In this series of sessions, we're going to look at several energy sources, two very popular energy sources, wind and sun, and nuclear. The renewables I'm going to look at, do not by any stretch of the imagination, exhaust the range of possibilities that we have. But the idea is not to give a detailed analysis of every single possible renewable source. But to furnish you, to provide you with the tools, to do the calculations yourself, understand what you must look out for. And always keep in mind, the scalability problem, when our real concern is, can we make a difference? Can we move the needle? So we begin with wind energy and we're going to answer a number of questions. How efficient is wind energy? Is it scalable, how big should the physical deployment of wind turbines be, in order to make a difference? And how big should the economic commitment required to make a difference, if we want to produce a lot of energy from wind? And it will be essential as we see, to distinguish between on-shore and off-shore wind turbines. And it is really, really important in all this type of analysis, both the wind and for solar and for nuclear and for everything else. To get real numbers, not just to be mesmerized by the use mega terra gigawatt, etc. So, in line to what I explained in our earlier sessions, I'm trying to get everything down to a manageable human size scale, so we can get a feel for the size of a problem. And therefore we have to use units, and let's refresh our memory a tiny bit. We're going to measure energy in KWatt hour. This is a very strange measure, as I said, I'm not going to swim against the tide. I would not have chosen this measure in the first place, but it is established, so we have to live with it, why is it strange? Because KWatt, is not a measure of energy is a measure of power. Power is energy per unit time. So when I say KWatt hour, I do not mean KWatts per hour per unit hours, but it is KWatt times hour. To get from power to energy I have to multiply power by time. That could be hour, day or whatever. In the following, I will express all the calculations for the UK. But there is nothing special about the UK, simply, but due to the weather time, UK base. So for me it's easier to get data in this national context, but it is an instructive exercise to repeat the same calculations, for any country, in which you might be leaving. And I've put up again here, one of the slides we looked at already, simply to remind ourselves of our yardstick, how big is 1 kWatt hour? Remember, 1 kWatt hour is one unit on electricity bills, and cost approximately 10 p. And 1 kWatt hour per day, is a nice human sized unit, because if you think of one, 40W light bulb, and you leave it on all day, it uses one kWatt hour per day. Okay, so this is the unit that we're going to use. So how much on-shore wind can be plausibly be generated? And I want to go ultimately, to power per person, because this is the way we're going to express our human sized per person units. And therefore I need wind power per unit area, and area per person. Area per person is very easy. I take the area of the country divided by the number of people in the country. For the, in order to get to power per person, I have to do, wind power per unit area times area per person. So, the bit we're missing, is wind power per area. Let's get started, let's assume in the UK, typical wind speed is approximately 22 kilometers per hour. So a tiny bit of reasoning, physics 101, etc. It calculate, calculation suggests that, the power ownership per unit time per unit area from a wind farm, is about 2W per meter square. So, which area now am I going to consider, or let's start big. Let's consider the case when I'm going to cover the whole of the UK. This will give us 250 people per square kilometer, plug it into the formula, power per person is wind power per unit area times area per person. And you get 8000W per person. This is power, I want energy. So I'm going to convert to our standard favorite human size units, and I get 200 kWh per day per person. That sounds impressive, but this was obtained by covering all of the UK, every single square centimeters with wind farms, it is not very realistic. Let's be still very aggressive, but a bit more realistic. And let's say that we are going to cover 10%, of the surface of the UK, with wind farms. Remember that there is a competition for land, for agricultural uses, for forestation, reforestation etc, as negative emission technologies. All these things have to be taken into account, but let's just settle for a 10% coverage. Clearly, we divide by 10, the number we obtained before, and 20 kWatt hours per day per person becomes, is the, sorry, the 200 becomes 20 kWatt hours per day per person. And okay, how big is that? Well, this figure here shows, the consumption in kilowatt hours per day per person, for cars, this is private use and from the wind. So, this shows that if we cover 10% of the whole land of the UK. With wind turbines, we obtain half as much energy as is used, just for private consumption in the UK. How realistic is my 10% coverage? Well, on the reference have looked at, which is a few years old but not enormously is five or six years old. It's stated is, this is equivalent to 50 times the wind turbines in Denmark, 7 times the wind turbine in Germany, and twice the entire wind bind fleet in the world. This doesn't close the argument, it doesn't mean, therefore it's impossible. It simply says that for wind turbines to make a different, their deployment must be huge. This was on-shore wind farming. And as we have seen, on-shore wind farming, can only give very partial solution to our energy requirement. What about off-shore, and here as I said, we have to distinguish carefully between shallow and deep offshore wind farming. But before we get started, let me try to tackle one objection which is often raised against wind turbines. And the objection is that, they are very damaging for migrating birds. Yes, they are damaging from migrating birds. But taking data here from the physicists MacKay at Cambridge University, there is a number of birds missing in action. I did put here, because of wind turbines, cars and mark of a cat, is not one individual cat, but it's all the cats in the UK. And the estimated number here, say some 55 million. I am not too happy with the precise 55 million. I would have preferred 50 million, does it make sense, 60 million people. Let's assume one person per cat, that is too much. On the other hand, one cat certainly kills more than one bird per day. So I can live with 50 million. 