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We started a pole-mount PV project yesterday. We had to dig two holes to eight feet, install sonotubes, install the poles, and get ready for the cement to arrive, all before 2:00 pm. Because of the location of the poles and the ground conditions around the owner’s house, we could not drive a cement truck to the pole locations, and as a result, we hired a cement pumping company. They arrived with one of those trucks with a long, extendable boom that would reach to where the poles were located.

Once all the equipment was in place, we started the pour. Two holes took less than 10 minutes to fill with cement. We spent the next two hours cleaning up and moving pipe and hoses. But we got the job done, and are ready for the next stage of the project – getting the actual PV modules installed.

I spent the morning yesterday swapping out my batteries – all 16 of them. While this may not seem like a big deal, you have to consider that each battery weighs 121 pounds, and I had to move 32 batteries (the 16 old ones out, and the 16 new ones in). In addition to the pain in the back, I was without power for a couple of hours.

Why did I have to go through this? The old batteries failed after only 12 months, and were not able to provide the amount of power they were supposed to. When we first got the batteries, we were able to go a day or two with no sun recharging them. At the end, we could not even go overnight without the generator kicking on. A battery bank with a capacity of 180 amp-hours (20 percent of the rated 20-hour capacity of the batteries) could not even give us 50 amp-hours.

I was alerted to a potential problem when I measured the specific gravity of the electrolyte in the batteries. A healthy fully-charged battery will have a specific gravity of around 1.265 to 1.275. Some of ours had specific gravity measurements between 1.300 and 1.315. When the acid is this strong, it starts to eat away at the positive plates, resulting in lower storage capacity.

Fortunately for us, our supplier recognized this as a manufacturing issue and replaced the battery bank free of charge. In talking to our supplier, I learn a lot about batteries and how to treat them. Lead-acid batteries do not like to run out of liquid, nor can they be drained too low for extended periods of time. This will dramatically shorten the life of batteries. For the most part, however, lead-acid battery technology is very robust and forgiving, but once in a while you run in to an issue that is not related to owner treatment. In these cases, it is good to have a supplier you trust and that has the experience to know when a battery has failed as a result of a manufacturing defect.

How are your batteries doing?

For those of you that live in Vermont and purchase your power from Central Vermont Public Service Corporation (CVPS), you are eligible for an additional credit for power you generate with solar renewable energy. CVPS has recently started a Gross Solar Generation Credit program, where they will give you a credit of $0.06 per kilowatt-hour for energy you generate, regardless of who uses it. This program requires installation of a second electrical meter (currently $60 for the meter, plus the cost of installation of the meter socket by a qualified electrician) that measures the amount of power generated by your PV system before the power goes to your service panel.

If you have a 2,000 watt (2 kW) PV system, in a typical year, you generate about 2300 kW hours per year. With this program, you would get a credit of around $138 in the first year. The electrician we work with, Paul Judd of Charlestown, NH, can install a meter socket for around $150 to $200, depending on site conditions, leaving a total cost for this meter of around $260 or less. With these costs, the payback for this program is less than two years. After this, the credit makes your investment in PV increase with every sunny day.

Please let us know if we can help you with this or any other renewable energy issue. We look forward to hearing from you.

Did any of you with PV systems note generation of any extra power yesterday? With the cold weather, PV modules make extra power. This is one reason considering cold weather extremes during the design of a PV system is so important, as the voltage of the system can increase significantly during cold snaps, sometimes over the rated maximum voltage of charge controllers or inverters. This condition can be bad, either causing a system to shut down, or smoke. The good news is, if properly designed, you can make more power on cold days than during warmer weather. Call us if you’d like more information about making your own power from the sun.

As we start a new year, we look back on 2011 and marvel at the many new friends we made, people that we had the opportunity to interact with and assist with meeting their energy goals. We are truly blessed to have had these opportunities, and are grateful for the confidence that was placed on us to complete many renewable energy projects.

We are looking forward to 2012 and the potential it holds for making more renewable energy. If you are considering a renewable energy project for 2012, now is the time to start planning. There are changes coming related to incentives that are available, and there could be delays in project approvals from the state. So give us a call and let us know how we can help! We look forward to serving you in the new year.