Solar Freaks

Ben came over last night after the races and we spent a few hours putting together a lightmeter for the NSW event. We required an averaging lightmeter due to the inconsistent light conditions.

The meter uses the same lightmeter software in the Nanometer. You may use any panel as the reference. So long as you know the I(sc) of that panel at full sun, you may calibrate the lightmeter.

The light meter was calibrated using a module i received from Ian Gardner, which has a known Isc of 663mA at full sun.

Here is a video of how it works. As can bee seen, it uses a remote panel on a pod. Displays average, and current light levels. The average can be reset at any time.



Pictures Below:

Tony,

Do all the Nanometer units have this averaging ability? Or is this something only your one possesses at the moment?

Also, what's the sample rate?

Marc

Your unit also has this ability. The software on yours was updated a couple months ago.
All you need to do is add a remote solar panel. You can use any panel with an Isc between 400mA and 800mA.

It might sound overkill, but the sample rate is 1000S/s.

The readings are:
Sunlight: xxx% Instananeous Sunlight.
Average: xxx% Average Sunlight.

The Sunlight reading changes instantly with the light level with no delay.
The Average is the sum of all the readings / number of readings.

Oh good. I'll certainly be using it for our state event then. Ian also sent me an Engelec module with a known Isc at full sun.

1000S/s does sound a bit extreme but I don't mind. I would have been more than happy with just a few samples per second.

Great.

If you have Nanometer Firmware v3.2 it will have the feature.
Firmware v3.1 had a lightmeter but didn't have averaging. Just double check.
It tells you the version on startup.

Whats wrong with 1000S/s . The more the merrier .

Marc have you experimented with the light meter yet?
If so, what are your thoughts?

No, not quite yet. I'll definitely be looking at it soon though since I will be setting it up for the Tas event.

I have however checked to see what Firmware version it is and it appears to be v3.2.

Talking about Sunlight Meters, I reckon the one we have over here is collaborated differently. It never seems to go past 100%. Well that's from my memory. Were talking about Perth here. I swear at the past 2 nationals that sunlight never was as intense as W.A. (could be wrong) and the readings were over 100%.

Anyone know the sunlight meter that we use over here?

jhg wrote:Talking about Sunlight Meters, I reckon the one we have over here is collaborated differently. It never seems to go past 100%. Well that's from my memory. Were talking about Perth here. I swear at the past 2 nationals that sunlight never was as intense as W.A. (could be wrong) and the readings were over 100%.

Jun,

It is quite possible that the meters are calibrated slightly differently. The meter/s used at the last few national events all base 100% on full Melbourne sun at mid-day in mid-summer. To maintain some consistency I will arrange to have a module measured and then sent over to you. You can then compare this with the meter used at the WA event.

The higher than 100% sunlight readings that have been present in the last couple of years are likely to be due to clouds concentrating the light. On a cloudless day, the meter shouldn't really exceed 100%.

Marc

The comments about light meters reading over 100% needs some clarifying.

There has been a lot of talk lately when it comes to solar panel measuring about using 100% sun at AM1.5 but there has not been any talk about what AM1.5 means.

AM stands for air mass, quite literally how much air the light has to pass through between the sun and the panel. The various molecules and particles in the air block some of the suns radiation. In outer space obviously there is no air (or very little) so that is AM0. Twice a year, at midday, at the equinox (no, not mid summer) and at the Equator the sun would be directly overhead and therefore the light will have to pass through the minimum air mass to reach the surface and this is AM1. This also assumes the air to be clean, no smoke or dust, and a certain relative humidity. If the sun is at a more oblique angle it will have to pass through more of the atmosphere. So, at any other time, at any other location and under any other conditions, the light will have to pass through more air mass and be reduced in intensity. In order to average things out and to make solar panel performance a bit more 'real world' the figure of AM1.5 is adopted when rating panels.

It is, therefore, quite possible and indeed very likely, that a reading of over 100% can be recorded at many locations and times.

Hobart is 42 degrees south but the Earth is titled 22 degrees (from memory) so in mid summer the sun is only 20 degrees off directly overhead. This does not constitute a great deal of extra air mass, especially when you add in the fact that Hobart air is exceptionally clean and also very dry. (If you don't believe me about the dry bit, go look it up). This is why visitors to Tasmania get a shock when the discover the power of the sun here, usually by getting badly sunburnt! And it means that we can record over 100% Sun. My 1kW rooftop panels regularly exceed 1100W in summer even without being aimed properly.

Perth is a long way further north and also gets lots of nice clean air blown in off the Indian Ocean so summertime readings over 100% should be easy to achieve.

Sydney and Melbourne, on the other hand, despite being further north than Hobart, both have filthy air for most of the time so achieving even AM1.5 is possibly difficult. (Anyone who has flown into Melbourne will have seen the disgusting brown cloud that hangs over it for most of the time.)

