Rising Carbon Dioxide Levels
Although many natural processes release enormous amounts of carbon dioxide, this is balanced by the level of carbon dioxide taken in. However, when artificial carbon dioxide is released, overall the level of atmospheric CO2 increases which causes noticeable effects.
Figure 1 shows global carbon dioxide levels for the last millennia, measured from air trapped in ice cores. 1 Marked on the graph is 1769, the year that James Watt patented his steam engine. From this, we can see that the industrial revolution, which followed this invention and was powered by burning fossil fuels, caused this enormous rise.
Recent data from EDGAR (the Emissions Database for Global Atmospheric Research) shows that currently, 90% of global greenhouse gas emissions are caused by our energy needs 25 (this includes power stations, transport, industrial processes, fossil fuel processing and energy use in buildings). But what will be the consequences for us? This question is hotly disputed in scientific circles.
The Greenhouse Effect?
Climate science is a complex and mostly speculative field. The majority of people now accept that there is a greenhouse effect, but exactly what it is and to what extent it affects us is still uncertain. Many scientists state that greenhouse gases such as carbon dioxide absorb infrared radiation that would otherwise leave the atmosphere and emit it in all directions. Essentially, this changes the direction of infrared randomly so that more stays in the atmosphere, retaining the heat. More carbon dioxide means more scattering, reducing the probability that infrared radiation will leave the atmosphere, thereby heating the planet.1
Many climate sceptics object by saying that the second law of thermodynamics states that energy spontaneously transfers from a warmer object to a colder object. Therefore upper, colder areas of the atmosphere cannot reflect infrared radiation back towards the lower part of the atmosphere because heat moving from cold to hot areas violates this law.2 However, this law applies to whole systems, not to parts of a system. The net movement of heat is to the colder areas, but some heat can move from the cold upper atmosphere to the lower atmosphere.
Two future climate models by Baer and Mastrandrea paint a grim picture for us:
Fig. 2: Figure 2
Global emissions for two scenarios considered by Baer and Mastrandrea, expressed in tons of CO2 per year per person, using a world population of six billion. Both scenarios are believed to offer a modest chance of avoiding a 2°C temperature rise above the pre-industrial level.
Figure 2 3 shows the reductions that we have to make in our carbon dioxide emissions to avoid a certain probability of a 2˚C increase in global temperatures. This is predicted as the point after which extremely bad things start to happen, with rising sea levels and extreme weather among the consequences. It is already too late to meet the first line, and we are also very close to missing the second. The main problem with the climate change debate is that it is fuelled by external intentions, as opposed to statistical evidence.
What Are The Effects For Us?
Whether the greenhouse effect is real or not, higher levels of carbon dioxide are harmful to our wildlife. The atmosphere balances itself out with ocean surface waters, and our carbon dioxide emissions add approximately two gigatons of carbon dioxide per year into the ocean. Carbon dioxide is continually absorbed by the oceans forming carbonic acid, which gradually decreases the pH of our ocean waters. Since measurements began, ocean pH has decreased by about 30%. If we continue to emit carbon dioxide at a continual rate, ocean pH will have decreased by about 150% by 2100. This will cause mass extinction of marine wildlife, especially those that use calcium carbonate as a skeleton or shell, and this massive disruption of the ecosystem will inevitably affect most life on earth.4
Fig. 3: Figure 3
The process through which atmospheric carbon dioxide acidifies ocean waters.4
Carbon Neutral Energy
One of the UK’s main targets as far as Global Warming is concerned, is to reduce its carbon footprint. There are a number of ways that this can happen. Firstly, we must replace our power stations with new, carbon-neutral energy sources. However, our electricity consumption contributes to only part of our total carbon output. It is also necessary to start using electric cars and replacing gas-fired heating with electric heating. Essentially, we need to source clean electricity and make sure everyone is using it. To determine a plan that works, we need to look at the numbers.
The sustainable development commission said that “The UK has the best wind resources in Europe”5, so wind is definitely the first power source we should look at in order to solve the problem of rising carbon dioxide levels. We can make an estimate of onshore wind possibilities by multiplying the wind power per unit area by the area available per person. Current wind turbines generate about 2 W/m2 6 and the current population density is over 250 people per km224, equivalent to about 4000m2 per person. Assuming turbines were packed across the whole country then they would produce 8000W per person or 200 kWh/d per person. However, realistically, perhaps 10% of the country would be covered by wind farms. This gives a figure of 20 KWh/d per person, about half the energy used by driving a standard car 50 km a day.1 While it is clear that onshore wind could make a big difference if it was properly managed, it is not nearly enough to cope with our current huge consumption.
Offshore wind comes in two forms, shallow (water depth below 25m) and deep (between 25 and 50m). Currently, deep is not considered to be economically viable, 17 but shallow is already in use. At sea, wind speeds are higher so there is a slightly higher power output of about 3 W/m2. The total area in British water of the correct depth is about 40,000 km2, twice the size of Wales.8 Using our previous calculation we get a figure of 48 KWh/d per person, assuming the entire area surrounding Britain was covered by turbines. A more reasonable figure is probably a third, so 16 KWh/d per person. Assuming deep wind did become feasible and an area of about 80,000 km became available and we filled a third of that with turbines, that would still only be 32 KWh/d per person.
