Home Brew Solar Cells for the Chemically Curious

Hackaday Solar Hacks -

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.

Imaging The Neighborhood with Solar Panels

Hackaday Solar Hacks -

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.

Expected versus actual power output.

[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.

Filed under: green hacks, Solar Hacks

Making Solar Cells

Hackaday Solar Hacks -

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.

Filed under: Solar Hacks

AMSAT MPPT Goes to Infinity and Beyond

Hackaday Solar Hacks -

AMSAT, the Radio Amateur Satellite Corporation, joined forces with students from Rochester Institute of Technology to create a MPPT attached to a Fox-1B CubeSat. It successfully launched into orbit on November 18th strapped to the back of a Delta II rocket. This analog MPPT, or Maximum Power Point Tracker, is used for optimizing the draw of a power cell in correspondence to the output of solar panels on the 10cm x 10cm satellite. In a nutshell, this works by matching the voltage of the two together. If you haven’t gotten a chance to play around with one of these first hand, Hackaday’s own [Elliot Williams] wrote up a thorough explanation of the glorious MPPT’s efficiency.

This little guy is currently hurdling along in an orbit every 90 minutes. During each of these elliptical trajectories, the satellite undergoes brutal heating and cooling cycles. The team calculated that this package will undergo a total of 29,200 orbits around Earth during its 5 year mission. This means that there are 29,200 tests for it to crack — quite literally — under pressure. To add another level of difficulty, the undergrad team didn’t have funding for automated board assembly. This meant that they had to hand solder over 400 micro components onto this board, adding additional human error to be accounted for in the likelihood of a failure. But so far, this puppy is going strong. This truly shows the struggles that can be overcome with a little elbow grease, hard work, and plain ‘ole good engineering.

They created some sharp-looking documentation for this project. I would highly suggest taking a couple of minutes to read their Fox-1 MPPT document if you are interested in seeing the carefully thought out design in detail. The collection of schematics shown above was used to predict the maximum power point voltage. The analog computer used Y = mX + B to accurately predict the MPPT based off of solar panel temperature. In doing this, they were able to account for radiation in orbit causing bit flips. Understanding all of these factors was essential for the success of this tiny beast.

We would like to say good luck to the RIT team of Bryce Salmi, Brenton Salmi, Ian MacKenzi, and Daniel Corriero in their future endeavors. Sending anything into space and then keeping it running once it gets there is no easy task, and there is already another MPPT set to launch on a Fox-1E CubeSat aboard a Virgin Galactic Launcher One in December, 2017. Check out some of the necessary testing they did on it below to ensure that this would be a successful mission. Let us know if you think this is as awesome of a collaboration as we do.

Filed under: Solar Hacks

Joan Feynman Found Her Place in the Sun

Hackaday Solar Hacks -

Google ‘Joan Feynman’ and you can feel the search behemoth consider asking for clarification. Did you mean: Richard Feynman? Image search is even more biased toward Richard. After maybe seven pictures of Joan, there’s an endless scroll of Richard alone, Richard playing the bongos, Richard with Arline, the love of his life.

Yes, Joan was overshadowed by her older brother, but what physicist of the era wasn’t? Richard didn’t do it on purpose. In fact, no one supported Joan’s scientific dreams more than he did, not even their mother. Before Richard ever illuminated the world with his brilliance, he shined a light on his little sister, Joan.

Baby Joan works on the Feynman smirk. Image via r/physics A Sign From Above

Joan Feynman was born in Queens, New York City in 1927 to Lucille and Melville Feynman, nine years after Richard came along. Both children were raised to be insatiably curious. Their parents encouraged them to always ask why, and to take notice of the world around them.

Joan deeply admired her brother and was always interested in whatever he was doing. Richard capitalized on this right away, making Joan his first student. He taught her how to add simple numbers together when she was three. Whenever Joan got one right, Richard let her pull his hair and would make funny faces. Anything Richard learned about math or science, he would repeat all over the house, which had the dual effect of reinforcing his understanding and piquing Joan’s interest.

Their working relationship continued, too. When Joan was five, Richard hired her assist him in his bedroom electronics lab. For a few cents a week she would flip switches at the appropriate time. Sometimes she had to put her finger in a spark gap to amuse his friends.

One night when Joan was quite young, Richard pulled her out of bed and led her down the street to a nearby golf course. He told her to look up into the sky, which was ablaze in the brilliant colors of aurora borealis. Joan was mesmerized. In that moment, her destiny became clear to her.

No one could foil Joan’s plans. Image via Popular Science A Woman’s Place is in a College-Level Astronomy Textbook

At the time, no one knew what caused auroras. Joan became determined to unlock their mysteries. Her mother had other ideas, though. When Joan proclaimed to her at age eight that she wanted to be a scientist, her mother told her that “women can’t do science because their brains aren’t able to understand enough of it.” Joan was crushed. From that day on, she doubted her abilities.

