It’s been cold here for the last few days, near freezing, then cool and rainy, so while I do have the power system running, finally, I have not been motivated to get out there and do the water test and finish the tub installation. It’s supposed to warm up a bit later this week and stay temperate for several days. I hope to get some work done this weekend, at least, and with luck, get the water test done, respond to whatever needs responding to about that, if anything, and ideally get the tub install done, too, at long last. We shall see.
In the meanwhile, I offer you this bit of geekery. I was musing recently that maybe I should just ditch the 320 pounds of LFP batteries, the 120 pounds of power center, and just use a little uranium to power the HomeBox. In the moment I just wild-guessed it at 50g. Then, of course, I had to look up the energy yield of uranium and do some math to see how close I was. I did say geekery, did I not? I did.
The batteries are rated for 10,000 charge/discharge cycles. Now while I don’t actually expect to full-cycle all four batteries every day, 10k days makes a decent life estimate anyway. Rounding down, that’s 27 years. So how much energy do I need over 27 years and what’s that in uranium, anyway?
My daily energy budget is 4kWh. 1W is 1J/s, so converting 4kWh to Joules goes like this:
[ 4000 (J / s) h ] * (60 s / m) * (60 m / h) -> 14.4 MJ each day.
A year being 365.25 days, 27 of them is 9861.75 days.
9861.75 days * 14.4MJ/day -> 142GJ.
The Internet says uranium has an energy yield density of 83,140,000 MJ/kg.
Since I’m already in GJ, let’s recast that as 83,140GJ/kg.
My total energy usage of 142GJ / (83,140GJ/kg) ->0.001708 kg -> 1.708g. I was off by a factor of almost 30. Still, if I was doing astronomy, that would count as pretty close! And anyway, I don’t actually know a thing about the practical matters of getting energy out of uranium, so maybe a tiny-house-sized nuclear power plant is only 3.4% efficient, so that 1.708 really needs to be 50g after all 🙂