diy solar

diy solar

Large system

C

Coolthings

New Member
Joined
Aug 30, 2021
Messages
6
Hello,

I have a 20 unit building. Need guidance on a system that I can build off grid. To power the needs of the guests. Everything here is electric. Heat,air conditioning , water heater. I have tracked my monthly usage. Just not sure about the usage surge from all the appliances. Thanks in advance
 
iamrich said:
What is powering the building now? I don't think a system of this size and "Beginner's Corner" go hand in hand. :)
Click to expand...
Regular public utilities offers their fine overpriced service. i am the beginner. But happy to jump right on in. The range of kWh is 12000 summer to 21000 winter that’s a huge range I know. If I am off grid I know I will need the batteries and a good amount of panels. The thing I don’t understand is how it effects when there is a surge with the heater or air conditioners all running at same time. Mornings would be the water heaters higher usage
 
Coolthings said:
Regular public utilities offers their fine overpriced service. i am the beginner. But happy to jump right on in. The range of kWh is 12000 summer to 21000 winter that’s a huge range I know. If I am off grid I know I will need the batteries and a good amount of panels. The thing I don’t understand is how it effects when there is a surge with the heater or air conditioners all running at same time. Mornings would be the water heaters higher usage
Click to expand...

I would not go complete separated off-grid. That would be extreme big and expensive system.
off-grid_separated.jpg

Maybe off-grid with grid support ?
off-grid.jpg

Or a grid-tie
grid_tie.jpg

or an AC Coupled system to lower the grid usage ?
AC_coupled.jpg

Every of this systems have pros and cons. But all are cheaper than separated off-grid.

21000kWh / month ?
 
Last edited:
There will be no easy way to predict what appliances will be used at the same time. So you would have to assume everything is running at the same time for a worse case scenario. Then you have to factor in night usage and bad weather. As others have said, this is probably not practical and not a beginner project. IMO the best option is a grid-tie system.
 
Texas-Mark said:
There will be no easy way to predict what appliances will be used at the same time. So you would have to assume everything is running at the same time for a worse case scenario. Then you have to factor in night usage and bad weather. As others have said, this is probably not practical and not a beginner project. IMO the best option is a grid-tie system.
Click to expand...
Grid-tie pros:
- cheap and easy
- can sell power to grid
- or with limiter only produce for inner usage
Grid-tie cons:
- If no sun at that moment then no cost reduction (like every evening to morning and when lot of clouds)
- with limiter if current load is smaller than it can produce then a lot of wasted Wh (power not made).
- in a blackout full darkness
 
mrzed001 said:
- in a blackout full darkness
Click to expand...
Grid tie backup is feasible for way way less than the cost of a full off-grid set up. But this is no beginner project so kinda pointless to speculate. With the energy consumption mentioned this is solar farm scale.

Suggest consulting with an industrial energy supply professional.
 
wattmatters said:
Grid tie backup is feasible for way way less than the cost of a full off-grid set up. But this is no beginner project so kinda pointless to speculate. With the energy consumption mentioned this is solar farm scale.

Suggest consulting with an industrial energy supply professional.
Click to expand...

Yes an 500kWp solar power plant produces 24.000 kWh in winter months (more or less on different locations).

I think OP does not know where to start and what are the possibilities.
And frankly I would not be surprised if one or more company would sent he off on some wild-goose chase
 
mrzed001 said:
I would not be surprised if one or more company would sent he off on some wild-goose chase
Click to expand...
I would be surprised if these installers DIDN’T send him off on a wild goose chase, or more likely sell him something that benefits them to install but either doesn’t meet all his goals or costs way more than necessary.

This one of those times where a mech engineer guy/gal with EE’s in his office might actually save money- or at least design a system that both works and makes economic sense.

Grid-tie > battery bank > generator backup might be the least expensive per year aged over 25 years
 
Last edited:
12VoltInstalls said:
I would be surprised if these installers DIDN’T send him off on a wild goose chase

This one of those times where a mech engineer guy/gal with EE’s in his office might actually save money- or at least design a system that both works snd makes economic sense.

Grid-tie > battery bank > generator backup might be the least expensive per year aged over 25 years
Click to expand...

I would go with a Grid-tie or hybrid system (and sell excess power to grid).
1, Grid-tie mainly, and if needed an Off-grid with battery to have UPS power outlets or
2, Grid-tie mainly, and an AC coupled battery solution to store some excess power and use it at night (more expensive)
To make the whole building UPS ... that is big.
Almost like this Victron container big:

Backup generator is always an option but that also only to UPS outlets. Not the whole house.
 
mrzed001 said:
would go with a Grid-tie or hybrid system (and sell excess power to grid).
Click to expand...
That is assuming there is any excess to sell without a ginormous array. Not sure what "a building with 20 units" actually consists of.
 
Texas-Mark said:
That is assuming there is any excess to sell without a ginormous array. Not sure what "a building with 20 units" actually consists of.
Click to expand...

I do not know either :)
Just guessing. But even if they are flats then by day the consumption is much lower (gone to work, school) than by evening.
Some cost calculations needed to know when and how many kW is used. And the power price there.
 
12VoltInstalls said:
^^^describes guest rooms to me
Click to expand...
One Ptac heater air conditioner. A few lights , microwave, small fridge and a coffee maker all typical items you find in a hotel room, I also have 10 electric 80 gallon water heaters on 24/7 I had a company come out to survey and it didn’t seem right what they were saying. One important thing is that when the power goes out so do the guests room I like to avoid that. My regular electrician suggested a hybrid on grid solution where I control it with a breaker in which if I need power I turn on the grid. Or if a power out I can turn off the grid and use my batteries
 
Starting point would be consumption with everything running...need to see what your surge draw is when a/c units start up...this will give you a look at what your minimum system requirements ...btw what is your service voltage 480v 3p?
 
Roqm said:
Starting point would be consumption with everything running...need to see what your surge draw is when a/c units start up...this will give you a look at what your minimum system requirements ...btw what is your service voltage 480v 3p?
Click to expand...
The ptac units are all 1 phase cooling is Rated 778 watts heating 3.5kW voltage is 208-230 according to the spec sheet
 
Coolthings said:
average of 15,500kWh per month
Click to expand...
517kWh per day
Assuming 5 hrs solar, thats 517,000Wh / 5h = 103,400W of solar.

If you have 350W panels, that would take 295 solar panels. How much room do you have for panels?

>>google search
Modern solar panels are around 15% efficient, so that works out to approximately 150 watts per square meter, or 15 watts per square foot.

103,400W / 15W / sqft = 6893sqft if densely packed.

Just messing with numbers.
 
You must log in or register to reply here.

Similar threads

R
New solar system /w used JA Solar 315w panels
Replies
2
Views
218
rrleesb
R
WorldwideDave
Getting hot outside - system sizing question
Replies
15
Views
351
WorldwideDave
WorldwideDave
R
Software to monitor my batteries wirelessly and display data in the house?
Replies
1
Views
218
42OhmsPA
4
M
Is 48V good for an Apartment?
2
Replies
22
Views
613
mgentile7
M
A
4000 kWh usage per month
Replies
15
Views
560
wpns
W
Back
Top