collector orientation calculator - ScanTheSun

[Ernest_Grodner]

Dear J.P.M.

Thak you for critical approach to ScanTheSun that will allow to develop the app further in a way future possible users are mostly interested.

Please remember, the app is a new and fresh approach an does not include all processes yet.
First thing we are concentrating is a proper treatment of a beam irradiation (the direct one) and related output power based on IAM factors.
Direct radiation is a main component for power prodution in most PV and thermal collectors. This will be done in the nearest update of the app.

Diffuse radiation is not included now.

The diffuse radiantion is a "second order approxipation". The works on diffuse irradiation have been suspended due to the mentioned polarization effects that are most alarming for a physicist.
However, your criticism is a motivation to contact other group and discuss how to include these phenomena and make a diffuse light evaluation available maybe in future update of the app.
I see this problem is important for you and other usres.

One of the most informative and openly accessible material on how to treat different factors for output power assesment You can find on the web is from Lund University:

http://www.ebd.lth.se/fileadmin/energi_byggnadsdesign/images/Publikationer/Bok_EBD-T-04_1_web_Anna_H.pdf

Please take special care on equation 7.1. The only component sensitive to panel angle (theta) is the first one and relates to beam (direct) irradiation.
Since ScanTheSun aims to help in proper panel orientation - only the beam irradiation component will be included (basing on IAM data) in the the next release of the app in Spring this year.

The app goes different way of development then the software you have mentioned, therefore it is hard to compare each other.
ScanTheSun tries to make use of detector equipment that everybody has at home in form of mobilephone sensors (just not to buy expensive equipment for quick and simple insolation assesment).
When some of you need a detailed assesment of a commercial use of solar setup - it is better to sinvest and buy a dedicated measuring equipment or software.
In contrast to the software you mentioned, this app is not designed for stationary computers but ruther to popular devices equipped with sesnoring hardware.

Regards,
Ernest.

[J.P.M.]

Dear J.P.M.
Thank you for your comments and questions. I would like to answer some of them if I may?
1) Various types of covers or glazings, device characteristics (direct irradiation).
The IAM - Incidence Angle Modifier - is a measured efficiency (actually relative efficiency) of a solar cell at STC conditions. Glazings and covers parameters are included in IAM just by the way how the IAM measurement is done. Since IAM is measured (by certificating institution) there is no need to calculate it in the app.
2) Diffiuse radiation and reflections.
There are Fresnel formulae stating that light reflection produces (partly) polarized reflected beam. Similar process takes place for photon scatering (constituing the diffuse light). There is no (I have seen no) certificate, or measurement that presents how a solar element reacts to polarized light and changes of the polarization plane or polarization helicity. Therefore diffuse light is not included in the app until there are no technical data in certificates related to polarized irradiation.

Regards,
Ernest.

Ernest:

Most respectfully:

I'm back to my original comments. What you have done appears to me like it might be a half way decent shading calculator. As far as much of the rest of what I've been able to follow, I have serious doubts about the methodology or the accuracy, or even what your method is attempting to provide.

Maybe that's just my ignorance showing. To repeat, maybe I'm wrong, but there seems to be a lot of missing pieces to the puzzle of what you are attempting. I have a smattering of knowledge of solar radiation, how it reacts with and is changed as it passes through the atmosphere under different atmospheric conditions as f(wavelength), and the effect of various atmospheric constituents, water vapor, mixed gasses, dust, ozone, etc., as well as how various glazing materials attenuate/change/scatter solar radiation, also as f(wavelength, angle of incidence, glazing material, other). Can you point me in a direction where I can understand how your method(s) treat those and other factors ?

Besides a shading estimate, are you providing estimates of Plane of Array (P.O.A) insolation ? Are you providing estimates of system output ? In sum: What is the actual output you are providing ? If you are providing estimates of a system's output, perhaps if you could provide some comparison to estimates of output of a system using your method against other, established methods that have attained some measure of credibility, such as SAM or PVWatts under unobstructed conditions, I (at least), and perhaps others would be able to make valid comparisons and perhaps offer some valuable comment.

Related to Sensij's post about diffuse irradiance - If you are only taking direct beam irradiance into account as is (also) my take on your method - that is, ignoring the other components of solar radiation, you're leaving a lot out. If you are ignoring the other components, that raises serious doubts in my mind and opinion about what you are actually trying to accomplish and more importantly, your depth and knowledge of the subject of applied solar energy.

Again, Respectfully,

J.P.M.

[sensij]

With regard to diffuse irradiation... imagine that you have a perfect tracking sunshade that is sized to the same 0.5 deg of sky as the sun. It blocks the direct light from the sun's disc to the solar element, but no other light. Would the algorithm return zero solar production in this case? If so, it is not accounting for the diffuse radiation in the sky, or reflections from the ground.

