Non-connected electrical connection

[craig110]

I found some solar panels that can be purchased at about 30% below the normal dollar-per-watt figure.  The gotcha is that these panels, while newly manufacturered, have been relabeled so they don't have a UL rating and thus can't be used for grid-tied applications.  (Such as mine, sigh.)  This got me thinking and so let me toss the question out as a general, and hopefully fun, thought-experiment for everyone to ponder: Non-UL equipment can certainly be used at a site that uses grid-tied panels, its just that the non-UL panels can't be electrically connected in to the grid-tied equipment.  How can one get the power from non-UL panels into the UL-based grid-tie system without having any electrically-conductive paths between them?

To get the thinking started, here is one way of doing it without batteries (the constant charging and discharging would kill them quickly): One could take the output of the non-UL panels and use that to drive an electric motor that turns a shaft made out of a strong but non-conductive material (PVC piping?) that attaches to a generator that feeds the grid-tied side.  This would transfer the power (with inefficiencies, of course) without having an electrically conductive path.  What other ideas can people come up with that would have lower inefficiencies?

p.s.  And no, I'm not planning on implementing anything like this.  30% off the normal panel prices is nice, but isn't enough of a discount for me to suffer the conversion inefficiencies of an odd connection like this.  This discussion is just for fun.  (Who knows, though, as some really great approach might surface!)

[drdongle]

A motor-generator setup would be very inefficient, a DC to DC converter would be a simpler, cheaper, and more efficient option.

[craig110]

Yes, but wouldn't a DC-DC converter still entail a direct electrical link between the non-UL and UL sides even if it is just in the box's ground?

[craig110]

Ah, just found isolating dc-dc converters.  Interesting.  What kind of efficiencies do they typically run at?  (Thoughts of those new panels are starting to dance in my head...)

[mtbandy]

What about a switched capacitor based system? Panels charge a large capacitor bank, capacitor then switches over and dumps it's charge into the inverter. You could do this several times per second, and there would be no physical connection to the gridtied inverter if you used a relay :p might be pushing it a bit though, and it would only be able to send power when it's sunny.

The other way would be an electrolyser and gridtied fuel cell, that should be as efficient if not more than batteries.

[RUFUS]

Are any of the home made wind generators used on this board grid tied?

Hook it up and keep your mouth shut.

                                      Rufus

[Countryboy]

It's my understanding that you can't have a non-UL device hooked directly to the grid.

You can use non-UL stuff, as long as you have a UL device between the grid and the non-UL device.

The only thing that connects directly to the grid is the grid-tie inverter.  You can hook up non-UL panels to a UL grid-tie inverter, and you are fine.  The non-UL panels are not connected directly to the grid because they have the UL grid-tie inverter between them.

A UL grid-tie inverter has the capability to immediately isolate the panels from the grid if there is a problem - and that's what the utility is worried about.

[craig110]

Do you have any reference for that?  If I can verify that, it sure would be good news.

[Countryboy]

http://www.fieldlines.com/story/2006/7/19/152753/292

I don't know the exact specifics for your state.  As best I can tell, most states require the 'point of common coupling' to be a UL device.  That is, the interconnect device between the generation facility and the grid.

The utilities could care less how you generate the electric, or what quality it is within your system.  Their primary concern is the point of connection where your system feeds their's.  They don't want you feeding power if the line is down, killing a lineman, and they don't want you feeding a screwy voltage which can damage their grid equipment.

[TomW]

craig;

I do not have a reference for it but if you use a wall wart [wall transformer] on a device you do it every time you use it.

Most companies do not get the U.L. on the device itself, like a modem, they just use U.L listed power supplies. Simply a difference of scale between the modem and a solar panel.

Just an observation.

Cheers.

TomW

[craig110]

Thanks.  I'll check our state's laws on this.

[craig110]

Thanks for the suggestion, but while others might do that, it isn't my style.  

[nothing to lose]

Good points here on this.

Also keep in mind often all UL aprovel means is that someone got paid off to say" Ya, okay" on a device.

I have several things I consider dangerous that have UL aprovel! They got paid off!

One example, a deep fryer. Has about a 6" ac cord attached by magnets! Ok least little bump to cord or movement of fryer and it pops off. This is a kitchen device meant to be used on a counter which would of course normally be near a sink in most homes. So your washing dishes and have wet hands, you bump the cord and it falls off, without thinking about it you grab the plug to snap it back on, ZAP!!!! 120Vac direct to your wet hands!!

 UL approved! Ya, someone was paid off somewhere!!!! Why don't I just test for live AC wires using my tougne, just as safe!!!

That is one example. I have been shocked, not exactly like the above, but shocked 3 times in 2 years now at least by this UL approved device!!! Can we say PAY OFF!!!

It certainly was not UL approved for being SAFE to people that is for certain!!!

And of course the corrupt money grubbing legal system, just try finding an attorney to handle a lawsuit against the UL aprovel of that device! Gee if I was Bill Gates maybe I could afford to sue them!

Well I have modified that deep fryer myself, it probably is no longer UL aproved but now it is safe!!! With those nice big screws I added for $1 that $50 deep fryer should never shock me again! That cord will never fall off again but UL would maybe not approve it?

Do what you gotta do, and don't tell no-one!

I have voided UL Aprovel on several other items that were dangerous in real life use also similar to the deep fryer.

At one time to begin with UL was decent, but now like any other government or insurance etc.. funded operation it's only out for money and payoffs!!

[Ungrounded Lightning Rod]

You can use non-UL stuff, as long as you have a UL device between the grid and the non-UL device.

Remember, though, that UL approval isn't just about meeting the electrical code.

It's also about insurance - especially fire insurance.

UL = Underwriter's Laboratories.  It was set up by insurance companies ("Underwriters") to reduce their risks by testing equipment for safety and allowing insurers to give lower rates to those who have only the proven-safer equipment in their insured premisis.

So in addition to meeting the electrical code for your house and for your interconnect, you also need to read your insurance policy to be sure you're not voiding your fire insurance with your home power instalation.

(It's also another reason to have a utility shack with any non-UL equipment located a goodly distance away from the house (like more than six times its height), rather than attached or inside the structure.)

[craig110]

I agree.  For this reason I won't be getting those non-UL panels after all.  Unless I want to put the panels right in the middle of my small front yard where they will be more shaded by trees (not likely on many counts!), they'd have to go up on the roof with my other panels.  Being attached to the house, having them inspected and UL rated are both important.