The country is going electric. There is very little choice in this, particularly now that a Brexit deal has been done (if it hadn't, the collapse of the automotive industry would have meant we could only use what someone was prepared to supply).
Hydrocarbon fuels are extremely energy rich. This can be thought of as calories per kg - think double chocolate cake with extra thick icing. By contrast, other options are much lower energy density. Battery storage is more the equivalent of a dry cream cracker. This gives rise to the much reduced range, even giving up the boot space. This is the main limitation to conversions. In a purpose-built vehicle, the cells are made up into modules, the modules into packs, designed to fit within the vehicle frame, effectively a ladder chassis, to keep the centre of gravity low and make space available above where needed. In a retro-fit conversion, you are limited to available sizes and shapes of packs so they can't be packed so well and tend to end up higher in the vehicle. There is also the issue of weight distribution to manage.
Power delivery is more of a challenge with high current/low voltage, requiring thicker cables and more heat management, hence the increasing tendency to push up drive voltages. Modern systems are now being designed around 800-900V. Battery management systems are also a key component - get it wrong and overdriven cells can set a module on fire - these will keep burning underwater so although there is no explosion risk, once your batteries catch fire they will keep going so there is nothing to do but stop by the side of the road and wait until everything flammable has burned.
Vehicles which were not designed for electric propulsion are often best converted by keeping the drivetrain. The gearbox can be removed but it is often left due to the ease of coupling to it. Multiple motors are possible but make it a lot more expensive to design, configure and build when you consider the battery management system and cabling. For a conversion which will not be optimised anyway, the gain is very small compared with the cost.
I think if I was converting a S2 it would be a choice between keeping the main gearbox for the feel of driving a classic vehicle vs. replacing the main box and bolting the motor on the side of the transfer case to decrease weight and save space. The latter would allow the whole engine bay to be filled with batteries which, together with a layer on the tub floor, would probably give a range of 100-150miles - it would be interesting to see whether that compares with any known figures. For most people for most journeys that would be fine, assuming you have a charging point at home. You should be able to make most journeys within that range, although attending rallies or doing long distance towing etc. would become more of an extended logistical exercise.
Hydrogen is an entirely different proposition. There are two main questions - combustion vs. fuel cell, and storage method. Combustion is long-established and hydrogen will run in a petrol engine as a direct replacement with a few setting tweaks. Fuel cells have been around for over 150yrs but have not been commercially adopted on a mass scale. Think of them as being like a battery where you flow the energy source in continuously on demand, rather than pre-charging it. They are very efficient but the cost of the platinum catalyst is not generally economically viable. One major change over the past 20 years is the shift from brown hydrogen to green hydrogen. Brown hydrogen is made by processing carbon (e.g. coal) with water to create carbon monoxide and hydrogen. You then have to remove the carbon monoxide as otherwise it blocks up the platinum catalyst and stops it working - the energy required for regeneration counters the improved efficiency. Switching to hydrogen generation by splitting water with electricity is far more promising, particularly as a use for renewable energy sources which are often out of sync. with demand (what do you do when it's windy in the middle of the night?) - this is likely to result in major growth in hydrogen production and use, although the electricity companies are not yet ready for it. The much greater challenge is storage. Stored at atmospheric pressure, hydrogen has the calorific value equivalent of a piece of celery. Being a gas it can be heavily compressed but a suitably robust storage container which will not puncture is heavy and it still won't carry as much energy as a liquid fuel (hydrogen cannot be liquefied like LPG). If you took a standard welding gas bottle and knocked the end valve off it would go off like a missile and punch holes in walls - add to that the flammability/explosive potential and you can see why carrying hydrogen around under high pressure in every car represents a challenge. There are other approaches under development such as storing as a solid metal hydride which decomposes to release the hydrogen; these work but are heavy so not well suited to transport.
A vast amount of money has been thrown at trying to improve cell chemistry to increase energy density further in batteries but there are some fundamental limits. Standard electric cars will be at around 150Wh/kg; Tesla have hit around 250Wh/kg. Electric flight requires 400Wh/kg as a starting point; some ultra-high performance (but virtually unmanageable) batteries can achieve 1500Wh/kg. Petrol and diesel are at around 10,000Wh/kg. This suggests we are either going to have travel very heavily rationed in the future, some radical technology breakthroughs which are not yet even on the horizon, or we will actually be using hybrids for a long time.
Alec
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Topic: Tumbling cost of Electric Vehicle battery packs..... (Read 3663 times)
