General > General Technical Chat
“Battery EV” vs “Hydrogen Fuel cell EV”
nctnico:
--- Quote from: tom66 on March 30, 2022, 10:30:55 pm ---Well, that source I linked suggests a production rate of 63kg/h for a compressor of 177kW. If we assume every car is filled empty to full (the Mirai holds up to 5kg though an undisclosed amount is 'reserved'), then the station can do about 10-12 cars per hour without downtime. I assume that if you want to have something close to a petrol station flow rate you'd need about 60 cars per hour, so you're looking at 1MW grid connections for the compressors -alone-. That kind of makes the argument that superchargers will present grid connectivity issues a bit moot. That's also ~15kWh of embedded energy per fill-up on compressor power alone, which surely further impacts efficiency.
--- End quote ---
Cost wise the impact of compressing the hydrogen is minimal so efficiency doesn't matter here. As I wrote before: thinking in efficiency leads to nowhere. Think in cost per km instead.
When you have hydrogen on-site it makes no sense to have a big grid connection. Convert it to electricity on-site.
james_s:
--- Quote from: nctnico on March 31, 2022, 12:46:01 am ---When you have hydrogen on-site it makes no sense to have a big grid connection. Convert it to electricity on-site.
--- End quote ---
You're never going to have hydrogen on-site, it isn't something that is naturally occurring in pure form, you have to "make" it by extracting it from other compounds. It makes even less sense to use hydrogen for land based energy storage than it does to use it to fuel moving vehicles. At least with a vehicle energy density, weight and filling time matter to varying degrees, on land you're better off using a big pile of batteries, even if they're something bulky and heavy like lead acid.
nctnico:
--- Quote from: james_s on March 31, 2022, 01:07:58 am ---
--- Quote from: nctnico on March 31, 2022, 12:46:01 am ---When you have hydrogen on-site it makes no sense to have a big grid connection. Convert it to electricity on-site.
--- End quote ---
You're never going to have hydrogen on-site, it isn't something that is naturally occurring in pure form, you have to "make" it by extracting it from other compounds. It makes even less sense to use hydrogen for land based energy storage than it does to use it to fuel moving vehicles. At least with a vehicle energy density, weight and filling time matter to varying degrees, on land you're better off using a big pile of batteries, even if they're something bulky and heavy like lead acid.
--- End quote ---
You may think so but how are you going to get the batteries charged somewhere high up a mountain or in the middle of nowhere? Hydrogen can be delivered by truck everywhere as long as there is a road. Also hydrogen is cheaper for storage for periods over 8 hours compared to batteries. Looking at what is being developed and rolled out at the moment, hydrogen is going to play a big part in energy delivery and storage anyway.
tom66:
--- Quote from: nctnico on March 31, 2022, 12:46:01 am ---When you have hydrogen on-site it makes no sense to have a big grid connection. Convert it to electricity on-site.
--- End quote ---
Convert hydrogen into electricity on-site - at an efficiency of 60% and with all associated costs of doing so - instead of using a grid connection directly?
Why? Hydrogen as storage might make some degree of sense (e.g. large grid-scale storage of excess renewables), but grid connections are far cheaper, let someone else worry about doing the conversion.
Cost per km, hydrogen will always be more expensive than electricity if hydrogen is produced from electricity. Even when it's produced from natural gas it's about the cost of diesel currently (per km).
Miyuki:
--- Quote from: nctnico on March 31, 2022, 01:49:02 am ---
--- Quote from: james_s on March 31, 2022, 01:07:58 am ---
--- Quote from: nctnico on March 31, 2022, 12:46:01 am ---When you have hydrogen on-site it makes no sense to have a big grid connection. Convert it to electricity on-site.
--- End quote ---
You're never going to have hydrogen on-site, it isn't something that is naturally occurring in pure form, you have to "make" it by extracting it from other compounds. It makes even less sense to use hydrogen for land based energy storage than it does to use it to fuel moving vehicles. At least with a vehicle energy density, weight and filling time matter to varying degrees, on land you're better off using a big pile of batteries, even if they're something bulky and heavy like lead acid.
--- End quote ---
You may think so but how are you going to get the batteries charged somewhere high up a mountain or in the middle of nowhere? Hydrogen can be delivered by truck everywhere as long as there is a road. Also hydrogen is cheaper for storage for periods over 8 hours compared to batteries. Looking at what is being developed and rolled out at the moment, hydrogen is going to play a big part in energy delivery and storage anyway.
--- End quote ---
Also, it is "easy" to have months worth of energy in hydrogen
Batteries are good for small scale (phones, tools cars) or quick cycles, like day/night cycle
But for long-term storage, like weeks or months. Other methods like hydrogen or maybe flow batteries to some scale are needed.
There is no way to have a battery for 2 months worth of energy next to a house.
Also, there is no way for a truck or ship to have a battery when you want to replace high-efficiency ICE which is commonly over 40% and can reach over 50% efficiency for long hauls
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