18 month DIY project finally done: 39kW inverter power off grid system

[timselectric]

There were likely other design factors that made this scheme more desirable than upflow.

The only design factor was minimal cost to adapt existing equipment for air intake filtration.
They reversed the fans and slapped the filter housing on what used to be the exhaust. Because it was easier.

 

[fmeili1]

Did you do firmware updates? Maybe they are unstable under really light load, and now that your baseline 500W load is on, they are stable?

Yes, I've installed the newest versions. I know about this low load situation which made the LED pulsing worse. But my base load is now only a little bit higher but the problems are completely gone.

Btw. I've noticed an additional problem with low load situation which made me some headaches, but I was able to solve it. At the moment when the AC-in's gets connected to the grid while the AIO's have low load, some of the AIO's are getting in fault F60 (Power feedback protection). This problem will not occur when the load is higher (about >150W per AIO). So I've changed the smart home rules to close the AC-in contactors only if the load is high enough and if it's too low, I let ramp up one mini split and I delay the contactor closing until the load is high enough. After the contactors are closed, I reset the mini split to it's default value. Not nice, but it works.

 

[fmeili1]

The only design factor was minimal cost to adapt existing equipment for air intake filtration.
They reversed the fans and slapped the filter housing on what used to be the exhaust. Because it was easier.

My feeling goes in the same direction... the flow direction was chosen because of costs and not depending on optimal engineering...

 

[timselectric]

My feeling goes in the same direction... the flow direction was chosen because of costs and not depending on optimal engineering...

Shouldn't be an issue for you.
Active cooling and minimal loading most of the time.

 

[fmeili1]

I've taken very good care about equal length wire sizes. Not only for the battery wires but also for the AC-out and AC-in wires to make it easier for the AIO to do load sharing. The following charts showing that the load is really very nice distributed over all six AIO's and the same is valid for the battery current. All six separate diagrams are overlayed so it's hard to separate them visually.
Only the battery current have slightly differences, but this chart was produced while 2 of the AIO's not already had PV connected. Next week I'll see if the current will be shared even better between the six AIO's.

 

[new off grid]

Finally after 18 month I've completed the installation of my DIY off-grid system. It was an incredible amount of work, much much more than previously expected.

Tomorrow will be the final inspection of the cities building division and on Friday the inspection of the power company - I'm very nervous...

Here are the key points:

• Single family home with 200A service and about 2100sqft living space, attached 2 car garage and RV garage
• Central heat pump for cooling and heating, everything electrical, no natural/propane gas, no wood fireplace
• Off-grid system with 39kW inverter power, grid only as backup if really required (disconnected most of time via remote controlled contactors).
• Permission to treat it as a "generator solution" with a manual transfer switch and I have the permit to have a permanent AC-in connection to the grid, independent of the transfer switch position!
• 18.5kWp solar bifacial modules 460Wp, 40 PV modules organized in 8 strings, strings with 4, 5 and 6 modules in series (no parallel modules), most modules on concrete tiled sloped roof (8 on RV garage flat roof), PV module orientation is 17x south, 11x north, 6x east, 6x west (not ideal roof for solar).
• LFP batteries (40kWh are allowed, organized in two separate racks)
• Emergency shutdown features for many possible failure scenarios
• Fully integrated in existing smart home to implement "smart" energy management and remote monitoring/controlling

View attachment 211059

For final testing, I've used the system for the last 5 days and everything is working so far as hoped. The batteries have about 63% SOC remaining in the morning before new solar production begins (this will change in summer for sure). Between 11am and 12pm the batteries are fully re-charged.

Because of the implemented ducted mini spit the AIO's running very nice cool and because of the modded fans, they are really quiet now.

The next charts showing an example of a 24h cycle while testing (full PV production between 6:30am and about 12pm until the batteries are fully re-charged):
View attachment 211060

View attachment 211061

View attachment 211063

Load and consumption situation of the house:

