Solar Design with Geothermal.

[RiverFever]

Good Afternoon,

I'm in the beginning stages of designing my own Solar PV and Battery Backup system for our all electric home. In the summer/winter i would like to power our 4 ton variable stage geo unit and a heat pump water heater. We live in NNY. Depending on the weather outside i'd like to power a freezer as well. In the winter i can turn it off and just pack everything in a cooler outside and not worry about it. During the summer it's a different story.

Because our geo unit tonnage is rated for heat and not cooling our 4 ton unit can quickly cool off our house without a sweat., Normal load for the whole home A/C is around 11 to 1200 watts for 10-15 minutes and then ramps down to 700-800 watts to keep that set temp. During the winter our coldest month was January and we used close to 776 Kwhcal. For the whole year in heating we used 3240Kwh and in the summer our total for cooling is 390Kwh. My Geothermal electrical is 208/230/60/1. Would I need two 120v inverters in parallel? I plan on going with three EG4 lipo 48v batteries for a total of around 15.3 Kwh. I know it wont get me through the whole day but id like to have a 8-10 hour window to sustain off the battery if the grid goes down.

 

[Bobert]

Good Afternoon,

I'm in the beginning stages of designing my own Solar PV and Battery Backup system for our all electric home. In the summer/winter i would like to power our 4 ton variable stage geo unit and a heat pump water heater. We live in NNY. Depending on the weather outside i'd like to power a freezer as well. In the winter i can turn it off and just pack everything in a cooler outside and not worry about it. During the summer it's a different story.

Because our geo unit tonnage is rated for heat and not cooling our 4 ton unit can quickly cool off our house without a sweat., Normal load for the whole home A/C is around 11 to 1200 watts for 10-15 minutes and then ramps down to 700-800 watts to keep that set temp. During the winter our coldest month was January and we used close to 776 Kwhcal. For the whole year in heating we used 3240Kwh and in the summer our total for cooling is 390Kwh. My Geothermal electrical is 208/230/60/1. Would I need two 120v inverters in parallel? I plan on going with three EG4 lipo 48v batteries for a total of around 15.3 Kwh. I know it wont get me through the whole day but id like to have a 8-10 hour window to sustain off the battery if the grid goes down.

Hi welcome. I am assuming that NNY refers to northern New York. That is where I live. What size solar array are you thinking of? Do you know what your peak power consumption would be in one hour? How much power management are you willing to employ? The trick in nothtern Ny is the long dark winters. They make solar very challenging. If you want to be certain of having power you will probably need to have some sort of a generator in the mix. Fortunately a decent size battery setup can greatly improve the efficiency of your generator. Unfortunately a solar system that just barely works fo get you by on the rare sunny days when there is no snow on the panels in December and January will actually be to big in the summer. Solar only is a tough go up here.

 

[Bobert]

Depending on the weather outside i'd like to power a freezer as well. In the winter i can turn it off and just pack everything in a cooler outside and not worry about it. During the summer it's a different story.

We have our freezer on an unheated north facing porch. The freezer essentially never runs in winter and as you probably already know there are times when the temperatures outside the freezer are much colder than the temperature inside the freezer.

 

[12VoltInstalls]

Depending on the weather outside i'd like to power a freezer as well.

We have our freezer on an unheated north facing porch. The freezer essentially never runs in winter

That was going to be my suggestion

just pack everything in a cooler outside

I’m in northern Vermont. Not only would a cooler drive me nuts but wildlife: they’re real

can quickly cool off our house without a sweat.

That’s very funny ?

Would I need two 120v inverters in parallel

Two of the right units. Basically a split-phase single 120/240 unit or a pair intended to ‘stack.’

Basically you want to feed a typically probably 200A load center just like the grid would do.

sustain off the battery if the grid goes down.

So you probably need to find out what inspections/compliance is necessary (specifically UL1741) to be approved regardless of gridtie sellback or not. I don’t know how flexible NY is but I’d imagine not much.

The trick in nothtern Ny is the long dark winters.

No science but imho: three to four times the panels you ‘need’ in summer will be sufficient some/most of the time in winter.

sunny days when there is no snow on the panels in December and January will actually be to big in the summer. Solar only is a tough go up here.

You ‘lose’ a bit, but orientation of the panels SSE and SSW in two arrays, plus putting the panels vertical in winter will have minimal extra “loss” but panels will never be snow covered. Wicked convenient.
“Solar In The North”

EDIT: I’m overpaneled in summer by enough (due to planning for winter) that I don’t need to tilt in summer, just leave them as is. Running aircon may make you want 30* for the summer but if you panel for winter - considering a/c is basically unneeded at our latitude- you may not need to, either. Once running? You’ll know…

 

[DThames]

We are total electric with an older heat pump and the starting amps would require a huge inverter, so we have not even went that route. But the heating load (even with a good heat pump) will take down a battery bank fairly quickly. You could reduce that load if you would set the thermostat to a lower (less comfortable) level to extend battery life. We have a large portable propane heater for emergency use.

