Wind and Solar Project

Hi,

I’m George. With Simon’s BatteryMonitor code, I’m finally able to save historical data and plot graphs! This helps paint a much clearer picture about what’s actually going on with my small wind and solar project.

I purchased a home in a rural area of the central US. I’ve wanted to build my own alternative energy system for years after living in other areas of the country where solar energy is very popular. However, since central US can have a thick overcast for much of the year, I felt it might be good to offset that with a couple small wind turbines/generators. Normally when we have cloudy days it can be stormy which equals wind across the rolling hills of farmland. So my project has been slowly underway now for a little over a year. Outside of my day job, when I have the time, this is when I make small adjustments and improvements when I have the extra money to add a component or better cables/connectors, etc. Perfect hobby project. But the project has been on hold now for several months. I am not an electrical engineer and I have no ‘real’ experience in this area other than small solar projects. My background is more related to technical support and network engineering currently and satellite communications years ago in the military. Some telephony and electronics experience but very basic. Thanks to Simon's nice schematics and detail I was able to create the circuits needed. Some trial and error of course on my end.

It was obvious, going into this project that before I would ‘get too far’, and invest a ‘bunch of money’, I would ABSOLUTELY need a small computer to record historical data. Without historical data, you really have no idea what the system is actually doing. Even if you are standing in front of it with a multimeter you are really only seeing one measurement point at any given time, like a big ‘black box’. Sure you can put multiple digital meters on all your measurement points but most of those don’t save data in a way you can plot it on a graph. One guy told me in a blog, “What I did was put digital meters on the points and then I have a camera watching them so I can go back and view what it’s doing.” That’s not data the data I want!!

There are systems you can probably buy that would do a lot of fancy things for me but I’m on a budget. Also, it’s just too much fun to pass up a project like this! After some research on the small computer options out there, like the well-known and documented RPi and Arduino, I decided on the Beaglebone Black. This one came with built-in WIFI and USB so perfect for mounting on my wall next to all inputs and outputs to and from the battery bank. The Beaglebone is powered by the battery bank using a 5V 1A voltage regulator.

Simon’s code has been absolutely perfect for my application. With a few tweaks here and there to adjust for my needs, I now have historical data in a readable format.

Here are some sample graphs of this data.

Both graphs are on the same timeline, about 1.5hrs and plotting in realtime from the data on the Beaglebone SD card. The top graph shows input in current (Amps) from wind and solar. Solar is yellow, wind is blue. I only have a couple of 100W solar panels so far so it doesn’t look too impressive now. As you can see the input from my two small wind turbines is quite active. Reaching into the 40 to 60A ranges today. The bottom graph is the voltage of the battery bank which is comprised of eight deep-cycle marine batteries in parallel (12V bank). In the graph you can see the voltage reaches full at around 13.8VDC, then the solar charge controller dumps the battery voltage till they are around 12.8VDC. On a windy day like this it is reaching full and dumping about every 12 to 15min. I plan to split the wind generators onto separate monitoring points and also add current monitoring points for my load which is an inverter to power an electric water heater (preheater to my main water heater). Another load in the future will be for off grid power (long term goal).

So now that I’ve explained a little about how I’m using Simon’s code, I’ll go into the adjustments we’ve made to taylor it to my needs. Simon wrote the code for his BatteryMonitor project, which is very cool indeed. He’s logging the voltage of individual cells and battery SOC of two points.

This is an evolving update so until I can outline the changes in detail, review our closed 'Issues' about the problems I ran into and how they were solved.