Reply to post: Re: Hmmm

Full shift to electric vans would melt Royal Mail's London hub, MPs told

Jellied Eel Silver badge

Re: Hmmm

Nope, it's a huge problem that will result in even higher electricity bills.

Musk hasn't cracked solar roof tiles. He's sort of trying to sell them, but they're very expensive and not likely to produce much power. AFAIK there aren't any in the wild yet to produce real-world stats. Problem is..

Solar gives you maybe 1kW/m^2 of potential energy, ie solar irradiance at surface. An EV may have a 100kWh battery, so depending on charge rates (10-120kW), you'd need 10-120m^2 or more per vehicle to charge it. But solar panels aren't 100% efficient, so you'd need more. And you can't rely on a constant 1kW/m^2 because that changes as the Sun's angle changes, or seasons change, or it's cloudy, or pigeons/London grime covers the panels.

And of course at night, solar's usefulness drops to zero. Then Powerwalls or other displacement activities add cost. So if you're using solar to charge a Powerwall during the day, you can't be using that energy to charge a vehicle. Or do any other useful work. Assuming the Powerwall's fully charged, you might then try charging a vehicle from it. But a Powerwall has a capacity of 13.5kWh, and the Model S wants 100kWh.. And the cost per kWh for a Powerwall is around $400

Which is around 10x more than current wholesale electricity prices, and a lot more than diesel.

Then there's the challenge with power density, ie trying to charge a lot of vehicles at the same time, so say 100 @ 120kW for 'fast charging', which would mean a substation and hefty DC conversion facility installed in your car park. Fleet owners won't want to be paying those sorts of costs any time soon.

But this is nothing new. After all, the first EV's were around a hundred years ago, and the problems are well understood.. By engineers, if not politicians.

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