Sander's Reflexions

Several years the environment was not an issue. Suddenly, this year it returned to the headlines, mainly due to the movie ‘An Inconvenient Truth’. So I thought, let me contribute a tiny bit to the discussion. I wrote a letter to the Dutch newspaper Trouw and yes, it got published. What’s the point? A 5 km large open air ice skating rink, Flevonice, has been opened. It uses coolers with a total capacity of 9.6 megawatt, which is equivalent to the reduction that can be obtained by replacing 1 million ordinary light bulbs by compact fluorescent lamps (CFL).



OK, the calculation in my letter is a bit biased. Of course the coolers are also not working at full capacity. They needed this capacity for initial ice creation at 10 °C. After startup the machines are probably running at 10 to 20 % of their capacity. But I had to make a statement. I could also have stated that it is equivalent to the capacity of 200 cars (50 kW), but that wouldn’t make a statement. Or, I could have said it is equivalent to 5 wind turbines (2 MW), but that would not impress at all, since there are about 500 wind mills in that province.

Let’s fiddle a bit more with those figures. The cars use maybe only 10 to 20% of their capacity when they are cruising. But also the average power of a wind turbine is 10% of its capacity. And light at home is also switched on for about 10% of the time. So let’s compare these capacities. One running car is thus equivalent with the saving 1000 CFL’s. And 40 cars are equivalent one wind turbine. Why is everybody talking about wind turbines and CFL’s? There are millions of cars out there and a saving of a few percent on the energy consumed by cars will have more effect than can be obtained with CFL and wind turbines.

Want some more interesting figures? An average boiler used for the heating of a house has a capacity of 25 kW, a small car. And, shame on me, I have still 6m2 of single glazing in my living. These are hung sash windows. Isolated glazing with two layers of glass does not fit in the frame. The heat transfer of non-isolated glazing is approximately 6W/m2K. When it’s near 0 °C outside this results in a heat transfer of 6 * 6 * 20 = 720 W. A figure that outnumbers any savings that can be made by CFL’s. Luckily I’ve recently found some thin isolated glazing, Van Ruysdael glass. I know what I’m going to do in 2008!