Hello All!

I bought my first 45 watt kit about 5 weeks ago and am looking to buy 1 or 2 more. I am interested in finding plans to build a tracker of some sorts to make better use of the sun by having the panels face it as long as possible while it is up! :)

Has anyone already started a discussion on this topic that I just haven't found and if now I'd like to start one?

Tags: panels, solar, tracker

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Yes but the only viable cheap way, I can figure is using an Old Satellite dish system with actuators

Then having the sensor circuit ....Unless I can get 2 cordless drills, and use long Threaded Bolts.

Slow the the drills, and use sensors,..That what I call inventive.

Dale, that sounds like it could work, I'll bet there are a 100 ways to do it depending on what resources are available.

I just need to figure out which one works for me I guess!

Thank you Dale.

The 2 cordless drill with long threaded bolts, like you can get at lowes that are 3 feet long.

Sounds like a viable idea. Just incorporating it with a controller and adjusting it would be the fun part.

Controlling the drills would be simple...Just use 12 volt cordless drills. I feel they are powerful enough

to torque on some long fine threaded bolt. Just have to keep it greased up good.

It make for a very interesting project. I think I will save up some money for this.

 

 

Hey Steve,

I've been thinking the same thing, but this is simple and will greatly affect your efficiency. It's just pointing it South and adjusting the degree of tilt with the seasons.one for winter (steep), one for both spring and fall, and one for summer (flattest).

It's not what you were asking for but I hope it might help.

Later,

Curtis

 

38. Optimum Orientation of Solar Panels


To get the most from solar panels, you need to point them in the direction that captures the most sun. But there are a number of variables in figuring out the best direction. This page is designed to help you find the best placement for your solar panels in your situation.

This advice applies to any type of panel that gets energy from the sun; photovoltaic, solar hot water, etc. We assume that the panel is fixed, or has a tilt that can be adjusted seasonally. (Panels that track the movement of the sun throughout the day can receive 10% (in winter) to 40% (in summer) more energy than fixed panels. This page doesn't discuss tracking panels.)

Solar panels should always face true south. (If you are in the southern hemisphere, they should face north.) The question is, at what angle from horizontal should the panels be tilted? Books and articles on solar energy often give the advice that the tilt should be equal to your latitude, plus 15 degrees in winter, or minus 15 degrees in summer. It turns out that you can do better than this - about 4% better.
Optimum Tilt for Winter
The winter season has the least sun, so you want to make the most of it. To calculate the best angle of tilt in the winter, take your latitude, multiply by 0.9, and add 29 degrees. The result is the angle from the horizontal at which the panel should be tilted. This table gives the angle for some latitudes:
 
Latitude     Angle     % of optimum
25° (Key West, Taipei)     51.5°     85%
30° (Houston, Cairo)     56°     86%
35° (Albuquerque, Tokyo)     60.5°     88%
40° (Denver, Madrid)     65°     89%
45° (Minneapolis, Milano)     69.5°     91%
50° (Winnipeg, Prague)     74°     93%

These angles are about 10° steeper than what is commonly recommended. The reason is that in the winter, most of the solar energy comes at midday, so the panel should be pointed almost directly at the sun at noon.

The third column of the table shows how well this orientation will do compared with the best possible tracker that always keeps the panel pointed directly at the sun.
Other Seasons
If you are going to adjust the tilt of your panels four times a year, the best dates to do it are when the "solar season" changes. The table below gives the dates of each "solar season". (If you are in the southern hemisphere, you need to adjust these dates by half a year.)
 
Winter     October 13 to February 27
Spring     February 27 to April 20
Summer     April 20 to August 22
Autumn     August 22 to October 13
Fixed Tilt
If your need for energy is highest in the winter, or the same throughout the year, you probably want to just leave the tilt at the winter setting. Although you could get more energy during other seasons by adjusting the tilt, you will get enough energy without making any adjustment. The following tables assume that the tilt is set at the winter optimum all year long. They show the amount of insolation (in kWh/m2) on the panel each day, averaged over the season.
 
