Solar Chimneys: Viable Energy Solution Or A Lot Of Hot Air?

January 15, 2024 by Lewin Day 90 Comments

We think of the power we generate as coming from all these different kinds of sources. Oil, gas, coal, nuclear, wind… so varied! And yet they all fundamentally come down to moving a gas through a turbine to actually spin up a generator and make some juice. Even some solar plants worked this way, using the sun’s energy to heat water into steam to spin some blades and keep the lights on.

A solar updraft tower works along these basic principles, too, but in a rather unique configuration. It’s not since the dawn of the Industrial Age that humanity went around building lots of big chimneys, and if this technology makes good sense, we could be due again. Let’s find out how it works and if it’s worth all the bluster, or if it’s just a bunch of hot air.

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A series of plates and tubes sits in a tank of water. The plates are square with what looks to be a white coating.

Desalinating Water With The Sun

December 21, 2023 by Navarre Bartz 12 Comments

Getting fresh water from salt water can be difficult to do at any kind of scale. Researchers have developed a new method of desalinating water that significantly reduces its cost. [via Electrek]

By mimicking the thermohaline circulation of the ocean, the researchers from MIT and Shanghai Jiao Tong University were able to solve one of the primary issues with desalination systems, salt fouling. Using a series of evaporator/condenser stages, the seawater is separated into freshwater and salt using heat from the sun.

Evaporating water to separate it from salt isn’t new, but the researchers took it a step further by tilting the whole contraption and introducing a series of tubes to help move the water along and create eddy currents. These currents help the denser, saltier water move off of the apparatus and down deeper into the fluid where the salt doesn’t cause an issue with the device’s operation. The device should have a relatively long lifetime since it has no moving parts and doesn’t require any electricity to operate.

The researchers believe a small, suitcase-sized device could produce water for a family for less than the cost of tap water in the US. The (paywalled) paper is available from Joule.

If you’re curious about other drinking water hacks, check out this post on Re-Imagining the Water Supply or this previous work by the same researchers.

A dark brown bench suspended between two white and grey rectangular pillars. They are capped in the same brown HDPE material. Aluminum uprights go to a curved solar panel roof that looks somewhat similar to a paragliding chute. The bench is inside a clean-looking workshop with two large toolboxes against a plywood half wall.

Public Power, WiFi, And Shelter

December 13, 2023 by Navarre Bartz 39 Comments

In the US, we’re starting to see some pushback against hostile architecture, and in this vein, [benhobby] built a swanky public power and Wi-Fi access point.

This beautiful piece of infrastructure has 400 watts of solar plugged into 1.2 kWh of battery storage, and can dispense those electrons through any of its 120 VAC, USB-C, or USB-A plugs. The uprights are 3″ aluminum tubing attached to a base consisting of cinder blocks and HDPE panels. Power receptacles are housed in 3D printed enclosures with laser cut acrylic fronts. Three outdoor lights illuminate the stop at night, triggered by a photosensor.

The electronics and battery for the system, including the networking hardware, are in a weatherproof box on each side that can be quickly disconnected allowing field swaps of the hardware. Troubleshooting can then take place back at a workshop. One of the units has already been deployed and has been well-received. [benhobby] reports “There’s one in the wild right now, and it gets plenty of visitors but no permanent tenants.”

Want to see some more interesting hacks for public infrastructure? Check out this self-cooling bus stop, this bus bloom filter, or this public transit display.

Radio Emissions Over Sunspots Challenge Models Of Stellar Magnetism

December 1, 2023 by Donald Papp 1 Comment

Sustained radio emissions originating from high over a sunspot are getting researchers thinking in new directions. Unlike solar radio bursts — which typically last only minutes or hours — these have persisted for over a week. They resemble auroral radio emissions observed in planetary magnetospheres and some stars, but seeing them from about 40,000 km above a sunspot is something new. They don’t seem tied to solar flare activity, either.

The signals are thought to be the result of electron cyclotron maser (ECM) emissions, which involves how electrons act in converging geometries of magnetic fields. These prolonged emissions challenge existing models and ideas about how solar and stellar magnetic processes unfold, and understanding it better could lead to a re-evaluation of existing astrophysical models. Perhaps even leading to new insights into the behavior of magnetic fields and energetic particles.