50 million birds missing in action because of cats. To be compared with 30,000, because of wind turbines. Admittedly, we will have to increase watt wind turbines a lot, but still we are many orders of magnitude away. One of my students when I showed this light says, yes, but it is not the same type of birds. True, but at this point, we are also making a value judgment, that the life of some birds is more worthy than the life of other birds, I won't go into this. But the purpose of showing, these little calculation, is always try to quantify, and try to put in context, all the scare numbers, that come from either direction, related to this type of arguments. So, let's begin to look at off-shore wind. Let's see winds are stronger than inland, and let's assume that they are about 50% stronger. In which case, the, we can estimate 3W per meter squared. And now we need an estimate of the area oversee that we could plausibly covered, with wind turbines. And this is where distinguishing between deep and shallow off-shore becomes important. Typically with classify as shallow offshore, it is depth less than 25 or 30 m. And this is technically feasible, without huge subsidies. Deep offshore at the moment, is not economically feasible, in the UK. There is, to my knowledge only one wind farm, which is, there is a bit ironic, is an experimental prototype. The sense, all of its of its electricity, to an oil rig. So the irony that is sending to an oil rig. But let's leave this to one side. So, we're going to look at shallow wind farming first, Britain is obviously blessed by a very, very generous coastline, and within British territorial waters. The shallow area is about 40,000 square kilometers, most of it off the coast of England and Wales. So the average power, available from shallow offshore wind, would be 120GW or 48 kWatt hours per day per person. Remember 55, if I remember correctly, was the amount for private consumption. However, I have now covered absolutely all the 25 to 30 m depth water, which is not realistic. We have to leave fishing, and shipping corridors. So an aggressive estimates of shallow water available, let's say, is one third of this. Therefore the maximum plausible power, from shallow offshore wind, would be all the order of 16kWh hour per day per person. It is still very big, there is still one third of Wales. So, if we take the total coastline of Britain, length 3000 kilometers. And put a strip of turbines, 4 kilometers wide all around, that's trip would have an area of 13,000 square kilometers. This is the area that we must fill with turbines, to deliver 16 kilowatt hours per day per person. I have said that, offshore wind at the moment is not economically, are the feasible or attractive. Let's take a, cost is no object approach. The areas with depths between 25-30 and 50 meters, is about 80,000 square kilometers, the size of Scotland. So, assuming a power per unit area, a still of 3W per square meters. Deep offshore wind farms could deliver another 96 kWh per day per person. If turbines completely fill this area, again, we have to leave some room, for shipping corridors and fishing corridors. So let's take one third, and we are down to 32kWh per day per person. Note that some turbines would be as far out, as 50 km from the shore. What about building the wind turbines, combining onshore and offshore turbines, considering no cost objections. And being very, very aggressive, we have arrived at 48 kWh per day per person. Which is a bit more than the energy consumption, for private cars in the UK. To create these turbines, we need a lot of energy, which is all taken into account in the energy balance. So I'm not saying for a second, as you often hear in the propaganda, that it takes so much energy building a wind turbine, that you don't actually get the energy payback. That is not true, but it still requires a lot of concrete, and a lot of steel. It requires one ton of steel per person. Annual world steel production is about 1200 million tones, which means 0.2 tons per person. The requirement in the UK would be one ton per person, let's put it in scale. During the second world war, American shipyards builds more than 2500 liberty ships, each one containing 7000 tons of steels, to do that. It was an effort that was 0.1 tons per American. So per person, that effort was one tenth the required effort, to build the wind turbines per person. Again, this doesn't mean, therefore we can't do it. What it does mean however, is that it is literally because of a comparison I've made, a war effort. And as we shall see, this is a recurring theme, whenever you hear, if we just do a tiny little bit, if we switch off the lights, when we go out of the room etc, everything will take care of itself. That is not an honest appraisal of the type of commitment we have to make, in order to tackled seriously climate change. So I'm bringing up all these numbers, not to say, therefore it's unfeasible, but simply to say, it is feasible on a war effort scale. [MUSIC]
