Add more Solar Panels to existing Grid Tied System.

 
ColdHouse
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Post by ColdHouse » Mon. Apr. 29, 2024 8:43 am

Looking to put DIY Solar on my Fifth Wheel with DIY battery backup.
I want to be able to plug my house into the camper to a dedicated panel while camper is not in use so a portion of my house is off grid and run off my camper Solar & Batteries.

It would be wise if possible to have the system plug and play expandable. So if I can only reasonably put x number of panels on the RV, I can come home and plug into Y number of panels at the home before connecting to my dedicated circuit.

Any and all input appreciated!


 
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Post by nut » Mon. Apr. 29, 2024 8:54 am

Might be better asking at the forum H suggested.

 
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Post by Hootyburra » Mon. Apr. 29, 2024 8:42 pm

You need to start with load calculations, maximum sustained loads, inrush current on items like compressors or well pumps and how long you want to power said loads before good advice can be given on inverters and battery bank size.

Do you want to be able to run in sync with your existing grid tie system (AC coupling) or disconnect the existing system with the flip of a transfer switch and power from your DIY system?
The latter will allow for less costly inverters / AIOs since you don't need the fancy bells and whistles.
That leads to the next question, do you want a modular component based system (separate inverter, solar charge controllers) or an all in one approach (everything in one box?

Batteries - will you be able to protect them from freezing? If yes go with LiFePo4. You could enclose them and in an insulated cabinet and keep them above freezing with heat mats / pads, some off the shelf batteries are doing this. If you can't keep them above freezing you need to use lead acid batteries.

Solar panels - go for the largest you can manage and figure out the optimal width / length based on your trailer length and panel mounting orientation.
Look at some photos of DC solar trailers for ideas on mounting. I've seen some of your creations, you'll have no problem coming up with a great mount.
Combining arrays can be done multiple ways depending how each array is wired and what the specs for your mppt are.

That should be enough to get you thinking.

 
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Post by Hootyburra » Mon. Apr. 29, 2024 8:44 pm

nut wrote:
Mon. Apr. 29, 2024 8:54 am
Might be better asking at the forum H suggested.
Agreed.
I'll offer as much advice and knowledge as I can here.

 
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Post by Hootyburra » Mon. Apr. 29, 2024 9:18 pm

So this was just shared on the other forum. I think it's a bit on the expensive side knowing what I have in my system but I think it's just awesome they are using the same AIO inverter I'm using and the same brand generator.

Coldhouse, it may give you some ideas.
https://shop.rpssolarpumps.com/products/off-grid- ... 0180694171

 
ColdHouse
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Post by ColdHouse » Tue. Apr. 30, 2024 4:19 am

Hootyburra wrote:
Mon. Apr. 29, 2024 8:42 pm
You need to start with load calculations, maximum sustained loads, inrush current on items like compressors or well pumps and how long you want to power said loads before good advice can be given on inverters and battery bank size.

Do you want to be able to run in sync with your existing grid tie system (AC coupling) or disconnect the existing system with the flip of a transfer switch and power from your DIY system?
The latter will allow for less costly inverters / AIOs since you don't need the fancy bells and whistles.
That leads to the next question, do you want a modular component based system (separate inverter, solar charge controllers) or an all in one approach (everything in one box?

Batteries - will you be able to protect them from freezing? If yes go with LiFePo4. You could enclose them and in an insulated cabinet and keep them above freezing with heat mats / pads, some off the shelf batteries are doing this. If you can't keep them above freezing you need to use lead acid batteries.

Solar panels - go for the largest you can manage and figure out the optimal width / length based on your trailer length and panel mounting orientation.
Look at some photos of DC solar trailers for ideas on mounting. I've seen some of your creations, you'll have no problem coming up with a great mount.
Combining arrays can be done multiple ways depending how each array is wired and what the specs for your mppt are.

That should be enough to get you thinking.
I have been dwelling on this since its inception and I think I should leave the fifth wheel out of the picture. That thing weighs 15,000 pounds and I don't think I need the added weight.

With that said I do want to set up a DIY solar that will produce approximately 5kw per year. Let's not bog down with the mount. I might go on a trailer or decide to put on the ground or maybe on top of the pallet rack garage or might use as a canopy for my dog area. Either way, I will figure out where they go.

