Solar Energy Part 1

Solar Energy – Today and Tomorrow (I)


Solar Energy…. It has a nice ring to it, doesn’t it? The answer to humanity’s need for energy, limitless, perfectly clean, harness the awesome power of the sun… all sounds grand. As with most subjects, it is both right and off base.

Solar energy can be broken into two components, and we will look at each separately. Generating electricity from solar energy is called photovoltaics, or PV. Using the sun’s heat to generate useful energy we will call solar heating, SH.

Let’s look at PV, or photovoltaics first. Scientists are able to measure the solar energy which strikes the surface of the earth quite accurately. At our current rate of consumption, the solar energy falling on one half of Manitoba is enough to meet all of the worlds’ energy needs. So research is focussed on how to increase the output of PV cells, how and where to locate them, and how to store and distribute energy when the sun is not shining.

Many of you have, or have seen PV devices. You may know them as “solar powered”… the essential component is a small window, usually grey or blue, that converts light into electricity. Some calculators and watches have a PV cell to run them, and your local auto supply store sells panels which will recharge your car battery or run a small electronic device. Solar powered radios and patio lights are also popular. All those devices work because as a photon, a unit of light, strikes the treated silicon layer inside the cell, it knocks loose an electron. When you have enough loose electrons you soon have a usable electric current. The big problem with these devices is their efficiency, or rather lack of it. A PV cell, on a good day, converts only about 15% of the sunlight that strikes it into electricity. When you include clouds and atmospheric dust, you don’t get a lot of electricity out of your cell. On the good side, huge strides have been made in recent years to advance this and experimental efficiencies of over 40% have been demonstrated. This compares with nature’s efficiency of over 95% when converting sunlight to chemical energy using photosynthesis by plants

Scientists figure that in places where there is a lot of sun and electricity is expensive, such as Italy, California and parts of Japan, PV can compete with traditional generation methods within a decade. There is a working PV system near Springerville, Arizona, that covers an area of about 50 acres. It is built so that standard modules of about one acre in size can be added as needed, and it generates 4.6 megawatts, enough to power about 3900 homes, perhaps one third of Brockville. The best part is that it does this with no emissions whatever. Even with the low efficiency of PV, maintenance and wear and tear is minimal. In our part of Canada however, with relatively cheap electricity (about 6cents/kwh) and less sunshine, PV remains marginal, powering channel markers on the Seaway, for example.

The German government is encouraging PV development by allowing producers to sell PV power to the grid for up to three times the cost of electricity generated by conventional means. This is creating a boom in technological innovations in PV. A really cool development involves a PV cell that is created by a special version of an ink-jet printer, and is laid down on a flexible sheet only a millimetre thick.

The next issue with PV is that our need for electricity and the times the sun shines do not always match, so you have to have some kind of storage and backup system. Weight and space requirements for these can be considerable. Batteries to power your house for 24 hrs. or more would be as big as your kitchen stove. Current research is tending towards compressed air in which the PV system powers compressors when the sun is shining, and the compressed air drives a turbine when it is dark. Underground caverns previously used for natural gas storage are being considered to store the compressed air.

So, to get our moneys worth out of PV, and scale it up to make it economical, we can do either of two things… set up in a desert location, preferably near the equator, and take advantage of clearer skies and a more consistent solar angle, or hoist the whole thing into space.

As to putting the whole thing into space, there are obvious technical challenges associated with getting that much hardware up there, and assembling it, but it is technically possible. Increases in efficiency of factors of three to five are thought possible because of the lack of an interfering atmosphere and the ability of the panels to face the sun continuously. The power would be beamed back to receivers on Earth in the form of microwaves. If this project were to be started tomorrow we wouldn’t be seeing any “space-generated” electricity for at least twenty years, and then at a considerable cost, but largely pollution-free. Dozens of necessary shuttle launches may make this option less attractive. This or comparable plans are unlikely to be implemented until fossil fuels are in critical short supply.

PV is on the verge of huge growth, and we can expect to see a lot more of it in all areas of the globe over the next few years. Next week we will look at solar thermal power.