Solar power anyone ?

[dmccarty]

Sunny Boy (SMA America) now has a line of string inverters that will produce up to 1500 watts (at a dedicated outlet connected to the inverter) while the grid is down, and of course the sun is shining.

Outback and a couple others now offer a "grid-interactive" central inverter. It is a bus-bar based inverter that has a separate relay for the grid-tied line. If utility power is lost, this relay opens to disconnect from grid, but the home is still fed on the "backup" breaker panel from solar panels and/or batteries. They have smaller inverters in GT/GV series, but their Radian series has dual AC input where you can connect generator to charge batteries in event of low solar output while disconnected from grid. This beats having to buy two inverters to accomplish the same thing.

Outback Power Inc. - Grid-Interactive

The Sunny Boy models, as I posted earlier, do not sound like they would work safely with motors, which would rule out fridges, freezers, and well pumps. I could care less about lights. The dedicated outlet is only marginally useful.

I looked at documentation on the Outback site, which has some confusing text, but I cannot find where they state their inverters will run, without batteries AND grid power. From the GTFX and GVFX specifications document, http://www.outbackpower.com/downloads/documents/gtfx_gvfx_series/ob_022013_gtfxgvfxseries_specsheet_lr.pdf

Our built in transfer switch automatically disconnects your loads from the utility grid and powers them from the inverter in the event of an outage, allowing you to continue using your solar and battery back-up power, unlike traditional grid-tie systems.

The marked text can be read a couple of ways but I think it means one needs batteries if the grid goes down.

The inverter manual did not mention anything on this subject that I could find. This page, Outback Power Inc. - Grid-Interactive has a diagram that shows batteries.

Is there a document on their website that has more details?

Later,
Dan

 

[westcliffe01]

Grundfos SQFlex Submersible Solar Well Pumps

Just to be clear, there are plenty of solutions that work for providing well water from solar. Generally speaking though, the flow rate does not equal a multi HP conventional well pump. But then the mode of operation is not the same either. One either installs an oversized accumulator, or installs a cistern with a float switch and the solar powered well pump can take its sweet time filling the cistern. When you need water (when pressure drops in the domestic line) then you have a much lower powered pump which lifts the water from the cistern into the house system and you could easily have a couple of thousand gals of water available if needed. Most wells in this area are around 500+ ft deep.

I am looking a building an off the grid home and have spent the last week looking at property in southern CO. There are plenty of people living this kind of life, the key thing is to configure the site/home for minimal energy demand in the first place. The site I am looking at is at 9000ft so no need for AC and has a high % of sunny days and the home will be built passive solar. All light fixtures will be LED. My home will not be very large, be almost entirely concrete (for thermal mass) and built into a south facing slope so only the southern side will be fully exposed and the east/west partially so.

I will also have a shop and that will be equipped with a diesel genset modified for CO-gen, thus recovering a lot of heat from the exhaust, coolant and oil. The primary heating system for the buildings will be water based radiant, in the slab with multiple circuits. Solar collectors will feed a buried/insulated cistern (installed under the grow beds in the greenhouse) and that in turn will als b fed by the co-gen system (when in use) as well as a diesel fired hot water heater. I have looked into all fuel sources and diesel is a common fuel for all my equipment, and I can buy it myself from many sources so I'm not held captive by 1 or 2 propane distributors. It also has a high energy density and I can transport it myself.

In my case this remote land is relatively cheap and the price for that is a lack of infrastructure and unreliable access (weather related) so for 3 months of the year it might take a arctic cat or snowmobile to get out to a maintained road. Conventional utilities are basically out of the question and the solution to that is part of the cost of building.

 

[TnAndy]

The GT/GV series is set to run on a specific voltage......12,24, 48 + a volt or two on the high side, and down a couple volts on the low side ( before they shut down due to low voltage ). Only way to do that is with a battery bank. Panel voltage will vary all over the place based on the amount of sun on the panels.

They are set up with a large positive and negative power lug on each that is fed from a battery bank ( thru a fused/breaker disconnect ), so you really don't have a way to feed in small wires from panels TO the inverter.

The setup is: Panels to charge controller ( where panel voltage is changed to match battery voltage, assuming you're using an MPPT controller, like the Outback FX series ), then battery, then inverter.....with the required fusing and disconnecting means between each component, and AC breakers on the output side.


The Radian, I have no experience with, and can't speak to how it works.

 

[TnAndy]

Grundfos SQFlex Submersible Solar Well Pumps

Just to be clear, there are plenty of solutions that work for providing well water from solar. Generally speaking though, the flow rate does not equal a multi HP conventional well pump. But then the mode of operation is not the same either. One either installs an oversized accumulator, or installs a cistern with a float switch and the solar powered well pump can take its sweet time filling the cistern. When you need water (when pressure drops in the domestic line) then you have a much lower powered pump which lifts the water from the cistern into the house system and you could easily have a couple of thousand gals of water available if needed. Most wells in this area are around 500+ ft deep.

