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Solarpunk is happening in Africa
601–610 of 616 posts
Re: Solarpunk is happening in Africa
#602Earlier quoted context omitted.
This has almost nothing to do with how electricity is priced.
Electricity isn't priced only one way. In the Japanese market in summer during the day the spot price nose dives to almost nothing because of an oversupply of solar. Yet most installed solar is operating under the FIT system where all generation is guaranteed to be bought by the regional generation company for a fixed price, regardless of what the spot price is. This worked to incentivise bringing lots of solar onlin…
all true, but in the vast majority of electricity markets, inertia is not priced.
what does drive the price of electricity is fuel cost, not grid stability.
Solar inverters do not have physical inertia but they can have fast frequency response via capacitors. Many wind turbines have this feature and at scale, it is a decent replacement for electromagnetic inertia.
Re: Solarpunk is happening in Africa
#603I worked in this industry as a software developer. Companies like SunCulture (who used to be a customer of ours) started maintaining all their customers on spreadsheets. But with high volume low-value sales, you need to have good software to manage this. We were a player. I once had to do a mobile money integration with a Zimbabwean bank. A dozen skype calls led to nothing. Then I visited the country, bought a local…
> So you are looking at powering DC only appliances! Is there anything you actually need AC for? The big advantage of AC is that you can easily transform it for long range transmission. If you don't need that, AC is not really necessary, is it? I guess the bigger issue is the limited power -- you probably can't use a small scale solar installation for cooking or washing, not because it's DC, but because it just wont…
Thermal energy storage solves the problem of cooking and washing.
I have a half-liter thermos bottle that leaks about 0.3 watts at ΔT ≈ 50° (635g of water dropped from 71.9° to 69.8° over five hours and 8 minutes), so any power supply averaging over about a watt would be sufficient to boil water in it—eventually. If you needed to do it in the 4 hours the sun was near peak on a single day, you'd need at least 15 watts. (I don't live in Africa, but I do live in a third-world country. Blown-glass thermoses are pretty widely available because, although they're fragile, they're light and never wear out, just shatter.)
Sand batteries are potentially extremely cheap and can easily deliver cooking temperatures. A super-low-tech version of this approach is "salt frying", where you preheat a few kg of table salt (melting point 800.7°) to frying temperature, then stir dry food into it. Most of the salt won't stick to the food, but the few grains that do won't cause the edibility problems that sand would.
TCES potentially offers much greater storage density and much greater controllability than these sensible-heat energy-storage technologies, since you can store the "heat" indefinitely.
Phase-change thermal energy storage is another potentially appealing possibility, potentially offering a stable cooking temperature for many hours, although I don't know of any suitable materials. The MgCl₂-KCl–NaCl eutectic, for example, doesn't melt until 401°. Maybe something like calcium stearate (m.p. 150°–180°) would work, but its heat of fusion isn't great, I'd be worried about long-term stability, and although it's easy to get anywhere in the world, it's probably a lot more expensive than salt. (Table salt is US$100/tonne, but the eutectic mentioned above would be closer to US$400/tonne.)
Re: Solarpunk is happening in Africa
#604Earlier quoted context omitted.
For what it’s worth, cooking a large meal for three (big pot of pasta or rice, brown onions and garlic, brown mince meat, vegetables, simmer sauce) on my induction in my round the world vehicle uses smack on 40Ah of a 12v lithium battery - so about 0.5kwh. It’s connected with a 3000W inverter. 600W of solar helps a lot.
> so about 0.5kwh It takes 1.16 Watt-hours to raise a litre of water by a degree. Say 85Wh for 15C room temp to 100C boiling. Assuming your large meal for three is 3 litres, that's 255Wh to get the water boiling. There's energy loss from battery through inverter, through induction. Loss in the pot losing heat to the air. This doesn't count keeping it simmering, or heating the other ingredients. I don't have any idea…
> 'pot cosy' to insulate the pot and stop radiated heat loss
Is this a product that exists?
The closest I could find was ceramic fiber insulation [0], which could presumably be cut to shape and fastened (high temp fastener?) into pot shape.
Re: Solarpunk is happening in Africa
#605Earlier quoted context omitted.