I am more concerned with what I need to make this work. I already have an emergency panel with all its own circuits. I am sure it runs the refrigerator a few lights, the well pump.... I can put whatever circuits I want in there. I can certainly more a circuit from one box to the next.

The goal. From this moment, this could change... Is to have a battery that won't be frozen that can be backup for my emergency panel and run my necessary circuits in a prolonged outage. So first thing is this array will charge the battery and keep it charged. Next I will want to run steady draw high consumption items that will consume the 5kw excess that I need. So for example, for 6 months of the year I need a dehumidifier in my basement, that thing spins the meter. Probably 15kwh per day. That one appliance alone gets me halfway there. Hmm how about I charge my car off of it? Okay next is clothes drier, my guess is that thing runs pretty at least every other day and most of a day on the weekend. When the drier runs I see my consumption spike. Heck probably easier for me to just install one more panel with just the items I want. Basic knife disconnect. Manual. Then when there is no solar or all winter I simply shut off the solar and run off the grid.

It seems like if I have a decent size battery, and run high energy consumption items, that will consume lots of kwh in an isolated few circuits. The grid tied array will cover most of my needs. So if I can ease the load by taking 5,000kwh off the grid I know I the grid tied array would have an overproduction and I would never have to pay for electricity.

This is the brainstorming stage of this concept. Tossing the ideas out I just mentioned can help stimulate the creative juices.

Heck I think that is the right approach for anyone wanting to start with a backup solar system. Get the system to ease a big guaranteed load. Then that leave the little stuff to the grid.

Charge the car.
Run dehumidifier
Run Clothes drier

That is a good start.
I would imagine that I could run dehumidifier at high for daylight hours not run it at night. If the humidity is lower during the day and creeps up at night that is fine. Heck could run 2 at once during the day if that helps the system.
Clothes drier could be run during the day hours.
Car needs charging in evenings for consistency. I don't know much about the device that plugs into the Tesla except that if it runs on a larger amp breaker it consumes more energy per hour. So on a 60 amp breaker it sucks down about 10kwh per hour. A normal full charge from pretty low is about 6 hours or 60kwh. So the car might need to be charged more often, like couple of nights a week instead of once.

 
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Post by ColdHouse » Tue. Apr. 30, 2024 5:27 am

Hmm. Well been looking into this a little bit and I have to say that Big Barney is pretty optimistic about renewable energy running the world. Wow. Charging a car pretty much seems like it needs to be done while the sun is out. If you want to charge at 10kwh per hour for 6 hours you need a lot of panels and all the energy need to be going to the car. It appears that charging an EV from stored energy in a battery is also a big ask. You would need a huge battery bank and it would get depleted/emptied charging the car. So if a person has 5kw system and wants to charge their car they better be charging during full sun and even at that they won't get it charged in one day.

So my above scenario in the last post doesn't really work. I guess I need to rethink this and come up with a more realistic solution. Charging the EV is out. The dehumidifier is a good idea, maybe. I don't know.

What I see is most energy is consumed when the sun is not out or at least not producing solar electricity.
What I notice is my panels pretty much produce for about 6 hours per day from around 9:30am to 3:30pm. The other hours of sunlight add little in solar energy production.

In a situation like mine where my wife has driven the EV to work 5 days a week it cannot be home plugged into the sun absorbing solar panels. If a person is off grid and has an EV and battery bank, they would probably have to charge their EV everyday in order to put less strain on their home battery bank.

EV's draw a huge amount of electricity and expend that energy in a short amount of time.

With all that said, I guess the best idea to consume 5kw of energy is to look at the low energy consumption items that draw consistently rather than the energy hogs. So the dehudifier is probably still a reasonable suitable appliance especially if I run it when the sun is hitting the panels and not at night, presently we have 3 refrigerators plugged in and running. I am not sure what else runs during the day. As mentioned I think most energy is consumed in the morning before work and after work. The consumption must be televisions, stove, clothes drier, lights. None of that stuff is on during the day when solar panels are producing energy.


 
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Post by ColdHouse » Tue. Apr. 30, 2024 8:33 am

Ideally a 5kw system with a battery and the battery gets charged only off the 5kw system but the battery can get discharged to the entire home. Don't know how to make that work. So I don't change the grid tied aspect, add 5kw per year of production and can use it however I want. I think there is probably a way to have the battery act as the go between the off grid 5kw and the grid tied 16kw.

