Enphase M250 Specs for off-grid, tips and tricks and results

[SunEagle]

Hi Solarddy, Syedamerali, and Everyone else.

I'm looking at the enphase M250s for use in a 1.kW RV based system. I've found this discussion very interesting. Has anyone else progressed with this islanded M250 concept recently? I'm looking at a 240VAC UPS modification to generate my "utility signal" with some form up "dump load" to deal with excess generation from the M250s.

Any update on progress/failures/tip/etc.. would be greatly appreciated.

Thank you,
-M

Unfortunately a UPS will not be able to mimic a "grid connection" to make your micro inverters work. You need a lot more than just the correct voltage and frequency to fool any grid tie inverter that it is connected to a working "grid".

[ButchDeal]

Hi Solarddy, Syedamerali, and Everyone else.

I'm looking at the enphase M250s for use in a 1.kW RV based system. I've found this discussion very interesting. Has anyone else progressed with this islanded M250 concept recently? I'm looking at a 240VAC UPS modification to generate my "utility signal" with some form up "dump load" to deal with excess generation from the M250s.

Any update on progress/failures/tip/etc.. would be greatly appreciated.

Thank you,
-M

This is a huge mistake. An AC coupled system is very complex and UPS systems are not designed or likely going to work in this configuration. They have no way to control the micros or the dump load. Worse UPS has an AC input and an AC output. They do not feed power out the input or take power in on the input side. This configuration will not work with AC coupling like a bymodal inverter which has two AC connections but canbfeed AC out on both and one is usually bidirectional.

[sensij]

I'm looking at the enphase M250s for use in a 1.kW RV based system.

Why would want to use microinverters? A normal charge controller (if you have batteries) works well. If you have enough shade that you think you need microinverters, you need to stop and rethink what you are doing.

[michaellong30]

Hi Solarddy, Syedamerali, and Everyone else.

I'm looking at the enphase M250s for use in a 1.kW RV based system. I've found this discussion very interesting. Has anyone else progressed with this islanded M250 concept recently? I'm looking at a 240VAC UPS modification to generate my "utility signal" with some form up "dump load" to deal with excess generation from the M250s.

Any update on progress/failures/tip/etc.. would be greatly appreciated.

Thank you,
-M

[SunEagle]

yeah, no (less than half earth):

http://ccar.colorado.edu/asen5050/projects/projects_2001/benoit/solar_irradiance_on_mars.htm

http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html

Mercury, now (at least the half of the planet facing the sun) YES, (6.6 times as much as earth)
http://nssdc.gsfc.nasa.gov/planetary...rcuryfact.html

Now Mercury sounds very bright and very hot.

[lkruper]

yeah, no (less than half earth):

http://ccar.colorado.edu/asen5050/projects/projects_2001/benoit/solar_irradiance_on_mars.htm

http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html

Mercury, now (at least the half of the planet facing the sun) YES, (6.6 times as much as earth)
http://nssdc.gsfc.nasa.gov/planetary...rcuryfact.html

!!!!

[ButchDeal]

I think Mars might be better.

yeah, no (less than half earth):

http://ccar.colorado.edu/asen5050/projects/projects_2001/benoit/solar_irradiance_on_mars.htm

http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html

Mercury, now (at least the half of the planet facing the sun) YES, (6.6 times as much as earth)

http://nssdc.gsfc.nasa.gov/planetary/factsheet/mercuryfact.html

[lkruper]

We are all interested to see the pvoutput graphs of the solar community you set up there with Solarddy.

I think Mars might be better.

[J.P.M.]

you mean you are not planning to move

Not anymore. Too old and too lazy. Besides, IMO, I'm now pretty much in the belly of the beast for about the best weather on the planet.

[ButchDeal]

Just adding some information for those with perhaps some curiosity. I forgot to add the usual "Take what you want of the above. Scrap the rest." My bad.

you mean you are not planning to move

[J.P.M.]

We are all interested to see the pvoutput graphs of the solar community you set up there with Solarddy.

