Batteries are the major technology being proposed for the decarbonisation of transportation, but not the right technology. It has a number of major problems, some of which have no technical fix and others whose fix would be prohibitively expensive.
- Grid Reinforcement: All the EV chargers would require tripling (at least – maybe up to 6x reinforcement) of every single level of the grid from the domestic connection through to the transmission grid, and all transformers and substations in between.
- Charging: A huge proportion of the population don’t have anywhere to put a personal charger and car, meaning that they’d have to use communal facilities which would lose them a long time in the day away from home, as well as increasing their costs greatly – and don’t forget, these are the poorer parts of the population. And to be near enough to people’s homes we’d have to have such re-charging stations every mile apart or so. And we’d have to kill the rush hour, as all would be wanting to use them at the same time – smart charging only works when the vehicle can be left in a personal parking space attached overnight to a personal charger, not when these are communal and the vehicle will have to be moved to allow the next vehicle to use the facility. And fast charging is the fastest way to destroy battery life.
- Weight and Distance: It’s inappropriate for heavy vehicles (insufficient power density per unit weight and volume) or for more heavily used vehicles (long re-charging times), for both of which hydrogen / fuel cells are better.
- Resource Sufficiency: There isn’t enough lithium in the earth’s crust for all the vehicles of the world, even less cobalt and even less rare-earth metals. If the 40-60 gigafactories currently planned world-wide are built, they would exhaust the lithium deposits in all current and under-development fields in 2-10 years according to figures from The Economist. And that’s without considering grid-connected batteries (a roughly equal amount proposed) or portable devices. Or its short asset life and lack of recyclability.
Nobody has ever addressed these issues while worshiping in the pro-battery faith. They just respond with pieties such as “lithium isn’t the only type of battery”, ignoring the practicalities that led to lithium dominance today.
Hydrogen / Fuel Cell Vehicles
As for hydrogen, the only reason why electrolysis is so expensive is because the only two technologies being promoted are PEM (expensive, especially as the membrane is a costly consumable item, and limited in scale) and alkali (expensive and noxious). Other electrolysis technologies are not being funded – I know of two such that have real potential for large-scale electrolysis cheaper than steam methane reformation, which is the current principal source of hydrogen for industrial use.
Hydrogen-powered fuel cell vehicles avoid all these issues:
- There’s no resource scarcity;
- Hydrogen can be distributed through the gas grid;
- Fuelling would be very similar indeed to current petrol and diesel refuelling, in both time and method;
- Fuel cell vehicles can carry more range and power, and are more quickly and easily refuelled during the day/journey.
Vehicle to Grid
A response is that this fails to address the requirements of the grid which can be supported by Vehicle to Grid (V2G) storage. However the assumptions and forecasts relating to this require some challenging; for example,
- All the cars in most developed countries, if turned into EVs that are 100% used for grid-connected storage, would account for only a part of the storage needs – they consume similar amounts of energy to the entire electricity grid, with only a 2-4-hour range, only half of which at most (if the system works flawlessly) would be available to the grid. Therefore it lacks the duration to provide true back-up for renewables.
- Where they charge from solar power (office, shopping), which is the proffered model, differs from where they would operate as grid-connected batteries, and nobody has proposed a cost-effective model for the financial flows.
- Most people don’t want their vehicles on less than half charge, which halves (or less) the energy/storage available.
- The bulk of the need for the storage is in the evening, when vehicles’ charge is lowest, yielding a grossly disproportionate multiplication of point 3.
- To roll out cars-with-solar widely, a high proportion of the parking spaces in the country would have to be fitted with chargers – who would bear the cost of that?
The above-listed challenges would need to be answered for V2G storage services to be reliable. And it appears that all these V2G proposals assume 100% efficiency in V2G services, which will not be attainable: a perfectly new battery requiring no cooling yields ~96% efficiency, whereas one approaching its end of life yields ~75%, so a reasonable assumed average efficiency would be ~85%; then there are converter efficiencies – 90% is reasonable, which has to be applied twice – once for charging and once for discharging. The total round-trip efficiency is therefore 0.85 x 0.9 x 0.9 = 0.6885 or 69% round trip, or about the same as large-scale long-duration storage.
Analysing this roughly,
- Vehicles will be at different states of charge, so assume 50% charged.
- Travelling capacity will need to remain in the vehicle, so halve that to 25%.
- Over its life, it loses ~20% of capacity, so average battery capacity is reduced by 10%, cutting the available amount to 22.5%.
- We can assume that no more than about ⅓ of such vehicles are left in personal parking spots attached to personal chargers overnight, so the capacity available to the grid is only ~7.5% of total EV battery capacity.
- Applying the 69% round trip efficiency, this drops to 5.2%.
- A typical car battery has 50kWh capacity, and there are ~30 million on the road in the UK, so available storage capacity is 7.76GWh.
This looks good until it is compared with the need: after sunset on a windless winter evening the country today consumes ~42GW x 5 hours = 210GWh, forecast by National Grid to double by 2050.
And don’t forget that all this consumes battery life.
Therefore the benefits of load shifting (smart charging, i.e. changing the time at which batteries are charged, again only available for the minority of vehicles being charged in private spaces on dedicated chargers) is their greatest benefit to the grid, with V2G (the ability to put charge back into the grid) a secondary benefit confined to smoothing small peaks in demand.
Large-scale long-duration storage is much more cost-effective than using EVs for either load shifting or V2G. The other draw-backs of EVs far outweigh any advantages for the majority of vehicles – the ⅔ which are heavier duty and/or more intensively used, which may account for over 90% of mileage driven.
Therefore EVs are best suited for short-distance light-use applications.
And both money and effort needs to be devoted to developing and commercialising non-PEM electrolysis technologies, and rolling out hydrogen fuelling points to filling stations everywhere.