I run a public library and just got a call from a salesman who saw we’d recently installed some solar panels. He said he had a device he can plug in to the inverter to “clean up” the electricity, taking care of “harmonic imbalances” that can cause computers to run hot, and which waste electricity generally. I told him I’m sure it’d void the warranty on the solar equipment, to which he said, okay, forget about that, we can just plug it in to any breaker box. I figured next he was gonna try to sell me a perpetual motion machine, so I dismissed him. But some cursory internet searching didn’t raise any red flags in re: harmonics, so I wonder if I was hasty. This was his company.
Cleaning up electrical harmonics for better system efficiency: cool or scam?
If you have dirty power due to poor inverter performance, then yes, it is a problem. The issue however, should be directed towards fixing the inverter, especially if relatively new and under warranty, not in buying an aftermarket power conditioner.
Missed the edit window, sorry.
An afterthought: Do you know for a fact that your system suffers from bad harmonics? Or, was this just a cold call from a salesperson looking for a quick sale?
Grainger is a reputable company, so I doubt it’s a scam so much as a legit company trying to sell you something you may or may not need. AC isn’t one of my specialties, but if you’re worried about it, I figure that any certified electrician could check your inverter output and tell you if it needs tweaking.
Your link doesn’t work for me but while there is such as thing as quality of electrical power, and the AC power you get over the grid can be fairly “dirty” in terms of frequency at which voltage alternates and the resulting root mean square (RMS) voltage, the voltage coming from a modern PV solar array inverter should be quite consistent, likely far more so than that coming from your local utility. I can’t imagine what kind of device could be “plugged into” the inverter to clean up the power quality automagically short of an industrial grade uninterruptible power supply, and frankly you’d be better off running the power to your sensitive electronics only through that supply, as your toaster oven, hair drier, hotplate, electric lights, and even most of your home entertainment equipment (except for LED televisions) isn’t going to care. And of course, you shouldn’t be attaching anything directly to the breaker panel without having it approved by a licensed inspector, as doing so can be a code violation and may invalidate insurance and indemnity in the case of an electrical fire or damage.
Sometimes much ado is made over the fact that most static inverters do not produce a true sine wave but rather a waveform that is squared off at the crests, but as long as it doesn’t produce overvoltage and matches the necessary frequency and RMS voltage most household and office electronic equipment switch mode power supply devices will function just fine, as will CFL and LED bulbs, appliance motors, et cetera. Where the waveform quality becomes an issue is on very sensitive laboratory measurement equipment , high torque motors, particle accelerators, et cetera in which case complex rectifiers or locally generated waveform conditioning are used.
I pretty much guarantee that whatever this cold calling wingnut was trying to sell you is pure scamistry. If you do want to follow up, ask the salesman if their device is Underwriters Laboratories (UL) certified. If it is, he should be able to cite compliance with UL 1741 (“Standard for Inverters, Converters, Controllers and Interconnection System Equipment for Use With Distributed Energy Resources”) and/or IEE 1547 (“Standard for Interconnecting Distributed Resources With Electric Power Systems”) as well as the pertinent parts of NFPA 70 (I’m assuming you are in the US, here; otherwise, CE/IEC or region specific standards apply). If you speak of these codes and he isn’t even able to recognize or describe them, he’s definitely full of shit.
I have some very geeky friends with home solar installations. If there was something to install to “clean up” the inverter’s output so computers would run cooler, they’d have it.
Guess what? They don’t have it.
I just wonder how this cold-calling goober has any idea of what specific equipment was installed at the library to know that he has a device that can plug into the inverter.
There’s essentially no such thing as sensitive household equipment anymore. Either you have a big (mostly resistive) load like you mentioned, or you have electronics with a switch-mode power supply, which converts to DC, runs through some big filter caps, and then chops up the result into a high frequency waveform. It doesn’t give a crap what the supply looks like, will happily run on anything from 100-240 volts, AC or DC. Your TV, your computer, your phone chargers, and basically anything that could remotely be called electronics falls into this category.
That’s not to say that it’s impossible to have sensitive stuff… I’m sure there’s someone out there with a hobby that requires sensitive lab equipment. But you’ll know it if this is the case.
Some appliances with high current draws and cheaper SMPS can still be sensitive to large but not atypical fluctuations in voltage or power frequency response, e.g. large LED screens, high power computers, et cetera, hence the recommendation to use an online UPS for critical devices. But yes, normal appliances such as refrigerators, laptop or desktop computers, other consumer electronics, et cetera can be plugged directly into the wall with little concern about normal power fluctuations. In the case of the o.p., however, his PV solar inverter already likely provides a conditioned waveform that is already more consistent than what the utility company does or can provide, and if there is a problem with the power quality it would indicate a problem with the inverter that needs to be corrected, not just filtered by some doo-dad from a random salesclown.
I think Stranger was, after the first quoted sentence, actually being too nice.
There are indeed lots of devices that meet those standards – and perhaps even salesmen who know what they are-- but almost certainly you still don’t need any of it.
Don’t ask about the codes, ask why he thinks your installation needs it, and, if so, why the original installers shouldn’t fix it on warranty. Though, on reflection maybe don’t even ask, that just opens the door for BS.
Not neccessarily the same thing. Home systems (tht ( know about) are single phase. Industrial systems (that (I know about( are three phase. Harmonic mitigation is something you do to three-phase systems. Reactive Power Compensation is what you do to single-phase circuits.
OP: Is your library system multi-phase? Do you sell power back to the grid?
