Controller for Everything!

[rdanneskjold]

Hello,
I am in the beginning stages of implementing a backup power system for my house. I live in SoCal, so power here is expensive. but that is not my motivation. I am looking for power security, and do not want to be reliant on the grid. Fire season is coming, and because of last year's fires, the power companies just shut down distribution when it gets too windy.

and I think things are going to get worse before they get better... anyway, I could use some help. here is my plan:

Stage 1: Natural gas backup generator (actually tri-fuel). I already have it, though it sits unboxed in my garage.
2: Battery storage. The idea here is to run the house off a battery-based inverter from a battery bank, probably AGM deep-cycle. My inspiration for this came from our Prius. the idea is not 'capacity', but to make generator output more efficient. Natural gas is cheap but not free. so like the car, when the system needs it, the generator will turn on and charge the bank. as opposed to running constantly even for small loads.
3. Solar. I have a nice flat roof with abundant sun exposure. We rent, but the landlord has given his blessing for a non-permanent installation. so if we ever leave we can just take it with us (albeit with moderate effort). The plan is to use a weighted bracket system instead of drilling into the roof. Using the same battery bank, a small array of say 2kW will provide charge current as well as provide for baseline usage.

Once stage 3 is in place I may opt out of the grid entirely. I've already confirmed with the utility that I can disconnect from electrical and keep natural gas service.

For inverters, the plan is to get a 220V inverter and connect to a midpoint grounded auto-transformer. This will give me split phase power. I already have a 5kVA buck-boost transformer on hand. I am unsure whether to get a single large-capacity inverter or multiple smaller ones operating in parallel.

So, there are a few things I need help with, mostly having to do with a controller. I need one that can charge batteries from solar, auto-transfer during a grid outage, turn on the natural gas generator, etc.

Thanks in advance for your thoughts, ideas and suggestions!

RD

 

[Theo74]

Maybe have a look at this option from Victron, it does all you want.
More brands make such all in one solutions, but I thought to start with a reliable brand.

 

[snoobler]

3. Solar. I have a nice flat roof with abundant sun exposure. We rent, but the landlord has given his blessing for a non-permanent installation. so if we ever leave we can just take it with us (albeit with moderate effort). The plan is to use a weighted bracket system instead of drilling into the roof. Using the same battery bank, a small array of say 2kW will provide charge current as well as provide for baseline usage.

Welcome to the forum.

My thoughts:

Have you sized this system based on your consumption?

Step 1 is a great idea for power security.

Step 2 is just added expense. You're not making the generator meaningfully more efficient. You've just added an expensive storage and power system in between your generator and your loads. Your generator will ultimately support 100% of the energy required by the loads, and with daily cycling, you'll wear out AGM batteries in just a few years as they typically have shorter cycle life than high quality FLA or GEL. Given the charging and inverting inefficiencies, you'll likely use more fuel than you would without the batteries/inverter in place.

Step 3 IMHO, this seems to be almost insanity on a rented property. 2kW of an array is pretty tiny and would only provide about 10kWh of energy daily assuming great sunshine and no shading/clouds from sunrise to sunset. This is about 1/3 the energy usage of the average American household.

"weighted bracket system" on a flat roof... Flat roofs work because they aren't subjected to heavy loads like snow loads.

Have you run the calculations on the weight required to keep an array in place for a given wind speed? A 20mph wind impinging directly on a typical large panel produces over 200# of force.

If so, have you actually run the calculations if the roof can handle this?

A "weighted" bracket system on the ground would seem much more preferable if you have the option.

 

[rdanneskjold]

In full disclosure, it is my style to begin with over-complex designs, and work backward toward simplicity.

 

[snoobler]

In full disclosure, it is my style to begin with over-complex designs, and work backward toward simplicity.

I feel your pain!

 

[Bleedingblue]

Hello,
I am in the beginning stages of implementing a backup power system for my house. I live in SoCal, so power here is expensive. but that is not my motivation. I am looking for power security, and do not want to be reliant on the grid. Fire season is coming, and because of last year's fires, the power companies just shut down distribution when it gets too windy.

and I think things are going to get worse before they get better... anyway, I could use some help. here is my plan:

Stage 1: Natural gas backup generator (actually tri-fuel). I already have it, though it sits unboxed in my garage.
2: Battery storage. The idea here is to run the house off a battery-based inverter from a battery bank, probably AGM deep-cycle. My inspiration for this came from our Prius. the idea is not 'capacity', but to make generator output more efficient. Natural gas is cheap but not free. so like the car, when the system needs it, the generator will turn on and charge the bank. as opposed to running constantly even for small loads.
3. Solar. I have a nice flat roof with abundant sun exposure. We rent, but the landlord has given his blessing for a non-permanent installation. so if we ever leave we can just take it with us (albeit with moderate effort). The plan is to use a weighted bracket system instead of drilling into the roof. Using the same battery bank, a small array of say 2kW will provide charge current as well as provide for baseline usage.

Once stage 3 is in place I may opt out of the grid entirely. I've already confirmed with the utility that I can disconnect from electrical and keep natural gas service.

For inverters, the plan is to get a 220V inverter and connect to a midpoint grounded auto-transformer. This will give me split phase power. I already have a 5kVA buck-boost transformer on hand. I am unsure whether to get a single large-capacity inverter or multiple smaller ones operating in parallel.

So, there are a few things I need help with, mostly having to do with a controller. I need one that can charge batteries from solar, auto-transfer during a grid outage, turn on the natural gas generator, etc.

Thanks in advance for your thoughts, ideas and suggestions!

RD

If you have an autotransformer then buy a 230/240 volt hybrid inverter. Get one that has up to 450 volt input from the solar array so you don't have to run large wires for current loss. They are also much less expensive than a split phase and can be run in parallel with additional units.