Carbon-Neutral Christmas 2008

We celebrate Christmas in Scotland in many ways. One of them consists of hanging many thousands of 25 or 40 Watt coloured light bulbs in public areas and leaving them burning for up to 40 days, thus consuming a huge amount of extra electrical energy over and above the amount we use for street lighting. Just two Christmas trees, one in Dumfries and one in New Galloway, have consumed 10 Megawatt-hours this Christmas - and there are dozens of other examples in Dumfries and Galloway. There is clearly an issue for Dumfries and Galloway Council to address here, and we're talking to them about it.

It doesn't have to be that way. LED lighting, ideal for decorative festive lights, consumes about 25 times less power and can be driven by micro-renewable generators, off-grid, such as photovoltaic cells, pico-wind turbines, small diesel generators fuelled by recovered vegetable oil, or even school pupils! So that's what we did, using garden-shed technology as always.

We built some generators from old exercise bikes salvaged from various places (one came out of the River Nith in Dumfries, rescued from its watery grave by a Local Authority Councillor). We used them to drive electric motors salvaged from pavement scooters (remember those?), either 24 Volt or 36 Volt. Working in reverse, these motors easily generated enough DC Voltage to charge a car battery when pedalled by a primary pupil (actually, relays of primary pupils doing 5 minutes each - exercise in the curriculum). The motor was connected to the battery through a blocking diode rescued from a computer power supply, so that the battery wouldn't drive the motor instead of the motor charging the battery. The batteries, needless to say, were scrounged from the reject battery pile of a friendly local garage and tested to make sure they had enough life left in them for our purposes.

We cheated a bit on the lights themselves. We bought mains LED light sets (nominally 24 Volts, they work fine when connected to 2 car batteries in series) as cheaply as we could find them and connected them to the 12 Volt batteries through cheap 75 Watt power inverters. This gave us a backup strategy in case anything went wrong - the lights could always be plugged into the mains, thus avoiding pupil disappointment resulting from end-of-term party fatigue! Even if run off the mains, these lights still consume only a tiny fraction of the energy used by the hot-wire bulb sets they replaced, so the schools were still on the side of the angels by an energy-reduction factor of at least 25 times. We have been working on making up sets of LED fairy lights using red, green and yellow LEDS from scrapped computers and so on, but that takes more time than we had to spare this year. We took a prototype of the lighting sets to the SNP Conference in Perth in October, where we were very kindly given some space on the stand being run by the The Royal Highland and Agricultural Society of Scotland, managers of the famous Ingliston Showground in Edinburgh, and it attracted a fair degree of attention there. Our grateful thanks to RHASS for their hospitality.

Here's a picture of one of the battery and inverter sets:

We managed to put three complete sets of generators, batteries and lights together and install them in Kirkcolm Primary School (link points to BBC Scotland TV article), Kirkcowan Primary School and Dalry Primary School during the first week of December. Initial pupil feedback was very positive, even ecstatic (cycling's more fun than sums) but we'll get more detailed results in the New Year. We also put a set of mains-powered LED lights in Glentrool Primary, a very small school, with too few pupils to pedal the generator set.