I had an idea, this last week.
We went on vacation, recently. While in Seattle, WA and Vancouver, BC, we saw plenty of electric busses. They have long poles on the back which hold up electric contacts, which connect with overhead catenaries (conductive, electrical wires) to provide current. Plenty of people complain about what an eyesore those cables are. Additionally, since the busses can only go where the wires go, the routes are kinda limited. It's a bit like a cross between electrically-driven light rail and traditional bus service. The electric busses can only go where the catenaries go, but they don't have the added expense of building rails.
So, what if you could make a bus which only occasionally needed connectivity to recharge?
The bus drives around on normal city streets. Occasionally, it pulls into a bus stop and, while passengers are loading and unloading, it puts a contact up or down, connects with electrical power and rapidly recharges. I could see two ways to do this:
- the bus has a pantograph on the roof, which extends up to an overhead catenary, which is only found at select bus stops
- the bus puts a "foot" down onto the ground, which sits on top of a inductive charging device (like the "paddles" used on the EV-1, only much larger); this transfers a significant amount of current, even when wet, without the possibility of electrocution, so it can be built into the road
There would be a limited number of charging points, so there would still be some limitations on routes, but not nearly as much as a bus which needed a constant electrical supply. Minimal eyesores, as well. The latter could be built into the road, keeping the overheard area completely clear.
Various companies are working with ways to make high-charge-rate (and high-discharge-rate) batteries, and there are always supercapacitors, but I'm thinking of running a pump to build up hydraulic pressure, then run the bus as a hydraulic hybrid. If you could get enough hydraulic capacity to cover 5 miles of level ground, you could hit quite a few stops without needing much more infrastructure than a traditional, diesel-powered bus. And yet, you wouldn't have the pollution of the diesel-powered bus. Instead of waiting on new technologies which are still under development or under limited production (the aforementioned batteries and supercaps), hydraulic hybrid systems tend to use off-the-shelf parts.
This idea could be extended further to light-rail systems. Since steel wheels on steel rails have less rolling resistance than rubber tires on pavement, a given amount of hydraulic storage would go further in a light-rail system. Also, since the vehicles tend to be larger, they would (presumably) have more room for hydraulic storage.
For either bus or light-rail, the pantograph would seem to be the better idea. If you want either vehicle to be able to recharge without stopping, you could put in a short distance of electric catenary (say 1/4 mile) and the vehicle could contact it while in motion. You don't have to be stopped to use that system, unlike the inductive charger.
Imagine a hydraulic hybrid bus, without an actual engine on board. It would have an electrically-powered pump, but the electricity would come from outside sources.
I'd like to see that happen.