Is Solar power dirty? - Page 1
Forum section: electronics / general

author: kastnerd
author_rank: Newbie
timestamp: November 09, 2017, 01:35:16 pm
content: Hi, At my office we on almost done installing Solar. A few electrician iv talked to have mentioned that the power we will be feeding back into the grid would be "dirty power" I looked this up and it looks to be due to the DC to AC conversion and how some Inverters use more of a square wave and other inverters use a pulse width modulation. We are putting in 11 SMA Sunny Boy sb7.7-1sp-us-40 Inverters.Using an oscilloscope is there a good way to see how clean the power is?Thanks.

author: tszaboo
author_rank: Super Contributor
timestamp: November 09, 2017, 01:44:50 pm
content: You asked an electrician about an electronics question.He answered it based on his very limited understanding, and some anecdotes based on different topology inverters.The sunny boy 7.7 has less than 4% Harmonics according to the datasheet. So your power will be maximum 4% "dirty"

author: woody
author_rank: Frequent Contributor
timestamp: November 09, 2017, 01:56:30 pm
content: And anyway, whatever the shape of the sinus coming from the solar inverter, that power is cleaner that anything coming out of a fossil power plant.

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: November 09, 2017, 02:39:23 pm
content: Quote from: woody on November 09, 2017, 01:56:30 pm-Remind me again: Where are solar panels made?

author: woody
author_rank: Frequent Contributor
timestamp: November 09, 2017, 04:18:23 pm
content: I don't have a clue. Germany?On the other hand I do know where virtually all the stuff we happily use on a day to day basis came from: China. And I know something else too. All that shit generated a lot of CO2 being produced for us and shipped to us for peanuts, and keeps generating CO2 while being used. Which cannot be said from solar panels, which produce CO2 free energy long after the first 6 to 12 months the average panel needs to return the energy involved in producing it.Insinuating that solar panels create CO2 is fake news.

author: Mjolinor
author_rank: Frequent Contributor
timestamp: November 09, 2017, 04:26:23 pm
content: I rather think that "dirty" in this case is referring to the quality of the sine wave and is nothing to do with CO2 at all.

author: helius
author_rank: Super Contributor
timestamp: November 09, 2017, 04:33:17 pm
content: Quote from: kastnerd on November 09, 2017, 01:35:16 pmYou can use a DSO with a high-pass filter function. As you adjust the corner frequency up, the amplitude of the signal will decrease, until only the higher harmonics are left. By comparing the amplitude at any given corner frequency with a clean power signal, you can also quantify the low harmonics (which will increase the amplitude).You can also use the FFT function to convert the signal to the frequency domain. Harmonics (or sub-harmonics) will appear off the main power frequency (50 or 60 Hz). However, impulse noise is harder to see on FFT plot compared to the filter approach.

author: Seekonk
author_rank: Super Contributor
timestamp: November 09, 2017, 05:24:13 pm
content: All the office equipment and lighting in your office is probably responsible for more dirty power than these inverters would supply. It is unlikely you will be able to see just how bad the utility power is now that the inverters are installed . Raw power doesn't need to be that clean. That is something marketing people thought up.

author: Mjolinor
author_rank: Frequent Contributor
timestamp: November 09, 2017, 05:58:24 pm
content: As far as I know it is set by law and nothing to do with marketing.

author: kastnerd
author_rank: Newbie
timestamp: November 09, 2017, 09:25:06 pm
content: Quote from: helius on November 09, 2017, 04:33:17 pmThanks, I will try this once I get the ok to Turn the system on.

author: martinator
author_rank: Contributor
timestamp: November 09, 2017, 10:27:36 pm
content: Solar panels don't grow on trees. It takes energy to make a solar panel. Manufacturing solar panels has it's toll on the environment just like anything else. I often wonder if it takes more energy to make a solar panel than it will give out in its lifetime? Think of all the making, eating, pissing, shitting and rooting that's required to just get a panel on the roof, before it's even switched on. We live in a system of diminishing returns. No one ever considers the Total Energy Expenditure.Now where did I put my scrumpy?

author: coppice
author_rank: Super Contributor
timestamp: November 09, 2017, 10:37:00 pm
content: Quote from: martinator on November 09, 2017, 10:27:36 pmLots of people take the total lifecycle energy usage of these products very seriously. The snag is their figures seldom agree very well. Its pretty clear that the energy produced by solar panels exceeds the energy consumed for manufacture, deployment and support, as long as the system is kept deployed for a long time. However, by some measures the ratio might only be a few times as much energy produced. The casual observer, noting that these panels are designed to operate for at least 25 years, might expect a much higher multiple.Everyone lies in the energy business. There's too much money involved for people to stay honest. Take all figures not presented with lots of solid supporting material with a pinch of salt. If there is supporting material, be highly suspicious of it, and probe its origins.That said, I think the original post is actually referring to dirty power as in distorted power waveforms. Most approvable grid tie inverters are required to produce a fairly clean sine wave. It doesn't need to be perfect. The mains power is rarely that clean. Even a simple incandescent lamp causes 10% to 20% THD in its current waveform, due to the rapid heating and cooling of the filament through each half-cycle of the mains.

