Link: www.withouthotair.com Please see link above for the book, “ SUSTAINABLE ENERGY – WITHOUT THE HOT AIR” by David E. Mackay. This electronic version is for personal use.
Saving the planet by numbers David MacKay Professor of Physics, University of Cambridge When it comes to saving the planet, "every little helps!" Or does it? Maybe if we all do a little, we'll achieve only a little. Newspapers and television programmes are full of suggestions on how we can be more green. But how can we tell what works? As I argue in this week's More or Less on BBC Radio 4, what we need is a single unit of measurement. I would like to suggest measuring energies in kilowatthours, and measuring how fast activities use or produce energy in kilowatt-hours per day. One kilowatt-hour (1 kWh) is the electrical energy used by leaving a 40 watt bulb on for 24 hours (and it might cost you 10 or 15 pence (15 or 20 US cent)). Can we cut fossil fuel consumption enough to save the The chemical energy in the food we eat to stay alive planet? amounts to about 3 kWh per day. Taking one hot bath uses about 5 kWh of heat. Driving an average car 50 kilometres uses 40 kWh of fuel. In total, the British lifestyle (and I apologise to international readers but my study is based on British numbers) uses 125 kWh per day per person for transport, heating, manufacturing, and electricity. So, how do green lifestyle ideas fare under the quantitative spotlight? Well, some of these sacred cows do not fare too well, and some come through with flying colours. Here are four important examples. 1