Sounds like a real setup !

We use gravity fed spring water for our home. 3,000 gallons of storage tanks located up on the mountain near the spring.

 

[westcliffe01]

Solar Water Pumping Guide

Nice write up (guideline) regarding solar water pumping.

 

[rmorey]

Sounds like a real setup !

We use gravity fed spring water for our home. 3,000 gallons of storage tanks located up on the mountain near the spring.

I've been reading this thread with interest. We recently moved to a retirement home, 200 acres on a lake. Built a home and workshop, called the hydro folks, who told us that "hydro is $150,000 due south of you"!

After the adrenaline rush subsided, we researched, and installed an off grid 3.6kw (20 - 180 watt panels), 2 - FM80 Charge Controllers, with a pair of Magnum 4,000 watt inverters, 24 - 2v Trojan 1110 amp batteries, configured as 2 - 1110 amp strings (big box in the basement). All for around $25K. (sorry, no subsidies here). Our savings come in the form of no power bills ever. We also have an 8500 watt gas generator for those dull periods.

We have a 240 v submersible water pump, fridge, freezer, lights etc. Our daily consumption is about 150 amps dc, converting to, give or take, 4Kw.

With regards to the question of no power from the micros when the grid goes down, why wouldn't a small battery backup, say 4 - 6v batteries, 225 amp with a small charge controller/inverter work? Would be cheap to install (< $1k) and give you enough power to run water, freezer/fridge and some lites.

 

[dmccarty]

With regards to the question of no power from the micros when the grid goes down, why wouldn't a small battery backup, say 4 - 6v batteries, 225 amp with a small charge controller/inverter work? Would be cheap to install (< $1k) and give you enough power to run water, freezer/fridge and some lites.

In the solar class I took earlier in the year, we discussed if it was possible to trick the inverters into thinking there was grid power. We came up with the ideas of using batteries but it is going to depend on how the inverters determine a grid outage. The bottom line seems to be that you really need batteries when the grid goes down are you risk damaging equipment that is sensitive to power fluctuations.

Later,
Dan

 

[TnAndy]

I've not tried it with my system, nor will I unless the grid goes down and looks to be down a long time, maybe forever....( like an EMP event, or a solar flare, etc ), but I'm fairly sure I could rewire the micro inverter portion of my system to connect with the off grid portion of my system ( the hybrid Outbacks ) so I could utilize the whole 11kw, at least during sunny hours, since the Outback inverters put out as clean ( or better ) power as the utility input. 240v 60hz power is the same, no matter where it comes from.

 

[TnAndy]

I've been reading this thread with interest. We recently moved to a retirement home, 200 acres on a lake. Built a home and workshop, called the hydro folks, who told us that "hydro is $150,000 due south of you"!

After the adrenaline rush subsided, we researched, and installed an off grid 3.6kw (20 - 180 watt panels), 2 - FM80 Charge Controllers, with a pair of Magnum 4,000 watt inverters, 24 - 2v Trojan 1110 amp batteries, configured as 2 - 1110 amp strings (big box in the basement). All for around $25K. (sorry, no subsidies here). Our savings come in the form of no power bills ever. We also have an 8500 watt gas generator for those dull periods.

Not to mention the $100,000+ you didn't shell out to bring the power line to you. Your payback was about one second after you fired up the system !

With regards to the question of no power from the micros when the grid goes down, why wouldn't a small battery backup, say 4 - 6v batteries, 225 amp with a small charge controller/inverter work? Would be cheap to install (< $1k) and give you enough power to run water, freezer/fridge and some lites.

One would basically be building a larger UPS like those used on computers, charged by line power, and only used in grid down. The problem would be size of battery storage. You're not gonna run pump, freezer/fridge and lights TOO long off a 24v 225amp/hr battery setup....assuming 50% depth of battery discharge, by the time you convert it to AC, you're only looking at about 1/2kw/hr. Average US home use is about 30kw/hrs/day......you can see 1/2kw/hr isn't gonna go too awful far.

That is exactly the problem with those "solar generators" they sell for 2,000-3,000 bucks ( or more ).....they would lead you to believe you have 1500 to 2000watts of power like a small gasoline generator....which you do.....for about 20 minutes if using the max. Then the small panel setup they sell with it is going to take 2-3 days of sunny weather to let you do that again.

 

[SPYDERLK]

People need batteries because batteries are required to provide backup power when there is a power outage. People are shocked when the find out that a grid tied system is not usable during a power outage.
Later,
Dan

Oh me, I'm as confused as ever now! :confused2: my normal state.

So, no batteries, no good when power goes out? Maybe I should have some solar boys come give me explanation and estimate.

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

 

[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.