A problem with offshore wind is the corrosive sea air. A farm in Denmark had to be dismantled after just 18 months of use as a result of this.9 Another problem is its enormous expense. To produce all these turbines would need 60 million tons of concrete and steel.6 The problem with wind is the sheer quantity required to make any significant difference.
Solar energy is not in abundance in the UK, but this can still make a large contribution to our energy budget. The simplest solar technology is solar thermal, using sunlight to heat water. Average solar intensity is about 100 W/m2 in the UK 10 and the best solar panels convert this to heat with 50% efficiency.11 If everybody covered their roofs with these panels, the area used would be about 10m2 per person so solar heating could deliver 12 KWh/d per person. The big problem with this energy is that it is heat, which is very difficult to store, so if it is not used when available it will be wasted. It will also be concentrated in the wrong areas, as roof area per person is much less in urban areas, where more people need the energy.
Solar photovoltaic panels are much less efficient, but they produce electricity, which is much more useful. The most expensive panels have 20% efficiency12 which is an additional 5 KWh/d per person. Of course, we can’t have both of these, and it is a difficult decision between energy loss from thermal and the low efficiency of photovoltaics. HelioDynamics have addressed this with their solar combined panel. This is a photovoltaic unit which has water pumps running behind it and high focus mirrors which in total would deliver 69 KWh on an average day. This is half of a European’s average daily energy consumption. However, they are very expensive, so not economically feasible on a large scale.13
Photovoltaic farming is currently only a fantasy because the mass-production of these panels is very expensive.14 However, if a breakthrough caused this price to drop and we covered even 5% of the country with 10% efficient panels then the energy produced would be 50 KWh/d per person. This is an enormous number of panels, 100 times as many as there are in the world today. If we were going to make this many panels, it would be better to install them in a sunnier country and send the electricity back.
Fig. 4: Figure 4
A photovoltaic farm in California.26
Solar biomass is a promising idea because it involves something we are already very good at – farming. This is a form of solar power which uses plants’ natural photosynthetic ability to harvest energy from sunlight. Usually, plants such as sugar cane are used as they can then be harvested and converted to fuel via fermentation or other processes. However, it has a number of limitations. The maximum amount of harvestable energy in Britain is 100 W/m2 and the most efficient, most well-fertilised plants in Britain convert this sunlight into energy with about 0.5% efficiency,15 so 0.5 W/m2 is achievable. Although they are not even close to the efficiency of photovoltaic panels, they are much cheaper and so we can cover 75% of the country with them, the amount of land currently used for agriculture in the country. This would theoretically yield 36 KWh/d per person. But this is before we have considered the energy costs of farming and converting the crops into a fuel we can burn. For example, most wood boilers lose 20% of the heat up the chimney. A more realistic figure is probably two-thirds of the efficiency, producing 24 KWh/d per person.
Tide is a relative unknown in the energy field and has never been capitalised on on a large scale. However, as an island nation, it is definitely something we should consider. There are three options for tide: Tidal farms, barrages, and lagoons. Tidal farms would be similar to wind turbines but underwater – something that only currently exists in Norway. To estimate the power from these we will have to make a number of assumptions. Firstly, that they will have a similar arrangement and efficiency to wind turbines. Using the same equations as for wind, we find that if tide was placed in all of the fastest tidal areas of the coast with speeds of about 2 or 3 knots, tide could be a valuable investment for the country, producing 9 KWh/d per person.16
The current method of using tidal power is the tidal barrage. This involves building a dam across a tidal area. There are sluice gates which allow the tide to come in and these gates then close while the tide goes out. This traps the water in the bay, creating potential energy. This water is then released back to the sea via a turbine. Although this is the most widely used form of tide, it is probably the least efficient. Because it only harnesses the energy of the tide coming in, the total estimate for these barrages at the places where tidal range is greatest is only 0.8 KWh/d per person, which is not worth including in our estimates.1
The improvement to this is the tidal lagoon. It is the same concept but it is built into the sea rather than across a river. This means that both directions of flow are harnessed and over a much greater area. Also, two lagoons can be built next to each other, so the power produced by one can be used to pump water out of the other to produce an even lower level than usual. This energy is then repaid by the extra range at the next tide. Due to this, the estimated figure for lagoons is 2 KWh/d per person. Tide is very promising for the UK for a number of reasons. It does not require expensive equipment like all the other forms of energy so far. It is very reliable, consistent and easy to predict. Because a tidal flow has a greater power density than wind, it is much more efficient. Although now tide can only contribute a small amount, it has a lot of potential. 17
Hydroelectricity should be a very promising energy source for this country because we have large mountainous regions and it rains a lot. However we currently only get 0.2 KWh/d per person from hydroelectric dams. This is because although our rain may seem relentless to us, its potential power is actually very low. Kinlochewe in the Scottish Highlands gets 2278 mm of rain per year and large areas are above 300m. By multiplying these figures and others, we can get a potential energy of roughly 0.24 W/m2. 1 Should all catchment areas above 1300 metres be utilised then the potential power is 7 KWh/d per person, assuming water stopped evaporating and every drop was perfectly exploited. Unfortunately, people also live in these areas which we would need to be flooded, so a more realistic figure is using 20% of the land – 1.4 KWh/d per person.