Latitude 30° Season     Insolation on panel     % of winter insolation
Winter     5.3     100%
Spring, Autumn     5.6     106%
Summer     4.5     85%

 
Latitude 40° Season     Insolation on panel     % of winter insolation
Winter     4.3     100%
Spring, Autumn     5.3     123%
Summer     4.5     105%

 
Latitude 50° Season     Insolation on panel     % of winter insolation
Winter     2.9     100%
Spring, Autumn     4.9     169%
Summer     4.5     155%
Adjusting the Tilt for Other Seasons
Keeping the angle of tilt set for winter may not be best for you. For example, you may need more energy in the summer to pump irrigation water. Or maybe you have a cabin that is not used in the winter.

The optimum angle of tilt for the spring and autumn is the latitude minus 2.5°. The optimum angle for summer is 52.5° less than the winter angle. This table gives some examples:
 
Latitude     Spring/Autumn angle     Insolation on panel     % of optimum     Summer angle     Insolation on panel     % of optimum
25°     22.5     6.5     75%     -1.0     7.3     75%
30°     27.5     6.4     75%     3.5     7.3     74%
35°     32.5     6.2     76%     8     7.3     73%
40°     37.5     6.0     76%     12.5     7.3     72%
45°     42.5     5.8     76%     17.0     7.2     71%
50°     47.5     5.5     76%     21.5     7.1     70%

If you want to adjust the tilt of your panels four times a year, you can use these figures to keep capturing the most energy year-round.

Note that the summer angles are about 12 degrees flatter than is usually recommended. In fact, at 25° latitude in summer, the panel should actually be tilted slightly to the north.

It is interesting to note that all the temperate latitudes bask almost equally in the warmth of summer.

The efficiency of a fixed panel, compared to optimum tracking, is lower in the spring, summer, and autumn than it is in the winter, because in these seasons the sun covers a larger area of the sky, and a fixed panel can't capture as much of it. These are the seasons in which tracking systems give the most benefit.

The following graph shows the effect of adjusting the tilt. The blue line is the amount of solar energy you would get each day if the panel is fixed at the winter angle. The red line shows how much you would get by adjusting the tilt four times a year as described above. For comparison, the green line shows the energy you would get from two-axis tracking, which always points the panel directly at the sun. These figures are calculated for 40° latitude.
Time-of-Use Rates
In some grid-connected systems, energy is more valuable during peak periods. To see the effect of this on panel orientation, look at my time-of-use page .
Assumptions
These calculations are based on an idealized situation. They assume that you have an unobstructed view of the sky, with no trees, hills, clouds, or haze ever blocking the sun.

You may need to make adjustments for your situation. For example, if you have trees to the east but not the west, it may be better for you to aim your solar panels slightly to the west. Or if you often have clouds in the afternoon but not the morning, you might aim your panels slightly to the east.

The calculations also assume that you are near sea level. At high altitude, there is less atmosphere to absorb light, so it is more important to capture sunlight near sunrise and sunset. At high altitude it might be better to lower the angle of tilt a little.
How these numbers were calculated
For each configuration of latitude and season, over 12,000 data points were calculated for various times throughout the day and the year. For each data point, the equations of celestial mechanics were used to determine the height and azimuth of the sun. The intensity of the sun was corrected to account for the increased absorption by the atmosphere when the sun is lower in the sky, using the formula:

intensity in kw/m2 = 1.35 * (1.00/1.35) sec(angle of sun from zenith)

These factors, and the angle of the sun with respect to the panel, then determine the insolation on the panel. An iterative method then determined the angles that give the maximum total insolation during each season. Given those angles, the beginning and ending dates of the season were then adjusted to the optimum, then the angles recalculated, until the process converged. After the optimum dates and angles were calculated, it was determined that a linear formula approximates the optimum closely.

Other published articles on tilt angles have used less accurate calculations. For example, Richard Perez and Sam Coleman, in "PV Module Angles", Home Power n.34 p.14-16, 1993 , recommend an angle that puts the panel perpendicular to the sun's rays at noon. That is indeed the best angle at noon on that day, but it does not take into account the best angle for capturing solar energy at other times of the day. That article also leaves it to the reader to estimate the best angle over the period until the next time the tilt is adjusted.

Percentages may not be exact due to rounding.
Links
Here is a link you may find useful.

http://www.nrel.gov/rredc/solar_resource.html
    The National Renewable Energy Laboratory has copious data on solar energy available at different locations in the United States, a performance calculator for PV systems, and more.  

 


Thanks for posting Curtis. The "noon" thing makes perfect sense.

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