author: tszaboo
author_rank: Super Contributor
timestamp: November 10, 2017, 10:17:17 am
content: Quote from: martinator on November 09, 2017, 10:27:36 pmIn that case, it would never pay for itself. Simple as that. If it takes more energy to manufacture it, then the energy cost would make it so expensive, that it is not worth buying it.

author: glarsson
author_rank: Frequent Contributor
timestamp: November 10, 2017, 11:01:48 am
content: It works as energy cost varies depending on location and time.

author: coppice
author_rank: Super Contributor
timestamp: November 10, 2017, 03:38:07 pm
content: Quote from: NANDBlog on November 10, 2017, 10:17:17 amIf the manufacturing of something is highly subsidized, and it produces energy which competes against highly taxed alternatives, the cost/benefit analyses can get very skewed.

author: woody
author_rank: Frequent Contributor
timestamp: November 10, 2017, 05:19:42 pm
content: FYI the fossil alternatives are subsidized much much more:https://www.theguardian.com/environment/climate-consensus-97-per-cent/2017/aug/07/fossil-fuel-subsidies-are-a-staggering-5-tn-per-year

author: tszaboo
author_rank: Super Contributor
timestamp: November 10, 2017, 05:57:03 pm
content: https://www.nrel.gov/docs/fy04osti/35489.pdfThere. It is 1-3 years. So raw material transport and other costs are the remaining 4-6 years for the 100% ROI.

author: coppice
author_rank: Super Contributor
timestamp: November 11, 2017, 08:39:29 pm
content: Quote from: NANDBlog on November 10, 2017, 05:57:03 pmI would be highly skeptical about that information. Its dated 2004, when solar panels were far more expensive, yet shows paybacks that look optimistic even at today's prices.

author: Jeroen3
author_rank: Super Contributor
timestamp: November 11, 2017, 09:12:59 pm
content: Quote from: kastnerd on November 09, 2017, 01:35:16 pmYou are somewhat correct. A grid with solely producers and consumers that have unfiltered inverters would be terribly "dirty" in terms of harmonics.It is easy to filter high frequency (>10KHz) "dirt" from mains by means of small inductor and capacitor.It is hard to filter low frequency (<10KHz). This is where line reactors and transformers,physical copper with magnetics, come in and filter harmonics.

author: Circlotron
author_rank: Super Contributor
timestamp: November 11, 2017, 09:23:53 pm
content: Would putting several tens of microfarads directly across the output of a solar inverter help reduce any high frequency noise going out into the AC line?

author: Damianos
author_rank: Frequent Contributor
timestamp: November 11, 2017, 11:26:09 pm
content: Quote from: Circlotron on November 11, 2017, 09:23:53 pmDo you mean that putting some capacitors in parallel with the mains will clean-up the entire grid? I do not think that this works, because of low impedance and creating large inactive currents. I think this is performed before "pollution" reaches the output, by decoupling the output for high frequencies...

author: Mr. Scram
author_rank: Super Contributor
timestamp: November 12, 2017, 12:55:11 am
content: I love how people don't read the thread and plunk in a post that suits their agenda, changing the subject completely.

author: Mjolinor
author_rank: Frequent Contributor
timestamp: November 12, 2017, 08:57:42 am
content: Quote from: Mr. Scram on November 12, 2017, 12:55:11 amMy walrus won't cook my dinner.

author: woody
author_rank: Frequent Contributor
timestamp: November 12, 2017, 09:11:49 am
content: Quote from: coppice on November 11, 2017, 08:39:29 pmHere you'll find a fresher report (2017):https://www.ise.fraunhofer.de/en/publications/studies/photovoltaics-report.htmlTL;DR: payback times between 2.5 and less than 1 year depending on location and type of technology used.

author: Mr. Scram
author_rank: Super Contributor
timestamp: November 12, 2017, 09:20:04 am
content: Quote from: Mjolinor on November 12, 2017, 08:57:42 amMaybe you should take your walrus out to dinner sometimes, and tell her that she's pretty.

author: Jeroen3
author_rank: Super Contributor
timestamp: November 12, 2017, 12:33:59 pm
content: Quote from: Circlotron on November 11, 2017, 09:23:53 pmYou only put capacitors on the grid to compensate for inductivity.If you are experiencing harmonics issues after installation this can be because the part of the grid you are on has a "high impedance". This could mean the transformer you're on is small, or the lines are long. You can't do anything about this except lowering inverter output, storing energy in batteries, or even installing your own transformer or line reactor. Or just take more load.

author: SeanB
author_rank: Super Contributor
timestamp: November 12, 2017, 06:31:01 pm
content: Typical thing to reduce noise is to put in filtering, generally the power companies have LC filters across the phases, and also have harmonic traps in series with the phases, typically tuned to the third harmonic so that the current is more likely to approach a sine wave. The distribution transformers though tend also to be part of the filtering, simply because they are also inductors in the path, though some utilities also deliberately include a bypass capacitor across primary and secondary of the transformers ( tuned to resonate at a predetermined frequency) to pass through the power line control signalling used to control things like power switching, line taps and street lighting, without having to run any extra communications cabling.

author: DougSpindler
author_rank: Super Contributor
timestamp: November 26, 2017, 11:19:55 pm
content: Even if solar inverters produce "dirty" power, don't consumers back-feed dirty power with the devices they connect to it? Such as motors?