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| Confused about PHEV, Hybrids, etc... |
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| tom66:
Other thing about synfuels is using them ... they're not exactly efficient in the whole system. Hydrogen production and use roundtrip efficiency is about 50% in most optimal case. (70% electrolyser best case, 70% state-of-the-art fuel cell, zero loss of hydrogen, zero cost of cryogenics.) Synfuels are worse if just combusted - production efficiency around 60% and combustion of nat gas in an ICE (e.g. some cars can run on nat gas) or CCGT (30-40% each) would get somewhere around 20-30% round trip efficiency. There will be a part for either in the future but their high costs compared to using the energy to charge a battery and drive a motor (60-70% round trip efficiency) will be a lot harder to compete with. Consequentially they will be only used in applications where the cost of electrification is too high or manifestly impractical (e.g. aircraft on long haul routes.) I expect to that end we will still see ICE cars for sale long into the future but they will be progressively taxed out of existence or will only be permitted if they can run on a synfuel. Or maybe this is where hydrogen will find itself. Long haul trucking has been mentioned as an area where EVs are impractical. I'd like to see overhead catenaries become more common (there's a line under test in Germany.) These vehicles use diesel or batteries to power their route when off the cable. Would be interesting to know how much of the highway network you'd need to cover in these lines to cover all use cases - the majority of trucks I suspect cover some distance on highway and if the overhead line can charge a battery up at over 250kW for instance then you might only need a ten miles of line for some sections followed by long gaps. Probably position the lines close to existing power infrastructure. Working out how to bill the customer will also be interesting. Electric meter in the truck? |
| Miyuki:
--- Quote from: tom66 on August 05, 2022, 03:21:51 pm ---Long haul trucking has been mentioned as an area where EVs are impractical. I'd like to see overhead catenaries become more common (there's a line under test in Germany.) These vehicles use diesel or batteries to power their route when off the cable. Would be interesting to know how much of the highway network you'd need to cover in these lines to cover all use cases - the majority of trucks I suspect cover some distance on highway and if the overhead line can charge a battery up at over 250kW for instance then you might only need a ten miles of line for some sections followed by long gaps. Probably position the lines close to existing power infrastructure. Working out how to bill the customer will also be interesting. Electric meter in the truck? --- End quote --- I do not know how reliable are current german highway overhead lines. But I know for city (trolley)buses the system is very fragile and needs huge maintenance. Especially when it has crosssections and switches (or how they call it when you split lines). Both lines and centenary damage are common. I expect short straight charging lines will be more reliable. As those complicated areas are what cause most issues. Bumpy roads are also a big problem for them. Yeah power stealing sounds like a possible issue |
| nctnico:
--- Quote from: tom66 on August 05, 2022, 03:21:51 pm ---Other thing about synfuels is using them ... they're not exactly efficient in the whole system. Hydrogen production and use roundtrip efficiency is about 50% in most optimal case. (70% electrolyser best case, 70% state-of-the-art fuel cell, zero loss of hydrogen, zero cost of cryogenics.) Synfuels are worse if just combusted - production efficiency around 60% and combustion of nat gas in an ICE (e.g. some cars can run on nat gas) or CCGT (30-40% each) would get somewhere around 20-30% round trip efficiency. There will be a part for either in the future but their high costs compared to using the energy to charge a battery and drive a motor (60-70% round trip efficiency) will be a lot harder to compete with. --- End quote --- Don't fall into the trap of looking at efficiencies alone. In the end the only thing that counts is the price you pay as a consumer. What synthetic / bio fuels inherently solve are storage and transport. When I look at my electricity bill (excluding taxes) it turns out that about 50% of the costs are transport costs. So a decrease in generating efficiency of 10% would translate to only 5% more expensive electricity (and vice versa). --- Quote from: Miyuki on August 05, 2022, 04:39:28 pm --- --- Quote from: tom66 on August 05, 2022, 03:21:51 pm ---Long haul trucking has been mentioned as an area where EVs are impractical. I'd like to see overhead catenaries become more common (there's a line under test in Germany.) These vehicles use diesel or batteries to power their route when off the cable. Would be interesting to know how much of the highway network you'd need to cover in these lines to cover all use cases - the majority of trucks I suspect cover some distance on highway and if the overhead line can charge a battery up at over 250kW for instance then you might only need a ten miles of line for some sections followed by long gaps. Probably position the lines close to existing power infrastructure. Working out how to bill the customer will also be interesting. Electric meter in the truck? --- End quote --- I do not know how reliable are current german highway overhead lines. But I know for city (trolley)buses the system is very fragile and needs huge maintenance. Especially when it has crosssections and switches (or how they call it when you split lines). --- End quote --- I have passed under the overhead lines test track in Germany a couple of times. It is not like a trolleybus system. More like the system you see on a train. I doubt it is unreliable since the mechanical principle is very simple (just like it is with a train). I doubt though the system as it is currently installed in Germany is capable of doing serious charging. Imagine 100+ trucks (the stretch is 5km long!) charging 1MW each. Even big railway stations can't deliver that much power; trains have to take turns pulling out. |
| tom66:
Re catenary power, the 25kV AC lines that power most trains can easily provide 500kW to a train as that is what is required to cruise at 125mph. If you scaled that up, you might be able to get several MW. These are typically powered every few miles by small substations located along the line, connected to 275kV+ infrastructure. How much power does a truck need? We can estimate it from the Volvo electric trucks, e.g. Volvo FH has up to 300km range in 4x2 axle configuration with 560kWh battery so crudely 1.86kWh/km and at 90kph that's 167kW. So to charge the battery and maintain cruise you would need 250kW+ per truck, assuming that net power is averaged for hills. Length of a truck is 16.5m and safe following distance at 90kph is 70m, so a 1km section of overhead line is supporting an average of 11 trucks. That would be ~2.5MW ... it doesn't sound extraordinarily high for 25kV line (100A @ 25kV, so 3-4x conductors would probably be ok.) Some intelligence would be needed in the case of traffic jams or slowdowns. How do you communicate an overall power limit of 3MW for example ... maybe load on the line should be determined by voltage sag, or by vehicle speed. Would it be better to regen energy back into the grid or into the truck's battery? I also wonder if ~25kV HVDC would be better than AC - most trains use onboard 50Hz transformers which add some weight. Edit: maths error, power of ten, d'oh |
| nctnico:
Trucks in that area of Germany usually drive bumper to bumper. Not 70 meters apart. Often you can't even squeeze your car in between to take an exit! |
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