[Ernest_Grodner]

J.P.M. answers

Dear J.P.M.
Thank you for your comments and questions. I would like to answer some of them if I may?
1) Various types of covers or glazings, device characteristics (direct irradiation).
The IAM - Incidence Angle Modifier - is a measured efficiency (actually relative efficiency) of a solar cell at STC conditions. Glazings and covers parameters are included in IAM just by the way how the IAM measurement is done. Since IAM is measured (by certificating institution) there is no need to calculate it in the app.
2) Diffiuse radiation and reflections.
There are Fresnel formulae stating that light reflection produces (partly) polarized reflected beam. Similar process takes place for photon scatering (constituing the diffuse light). There is no (I have seen no) certificate, or measurement that presents how a solar element reacts to polarized light and changes of the polarization plane or polarization helicity. Therefore diffuse light is not included in the app until there are no technical data in certificates related to polarized irradiation.

Regards,
Ernest.

[J.P.M.]

It looks to me that this is an application to calculate potential shading for a stationary (non tracking) solar application.

So, for shading estimates, it looks like it has potential.

I'll admit some ignorance here. Maybe I'm missing something but I don't see any information about how this application handles diffuse radiation, reflected radiation or transmission characteristics of those various types of insolation through various types of covers or glazings, or a lot of other information, such as solar device characteristics.

I also wonder if the author has seen all the NREL stuff like SAM, etc. which seems to already do a lot of the stuff implied here and much more.

Also, it looks to me that there is no treatment of non clear days, or just what constitutes a clear day.

I believe there is a lot more to calculating the solar potential of a site than a shading calculation. If shading estimates are all this application does, it looks like it may fit the bill, but my reading of the website and u-tube stuff gives me the feeling that a lot of necessary stuff is being left out. The website, to me at least, implies more completeness than is actually delivered, and a lot less than necessary for what is implied as output.

[russ]

Hi Ernst - Looks good so far. We don't usually allow such links but yours does seem to be for the members good so OK.

Russ

[Ernest_Grodner]

Initiative for support of solar panels users

Dear Forum users,
Thank you for worm words and opinions about the app.
This motivated me to prepare an action aimed at getting the best
of our solar panels and to get closer to energetic independence based on renewables.

ScanTheSun is starting an initiative for support of solar panels users
in getting the highest efficiency of installed devices.

Presently, with ScanTheSun it is possible to calculate the insolation of the place where a solar element will be installed
taking into account various factors like shading by surrounding buildings or trees.

The measured insolation is an amount of solar power that will incide on the panels.

How much of that solar power will be transformed into usable energy is an another important aspect
which depends on the type of the used solar element and its efficiency characteristics.
For instance a tubular collector catches sunlight in a quite different way then a flat PV-panel.
This difference is reflected by so called IAM factors (being just an efficiency functions of incidence angle).
The efficiency data are accessible in almost all PV-panels or thermal-collectors certificates.

In Spring (March 2015) an upgrade of ScanTheSun is planned for enabling on-site output power assessment
of solar installations that will take into account the IAM data.
The new functionality will be based on angular efficiency of a panel for direct irradiation.
This way all users will have an occasion to choose a panel type/model that may best fit to specific on-site conditions.

I'd like to invite you to take part in the initiative.

The only thing to get it working is to upload efficiency data of solar panel you are interested in.

For this purpose I've prepared a website:

http://www.scanthesun.com/panels.php

where technical data of solar elements may be uploaded.

I've also prepared an introduction video about the initiative http://youtu.be/MeSimI3HL-A :

with best wishes for 2015
Ernest

[silversaver]

I haven't had chance to watch all the videos, but they seem informative. Thanks!!

[Ernest_Grodner]

compass calibration

Hi, I got first feedback form the users of ScanTheSun.

Mostly it relates to issues with tracking the Sun.
Some devices require compass calibration. I have prepared an instructive video on
why and how the compass should be calibrated to get proper tracking.

http://www.youtube.com/watch?v=c82AW2BKF-Q

I hope it will help you in insolation and shading analysis.

[Ernest_Grodner]

Hi,
my name is Ernest Grodner and I'm physicist at the University of Warsaw.
Since more than one year I'm in the possession of solar panels installed on my home.
My home is surrounded by trees and I wanted to know what is the insolation of my panels considering all possible shade.
I have used my knowledge and wrote a free app for handsets and tablets that calculates this.


The app calls ScanTheSun
with which you can

1)measure the total solar power on your collector
2)measure the solar energy loss in the shade
3)measure the best collectors orientation considering surrounding obstacles like trees and buildings.
4)Measure the hours of water warming/electric energy generation along the year

Example of such documentation can be found here:

http://www.scanthesun.com/applications/detached_house.php?lan=EN

If you are about the solar collectors installation you can find the best part of the roof and discuss the results with your local experts.


If you already have solar cells then you can ask the technician for the documentation (1,2,3,4) or prepare it yourself.

Videos of the ScanTheSun usage are here:
Raw video:

https://www.youtube.com/watch?v=GHKAhpQv1Vs

Video with additional presentation:

https://www.youtube.com/watch?v=m6BIzAaE09s

Id like to contribute to our better future too, therefore I decided to make the app available for free.
You can install it from Google Play

https://play.google.com/store/apps/details?id=com.scanthesun&hl=en

I hope the app will be helpful to some of you in getting the solar power efficiently.
With best regards,
Ernest Grodner.