Tag Archives: energy

The problem with the bulb ban

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You might not have noticed, but the sale of standard filament lightbulbs has been banned since last September.*

Current proposals are to replace standard incandescent bulbs with more efficient compact fluorescent bulbs. Fluorescent lights work by passing a current through a tube containing mercury vapour. The excited mercury atoms emit ultraviolet photons which then collide with the phosphor coating on the inside of the tube, causing it to emit light (to “fluoresce”) in the visible part of the spectrum.

The problem with this is that some of the ultraviolet light is still emitted (in fact germicidal lamps are basically fluorescent bulbs without the phosphor coating). Many people are sensitive to ultraviolet light and cannot enter rooms lit by flourescent lamps.

People with conditions such as photodermatosis (where exposure to ultraviolet causes swelling, rashes and blistering) and people with photosensitive epilepsy (the 50Hz mains supply flicker is visible from fluroescent bulbs but not from incandescent ones) have been stockpiling bulbs since the ban was announced.

I’m not against the sale of compact fluorescent lightbulbs; in fact I’d like to see them more widely used (especially in place of the inefficient halogen spotlights that seem so popular). What I’m against is removing the consumer’s right to choose.

(If you’re desperate for lightbulbs and you’re wondering, I took the photo above outside of Rugby Electrical, in Rugby.)

* Technically, it’s only the sale of bulbs for household use that’s banned. “Industrial use” is still okay.

Kinetic hydropower

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Wind is moving around the world all the time, and we use that for generating electricity. But water is moving around the world all the time too – can’t we use that to generate electricity?

A wind turbine is a device that converts kinetic energy (of the wind) into electrical energy. If you solve all the right equations you find out that the power (P) of a wind turbine is the product of the density of the air travelling through it (ρ), the cross-sectional area of the blades (A) and the speed of the wind cubed (v). (This means that if you double the speed of the wind, the power produced goes up by a factor of eight; if you triple it the power goes up by a factor of 27.)

This equation applies to any situation in which we’re using a fan-type arrangement to “catch” a moving fluid and extract useful electrical energy from its kinetic energy, so it applies just as well to moving water as it does to moving air.

Kinetic hydropower is the fancy name for putting a wind turbine underwater. Although the water in a river or sea moves much slower than the wind, the fact that it is much denser (about a thousand times denser) means that it can still generate reasonable amounts of electrical power. The low rotational speed also helps to protect marine life, which isn’t the case for wind turbines and birds.

Kinetic hydropower systems are expensive and difficult to install, and have to very sturdy to withstand the larger forces that moving water imparts; but if the engineering challenges can be overcome they have significant advantages over wind turbines, particularly in respect of their intermittency – a river’s flow is far more reliable than wind’s.