Ultra-Low Power, Energy Harvesting Battery Charger

July 8, 2018 by Donald Papp 10 Comments

This half-inch square ultra-low power energy harvesting LiPo cell charger by [Kris Winer] uses a low voltage solar panel to top up a small lithium-polymer cell, which together can be used as the sole power source for projects. It’s handy enough that [Kris] uses them for his own projects and offers them for sale to fellow hackers. It’s also his entry into the Power Harvesting Challenge of the Hackaday Prize.

The board is essentially a breakout board for the Texas Instrument BQ25504, configured to charge and maintain a single lithium-polymer cell. The BQ25504 is an integrated part that takes care of most of the heavy lifting and has nifty features like battery health monitoring and undervoltage protection. [Kris] has been using the board along with a small 2.2 Volt solar panel and a 150 mAh LiPo cell to power another project of his: the SensorTile environmental data logger.

It’s a practical and useful way to test things; he says that an average of 6 hours of direct sunlight daily is just enough to keep the 1.8 mA SensorTile running indefinitely. These are small amounts of power, to be sure, but it’s free and self-sustaining which is just what a remote sensing unit needs.

Algae On Your Plate

June 8, 2018 by Brian McEvoy 34 Comments

For those of us who grow up around natural swimming holes, algae are the reason we have to wash after taking a dip. Swimmer’s itch* or just being covered in green goop is not an attractive way to spend an afternoon. Lumping all algae together is not fair, some of it is nasty but some of it is delicious and humans have been eating it for generations.

If you are thinking that cases of algae cuisine are not widespread and that algae does not sound appealing, you are not alone. It is a tough sell, like convincing someone to try dandelions for the first time. It may not warrant a refrigerator section in the grocery store yet, but algae can produce protein-rich food which doesn’t require a lot of processing.

Currently, there is a lot of work to be done to bring up the efficiency of algae farms, and Qualitas has already started. The leaps they are making signify just how much room we have for improvement. The circulating paddle wheels, which can be seen in the video below the break, use one-third of the energy from their previous version. Their harvester uses one-thirtieth! Right now, their biggest cost comes from tanks of carbon dioxide, which seems off given that places such as power plants pay to get rid of the stuff. That should give some food for thought.

The 2018 Hackaday prize could use some algal submissions and you could take that to the bank. Ready to start growing your own algae, automate the process. It may also keep you from tripping while walking to the grocery store, or you can print with it.

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Their Battery Is Full Of Air

May 26, 2018 by Al Williams 46 Comments

Storing electrical energy is a huge problem. A lot of gear we use every day use some form of battery and despite a few false starts at fuel cells, that isn’t likely to change any time soon. However, batteries or other forms of storage are important in many alternate energy schemes. Solar cells don’t produce when it is dark. Windmills only produce when the wind blows. So you need a way to store excess energy to use for the periods when you aren’t creating electricity. [Kris De Decker] has an interesting proposal: store energy using compressed air.

Compressed air storage is not a new idea. On a large scale, there have been examples of air compressed in underground caverns and then released to run a turbine at a future date. However, the efficiency of this is poor — around 40 to 50 percent — mainly because the air heats up during compression and often needs to be prewarmed (using energy from another source) prior to decompression to prevent freezing. By comparison, batteries can be 70 to 90 percent efficient, although they have their own problems, too.

The idea explored in this paper is not to try to store a power plant’s worth of energy in a giant underground cavern, but rather use smaller compressed air setups like you would use batteries to store power at the point of consumption. The technology is called micro-CAES (an acronym for compressed air energy storage).

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Solar Power In A Can!

March 2, 2018 by James Hobson 17 Comments

When spending time camping, people often bring lanterns, flashlights, and the like — you might even bring along a solar charger. Instructables user [bennelson] is combining all your electrical powered needs by cramming solar power into a can.

Already designed to resist the elements, [bennelson] is using a 50cal. ammo can for a portable enclosure. Inside, he’s siliconed a 15AH, 12V lead-acid battery in the centre to maintain balance and to leave room for the wiring and storage. One cardboard mockup later, he laser-cut the top panel from 1/8″ plywood and secured a 20A solar charge controller, a four-in-one socket panel, and two banana plugs on its top face.