Lucille Feynman wasn’t trying to be cold-hearted or unprogressive. She had marched for women’s suffrage in her teens. Still, she believed that women weren’t as intellectually capable as men. This was then.

For a while, Joan’s aspirations were put on hold. There weren’t many women scientists to look up to in the 1930s, anyway, except for Marie Curie. She was iconic, perhaps too much so. Joan saw her as mythological, a majestic unicorn of scientific greatness, not a human woman she could try to emulate.

Even so, Joan wasn’t discouraged enough to lose interest in science. For one thing, Richard had never stopped rooting for her. When she turned fourteen, he gave her a college-level astronomy textbook. She found the material difficult but took his advice to start over from the beginning when she got stuck.

On page 407, Joan found something that would give her the one thing she needed the most to seal her future—validation. On the page was a graph of spectral absorption lines credited to one Cecilia Payne. Joan was ecstatic. A woman scientist! Finally, concrete proof that her mother was wrong. Not only can women understand science, they can have their work referenced in a textbook. Joan’s confidence was renewed.

The science of homemaking. Image via NPR The Science of Homemaking

Of course, becoming a scientist wasn’t that simple. Joan faced adversity everywhere. During her undergraduate studies at Oberlin, she did all the lab experiments while her ill-prepared lab partner got all the credit. A professor at Syracuse University told Joan she should write her dissertation on cobwebs, because she would encounter them regularly as a housewife.

After finishing her PhD in 1958, Joan tried to find a research scientist position by posting in New York Times classifieds. The listings were split by gender, and they told her she wasn’t allowed to post among the men. But who would look for an astrophysicist in the women’s section?

By the early 1960s, Joan was working for a small company that made solid-state devices. She was also raising two young sons with her husband Rich Hirshberg, a fellow scientist she met at Oberlin. When the commute became too much, she quit to try full-time domesticity. For three years, Joan did nothing but cook, care for the boys, and clean the family’s five-bedroom house. The only semblance of science in her life involved baked goods. Joan was miserable. On the advice of a psychiatrist, she went to Lamont Observatory at Columbia University to look for a job, but worried that she’d been away too long. Immediately, she had three offers.

Solar Interference

At Lamont, Joan studied interactions between the magnetosphere and the solar wind. In those days, astrophysicists believed the magnetosphere was closed and tapered like a teardrop. Joan discovered that it’s actually open-ended, and has a long tail on the side opposite the Sun where the solar wind don’t blow. In an open model, the Sun’s magnetic field more directly influences the magnetosphere.

Several years later at NASA’s Jet Propulsion Laboratory (JPL), Joan was able to demonstrate that aurora happen when solar particles penetrate the magnetosphere. As these particles mix with those in the magnetosphere, the collisions manifest as brilliant colors.

Solar Wind vs. Magnetosphere. Image via NASA

She also studied sunspot cycles and coronal mass ejections (CME). These are solar storms that can greatly affect the magnetosphere and are capable of disabling satellites and interrupting terrestrial communications. At the time, CMEs were difficult to pinpoint. Joan’s research showed that wherever there are CMEs, there is also a significant increase of helium in the solar wind.

Joan also proved that CMEs occur in groups. From this research, she devised a statistical calculation to predict the number of high-energy particles that could bounce off the average spaceship during its lifetime. This important development resulted in better designs with greater longevity. In 1999, NASA honored her with an Exceptional Scientific Achievement Award.

Joan retired from JPL in 2002. Since then, she has turned her focus to the effect of solar cycle variations on climate change  and historical climate anomalies. At the age of 90, she’s still fascinated by all the crazy things the Sun does and is still determined to find explanations.

Joan thinks the Sun is excellent. Image via BBC


Filed under: Hackaday Columns, History, Original Art, solar hacks

Mendocino Motor Drives Cubicle Conversations

Hackaday Solar Hacks -

Mendocino motors are solar-powered electric motors that rely on pseudo-levitation.  The levitation comes from magnets mounted on either end of the shaft, which repel same-field magnets fixed below them into the base.  When light shines on the solar panels, current flows through connected magnet wire windings, creating an electromagnetic field that interacts with a large stationary magnet mounted underneath. These constantly repelling forces spin the shaft, and the gaps between the solar panels provide the on-off cycle needed to make it spin 360°.

As [Konstantin] discovered, building this simple motor and getting it to spin depends on a lot of factors. The number of windings, the weight of each solar panel, and the magnet sizes all figure in. [Konstantin]’s struggles are your gain, however. His Instructable takes the guesswork out of the tolerances and he designed a nice, open-source 3D-printed structure to boot.

You’re right, these motors can’t do much work. But it would definitely look cool on your desk and might even start a conversation or two. If not, whip up this little electromagnetic train.

Filed under: how-to, solar hacks
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