I appreciate the statistics - including the formatted table, which I plan to shamelessly steal from you to add to my own collection of useless energy facts - but I question the HORIZONTAL orientation. Why would it not be angled at the latitude value? You have a number for solar angle loss, that probably includes the average of 13.4% loss from this avoidable pointing error.
My solar water heating panels are appropriately angled - it is a trivial task, and allows rain to wash the dust off, as well.
You are more than welcome to "shamelessly steal" that table! But first, let me repost it (in the post immediately following this one) with the table notes appended to the bottom, that I had left off for the sake of simplicity. They contain some good additional information and links that you may want.
• "but I question the HORIZONTAL orientation. Why would it not be angled at the latitude value?"
I have a couple of explanations for you, plus a real-world example.
First, the sun light arriving at the PV array is a combination of both direct and indirect radiation. Indirect sun light (or blue-sky radiation) is that light that was diffused and scattered by various atmospheric effects. While the intensity of blue-sky light is very small, nevertheless, the blue-sky contains over 100,000 times the angular area of the sun, so even that small intensity adds up to be a substantial level of flux. The actual amounts of direct and indirect solar flux reaching the earth's surface varies depending on which expert you care to cite, but it is generally accepted to be somewhere in the neighborhood of 25% direct radiation from the sun while another 25% would be indirect radiation.
This means that as you tilt your array towards the sun to increase the direct solar irradiance, you are, at the same time, decreasing (to some degree) the irradiance from the indirect solar radiation.
Second, since the vast majority of solar installations are rooftop installations, you not only have to take into account the tilt provided by the roof, but also its east/west orientation. Since the sunny side of the "average roof" will face about 45º either side of due south, this can negate much of the benefit of tilting the array.
As interesting as the numbers in my table may be, and as informative as the above explanations may also be, what can you expect from a system in the real world?
Shell Solar offered a peak at real-world performance in their document: "Solar Electric System Case Study". This document reports on the performance of a roof top residential installation in sunny Southern California. The array consists of 32 Shell Solar SP75 solar panels.
The report states that the total projected system electrical energy output per year is 3650 kWh. Using the data from the Shell report and the spec sheet for the SP75, the average power production is 20.6 W/m^2. A comparison between that value, and the nearly identical value of 20.3 W/m^2 quoted in line 6 of the table in post #104, suggests that the table data is a highly accurate real-world representation of what one can expect from solar power.
--Boot Hill
| ref. | source | loss (%) |
power (per m2) |
|---|---|---|---|
| Solar flux |
|
1,368 W | |
| Atmospheric losses |
|
752 W | |
|
|
Night times losses |
|
376 W |
| Solar angle losses |
|
188 W | |
| Cell conversion losses |
|
22.6 W | |
| DC®AC inverter losses |
|
20.3 W | |
|
|
Net efficiency |
|
1.5% |
|
|
Net energy (per m2 per day) |
|
0.5 kWh |
| Value of energy (per m2 per day) |
|
4.3 ¢ | |
| Solar panel cost (per m2) |
|
$530 | |
|
|
Payback period |
|
33 years |
|
--Boot Hill
