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Introduction
One must not believe, despite the silence of modern writings, that the idea of using solar heat for mechanical operations is recent. On the contrary, one must recognize that this idea is very ancient and its slow development across the centuries has given birth to various curious devices. Augustin Bernard Mouchot, at the Universal Exposition, Paris, France, after demonstrating a solar-powered device that made ice (1878).
Eventually industry will no longer find in Europe the resources to satisfy its prodigious expansion... Coal will undoubtedly be used up. What will industry do then? Augustin Bernard Mouchot, after demonstrating an early industrial application of solar thermal energy (1880).
Figure 1.1 The sun.
Source: Wikimedia Commons
Augustin Mouchot was an exceptional pioneer of solar power who invented the first solar-powered engines 150 years ago (Figures 1.2 and 1.3). Since then, our knowledge of how to exploit the power of the sun has increased by leaps and bounds, especially in the last 50 years. Nowadays, with the reality of climate change upon us, it seems that almost every week we are learning about a new way to exploit the incredible amount of solar energy that falls upon our planet every day.
From massive solar power stations in the northern Sahara that may soon help provide Europe with its energy needs, to houses that donât need any heating or cooling (Passivhaus); from a solar-powered iPhone case/charger, to a power station that uses phase-changing materials to let the sun run our homes, even at night; from an electric car with solar panels on the roof to help save fuel, to a solar-powered ski jacket; all of these innovations and many more are coming over our event horizon. Like the rising sun, they herald a potential new dawn for our energy-guzzling world, if only it can wean itself off dirty fossil fuels and high risk nuclear energy that both bring with them massive environmental hazards. Unlike them, the freely available power source of solar energy is everywhere, brings no dangerous pollution, and will last longer than the human race.
The sunshine we receive every day could provide more than enough power for our global needs, even with a bigger population in the future. We can learn to heat and cool our buildings without the need for electric heating or cooling devices, as the Romans did. We can capture the sunâs heat in solar water heating panels to provide hot water. We can use its light to make electricity in photoelectric solar panels. We can even copy what nature itself does to make plants grow, by employing its light energy in photosynthesis to provide for our needs. This book is about many of todayâs realities and the opportunities which together will help to save us from the threat of climate change. It will explain how there are two kinds of solar panels: those that heat water and those that generate electricity. And it will offer a good overview of the potential and various applications of solar technologies anywhere around the world. But as with every discipline thatâs worth knowing about, there are a few basic technical concepts to take on board.
Figure 1.2 French solar pioneer Augustin Mouchot (1825â1912).
Each chapter contains a section on the history of each technology. Several thought-provoking ideas emerge from this. First, itâs interesting how instrumental the French have been in the development of solar power â from Antoine Lavoisier, Augustin Mouchot, Abel Pifre and Felix Trombe right up to the developers of the new solar-powered aeroplanes and blimps. Even more interesting is the way in which solar technology has proceeded in leaps and bounds over the last three centuries, and at several points been abandoned in favour of coal or oil. This happened with concentrating solar power stations in 1914, and solar thermal water heaters in America in the 1930s, to cite but two examples. It is as if it has constantly been on the edge of a breakthrough as the worldâs principal source of energy, and if it hadnât been for the abundant supply of cheap oil, it would be much more widespread today. The abundance of fossil fuels in the crust of the Earth has propelled human development in the last 200 years, but has brought us to a point of crisis because of climate change. Consider if there had been less of this fuel bequeathed to the human race: suppose it had, for instance, run out in 1914 â we would now be well into the solar age. Consider again if it had run out in the 1970s â then we wouldnât be arguing now about whether human activities have caused climate change. Whether the solar age finally comes in the next 10 years, or much later in this century, there is no doubt that it will come. And it is to the pioneers named in these pages that future generations will owe a huge debt.
Figure 1.3 On 6 August 1882 this printing press produced copies of Le Chaleur Solaire (Solar Heat) by Augustin Mouchot, a newspaper that he created in the Tuileries Gardens, Paris, for the festival of LâUnion Francaises de la Jeuenesse. It printed 500 copies an hour, using solar thermal technology.
Source: Corbis
The range of technologies
There is far more solar energy potentially available than we could ever use, but the problem with collecting it on a large scale is that it is not especially concentrated. We would need a big area of the Earthâs surface to capture enough to convert it into electricity for all our needs. In fact, someone has calculated it would require around 1 million km2 (386, 102mi2) of land surface. Matthias Loster at the Department of Physics, University of California, worked out that this amount of land could in theory be deployed at six sites around the globe: the Sahara; the Great Sandy Desert in Australia; Takla Makan in China; Iraq/Kuwait; the Atacama Desert in South America; and the Great Basin of the US (Figure 1.4). Together these installations could produce 18TWe, the worldâs total primary energy supply in 2006 using current levels of technology. He assumed panels with a conversion efficiency from incident sunlight to electricity of 8 per cent. One project â Desertec â is already under way in the Sahara to
Figure 1.4 Itâs been calculated that solar power stations in just six of the hottest sites on the worldâs surface (black dots) could harvest enough energy for all our needs: 18 terawatts. The colours represent the amount of solar energy hitting the Earthâs surface in W/m2 averaged out over the year, indicated by the scale below the map.
Source: www.ez2c.de/ml/solar_land_area © Matthias Loster
build such an installation to supply Europe â except that it doesnât expect to use photovoltaic (PV) technology but concentrated solar power. This focuses direct sunlight onto a type of heat engine that is used to produce electricity.
For solar PV is just one of many solar technologies. This book will systematically examine them all:
- passive solar architecture;
- solar water heating;
- solar thermal electricity generation;
- photovoltaic electricity generation.
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