SAY solar power” and everyone thinks of photovoltaic cells, and investing in these would be a boon to the world – we would live in a different planet now if most people did that back in the 1970s, when we had used up a sixth of the world’s oil rather than half.
No matter how much we think we know the advantages of solar, it’s useful to run through them again – unlike oil, coal or peat, solar energy is not diminished by its harvesting; no matter how much we take today, there is still the same amount left tomorrow. Every day, enough energy falls on the Earth’s surface to supply all our energy needs for four to five years.
Unlike most sources of electricity, they use no fossil fuels and create no greenhouse gas emissions, beyond the panels’ initial manufacture, and an average home-sized solar panel will save 11 tonnes of carbon dioxide each year from adding to climate chaos. This does not even count the additional solar power we receive from wind, waves or rain into rivers, any of which can also generate electricity.
One potential problem with photovoltaics, though is that they require exotic metals that must be mined and shipped around the world, and whose supply might be limited. Even if we encounter supply problems with these, however, there are still Stirling engines, which really deserve their own article. Stirling engines focus the sun’s rays with mirrors on a target, usually to boil water to power a turbine the way a nuclear plant does.
One of the simplest ways of using solar power , however, requires little technology — you merely face your doors and windows south (or north in the Southern Hemisphere), or build a conservatory, and let the sun warm your home.
Especially in areas where the weather swings between hot and cold temperatures – say, in Spain – some people build a thick wall in their house to separate the conservatory from the rest of the home. It’s called a trombe wall, and its purpose is not protection, but to regulate heat – in the heat of the day the sun pours through the conservatory and bakes the cool stone until hot, and in the cool winter the hot stone radiates the heat through the house again.
The most effective kind of solar power we can use in our area, though, is probably through hot-water panels; glass or plastic boxes on your roof house darkly-coloured water pipes, inside which the water warms naturally.
In a “close-coupled” solar water heating system, a water storage tank is set right by the solar collectors on the roof, and the change in temperature automatically makes the water flow without pumps. Other systems pump the hot water collected in the pipes down into a water tank.
Sun-heated water can be used with a regular heating system, not to replace it entirely but to augment some of the power. When you shower, you might get the hot water from the solar panels first, after which the boiler takes over. The main time you need a boiler or central heating, however, will be at night when the need is less anyway. Therefore, solar water heating for washing and bathing is often a better application than central heating because supply and demand are better matched. In many climates, a solar hot water system can provide up to 85% of domestic hot water energy. In many northern European countries, systems that combine solar water heaters and space heaters provide 15 to 25% of home heating energy.
A recent report from the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety found that Europe could cut its greenhouse gas emissions by 70 per cent if everyone switched over to solar power — and that includes countries like Ireland or Finland, where it is often said that solar power is not feasible. They also noted that the cost of collecting solar thermal energy equivalent to one barrel of oil is often less than the price of oil these days — although that jumps around from week to week — and is likely to go down further as demand increases and technology improves.
I don’t want us to talk about “clean energy” as a blanket solution for everything; for example, they do not generate liquid fuels. But much of the world’s electricity comes from fossil fuels, and clean energy could free up the remaining oil and gas for other things we might need – buses, trains, tractors and manufacturing – including manufacturing solar panels, until someone finally creates a solar-powered solar-panel factory.