Speed bumps to get new role as a source of green energy

Read the Article (The Guardian)

Stop the press. The world has gone mad!

This “scheme” sounds innovative on the surface – put some specially designed “speed bumps” (which can be flat or raised) in the road and they will harness kinetic energy from cars passing over them and turn it into electricity to power street lamps (etc) or feed surplus energy back into the National Grid.

However, when we look at the economics things start to make you scratch your head.

One of these new speed bumps costs anything from £20k to £55k depending on its size. The value of the energy it generates varies between £6k and £21k per year depending on traffic and size. So the ROI is approx 2-3 years before it has even paid for itself, let alone saved money or generated additional electricity.

A steady stream of traffic passing over the bump would generate 10-36 kW of power. This equates to a cost of approx £1.5k to £2k to produce wach kW of eletricity, and the article claims that 10 speed bumps would be equivalent to a wind turbine. However, the cost of a wind turbine is a little more vague as they are usually built in farms (ie lots of them), and the average cost to generate each kW of electricity from a wind farm is quoted at approx USD 1000 per kW (1998 figures – though this can vary).

It is clear to see that in high traffic areas (for example large supermarkets, shopping centres or distribution depots) these speed bumps could generate sufficient electricity to create a return and justify the cost of installing them. They could also make such developments more environmentally friendly as they are partly self-sufficient (although, as the article notes, it would take 4 speed ramps to power the street lamps, traffic lights and road signs in a single street – so not exactly a power plant and costing anything from £80k to £220k for that street). As part of a coordinated energy strategy they could balance environmental impact aganst energy production. However, it’s not clear from the surface of this news story how much of this impact has been investigated or understood.

So, are they economically viable? Or just another faddish idea? have you got any more in-depth information to back up the viabilty of these speed bumps?

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