[bennelson] is using 12 AWG wire to match the 20A rating of the solar charge controller — including a fuse for safety — and lever lock-nut connectors to resolve some wiring complications. Industrial velcro keeps the top panel in place and easily removed should the need arise. When he’s out camping, he uses an 18V, 1A solar panel to charge, but can still use a DC power adapter to charge from the grid. Check out the full build video after the break!

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Home Brew Solar Cells For The Chemically Curious

January 26, 2018 by Dan Maloney 20 Comments

The idea of making your own semiconductors from scratch would be more attractive if it weren’t for the expensive equipment and noxious chemicals required for silicon fabrication. But simple semiconductors can be cooked up at home without anything fancy, and they can actually yield pretty good results.

Granted, [Simplifier] has been working on the method detailed in the video below for about a year, and a look at his post on copper oxide thin-film solar cells reveals a meticulous approach to optimize everything. He started with regular window glass, heated over a propane burner and sprayed with a tin oxide solution to make it conductive while remaining transparent. The N-type layer was sprayed on next in the form of zinc oxide doped with magnesium. Copper oxide, the P-type layer, was electroplated on next, followed by a quick dip in copper sulfide to act as another transparent conductor. A conductive compound of sodium silicate and graphite was layered on the back to form the electrical contacts. The cell worked pretty well — 525 mV open circuit voltage and 6.5 mA short-circuit current. Not bad for home brewed.

If you want to replicate [Simplifier]’s methods, you’ll find his ample documentation of his site. Of course, if you yearn for DIY silicon semiconductors, there’s a fab for that, too.

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Imaging The Neighborhood With Solar Panels

January 5, 2018 by Tom Nardi 27 Comments

Like many people who have a solar power setup at home, [Jeroen Boeye] was curious to see just how much energy his panels were putting out. But unlike most people, it just so happens that he’s a data scientist with a deep passion for programming and a flair for visualizations. In his latest blog post, [Jeroen] details how his efforts to explain some anomalous data ended with the discovery that his solar array was effectively acting as an extremely low-resolution camera.

It all started when he noticed that in some months, the energy produced by his panels was not following the expected curve. Generally speaking, the energy output of stationary solar panels should follow a clear bell curve: increasing output until the sun is in the ideal position, and then decreasing output as the sun moves away. Naturally cloud cover can impact this, but cloud cover should come and go, not show up repeatedly in the data.

[Jeroen] eventually came to realize that the dips in power generation were due to two large trees in his yard. This gave him the idea of seeing if he could turn his solar panels into a rudimentary camera. In theory, if he compared the actual versus expected output of his panels at any given time, the results could be used as “pixels” in an image.

He started by creating a model of the ideal energy output of his panels throughout the year, taking into account not only obvious variables such as the changing elevation of the sun, but also energy losses through atmospheric dispersion. This model was then compared with the actual power output of his solar panels, and periods of low efficiency were plotted as darker dots to represent an obstruction. Finally, the plotted data was placed over a panoramic image taken from the perspective of the solar panels. Sure enough, the periods of low panel efficiency lined up with the trees and buildings that are in view of the panels.

We’ve seen plenty of solar hacks, but this one has to be something of a first. Usually people are more worried about maximizing efficiency or tracking the sun with them.

Making Solar Cells

January 4, 2018 by Al Williams 11 Comments

We will admit that it is unlikely you have enough gear in your basement to make a solar cell using these steps. However, it is interesting to see how a bare silicon wafer becomes a solar cell. If you’ve seen ICs going through fabrication, you’ll see a lot of similarities, but there are some differences.

The process calls for a silicon wafer, some ovens, spin coaters, photolithography equipment, and a dice saw, among other things. Oh, you probably also need a clean room. Maybe you should just buy your solar cells off the shelf, but it is still interesting to see how they are made.

Modern solar cells have some extra structures to improve their efficiency, but the cells in this video are pretty garden-variety. For example, some experimental cells use multiple layers of active devices, each tuned to absorb a different wavelength of light.

If you really want to make your own, there’s another process where you can start with some copper and wind up with a kind of solar cell that uses a copper-based semiconductor material. But don’t be fooled into thinking that making the silicon variety is totally out of reach to hackers, we’ve seen [Sam Zeloof] pull it off.

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