Africa’s Cold Rush and the Promise of Refrigeration
August 25, 2022 9:07 AM Subscribe
Cold chains for Covid vaccines (which need to be super cold) were a big issue not too long ago. But grocery stores are everyday wizards at it.
posted by Bee'sWing at 10:10 AM on August 25, 2022 [3 favorites]
posted by Bee'sWing at 10:10 AM on August 25, 2022 [3 favorites]
I've been reading up on crop coolers, harvest coolers, because a PV one on a farm organization near me turned out to be under-powered. Most of the off-grid research is done in hot poor places because the normal US approach is to fling grid power at it (even that can go wrong!)
1. Nutrient loss in un-chilled food is very high even if you don't get actual spoilage. Somewhere I saw a nonprofit working out the maximal nutrition*calorie payoff for their investment dollars, specifically "How many coolers per well?".
2. It needs so much chilling. Not only is there a lot of "field heat" in the food as you pick it, which you want to get rid of fast, but vegetables have "heat of respiration" -- they're producing heat in the cooler by the same metabolic processes that eventually reduce tastiness and nutrition. The lower the chilling temperature, the slower the metabolism, the less heat of respiration, so there may be a payoff to investing in the coolest temperature you can get to. But the greater the difference between the cool temperature and ambient, the more energy demand per degree of cooling.
3. Cooling is straight up resource consuming. In hot dry places there are low-power tricks if you have plentiful clean water. In hot humid places there are no easy tricks. And
4. The veg need high humidity at low temperatures. Moisture management trips up a lot of seemingly obvious low-energy climate control approaches -- I've spent time with too much damp in hopeful heating situations, am amused to be looking at inadequate humidity in hopeful cooling situations.
posted by clew at 10:48 AM on August 25, 2022 [22 favorites]
1. Nutrient loss in un-chilled food is very high even if you don't get actual spoilage. Somewhere I saw a nonprofit working out the maximal nutrition*calorie payoff for their investment dollars, specifically "How many coolers per well?".
2. It needs so much chilling. Not only is there a lot of "field heat" in the food as you pick it, which you want to get rid of fast, but vegetables have "heat of respiration" -- they're producing heat in the cooler by the same metabolic processes that eventually reduce tastiness and nutrition. The lower the chilling temperature, the slower the metabolism, the less heat of respiration, so there may be a payoff to investing in the coolest temperature you can get to. But the greater the difference between the cool temperature and ambient, the more energy demand per degree of cooling.
3. Cooling is straight up resource consuming. In hot dry places there are low-power tricks if you have plentiful clean water. In hot humid places there are no easy tricks. And
4. The veg need high humidity at low temperatures. Moisture management trips up a lot of seemingly obvious low-energy climate control approaches -- I've spent time with too much damp in hopeful heating situations, am amused to be looking at inadequate humidity in hopeful cooling situations.
posted by clew at 10:48 AM on August 25, 2022 [22 favorites]
I wish them luck! Thanks for the link very interesting Ertigan.
posted by Meatbomb at 10:55 AM on August 25, 2022
posted by Meatbomb at 10:55 AM on August 25, 2022
Cooling is straight up resource consuming.
Fortunately it's also a pretty good match for cheap, intermittent, off-grid, distributed renewable energy sources like solar PV, because storing coolness for weeks at a stretch is very easy, certainly much cheaper than storing bulk electricity. All you need is a large thermal mass such as a big water tank or even a silo of gravel or coarse sand, with a decent amount of thermal insulation around it and some kind of heat exchanger embedded in it, and a small amount of battery storage to keep the control systems for the heat transfer fluid loops alive.
posted by flabdablet at 12:35 PM on August 25, 2022 [4 favorites]
Fortunately it's also a pretty good match for cheap, intermittent, off-grid, distributed renewable energy sources like solar PV, because storing coolness for weeks at a stretch is very easy, certainly much cheaper than storing bulk electricity. All you need is a large thermal mass such as a big water tank or even a silo of gravel or coarse sand, with a decent amount of thermal insulation around it and some kind of heat exchanger embedded in it, and a small amount of battery storage to keep the control systems for the heat transfer fluid loops alive.
posted by flabdablet at 12:35 PM on August 25, 2022 [4 favorites]
Yeah, in theory. I should start taking pictures of grant-funded and capstone projects moldering unused because something failed in practice.
I mean, after the pictures, measurements; and theoretically interviews with the people who gave up on it to figure out why; and review with the builders/grantors to get them to do follow ups. Or - better - never pay for one of these projects without at least a year of operations maintenance and reporting.
posted by clew at 1:13 PM on August 25, 2022 [3 favorites]
I mean, after the pictures, measurements; and theoretically interviews with the people who gave up on it to figure out why; and review with the builders/grantors to get them to do follow ups. Or - better - never pay for one of these projects without at least a year of operations maintenance and reporting.
posted by clew at 1:13 PM on August 25, 2022 [3 favorites]
Everyone deserves tasty, nutritious food.
And, yeah, non-fossil energy sources are a must to the extent possible.
posted by neuron at 4:00 PM on August 25, 2022
And, yeah, non-fossil energy sources are a must to the extent possible.
posted by neuron at 4:00 PM on August 25, 2022
confusion. I have been taught, and seen, tomatoes loose flavor from refrigeration.
posted by Goofyy at 5:27 PM on August 25, 2022
posted by Goofyy at 5:27 PM on August 25, 2022
They may still stay edible and Vitamin-C providing longer if cooled.
posted by clew at 6:30 PM on August 25, 2022 [2 favorites]
posted by clew at 6:30 PM on August 25, 2022 [2 favorites]
Tomatoes turn mealy and tasteless when refrigerated for any length of time. But they don't last particularly long sitting around at room temp either. You can change that a bit by sealing the stem scar with something - tape, wax, gum, etc.
posted by 1adam12 at 6:00 AM on August 26, 2022
posted by 1adam12 at 6:00 AM on August 26, 2022
Tomatoes do ok refrigerated above 10C which is quite a lot warmer than a typical refrigerator.
posted by atrazine at 7:21 AM on August 26, 2022
posted by atrazine at 7:21 AM on August 26, 2022
Sounds like that's another wrinkle in the cold chain problem for developing countries, some foods need to be cooled as low as possible as fast as possible (beans), some should be flash frozen (fish), while others might benefit from being cooled to a midpoint for faster consumption (tomatoes). But if you've only got one storehouse/one truck, then someone's got to make the decision on which of those methods is the priority.
posted by sharp pointy objects at 1:09 PM on August 26, 2022
posted by sharp pointy objects at 1:09 PM on August 26, 2022
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posted by jacquilynne at 9:37 AM on August 25, 2022