Sponsored

Simple Off Grid Solar Option?

OP
OP

Bobthebuilder352

Well-Known Member
Joined
Nov 12, 2020
Threads
13
Messages
346
Reaction score
237
Location
Florida
Vehicles
Kubota
Occupation
Farmer
Now I'm curious. Why in the world do you need a 50kW system?
10ton+ HVAC is a huge drain
I was just looking and got one quote for a 37kW install. I would cover 70% of my monthly usage.
I don’t know much about solar as most on here
what was your quote and what was the battery system?
Sponsored

 

RivianXpress

Well-Known Member
Joined
Nov 17, 2020
Threads
89
Messages
778
Reaction score
1,432
Location
West Coast
Vehicles
R1T, Sprinter, TE300i, R1250GSA, KTM 500, 790
Occupation
Retired Engineer
 

RivianXpress

Well-Known Member
Joined
Nov 17, 2020
Threads
89
Messages
778
Reaction score
1,432
Location
West Coast
Vehicles
R1T, Sprinter, TE300i, R1250GSA, KTM 500, 790
Occupation
Retired Engineer
Will is one smart kid...

 

ajdelange

Well-Known Member
First Name
A. J.
Joined
Aug 1, 2019
Threads
9
Messages
2,883
Reaction score
2,317
Location
Virginia/Quebec
Vehicles
Tesla XLR+2019, Lexus, Landcruiser, R1T
Occupation
EE Retired
I was just looking and got one quote for a 37kW install. I would cover 70% of my monthly usage.
I don’t know much about solar as most on here
For starters you need to appreciate that the amount of sun you get in the winter is much less than the amount you get in the summer. This is due both to the sun's ephemeris and weather conditions - both depending on location. A 37 kW system produces 37 kWh per hour of Full Sun Equivalent (FSE). In the summertime you may get 5 hours of FSE, in the winter 3. Calling the average 4 a 37 kW system would produce, on average, 148 kWh per day.

You list Phoenixville (I assume Pa) as your location and indicate that this is mainly for AC as winter heat is from gas. Let's give you 5 hours average daily summertime FSE. That's 185 kWh per day which is a lot of energy. The average consumption in the US is about 16 kWh/da/1000 ft^2. For a 4600 ft^2 house that's about 74 kWh/day which is about what I pull in a house of about 4500 ft^2.

I ran an 8 ton W/W heat pump June through August on about 3.5 MWh. Total consumption, including several other A/A heat pumps (10 - 12 tons) was 7.91 MW; average consumption 82.6 kWh per day. 79.6% of this was covered by a 14.5 kW solar array. At 185 kWh per day over 90 days you would collect about 16.6 MWh. That's double what I use for a similar sized house.

All these numbers say that it appears that a 37 kW system is way oversized for what you need. Now that is said, of course, without knowing details of your particular requirements.

Another big factor in a system with such huge load is that were I to try to cover my summertime demand (average 3.44 kw) for the 24 -5 = 19 hours of non FSE I would need 19*3.44 = 65 kWh of storage which is about 5 Powerwalls. This is with no buffering i.e. it assumes that you get your 5 hrs FSE every day. If you need to cover one day of no sunshine you would need twice as many, to cover three days, three times as many etc. Have you looked at the costs of those things?

Bottom line here is that I believe that you are, in looking at 37 - 50 kW systems, looking at systems much bigger than you need. Even so, assuming that your actual requirements are similar to mine based on approximately the same latitude, weather and square footage, you are going to have challenges with storage. Rather than shell out the tens of thousands for dozens of Powerwalls you will do much better to back up your system with a generator. Tesla recommends this and it is, AFAIK, what most people with off grid solar systems wind up doing.
 

ajdelange

Well-Known Member
First Name
A. J.
Joined
Aug 1, 2019
Threads
9
Messages
2,883
Reaction score
2,317
Location
Virginia/Quebec
Vehicles
Tesla XLR+2019, Lexus, Landcruiser, R1T
Occupation
EE Retired
That would have to be a MASSIVE carport to have a roof large enough to support 11.5kW of panels.... unless you only want to offset some but not all of your charging needs — then it’s just a matter of how much you expect.
I got it onto 35 x 30'. Now I admit readily that the project is orders of magnitude greater than what I had in mind when I decided to build a charging carport. It transmogrified into a 3 car garage.
 

Sponsored

CommodoreAmiga

Well-Known Member
Joined
Dec 30, 2020
Threads
39
Messages
4,104
Reaction score
7,706
Location
INACTIVE
Vehicles
INACTIVE
I got it onto 35 x 30'. Now I admit readily that the project is orders of magnitude greater than what I had in mind when I decided to build a charging carport. It transmogrified into a 3 car garage.
Yea, that's a massive carport. The average garage is between 18x20 to 20x25. Assuming a typical 6/12 pitch and 1' overhangs, that's only 500 - 674 sqft of total roof surface.

You didn't specify if your 35x30' is the land area, or the roof surface area... But that's either 1,050 sqft or 1,338 sqft -- so more that double the average garage.

Cool for you, no doubt. But not representative of what the average person could acheive.
 

ajdelange

Well-Known Member
First Name
A. J.
Joined
Aug 1, 2019
Threads
9
Messages
2,883
Reaction score
2,317
Location
Virginia/Quebec
Vehicles
Tesla XLR+2019, Lexus, Landcruiser, R1T
Occupation
EE Retired
That's the facet area, not the projected area. The factory will build trusses at whatever pitch you want so these are at the optimum pitch for annual solar collection. The size of the roof required to support the panels made it easy to fit a roomy (accommodate CT with ease) 3 car garage with workshop under it. Even so, 12 kW is quite marginal. Summertime insolation grants about 60 kWh per day (120 - 150 miles added range) and wintertime about 36 (72 - 90 miles) per day. Folks need to appreciate that it takes a lot of panels to charge one of these trucks.

One could do a real carport (what I had in mind originally) but it would be necessary to have supplemental panels on frames on the lawn. In fact I may wind up doing that with what I have on the garage now.
Sponsored

 
 




Top