Just adding some information for those with perhaps some curiosity. I forgot to add the usual "Take what you want of the above. Scrap the rest." My bad.

[ButchDeal]

There's a bit more than anecdotal evidence that it's not rained in most places there as long as records have been kept, and the arch. evidence is that it hasn't ever rained in some spots.

Just sayin'.

We are all interested to see the pvoutput graphs of the solar community you set up there with Solarddy.

[J.P.M.]

Based on what I have found there isn't anywhere on earth that has perfect solar sunshine every day of the year. Even the sunniest (supposed to be Yuma, Arizona) may get > 4000h of annual sunshine but that is still about 91% of the time. So it really doesn't matter where you live except maybe in orbit to expect continuous sunlight for pv to produce.

I understand the attraction that solarddy has for a micro inverter system but without another way to generate or purchase power (batteries, gen set, grid, hydro, wind, etc) when the sun isn't shining I will say your electrical equipment will not run.

As it turns out, and FWIW (maybe), Tucson, MAY edge Yuma out by a nose with a clearness index - common symbol "Kt" = = (Annual global horiz. irrad./Extraterrestrial "horiz."rad, at same loc. above the atmos.) of ~ .653, vs Yuma's ~ .630. More than a few places in NM come close to that # like Las Cruces (.656), or Santa Fe (.652). But that may be separating fly fraas from pepper.

However, looking outside the U.S, places in the Atacama desert in Chile ( ~ 2,500 m above sea level) probably have Kt values exceeding .80 or so. Kind of a harsh climate however. There's a bit more than anecdotal evidence that it's not rained in most places there as long as records have been kept, and the arch. evidence is that it hasn't ever rained in some spots.

Just sayin'.

[SunEagle]

So you only have a grid tie micro system with no battery and are comparing it to an off grid system with battery and generator...
yes grid tie micros are pretty easy though not as simple as legos, BUT have absolutely no backup capability.

What everyone here (including you) is talking about is a system that you can use RIGHT NOW off grid called AC coupling. It uses a second inverter (like you keep mentioning Magnasine) and batteries to allow ANY (yes including micros) GRID Tie system to work off grid. This is a pretty complex install and the batteries and dual inverter system has a lot of configuration and sizing to get right.

Further you suggestion that everyone move to the desert so they can have more sun and not have to worry about cloudy days in temperate climates in the US seems at best ridiculous. A suggestion of Dallas TX seems just as ludicrous , a quick search of pvoutput shows this site just north of Dallas showing clear weather issues on 10/22- 10/25 http://pvoutput.org/list.jsp?p=0&id=...=29366&v=3&s=1 .

Based on what I have found there isn't anywhere on earth that has perfect solar sunshine every day of the year. Even the sunniest (supposed to be Yuma, Arizona) may get > 4000h of annual sunshine but that is still about 91% of the time. So it really doesn't matter where you live except maybe in orbit to expect continuous sunlight for pv to produce.

I understand the attraction that solarddy has for a micro inverter system but without another way to generate or purchase power (batteries, gen set, grid, hydro, wind, etc) when the sun isn't shining I will say your electrical equipment will not run.

[inetdog]

My favorite battery is: Telcomm batteries! I bet you thought I was gonna say Walmart! http://www.northstarbattery.com/batt...opzv/index.php ooo they are expensive but with a 20 year lifespan and up to 3000Ah wow.

That website seems to be down at the moment (or forever?).
But the Google cache shows that these are, as stated, telecom batteries. They are designed primarily for emergency power and so are engineered for long life in float service with minimal maintenance requirements. They can also deliver a very high current for their AH rating.
Sunking has talked about this kind of battery in the past, they are nothing new.
Their cycle life in a a repeated discharge situation is low (1500 cycles would be about 4 years) and their tolerance for spending a long time at a Partial State Of Charge (PSOC) is unknown but probably not good. They do apparently have low self-discharge, so once charged fully they can tolerate being on their own for awhile. Again great for backup service but not for RE.

Have you worked out the cost per kWh of storage? These will be very expensive batteries, I fear.