Are You Down With MPPT? (Yeah, You Know Me.)

Solar cells have gotten cheaper and cheaper, and are becoming an economically viable source of renewable energy in many parts of the world. Capturing the optimal amount of energy from a solar panel is a tricky business, however. First there are a raft of physical prerequisites to operating efficiently: the panel needs to be kept clean so the sun can reach the cells, the panel needs to point at the sun, and it’s best if they’re kept from getting too hot.

Along with these physical demands, solar panels are electrically finicky as well. In particular, the amount of power they produce is strongly dependent on the electrical load that they’re presented, and this optimal load varies depending on how much illumination the panel receives. Maximum power-point trackers (MPPT) ideally keep the panel electrically in the zone even as little fluffy clouds roam the skies or the sun sinks in the west. Using MPPT can pull 20-30% more power out of a given cell, and the techniques are eminently hacker-friendly. If you’ve never played around with solar panels before, you should. Read on to see how!

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Maximizing a Solar Panel

Solar panels seem like simple devices: light in and electricity out, right? If you don’t care about efficiency, it might be that simple, but generally you do care about efficiency. If you are, say, charging a battery, you’d like to get every watt out of the panel. The problem is that the battery may not draw all the available current, basically leaving capacity on the table.

The solution is a technique called MPPT (Maximum Power Point Tracking). Despite sounding like a Microsoft presentation add on, MPPT uses a DC to DC converter to present a maximum load to the solar cell while providing the desired current and voltage to the load. MPPT is what [Abid Jamal] implemented to manage his solar charger.

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Hackaday Prize Entry: Arduino MPPT Controller

Imagine you’re building a small solar installation. The naive solution would be grabbing a solar panel from Horror Freight, getting a car battery and AC inverter, and hoping everything works. This is the dumb solution. To get the most out of a solar you need to match the voltage of the solar cell to the voltage of the battery. How do you do that? With [Debasish]’s entry for The Hackaday Prize, an Arduino MPPT Solar Charge Controller.

This Maximum Power Point Tracker uses a buck converter to step down the voltage from the solar cell to the voltage of the battery. It’s extremely efficient and every proper solar installation will need a charge controller that does something similar.

For his MPPT, [Debasish] is using an Arduino Nano for all the math, a DC to DC buck converter, and a few MOSFETs. Extremely simple, but [Debasish] is connecting the entire controller to the Internet with an ESP8266 module. It’s a great example of building something for much less than it would cost to buy the same thing, and a great example for something that has a chance at making the world a little better.

 


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Solar Charge Controller Improves Efficiency of Solar Panels

The simplest and easiest way to charge a battery with a solar panel is to connect the panel directly to the battery. Assuming the panel has a diode to prevent energy from flowing through it from the battery when there’s no sunlight. This is fairly common but not very efficient. [Debasish Dutta] has built a charge controller that addresses the inefficiencies of such a system though, and was able to implement maximum power point tracking using an Arduino.

Maximum power point tracking (MPPT) is a method that uses PWM and a special DC-DC converter to match the impedance of the solar panel to the battery. This means that more energy can be harvested from the panel than would otherwise be available. The circuit is placed in between the panel and the battery and regulates the output voltage of the panel so it matches the voltage on the battery more closely. [Debasish] reports that an efficiency gain of 30-40% can be made with this particular design.

This device has a few bells and whistles as well, including the ability to log data over WiFi, an LCD display to report the status of the panel, battery, and controller, and can charge USB devices. This would be a great addition to any solar installation, especially if you’ve built one into your truck.

This is [Debasish]’s second entry to The Hackaday Prize. We covered his first one a few days ago. That means only one thing: start a project and start documenting it on hackaday.io