| ▲ | martinald 17 days ago |
| While I agree with you; just to be clear it's not "slightly" beef up the local transformer. If you imagine a medium sized depot with 50 buses stabled at any one time, and 300kW chargers (I believe you could go higher), that's 15MW peak which is not trivial to add in many cities overnight. You really need some sort of HV connection for that kind of load, the existing local LV distribution grid isn't going to handle it. I do definitely think green hydrogen has a big future ahead of itself though. We still use an absolutely ridiculous about of H2 in industrial processes (especially fertilizers). Europe could produce huge amounts of fertilizers in the summer in the future with all the excess solar and wind it has via this method. It seems to me hydrogen skipped a step - focus on replacing hydrogen feedstocks in industrial processes directly with green hydrogen, instead of replacing stuff up the chain that can be done with batteries directly anyway. |
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| ▲ | londons_explore 17 days ago | parent | next [-] |
| Any decent sized installation will use current clamps at the local transformers to scale the charging rate up and down depending on other users in the local area. Ie. in the evening whilst everyone has their ovens on, charging might only be 3 kW per bus, but then at 1am when everyone has gone to bed, it can be 30 kW per bus. Using that approach, you can get far more capacity out of old infrastructure. Unfortunately, some utility companies aren't amenable to that approach, and instead insist you pay to upgrade the infra, since to them it's a free upgrade. |
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| ▲ | martinald 17 days ago | parent [-] | | Not really. Buses need to be charged whenever, not just overnight (it creates enormous logistical problems otherwise). A typical bus route running 5am to midnight say is not going to last with one charge, depending on length. Also, if it is a cold night and everyone leaves electric heating/heat pumps on, what happens then? Noone can get to work the next day? Regardless most urban transformers are not going to have 15MW of overnight capacity spare even on a good day. The largest LV substations might be 30MVA in the UK at least - they won't just have half capacity suddenly free. | | |
| ▲ | adgjlsfhk1 17 days ago | parent | next [-] | | Lots of busses are split shift. i.e. they drive from ~6:30am to ~9:30am and ~4pm to 7pm. This means that a significant portion of your bus fleet will be able to charge during the middle of the day when energy demand is relatively low and there's a ton of solar power. As an aside, we have so far really dropped the ball on level 1 electric vehicle chargers at offices. As solar power and EV numbers increase, it's pretty obvious that we want more cars charging during the day and fewer charging at night. | | |
| ▲ | bluGill 16 days ago | parent | next [-] | | Split shift is a stupid idea that needs to die. It only works for people who always work '9 to 5'. Work a different shift and you drive. Need to go shopping - just drive. Have a day off - drive to whatever you do. Going to church one sundap - drive. Have a kid who might get sick at school - you better drive everyday. | | |
| ▲ | ViewTrick1002 16 days ago | parent [-] | | In cities with working public transport it aligns the schedules to accommodate the ridership. Which sucks a bit in the late evening when headways might become a bit long. The absolutely largest peak is in the morning and then a smaller one in the afternoon. So you might have a baseline like every 10 or 15 mins and then in rush hour it is every 3 or 5 mins. | | |
| ▲ | bluGill 16 days ago | parent [-] | | again. Stupid. Complete nonescense that comes from people who drive themselves and think of transit as for 'lesser people'. humans have places to be. They shouldn't wait for transit. and they mostly won't. |
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| ▲ | linedgolyi 17 days ago | parent | prev | next [-] | | >we have so far really dropped the ball on level 1 electric vehicle chargers at offices Our govt. really did a disservice to transition to EVs by slapping on a big tax to anyone even brushing against a charger at work: 120€/year | |
| ▲ | bmicraft 16 days ago | parent | prev [-] | | Where do you live that buses aren't running during most of the day? That just seems absurd to me. Buses in my city run at only slightly reduced (from the rush hour peak) intervals for the whole day | | |
| ▲ | martinald 16 days ago | parent [-] | | Agreed, I assume this is a very US centric viewpoint. Wherever I have been in Europe the schedule is basically the same throughout the day, with reduced frequency in the evenings. Potentially slightly higher at rush hours, but nothing dramatic. Not sure why you are being downvoted. |
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| ▲ | Retric 17 days ago | parent | prev [-] | | The critical bit for infrastructure is generally peak load not simply is anyone using it for anything. A few solar panels and a few batteries on-sight can create a lot of freedom here. City busses don’t need that much energy because as they don’t move quickly, the cargo is light, and regenerative breaking offsets stop and go. |
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| ▲ | m4rtink 16 days ago | parent | prev | next [-] |
| Thats the genial thing about trolleybuses with batteries - there is alread a substantial city wide charging network, that is even distributed and enables on-the-go charging. :) Sure, for regular battery buses without trolley collectors, indeed some new transformers might be needed. But even here, I wonder if you could make it somewhat distributed, with some charging happening at the line terminus where the drivers also often have to take a break anyway. |
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| ▲ | crote 16 days ago | parent | prev | next [-] |
| You wouldn't need 300kW chargers, though! Battery buses have a battery capacity of around 400kWh. Assuming they are stabled for 6 hours overnight, that's only a charging power of 66kW. Suddenly your depot needs a connection with a peak capacity of 3.3MW instead of the proposed 15MW. This can get significantly better in practice. There's a peak transit demand during commute hours, but that means there are quite a few unused buses in the middle of the day. Those can charge at the depot to take advantage of cheap daytime solar. A lot of bus routes are timed, with a waiting time of 5 to 10 minutes at the turnaround point. Place an overhead charger here, and the charging demand can be distributed across the day. As a bonus, this also reduced the battery capacity needed - and the associated lower weight reduces total energy demand as well. Sure, bus depots are going to need beefy connections, but that's hardly an insurmountable obstacle. The ongoing rapid rollout shows that it simply isn't a such a big issue in practice. |
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| ▲ | martinald 16 days ago | parent [-] | | You're oversimplifying on many angles. Firstly you have charging losses - and you're assuming that you can charge at the same rate consistently over the cycle of the charge. Secondly, doing it like that massively reduces operational flexibility. If buses are all late back (bad traffic for example) you would want to charge more aggressively than the 60kW. You can't so you're going to have buses that are low on charge the next day. Finally, it's all a bit moot. In most areas you do not have 3MW of spare capacity on the LV network to suddenly plug into. You're going to need a new HV connection or dramatic LV grid reinforcement, so you might as well put a decent connection in at that point. The cost is basically the same, most of the cost is in permits and civils. Your idea to place charging points at turnaround points is also not as feasible as you make out. It's incredibly hard to do that (TfL massively struggles to get planning for a simple toilet block for drivers at turnaround points) and they are not designed in a way to have buses in a certain exact position to charge often. And even if you could if buses are late they cannot skip the turnaround like now as they need to charge. This will cause massive cascading delays down the route for the rest of the day. Grid connections are the reason rollout is so slow, at least in the UK. There is relatively plentiful funding for it but most depots are now completely maxed out in power availability - any spare capacity has already been used and the LV DNO queue is 10+ years for local reinforcement. |
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| ▲ | smeeger 16 days ago | parent | prev | next [-] |
| a lot of people like to laugh very, very loudly at the idea of upgrading the grid to handle EVs. simply remind them that at one point in time there was no grid at all. the grid is not some magical entity that cant be changed |
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| ▲ | HPsquared 16 days ago | parent [-] | | It's a bit like the difference between building a new house, vs renovating an old one. Different skills are required and the renovation project can actually be more complex than new build. |
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| ▲ | discardable_dan 17 days ago | parent | prev [-] |
| Luckily, humans are rather expert water-boilers at this point in time. |
