Solar power anyone ?

[Beltman60]

the micro inverters need 110 volts

 

[dmccarty]

Can anybody explain why a simple automatic drop out switch arrangement would not suffice to break from the mains in a power outage, leaving your array connected to your panel? With this option you could probably do with minimal batteries just to supply ride thru of nulls caused by clouds.
Thanks,
,,,,larry

The inverters detect if the grid has power. If there is no grid power, the inverters do not invert the PV panel's DC power to AC. I don't think the inverter can tell if the grid is disconnected in an outage, so the inverters stop inverting so they will not back feed the grid. You would think the inverters could be built so that they could control the grid power going into the house and the inverter could have a switch that would be flipped when the grid was off line. BUT, the problem with this is if you do not have batteries, and the panels are producing 1KW and you need 10KW, what happens to those devices that do not get enough power?

I think it all gets back to needing batteries when the grid goes away and batteries are EXPENSIVE.

Later,
Dan

 

[TnAndy]

Can anybody explain why a simple automatic drop out switch arrangement would not suffice to break from the mains in a power outage, leaving your array connected to your panel? With this option you could probably do with minimal batteries just to supply ride thru of nulls caused by clouds.
Thanks,
,,,,larry

That's what a hybrid inverter does.....it can operate in grid tie OR off grid mode.

Although you're assuming by the use of minimal batteries, your outage happens from about 9am to 3pm on a fairly cloud free day. That isn't the case here.....seems the sorrier the weather, the more likely the power is to fail.....or around midnite when some drunk takes out a pole. Panels aren't producing in rain/snow, or around midnite.

Also, you have to have other equipment, like charge controllers, the minute you introduce batteries into the mix. Grid tie ONLY systems don't have those, since they also don't have batteries.

Sounds like it would be simple to cook up what you're thinking.....until you actually try to cook it up.

 

[BrandonR]

the micro inverters need 110 volts

They need 240 volts actually and 60hz

http://enphase.com/wp-uploads/enphase.com/2011/10/Enphase-Datasheet-M215-Microinverter.pdf

 

[BrandonR]

The inverters detect if the grid has power. If there is no grid power, the inverters do not invert the PV panel's DC power to AC. I don't think the inverter can tell if the grid is disconnected in an outage, so the inverters stop inverting so they will not back feed the grid. You would think the inverters could be built so that they could control the grid power going into the house and the inverter could have a switch that would be flipped when the grid was off line. BUT, the problem with this is if you do not have batteries, and the panels are producing 1KW and you need 10KW, what happens to those devices that do not get enough power?

I think it all gets back to needing batteries when the grid goes away and batteries are EXPENSIVE.

Later,
Dan

Batteries are expensive and for most locations the grid is extremely reliable so they are a waste. If you are building off-grid then you aren't using microinverters so it's a moot point that they don't work without the grid.

 

[rmorey]

Can anybody explain why a simple automatic drop out switch arrangement would not suffice to break from the mains in a power outage, leaving your array connected to your panel? With this option you could probably do with minimal batteries just to supply ride thru of nulls caused by clouds.
Thanks,
,,,,larry

As what everyone else said, plus, a central inverter will take some time to establish whether the incoming AC power is of an acceptable level, both voltage as well as frequency, before it hooks up to it.

The reason is the act of connection to a power source causes voltages and frequencies to fluctuate for a while before they stabilize. An example is connecting a generator to an inverter to power the charging circuit. It usually takes about 30 seconds before the inverter will accept the AC input from the generator.

 

[SPYDERLK]

Ok now wait. ... You have solar power charging a minimal battery with all micro inverters feeding from the batt. Power goes off and the grid tie at the mains drops out automatically [so the inverters dont have to turn off and are refined so that they dont], but leaves your house connected. Sensors determine whether solar is abundant or critical. You are immediately alerted if you are there. If solar is critical you can take action by shedding load and/or adding adaptive charge to the batts using an inverter gen and DC power suppy. The circuit is shut down in an orderly fashion if it is necessary as batts deplete.
,,,,It may not be designed to work that way, but why not?
larry

 

[BrandonR]

Ok now wait. ... You have solar power charging a minimal battery with all micro inverters feeding from the batt. Power goes off and the grid tie at the mains drops out automatically [so the inverters dont have to turn off and are refined so that they dont], but leaves your house connected. Sensors determine whether solar is abundant or critical. You are immediately alerted if you are there. If solar is critical you can take action by shedding load and/or adding adaptive charge to the batts using an inverter gen and DC power suppy. The circuit is shut down in an orderly fashion if it is necessary as batts deplete.
,,,,It may not be designed to work that way, but why not?
larry

Microinverters are not connected to batteries, they are mounted directly to the panel and consume all available power from the panel there is no storage.

You are describing a off grid/grid tie hybrid central inverter system, those do exist. They are only practical (cost-wise) where there is flaky grid power because the batteries are expensive up-front and are an ongoing maintenance (expense) item long term. You are essentially creating a "whole-house" UPS with multiple charging sources.

 

[TnAndy]

You have solar power charging a minimal battery with all micro inverters feeding from the batt. Power goes off and the grid tie at the mains drops out automatically [so the inverters dont have to turn off and are refined so that they dont], but leaves your house connected.

You just described EXACTLY what a hybrid inverter system does.

However, microinverters don't work that way. They change low voltage DC into 240AC right at the panel....one per panel. The advantage of that is cost ( $150 each versus $1500+ for a central inverter ), low power loss from the panel to the grid connection, since it is 240AC versus low voltage DC, and simplification.....you literally plug and play.

Also, they are easy to expand. Say I want to add one panel to an existing system. I buy one panel, and one micro inverter, mount, plug in and produce.

With a hybrid central inverter, there are many other factors to consider.....will the charge controller handle my expansion ? If not, add another 600 buck charge controller. Are the inverters at max now ? If so, add more central inverters. ( 1500-3000 bucks ). Are my disconnects and fuses rated to handle more panels ?. And so on and so on....

Expansion isn't NEAR as easy with a central inverter setup. Done both, micro inverters win that prize.

You are immediately alerted if you are there. If solar is critical you can take action by shedding load and/or adding adaptive charge to the batts using an inverter gen and DC power suppy.

larry

You can be producing 10,000watts of solar, and a cloud pass over, and the production go to 1,000....immediately. Unless you were planning to sit there with your finger on a breaker to kill the circuit to your freezer at the exact right moment, it would brown out.....attempting to draw more amperage as the voltage decreased and burn out the motor.


GO to my Enphase page: https://enlighten.enphaseenergy.com/public/systems/4Y8U142036


Look at the graphs at the bottom of the page. Pick a day with a lot of spikes in it.....that's a day with sun and clouds....like Wed, Aug 14th for example. Mouse over the 2nd high spike in the morning...it will give you the time and production. 3315 watts at 9:50. Then mouse over the dip next to it. It falls to 909 watts at 10:10. There is a twenty minute window with over a 2,000 watt variance in production. Does the same thing the rest of the day...peaking at 4354w around solar noon ( 1pm daylight ) up 1500w from 15 minutes previously.

The battery bank in the system buffers that load. The hybrid inverters feeding off the batteries will also shut down if the bank voltage drops enough, but that is like you sitting there having to regulate it

 

[TnAndy]

Batteries are expensive and for most locations the grid is extremely reliable so they are a waste.

Right up until the grid isn't reliable anymore....then they are priceless.

Don't assume the NK or China or Russia don't have an EMP weapon floating overhead right now in a "communications" satellite waiting for a signal to drop over Kansas.

OR the sun won't spit out a Carrington Event class solar flare and reduce the grid to smoking ruins.