Grid tied when the grid is down...Can I do anything?

[(unknown)]

Apparently this is a dumb question, so forgive my lack of knowledge.

I just put up a 2150W grid tie system. When the grid is down, the inverter shuts down and isolates the panels, so there they are on the roof being useless.

My understanding is that without batteries, there is no way that I can get useable power from the array, since it is wired for a high voltage.

Is there any cheap and simple solution? People on this board seem pretty savvy, so instead of me making ill informed speculations, perhaps you all could give me some suggestions or further education about what I just put on the house.

I know, I should have learned more about it an installed it myself, and all that, but with two kids under three, two jobs, and endless projects, I just couldn't manage that this time around....

Thanks for any help!

Andrew

[Nando]

Andrew:

You ask questions but you do not give any information.

No body, and I mean, No body in this group has the mental capabilities to read your mind and determine what you have.

So, start by informing what type of system you have with all the details then may one or more will be able to give suggestions for a possible solution to your problem .

Nando

[Kevin L]

If correctly done, the load could be dumped to hot water heating and/or resistive element heating for the home but I doubt if the added expense is worth it unless your grid is down all the time.  If your grid goes down like ours then you should save some money and let them be useless for less then 0.05% of the year.

Kevin L

[Kevin L]

Sorry forgot a zero.  So it would go from being useless 60% of the year to useless 60.005% of the year.  Seems like a non-issue.

Kevin L

[ptitchard]

Andrew,

To be honest, unless you have lots of power cuts it is not worth worrying about.

When you bought the system you could have gone with a system that included back up batteries to provide power during grid failures.

These systems come at added cost mainly due to battery costs. An example is manufactured by Magnetek / Eoltec MWI5200-48. http://www.solacity.com/Docs/MWI%20Manual%20V1_0.pdf

A grid tied system must by law disconnect from the grid when the grid is down to protect the engineers who have to fix the fault.The way these duel role inverters work is that essential loads ie fridges, alarm systems, etc are wired directly to the inverter so when the grid fails the inverter takes over using the backup batteries as the power source. It is exactly like UPS (un-interuptable  power supply) used on computers so if a pwer cut occurs they can continue and shut down the computer in a controlled way and not loose data.

Hope this helps to expand your know how.

Regards

Paul

[Gary D]

 My first thought is that you needed to have a licensed installer do the connects and inspection at the very least to qualify to be interconnected. The tax break you get next year (federal and most likely state) could be put to good use by helping with offsetting a solar domestic hot water pre heat system. If you paid for the system, and aren't leasing it, you can sell the "green tags" also.

 Your system should produce(offset) between 8 to 10 kilowatt hours a day of grid power depending on the solar radiation in your area(4 to 5 hours average in the U.S.)

 As you say, when the grid goes down, your panels don't produce. As others are wondering, what type/brand name inverter do you have, and could you trade it for a multifunction one if you desire(depending on the type you may not need to)? You would probably then need/want a sub panel with a double throw switch for necessary critical loads and yes a battery backup. The sun doesn't shine at night, during storms, and when many blackouts occur. Perhaps this helps, or maybe not worth 2 cents, just a few thoughts, no morning beverage yet....  Gary D.

 

[nothing to lose]

"60% of the year to useless 60.005% of the year."

I think your numbers are still messed up, I would not want anything that was useless for near 60% of a year

That would mean it only works less than half a year!

[Brian H]

 In all seriousness, your best bet would be to contact the company that installed your system and ask them what your options are. Even if someone here on this board could explain exactly what components to acquire and replace/install to make your panels useful without the grid, it would still have to be installed by a licensed professional and inspected to ensure compliance with code, etc. assuming that you still want a grid-tied system in the end. All of which you have indicated that you don't have time to carry out anyway, right? So that's why I reccomend calling the installer. He alone knows more than anyone what you have, and what it would take to add a backup battery system.

 Alternatively, if you're just looking for backup power to see you through short grid failures of a few hours to a few days or so, you're cheapest option would probably be a gas powered generator.

Cheers!

BrianH

[(unknown)]

Well you could keep some batteries charged when the system is grid tied and have a second inverter powering a few house circuits. Outback makes several that will do this. Check the GTFX series. Inverter will start around $1500 though. If you only need to power a few house circuits and don't mind manual switching then any sine wave inverter that will handle the load can be used and some come with a battery charger.

[(unknown)]

Thanks everyone for your thoughts, and Nando, sorry for lack of info, I was already up past my bedtime...

I have 10 Sunpower 215 watt panels, and a Sunpower SPR 2000 inverter.

I do have a propane generator for backup, so it is not so much the short term brief outages that concern me.

I guess that I have a little bit of the paranoid about the general state of the world thing in me, and I am just trying to think ahead to what I would do if the grid was really down for an extended period.

I live in Vermont, so hurricanes are not a concern, but we can get ice storms, and the one in 98 did tremendous damage in Quebec and there were places out of power for quite a while. I don't have any idea if climate change will create more or less seriously damaging weather events up here.

Then there is the more paranoid stuff, and I think I am a victim of looking too much at discussion boards, but there are sure loads of people freaking out about peak oil, flu pandemics, terrorists with nukes, and other scary stuff that could also interrupt the grid.

Anyway, I was just dreaming that there was some solution that would be cheap and easy. The installer didn't have one, so I'm not surprised that one does not exist.

Seems like if I really want to be prepared for any eventuality, I'd need a different inverter and a battery bank.

Sigh... Hopefully the world will not come crashing down before there are great new innovations to equipment that make it cheap and I can afford to upgrade...

Andrew

[Nando]

DEE:

If you know the RPM as well as the number of poles that the generator have then one can calculate the operating frequency at known RPM values.

With the wide Voltage DC operating range of the windy boy ( set for 230 Volts AC = European) one can use smaller power transformers in boost mode and rectifying diodes in parallel with the regular diodes to present a higher voltage to the Windy Boy and and the addition of a small circuit detecting a band output voltage triggering TRIACs to insert or disconnect the transformers from the DC voltage link feeding the windy boy, you can obtain a much higher operating range.

I have attached a schematic showing the principle if the frequency of the generator is greater than 35-40 HZ at the lowest boosting voltage.

Nando

[Kevin L]

Nothing to Lose,

Last time I checked Solar systems didn't work at night, Plus the power lost for cloud cover and morning and evening power drops when the array is far from pointing at direct sunlight.  Thus 60% is conservative based on a good location like southern california or arizona.  Drop pv in seattle and their 300 rainy days a year and you'll see much much less.  Unlike the wind, sun doesn't shine at night.

Kevin L