in 1983 in the  region of the Pyrénées Orientales. An International reference in terms of conversion of solar energy by thermodynamics, the research was however abandoned in favor of the “all nuclear” plan in France,  with a view to restart a few years later…

Any unit for  thermodynamically converting solar energy is therefore schematically composed of similar elements: an optical device for concentrating solar radiation re: the input of the receiver; a heat generating system composed of another receiver – a form of transport medium affecting heat transfer fluid and optionally  as a storage means; then a subsystem for converting heat into electricity by a thermodynamic cycle associated with an alternator. Each of these processes is distinguished by its geometry, its temperature of use as well as its optical and thermal performance and costs.

Today there are in existence four main types of devices ready for the industrial production of thermal electricity:

  • The Parabolic Trough
  • The Central Receiver or Tower plants
  • The Linear Fresnel Reflector


The most impressive ones, if one is to go by their futuristic looks, are Tower power plants. In the US, SolarReserve is currently developing the biggest plant ever designed (see cover picture of this acticle). The Sandstone project: 2000 MW of installed power, which could supply electricity to 1 Million homes without using any fossil fuel, and with a storage capacity of 10h, to be able to  be produced even when the sun is set.


Added values of the CSP

The capacity of solar thermodynamics to store energy in the form of heat is one of the major points of differentiation of this concept compared to other renewable energies. As wind power or solar photovoltaic power develops, always marked by the intermittency of their production, concentrated solar thermodynamics is positioned as the mode of production of renewable energy able to fill this void by offering a reliable and redistributable energy capacity on demand. The storage, the hybridization and / or the combination of the two allow solar thermal electricity to be competitive on the grid with other forms of energy that can meet the same criteria for use: starting with natural gas.

Disruptive, concentrated thermodynamic solar technology is a source of great hope. The futuristic paces of the plants speak for themselves. Renewable by nature and decarbonized, this technology is an indispensable asset for the transition of our energy systems. The various uses attributed to it allows us to imagine its total integration: as much on a large scale to meet an exponentially growing demand in the industry of tomorrow as to help decarbonize this sector and hopefully to finally achieve an ecological industry.

The European Union has all the resources and tools at its disposal to promote its integration: be it in the South of Europe or pushing the boundaries of the internal market in order to consider collaboration with the regions of North Africa. On this subject, it is a moot question as to whether it will be a simple commercial opportunity or the establishment of a real cooperation, with a goal to a real sharing of the resource that we all have in common: the Sun.

A propos de Marion LEMOIGNE

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