Monday, July 14, 2008

My Renewable Energy Projects, an Update

Solar Water Heater:

My solar swimming pool water heating project is still a work in progress. I now circulate water through 200 feet of pvc tubing mounted in the attic of my storage shed. I pump cool water from the pool, circulate it through the pvc heat exchanger, and return the heated water back into the pool.

The system heats the water nicely, but I seem to have too much pool for the small amount of hot water I’m producing. I’m using an ordinary garden hose for the water input, and it has a tendency to collapse under the vacuum that the pump creates. This restriction lowers the output of the system. I may put this project on hold, since heating the pool water is not necessary this time of year. I suppose I'll work on it again this fall, or next spring.

Home Heating with Corn:

My corn stove saw limited use last winter due to the high cost of corn. Corn was about $2.50 per bushel when I installed the stove, but it’s currently about $7.00 per bushel. The sharp increase was due to the huge demand for corn by the ethanol industry. I expect the cost of corn to decline as cellulosic ethanol plants come on line, and I’ll once again be able to economically use the stove.

If the price of corn remains high, I might try growing it myself (again). I've recently purchased my first piece of equipment to help with the process, an old corn sheller. I found the sheller at an antique store. This should be well worth the 20 dollars I paid for it.

My PV System Automation and Battery Charging:

Summer has arrived, and hot weather has resulted in an increased demand for electricity. My utility rate plan has me paying for electricity based on demand, and the rate has exceeded .17 per kwh a few times. However, my nighttime rates have been surprisingly low, sometimes below .01 per kwh. To take advantage of this large discrepancy, I sometimes charge my batteries at night and use the stored energy to run my refrigerator and freezer during the day when utility rates are high. It seems that switching to a variable electricity rate plan has paid off, and that my load shifting plan is working. Here are some statistics:

My cost for the electricity I used in June of 2008 was $65.38.
My cost for the electricity I used in June of 2007 was $116.31.

I used 625kwh of electricity in June of 2008.
I used 1127kwh of electricity in June of 2007.

Other PV System Statistics:

I currently have 5 – 85 watt PV panels on my roof. I’ve not yet adjusted the angle for the summer sun, so they’re not pointed at an optimal angle. I waited a little too long to do this, and now I want to avoid walking on the roof while the shingles are hot. Later this year I’ll add another PV panel, and I’ll adjust the angle at that time.

In addition to the inefficiency caused by a less-than-ideal angle, I’ve noticed the effect of temperature on the PV panels. I seldom see PV panel current exceed 22 amps. I’ve seen panel current exceed 25 amps during cold weather.

System output averages a little more than 2kwh per day, or about 10% of my total household usage, but that is with a boost from the battery charger. I’m pretty happy with this free, and low-cost, electricity.


Some say that unless utility rates are exceptionally high, and renewable energy incentives are exceptionally good, the payback for a solar PV system might be in excess of 25 years. But for those of us who do most of the labor ourselves, and explore ways to improve efficiency, payback can be much quicker. At the same time we benefit from a system that shelters us from utility failures. We can stay comfortably in our homes at a time when others need to abandon theirs. We can keep our refrigerators and freezers running, protecting our food from spoiling. We can keep our communications and entertainment equipment working, and protect our property and belongings. I don’t dwell on the payback period. My system has already paid for itself as far as I’m concerned. My systems can keep me comfortable in my home regardless of outside weather, or disruptions of any of my utilities. My systems are far from complete, but are improving with time. In the not-to-distant future I’ll be able to cut my transportation expenses thanks to my PV system. Perhaps one of these days I’ll be able to pull the plug on all outside services.


1 comment:

AnnyPan said...

John, your blog is pretty amazing! And your "sustainable-living project" too. I just took a small look about it, but I have your blog in my bookmarks and I'll return on it soon. I'm personally and professionally interested in CFL and LEDs, I'd love to discuss about that with you if possible. Ciao! Agnese