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Great idea to electrify transport and this bus idea makes a whole lot of sense on a circular and regular route.
Electricity however is ubiquitous. It doesn't matter if it is produced by coal, solar wind or hydro, what comes out of the generator or inverter is exactly the same: Electrons moving in AC sine wave form.
This means that the bus can be charged up from anywhere really and just needs to access the electricity grid. The Solar panels really don't run the bus, they are just ofsetting the power drawn down by the bus when it plugs in.
This is important to understand when it comes to siting wind or solar panels. They should be placed in the area where they will operate most efficiently. Solar would be very inefficent on the Gold Coast (I jsut spent two weeks there in November and most days were overcast).I don't know about the wind profile but I imagine that the top of the Gold Coast Escarpment would be the best place on the coast but may be not the best place in QLD. I also think that NIMBY would stop a wind farm pretty quickly on the escarpment.
The point is that any renewables will generate electricity and this energy must be used instantly or stored either in batteries, reverse hydro, compressed gas or even chemical electrolysis.
The problem with renewables is thay are sporadic and unreliable. Wind and solar cannot provide baseload yet so we are left with "averaging out" the contribution these inputs make vis-a-vis the baseload coal stations. But that implies that the coal fired station is indespensible which should make us stop and think about the wisdom of adding a new technolgy when it does not repalce the old one and only serves to entrench the perception of "clean" electricity when the truth is somewhat different.
It might be OK to run one bus with an acre of solar panels but it is relly just a gimmick unless it can be shown that it can be scaled up and run a whole cities buses this way.
The only way I could see this operationally practical is to have standby batteries being charged and quick changeovers of battery cells for example when the bus stops to take passengers (think grand -prix type tyre swap outs). This would require at least two sets of batteris per bus and probably more. It really depends on if the batteries can be charged at the same rate as they are being discharged in the buses.
I suspect probably not, which means that an even larger solar array charging larger banks of batteris would be required. An assembly line of batteries at various charge stages would need to be built big enough to ensure 100% availability when each bus demanded a top up. The efficiency of this type of arrangement would be extremely low and this would make it very expensive.
I am also very sceptical of the zero emissions argument about solar and wind. Photo voltaics especially have very intricate manufacturing processes which use enormous energy inputs, and wind turbines are built from steel towers and copper generators.
The materials in these renewable energy harvesters have already created huge amounts of GHG before they generate one watt of power. We must take into account the manufacturing cost in energy terms and balance that out against the energy that will be harvested.
We also have to ask how the net energy, after the payback of manufactuing energy, will be used? I don't really know but my guess is that by the time you reach the profit point, electricity demand will have grown to the point that both the CFE and the RE will be used to the max and not one tonne of GHG will be saved. The only thing RE's might do is slow the growth of CFE generated GHG.
"The only thing RE's might do is slow the growth of CFE generated GHG."
- There. You said it. That's the point exactly!
As far as Energy Balance, this has been reintroduced here regularly, so you can look it up yourself (Google NREL), but Solar Electric {PV) HAS been evaluated as recovering its Embodied Manufacturing and Materials Energy within the first year or three, depending on the panel type, while continuing to be productive for two to three DECADES afterwards, and being highly recyclable thereafter. No moving parts, can sit on the rooftops or BECOME the rooftops, which were expensive to build in their own rights.. and not bother anybody. As 'imperfect' and 'mortal' technologies go, PV has a lot going for it.
Finally, you said;
"The Solar panels really don't run the bus, they are just offsetting the power drawn down by the bus when it plugs in."
What's the difference? This is misleading. If these panels are Grid-tied, they are putting watts into the grid and the bus is taking them back out.. not the 'same watts' per se, just like the dollars you put into the economy are not necessarily the same ones you get back when you are paid for your work, but what's the difference? You seem to be implying that the inputs from this system 'aren't really' covering the draws on it, or at least your statement could easily be read that way..
The point is that PV panels (or Wind, etc) CAN run a bus, provided you've installed enough of them. The details of Charging, Battery Transfers or whatever is done to get that charge onto the bus is worth knowing, but is not such a dramatic challenge as you suggest. Even the transfer of a New Battery Pack every few hours (the article said the Zebras give them a 200km or 120mile range), while cumbersome would hardly have to be an extreme engineering challenge, though I would expect that the future really will lie with Trolley Buses as Alan Drake includes in his 'Light Rail Now' plan for transp. http://www.lightrailnow.org/features/f_lrt_2006-05a.htm .. but that said, the solutions will take on many varying forms, and Battery Buses can certainly have a place in that.
Bob Fiske
Snowed in in Maine!
The point I ws trying to make here is that it will slow the growthreduce green house gases. Waht usually happens when extra generating capacity comes online is that we find new ways to use it and the economy grows. While grid comnected buses may be a good thing for an oil constrained world, they will do absolutley nothing to reduce green hosue gases and could even make us more dependent on coal and natural gas as tehse systems will be required to provide 100% redundancy to renewables if and when they are ever able to provide baseload. The chances of anyone investing billions of dollars in FF electricity generation just to see it sitting idle is nil.
This so called solar powered bus is a feel good project. It is sexy and makes good headlines and gives the politicians something to pat themselves on the back for. But it is not scalable in any meaningful way and ultimately is a sistraction from what the reall point is and that is why hordes of people need to be moved each day anyway!
If this thing is done on a larger scale it could be possible to average out even long-term fluctuations of renewable power.
If the recharging station for example keeps an array of standard battery packs for say 50 buses and 200 NEVs the amount of energy stored would probably be enough not to need a grid backup.
The real problem with such schema is that it would be very hard to implement. Swapping batteries would be a very cumbersome operation, and batteries themselves are yet too expensive and quickly degrading toys.
I have seen a suggestion that could help such schema though - if the battery is using liquid electrolyte which participates in the charge-discharge process (e.g. lead-acid), one could just leave the battery pack intact, while draining and "refueling" just the electrolyte liquid. However I can imagine the safety issues of changing the sulfuric acid in a lead-acid batteries, so it must be some other battery chemistry allowing for this.
P.S. I have repeated the point you made many times (falling of deaf ears unfortunately) - while renewables require considerable fossil fueled backup it is dubious to promote them as their replacement. If you need to add one coal power station after you build 100 wind turbines, how exactly are you helping the environment? Of course while penetration is low this problem is not so significant, but expecting a 30 or even 20% renewable powered grid is a pie in the sky (to counter the Denmark example which usually pops up - they are doing 20% wind using their heavy interconnections with other grids - not many places have this luxury).
A range of 200km will be enough for the day. Here in Melbourne buses have an average speed, what with traffic, no dedicated bus lanes, and stops, of about 20km/hr. That lets the 200km range bus travel for 10 hours, and the things only run from 6am to 11pm at most. In practice about half the buses run all day, and the other half run in the peak times (7am-9am, 4pm-6pm). So buses are constantly being shuffled in and out of depots anyway to cope with varying timetables throughout the day. It'd be trivial to turn those into recharging times; when the driver finishes their shift, they plug the thing in.
Placing batteries in busses is a silly idea!
The first busses to go electric should be on the bussiest lines, and since busses run the same route most of the time, overhead cables is the way to go.
We should choose the bussiest lines to get most busses to use the same wire.
We had some electric busses in Copenhagen a few years back, and I never understood why they got rid of them.
Rune
SF Electric Trolley Bus
http://www.youtube.com/watch?v=6vAGEaKFuyY