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 around 100 watts heatat rest. This heat can easily exceed the temperature when you are exercising. 1,000 watts: Energy that can boil one litre water in six minutes. It takes less than two minutes for a standard (3kW) kettle to heat a litre water.
Where does the energy come? Mostly, food. The body’s Internal metabolismTo produce energy, the body uses products of digestion such as carbohydrates and fat acids. However, About 70-95%Heat is the main form of energy that is produced. This shows that the human body isn’t very efficient at generating mechanical energy from food: in fact, it’s slightly less efficient than a petrol engine.
Convection, infrared and other radiation can remove a lot of this heat from the body. You should sweatThis cools the skin by evaporation. This is why extremely Hot and humid conditions, you don’t feel comfortable – your sweat isn’t evaporating as easily into the saturated air.
Using infrared cameras, we’re able to see that heat as it moves from bodies to their surroundings. These cameras depict areas of increased heat (where more heat is being lost) as lighter in colour, and cooler areas as darker – showing us where most heat is being wasted.
This heat can build up when people gather indoors. Imagine a theatre seating 500 people. Assuming that each person produces 100 watts thermal energy, this would mean that 50 kW total heat will be emitted. This is equivalent of 25-30 AverageKitchen kettles boil water continuously
If those people are physically active – for example, dancing – together they could generate 150 kW of heat, or 3600 kWh over 24 hours. The average UK household consumes about 1,000 kWhEach month. An average domestic gas boiler produces approximately 30 kW, so 500 dancers could generate the same amount of energy as five gas boilers.
Next, we need to know how this heat can be best used to heat buildings. Air conditioning systems or ventilation are used to cool buildings and improve air quality. This heat is then lost into the environment, wasting energy. Crowd heat could be extracted instead via Heat exchangers for mechanical heating – devices that transfer heat from one area to another – and used to heat incoming air in neighbouring buildings.
You can also use this option to be more flexible Heat pumpsThese systems are similar to reverse air conditioning systems, where heat is pumped in instead of out. You can also store the heat in water cylinders, or modified bricks, for later use. This technology is already being used. data centresIt is here that the large amounts of heat released by computer networks must be extracted to prevent system failure.
Thermal energy in action
In some parts of the world, body heating systems are already a reality. In Sweden, the Kungsbrohuset office building – located above Stockholm’s central subway station – is already Heating partiallyThe station’s heating needs are reduced by the body heat of daily travelers who pass through it. This reduces heating costs by between 5-10%. A heat pump extracts heat from the station, where it’s stored in water that’s used for heating the offices above.
In Minnesota, Mall of America has been generating energy from the sun and the heat of more than 40 million visitors annually. Replacingcentral heating. The thermostat. BODYHEAT system, currently undergoing installation at an arts centre in Glasgow, uses heat pumps to capture clubbers’ thermal energy and store it in Underground boreholesIt will heat the building with hot water.
I’ve studied the heating system at Nottingham PlayhouseWith a capacity for 750 people, the auditorium is available at. The theatre’s capacity is 750 people. We discovered that the temperature rises with increasing audience numbers. This means that the central heating can also be reduced on nights when there are packed houses. Using this principle, we can develop “smart buildings” able to adjust their heating based on the number of people in a room and the expected resulting increase in temperature. This simple solution can be used in many types of buildings – even those without heat pumps installed.
With the Recent hikeIn energy prices and the global push toward reaching net zeroThese systems could reduce carbon emissions and make it easier to save fossil fuels and lower your energy bills. They also make use of heat that is already being used in busy public spaces.