So, when we run out of oil, how will we get around?
October 10, 2006
On bikes, of course, but would it hurt to have a little electrical assist?One of the finer books that I have read is Bicycling Science . One of the more astonishing things is how little power it takes to move a human at a moderate pace, if you dispense with the 2000 pounds of armor that we normally use for transportation. Of course, as engines go, we’re pretty wimpy, and many people will balk at riding up a serious hill, especially if they are carrying 4 bags of groceries, especially if (for whatever reason) they are not in good physical shape. If we were serious, we could supply, as part of our infrastructure, an electrical assist.
We have similar infrastructure already; overhead wires for electric busses run on the street right next to where I am typing this, and years ago in San Francisco I often took the electric bus to visit my aunt. The wires for busses are vastly larger than what would be more than adequate for cycling.
A run-of-the-mill electric drill puts out as much power (500W) as a world-champion cyclist, so the motor would not be that big a deal. One problem is passing; with many cyclists on the road, differently loaded, and contributing different amounts of their own power, passing is inevitable. I thought of a couple of ways of solving this. If the electrical contacts were arranged in a checkerboard, and the contacts ended in 3 or more pads, at least two of them would always be contributing power. Here, the contact pads are green circles, and the arrows indicate diodes for providing power (as the bicycle moves, the current on each individual line can be regarded as a gross form of alternating current).
Or, multiple parallel wires could be used instead, and a contact bar with multiple segments would ensure that at least two were providing power.
The cost of the power is not large; if electricity is $.1 per kWH, an hour’s assist at high power is a nickel’s worth of electricity. If this were applied in general, and not just on hills, with no contribution from the rider, that’s 20-25 miles, or an energy cost of a fraction of a penny per mile.
Infrastructure is a much bigger problem. The checkerboard pattern is probably the wrong choice; wires require much less overall material, and also serve to distribute the power, and we’ve got lots of practice stringing wires. It would probably be sensible to put some sort of a covered structure over the wires and roadway. This costs more initially, but adds to the lifetime of the wires, and makes a more comfortable and safer place for cyclists to ride. Wires have the possible advantage of being easily adapted to carrying multiple phases of AC, rather than just positive and negative DC; the diodes don’t care.
I’m not really sure what to think about safety; it’s sort of a compared-to-what issue. Bikes moving much faster than 15mph are a good deal more vulnerable to headers if stopped quickly using the front brake. Perhaps people will make greater use of recumbents, or perhaps they will use ABS braking systems (see Bicycling Science for a discussion of one), or perhaps they will use bicycles where more of the weight is moved to the rear (for example, a tandem, or an xtracycle). Cars are not exactly risk-free, and one of the most frequently voiced impediments to cycling is fear of cars (and to look at all the dents on cars around Boston, and to extrapolate those dents to my body….)
But it turns out, on further study, that the bicycle is safer than any car, provided that you are still pedaling.