The folks at Low Tech Magazine are here again, this time with a solar powered coffee maker. Lest you think of a large parabolic mirror with a pot at its focus, in this case the device is much more friendly. It’s a table-top appliance that relies upon a 100 W 12 V panel for its operation.
They make the point that an electric coffee pot requires at least 300 W to work, so what’s the secret? In this case, insulation, as a standard moka pot is placed within a nichrome heating element set in mortar and surrounded by cork. On the outside are tiles, though they appear largely ornamental and the write-up suggests you could experiment with other materials to serve as an enclosure.
It appears to be an effective coffee maker, with the significant caveat that it’s hardly fast. In full sunlight the first pot takes over an hour to brew, with subsequent ones once it’s up to temperature being somewhat faster. But you can’t argue with the idea of free power, even if your favourite caffeinated beverage may now take a while to appear.
We like this idea, despite its slow brewing. We’ve featured Low Tech Magazine before, not least in their solar powered oven.
I came across this website a few years ago and immediately fell in love with the idea of a solar powered web server. Sadly I forgot the name of the website and didn’t really attempt to search it.
Thanks for reminding me [Jenny], I now have a nice addition to my reading list
In a perfect world with a solar panel that doesn’t have loss and a perfect insulation, it would take 8 minutes and 22 seconds, based on a 3 cup (150ml) mokka pot and the 100W panel.
With a warm mortar slab, which is mentioned, it takes 20 minutes. It’s only the first one that takes over an hour. Now, 20 minutes vs 8 minutes, with a solar panel that won’t be 100% effective, that’s actually pretty reasonable.
The two biggest improvements I can find are, covering the top and a much better insulation. Quality ceramic fiber blankets for example, with an outer coating for the fibers. Make a cover on it to cover the top and that solar panel might be able to produce coffee much faster. It’s also generally advised to start out brewing with hot water, reducing the time even more.
Very interesting article.
A more efficient method of heating would be to put the heating element around a copper tube and then drip water through it, through the coffee and straight into a thermos flask.
In the past I’ve made tea using tea lights with this method, and it’s surprisingly effective although each candle is only worth about 40 Watts and about half of that blows past the heating coil. That was my experiment into “how to make do when the power goes and you haven’t prepared”. I made a tinfoil oven to cook an egg, a single cookie, brewed some tea…
Still doesn’t make the thing cheap though. The cost of power from a 100 Watt solar panel that’s not generating useful power most of the time is going to be enormous compared to grid power, because you pay the investment but you’re not making use of the energy it’s providing.
I’m a little bothered by the presence of the solar panel, which is far from low-tech when you consider the machinery needed to produce it. It would be cool to see a version with a Stirling engine powering a heat pump to transport heat and raise the temperature.
That’s a common theme with the helpful gadget nerds though. If there’s no real practical use of it or it performs poorly, it’ll be “sold” as something for emergency use, or for the unprivileged, or as an aid for disabled people… just something that sounds plausible to justify spending so much time and money tinkering with it.
The typical version is, “This gadget will help people in developing countries. It uses parts only available from highly developed countries.” See the OLPC laptop, or solar street lights in rural India (most got stoned to bits by kids, or stolen for the solar panels).
I do some volunteer work in developing nations and you are spot on.
There is a whole room full of modern equipment that was donated with the best intentions but broke and became a boat anchor. The stuff still in use is from like the 60’s (guessing) that is bullet proof, easily repairable with regular tools, and seems to work just fine without touchscreens and, for some stuff, is pneumatic powered and doesn’t even need electricity.
Also, a similarly sized panel but made with reflectors and copper tube painted black would generate 3-5 times as much heat and be less sensitive to solar angle, so it would work earlier in the morning and later in the evening. When it gets running, the water will boil inside and pump itself around.
If you use that all through the day to collect hot water in an insulated tank, by next morning you’ll have gallons of very hot water. You can’t use that water directly as it would be contaminated with stuff, but you can use it to heat up a smaller quantity of water through a loop in the tank and use a bit of flame or a smaller solar panel to bring that up to a boil.
Solar powered coffee roaster.
Nice, today morning I thought about solar panel powered coffee machine, but with battery instead mortar.
Trying to sell us an under-powered, mildly insulated electric kettle as solar ?
That´s borderline abusive.
The most idiotic thing about this, when not making coffee, the solar panel isn’t used.
Perhaps not the most idiotic, that’s the whole Fn idea.
Honorable mention, need to wait till noon to make coffee.
It’s just ‘solar panels on cars’ in miniature and without a battery to not effectively charge.
Some people need the definition of ‘fungible’ pounded into their heads.
Precisely, i would just hook it up to one of those big power banks and then you can just use a regular coffee maker with it. Charges in half an hour, but still makes coffee in regular time. You can also use the extra energy for other things.
I am not sure where the line is drawn for low tech stuff. For sure low tech can also mean easily available, as opposed to custom made.
There is no free power. You paid for the solar panel. That’s what, $150 or thereabouts?
The energy to boil a cup (150 ml) of coffee in a kettle is about 15 Watt-hours. The faster you do it, the more efficient it will be. With a US-average electricity price at 12 c/kWh that’s roughly 0.2 cents a cup. To cover the $150 for the panel, you’d have to brew 75,000 cups of coffee.
Six cups a day, you’ll be at it for 34 years.
Yeah, taking energy from the panel only for brief moments of time, makes it not worthy, especially if you over inflate the price of the panel and pick a very cheap electricity rate.
But put a bigger panel and power a lot more things and things look different. Here in Europe balcony plug in solar is starting to become a thing, with 800W kits reaching even below 500 euro. Depending on the situation, it can pay for itself in 3-5 years.