Solar Hacks

203 Articles

PTPM Energy Scavenger Aims For Maintenance-Free Sensor Nodes

August 1, 2018 by 13 Comments

[Mile]’s PTPM Energy Scavenger takes the scavenging idea seriously and is designed to gather not only solar power but also energy from temperature differentials, vibrations, and magnetic induction. The idea is to make wireless sensor nodes that can be self-powered and require minimal maintenance. There’s more to the idea than simply doing away with batteries; if the devices are rugged and don’t need maintenance, they can be installed in locations that would otherwise be impractical or awkward. [Mile] says that goal is to reduce the most costly part of any supply chain: human labor.

The prototype is working well with solar energy and supercapacitors for energy storage, but [Mile] sees potential in harvesting other sources, such as piezoelectric energy by mounting the units to active machinery. With a selectable output voltage, optional battery for longer-term storage, and a reference design complete with enclosure, the PPTM Energy Scavenger aims to provide a robust power solution for wireless sensor platforms.

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High Efficiency, Open-Sourced MPPT Solar Charger

July 31, 2018 by 28 Comments

A few years ago, [Lukas Fässler] needed a solar charge controller and made his own, which he has been improving ever since. The design is now mature, and the High Efficiency MPPT Solar Charger is full of features like data logging, boasts a 97% efficiency over a range of 1 to 75 Watts, and can be used as a standalone unit or incorporated as a module into other systems. One thing that became clear to [Lukas] during the process was that a highly efficient, feature-rich, open-sourced hardware solution for charge controllers just didn’t exist, at least not with the features he had in mind.

Data logging and high efficiency are important for a charge controller, because batteries vary in their characteristics as they recharge and the power generated from things like solar panels varies under different conditions and loads. An MPPT (Maximum Point Power Tracking) charger is a smart unit optimized to handle all these changing conditions for maximum efficiency. We went into some detail on MPPT in the past, and after three years in development creating a modular and configurable design, [Lukas] hopes no one will have to re-invent the wheel when it comes to charge controllers.

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DIY solar panel vs. commercial solar panel

DIY Vs. Commercially Made Solar Panel

July 23, 2018 by 31 Comments

The price of commercially made solar panels on eBay is around $1 per watt and have been for a few years, but the price of individual solar cells are likewise at a low price per watt, around $0.48.  Looking at those prices, it’s tempting to say that it’d be cheaper to just buy the solar cells and put together your own panels. But is it? Simply adding up all the costs might seem like a good way to tell, but you’d need to make a panel to really see what works and what doesn’t.

Part US$ Euros €
solar cells 53 45
aluminum U-channel 20 17
plexiglass 43 37
adhesive 8 7
clear epoxy resin 40 34
Total $164 140€

And so [GreatScott] did just that, with his own side-by-side comparison. He made a 100-watt solar panel and mounted it on his roof beside his commercially produced 100-watt one and compared their output.

The cost of his DIY panel rose quickly. To make a somewhat comparable panel he needed to buy aluminum U-channels, clear epoxy resin, and more. Shown here is the breakdown of his costs.

His commercial 100 watt solar panel would cost him $103 today (87.90€). Compare that to his $164 DIY panel. Also, his DIY one likely won’t weather as well as the commercial one and may not handle high temperatures as well either. You can see the results of his testing in the video below, along with all his construction steps.

Another component open to DIYers in a solar system is the charge controller which takes the solar panel’s output and uses it to charge the battery, with added features like MPPT. Check out this DIY charge controller with MPPT and WiFi for data logging.

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Energy Harvesting Design Doesn’t Need Sleep

July 19, 2018 by 10 Comments

Every scrap of power is precious when it comes to power harvesting, and working with such designs usually means getting cozy with a microcontroller’s low-power tricks and sleep modes. But in the case of the Ultra Low Power Energy Harvester design by [bobricius], the attached microcontroller doesn’t need to worry about managing power at all — as long as it can finish its job fast enough.

The idea is to use solar energy to fill a capacitor, then turn on the microcontroller and let it run normally until the power runs out. As a result, a microcontroller may only have a runtime in the range of dozens of microseconds, but that’s just fine if it’s enough time to, for example, read a sensor and transmit a packet. In early tests, [bobricius] was able to reliably transmit a 16-bit value wirelessly every 30 minutes using a small array of photodiodes as the power supply. That’s the other interesting thing; [bobricius] uses an array of BPW34 photodiodes to gather solar power. The datasheet describes them as silicon photodiodes, but they can be effectively used as tiny plastic-enclosed solar cells. They are readily available and can be arranged in a variety of configurations, while also being fairly durable.