Harmonic mitigation and Reactive Power Compensation are things you do if you if you are running large machines. You do this for two reasons: your large machiInes (or other special loads) might not like it, and, your supplier might not like it. When you run an inverter, you are the supplier: in extreme circumstance your inverter won’t like it, and may artificially limit the amount of power you can get out.
In theory this might apply to a small residential system too. Running a huge plug-pack only load, your demand might be so harmonic that you pay for mains power when you should be using solar power. But I’ve not heard that people have found a market there.
It makes me wonder: do you have a large roof, and a system so large that the salesman thought you were an industrial customer?
Not to lend any credence to the OP’s traveling salesman, but…
The concept and import of dirty power isn’t simply a scare quote opportunity for KIA’s.
Certainly, the notion of a perfect, singular, sinusoidal AC wave being necessary for the operation of common residential applications has been overblown on occasion, but there is no need to go to the opposite extreme by claiming lousy (perhaps multiple) waveforms have no impact on equipment. It does. A poor power factor, et-al, affects equipment efficiency, reliability, and ultimately our pocketbooks.
For those of you who are unaware of plugin power conditioners, goto: power conditioner at DuckDuckGo For those who are unaware of industrial power conditioners, goto: Products - Power Conditioning|Emerson For those who are confused about the difference between a power conditioner and a UPS, goto GOOGLE (do your own work).
Are you having any problems? If not, then don’t worry about it.
Note there is a problem and the words to search Google for are: Power Factor
But it is my understanding this problem would be more a concern of an electric company and lager industrial customers. The electric company is the one who would have the problem. And it is many customers combined that would cause this problem with the electric company.
I don’t think there would be a problem with just a library.
Anyway being as you work in a library and are posting here, you probably want to learn more about this! So search for the words *Power Factor *or Power Factor Solar and read, read, read. Let us know what you learn.
Quick answer is that the grid is shared, and big. Everything from lightning to big industrial customers put noise on the grid. There are also short-term frequency variations based on load (you get a dip when a large new load is turned on). This is because there’s a huge amount of spinning mass (in the form of generators) driving the grid, and while they can respond to load changes, it’s not instant. So with a sharp change they can slow down or speed up.
A home inverter setup is a little different. First, because the frequency is not based on spinning mass, load has no effect on it. Household loads can inject voltage noise into the system, but most household loads are pretty “friendly” in this regard. So it should be pretty clean overall, though if you’re operating a Tesla coil in the garage you still might have some noise problems.
Some clarifications, though:
Most PV systems, even if they supply your entire needs, will still be tied to the grid. They have to match the frequency variations regardless. I think most states still legally mandate a grid tie. So even if your inverter setup can produce a uniform frequency, it won’t in typical use–it’ll just match the grid.
Also, while grid frequency can vary in the short term, in the long term it is extremely stable. Operators run their generators overspeed at night (with low load) if they couldn’t quite keep up during the day. They calibrate against atomic clocks to keep an exact 60/50 hz. Many household clocks still use the frequency as a timebase, and while it might be a minute or so off during the day, there won’t be any further day-to-day drift.
When our plant’s small unit (12Mw) syncs to our sister unit (250Mw) and they subsequently sync further out on the grid (Eastern) there is no atomic clock involved. We are a slave to the next larger (master) unit up the line… and so forth and so forth. Eventually, a competitive state arises between varying sectors of the grid concerning frequency maintenance. This is where the voodoo occurs involving load shedding and acquisition, operational diligence, etc. None of this involves any reference to atomic clocks.
Granted, there is a tight operational tolerance involved that allows but a few percentile deviation, on average, over a 24 hr. time frame (less on an instantaneous basis). But nothing requiring the precision or accuracy of an atomic clock. Emerson, Honeywell, etc., are perfectly capable of this level of time management… So where did this notion come from?
Balancing and Frequency Control, from NERC
*Time Control
Frequency and balancing control are not perfect. There will always be occasional errors in tie-line meters, whether due to transducer inaccuracy, problems with SCADA hardware or software, or communications errors. Due to these errors, plus normal load and generation variation, net ACE in an Interconnection cannot be maintained at zero. This means that frequency cannot always be maintained at exactly 60Hz, and that average frequency over time usually is not exactly 60 Hz.
Each Interconnection has a Time Control process to maintain the long-term average frequency at 60 Hz. While there are some differences in process, each Interconnection designates a Reliability Coordinator as a “Time Monitor” to provide Time Control. The Time Monitor compares a clock driven off Interconnection frequency against “official time” provided by the National Institute of Standards and Technology (NIST). If average frequency drifts, it creates a Time Error between these two clocks.*
So in the long term (hours on up), the time standard comes from NIST official time, which is of course based on atomic clocks. It is allowed to have some relative drift on shorter timescales.
As an addendum, what I mentioned about long-term stability may not be true forever. Already, NERC is running experiments to see if people really care about perfect long-term stability.
I’m not sure what you’re disagreeing with, if anything. The long-term average is indeed determined by the atomic clocks at NIST. A clock based on counting cycles (like a synchronous analog clock) will keep excellent time for many years. In the shorter term, there may be variation of ~0.1%.
That smaller operators have no need for such high precision timekeeping is irrelevant, since as you say they just sync up to larger units and the rest of the grid. Though even this is changing–GPS time (also based on atomic clocks) gives a stable timebase and helps decrease phase error (which can be wasteful). Not sure how prevalent this is but the tech is out there.