Ways to deaden high frequesncy pitch of 100 kW solar inverter

Maria Sanders · June 2013

Hello,

I'm a solar beginner that has been charged with installing several large solar systems in an urban infill environment. We just completed installing a 124 kW solar carport system in a narrow parking lot. Now that the project is up and running, the solar inverter (an AE 100kW) makes a high pitched whistling noise that has caused some complaints from several neighbors in the neighboring apartment complex. The inverter is about 80 feet across the parking lot from the nearest neighbor. The neighbor that is complaining is on the 3rd floor, so it seems the noise is carrying upwards. There is plenty of other ambient mechanical noise in the area, so I suspect it is the high frequency part of the noise that is causing the problem, not the constant mechanical hum.

Short of completely ripping out the current inverter or redesigning the system, is there any way we can dampen the noise, especially the high frequency? Is there a noise cancelling technology or fencing option that has worked well for others.

I have a hard time believing that this issue has not come up for other large urban solar projects.

Thank your, Maria

niel · June 2013

Re: Ways to deaden high frequesncy pitch of 100 kW solar inverter

if it is going across 80ft and up roughly 30-40ft then it really isn't going straight up. maybe the answer is to put a box arrangement around it and extending above it to actually make it go more straight up. it is easier to direct higher frequencies than lower ones and i don't think you can change the pitch. try using cardboard first before anything fancy as it is cheap and may indicate if it will work. if my suggestion fails then contact the inverter manufacturer for possible answers.

PNjunction · June 2013

Re: Ways to deaden high frequesncy pitch of 100 kW solar inverter

Is it possible to just put up a barrier / baffle to deflect the sound? You may also want to look into Sonex acoustical foam on a baffle, although I'm not sure how they hold up outdoors. Perhaps an enclosure with proper ventilation lined with Sonex foam? They make exterior wall and fence sound absorbing systems / blankets so maybe that would hold up better.

Cariboocoot · June 2013

Re: Ways to deaden high frequesncy pitch of 100 kW solar inverter

Dreadful cynic that I am; has anyone confirmed that this noise actually exists, and that it is coming from the inverter? If you can hear it 80' away on the third floor it ought to be screaming loud at the inverter itself.
That would be the first thing I'd check up on. People being how they are it is possible someone saw the array go up and started complaining without cause.

solarix · June 2013

Re: Ways to deaden high frequesncy pitch of 100 kW solar inverter

Talk to the inverter manufacturer. High pitched noise can be difficult to eliminate, so some sort of cabinet around the inverter may be needed.
Consider yourself fortunate that the residents are not suing you for some sort of imagined health detriments due to this "evil" electrical "energy". Around here, you wouldn't believe how many new age types are up in arms over "smart" meters - not only invading their privacy, but actually harming them due to "radiation".

BB. · June 2013

Re: Ways to deaden high frequesncy pitch of 100 kW solar inverter

One acoustic engineer I read about years ago--There was a substation or something similar that generated enough sound to bother one or two neighbors... Engineer did lots of work which reduce sound some--Still complaints.

As a last resort, planted trees and the "noise went away!". However, the secret was the sound pressure measurements showed exactly the same amount of noise before the trees and after the trees.

So--possibly human engineering (trees/make look pretty) may do more than actual noise reduction measures to reduce complaints.

-Bill

mike95490 · June 2013

Re: Ways to deaden high frequesncy pitch of 100 kW solar inverter

You may need a teenager or audio spectrum analyzer to locate the source. Older ears can't hear the high frequencies as well.

I guess these are the transformerless inverters ?

Does the noise continue at night too ?

ggunn · June 2013

Re: Ways to deaden high frequesncy pitch of 100 kW solar inverter

Maria Sanders wrote: »

Is there a noise cancelling technology...

In a word, no. In general, noise canceling works at the point of reception, not at the source.

inetdog · June 2013

Re: Ways to deaden high frequesncy pitch of 100 kW solar inverter

ggunn wrote: »

In a word, no. In general, noise canceling works at the point of reception, not at the source.

Not completely true. They make noise cancelers for jackhammers at construction sites now. It just takes a lot more power to get cancellation at the source. But either source or reception end noise cancellation will not work as well at higher frequencies because the phase of the noise will vary rapidly with position. If the size of the inverter is large compared to the wavelength of the high pitched noise, then it would be much harder to cancel it at the source. You could get cancellation in one direction, but not another for example.

ggunn · June 2013

Re: Ways to deaden high frequesncy pitch of 100 kW solar inverter

inetdog wrote: »

Not completely true. They make noise cancelers for jackhammers at construction sites now. It just takes a lot more power to get cancellation at the source. But either source or reception end noise cancellation will not work as well at higher frequencies because the phase of the noise will vary rapidly with position. If the size of the inverter is large compared to the wavelength of the high pitched noise, then it would be much harder to cancel it at the source. You could get cancellation in one direction, but not another for example.

Yes, I know; that's why I said "in general". If the sound source is a point source and the noise canceling comes from a different point displaced by a distance that is a significant portion of the wavelength of the sound that is desired to be canceled, then it won't work at a distance, or at least it will be directionally dependent. In some directions it would actually make it worse because you'd get constructive instead of destructive interference. If the sound source is large and the frequency is high, fuhgeddaboudit.

Maria Sanders · June 2013

Re: Ways to deaden high frequesncy pitch of 100 kW solar inverter

Thank you, All, for your suggestions? We were planning on building an enclosure around the inverter for security reasons, but on your suggestions will work to modify the enclosure to add some sort of sound barrier system. Here's what the manufacturer suggested:

"The low level, high frequency noise mentioned below is typical of central inverters. Screening or erecting barriers will lessen the issue. Noise from the inverter can be screened using a sound dampening barrier. Although I am not an expert in acoustics, we do have the following recommendations:
-The barrier should be at least as high as the inverter and should aim to break the “line of sight.”
-It should be continuous (non-perforated, uninterrupted) to prevent the transmission of sound through or beneath the barrier.
-The wall should have a minimum surface weight of 4 to 5 pounds per square foot.
-Sound can travel up and over a barrier. As you move away from the barrier and outside of the “sound shadow”, more noise may be heard.
-Specially designed sound panels, fencing, and barriers can be obtained from companies like Industrial Acoustics Company (http://www.industrialacoustics.com/) or Kinetics Noise Control

Enclosing the inverter as mentioned below may work as well. You will need to ensure there is sufficient ventilation.'

niel · July 2013

Re: Ways to deaden high frequesncy pitch of 100 kW solar inverter

it really does not need to have the top on it as long as it doesn't need it to prevent the electronics from getting wet that is. sound wise the top can be open. i would recommend going up higher than the top of the inverter at least by the distance from the inverter to the barrier to help prevent it from being reflected by the back side of the fence to the buildings. in other words if it is 4ft x 4ft that puts the inverter 2ft away from the barrier and should extend up above the highest point of the inverter by at least that same 2ft. it can go higher if you wish as this is my minimum recomendation.

Ways to deaden high frequesncy pitch of 100 kW solar inverter

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