• 21,000kWh per year consumption
• 114kWh highest peak consumption per day (usually end of July or beginning of August)
• Highest consumption between May and August (2,000kWh to 3,000kWh per month)
• High power consumption devices sorted by power
• Central heatpump: 5,800W (max. 7kW, <=15kW inrush)
  ▪ Dryer: 5,200W
  ▪ Water heater: 4,470W
  ▪ Wall oven: 3,500W
  ▪ Coocktop large field: 3,300W
  ▪ RV garage mini split: 2,500W
  ▪ RV parked in the driveway: 2,000W
  ▪ Microwave: 1,700W
  ▪ Coocktop 3 small fields: 3x1,400W
  ▪ Washer (front loader with heating element): 1,200W
  ▪ Pool pump: 1,200W
• High energy consumption devices sorted by runtime:
  ▪ Pool pump: 8 hours only on daytime
  ▪ Central heatpump: in high summer days it runs about 60%-90% of the time constantly (60% at night), in winter time it runs about 20%-30% of the time
• Power requirements so far:
  ▪ house idle consumption is about 500W
  ▪ AIO idle/self consumption is about 550W for all six units
  ▪ while pool pump is running 8-9h over the whole day the base house load is about 2000W total
  ▪ never seen more than 24kW power consumption at a time – but it may happen
  ▪ possible worst case could be: 2000W idle with pool pump + 5000W heatpump + 4500W water heater + 3500W oven + 6500W for 3 coocktop fields + 200W dryer + 2500W RV garage mini split + 2000W RV in driveway connected to the house + 1200W washer = 32.5kW is still below rating of 39kW with reserve for e.g. toaster, water cattele, microwave, tools, etc.

Unexpected challenges / missed considerations while building:

• AIO's were extremely loud (our master bedroom is located behind the inverter wall), so I had to modify the fan control of all 18 fans in all 6 AIO's to enable a temperature controlled fan speed. Because they heat up quickly under charging conditions, I had to implement an active equipment cooling on top of this to make them really quiet. To achieve this, I've installed a 9,000 BTU ducted mini split which cooling power is controlled via smart home rules, depending on the AIO temperatures. Now they are usually around 50-52°C, even under high load (charging and inverting).
• I've implemented an emergency shutdown circuit (I wanted to have that to be able to sleep with a better feeling) which shutdown the system in case of smoke detection or too high AIO temperatures or too high battery temperatures or camera detects fire or manually remote if I want. In case of an emergency is detected, the PV modules are shutdown via TIGO module level PVRSS, the batteries are disconnected from the AIO's via 600A relays, the AC-in's are disconnected from the grid via contactor if connected (usually the are always disconnected anyway). Because these three different types of disconnect's are NO (normally open) operated, I've needed to build a blackstart UPS to initially startup the system.

I am totally amazed and very pleased that my LED pulsing/flickering problems are completely gone - without doing anything! While in building phase, I've noticed the LED pulsing problem a couple of times and I thought many hours about how to solve it. I have no idea why this problem completely disappeared, independent if solar production or not, clouds or not, battery charging or discharging, high or low load,...

I'll update this thread from time to time with new pictures, findings, data, issues, etc.

big and nice system
how much total friend ?

 

[wpns]

The 18k was not available 18 month ago. I hope I will not regret to choose the EG4-6500EX because it's sunset now. But they are working great so far and it was (at this time) an unbeatable price for a 6,500W inverter, 6,500W AC charger and 8,000W PV with 500Voc and two MPPT's. I would have loved to use Victron components (I'm using them in my RV) but it would have been much more expensive.

All AIO's are running at the latest firmware (DSP=79.71 and MCU=61.13) since it's available. The flickering in the early test phase also occurred with the newest firmware versions. Maybe as @wpns mentioned, it's because the base load is now a bit higher (the 9,000BTU minis split is now always running). Btw. Because the city required to install a 2-pole transfer switch (they didn't allow a previous planned 3-pole TS), I'm running with common neutral setup (program 42 set to ENA to disable the internal N-G-bonding relays) and the bonding screws are inserted in all six AIO's.

The AIO's are sucking cold air on the top side entries and blow the hot air out on the bottom and bottom side outlets - which is silly engineered because it would create a thermal shortcut. The hot air is rising and get sucked in at the top to cool the device - with this nonsense the AIO's are heating up very fast - whatever they smoked while they engineered the cooling system, they should smoke less of it That's the reason why I've 3D printed these 45° windshields which are installed between each AIO and on the outer ones so the hot air will at least be separated a bit from the cold air.

Here are some more pictures in detail:

These small grey rectangle boxes (over the pos. busbar and below the wireway) are the two 600A/80VDC relays to disconnect each server rack from the positive busbar in case of an emergency.
View attachment 211115
View attachment 211127

Here are the AC-out and AC-in combiner panels with surge protectors below both of them. The left metal box contains the 8 double pole PV breakers. The right plastic box contains the two 3-pole contactors to connect the grid with the AC-in's of the AIO's - but only if really required. I found out that if the AIO's are permanently connected to the grid, each unit will draw about 50W from the grid, even if grid is not used! In my case this would have been 300W permanently drawn from the grid, just to be prepared to use it - I don't want this! Maybe I need 5-10 days per year some hours gird support and I don't want to waste more than 2,600kWh per year. Instead I've implemented a smart home rule which only closes the AC-in contactors if required and before I initiate the AIO's program 12 "point back to utility" by adjusting this setting. After I will have enough solar again, I will initiate program 13 "point back to battery" by adjusting the voltage value via a smart home rule. While system is on grid, I've reduced the battery charging to the lowest possible value (2A per unit) because I don't want to charge the batteries from the grid.
View attachment 211119