 
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Post by Hootyburra » Tue. Apr. 30, 2024 6:21 pm

If you want it to back feed the existing system your best option would be an AC coupling inverter.

I see you've already realized the reality of battery bank size and running high draw loads when the sun is shining.
That's why I have a 39kWh bank and plan to nearly double it before winter.

Another to keep in mind with your battery bank is the maximum discharge rate. For example a 5kWh 48V server rack battery shouldn't be discharged or charged with more than 2.5kW. A typical electric dryer pulls 6kWh when the heating elements are on.

Based on the research I've done an EV will use ~0.35kWh/mile; 10 mile drive ~3.5kWh.

Bases on the loads you are describing I'd recommend the same inverter I'm using but you'd have to use a transfer switch to isolate your current system from the rest of the house, it can't AC couple...

Let me think about options some more and come back.

 
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Post by ColdHouse » Wed. May. 01, 2024 5:43 am

I am thinking all I need are solar panels and something like this:

 
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Post by waytomany?s » Wed. May. 01, 2024 6:32 am

Seems pretty convoluted when all you need to do is call the original installer and add a small ground array.

 
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Post by ColdHouse » Wed. May. 01, 2024 6:57 am

waytomany?s wrote:
Wed. May. 01, 2024 6:32 am
Seems pretty convoluted when all you need to do is call the original installer and add a small ground array.
Why would you say that? Weren't you asking about DIY solar and saving money and DIY batteries? Maybe it was someone else.

If I already have a perfectly functioning Grid tied system why would I want to mess with that?

Furthermore, I know it is not as simple as just adding on. Once a system is installed I do not think it can just be added onto. You need a new separate system.

 
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Post by waytomany?s » Wed. May. 01, 2024 7:17 am

ColdHouse wrote:
Wed. May. 01, 2024 6:57 am
Why would you say that? Weren't you asking about DIY solar and saving money and DIY batteries? Maybe it was someone else.

If I already have a perfectly functioning Grid tied system why would I want to mess with that?

Furthermore, I know it is not as simple as just adding on. Once a system is installed I do not think it can just be added onto. You need a new separate system.
That's exactly what you are looking to do.

 
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Post by ColdHouse » Wed. May. 01, 2024 8:49 am

So if I get about 5-6kw panels.
Figure my home average is 1.5kwh per hour x 6 hours of sunshine = 9kwh consumed directly on average from solar panels.
Sunniest day produce 93kwh with (40) 400 watt panels = average 2.35 maximum production on sunniest day per panel.
If I install additional (14) 400 watt panels the most I would get is 32.55 kwh per day on sunniest day.
If I consume 9kwh from 32.55 the largest battery bank I would need is 23.55 but if you can only discharge the battery 80% I would need about a 30kwh battery maximum to not waste any energy generated from the new array.
Install in a grid tie inverter like this one: https://signaturesolar.com/growatt-120-240v-6kw-g ... -inverter/

Then I have panels that produce electricity and go directly to the battery which goes directly to the grid tie inverter that shuts down when the grid goes down. All my energy is used in the home while the grid is up.

What you think hooty?

It seems like with these grid tied inverters, I wouldn't even need a battery. I already have a bidirectional meter and power from the original system goes to the grid. So I would think that with the grid tied inverter on the new array that would shut down the new array if the grid went down but send all the power generated to the main panel for immediate use or get sent to the grid.
Last edited by ColdHouse on Wed. May. 01, 2024 9:08 am, edited 2 times in total.

 
ColdHouse
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Post by ColdHouse » Wed. May. 01, 2024 8:57 am

waytomany?s wrote:
Wed. May. 01, 2024 7:17 am
That's exactly what you are looking to do.
Yes and were you not the person asking Hooty to explain in detail how he assembled and built his batteries? It seemed in that thread that you were interested in how to DIY your own Solar and Battery.

Now you suggest calling the original installer.

That is okay. This will be an interesting thread. It will end up being a solar with battery and grid tied system.
The thing about this array is it will be used completely each day so that as much as possible from my other already installed system can go back to the grid for my off season months.

I would be interested in hearing about some of your adventurous, innovative projects that you have done or are presently doing. Please start a thread and share with us the details of your ingenuity.


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