new inverters provide power when grid is down / power failure / blackout occurs.

Re: new inverters provide power when grid is down / power failure / blackout occurs.

This is really cool.:cool:

According to the discussion in the links it will have an optional "dedicated power socket" able to supply "up to 12 amps so long as the PV is generating". No definite word on what the US versions AC output voltage will be. (12 amps x 120 or 240 or 120/240vac?)

It may be possible (while the sun is shining) to cool a refrigerator/freezer, pump water and charge a small but useful portable battery system. You can do a lot in an emergency with a 100 amp/hour 12volt battery. You could spend less than $500 and have lights, communication and some medical equipment 24 hrs/day. (Sleep apnia machine, nebulizer...?)


-Alex

Re: new inverters provide power when grid is down / power failure / blackout occurs.

niel wrote: »

a few days of clouds after losing the mains would prove the feature to be nearly useless.

I think you're overstating. A 3000watt inverter (the smallest model) should be able to run a 200W fridge for a few hours a day even on a cloudy day. 10% sunlight is unusually bad weather. As long as people still understand that they have to prioritize what they use it for, they should be able to take advantage of it even if there's clouds. The most valuable energy is used for communications and that does not take a lot of power at all. I think that's pretty far from 'nearly useless.'

I agree with you about medical equipment. Someone in need of that should probably own a generator. Although perhaps with this feature they might be able to avoid using up their fuel as quickly.

Most importantly, it will stop everybody from asking "Is there a way to use the power from my solar system when the grid is down?" I'm really looking forward to not hearing that question anymore.

Re: new inverters provide power when grid is down / power failure / blackout occurs.

Cariboocoot wrote: »

I also can't help but think that the average person will misinterpret this feature as meaning they will have power available 'whenever' and be sorely disappointed when it isn't.

I think the average person will understand that a solar system doesn't deliver power without the sun.

Mind you, I get your point. Half the people out there are below average.

Re: new inverters provide power when grid is down / power failure / blackout occurs.

inetdog wrote: »

Except for the children in Lake Woebegone, of course.

Where all the women are strong, all the men are good looking, all the children are above average and the solar panels put out by the light of the moon.:-)

Re: new inverters provide power when grid is down / power failure / blackout occurs.

t00ls wrote: »

I think there is already inverters that provide power when the grid goes down......they have been around for a while, they use batteries and solar panels........hello

Let's look at the economics for a minute. It costs me $0.064/kWh to supply myself electricity with my grid-tied system, or it would if I used all the electricity that I generated. Alternatively, I could buy electricity from the utility at $0.108/kWh. Or I could go off-grid, but the folks on this forum say that the costs for off-grid are roughly $1.00/kWh (+-50%) when you include battery replacement costs, reduced generation efficiency, etc. So the economic choice clearly favors a grid-tie PV system.

Are there any disadvantages of the grid-tie system? About the only one that concerns me is having solar panels that are useless when the grid goes down, and the possibility of freezing pipes in the winter. In the 2.5 years that I have lived here, the grid has never been down more than an hour or so. However, I have lived in a place where the grid was down for 7 days. Is it worth it to me to go off-grid and pay $1.00/kWh to avoid the occasional (once every 10 or 20 years) extended grid failure. No. Is it worth it to pay an extra $500 (I don't know the actual cost) when I replace an inverter to get a grid-tie inverter that could provide a small amount of emergency power to avoid freezing pipes and the loss of food. That sounds fairly attractive. I also have a 4 kW, propane-fueled, Onan generator that was used at an off-grid property that I recently sold. I need to trade off the cost to buy and bury a propane tank (in my city location) or convert the generator to natural gas (if possible) and extend a natural gas line versus the solar PV inverter with emergency power.

I live in an area that has relatively high solar insolation (5.78 kW/m^2/day annual average), and rarely two completely overcast days in a row. My refrigerator draws 37 W (avg.), and with a natural-gas fired, hot-air furnace, I just have to run an effcient ECM motor and the controls to have space heat. Heck, with the solar hot water I could even shower! The house could probably go several days or more before it ever dropped below freezing, so occasionally running the gas heat would be the cat's meow.

Re: new inverters provide power when grid is down / power failure / blackout occurs.