Not really, my old microwave has 500 Watts, this should be also enough for slow resistive cooking while being insulated.You will find 12V/24V 2.8L/5L Dc Electric Pressures Cookers with 250W-300W on AliExpress. (1l needs roughly 0.1kwh of energy to go from 20 to 100°C) Additionally, you might save a lot of energy by using a hay box after it starts to boil. https://en.wikipedia.org/wiki/Haybox
slow cooking: see above on changing the taste of food that's deeply rooted in tradition
So? Everyone used to cook over woodfire. If the benefits are good enough, like massiv time saving, it will change.
Re: Solarpunk is happening in Africa
#606Earlier quoted context omitted.
Not really, my old microwave has 500 Watts, this should be also enough for slow resistive cooking while being insulated.You will find 12V/24V 2.8L/5L Dc Electric Pressures Cookers with 250W-300W on AliExpress. (1l needs roughly 0.1kwh of energy to go from 20 to 100°C) Additionally, you might save a lot of energy by using a hay box after it starts to boil. https://en.wikipedia.org/wiki/Haybox
IMO 500 watts of sustained electrical power is a fair bit, especially compared to every other electric device these households are likely to have.
500wh battery can deliver that for 1 hour.
Re: Solarpunk is happening in Africa
#607I think this is really cool, but math seems off: > A company (Sun King, SunCulture) installs a solar system in your home > * You pay ~$100 down > * Then $40-65/month over 24-30 months But also: > The magic is this: You’re not buying a $1,200 solar system. You’re replacing $3-5/week kerosene spending with a $0.21/day solar subscription (so with $1.5 per week half the price of kerosene) $1.5 week is $6 a month, not $60…
this, they also say 45-60/month which is NOT 0.21/day
These 0.21/day are MPESA transaction fees. I stumbled upon that, too.
Re: Solarpunk is happening in Africa
#608Earlier quoted context omitted.
For what it’s worth, cooking a large meal for three (big pot of pasta or rice, brown onions and garlic, brown mince meat, vegetables, simmer sauce) on my induction in my round the world vehicle uses smack on 40Ah of a 12v lithium battery - so about 0.5kwh. It’s connected with a 3000W inverter. 600W of solar helps a lot.
> so about 0.5kwh It takes 1.16 Watt-hours to raise a litre of water by a degree. Say 85Wh for 15C room temp to 100C boiling. Assuming your large meal for three is 3 litres, that's 255Wh to get the water boiling. There's energy loss from battery through inverter, through induction. Loss in the pot losing heat to the air. This doesn't count keeping it simmering, or heating the other ingredients. I don't have any idea…
No, I never tried.
I have a 200Ah lithium battery, 600W of solar and a dc-dc charger.
To be honest, using up 20% of my battery to cook a large dinner is not a big deal or something I need to improve.
Re: Solarpunk is happening in Africa
#609Earlier quoted context omitted.
Afaik markets predate joint-stock companies. The concept of "raising capital" is much newer than the concept of a market economy. Did capitalism exist under feudalism? How do modern capital markets differ from historical markets under various other economic systems?
> Did capitalism exist under feudalism? I would say it's more of a matter of the level of interference of the fief on trade. When 100% of the economy is controlled by the monopoly on violence I would say that is complete communism, and when 0% of the economy is controlled by the monopoly on violence that is complete capitalism. This is a kind of asymmetric definition of communism/capitalism because "complete capitali…
You're describing planned and unplanned economies, which aligns somewhat with capitalism and state communism but is not the defining feature of them.
The main difference is ownership of the means of production/companies by the workers or by a separate group that might not work at the company at all.
Re: Solarpunk is happening in Africa
#610Earlier quoted context omitted.
> I guess the bigger issue is the limited power -- you probably can't use a small scale solar installation for cooking or washing, not because it's DC, but because it just wont offer 1000W power. Your average lead-acid starter battery can easily do that - 1 kW is less than 100 amps at 12V, less than 50A if you wire two in series. 200 Ah means about four hours worth of runtime. The problem is switching off higher DC v…
Could it easily do that for several minutes at full chap? Under the load of a full washing machine?
No, only for about a minute or two. But there are a lot of lithium-ion batteries capable of 10C discharge rates which can survive several minutes of max load. For 100 amps I am guessing you'd need 10 amp-hours of 10C-capable lithium-ion batteries, roughly a 4S4P or 4P4S configuration of 10C 18650s. I think this is about US$128 of batteries, a similar price to the car battery but much smaller and more inflammable.