Some renewable energy claims are just absurd when you stop to think about them.
From a pro- solar energy article:
“According to [a developer in Spain], just 2% of the solar radiation that falls on the world’s deserts would supply all the planets power demands.” That sounds good, doesn’t it? Well, let’s do some figuring. First of all, how big are the world’s deserts? A bit of Google searching suggests around 20% of the world’s land area. I’m not sure if that includes Antarctica, which is considered desert, and which is too remote to be used as a photovoltaic outpost, but let’s just ignore details for now. Two percent of 20% of the world’s land area is about 2,300,000 square miles, which is equivalent in size to a country somewhere between India and Australia. So according to the article, this much area could provide all of the planet’s power needs. (Though I point out that it would have to be spread around the globe well enough to account for the lack of sun and therefore electricity at night. Details again.)
Now it might seem okay to swallow the supposed need to cover such a large area of the planet with photovoltaics or focused collector systems, since we DO need electricity. Generating it with solar collectors produces no pollution except in the manufacture of the equipment, and installations in the desert would be fairly inobtrusive anyhow. But let’s think about it. The world’s energy demand increases by about 3% a year or so (again, thanks Google). Doesn’t sound like so much of an increase? Well, using the Rule of 72 (look it up), if we continue at this rate, our demand will double in 24 years. We will then need to cover another Australia/India with solar collectors to meet the demand. 24 years later, we will need FOUR times as much area as we started with. And consider that these devices lose efficiency over time. For example, I understand that photovoltaic cells lose about 20% of their capacity over 20-25 years, at which time they may be nearing the end of their useful life anyhow. Imagine large areas of the world covered with solar installations and associated transmission lines, and requiring replacement or major refurbishment once every generation or two!
It is also worth thinking about where the raw materials (minerals) for this equipment will come from, and where the energy will come from to extract and process the minerals.
A similar line of thought can be applied to wind energy.
Realistically, no one is going to replace all the world’s current power sources with renewable sources. Though there are a large number of assumptions in the above scenario, I still think it is useful to think through these sorts of claims. This illustrates that there is no silver bullet solution to our energy needs. If we expect to keep living at the same level of consumption, and our population continues to grow, we are going to make a big mess of this place, although (and even because) we use so called “clean” renewable energy sources. There are better ways.