Lowes selling solar collectors

[Jules Richardson]

I thought you got paid by the 'leccy company over there for the electricity that you generate - who then raise prices accordingly to cover their costs?

[Jim Yanik]

[e-mail] wrote in news: [e-mail]:

what's the point of having solar panels if they shut down when you lose mains power and REALLY need them?

3 KW would easily keep your fridge going and your food unspoiled. (and your beer cold!) 3 KW would probably power the entire home,excluding heating or airco.

Perhaps they note the loss of the 60 HZ mains freq;with no sync signal,they shut down. If the panels tried to sync to each other,they would quickly drift to some out-of-spec limit. (lacking any reference) Hopefully,a narrow limit,as too far off 60 HZ can damage some appliances.

[gfretwell]

Plug in collectors have been around for a year or two. They simply shut down when the grid stops. I agree it is not useful in a power failure but that is true of any grid tie system.

These things are U/L listed so I am not sure exactly how the AHJ can stop anyone from using them. U/L says they have been tested and they are safe. What would you cite?

[trader4]

Why would that be? If you have any type of solar generation system on your house, to the extent it's meeting the needs of your house, the house is pulling that much less power from the grid and the meter reflects lower usage.

[trader4]

I can see the obvious need for any solar array to disconnect from the grid when the grid power goes down. The more interesting question is why no one has a system that will allow the home to still be powered by solar while disconnected from the grid. There are obvious issues with that too, like the house experiencing brownout when the sun goes behind a cloud. But you would think with some smart's in the controller it could allow the house to be powered, no? Say for example, the controller detects 50% of max power from the array for 30 mins continuous, ie it's a reasonably sunny day, so it turns on power to the home, but not the grid. If it can't meet the load because it then gets cloudy, it could turn off, then repeat process. I guess the issue is how well that would work, for how many parts of the country, etc vs the added complexity and the annoyance of having power come and go.

[trader4]

The question is if it's possible to have a solar array system that would power the house provided there was enough sun WITHOUT the batteries. I know you can do it with batteries. And if not, why not.

[RickH]

How much are they and would I recoup my investment in my lifetime?

[JIMMIE]

If they dont shut down the inverters are going to be trying to feed the whole neighborhood at least and will let out all the magic smoke that allows electronic componets to function. Besides that you wouldnt want to try to use the direct output of an inverter not paralleled with the PoCo. Its a very nasty looking square wave that can have 400 volt peaks. When attached to PoCo all of this is cleaned up.

Jimmie

[Tom Horne]

Grid tie inverters shut down when they cannot synchronize to the grid. No utility power means no inverter output. It simply shuts itself off without any user intervention.

-- Tom Horne

[krw]

What do you do when a cloud floats by? Let the voltage sag? Shed load? Interrupt? None of the options are good.

[krw]

Depends on how much you can get your neighbors to pay for them.

[Tom Horne]

In a practical solar emergency back up system there will be a battery bank. The batteries add markedly to system costs and require periodic replacement. A battery charging controller can use a grid tie inverter as a diversion load for the system. When the batteries are charged the output of the solar array is diverted to the grid tie inverter. When the batteries need recharging they get the solar array power they need via the charge controller with any excess power diverted to the grid tie inverter. An automatic or manual transfer switch transfers the emergency loads to a separate regular inverter that runs off of the batteries when utility power is absent. The grid tie inverter senses the emergency inverter output as non utility and does not turn on unless the emergency power inverter is of the true sine wave output type in which case the grid tie inverter will synchronize with the emergency inverter and share the load. That would have the effect of increasing the loads the emergency system could carry up to the limit of the solar and or battery capacity available.

Some generators can deceive a grid tie inverter. The larger the generator and the better its power quality the more likely that is. The good news is that there is no danger caused by that as long as a proper transfer switch is used on the emergency inverter and generator system. The grid tie inverter will only reduce the load on the generator and if you use the battery charging and emergency power inverter system then the grid tie inverter would only get the extra current that wasn't needed by the batteries. The switching and sharing of the solar arrays output is all handled by the charge controller or an add on diversion controller. If an automatic starting generator is available the emergency inverter will signal it to start if the load exceeds the capacity of the emergency inverter or if the battery voltage drops to it's minimum safe level.

-- Tom Horne

[Hell Toupee]

They do run when disconnected from the grid, that's a standard feature. Homes powered primarily by solar typically use the grid only as a backup/supplemental power source for when the solar is insufficient to meet demand, or offline for maintenance. Having the grid as the sole electrical backup is acceptable if you assume that the grid usually won't go down very often or for very long, which is true most of the time in most urban/suburban parts of the country. Adding a generator or a battery to the system will provide another supplemental supply in case the grid goes down and the solar array is insufficient to meet demand.

[Hell Toupee]

No, during those times you supplement from the grid. OTOH, during the hottest, sunniest part of the day (peak demand in the high temperature regions), the solar array is providing most or all of your electricity, which is especially helpful if your local utility charges more during times of peak demand. Sure, solar doesn't work at night, so you have to draw from the grid then - but that's when electrical costs are lowest.

[cjt]

... like every night.

[gfretwell]

At the current price, they would pay back in about 20 years. To be successful they are really going to have to cut the price. Of course there are incentives (tax rebates etc) that will close this gap considerably.

[krw]

What a dumbass.

[trader4]

I'd like to see a citation for that. I've looked into them a bit and all of the ones I've seen will not power the home when the grid is down, unless they are specifically designed to do that and include batteries which obviously have big negative issues. Hence, they would only make sense for true isolated homes in areas without a grid. That is what everyone else in this thread is saying too.

Homes powered primarily by solar typically use the grid only

That's true, but they also turn themselves totally off without the grid power being there.

Having the

[JIMMIE]

There are types of inverters that allow this but this is not usually the case.These systems are much more expensive as they have to be sized to handle peak loads even if they are only momentary loads. Batteries are a must to handle these surges.

Jimmie

[gfretwell]

I have heard about a hybrid system too but that is a lot more complexity and cost than you would have with a simple grid tie system. You need transfer equipment, load management and batteries.