Department of strange specifications

[BillK-AZ]

A recent City of Tucson, Arizona procurement specification for a PV system had the following testing/verification requirement:

"Verify that at or near sunset the inverter stops delivering power to the grid and stays in that mode throughout the night. "

How could it be otherwise? I guess they want someone to watch a system all night just to verify this. If one could make power out of darkness, it would be wonderful. The document was dated 3/6/2012, so it was not an April Fool's joke.

 

[wirenut1980]

Sounds like they want to have something automatically disconnect the PV system from the grid using a timer or photocell as control. I have no idea why, but maybe they have some idea that having a small amount of electricity generated by the PV installation in the evening hours is bad?:blink:

 

[iwire]

The inverter (assuming it is a listed grid tied inverter) will have that control built into it.

There is a point where even with the array making some power at low light levels the inverter uses more power to operate than you are getting from the array.

So .... if the inverter tried to stay 'on' all night it would burn up electricity with no gain.

But I believe all listed grid tied inverters will sleep when there is low light levels. A cloudy day or fresh heavy snow on the array should also put it into sleep.

 

[jaggedben]

A cloudy day or fresh heavy snow on the array should also put it into sleep.

That would be a lot of clouds or snow. Most systems will still produce 10-20% of full power on cloudy days, meaning fogged over so you can't pick out the sun. Really dark rain clouds will knock it lower.

 

[BillK-AZ]

I posted this because it is absurd. There is a separate standby loss spec that is conventional.

But, why have a verification of the fact that it does not work at night? Is there a problem with that?

If I ever find one that works at night, I want to study it, improve it, and ..... well, who would then need the sun.

 

[jaggedben]

Maybe they are trying to ensure that no one is using solar as a front for some less clean power source. :lol:

 

[iwire]

That would be a lot of clouds or snow. Most systems will still produce 10-20% of full power on cloudy days, meaning fogged over so you can't pick out the sun. Really dark rain clouds will knock it lower.

I guess my direct observations where wrong.


I think we are splitting hairs over how cloudy.

 

[north star]

$ $

A statement from the manufacturer' own installation instructions
could be forwarded to the person asking for this verifcation.
First, you would have to find the actual person making the request,
...then send them an e-mail with a "cut & pasted" section out of
the manufacturer' specs., for the "sleep mode"......Then, ask if
this will satisfy their request......It WILL require some time to
achieve this, but it [ could ] also establish some good working
relations with the City of Tuscon......Just sayin'...

$ $

 

[crazedengineer]

hmmm

hmmm

I think you only issue is going to be if you have a inverter with batteries. If not, pretty much any inverter will switch its self to Standby when it goes below it shut off voltage on the DC side.

 

[jaggedben]

I think you only issue is going to be if you have a inverter with batteries. If not, pretty much any inverter will switch its self to Standby when it goes below it shut off voltage on the DC side.

Well now you've brought up a potentially real issue. Does Tuscon require that hybrid systems only be grid interactive during the day? Most battery back-up systems are not grid-interactive in that way, but it's food for thought.

 

[hurk27]

A recent City of Tucson, Arizona procurement specification for a PV system had the following testing/verification requirement:

"Verify that at or near sunset the inverter stops delivering power to the grid and stays in that mode throughout the night. "

How could it be otherwise? I guess they want someone to watch a system all night just to verify this. If one could make power out of darkness, it would be wonderful. The document was dated 3/6/2012, so it was not an April Fool's joke.

Kind of like the new sign they put up in my bank"

"The cut off time for deposits will be the time of bank closing"

Ok sure I want to break in to my bank after is has closed to make a deposit:roll:

 

[ggunn]

Kind of like the new sign they put up in my bank"

"The cut off time for deposits will be the time of bank closing"

Ok sure I want to break in to my bank after is has closed to make a deposit:roll:

Maybe what they mean by that is that even if you are already in the bank, the tellers shut their windows down at closing time and take no more deposits. That would suck if you'd been waiting in line for a while.