What would be the implications of converting completely to EV’s? In the UK there are 31.5 million cars. The average mileage in the UK is 7900 miles/year (2), a figure which covers both private and business use. To give an order of magnitude estimate assume the entire fleet is replaced with cars having an average energy performance equal to the energy performance of the current Tesla S 85. The average annual electricity required for each car is then 7900 / 2.24 = 3527 kWhr, and for the entire fleet is 111 TWhr /yr , or 304 GWhr/day. If the recharging can be evenly spread over the full 24 hrs (unlikely), this equates to a power of 12.7 GW.
This power has to be supplied though the national grid. The UK transmission loss is around 7.9%, so the required generation rate is 120.5 TWhr/yr, or an average of 13.8 GW.
The power presently supplied by the UK grid varies through the day and the time of year, but is typically in the range 25 – 45 GW, and averages perhaps 35GW. Total generation capacity is understood to be around 85 GW, but not all of that is available at any one time. Any generating plant may be offline due to maintenance, and of course wind and solar generation vary due to weather conditions and the time of day. The maximum UK load occurs during winter, when electrical production from solar PV is inherently low. In 2014/2105 the maximum load was 53.9 GW (10th January 2015).
UK wind turbine capacity is presently 13.5 GW (3) but the overall capacity factor (overall figure for offshore and onshore) is only around 28% (15), giving an annual average generation of 3.8 GW. Planned / approved capacity is set to rise to 35.1 GW. In winter turbine de-icing and heating can consume a significant proportion of the turbine’s rated capacity; in general there is a loss of 10-20% between the gross power extracted by a wind turbine and the nett power available to the grid.
Wind power is variable. In the UK in 2015, the metered wind turbine power to the grid (which is around 2/3 of the total wind power in the UK) averaged 2.66 MW, the peak was 6.7 MW, but for 19% of the year the generation was less than 1MW. There was at least one 24 hour period where the generation was below 250 kW.
UK solar PV capacity is presently around 7.8 GW (16) and is expected to reach 10 GW by the end of 2016. The problem with solar PV is that power production is zero at night time, and poor weather conditions can reduce day time production to a few % of the installed capacity. Solar PV will generally peak around midday (for obvious reasons). In the UK, the capacity factor for PV is usually given as being around 10 - 11%.
The power generation from solar PV in 2015 was 5.9 TWhr, an average of 0.7 GW (15). The data implies a capacity factor for 2015 of 8.7% .
Apart from variability, the other problem with wind and solar is they cannot be reliably predicted except for perhaps a few days in advance – other capacity is required to make up the any shortfalls, be it fossil fuel or nuclear. Wind has a particular problem as the power generation is very sensitive to the wind speed. Small errors in wind speed prediction give significant errors in predicted power output.
Switching from ICE cars to EV’s would take additional power generation averaging 40% of the current total power generation (i.e. pushing average generation up from 35 to 49 GW).
To provide this extra demand by wind needs something like 50 GW of additional installed wind turbine capacity to match the average demand. Since it is inevitable that recharging demand would show some variation over the day, this could easily require (say) 60-70 GW of installed wind capacity. A significant level of reliable (non-wind, non-solar) capacity will have to be provided as a back-up.
For wind turbines (or solar) it has to be recognized that providing conurbations with the clean electricity they may benefit from requires building vast arrays of turbines (or solar panels) somewhere else. Providing 60 GW of installed wind capacity would require 24,000 2.5 MW turbines, each with a rotor diameter of around 100 m and around 150m high. Assuming a minimum separation distance of 7 rotor diameters (700m) this requires an area of around 12000 km2.
If these were onshore that is equivalent to around 5% of the entire land area of the UK (c. 240,000 km2). The optimal spacing for large turbines may be as high as 15 rotor diameters; at this spacing the area required would be equal to 23% of the area of the UK. For a minimum distance of 2 km from an array to any residential area, Fig 18.8 of ref. 21 shows a plot of the UK where this might leave places suitable for wind farms – basically Scotland other than the lowland belt, perhaps a third of Wales, and perhaps a quarter of England, including Dartmoor and areas of the North York Moors. The turbines have to be distributed across the country.
There are safety issues around wind turbines. According to ref. 19, in the UK there were around 160 wind turbine related accidents each year between 2010 and 2015; this may represent a marked under reporting of incidents. Blade failure and fires are the most common accidents. The Scottish government is considering increasing the minimum separation distance between wind farms and local communities from 2 to 2.5 km .
The useful life of wind turbines may also be substantially less than promised by the turbine industry. Ref 20 (2012) (as well as other sources) found that the useful life of a turbine may be as low as 10-15 years, not the 20-25 years generally assumed, and lower still for offshore turbines. Against that, Siemens have offshore turbines that have achieved lives of more than 20 years and are still operating.
The capital cost of onshore wind power is around £1300 / kW of capacity,so for 60 GW the total is £78 billion. Onshore generation has issues around blade noise, visual impact, and flicker during the early or late daylight hours. The likely additional capacity required for the national grid to distribute the additional wind generated power will add to the total cost.
If built at sea the turbine numbers would reduce, since offshore capacity factors are higher than for onshore (generally higher wind speeds), but the unit cost is around double (£3100 / kW) so even if the installed capacity is reduced to say 50 GW, the cost is now £155 billion. Allowing for postulated future reductions in costs, the cost in 2023 is still expected to be around £2400 /kW, or £120 billion (8).
The UK government has recently guaranteed minimum prices for offshore wind power at £140 to £150 / MWhr, which compares to the present wholesale price of around £45 / MWhr. UK electricity bills are likely to rise steeply as offshore power contributes a larger percentage of the UK electricity mix. This makes the £92.5 / MWhr guarantee to secure the new Hinkley nuclear power station look like a good deal.
The required 13.8 GW of power generation could be built as nuclear for perhaps £82 billion (nuclear plants produce power continuously and have a high availability factor). Total present nuclear capacity is 9.3 GW, of which most will be shutdown by the mid 2020’s; present nuclear generation is typically around 8 GW.
Future demand and supply patterns require complex modelling, but even a simple analysis shows that electrification of transport requires a huge investment in additional generation capacity and in reliable backup generation, of which most cannot be fuelled by renewables. It probably also requires a sea change in people’s behaviour and expectations. It may not always be possible to charge up your car.
Road transport of people accounts for around 55% of the total energy required for road transport. Electrifying the entire transport system would more or less double the amount of electricity required.
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