collector orientation calculator - ScanTheSun

[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.

[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.

[silversaver]

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

[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

[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

[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.

[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.

[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.

[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.

[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.]

I would respectfully suggest you consider withdrawing this application from public use until you get a better working knowledge of applied solar energy and provide something better.

From what I've seen of it and from what you have written, I'm pretty sure both this attempted application and your working knowledge of applied solar energy are not ready for prime time just yet.

I've seen better undergraduate projects than this. Maybe it has some use as a shading tool, but the rest of what I've seen of it is pretty amateur and borderline nonsense.

I'd never recommend its use in its current form. I suspect others more knowledgeable than I would say the same and have a similar opinion to mine.

Respectfully,

J.P.M.

[sensij]

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

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.

Based on what you've described in this thread, it appears that, at best, you are able to meet item (3) of the stated goals of the software, and maybe a bit of item (2). Items (1) and (4) require the full solution of Eq. 7.1 of your citation, along with supporting data to estimate each of the parameters of that equation. It is seriously misleading to suggest that the software in its current or near-term state could hope to meet either of those goals.

[Ernest_Grodner]

Sensij,
You are right, to get total assessment of usable energy form the cell you need to solve all factors and do parameters measurement for each type of a panel.
No question about that. And this will not be calculated in the app.

Just to clarify what is stated above "The new functionality will be based on angular efficiency of a panel for direct irradiation. ".
Maybe some sentences I wrote are misleading (I'm not a native english speaker). Insolation in my language relates only to beam radiation - and that I have used above.
Do you think I should change
"1)measure the total solar power on your collector." to "1)measure the solar power on your collector from direct irradiation."?
and
"4) Measure the hours of water warming/electric energy generation along the year." to "Timing of beam irradiation"?
to be more precise?


Returning to Lund paper.
The app is intended to find best orientation of the panel. Only first component plays a role as orientation dependent.
I do not see how heat loss or thermal capacitance may strongly depend on collector orientation.

Some of you asked for a comparison of app calculation with , say PVatts.
I have chosen obstructionless environment (that PVatts is only able to calculate online).
I have choosen Egipt location and horizontal panel orientation.
The location is chosen intentionally in order to lower the dependence on weather statistics and increase the relative effect of diffuse irradiation.
kWh per day of solar irradiation are listed starting from January up to December.

ScanTheSun PVatts relative difference
(direct) (direct,diffuse, weather)

3.6 4.43 18%
4.7 5.33 11%
5.9 6.4 7%
7.1 7.31 3%
7.7 7.4 4%
8.0 8.03 0.3%
7.9 7.9 0%
7.4 7.58 2%
6.5 6.8 4%
5.2 5.7 9%
4.0 4.8 16%
3.4 4.16 18%

The relative difference - on the average - on the level of 10%.
Ernest.

[J.P.M.]

Ernest:

I believe your goals are ill defined and poorly explained. Furthermore, your methods are way off base in more ways than this format allows time or space to describe.

1.) The Helgesson paper you reference deals primarily with solar thermal applications and methods to enhance and improve thermal collector performance, mostly by focusing on one type of thermal collector. It treats the analysis of the solar energy resource as a secondary issue necessary for the main topic which seems to be thermal analysis. I would not agree that, to use your words, it is "One of the most informative and openly accessible material..." on the subject.

2.) There is nothing wrong with that paper, which seems to be a dissertation necessary as part of the requirement for recognition and licensure as a Professional Engineer or something similar. In point of fact, it's methods are quite recognizable. I've seen similar and almost identical methods in print and have used similar methods for thermal analysis. The methods are common but they are not the only ones. The point is, what's in that paper regarding the solar resource is not new, and much of the rest of it. while probably accurate (as much as those things can be accurate), seems a reshuffle of existing methods and material, most of which is not new, and certainly not unique, as is common for dissertation topics.

3.) See a copy of Duffie & Beckman, and/or many others - Iqbal, Lunde, Kreith, NREL, The Solar Energy Handbook, etc. and/or, the references in the Helgesson paper itself. Start with Liu and Jordon (1960), to see the origin of the info in the Helgesson paper about not only resource evaluation, but also most of the thermal analysis. Indeed, most of the material you may think makes the Helgesson paper so informative (but IMO, mostly a rehash) was around for a long time before the publication date of the Helgesson paper (2004), as correctly acknowledged by its cited references. As a respectful suggestion - go to the horse's mouth and use the Helgesson cited references as a start.

4.) From the beginning, that you seem to not understand the folly of not including all of the solar radiation components - diffuse and reflected, as well as the direct component, or (as seems possible at this point), to not even be aware those other components exist until challenged (tipped of ?), or that those components may be important in varying degrees based on the situation, and expect to be taken seriously, particularly when methods are commonly available to evaluate the solar resource, causes me to doubt that you do have the necessary depth of the subject to claim the necessary expertize.

5.) FWIW, depending on the application and in spite of what you may think or not see, collector orientation can and does affect heat loss and (possibly to a much lower degree) thermal capacitance, and, FWIW, many other things in any solar conversion device. That effect is usually most pronounced for thermal devices, but also for PV and other applications as well. I and many others think we know that, and some of us think we know why, when, where, how, or not, in what ways and to what degree, at least to a 1st approximation collector orientation affects things that in turn, affect collector performance.

That you acknowledge you do not believe device orientation affects such things as heat loss and thermal capacitance (again, perhaps to some small degree, depending on application), only gives me more reason to think you may lack the knowledge depth of applied solar energy necessary to expect a reasonably knowledgeable student of the subject to take much of what you present seriously.

6.) Much of what you seem to be attempting has been done before. You seem to be trying to reinvent the wheel. Looks to me like some of the dimensions on your new wheel come out of the imaginary plane.

I believe you are out of your knowledge depth for what you are trying to do with respect to applied solar energy. The shading portion of your application may have some merit. I'm of the opinion that most of the rest of what you claim and provide is simplistic, incorrect in both approach and execution, and therefore prone to error. In its current form, and in my opinion, your application will not find what is likely the best collector orientation with a reasonable probability of success or accuracy. That the comparison and agreement in output between PVWatts and your app that you present seems to be quite seasonally dependent would be a red flag to me. Try comparing your app to SAM or TRNSYS and see what you get. My suspicion is you'll find those two produce results a lot closer to PVWatts than your app.

Respectfully,

J.P.M.

[Ernest_Grodner]

Dear Friends,

I'm happy to announce that the project ScanTheSun was chosen by the jury as Energy Globe National Award winner this year. On June 5 (World Environmental Day) all National Winners will be published at www.energyglobe.info.
I would like to thank all of you for the feedback that allowed decent debugging of the ScanTheSun code and make important changes and corrections.
There are also press releases of the recent year available at:

http://scanthesun.com/papers/sts2.php?langmain=EN

With best regards,
Ernest.