Some inverters are 240v/120 split phase, Schneider example. Some inverters are 120v with the ability to "stack" and configure more than one into a split phase and/or a larger system, Phocos example. Proper sizing of the inverter for your load needs is something to carefully consider. I would guess the house heat and the water heat are both things that could greatly inflate what would be somewhat typical of a "critical loads" system. You are more in the whole house size range, I would think.

Do you have space to put up as many solar panels as you see fit?

 

[RiverFever]

We are total electric with an older heat pump and the starting amps would require a huge inverter, so we have not even went that route. But the heating load (even with a good heat pump) will take down a battery bank fairly quickly. You could reduce that load if you would set the thermostat to a lower (less comfortable) level to extend battery life. We have a large portable propane heater for emergency use.

Some inverters are 240v/120 split phase, Schneider example. Some inverters are 120v with the ability to "stack" and configure more than one into a split phase and/or a larger system, Phocos example. Proper sizing of the inverter for your load needs is something to carefully consider. I would guess the house heat and the water heat are both things that could greatly inflate what would be somewhat typical of a "critical loads" system. You are more in the whole house size range, I would think.

Do you have space to put up as many solar panels as you see fit?

Hi welcome. I am assuming that NNY refers to northern New York. That is where I live. What size solar array are you thinking of? Do you know what your peak power consumption would be in one hour? How much power management are you willing to employ? The trick in nothtern Ny is the long dark winters. They make solar very challenging. If you want to be certain of having power you will probably need to have some sort of a generator in the mix. Fortunately a decent size battery setup can greatly improve the efficiency of your generator. Unfortunately a solar system that just barely works fo get you by on the rare sunny days when there is no snow on the panels in December and January will actually be to big in the summer. Solar only is a tough go up

Hey there. Thanks for all the replies. The geo heat pump has a soft start option built in , so the locked rotor amps wont nearly be as high. My heat pump water heater has the same thing. I want to hook my geo, heat pump hot water heater and a small fridge to the solar inverter at all times and keep the battery's charged through out the day with the solar and use the grid at night if the solar didn't charge the batteries enough. So i want to use the batteries/solar if I can and use the AC tie in to the inverter if the system cant keep up with the demand. Does that make sense?

I'm looking at getting three lipo4 5.3? Wh batteries. That should last me the evening hours. My total peak wattage would be just be about 3000w with everything running full tilt, but that's rare. Total average wattage with those three systems is around 1500w. Geothermal and heat pump water heater are amazing for low electric consumption.

 

[RiverFever]

We are total electric with an older heat pump and the starting amps would require a huge inverter, so we have not even went that route. But the heating load (even with a good heat pump) will take down a battery bank fairly quickly. You could reduce that load if you would set the thermostat to a lower (less comfortable) level to extend battery life. We have a large portable propane heater for emergency use.

Some inverters are 240v/120 split phase, Schneider example. Some inverters are 120v with the ability to "stack" and configure more than one into a split phase and/or a larger system, Phocos example. Proper sizing of the inverter for your load needs is something to carefully consider. I would guess the house heat and the water heat are both things that could greatly inflate what would be somewhat typical of a "critical loads" system. You are more in the whole house size range, I would think.

Do you have space to put up as many solar panels as you see fit?

I sure do. I plan on starting a southern facing ground mount. My houses roof points east and west.

 

[DThames]

Hey there. Thanks for all the replies. The geo heat pump has a soft start option built in , so the locked rotor amps wont nearly be as high. My heat pump water heater has the same thing. I want to hook my geo, heat pump hot water heater and a small fridge to the solar inverter at all times and keep the battery's charged through out the day with the solar and use the grid at night if the solar didn't charge the batteries enough. So i want to use the batteries/solar if I can and use the AC tie in to the inverter if the system cant keep up with the demand. Does that make sense?

I'm looking at getting three lipo4 5.3? Wh batteries. That should last me the evening hours. My total peak wattage would be just be about 3000w with everything running full tilt, but that's rare. Total average wattage with those three systems is around 1500w. Geothermal and heat pump water heater are amazing for low electric consumption.

Look at that Phocos AnyGrid product. They have a couple of hours of video on Youtube explaining some of the functions/features of the product. It will allow you to run your loads off solar and blend more power in from the grid, if the sun is not great, in order to use the sun as much as you can. It can supplement battery with the solar or not, if you want to hold the battery for after sundown. Anyway, lots of options to be ready for Off Grid use but be running off of what solar you can produce. So you could put in the inverters, batteries, some panels.....then later add more panels of you want to reduced further your daytime grid demand. 2 of those 6.5kw inverters in a 240v/120v splitphase setup could run off the batteries you described, both running from one battery bank.