Our Solar Future

Solar energy is already in widespread use across the world. Yet, we clearly have a very long way to go before it reaches anything like it's full potential. It seems to me that the state of solar energy today is very similar to that of electricity as a whole, back in the Nineteenth Century.

The first electric currents to be produced and controlled by people came from chemical reactions. A device made to produce electric current by chemistry is known as a battery. But batteries were only the beginning of electricity as we know and use it today. The vast majority of the electric current that we use is generated in some way. These generation methods can range from hydroelectric dams to use of steam produced by a boiler to turn a magnet relative to a coil of wire so that the magnetic lines of force will move electrons in the wire, resulting in an electric current.

Solar energy is used today to produce electricity primarily by solar cells. As the term implies, these cells are compact devices which take in energy from the sun and use it to produce an electric current.

Solar cells have proven to be extremely useful in a wide variety of applications, including spacecraft. But solar cells have a lot more in common with batteries than that they both give us electricity. Just as batteries were only the beginning of electricity as we use it today, solar cells are only the beginning of the "Solar Revolution".

As useful as batteries have always been, they are useful only for small-scale applications. They are wonderful for vehicles and portable devices of all kinds, but we cannot possibly power a city, or an entire country, with batteries. Batteries gave us the experience and understanding to handle electricity as required for the electrical grids across the world, but those grids were not possible until large-scale ways were developed to generate electricity.

I find that the same is true of solar cells. As useful as they are, they are necessarily only the beginning in the same way as batteries once were. A fortune in solar energy falls on the roof of any large building, even in the winter. Yet, solar cells are just too expensive to make to be a practical solution to harvesting this energy, except on a very limited scale. Just as the development of our modern electrical grids required methods of large-scale generation, the harvesting of solar energy will require large-scale methods which go far beyond solar cells.

Countries vary widely in their attitudes toward, and use of, nuclear power to generate electricity. But it is often said of nuclear power that no matter how much science there seems to be involved in it's use, all that nuclear power really comes down to is just another way to boil water. The steam from boiling water is used to provide mechanical energy which turns a magnet inside a coil of wire to generate electricity. It makes no difference whatsoever whether the heat to boil the water comes from a coal boiler or from a nuclear reaction.

So, if any method of making large quantities of water boil can be used to generate electricity, what about the sun? There are solar reflectors which concentrate the sun's energy to cook a meal, or to cut through a piece of steel, why can't we just concentrate the energy from the sun to boil water? We could then generate vast amounts of electric current.

Everyone has seen how the rays of the sun can be concentrated to a point by a magnifying glass. Why can't the roof of a generator building be constructed as a lens in the same way? The entire roof could be made of glass or plastic panels, assembled so that they focus the energy of the sun to a point inside the building. The roof would not necessarily have to be circular, it could be rectangular and focus the sun to a line, rather than a point.

The solar energy would be focused on a boiler, which would then produce electricity in the same way as a boiler heated in any other way. If any of the roof panels was knocked out of alignment by wind, for example, they could be recalibrated. There could be a reflector on the side of the roof opposite the sun, to bring in even more energy. Heat is of longer wavelength, and is less precise than light, so it would not be that important whether or not the energy was brought to a sharp focus. Of course, the solar roof would have to be kept clean and snow-free.

It is true that the larger such a generating plant was, the more efficient it would be. This is simply because large boilers are more efficient than small boilers. A boiler inevitably loses some waste heat through it's surface area, and the volume is three-dimensional while the surface area is only two-dimensional. This means that the volume changes faster than the surface area as the boiler changes in size, so that a larger boiler has less surface area per volume, through which to lose heat, than a smaller boiler.

There are certainly other possible variations on the plan of a solar generating station. Instead of a roof, acting as a lens, the boiler could be installed over a concave mirror which would focus the energy of the sun on it.

There could be smaller-scale generating facilities as "solar bubbles", with a boiler and generator inside.

Perhaps the easiest and most practical design of all for harvesting the abundant energy that comes from the sun is a long pipe, suspended above the ground, with a concave reflector underneath it's entire length. The sun would shine on the reflector, which would focus it on the pipe. The pipe would naturally be dark in color (colour) to absorb the maximum amount of solar energy. The pipe could be set up in either a straight line, or the more likely twists and turns. Cold water would go in one end of the pipe, and boiling water would emerge from the other end. The boiling water would then be used to generate electricity.

But whichever design is used, it seems very clear that while solar energy can provide us with all the energy we need, we are in the same place now with solar cells as we were with batteries in the early days of electricity. Some method of large-scale generation is the next step.