or sometimes just a passing thought.

Leveraging the Cold

Date of original idea: been kicking around for quite awhile, this cold snap made me finally make the calcs

Can I utilize the cold cold outside to (significantly) reduce the energy my fridge uses?


I’m staying with round numbers to keep this a proof-of-concept calc, so don’t get hung up on my use of “approximate values”.

Results: About 1400kJ of reducing heating load per jug. The lion’s share of the heat absorption (about 96%) is due to the phase change from ice to water, which means this only has a chance if you can fully freeze and then fully melt, and the melting of a large block takes time. This puts an upper limit on the frequency that you can do this, I’m guessing that if you used a gallon jug that this limit is on the order of at least 1 day (from some empirical data I have with pop). Therefore, optimistically, this 1400kJ is the max per day for this shape jug. Maybe a flat, thin container could speed this up- we’ll hold that aside for future funding requests.

The electricity savings, and therefore money savings, would depend on the “efficiency” of the fridge (which would also include the number of times the door is opened and the temp of items put in and and and, which is why I put “efficiency” in quotes- it’s a mix of efficiency and consumption). The 1400kJ does work as a lower bound on the savings: 0.4kWh/day minimum.

My fridge is listed at “606 kWh per year” though that’s a marketing value. I would put a meter on the plug but the thing is big and difficult to pull out of the way to get to the plug. Using the marketing value 606/365 = 1.6 kWh/day of electricity. How much heat rejection that is I don’t really have a good handle on right now. What we can see is that, assuming this 1.6kWh per day is accurate, you can’t get much out of this even at 100% savings ($0.18 or so, which is $5/month and not nothing, but only when it is below freezing out).

Conclusion: The savings are small, likely less than $0.10/day of electricity, but a significant portion (> 25%) of the fridge consumption. Admittedly, however, a better test is needed to quantify the benefit: Energy meter for a some time of normal use followed up by an energy meter for a some time of normal use with frozen water jugs. I’ll get on that the next time it is both cold out and the fridge needs to move anyway.

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Puzzle Piece Table

Date of Original Idea: Like in April or something

A table with jigsaw-puzzle shaped pieces. When you want to expand it and add new leafs (leaves?) in, they are also puzzle pieces that fit i in between. I’m thinking 4 pieces with the legs attached, that can then expand into a longer, rectangular table. Maybe into a larger square table.

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Pi Table

Date of Original Idea: Mar 25 (came to me in a dream)

Self explanatory.  For pies.

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