In the cult film The Matrix, unwitting humans’ body heat was siphoned off by machines to use as their energy source. Although that might not be the ideal situation to find ourselves in, the basis of the idea – using the warmth we generate to heat our buildings – could help fight climate change by cutting fossil fuel use.
Let’s look at the science. The average human body emits about 100 watts of heat at rest. When exercising, that heat can easily exceed 1,000 watts: energy that could boil one litre of water in six minutes. For comparison, a standard (3 kW) home kettle takes more than two minutes to heat a litre of water.
