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On this: > "There's probably about 3 million households in Rwanda, and a vanishingly small number have a fridge. A refrigerator uses about 2 kilowatt-hours (kW
by photochemsyn 4y ago
On this:
> "There's probably about 3 million households in Rwanda, and a vanishingly small number have a fridge. A refrigerator uses about 2 kilowatt-hours (kWh) of energy per day, so if we were able to get one into every household, that would add about 2 billion kWh (2 terawatt-hours, or tWh) to Rwanda's annual energy usage. That's about as much energy as there is contained in 1 million barrels of oil — and fully one-third of Rwanda's current primary energy consumption."
1) Energy-efficient refrigerators are available at ~1.1 kwH/day. This reduces the needed energy estimate by about half.
2) Energy capture for refrigeration from solar in Rwanda makes much more sense than oil production does. Under full sunlight, a decent 2.5 kW solar array produces about 10 kWH per day (as the full 2.5 KW is only produced at noon, tailing off towards morning and evening). As you probably want to run the refrigerator at night, a battery capable of storing about half that output (5 kWH) would also be needed.
The notion that you'd want to set up an oil-burning power plant (which only converts energy stored in oil to electricity at ~25% efficiency or so) in Rwanda is pretty silly.
As far as claims that there isn't enough land to set up solar panels to provide this minimal home energy supply, the roofs of most dwellings would provide adequate area. It's also possible to grow a wide variety of crops in conjunction with wind turbines and solar panels on agricultural land (wide spacing is all).
- affgrff2 4y agoI don't think the author suggests to set up an oil-burning power plant, that number is just for visualization. And I guess you could even go without a battery at night by converting the energy from the daylight directly into cold.
- ebiester 4y agoI think the point is explained further below - the author is making a reference to the amount of energy required if the world had a developed standard of living, not saying that we would ever use natural gas down there. > It can be done. In the near term, it is conceivable that already-common sources of renewable energy like wind and solar power can meet most of the need. Things would be easier if existing nuclear power technologies were expanded, or at least if we avoided shutting such plants down prematurely. > But the more fanciful world described above—the one in which, thanks to plentiful energy, the world has eliminated want—is possible only with continued innovation. In the long term, the renewables we currently have will hit a ceiling.
- nordsieck 4y ago> Energy-efficient refrigerators are available at ~1.1 kwH/day. This reduces the needed energy estimate by about half. There's a number of people experimenting with converting chest freezers to chest fridges using an external thermostat. Apparently, these can be extremely efficient - people are reporting 10-20% of your 1.1kwH/day number. Of course, the typical downsides of a chest freezer apply to a chest fridge - they're typically much more limited in size compared to their upright counterparts due to ergonomics, and the larger they are, the more difficult they are to fully utilize. But they're a lot better than no fridge at all.
- jules 4y agoWhat explains the big difference?
- jusssi 4y agoCold air likes to go down. When you open a fridge door, the cold air pours out at the bottom. When you open a chest, it stays in the chest. Also, a freezer probably has better insulation than a fridge to begin with, since it's designed to hold bigger temperature differential.
- pbhjpbhj 4y agoFridges should probably be designed with multiple sections rather than open shelves?
- deleted 4y ago[deleted]
- misto 4y agoHad to check, our fridge model advertises about 0.8kwh/day. I guess while operating it with the ECO -mode.
- lostapathy 4y agoThose numbers assume a climate controlled environment, though. If you live somewhere hot without air conditioning, the fridge has to work a lot harder. That’s why the typical middle America “garage fridge” is such an energy hog.
- izend 4y agoFor a 2.5 kW solar system would cost somewhere around $2-5K USD and the 5kWH battery would also cost $2-5K USD. I don’t think the average Rwanda citizen has $5-10K available to install just enough power to run their fridge.
- photochemsyn 4y agoWell that system would produce maybe 9X what the fridge needs so you'd have a lot of extra power for other uses, like AC, lights, cooking, online gaming...
- Panzer04 4y agoIt would certainly be on the low end I would expect, and only getting cheaper. It's unfortunate that Rwanda is so poor that even that is far too much :(
- WalterBright 4y ago> As you probably want to run the refrigerator at night My experience with power failures is that the refrigerator will keep the food cold enough overnight if you don't open the door. Even so, the refrigerator could make ice during the day and be an ice chest at night. No need at all for a battery.
- dredmorbius 4y agoThis. There are numerous heating/cooling applications in which excess capacity at peak capabilities is banked for later use. Thermal energy storage for thermal energy applications is exceedingly efficient as there are no further conversion losses. Solar power refrigeration which chills an ice block to an arbitrarily low temperature then relies on that to maintain the chilled-compartment temperature during periods of low or no power would be the obvious option.