Saturday, May 7, 2016



This comment is the third of three short pieces highlighting particular questions for the road transport sector.  The first dealt with the role of regulation in shaping energy efficiency, using US experience as an example. The second dealt with lessons to be learned from the London congestion charge in the context of the environmental benefit of lower congestion.

Electric vehicles provide what is prima facie the perfect solution both to removing fossil fuel use from the transport sector and providing a convenient outlet for low or zero carbon electricity generation which is intermittent or inflexible. The reason is they use batteries and this potentially allows the timing of recharging to be fitted to the needs of the power system. But they also pose some potential problems and new challenges for power distribution networks, an example being the Norwegian  “Friday night” problem, the subject of an interesting anecdote.

Electric vehicles (EVs) are widely seen as the innovation that allows decarbonisation of road transport. A prior condition is that the electricity itself is produced from sources other than conventional fossil fuel generation, ie from nuclear, renewables or thermal plant with carbon capture and storage (CCS). This is already broadly true for countries like France and Norway, but is also the clear ambition for the UK, anticipating a more front-end loaded reduction in carbon intensity for power generation than heat and transport, both of which will also depend on low carbon electricity. We can expect this pattern to be repeated in many countries approaching the commitment to the recent Paris (COP21) agreement.

But the big problem for power systems based on renewables and other intermittent sources is the non-storability of electricity and the need to balance supply and demand in real time. This poses problems both because of the intermittency of supply and the seasonal nature of some new loads such as electricity provided for the heat sector.  The answers are likely to include storage as well as more active maangment of consumer loads.  However electricity for transport has been widely seen as part of the solution rather than as part of the problem, simply because vehicle batteries have the potential to operate as a major source of storage.

Norwegian Experience

Norway is a world leader in EV take-up. Its conditions are particularly favourable because it has what is essentially an all hydro-generation power system. This implies that the electricity generation is non-fossil fuel and essentially carbon free; and it also makes for great flexibility in the way the power system can be operated.

A useful case study is Norway, which is the world leader in per capita take-up of electric vehicles (EVs).  A third of new car registrations are EVs, which now exceed 3% of the total fleet. The great majority of these are all-electric, of which there are now some 75,000.  EVs  have been strongly promoted by the Norwegian government, offering tax incentives and also allowing local authorities to prioritise EV owners for both road use and parking.  As with the London congestion charge, over enthusiastic promotion of EVs in this way may have had some unforeseen consequences that defeated some of the original objectives (by increasing local congestion), but these have not detracted from what overall is a success story.

The Friday night problem[1]

Many Norwegians drive quite long distances to their country retreats at weekends and on arrival seek to re-charge their vehicles. Since a Tesla can require a charge of around 75 kWh, or about a full week of typical household consumption, this creates some big loads on the power network. Over six hours it would create a load of about 12 kW, when the average household loading is usually less than 1 kW. Delivery of recharging over a few hours, when many people may choose the same time slot, has the potential to constitute a major and problematic peak load even for national systems. This would certainly be the case if EV penetration continued at its current rate.  As there are also high geographic concentrations, typically in popular weekend destinations, this also has major implications for thermal and voltage constraints necessary to maintain stability in local distribution systems, and hence for investment in and management of those networks. These are unanticipated demands for large amounts of energy and power, often concentrated at particular parts of the distribution network. In a UK context we can imagine the effect of Bank Holiday “get away” traffic to Devon and Cornwall for example, Cornwall already being a county with potential connection problems in relation to the National Grid.


Norwegians are clearly aware of the general issue and an article by Karolin Spindler describes attempts to analyse it in particular contexts and to anticipate possible load shapes posed in particular conditions. But the more general question is one for future operational management of battery or other storage options in the context of low carbon power systems, and for the investment in local systems. Although it may be possible to adopt a “predict and provide” approach, this may imply a high level of potentially wasteful investment in banks of local batteries.  This may be part of the answer but a complete answer almost certainly requires that the conventional utility business model for the supply of power has to change. Offering consumers a choice between:

·         having the right to instant recharging but only at a premium price,

·         rationing demand by local peak charges,

·         organised pre-booking of charging slots

·         or some combination of the above

The Norwegian example will set some interesting challenges. None of these should be insurmountable, but the transport sector, and other factors, will require a radical re-think of the ways we buy electricity. And these rather technical considerations will also be relevant to the ultimate balance between EVs and the other low carbon option - hydrogen powered vehicles.

[1] I have not been able to verify this anecdote, but in this case I am inclined, in mitigation, to plead what I shall call the Boris Johnson defence.  It may not be true, but something like it is very likely to have happened or to happen in the future. In this context, and unlike the case of the recycled teabags or the Euro-coffin discussed by Mr Johnson with the Treasury Select Committee , it is a useful illustration of the kind of unexpected consequence that needs to be covered in thinking through the technicalities of a system with major electric vehicle penetration.

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