This phenomenon was observed from our very own sun, but it has implications for better understanding distant stellar bodies. Speaking of our sun, did you know it is currently in it’s 25th Solar Cycle? Check out that link for a reminder of the things the awesome power of our local star is actually capable of under the right circumstances.

Solar Camera Built From Raspberry Pi

October 17, 2023 by Richard Baguley 29 Comments

Ever since an impromptu build completed during a two-week COVID-19 quarantine back in 2020, [Will Whang] has been steadily improving his Raspberry Pi solar photography setup. It integrates a lot of cool stuff: multiple sensors, high bandwidth storage, and some serious hardware. This is no junk drawer build either, the current version uses a $2000 USD solar telescope (an LS60M with 200mm lens) and a commercial AZ-GTi mount.

He also moved up somewhat with the imaging devices from the Raspberry Pi camera module he started with to two imaging sensors of his own: the OneInchEye and the StarlightEye, both fully open source. These two sensors feed data into the Raspberry Pi 4 Compute Module, which dumps the raw images into storage.

Because solar imaging is all about capturing a larger number of images, and then processing and picking the sharpest ones, you need speed. Far more than writing to an SD Card. So, the solution [Will] came up with was to build a rather complex system that uses a CF Express to NVME adapter that can keep up, but can be quickly swapped out.

Unfortunately, all of this hard work proved to be in vain when the eclipse came, and it was cloudy in [Wills] area. But there is always another interesting solar event around the corner, and it isn’t going anywhere for a few million years. [Will] is already looking at how to upgrade the system again with the new possibilities the Raspberry Pi 5 offers.

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E-Bikes Turned Solar Car

October 9, 2023 by Danie Conradie 20 Comments

There is something to be said for a vehicle that gains range just by standing outside in the sun. In the video after the break, [Drew Builds Stuff] demonstrates how he turned a pair of bicycles into a solar-powered vehicle.

The inspiration for this build started with a pair of 20″ steel framed fat tire bikes [Drew] picked up in a liquidation sale. He welded up a simple steel chassis, and attached the partial bicycle frame and forks to the chassis, using them as steerable front wheels. A short arm was welded to each of the fork, linking them together with threaded rods and rod ends that connect to centrally mounted handlebars. The rear driving wheels are from a 20″ e-bike conversion kit, with the disk brake assembly from the cannibalized bikes.

The solar part of this build comes in the form of three 175W flexible solar panels mounted on cedar frames, coming in at 10 lbs per mounted panel. [Drew] considered using conventional rigid solar panels, but they would have been 4-6 times heavier. The two panels mounted to the rear of the vehicle are on a hinged frame to allow easy access to the electronics below. Battery storage is made up of two 24V 100Ah batteries wired in series, connected to a 60A solar charge controller and the e-bike motor controllers.

The vehicle has a top speed of about 45km/h and 100km range on batteries alone. It might not be fast or engineered for maximum efficiency, but it looks like a ton of fun and relatively simple to build. As [Drew] says, it’s not a how-to for building a perfect solar-powered vehicle, it’s how he built one.

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Passive Desalination Discovers How To Avoid Salt-Clogging

October 2, 2023 by Donald Papp 15 Comments

Saltwater is plentiful, but no good for drinking. Desalinization is the obvious solution, but a big problem isn’t taking the salt out, it’s where all that leftover salt goes. Excess salt accumulates, crystallizes, collects, and clogs a system. Dealing with this means maintenance, which means higher costs, which ultimately limits scalability.

The good news is that engineers at MIT and in China have succeeded in creating a desalination system that avoids this problem by intrinsically flushing accumulated salt as it is created, keeping the system clean. And what’s more, the whole thing is both scalable and entirely passive. The required energy all comes from gravity and the sun’s heat.

To do this, the device is constructed in such a way that it mimics the thermohaline circulation of the ocean on a small scale. This is a process in which temperature and density differentials drive a constant circulation and exchange. In the team’s system, this ultimately flushes concentrations of salt out of the system before it has a chance to collect.

The entirely passive nature of the device, its scalability, and the fact that it could desalinate water without accumulating salt for years means an extremely low cost to operate. The operating principle makes sense, but of course, it is careful engineering that shows it is actually possible. We have seen projects leveraging the passive heating and circulation of water before, but this is a whole new angle on letting the sun do the work.