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Power Hack and the Brick that Generates Electricity

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Hacking energy generation for developing countries and a simple thermopile brick solution.

Last week I was honoured to have been invited to a hackathon hosted by DesignSpark in partnership with Practical Action, the charity that puts technology to use in challenging poverty. For those not familiar with hackathons, the idea is that you rapidly prototype new solutions, getting as close to a working implementation as possible given the available time and resources.

Power Hack took place over the course of two days and the objective was to come up with novel solutions for domestic power generation, that are suited to use in developing countries. Of course, with a brief such as this and so many possibilities it wouldn't be practical to have all the components potentially required on hand. However, we did have no less than three 3D printers.

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What this meant is that custom mechanical parts could be quickly designed using the DesignSpark Mechanical tool before being printed out. So at the very least we would have physical models that allowed us to validate the design of components and assemblies, thereby taking us further down the development path than if we simply had drawings and perhaps cardboard models.

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Adrian Bowyer demonstrating the RepRap to Practical Action's Neil Noble

Once we had been briefed we were split up into three teams, Maxwell, Kilby and Faraday. I was in Team Maxwell, along with Adrian Bowyer, inventor of the RepRap self-replicating 3D printer, Daniel Tinsley of Schneider Electric, Subhash Mungarwadi from TE Connectivity, and Mario Caruso of QinetiQ.

Developing an idea

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With introductions out of the way we got straight to brainstorming and came up with numerous ideas — including a biogas generator and mechanical tracker for solar energy — before finally settling on using heat to generate electricity via the humble thermocouple and Seebeck effect.

We found this means of power generation particularly compelling since it's such a simple technology and requires nothing more than the combination of two dissimilar metals, with one junction kept at a higher temperature than a second. Furthermore, it doesn't matter where you are in the world, you always need to eat and this requires cooking food, therefore there is the possibility of generating electricity as a by-product if thermocouples could be built into a rudimentary stove.

Since the amount of electricity generated by a single thermocouple is very small we would need many thousands of these, to create a thermopile that could deliver a useful amount of electricity. We quickly arrived at the idea of building these into bricks so that they would be robust and could be used in the structure of the stove. Each brick would then contain a stack of thin clay plates wound with alternating lengths of copper and iron wire, with junctions facing towards the fire and those aligned down the opposite side of the plate on the outside of the stove.

Prototyping

A simple plate was designed with notches down either side so as to help locate the hot and cold wire junctions. This was printed out on the RepRap and then Adrian set about winding thin copper wire onto it, with twists down either side where in practice there would be a copper/iron junction.

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The completed plate can be seen at the top of this post. In an actual brick — we'd dubbed it the “Seebrick” at this point, after the Seebeck effect — this would be a thin sheet of clay and there would be a stack of these plates connected in series, with thin sheets of wet clay separating them and liquid clay slip poured into the brick mould before it is finally fired.

We originally envisaged having a single brick generating 2.5 watts — enough to power modest LED lighting in three rooms or to charge multiple USB devices. However, we soon realised that this would mean an awful lot of wire and junctions crammed into a single brick, and eventually opted for on having six bricks generate 2.5W, which was much more achievable. It also meant that in the event of a junction failing you didn't lose all your electricity generation capacity.

Of course, forming tens of thousands of thermocouple junctions from short lengths of metal wire joined end-on-end would quickly become incredibly tedious. And equally error prone. Therefore we had the idea to create a machine that would automate this task, by drawing copper and iron wire from two reels, before cutting and spot welding it.

Once we'd agreed on the machine's operation Adrian and Subhash set out designing the parts before sending these to print.

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Once printed a small amount of hand finishing needed to be done before they could be fitted together.

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The operation of the main mechanism is pretty straightforward, with blades to cut the wires and graphite electrodes to spot weld them.

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Although we didn't have time to prototype the electronics these would be equally as simple, with a motor to drive the mechanism and mechanical contacts to charge a capacitor bank before it is then discharged through the spot welder electrodes. Since 0.1mm wires would be used very little current should be required for this operation.

Next a mockup of a stove was constructed from cardboard, with a hole in the right-hand wall where the Seebrick model could be positioned.

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For added effect a bowl was placed on the stove, with red LEDs used where the fire would be and white LEDs hooked up to our dummy Seebrick.

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In the run up I wasn't too sure of the exact scope of the event and whether we might be hacking on electronics and/or software, and so I'd brought along a compact mobile phone base station development kit, based around the open source UmTRX transceiver from Fairwaves. The thought being that communications and power go hand-in-hand and there might be a novel use for it.

Even though we didn't get to power up the base station it came in handy as a prop when we calculated that a village of 50 households with Seebricks, each cooking 3 times a day, could contribute 50% of their power generation capacity to charge a small bank of batteries, that would in turn power the mobile base station plus a satellite uplink for 10 hours a day!

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The UmTRX and antennas can be seen on the left-hand side of the table

Presentations

At the end of day two each team had to present their solution and a winner would be selected. We were up first and Mario boldly volunteered to present the Seebrick and machine for manufacturing thermocouple plates. It's not always easy to tell how these things go, but our solution seemed to be well received.

Next up were Team Kilby with a pretty slick presentation that included video. Their solution was based on the recognition that laptop battery packs are so often disposed of while many of the cells still work, and that also these cells are typically a common type. What they proposed was a system whereby the cells could be easily harvested and quickly fitted into easy to manufacture packs, with new new charge and discharge controllers and it being trivial to swap out cells.

The final presentation came from Team Faraday, with not one but two solutions. The first being an evolution of the Moser Light which uses a plastic bottle filled with water to pipe sunlight into a room. Dubbed the Electro Moser Light, the addition of a potted LED would give the best of the traditional solar light and LED lighting. The second being a multi-purpose hub that could be used to generate power from wind, steam or water.

And, I'm delighted to be able to say that Team Maxwell were declared the winners!

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Final thoughts

It was a thoroughly enjoyable event and to say that most of us had never met before (Adrian and I had previously met briefly at an OSHUG meeting), I think our team worked extremely well together, with each bringing valuable perspectives and different areas of expertise to the challenge. And the question we've all since asked is: how can we keep up the momentum and take this forward? I'm not sure what the answer is just yet, but hope that we are able to find some way to.

Andrew Back

Open source (hardware and software!) advocate, Treasurer and Director of the Free and Open Source Silicon Foundation, organiser of Wuthering Bytes technology festival and founder of the Open Source Hardware User Group.
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