How to check a PV system with your smartphone

[Armand]

Hi,
I stumbled across this Android app:

https://play.google.com/store/apps/details?id=com.optivelox.solartester

is there someone who has already tried it?

[russ]

All in all it seems rather misleading - the one thing it may be able to do with the additional sensor is

• Help in getting a risk-free tan or planning sun-safe outdoor activities

[inetdog]

Has anyone actually found a price for the optical sensor? Or a place to order it from?

[russ]

That possibly allows you to check the level of insolation with your smart phone plus additional sensor - it will tell you nothing about your PV system.

[Armand]

That possibly allows you to check the level of insolation with your smart phone plus additional sensor - it will tell you nothing about your PV system.

I've just tried the app in demo mode (I don't have the add-on sensor SS02); you have to enter the nominal power and the expected overall efficency of the PV system, then place the phone coplanar with the PV modules and the app will show the value of the power (expressed in kW) that the system is expected to generate at the given insolation. By comparing that value with the power shown by the inverter display you can quickly determine if the system is over or under performing.

Has anyone actually found a price for the optical sensor? Or a place to order it from?

I'll try to go deeper and then I'll let you know.

[russ]

I've just tried the app in demo mode (I don't have the add-on sensor SS02); you have to enter the nominal power and the expected overall efficency of the PV system, then place the phone coplanar with the PV modules and the app will show the value of the power (expressed in kW) that the system is expected to generate at the given insolation. By comparing that value with the power shown by the inverter display you can quickly determine if the system is over or under performing.

I am trying to understand the benefit of this? With the additional sensor you learn the insolation of your system then by using fudge factors etc you can compare apricots to apples.

Many weather stations have a pyranometer - far easier.

[J.P.M.]

I am trying to understand the benefit of this? With the additional sensor you learn the insolation of your system then by using fudge factors etc you can compare apricots to apples.

Many weather stations have a pyranometer - far easier.

And a lot more accurate provided you know how the diff. between global horizontal radiation and solar radiation in the plane of the array.

[Armand]

I am trying to understand the benefit of this? With the additional sensor you learn the insolation of your system then by using fudge factors etc you can compare apricots to apples.

Many weather stations have a pyranometer - far easier.

Ok, maybe an example will help you understand better.

Let's suppose you have a 3 kWp PV system and you are considering to check its performance because you want to be sure that all components are working well.

So, the first thing you can check is the value of the power fed into the grid by reading the inverter display (Pgrid).

Let's assume Pgrid= 2 kW. Is your sistem ok? Of course you can't answer this question because you don't know the real value of the solar radiation hitting the PV arrays (Ir). But if somehow this radiation was measured you could estimate:

P = (Ir * Pnom * Oe)/1000

where Oe is the overall efficiency assumed for the system.
For example with Ir=800W/m2 and Oe=0.85 you get P=2.04kW.

Now you can compare P with Pgrid and have an idea about how well your system runs. We are not talking here about apricots or apples but just kW

Do you believe Oe is a fudge factor? No problem, use Oe=1.0 and then estimate the ratio P/Pgrid, this will give you the current overall efficiency of your system.

Finally, do you like to buy a weather station, set its pyranometer coplanar with the PV array and then manually calculate P? Of course you can, but I really doubt that this would be far easier than just placing a smartphone near a PV module and reading the P value directly from its screen...

[J.P.M.]

Ok, maybe an example will help you understand better.

Let's suppose you have a 3 kWp PV system and you are considering to check its performance because you want to be sure that all components are working well.

So, the first thing you can check is the value of the power fed into the grid by reading the inverter display (Pgrid).

Let's assume Pgrid= 2 kW. Is your sistem ok? Of course you can't answer this question because you don't know the real value of the solar radiation hitting the PV arrays (Ir). But if somehow this radiation was measured you could estimate:

P = (Ir * Pnom * Oe)/1000

where Oe is the overall efficiency assumed for the system.
For example with Ir=800W/m2 and Oe=0.85 you get P=2.04kW.

Now you can compare P with Pgrid and have an idea about how well your system runs. We are not talking here about apricots or apples but just kW

Do you believe Oe is a fudge factor? No problem, use Oe=1.0 and then estimate the ratio P/Pgrid, this will give you the current overall efficiency of your system.

Finally, do you like to buy a weather station, set its pyranometer coplanar with the PV array and then manually calculate P? Of course you can, but I really doubt that this would be far easier than just placing a smartphone near a PV module and reading the P value directly from its screen...

And doing that (Putting the weather station/sensor in the plane of the array) would lead to incorrect insolation readings. However, given the other methodology induced gross inaccuracies built in to you method, it probably doesn't matter all that much.

[russ]

And doing that (Putting the weather station/sensor in the plane of the array) would lead to incorrect insolation readings. However, given the other methodology induced gross inaccuracies built in to you method, it probably doesn't matter all that much.

Sorry Armand but the smart phone app is basically useless and not with bothering with - especially when you have to buy the sensor.

[Armand]

And doing that (Putting the weather station/sensor in the plane of the array) would lead to incorrect insolation readings

Please J.P.M. could you give me some additional detail on the errors to which you are referring? As far as I know, this method is also suggested by the guidelines of international standard IEC 61724.

Sorry Armand but the smart phone app is basically useless and not with bothering with - especially when you have to buy the sensor.

Russ, I've just found the sensor is currently offered on eBay, however, before to give it a try I will think over your suggestions. Thank you.

[russ]

Please J.P.M. could you give me some additional detail on the errors to which you are referring? As far as I know, this method is also suggested by the guidelines of international standard IEC 61724.

I wonder what the interest is - Armand wrote the app possibly?

[J.P.M.]

[QUOTE=Armand;112780]Please J.P.M. could you give me some additional detail on the errors to which you are referring? As far as I know, this method is also suggested by the guidelines of international standard IEC 61724.

For my part of the response, the short answer is no. The slightly longer answer is that you need to have some knowledge of solar irradiance before you can understand information on induced errors. Once you obtain that information you will have answered your own questions. See recent prior threads I've posted on the subject for a surface scratch.