Energy, Heat and Global Warming

By Daniel Brouse and Sidd Mukherjee for Sidd’s Science Center

I ask:
Is there anything humans do with energy that results in less heat?

For example, furnaces generate heat, refrigerators generate heat, light bulbs generate heat, computers, cars, fans and even air conditioners create more heat.

Is there anything that we do that has a net loss of thermal energy or does the use of energy (period. both fossil fuel and renewable energy) by humans add to global warming?

Sidd replies:
Not just humans. Anytime energy is converted from one form to another and work is extracted by any agency, not just humans, some is lost as heat energy. That’s the second law of thermodynamics.

But to put it in perspective, lets say you burn a pound of coal, and take all the chemical energy out as heat. The amount of heat you directly obtain is several hundred times smaller than the heat trapped by the carbon dioxide generated over the next many thousand years that it remains in the atmosphere… so, don’t burn coal, oil or any fossil carbon.

Thus, for example conversion of AC to DC electricity can be very close to 100% efficient… but if you take out some of the energy and do work with it, you will lose some energy as heat.

The second law of thermodynamics states that the total entropy of an isolated system always increases over time, or remains constant in ideal cases where the system is in a steady state or undergoing a reversible process. The increase in entropy accounts for the irreversibility of natural processes, and the asymmetry between future and past.

The second law has been expressed in many ways. Its first formulation is credited to the French scientist Sadi Carnot in 1824, who showed that there is an upper limit to the efficiency of conversion of heat to work in a heat engine.

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