One Step Closer to Solar Electric Panels
The good folks at SIREN gave a stirring presentation last month about how now is the time to switch to solar electricity. Panel prices have fallen significantly due to the recession, electricity prices look poised to raise (at least here in Indiana where Duke Energy is spending several billion dollars to construct a coal gasification plant in Edwardsport and pass costs on to customers), and there’s a brisk market for renewable energy credits. We had already caught the fever a bit and the talk just convinced us it was time to get an actual site assessment and cost estimate.
We’re working with Alex Jarvis of Solar Systems of Indiana, a quirky guy who knows a heck of a lot about solar. He came out to discuss some different options and to do a site reading of a few potential spots using his handy dandy Solar Pathfinder. It’s a very simple little device that maps shade to determine if a particular spot has a good solar window. The image above is from the middle of our roof, which has a very good solar window of about 85% between the key sunshine hours of 9:00AM and 3:00PM – solar time. (See rant on Daylight Savings Time below.)
He also measured a few other spots in our yard so we could think about doing a pole-mounted solar panel. You could argue that the pole-mounted systems are a little on the ugly side but they are very practical in terms of maintenance – no climbing on the roof, no trying to patch the roof under the solar panels – and they are great for houses that have a shaded roof but sunny yard. We are leaning in that direction simply because our roof is 20 years old and will need to be replaced well before the solar panels. Alex actually has his panel (shown at right) configured so he can move it around during the day to maximize its exposure to direct sunlight and therefore maximize electrical generation. He is the first to admit that is way too hardcore for most people but he is a tinkerer and enjoys fiddling. Most people just retilt their panels twice a year at each solstice. At the spring solstice, the panel is tilted closer to horizontal since the sun is higher in the sky during the summer. At the fall solstice, the panel is tilted more vertical since the sun is low in the sky during the winter.
After that is the decision of what kind of solar panels and inverters to get, which I must confess is mostly Greek to me but Will is drooling a bit at the thought of enphase microinverters that broadcast all kinds of exciting data for him to analyze with a fine-toothed comb. We’re looking at getting six modules that are each rated somewhere around 240 watts, giving us a system that is around 1.44 kilowatts. Here in southern Indiana, we average about 4.7 hours of direct sunlight per day once you factor in cloudy days and the fact that our days are significantly longer in the summer but shorter in the winter. In a perfect world, our solar panels would produce 6.8 kw-hr per day (1.44 kw x 4.7 hours) or 2,470 kw-hr per year. However, there are some losses that we have to take into account with our lovely fudge factor friend, the derate factor. The derate factor has several components:
- Shade on our system. Our solar window is about 85% open, 15% shade.
- Losses from the inverter, connections, and wiring
- Losses from dirty solar panels (we’re going to assume we can keep ours clean – with a hose if needed)
- Losses from improper angling (again, we’re in good shape with a pole-mounted system that can be tilted at least twice a year)
In the end, we figure our derate factor is about 0.8 (meaning we lose about 20% of the ideal production level), which reduces our expected output to about 5.4 kw-hr per day or 1,970 kw-hr/year. That should still just about cover our needs and in our area it’s not worth overproducing since the electric company will just keep rolling over our credits until we move. If you’d like to try this game at home, check out the PV Watts calculator developed by the National Renewable Energy Lab. Soon we should have some prices to go along with our power estimates but for now we’re excited about the possibilities and also trying to brainstorm how we might landscape our yard to make the solar panels blend in a bit. Any and all suggestions are welcome!
Daylight Savings Time Rant: Indiana only recently adopted Daylight Savings Time while staying in the Eastern Time Zone, and I am not a fan. Today the sunrise was at 6:30AM and sunset at 9:15PM, which means our solar noon is really about 1:50PM and our key sunshine hours are 10:50 to 4:50. It also means that the fireflies don’t come out until 10:00 and it’s awfully hard to schedule fireworks, bonfires, or drive-in movies that children (or I) can stay awake for. I liked it better when we were in straight-up Eastern Standard Time and never had to worry about changing our clocks.
Even with our reduced electrical usage, installing enough solar panels to meet our average needs just isn’t cost-effective for us yet. Photovoltaic (PV) prices have dropped a lot in recent years so even though we can’t afford a big system, there are a couple of cheaper options for trying out solar energy on a small scale.
This whole
So we signed up for the SIREN Energy Challenge and have been trying to figure out where we use electricity and how we can cut back, which means Will is running around using his Killowatt on everything. At the same time, I am planning my garden for spring and also thinking about how we will take advantage of the summer bounty. My dad helped me set up a seed starting system with three shelves of fluorescent lights and I’m trying to talk Will into getting a chest freezer so we can store the summer’s vegetables but all he can think about is the increased electrical consumption.
Well, approximately one year after we purchased an
Next came the fun but mildly intimidating step of drilling a hole in the roof! We rented a “Sawzall” reciprocating saw for the job since it didn’t seem like a piece of equipment we really needed to own. I am mildly afraid of heights but I do love power tools so I had a good time cutting out a big chunk o’ roof. Happily, the solar tube is designed in a way that the hole does not need to be perfectly circular (it wasn’t) since it comes with a rubber “boot” that fits over the hole, under the neighboring shingles. Once we had the hole cut, we pried up the shingles around it, put some roof sealant on the rubber boot, and slid it into place.
Somehow we didn’t get any pictures of us sliding the actual metal tube into place, probably because I kept blinding Will with it. The solar tube is comprised of two very shiny metal tubes and a clear plastic dome. Sun shines down on the dome and then bounces down through the tubes to our kitchen, where a frosted plastic light fixture lets the light shine through without blinding anyone.
So, back up to the roof to remove the dome, swap the tubes, then Will stayed on the roof while I went into the attic and it was much easier to get the tubes together. He pulled the top tube up while I put the correct bottom tube into place in the ceiling fixture, and then he pushed the top tube down, helping me wrestle the two tubes together and then tape them with the shiny metal tape enclosed in our original kit. Whew! I totally used some muscles I didn’t know I had but I would willingly do it again and I know it would go faster the second time.


You know those little projects that you never seem to get around to? Well, our new house came with a security light over the garage that stays on 24 hours a day. Neither of us have ever really been into security lighting, especially the kind that illuminates the back deck, calls in flying insects from nearby counties, and shines brightly in through our windows. There’s also the fact that it drains electricity 24 hours a day, which seems rather wasteful. However, this light didn’t come with a light switch so we had trouble figuring out how to turn it off.
We checked our electric meter after turning the circuit breaker back on and it appears to be spinning at a much slower rate. Woo hoo! Victory! We’re not sure exactly what wattage the bulb was but based on some other on-line security light figures it could easily be as high as 200 Watts. With 24-hour usage, that adds up to 6 kWh per day, almost as much as we used