Fig. 5: Figure 5
Loch Sloy hydroelectric power station.27
Geothermal is a very exciting technology because it harnesses the enormous power of Earth’s core. However, it requires us to drill very deep holes and pump water down them. Because there is a limit to the depth that we can drill to, there is also a limit to how much energy we can take out. As we pump water down, it cools down the rocks to which we have drilled. For this to be sustainable, we would have to pump the water down at the same rate as heat from the core reaches the rocks, which is slow. The optimal depth for this currently is 15 km and if 10% of the country was filled with these holes, the power generated would be a tiny 0.2 KWh/d per person. It is obvious that, sadly, there is little potential for geothermal power in this country.19
There is one final power source that I have neglected to mention so far because unlike the others, it is not sustainable. There are currently two possibilities for nuclear power: Fission and fusion. Fission is the source that we know how to use and is the splitting of heavy nuclei to become smaller ones, releasing energy. An advantage of fission is that its energy density is very high. 2 grams of uranium in an inefficient fission reactor provides the same amount of energy as 16kg of coal. The method currently favoured by the United States and others is the once-through reactor. It burns only the fissile uranium-235, about 0.7% of any mined uranium, and the remaining uranium-238 (U-238) is left as waste. This is because to be fissile, the uranium must be able to sustain a chain reaction with neutrons. This cannot take place in U-238. These reactors are extremely inefficient (although still more so than a fossil fuel power plant) and without great improvement cannot contribute very much at all.20
There is another type of reactor, the fast neutron reactor, specifically fast breeders. These reactors are designed to enrich U-238 to fissile plutonium-239, which can then be used in the reactor. These reactors are far more efficient, but more dangerous. This is because they also utilise minor actinides which are produced as waste, which can be very dangerous. When curium is irradiated by neutrons it forms very heavy californium and fermium which undergo spontaneous fission. This makes planning these reactors very difficult and very expensive. Sadly, they have dropped off many countries’s energy plans.21
However, Russia, Japan and France have persisted. France had an extremely successful reactor called the Superphénix. This operated successfully from 1985-1998, but was closed because many people feared that it was dangerous. Russia has built Beloyarsk with a slightly lower power output but a much stronger emphasis on safety. It became operational in April 2014 and should produce 789 MW.
Should this reactor be deployed across Britain then we can estimate a power of 33 kWh/d per person. However, current attitudes are that this is a dangerous, unreliable technology. This will have to change if nuclear is to fill the gap left by fossil fuels.22
Fig. 6: Figure 6
The new control room at Beloyarsk.28
The other possibility is fusion. This is combining the nuclei of lighter elements to form heavier ones, releasing energy. This is what powers stars and so is an enormous potential power source. However, it is still in its very early stages. There are a number of problems that must be overcome before fusion can supply commercial electricity. Fusion requires enormous pressure and extremely high temperatures to start. The National Ignition Facility in America was set up to try to achieve a “burn and gain”. This is a fusion reaction where the energy used to start the reaction is less than the energy generated. Although the energy required to start the reaction is huge, the energy produced by the fusion is even greater. The reaction uses the principle that when there is an explosion, there is an equal and opposite implosion. The fusion fuel (a mixture of deuterium and tritium) is placed inside a tiny spherical capsule. This capsule is then heated by a laser that for 20 billionths of a second produces power equivalent to 500 trillion watts. The capsule explodes but also implodes, providing enormous pressure and heat to the fuel. This starts the fusion reaction. It is apparent that the energy here is enormous, but this power is dangerous and very difficult to control or to harness. Should the technology ever be mastered, it would solve our energy crisis indefinitely, but until then it just isn’t possible.23
Fig. 7: Figure 7
The two-millimetre fuel capsule. 23
So, can Britain maintain its current life without fossil fuels? When we add up the numbers we find Britain’s energy potential from carbon neutral sources could be 205kWh/d per person. The total British energy consumption is 195kWh/d per person. Some of the energy projects listed above such as the deep offshore wind or the photovoltaic farming would require some major sacrifices. For a while, electricity could become much more expensive and we are going to have to also consider ways to use less of it, striking a balance between investing in carbon-neutral sources and cutting our consumption.
So, what is the current UK government doing to tackle this problem? In January of this year, the government separated from the EU’s green energy plans because it felt that the plans were too extreme and they could not cut emissions by the amount required without driving up energy prices and creating a cost of living crisis. Decision making on these questions is, unfortunately, often driven not by scientific reasoning, but by political expediency. Uncertainty on the underlying science may still remain and it is not possible to make guaranteed predictions about the future. We have to rely on the numbers, and have a plan that adds up.