In the previous post, I looked at the issues involved with replacing all motor vehicles with electric vehicles, and noted that is impossible with what we know now because the necessary materials are just not there. Of course there may be new battery technology developed, but there is another issue: from whence the energy? From international energy statistics, petroleum liquids have the equivalent energy of 53 trillion kWh. Since the electric vehicle is more efficient we can divide that number by about three, so we need almost 18 trillion kWh. (The issue is more complicated by whether we are trying to replace petroleum or solve the transport issue, since some petroleum products are used for heating, but for simplicity I am going to stick with that figure.) If we were going to do that by solar energy, the sunlight gives according to Wikipedia, on average about 3.5 – 7 kWh/m2per day. That needs about five trillion square meters devoted to solar energy to replace petroleum products. The Earth’s area is 510 trillion square meters, so we need about 1% of the surface area devoted solely to this, if the cells are 100% efficient. The highest efficiencies so far (Data from NREL) come from four junctions, gallium arsenide, and a concentrator where 46.6% has been reached. For single junction cells using gallium arsenide, we get 35% efficiency, while silicon cells have reached 27.6%. If silicon, we need 4% of the world’s area.
It is, of course, a bit worse than this because 70% of the world’s surface is ocean, and we can eliminate the polar regions, and we can eliminate the farmland, and we should eliminate the wild-life habitats, and we can probably assume that places like the Sahara or the Himalayas are not available and anyway would be too dusty, too windy, too snowy. Solar energy drops efficiency quite dramatically if the collectors get covered in dust or snow. So, before we get all enthusiastic about solar, note that while it can contribute, equally there are problems. One issue that is seldom mentioned is how we find the materials to make such a huge number of panels. In this context, the world supply of gallium is 180 tonne/a, so basically we should be back to silicon, which is one of the most plentiful elements. (In one of my novels I made a lot of someone finding a source of gallium otherwise overlooked. I feel good about that!). We don’t know how critical element supply would be because currently there is a lot of development work going on on solar conversion and we cannot tell what we will find. The final problem is that latitude also plays a part; in southern England we would be struggling to get the bottom of the range listed above on a sunny day, and of course there are many cloudy days. Accordingly, assuming we do not put the collectors on floats, the required area is starting to get up to 10% of the land area, including highly unsuitable land. We just cannot do it.
That does not mean solar in of no use. One place to put solar panels is on the roof of your house. Superficially, if every motorist did this, the problem is solved, apart from the long-distance driving, at least in the low latitude areas. The difficulty here is that the sun shines in the day, when the commuter uses his car. The energy could be stored, but we have just doubled the battery requirements, and they were already out of hand. You could sell to the power to the grid, and buy power back at night, and there is merit in this as it helps with daylight loads, except that the power companies have to make money, and of course, the greatest normal power requirements are in winter at the beginning and end of the day, when solar is not contributing. So yes, solar power can help, but it is not a single fix. Also, peak power loads are a problem. If the company needs capacity for that, where does it come from? Right now, burning gas or coal. If your electric vehicle is purchased to save the environment from greenhouse gas emission, that is pointless if extra power has to be generated from coal or oil.
My personal view on this is that while renewables are going to be helpful, if we want to stop emitting carbon dioxide when making energy, we have to go partially either nuclear or thermonuclear. My personal preference is for fusion reactors, but we do not know how to make them yet. The main problem with fission reactors is the disposal of waste, and the potential for making materials for bombs. We can get around that if we restrict ourselves to thorium reactors, because the products, while still radioactive, decay much more quickly, and finally you cannot make a thorium bomb. Another benefit of thorium reactors is they cannot get the runaway problems as seen at Chernobyl and Fukushima; they really are very much safer. The problem now is we have not developed thorium fission reactors because everyone uses uranium to make plutonium for bombs.
Even if we manage to get sufficient electricity, the next problem is transmission of this huge increase in electricity. In most countries, the major transmission lines will not take it, and would have to be replaced or supplemented. Not impossible, butat the cost of a lot of carbon dioxide being emitted in making the metals, and transferring them, because massive electric vehicles cannot precede the ability to shift electricity. Again, this is not a problem per se, but it is if we do not get organised quickly. The next problem is to get it to houses. “Slow charging” overnight is probably adequate, even for a tesla. If you can charge it fully in an hour at just over 40 amps, you should need only 3 amps overnight. Not difficult. However, the retail sale of electricity for vehicles travelling is not so easy. It is hard to put figures on this because I don’t know what the demand will be, but charging a vehicle for over an hour means no more than about ten vehicles per day per outlet. It is hard to make money out of that, so you need a lot of outlets. If you have a hundred outlets, you service a thousand cars, say, per day. Still not a lot of profit there and you need a parking lot and some excellent organization. You are also drawing 4,000 amps, so you need a fairly good power supply. Not an enticing proposition for investment.
The point I am trying to make here is that the problem is very large. We have built a monstrous infrastructure around oil, and in the normal circumstances, when we have to change, that industry would go slowly and another would slowly take its place. We don’t have that luxury if we want to save our coastal cities. Yes, everyone can “do their bit”, and that buys time if we all do it, but we also need some bigger help, in organization, research, development and money. It is time for the politicians to stop thinking about the next election, insulting the opposition, and start thinking about their country.