Then, as Marc has pointed out, a few clouds in an otherwise 'clear' sky can add to the directly incident radiation by reflecting additional light onto the panel.

On the other hand, don't get confused into thinking that just because it is a hot day the light level must be high. High levels of dust and water vapour not only reduce the incident radiation but also prevent the heat caused by that radiation from being re-radiated so everything heats up. And you cannot trust your eyes. The brain has a fantastic automatic gain control so a wide range of light levels looks the same to us. Add in some glare from reflected light travelling horizontally and what looks like a bright day isn't necessarily.

I don't think we will be considering 1.5AM over here for our States.

Anyway I was just wondering if the nanometer is connected to the timing instruments? Or is the USB port on the nanometer connected to the computer, where the timing instruments is also connected to the same computer? Or is it manual since their buttons on nanometer. It's a stupid question but I can't really tell. I'm assuming/ hoping its works together?

The Nanometer runs 100% free of the timing equipment.

In that particular video the USB port was just used to power the unit. Normally it runs using batteries.
The USB port is used for transferring the panels I/V curve to the computer using the PC software I've designed it to interface with. It'll Give you data like this:



It also logs the light level for the day (SW v3.3) in 30s to 5min increments and can send the data to the PC in excel format, so you can view the sun level for the entire day in a sunlight/time curve.

Anyways when you use it in WA, all you will need to use on it is the 'Light Meter'.
You can have a play around with the I/V Curve Sweeper as well and test out a few panels if you like.
It'll give you their FF and all the other data too.

jhg wrote:I don't think we will be considering 1.5AM over here for our States.

I think you will be. Ian Gardner sent over the Victorian Master panel to WA late last year or early this year to get it specially calibrated at AM 1.5 at one of the Unis.

That makes sense to me now. They were talking about a calibrated modules or something. I brought the topic of air mass up but they didn't really response much to it. Since a Curtin uni professor is handling the light box this year he may have made modification to the light box or program used. F.A. was surprised that our light box could be tuned to 50%, so was I; since we all thought it was fixed at 100%.

So at the NSW event did you reset the nanometer and then started it when the gate was opened? Was the percentage recorded after the second car went through? I noticed that the sunlight % didnt change in the results so that's what I have been lead to believe. Is it better to measure the sunlight percentage when each car passes the finishing line or is too hard? Anyway our time trails are singular so there's no issue. But I'm interested in your reasoning behind which method is the best. I have my own opinions but don't know if its right.

The light percentages were recorded as soon as the first car finished the race.
You may also record the light percentage for both cars separately, but i don't think its worth the effort.

The top button seen in the picture resets the average.
You need to record the average before you reset it.
I thought about putting in a split feature, but it'll make things too complicated.

TonyB wrote:The light percentages were recorded as soon as the first car finished the race.
You may also record the light percentage for both cars separately, but i don't think its worth the effort.

Agreed. In most races, cars don't finish too far apart from one another. Other than for seeding, only the car that finishes first and is of major interest.

Marc

Thanks guys!

Out of curiosity, I was just wondering what sunlight measuring device was used at last years nationals. Because I heard that at our state event last year, that the time device was connected to the sunlight meter. Apparently all the data was entered automatically into the computer. Or is this another lie?

jhg wrote:Out of curiosity, I was just wondering what sunlight measuring device was used at last years nationals. Because I heard that at our state event last year, that the time device was connected to the sunlight meter. Apparently all the data was entered automatically into the computer. Or is this another lie?

For the past couple of nationals Ian Gardner's light meter has been used. This consists of two 1.5V Dicksmith modules connected in parallel and then taped off to produce 1A at 100% sunlight (approx. AM 1.1). This is set up in combination with a Fluke multimeter which allows current measurements (sunlight %) to be averaged over the course of a race. This meter is also reasonably consistent with what was used before then.

I wouldn't know, but it is quite possible that WA might have the timing and sunlight meter all connected together with the data then automatically entered into the computer.
If this is the case, then does the sunlight meter have averaging? If not, I would suggest using the Nanometer. The Nanometer will also come with a calibrated cell and so be sure to compare it with the WA meter to see how consistent they are.

Marc

Apparently last year for our states, we used everything that came across with the national track. So that's why I was curious about why we would be manually recording the sunlight percentage with the nanometer this year. I have no idea what happened last year at the states but I would believe that the meter that was used was not as high tech as the nanometer. But I'm pretty should it would have done averaging if it recorded the sunlight when the timing devices were activated... Who knows!

If you were using everything that came across with the track last year then race times were not entered automatically into a computer but instead done manually. Whoever told you otherwise must have been mistaken since the timing gear is linked up to a box with an LCD which is separate from any computer.

The sunlights may have been automatic if WA was using it's own meter, but I somehow doubt it. As for the averaging, I also doubt that the WA meter did that.

Marc