The Joy of Discovering Saving More Energy (and using Q = m c ΔT)

March 4, 2024 by Joshua
in Stories

When getting electrical power requires climbing eleven flights of stairs, you learn to reduce consumption.

My pressure cooker usually uses the most energy. I have to gauge how much food to put in based on how much charge remains in the battery and how much sunlight I expect in the days to follow cooking. The forecast says three days of rain, so I won’t cook today, for example. When there are several days of sun in a row, I might cook without a second thought. Well, I still need to climb all those stairs, so I won’t cook blindly. I might check my work and exercise schedules.

My physics background tells me the amount of energy needed to heat the food is

Q = m c Δt

I suspect the amount of water I put in to dominate the energy needs, though vegetables are mostly water. I’ve learned to cook only what needs cooking, like beans, then add other things that don’t need as much cooking to warm from residual heat after the beans cook, like spinach.

It hit me that the metal pot in the pressure cooker added a lot of mass with a high specific heat.

Q = (m c Δt)food + (m c Δt)pot

For a while I figured I couldn’t do anything about it. Then I learned there are smaller pressure cookers. I have been using six quart ones. As my usual m.o., I went on Craigslist and to find used ones. I found someone selling a used three quart pressure cooker. I bought it Saturday for $30.

Do you think it would make much difference?


It did! I didn’t scientifically measure and compare, but based on my experience, eyeballing a load of stew, it took about two-thirds the energy in the smaller pressure cooker. That means I can cook more and climb less. I can stand longer periods without sunshine.

The container is smaller too, so I don’t have to heat as much water to turn to steam and fill up the pot to reach full pressure. More physics, regarding latent heat and a phase change, which still requires energy. Smaller works for me even more.

Fun, Freedom, and Abundance

There’s no other way to put it: this experiment was fun. I was confident I would get the results I did, but one never knows until testing. It’s fun to put into practice something I probably first learned in high school, meaning the 1980s.

I am living in more abundance than when I allowed myself to plug in at my whim and not think twice about how much energy and power I used. The less energy and power I use, the more I enjoy resilience and freedom.

People act like polluting less is some hardship. It’s fun. No matter how much I’ve reduced polluting, if I pollute more than zero, I can pollute less, meaning alleviating suffering.

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