Solar Power Data logger

[Hawi]

I'd like to purchase a hand-held (battery powered) solar power meter. Does anyone have a model they can recommend. Hoping to keep it under $300.

[J.P.M.]

Can you be a bit more specific ? What do you want to measure ?

[Hawi]

I'd like to measure the solar radiation in watts/m^2 . So far, this is the closest product that seems like it would work.

https://www.aliexpress.com/item/TES-132-Handheld-Solar-Power-Meter-Tester-400-1Knm-Range-2000W-m2-634Btu-ft2-h-Data/32724724317.html?spm=2114.40010408.3.5.cMOrFH

My goal is to compare a calibrated meter against my neighbors weather station. He's been recording on weather underground for the last year and I'd like to rely on his data to estimate some typical and worst case conditions. If I can rely on his data then it should help me with my system design.

[J.P.M.]

I'd like to measure the solar radiation in watts/m^2 . So far, this is the closest product that seems like it would work.

https://www.aliexpress.com/item/TES-...408.3.5.cMOrFH

My goal is to compare a calibrated meter against my neighbors weather station. He's been recording on weather underground for the last year and I'd like to rely on his data to estimate some typical and worst case conditions. If I can rely on his data then it should help me with my system design.

Understood. You won't get a calibrated meter for anywhere near that price. If you think you are, or are told that, someone is lying to you. You might get one measured against a secondary standard when built, and that's probably good enough.

A suggestion: Check out something called PVWatts on the net, particularly the help screes. It uses the data from the TMY files from NREL to model PV array performance. The data is easier to use and will probably give reasonable results that will be quite sufficient for what sounds like your needs. In spite of what you may think, one year's data is probably not as representative as what you can get from PVWatts. Read the help/info screens and you'll know why.

Still, to discuss what you plan:

Your neighbor probably has a Davis Pro II + weather station. I also have one. The pyranometer data from the Davis, like most any other irradiance data, including that of much the more sophisticated and expensive equipment such as that from Eppley is about +/- 5% or so. Most all hand held meters also have about the same 5% accuracy. That means you'll probably get #'s for horizontal irradiance close to the Davis that's at your neighbor's house, but probably not much better than the 5 %. Using two pyranometers is a bit like having two watches - you never know which one is more accurate.

FWIW, you can get a Davis instrument with all the bells/whistles/data logging for ~ $900 -$1,000 on line. That's sure a lot more than $300, and this is not a plug, but you get a lot for your money.

Also, if you're neighbor's instrument is wireless and you're within 800 -1000 ft. or so of your neighbor's instrument with a clear line of sight , for ~ $100 + or so you can get your own receiver from Davis and, with your neighbor's knowledge and permission, use the data from that station. For ~ $150 more you can get a data logger/computer interface. See the Davis website.

BTW, unless your neighbor has his instrument calibration checked, it's prudent to assume a couple %/yr. drift in the irradiance data after the first year or so. Last time I checked, recalibrations are $60 U.S. from Davis.

If I was you, knowing what I think I know, if I wasn't going to see what I could get in the way of numbers from PVWatts, I'd use your neighbor's data for the global horizontal irradiance (G.H.I.) and then do a spreadsheet following information in Chap. 1 & 2 of Duffie & Beckman: "Solar Engineering of Thermal Processes" to transpose the G.H.I. to something called plane of array (P.O.A.) irradiance for what you plan for an array orientation. It's basically a number crunch. I've found that using the HDKR logic in Duffie & Beckman to be about the closest match to my actual measurements and seems to give sensible numbers when trying to figure out my array's instantaneous efficiency.

So, with the handheld meter, you'll be able to get P.O.A irradiance but the number you get won't be the same as the Davis and you'll still be doing the number crunch for every daylight hour.

PVWatts is a lot simpler and will probably give better long term estimates for what it sounds like you're looking for.

I know all the modeling and nomenclature may seem like mumbo jumbo, but if you're serious, check out PVWatts first and then read Duffie & Beckman and all will be made clear.

Welcome to the neighborhood and the forum of few(er) illusions..

[bcroe]

Also, if you're neighbor's instrument is wireless and you're within 800 -1000 ft. or so of your neighbor's instrument with a clear line
of sight , for ~ $100 + or so you can get your own receiver from Davis and, with your neighbor's knowledge and permission, use
the data from that station. For ~ $150 more you can get a data logger/computer interface.

I'll just add, with line of sight, and knowing the frequency of transmission, you could probably greatly increase range/signal strength
by adding a proper higher gain receiving antenna. It would be directional, to be aimed at the transmitter. A lot of that is going on here.
Bruce Roe

[Hawi]

Thanks for the reply and tips. Here is the actual weather station model.

http://www.weatherhawk.com/611-series

Here's a link to the weather underground data.

https://www.wunderground.com/personal-weather-station/dashboard?ID=KHIKAPAA7#history

[Hawi]

Thanks for the tips, I will check out PVWatts later today when I get a chance. Regarding the weather station it's a model WeatherHawk 611, which is pretty high-end.

Also, here is a link to the weather station data on weather underground.

https://www.wunderground.com/personal-weather-station/dashboard?ID=KHIKAPAA7#history

[Hawi]

Here's a link to the manufacture page on the station.

http://www.weatherhawk.com/611-series

[J.P.M.]

Here's a link to the manufacture page on the station.

http://www.weatherhawk.com/611-series

Understood. Thanx for the info.

I looked at the Campbell Scientific instruments before I bought the Davis. Nice stuff, but out of my price sensibility and complexity with respect to the other measuring methods used. Additionally, I believe the irradiance sensors are the same as the Davis.