President
rpr consulting

I’m the project manager for developing guidelines on modern streetcars—through APTA’s standards program.One of the guidelines’ chapters deals with power supply. If you put enough energy storage in a streetcar, you can operate it without overhead wires, and that’s where it gets interesting.

Why eliminate overhead wires? A key issue is aesthetics. You might be running a tramway against a 16th-century cathedral. Or you might have an impaired clearance, and thus no room. In Seattle they are building a streetcar line that does not put overhead wires up to avoid a trolleybus overhead.

It could be cheaper—but before you jump to that conclusion, you need to look at the pros and cons. How far you can go on the energy storage alone is dependent on all kinds of things, like going up a hill.

In the guideline, we’re encouraging people to look at the lifecycle cost, not just the capital ones.

The technology is sized for a particular application, because you don’t want to carry around extra capacity, which means you’re carrying extra weight. With batteries, however, you need external power to recharge it—and how long will that take? If it’s a two-mile line, if the charging time is longer than the headway, that would impact the cost.

So why is this of value?

First of all, energy storage is something that can pay off literally in cost savings and can bring other operational benefits as well. So cost savings is the primary driver.

In some cases, there are definitely reasons why it would be really handy to eliminate overhead wire. Whether, over the lifecycle cost of the project, that investment translates into cost savings is still open for discussion.