Professor Science: could a giant space fridge stop global warming?

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Here at my lab, I receive emails from all manner of laymen, questions about science due to my status as the agony aunt of the entire scientific community. One of the most common subjects is that related to kitchen appliances which people use every day but do not understand. As such I have decided to address the matter of confused refrigerator users.

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Professor Science reading your emails

Fridges make things colder by literally “chilling” the inhabitants of the refrigerator. They whisper dark things to the food about what will happen to them once the perceived saviours (i.e. us) open the door to remove them. Now to do this they use demonic powers (channelled by physicists upon our sterilised, whitewashed alters of “science”), which is why if you reach round the back the fridge seems warm. Now we come to the tricky bit.

Due to a combination of the laws of thermodynamics and entropy, the warmth out the back is going to be greater than the cold within the fridge. This is simply due to efficiencies – the process of cooling the inside of the fridge can only be conceivably 100 per cent which would be a net zero temperature change if you left the door open for a long time. However, this is not possible at all – the highest efficiency of a heat pump (read refrigerator) is the Carnot efficiency – a lovely little formula for the highest possible (yet still practically unachievable) efficiency of our heat pump.

So therefore if you leave the fridge door open the little motor inside it essentially just turns into an energy wasting heater!
Ah, you interrupt, so then surely we could counter global warming by pointing a whole load of fridges away from something that needs warming and then just cool the outside? Let us see!

Since 1880 the globe has warmed 1.4 degrees Celsius according to National Geographic.

So let us build a fridge that will point the cold side inwards and the warm side outwards – let’s say a fridge satellite (I’ve heard that space is fairly cold). And of course let us ignore all the things like the shape of the world etc. that cause this to be an “estimate” (science term).

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Artists impression of the space fridge

There is around 5000 trillion tonnes of air in the world that needs to be cooled down by 1.4 degrees in this very simple idea. Using very bad science and a slew of estimates, let us say that 1 joule of energy is needed to reduce the temperature of 1 gram of air by 1 degree. As such we need to remove 7,000,000,000,000,000,000,000 Joules of Heat energy from the atmosphere. I cannot find a definitive average temperature for the world so let us pick a day when the average temperature is a comfortable room temperature of 22 degrees Celsius. And let us put the hot bit of Jake the satellite fridge in the very coldest part of all space making it 2.7 Kelvin.

This is such an extremely large temperature difference that it is not *too* silly to give our fridge an efficiency of 1. As such it would need to be supplied with all those zeroes of energy quoted above in order to move the heat from our atmospheric reservoir to space.

If we connected it to the largest nuclear power station we have ever made which has an output of 8212 kiloWatts giving 700,000,000,000,000 Joules per day. The keen eyed among you will notice that this will take 27 thousand years to reverse global warming. This might not work. Let us say that we need a reasonable time scale in which to stop Al Gore’s rampaging do-gooder hard-on. Thirteen years sounds reasonable. Every power plant on the planet outputs 150 pWh a year which would mean that in 13 years the combined output of every single power plant on the planet could, in theory (let’s assume perfect conducting wires etc. obviously!), reverse global warming. Add a year due to the global warming we produce running all our power plants and here you have our viable global warming ending fridge!

Do you have a question for Professor Science? Contact impact-features@bath.ac.uk

Cartoon credits to Darius Gilani

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