In a utopian world, all our energy needs might be met by renewables. It is the green dream of a world in which wind/wave/solar/ hydroelectric/geothermal are the primary energy sources, and are used to turn turbines to make plentiful electricity for all, while leaving "The Environment" untainted. Even if we could find utopia in the U.K.'s pleasant land, currently the green dream would only supply 18% of the energy that the nation uses overall. Placed in context, the most favourable rallying cry, that 40% of the U.K.'s energy might be provided from renewables by 2050, appears a little limp, since it may be seen that even this most favourable scenario would only provide 40% of 18% = 7.2% of our total energy requirements, once the significance is appreciated that by the word "energy" it is "electricity" that is actually meant, but it sounds far more progressive to call it energy.
The current proportion of electricity generated from renewables is miniscule, at around 1%, i.e. perhaps 0.2% of total energy. The figure of 9% often quoted as being the proportion of electricity produced as "primary electricity" is highly misleading, since it includes electricity generated using nuclear power - rather, "uranium" should be listed separately as a primary fuel, reserving the term "primary electricity" for that produced from hydroelectric/wind/wave/solar/geothermal sources, i.e. those which are truly primary, and are renewable. Nuclear, as I have commented in previous articles in this series, is unsustainable (because it uses up uranium, of which there is only a limited supply), potentially dangerous and of limited benefit at best, neither securing security of supply nor significantly eliminating the U.K.'s own burden upon world CO2 greenhouse gas emissions.
If we "do the math" as they say across the pond, i.e. work a book keeping exercise, the figures find that 22% of total electricity is provided from nuclear sources, ignoring the Sun whose contribution to artificial energy production is negligible, standing trivially apart from the miracle of photosynthesis. As I have noted, even generating 40% of electricity from renewables by 2050 would only represent 7.2% of the energy we use in total, while oil and gas will still furnish the lion's share, together providing 78% of the total. As I stated at the outset, we are considering a perfect world where electricity is in limitless supply, and is provided from renewable sources. In such a world, why wouldn't we simply provide practically all our energy requirements by electrical means? Wind energy is more complex than at first appears. It is not simply a case of inaugurating 1 GW of wind capacity to replace 1 GW of fossil fuel or nuclear (ground based) power. The reason for this boils down to the fact that the amount of energy that may be extracted depends on the dimensions of the turbine blade and on the speed of the wind. Thus a blade that is too small might extract very little energy until the wind speed had reached, say 40 mph, and since the wind speed varies and is often significantly less than this, the turbine would not accumulate sufficient time at high power output to achieve a reasonable annual energy output.
A larger blade might begin to harvest wind energy at only a few mph, drawing a maximum power at, say 15 mph, but would need to be geared down, perhaps by the time the wind speed reached 25 mph to limit mechanical stress upon the turbine.
Experience in both Germany and Denmark - a country which produces 20% of its electricity from wind power (i.e. about the same as the U.K. does from nuclear) - is that 20% or less of full capacity is expected over a period of a year. This "capacity factor" as it is known, is simply the wind turbine's actual energy output over the year divided by the energy that would be obtained if it were run at full capacity over the same period (i.e. an upper limit of 0.2, which we now assume). A crude calculation indicates that if we were to try and replace around 62 GW of current energy demand by wind power, this would require 62/0.2 = 310 GW of full wind turbine capacity. But this large number still only refers to the 18% of total "energy" that comes from electricity. If we take the calculation to the limit of supplying all energy in the form of electricity, in order to eliminate the use of coal/oil/gas/nuclear generated energy, we would need about another 80% of the total which comes to 276 GW as derived from these greenhouse gas generating source (and building nuclear power plants, mining and milling their uranium fuel etc. also produces CO2, despite the rhetoric of the pro-nuclear lobby, the government and it's Chief Scientific Advisor), this steps up to a massive 310 + (276/0.2) = 1690 GW to be generated from wind energy.
The technology improves as turbines get bigger, but even using turbines rated at 0.5 MW full capacity, we would need to produce 3,380,000 of them, which would be a staggering endeavour. In addition, a vast network of hydrogen - an energy storage medium, which requires primary fuels to produce it, including electricity as in the present utopian scenario - storage devices, fuel cells for vehicles as we are going the whole hog of 100% reduction in carbon emissions here, would be necessary. Graham Sinden at the Oxford University Environmental Change Institute has estimated that a mix of 43% wind, 52% wave and 5 % tidal stream power could reliably produce the equivalent of 8 GW worth of coal, oil or gas power (out of about 344 GW worth of these total fuels burned), which is not a lot. If drastic reductions in emissions of greenhouse gases, in the range of 80 - 90% (still requiring 3 million or so wind turbines) of the current level is required by 2023, we really are in trouble, as there is no real means to replace the huge qauntities of fossil fuels that we currently use.
The only scenario which could succeed in making any significant impact is to focus on energy saving strategies, e.g. buildings designed perhaps along the lines of the "40% House" being researched by Dr Brenda Boardman's group in the Oxford University Environmental Change Institute, and further advances of it where heat from appliances, body heat etc. would fulfil most of its space heating requirements. The "Zed Bed" and "Passivhaus" concepts are also most interesting, and there are web pages available for them which are worth purusing for more detail. The Passivhaus is a continuously ventilated unit, which draws warm air into it via pipes that are heated geothermally by being buried in the soil, thus avoiding the veltilation problems that might arise from an "ultra"- insulated building and since the incoming air is to some extent warmed (to 5 degrees C, even in winter), along with efficient insulation, relatively modest additional heating is needed. However, the construction and engineering efforts required to substitute sufficient such buildings on time (i.e. before the climatic effect of CO2 is expected by some experts to be irreparable, 2030 perhaps) are truly daunting, and would meanwhile be producing CO2 until their final fabrications were complete. This point was reinforced by Professor James Wouduysen recently, in his statement: "It will take 1,000 years at current rates for our current housing stock to be replaced". He then suggested that houses could be constructed as part built kit homes, exported from China, which could be assembled in the U.K. and transported to their final site of location. This might require relocating some people to other parts of the country, but he argues that 280,000 computer designed, insulated units a year could be provided for the U.K. market by this means, which in many ways resembles car mass production.
However, the aspect of having more energy efficient buildings does not tackle the issues/problems of transportation, and its fuel requirements which remain enormous even allowing for improved efficiency methods - i.e. more miles per tank of fuel, using fuel cells etc. ultimately, and meanwhile using more efficient combustion engines, while the hydrogen powered utopia was being implemented. This leads to my final point, that we also need to reduce our dependence on transportation by living in "local" communities based on local economies, which supply smaller populations from local farms, and therefore cut down generally on more global transportation necessities. In our localised communities, we would also want fewer cars, and less foreign holidays too, once the general concept had been assimilated that we can't continue as we are. I'm afraid this is the best I can offer, which gives me no comfort either, but I can see no quick fix to our greenhouse gas emissions, as implementing all of this will take decades, if it happens at all. Meanwhile we will continue to pump out CO2 into the atmosphere.