Charging a capacitor then running a load for a short amount of time is one of the simplest ways to manage solar energy, and it requires no unusual components or fancy charge controllers. As long as the load doesn’t mind a short runtime, it can be an effective way to turn even indoor light into a figuratively free power source.

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SPINES Design Makes For Modular Energy Harvesting

July 17, 2018 by 7 Comments

The SPINES (Self-Powered IoT Node for Environmental Sensing) Mote is a wireless IoT environmental sensor, but don’t let the neatly packed single PCB fool you into thinking it’s not hackable. [Macro Yau] specifically designed SPINES to be highly modular in order to make designing an energy harvesting sensor node an easier task. The way [Macro] sees it, there are two big hurdles to development: one is the energy harvesting itself, and the other is the software required to manage the use of every precious joule of that harvested energy.

[Macro] designed the single board SPINES Mote in a way that the energy harvesting portion can be used independently, and easily integrated into other designs. In addition, an Arduino library is being developed to make it easy for the power management to be done behind the scenes, allowing a developer to concentrate on the application itself. A solar-powered wireless sensor node is one thing, but helping people get their ideas up and running faster in the process is wonderful to see.

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IoT Solar Pool Heating

July 14, 2018 by 10 Comments

A backyard swimming pool can be a great place to take a refreshing dip on a summer’s day. It can also be a place to freeze your giblets off if the sun has been hiding for even a few hours. That can make pools an iffy proposition unless they’re heated, and that starts to get really expensive in terms of upfront costs and ongoing charges for fuel or power. Unless you put the sun and the IoT to work for pool-heating needs.

Preferences vary, of course, but [Martin Harizanov] and his family clearly like their swims on the warm side. With nobody using the pool when it was below 25°C (77°F), [Martin] picked up a few bits to harness the sun to warm the water. Loops of PVC lawn irrigation tubing were tossed onto a shed roof with a favorable solar aspect and connected to the pool with a length of garden hose. The black thin-wall tubing is perfect for capturing the sun’s energy, and 200 meters of the stuff can really heat things up fast. A small pump is controlled by a microcontroller — it’s not explicitly stated but we suspect it’s a Raspberry Pi — with a pair of temperature sensors to sample the water in the pool and in the heating loop. Metrics are gathered and logged by Emoncms, an open source energy monitoring app. [Martin] says he’s harvesting about 10 kW from the sun on a good day, and that the pool water in the heating loop has gotten up to a steamy 55°C (131°F) without any other energy inputs other than the pump.

Plenty of others have made the leap to solar for pool season extension, with designs from the simple to the more complex. And if you live where the sun doesn’t shine, there’s always a compost water heater.

Open Hardware Takes Charge In Papua New Guinea

July 10, 2018 by 29 Comments

You probably don’t think much about charging your phone. Just find an outlet, plug it in, and wait a while. Can’t find a cable or wall wart? A rainbow of cheap, candy-colored options awaits you down at the brightly-lit corner drugstore.

This scenario couldn’t be further from reality in third world countries like Papua New Guinea, where people living in remote jungles have cell phone coverage, but have to charge their phones by hooking them up directly to cheap solar panels and old car batteries.

[Marius Taciuc] wants to change all of that. At the suggestion of his friend [Brian], he designed an intermediary device that takes any input and converts it to clean 5 volts with a low-cost, reliable buck converter. The inputs are a pair of alligator clips, so they can be connected to car battery terminals, bare-wire solar panel leads, or 9V connectors.

Mobile phones mean so much to the people of Papua New Guinea. They’re like a first-world care package of news, medical advice, and education. At night, they become simple, valuable lanterns. But these dirty charging hacks often lead to house fires. Someone will leave their phone to charge in the morning when they go off to hunt, and come home to a pile of ashes.

This is an open, simple device that could ultimately save someone’s life, and it’s exactly the type of project we’re looking for. [Marius] hopes to see these all over eBay someday, and so do we. Charge past the break to see [Marius] discuss the Brian Box and the people he’s trying to help.

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