I have a good friend who wants to put in a 20 KW system, on a new house and looking to do it right. He has been reading a bunch as I have but wants the best equipment available at a reasonable price. He plans to be off the grid so needs batteries and is willing to spend what it takes to do it right. Does anyone out there want to help or offer advice? When he asked me, I said I know what I do know, but don't know what I don't know! I feel there are many out there that might have great ideas, know of good products, and have the latest info. I told him I wish this site had a Will Prowse-approved link for a great package or the components to make one.
New System Whole House Near LaCrosse WI
- Thread starter TRW
- Start date
BentleyJ
Solar Wizard
Could you please be more specific. 20kW of what? Solar panels, Inverter output. To be completely off grid it is absolutely necessary to have an accurate energy usage audit or in the case of a new house with no history its going to require adding up all the electrical demand and deciding how many items will be used at the same time as well as how much is needed over a 24hr, weekly, monthly basis for both summer and winter.
Then you have to decide how many days of battery back up is necessary for normal weather conditions that may include multiple cloudy days. Being off grid, some kind of emergency, diesel, gasoline, propane or natural gas generator is highly recommended.
Then you have to decide how many days of battery back up is necessary for normal weather conditions that may include multiple cloudy days. Being off grid, some kind of emergency, diesel, gasoline, propane or natural gas generator is highly recommended.
Thanks for your quick reply and follow-up questions. The expected load is less than 1000 KW for a month, the biggest load will be a two KW heat pump, and most major appliances will be gas. He has a large roof and can go with close to 30Kw of panels if needed, and might as he is hoping to charge an electric vehicle. He intends to have an LP gas backup generator to handle all possible needs but hopes not to need it often. The main source of heat will be an outdoor wood furnace. His plan is to be comfortable but will not panic if his capacity does not fully meet his needs.
PreppenWolf
Solar Addict
- Joined
- Oct 10, 2022
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- 930
Here are the Sunny vs cloudy days and snowfall.
Thanks for the input, lots of obstacles including night fall! We will make it work as we have others with working systems, but none optimal, and that is what he is looking for.
BentleyJ
Solar Wizard
If you wish we can resume tomorrow starting with a full energy usage estimate and then start sizing the system.
That is the plan, He does not plan to start until mid-summer at this point, the roof it is going on is not built yet. Where in Ministota is he? My friend will pay for whatever help we need, just not sure how much that is at this point.
I have a busy day tomorrow but will be glad to pick back up in the evening. I will get the electrical consumption he has had for the last year at his current residence.
I will be busy all day until late tonight, but the total electrical demand will be just over 1000 KW a month, he plans to expand that to 1500 a month when the sun shines and can use the excess on water heating or space heating. In addition to that eventually include things like charging an electric vehicle.
Send me his info and we can talk with him. Thanks for the reply.
Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 20,789
1000 kWh/month is 33 kWh/day. Summer or winter? In summer, can make that with about 5kW of PV.
Room for 30kW of panels, I like the sound of that.
I like SMA, of course. 30kW of panels would be a good fit for 4 Sunny Boys if all one orientation, maybe 3 Sunny Boys if multiple orientations and well distributed. Two Sunny Islands, three if he wants 3-phase.
on eBay, 2x SI-6048 is $5k to $6k. 3x SB 7.7 -41 , don't see on eBay but from StellaVolta $5k (a pair of SI would be $7k from them.)
Battery, if lithium DIY, should have REC BMS. Don't know if any compatible server rack units yet. SMA's recommended list are more expensive, but might be the right fit for him.
Having so much PV means system should be programmed for the reduced charge current you want (maybe for lithium, BMS takes care of that, but using lead-acid I had to reduce from default.) Battery will charge steadily, and frequency-shift is used to adjust PV production to match load.
Roof, if that is where PV is going, good time to put in standoffs and flashing.
Room for 30kW of panels, I like the sound of that.
I like SMA, of course. 30kW of panels would be a good fit for 4 Sunny Boys if all one orientation, maybe 3 Sunny Boys if multiple orientations and well distributed. Two Sunny Islands, three if he wants 3-phase.
on eBay, 2x SI-6048 is $5k to $6k. 3x SB 7.7 -41 , don't see on eBay but from StellaVolta $5k (a pair of SI would be $7k from them.)
Battery, if lithium DIY, should have REC BMS. Don't know if any compatible server rack units yet. SMA's recommended list are more expensive, but might be the right fit for him.
Having so much PV means system should be programmed for the reduced charge current you want (maybe for lithium, BMS takes care of that, but using lead-acid I had to reduce from default.) Battery will charge steadily, and frequency-shift is used to adjust PV production to match load.
Roof, if that is where PV is going, good time to put in standoffs and flashing.
Zwy
Emperor Of Solar
I live almost straight west of Lacrosse about 90 miles away as the crow flies, I go fishing there now and then. There is a reason I went with a PV mount that tilts to 65 degrees from vertical in winter.
Zwy
Emperor Of Solar
In the country or in Lacrosse? Along the river? I'd forget a roof mount if possible, the snow sticks too much to make it worthwhile here. The sun might be shining but with low temps the snow will not melt or slide off. In a neighboring town there is a roof mount on a large shop building, all panels still covered as of Saturday with about 5 inches of snow. It has been that way since the cold snap since the last snow a week ago. The city put in a couple of grid tied array's to cover electrical needs for the sewer plant. Fixed ground mounts, and the snow takes some time to clear the panels.
If he wants to drive down and see what I have done, he is more than welcome. I'm 90 miles away.
Thanks for the info and reply! His load does not vary a great deal, but a hot summer day is the maximum load he just insists he will expand up to what he can produce, like charging his vehicle and maybe some space heating. Yes, this will be a roof installation, on a standing seam roof, would there be an advantage to standoffs in that case? Thanks for the specific details, we will study that info.
We may do that, this will be in the country, 10 miles from the river, and this will be an ideal application for a proper angle roof. Thanks a bunch for the offer, send me a message if you are comfortable with it. You raise a great question on the snow, and I know what you mean about melting off, but this is an issue we need to figure out.
Thanks, I see that PM now, I will keep this thread informed as this progresses, he is taking a careful approach and might not get started until late summer.
BushMan2000U
New Member
Just Remember that if you go with SMA the Sunny Boys need to be set to OFF GRID. Also i have found that Trophy Battery (Dan Keaton), has checked with his engineers and tell me that his batteries work with the Sunny Islands Com Protocol in a closed loop.
