Happy Solstice

happy-solticeThe long days of summer are here and solar production is at its peak for Cincinnati. We have plenty of sunshine here in the summer, but many people ask us if we get enough sun during the rest of the year to make solar projects feasible? The answer is, absolutely!  With thousands of solar power systems installed in southwest Ohio, there is no doubt solar works here.  The table below shows the percent of our annual sunshine we receive each month of the year.

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total
5% 6% 8% 10% 11% 11% 11% 11% 10% 8% 5% 4% 100%

Obviously our best sun conditions occur from March thru October, but even those cloudy months of winter provide some good solar days.

The sun’s angle above the horizon peaks on June 20, the summer solstice, and reaches its minimum angle on December 20, the winter solstice.

How does this play into the best orientation of solar panels?  Ideally when the sun is perpendicular to the surface of solar panels, the panels receive optimum sun and thus produce optimum power.  So to maximize production at the summer solstice, we tilt our solar panels at 26 degrees so the panel is at a right angle to the sun (26 + 74 = 90 degrees).  This would make production optimum for one day of the year, and suboptimum for the rest of the year.

But solar is forgiving and solar power systems which don’t have optimal siting still produce lots of solar power! There is a large “solar sweet spot” such that, even if the tilt and orientation of the panels towards south is not perfect, we take a relatively small performance hit.

What happens in practice is typically one of three things:

  1. We mount the solar panels flush with the roof of the home.
  2. We mount the solar panels on a fixed tilt mounting system on the ground.
  3. We mount the solar panels on a variable tilt mounting system.

In the end, if the modules do not face true south and are not tilted at just the right angle, solar still works and we still produce power.

Let’s discuss the three options above.

Option 1

We mount the solar panels flush with the roof of the home. This configuration provides the best aesthetics and lowest installed cost for most residential systems.  Typical roof angles are 18 – 45 degrees in the Cincinnati area, the most common being 18 – 26.6.  The systems perform well and the neighbors don’t think a space ship has landed on your roof.

Option 2

We mount the solar panels on a fixed tilt mounting system on the ground. This approach is often taken when there is available ground real estate and building roof structure or orientation is not conducive to a solar installation.  Here is a  solar carport constructed for a client in Cincinnati. The home has a large south facing roof, but it is encumbered by a large dormer and two large chimneys.  The carport array tilts at 15 degrees as a trade off to maximize solar production and minimize wind loading on the structure.  The array is producing 100% of the electrical needs of the home. At this  local farm we had plenty of real estate and freedom to line up the array to face true south with a tilt of 30 degrees (optimum for Cincinnati).  In general, ground mounted structures will be more expensive than roof mounted systems due to the cost of building the mounting system.

Option 3

We mount the solar panels on a variable tilt mounting system. This allows the tilt angle of the modules to be adjusted (typically monthly) to follow the sun’s seasonal elevation changes.  This approach adds some cost due to the increased complexity of the structure, but the benefits are many. It is easy to mow and trim around the structure, solar production is maximized, and less real estate is needed for the array. SunRock Solar installed a  seasonally adjustable pole mounted array in Reading, Ohio. This site is interesting as it has some late afternoon shade so the array was oriented to face slightly south east rather than true south.  This actually improved the system performance by approximately 5% over a true south facing array.

To wrap up, there are many factors which contribute to the performance and aesthetics of solar power systems.  Each situation is different. By taking the time to analyze and discuss options with its customers, SunRock Solar can deliver a power system which melds aesthetic and performance expectations, with the reality of site conditions. Solar works well in Cincinnati!

Interview with SunRock Customer

toyota-prius-with-solar-systemHarvey P. of Yellow Springs Ohio hired SunRock Solar to install a photovoltaic array in his backyard using a seasonally adjustable pole mount system. The installation was completed on May 3, 2011, so the system has been in production for about a year.  We interviewed Harvey about his panels and the pole mount system.

How big is your system?

Fifteen 230-watt modules for a system rating of 3.45 kW.

What percentage of your utility is being covered? How much have your utility bills gone down?

I am covering 100% of usage, but we were not big users. Our electric bill is now $10.00 per month, covering the first 100 kWh, which I never use.

Now that it has been running for awhile, have you figured out how long it will take to pay it off?

Very uncertain, as it depends on electricity rates, SREC values, and the value of my power uses (e.g. the use of solar to power my plug-in Prius displaces gasoline charges)

How many SRECs have you produced?

Slightly less than 4 MWh at this point.

You decided to use a pole mount system. Why didn’t you put the panels on your roof?

More shading from neighbors trees than was the case with the pole mount.

Why didn’t you use a regular ground mount system?

I wanted the option of “following” the sun during the seasons, and also the pole mount left more gardening space than a ground mount would have.

Do you think the pole mount system has helped your production?

Yes, based on a comparison with a roof-mount array located nearby. The steep winter tilt also helps prevent snow build up on the panels.

Are you satisfied with the production? Yes.

Is the tilt mechanism easy to adjust?  Yes, very easy.

How often do you need to adjust it?

I usually change the setting twice a month, and sometimes more often if I am showing the installation to someone.

Have any issues or problems developed?  No.

Have you had any major storms hit your area? Hail, or high winds?

There has been some small hail and fairly high winds.  The hail caused no visible damage and the wind caused the array to shake a bit, but not enough to cause worry or damage.

Are you satisfied with the work that was performed?  Very much.

What other things do you do at your house to reduce your energy costs?

We have new appliances, all energy star, and most of our lighting is with CFLs.  We are replacing our windows to decrease air conditioning load, the only possible use that would exceed our production enough to use our “banked” production.

Are the panels producing enough energy to handle your house and charge up your electric car?

We have a plug-in Prius, and easily have the capacity to cover it.  (about 4 kWh for a full charge.  It is not used every day.)

Do you monitor your usage more now that you have panels installed? Has it made you more aware of what you are using?

No, I have kept a spreadsheet of usage for several years.  But I do enjoy following the solar production using the online monitoring.

Are you glad that you had solar panels installed at your house?

Yes, indeed.

Installation of Solar Panels Using a Pole Mount System

solar-panel-on-pole-of-mount-systemSunRock Solar has started using pole mounts to install photovoltaic systems for some of our customers.  Pole mounts are a valid option when there is a small amount of roof space to install an adequate number of panels, the roof line is east/west, or there is too much shading to justify an installation.  The poles consist of a single pole with a crossbar where the solar panels are mounted.   There are two different sizes of poles that can hold either ten or fifteen panels each.  Because everything is mounted on a single pole, the footprint of each pole is minimal.

We buy the mounting system from a company called True South.  The company is located in Ohio and the poles are also manufactured here.

Another feature of these poles is that each pole has a hand crank, at the ground level, that can tilt the panels.  In this way, the panels can be adjusted to give an ideal tilt for each month of the year.

To see pictures of the installation of a pole mount system in our gallery, click here.