Cariboocoot wrote: »

Try to keep in mind that SMA's new inverter supplies power without batteries for a short time. That is the "trick" here; no batteries to maintain or replace. The limitation is that the power is only available while the sun shines.

If I take my monthly output and express it as equivalent hours of AC power at the rated DC power output, I average 4 to 6 hours of full-power operation for every month except December, when it is around 3 hours (Figs. 10 and 11 at http://www.residentialenergylaboratory.com/comparison_of_pv_systems.html. So for my 3.15 kW DC-rated system, that is 26 Amps for that length of time. Since the emergency power is 10 A, the period of operation should be significantly longer.

However, the things that I would like to run may not take kindly to being switched off and on, so it may yet take some batteries. Alternatively, I could at least run a small electrical resistance heater that would be sufficient to keep the house above freezing.

Re: new inverters provide power when grid is down / power failure / blackout occurs.

"So for my 3.15 kW DC-rated system, that is 26 Amps for that length of time. Since the emergency power is 10 A, the period of operation should be significantly longer."

i'm not too sure what it is you are saying here, but if you are saying that if you are providing more power than the inverter needs to produce the 10a or so that your time will be extended. you may also be thinking if you draw only 5a while it is providing 10a available that you can extend the time.

both cases are false. if it is giving 10a then use it or lose it as it does not get stored.

Re: new inverters provide power when grid is down / power failure / blackout occurs.

inetdog wrote: »

I think that all he is saying is that if his panels can produce their full PTC output for 4 to 6 hours on a clear day, then the region on the insolation curve where the available output current stays above 10 amps would start earlier and end later than the full power period, giving him more than 6 hours of "up to 10 amp" output. (Again, on a clear day.)

Definitely not a factor of 2.6 longer, but that is not what he is saying.

The interpretation given by inetdog is exactly what I was trying to communicate. I gave no estimate of how much longer the system would be capable of producing the emergency power at 10 A, but that it would logically be longer than 4 to 6 hours (depending on the time of year), since it averages 26 A over that time period, and the output of my panels as a function of time is roughly a bell-shaped curve (on a reasonably clear day).

Re: new inverters provide power when grid is down / power failure / blackout occurs.

Cariboocoot wrote: »

When the utility grid is down the output of a standard grid-tie inverter is zero, no matter the size or location.
This new one provides power without grid or batteries so long as the array can meet the power demand.

Of course.

I expect they have included a super capacitor to stabilize the DC input against the draw as well as an oscillator to provide a sync signal, but I haven't seen a schematic and it's unlikely they plan to make it public.

That is really a key specification, isn't it, that I have not seen in the spec. sheet. It seems like it would have to have at least a minimal amount of storage (super capacitor or battery) to make usable power. Otherwise an airplane flying over could shadow the array, putting the loads into disarray, like the compressor on a refrigerator.

Re: new inverters provide power when grid is down / power failure / blackout occurs.

To have (some) emergency lights and small electronics 24 hrs with this new SMA GT inverter:


From Wind and Sun:

SunXtender 12 Volt 104 Amp-Hour AGM Deep Cycle Solar Battery $ 307
http://www.solar-electric.com/pvx-1295.html

PowerMax 12 Volt 35 Amp Battery Charger $ 103.50
http://www.solar-electric.com/pomax12vo35a.html

Samlex 300 Watt Sine Wave Inverter 12 Volt $ 130.95
http://www.solar-electric.com/sa300wa12vos.html

A good storage container, misc basic wiring and a small battery tender to keep everything safe and ready +/- $ 100


This system could easily keep a couple of CFLs or LEDs going full time and run a laptop and phone charger for + 8hrs. Other possibilities include the igniter and thermocouple for a gas range or short cycles of a gas furnace fan and controls. Make no mistake, 1200 W/h battery has a useful amount of energy storage for emergency use.

The Concorde AGM battery and the charger listed above can handle a high enough rate to charge ( to +/- 90%) in as little as 3 hrs while drawing something around 600 watts from the battery-less GT inverter. If it is in the budget a small Honda 1 or 2kw generator would make a long term power outage even in poor weather much more comfortable.


I know many GT PV system owners who would be interested in this. The high cost of emergency backup power is always a big disappointment in the initial consultation for a new PV customer. The modest investment above is much easier to swallow than a full battery backup system with need for a new +$3k battery every 5-6 years.

-Alex Aragon