Efficient solar cooking that stores heat in sand
25 comments
·November 24, 2025ortusdux
I've seen very simple DIY versions of this (stove coil directly wired to a panel) for home heating. At current panel pricing, I wonder if there is a config with a reasonable ROI.
21asdffdsa12
Just imagine the machinery you could power beneath the dessert, if you store the heat of the day.. Imagine for example salt water pits near the coast, where the heat creates fresh water mist, that rises and distills int he cold desert nights. To then be pumped onwards with sundriven steampumps, to places where the water is needed. No moving parts, just light redirecting glasfiber and infrastructure created beneath the sands creating geysers of fresh water miles away.
paddleon
Just imagine the incalculable wealth if you could store the energy of the sun in, say, plants, which would release the fresh mist during the night, build the health of the soil, and enable mobile life forms to carry the energy around to move it to other locations.
North Africa was the breadbasket of Rome, filled with life and water. Then we turned it into a desert.
loloquwowndueo
Awesome! Then imagine people wearing full-body solar-powered suits that capture and recycle body moisture and fluids, purify them and store them in a tank for later use. Would be fantastic!
akeck
The article talks about a similar device developed by Cal Poly in 2015: https://solar.lowtechmagazine.com/2023/08/direct-solar-power...
Legend2440
I was expecting some sort of cool focused-light cooker like a solar oven, but it's basically just an electric cooker powered by solar cells.
dv_dt
Because of their simplicity solar-cell based systems have become lower-cost and easier to install and maintain for water heating as panel + electric water heater, vs a piped direct solar thermal heating system. Higher "efficiency" for the direct thermal system, but overall system costs are lower for panel + heat.
I still love seeing the interplay with different combinations of physical systems and clever things humans figure out. Including with solar panels + other system items.
taneq
Is this a good point to mention that simple solar heating circuits work better if you use diodes in series (for a fairly constant voltage drop across the solar cells) than if you just use a resistive element? :)
actionfromafar
This should scale up for heating a house at night, too.
gsf_emergency_6
Yep! focussed light anything is a hassle really-- mirrors have to be maintained and positioned. For anything larger than a family, mirrors have to be unrealistically large..
There was a concentrated light power station in north of Vegas, but it bankrupted the company that built it. They didn't think about storage at the time
https://en.wikipedia.org/wiki/Crescent_Dunes_Solar_Energy_Pr...
>As of 2023, it is operated by its new owner, Vinci SA, and in a new contract with NV Energy, it now supplies solar energy _at night only_, drawing on [molten salt] thermal energy stored each day.
dagss
In buildings with water heating this is already commonly done, accumulating heat in water tanks. Size of water tanks is dimensioned after how much heat you have to store.
Electric heating with water heating is sometimes used in Northern Europe at least, often with a heat pump.
Ultimate would be solar panels on the roof, heat pump to multiply the electricity 3x-5x and water tank storage to last 24 hours.... Never recoup the investment though..
mrgaro
At least in Nordics (I'm from Finland) heat pumps are rapidly replacing other forms of heating. One can get a big enough heat pump for a 200m^2 house (including heating hot water) for around 10-15k, with a few thousand more for installation price.
Adding 10-15kWp of solar panels to the roof is around 6k more. It's definitively a no-brainer as it will recoup the investment in 5-10 years.
actionfromafar
Especially if panels continue to drop in price, a heat pump will just add needless complexity.
kirab
It even scales up to a whole town: https://polarnightenergy.com/news/worlds-largest-sand-batter...
trollbridge
For reasons I don’t understand, American cities seem allergic to installing new municipal steam or hot water utilities, even though things like cogeneration were an obvious use case for it, and now things like solar heat storage.
Barry-Perkins
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tony-john12
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That traditional biomass stove in paper's figures is perhaps the worst stove imaginable. Its efficiency could below 10%. Better designed stove has efficiency above 30% and has much less indoor air pollution.
Edit, efficiency measured by energy transferred to boiling water or cooking vs energy released from burning biomass.