Solar

Data Junkie

I’ve never been really satisfied with knowing that something works. I’ve always wanted to know exactly how well it works. I crave data. I’m a data junkie.

I’ve never been really satisfied with knowing that something works. I’ve always wanted to know exactly how well it works. I crave data. I’m a data junkie. My unending quest for data really began at Portsmouth, New Hampshire, when my high school physics teacher, Mr.Walter Novak, showed me the power of precise measurement. He taught me that if you can accurately measure the performance of a device or system, you can improve it, tweak it, and make it work even better. I was hooked. When I installed our very first PV module, I also installed an instrument panel to go with that single PV. I could easily measure the current produced by the PV and its operating voltage. I took this data hourly for the first few months and wrote it down on a clipboard. I guess I couldn’t really believe that I was making electricity directly from sunlight until I measured it. From this simple one-module system and its instruments, I learned the basics of solar electricity—module orientation to the sunlight, the effect of clouds, and the effect of temperature. If knowledge is power (volts times amps), understanding is like voltage, and data is like amperage. Over the years, Home Power has published many of my data quests. See the PV democracy rack testing in HP24, HP33, and HP49. See also the many Things that Work! reports we’ve generated showing actual data for RE equipment operating in real world conditions. As our system and my quest for knowledge grew, we began to get interested in computerized data acquisition (DAQ). There were simply too many things to measure too often to accomplish this job with a meter and a clipboard. In HP49, we first used a computerized DAQ system to measure performance of the PVs on our democracy rack. While this early DAQ system was crude, it had the advantage of playing directly into our Macintosh computers. Over the last few years, we realized that we had totally outgrown our DAQ system.We now have all sorts of stuff to measure and report on—all the PVs on the democracy rack, inverters, appliances, solar hot water, and solar hydronic heating. I live with all this stuff and I know from direct daily experience that it works, but I won’t be satisfied until I know exactly how well it works and can tweak it into working better. So we’re getting into a new DAQ system, and you’ll be seeing the data it generates in the pages of Home Power. We had to abandon the Macintosh computer platform to get a state-of-the-art DAQ system. Sophisticated DAQ systems and software are simply not optimized for the artistic world of the Mac, but are instead the province of the Windows PC world. When Joe Schwartz and I began dreaming up our new DAQ system two years ago, we figured we could pull it off in a few months for less than US$1,000.We soon realized that we didn’t have the experience to design such a complex system.We sought help from an experienced professional—A. J. Rossman of Draker Solar Design. Without A. J.’s help, we’d still be floundering around in a sea of hardware and software. The final system’s hardware cost, including the laptop, DAQ hardware, and software, came in at US$4,200. Home Power’s new DAQ system consists of a Toshiba Satellite 1800-S207 laptop computer with Windows XP, running National Instruments’ LabVIEW 6.1 software. We’re using a Measurement Computing DAS-16-16AO PCMCIA, 16 bit, multifunction DAQ board with LabVIEW drivers running on the Toshiba. The various measurement points are multiplexed using a Lawson Labs Inc. model 35B, amplified multiplexer and a model 17B multiplexer.We can make rapid measurements in many points of the systems without having to rewire or reconfigure the DAQ system. The Toshiba laptop and its DAQ system will talk to our Mac computers via 100 base T Ethernet, so we can crunch numbers and graph the data on our Macs. This new DAQ system will be able to measure and log PV module current and voltage, solar insolation, PV temperature, battery voltage and current, wind speed, wind generator voltage and current, both inverter input and output current and voltage, solar hot water collector temperatures, solar hot water tank temperatures, hydronic heating collector temperatures, room temperatures, and solar slab temperatures. And that’s just part of what this DAQ six-ring circus will measure and record…. Our first DAQ project using this system will be to do another data run on our aging democracy rack. Only this time, in addition to current versus voltage (IV) curves for all the modules, we will also have data about how much daily energy each module contributed to our system. Although they’re still working fine, most of the PV modules on our democracy rack are no longer available for purchase. After this test on the democracy rack, we’re going to assemble a new democracy rack with the latest models and begin testing them. Expect to see the data generated by our new DAQ system in Home Power next spring. I want to invite all you other data junkies out there to contribute your data and experiments for publication in Home Power. Only by accurate measurement and analysis will we all learn exactly how these RE systems work in a very diverse world. For a data junkie, this is heaven! © 2002 Richard Perez Used with Permission Contact Richard Perez at: [email protected]