City of Milton Keynes adding wirelessly charged electric buses to fleet
25 September 2012
The city of Milton Keynes in the UK is replacing the diesel buses on its Nº7 route with eight electric buses that will use wireless charging. Eight organisations led by a subsidiary of Mitsui & Co Europe signed a five-year collaboration agreement committing to the replacement of the diesel buses with their all-electric counterparts on one of the main bus routes in the city by summer 2013.
The buses will charge when power transmitted from a primary coil buried in the road is picked up by a secondary coil on the bus. 10 minutes parked over a coil will replenish two thirds of the energy consumed by the bus’s route. The primary coils will be placed at three points on the bus route, and the buses will charge in the time scheduled for driver breaks at the end of the route.
The eight electric buses will run seven days a week; removing approximately 500 tonnes of tailpipe CO2 emissions per year as well as 45 tonnes of other noxious tailpipe emissions. The route currently transports more than 775,000 passengers a year over a total of 450,000 miles.
The trial is a partnership between: Mitsui subsidiary eFleet Integrated Service Ltd; Milton Keynes Council; bus operator Arriva; manufacturer Wrightbus Limited; technology supplier Conductix-Wampfler; Western Power Distribution; Chargemaster Plc; and SSE.
The trial was planned and will be managed by Mitsui-Arup joint venture MBK Arup Sustainable Projects (MASP). MASP’s ultimate aim is use the data collected by the Milton Keynes trial to demonstrate the economic viability of low-carbon public transport. This data could be used to kick-start electric bus projects in other towns and cities worldwide.
What a smart decision! Hope that many many more will follow.
Posted by: HarveyD | 25 September 2012 at 08:49 AM
That's the way we do it!
Posted by: Davemart | 25 September 2012 at 10:46 AM
If you do the math, this is a pretty easy route to cover. I mapped this from the Milton Keynes public transport site in to Google Maps and arrived at a distance of 10km, very flat terrain. Here is the map: http://goo.gl/maps/sZu0Z . Given this short route of 10km, and a power draw of about 1.5 kWh/km, this gives a power requirement of 15kWh per charge. They are charging only 2/3 of the required charge, for 10kWh in 10 minutes. This translates into a charger of 60kW, about average for an inductive charger. Hybricon in Umea is using AltairNano LTO batteries, an Opbrid conductive charging station, and charging at 300kW. This means a 100% charge (15kWh) in only 3 minutes.
Posted by: Opbrid | 25 September 2012 at 01:41 PM
The induction charger performance is markedly inferior to Busbaar, which can charge at up to 250 kW.
The question becomes relative cost, including reduced battery cycling with full replenishment of charge. I find it hard to believe that an overhead bar isn't going to have much lower maintenance costs than an induction coil which will get driven over.
Posted by: Engineer-Poet | 25 September 2012 at 02:48 PM
EP:
I don't know if it is the case here, but some induction chargers are covered with concrete, and so one would assume that wear would be relatively limited, although presumably that may come at some energy penalty.
I can't get too worked up about such losses, as electric is so much more efficient than diesels that there is considerable leeway.
Posted by: Davemart | 25 September 2012 at 04:10 PM
@Opbrid:
It would be great to see your system in use in the UK.
AFAIK no-one has plumped for it yet, but one lives in hope.
We have to drastically reduce emissions in the UK or risk huge fines.
Posted by: Davemart | 25 September 2012 at 04:16 PM
E-P; This is the same argument as 'underground cables' in EU versus 'Aerial Cables' all over the place in USA and most of Canada.
I do not live in EU but all cables (Hydro, CableTV, Telephones cables) are underground in our area. Unfortunately, it is not the case in the majority of other places.
Posted by: HarveyD | 25 September 2012 at 04:49 PM
Electrify your buses and trains and go nuclear (buy GE's S-PRISM and destroy your reclaimed plutonium already!) and you deal with both emissions and import dependency.
Posted by: Engineer-Poet | 25 September 2012 at 04:51 PM
Inductive charging IS markedly inferior. It is less efficient (more CO2), has much less power handling capability (slower and/or more bulky), is more expensive and requires a heavy receiving solenoid in the vehicle.
But I am not surprised that some city politicians chose it, maybe because the route does not require 20 yards of overhead rail at one or two stops.
Posted by: ToppaTom | 25 September 2012 at 11:18 PM
The visual impact of the Opbrid Busbaar station has been markedly reduced in the latest version, a single pole and an largish box that contains the charger. Not much more than a streetlight really, and can be combined with a bus shelter. An inductive charger also has a largish charger box - you have to put the charger electronics somewhere!
In either case, you don't have overhead lines like a trolley bus or tram strung throughout the city.
Shorter charge times can translate into fewer buses. If a bus is out of service for 10 minutes each hour charging, this adds up to 180 minutes over 18 hours, perhaps requiring an additional bus to be purchased.
Posted by: Opbrid | 25 September 2012 at 11:53 PM
Opbrid,
It could be not an issue charging time if the chargers are installed more frequent at stops. Anyway buses shall stop for several minutes to let passengers in and out.
Posted by: Darius | 26 September 2012 at 12:46 AM
Putting in more chargers to make up for slower charge speed costs money.
OTOH it is unclear that the premium for buying batteries capable of accepting really fast charge is, so we, or at any rate me, do not have good figures on balance of cost.
Posted by: Davemart | 26 September 2012 at 01:18 AM
Actually, it really isn't clear, and likely depends on the route and the preferences of the bus operator. I personally think that a plug-in hybrid bus is a very good choice in most situations. You can size the battery to a normal run, not over-sized like an all-electric bus has to have. If you run out of battery power due to a traffic jam or other situation, you just revert to hybrid mode and keep going on diesel. Normally you run 100% electrically and just use the diesel for backup. Since all the engineering for hybrid buses has already been done, it is "simply" a matter of adding a bigger battery and a fast charging system. This is what Volvo is doing with their 7900 hybrid. It will be very reliable in all situations, yet act as an electric bus most of the time - very cool if you think about it.
Posted by: Opbrid | 26 September 2012 at 10:45 AM
We gladly paid between $1000 and $2000 extra per household in our area not to have aerial cables. Money (cost) is NOT always the prime mover. There are other joys in life.
A house built on a street with underground cables is much easier to sell and you can double your initial investment and benefit from your stay without all those aerial cables.
Posted by: HarveyD | 26 September 2012 at 02:00 PM
I'm not at all optimistic about the current and near future world economy's health. I have liquidated-sold 70% of stocks and mutual funds that my wife and I had in the last 4 weeks. The remaining is in high dividend essential basic products and services firms. We will stay in a highly cash situation for the next few/many months or as long as the world economy has not turned around. TMC is one the very few exception in our maintained portfolio.
Posted by: HarveyD | 26 September 2012 at 03:08 PM
Having a hybrid instead of a BEV bus also reduces the problem of cold weather heating, although of course you prefer not to run the engine in idle to heat the interior.
Posted by: Davemart | 27 September 2012 at 03:19 AM
An ethanol heater could do a good enough job instead of running the large ICE to keep the cabin warm?
Posted by: HarveyD | 27 September 2012 at 03:51 PM
A house built on a street without bus charging stations is even easier to sell.
Posted by: ToppaTom | 27 September 2012 at 06:13 PM
Harvey, why would you want to burn a liquid fuel to make low-grade heat without harvesting any work from it?
Posted by: Engineer-Poet | 27 September 2012 at 07:39 PM
An CNG burner could be a better idea? Eventually, ultra high efficiency solar cells + low cost e-storage may do the trick.
Posted by: HarveyD | 19 February 2013 at 09:38 AM