This picture shows the controller which implements the blackstart, the emergency control and the monitoring via SolarAssistant (via MQTT bridge to the existing smart home). Above the controller are the three components for the online-double-conversion-UPS (small inverter, small battery, small battery charger). This UPS has enough power to drive the controller with it's relays/contactors etc.\
View attachment 211124
View attachment 211125
View attachment 211126

The following picture shows the outside wall with the Tigo RSS transmitter with the two emergency shutdown buttons (the left will disconnect the PV modules, the batteries and the AC-in) and the right button just the PV modules via Tigo but the inverters will still running from batteries). Left of the main service panel is the transfer switch. The completely oversized box above the main service panel is just a box to splice the grid to the AC-in breaker panel and the transfer switch (this box and the transfer switch were the only parts which I've not installed by myself, it was done by an electrician).
View attachment 211131
View attachment 211133
View attachment 211134

This is spectacular! Good luck with your inspection (today?)

 

[wpns]

I've promised my wife that she will not have comfort loss and she does not need to depend on sunshine to do what she wants to do (cooking, laundry, etc.). Also I didn't want to tell her things like "please turn off the oven because I need to use my miter saw.., etc.". For me it was clear that I need to massive oversize the system to have enough reserve to make it unaware, that the house is running on off-grid inverters only from solar and batteries. But because of the price of AIO's and batteries (and in our >300 sunny days location) it's possible without breaking the budget.

This! Not just the wife, but myself and family and houseguests. I don't want to be my mother (the sound of the ice dispenser on the fridge always triggered "Don't Use Up All The Ice!"), or have to put up those kitchy signs "When you are having fun in the sun, please don't flush for number one", or ask/tell people how and when to use the HVAC splits, or "Don't use the clothes dryer on cloudy days" (I mean, how backwards is that? Use the clothesline when it's raining?). I don't want the 'camping out' experience, I want the first-world "Plenty of water and power and ice and food and clean air and all the comforts of home because this is my home" experience. Sure, I'll obsess about the cistern and the battery and such because it's my hobby, but for the most part I'll just live my life.

 

[wpns]

Really love all the 3D-printed stuff!

 

[fmeili1]

big and nice system
how much total friend ?

After the 30% federal incentives and the $1000 Arizona solar incentives, my net invest was about $34,000.

With different AIO's, which may not require equipment cooling, I could have saved the ducted mini split, the ductwork and an other mini split with a typical indoor unit to cool down the ambient in the garage. Also the controller with the emergency circuit and the blackstart UPS was not a must.

I think, it's realistic that one can build a DIY system with this performance data for about <=$30,000 (after incentives). Maybe cheaper, because I bought the components 18 month ago and now all mayor components are cheaper.

 

[fmeili1]

This! Not just the wife, but myself and family and houseguests. I don't want to be my mother (the sound of the ice dispenser on the fridge always triggered "Don't Use Up All The Ice!"), or have to put up those kitchy signs "When you are having fun in the sun, please don't flush for number one", or ask/tell people how and when to use the HVAC splits, or "Don't use the clothes dryer on cloudy days" (I mean, how backwards is that? Use the clothesline when it's raining?). I don't want the 'camping out' experience, I want the first-world "Plenty of water and power and ice and food and clean air and all the comforts of home because this is my home" experience. Sure, I'll obsess about the cistern and the battery and such because it's my hobby, but for the most part I'll just live my life.

Usually, it would not be too much effort to change the behavior a little bit to save energy (like most off-grid people are doing - it's a bit of the feeling to do a small part to save the planet) - but because the sun is for free and the batteries are there and the system have enough power, it doesn't hurt to waste a part of this energy by not organizing the life in sync with the off-grid system - and like you, I love the convenience to not need to do this! This was one of my mayor goals.

 

[fmeili1]

Really love all the 3D-printed stuff!

I had the printer about 2 years now and have not used it a lot before starting the solar project. As longer the solar project took as more I've realized how powerful such a printer is to create custom parts in short time to visually enhance the optic of this project. Everything looks much cleaner after I've printed the battery wire covers, holders, brackets, cases, etc.
In the meantime I've got a big fan of 3D printing and with an extreme easy to use free engineering software (OpenSCAD) it's just fun to produce 3D objects just by adding/subtracting/rotating geometric primitives with commands and not wasting time to learn how to use a complex 3D CAD software from time to time.

 

[fmeili1]

I'd like to share my 3-wire diagram of the system (overall and zoomed for better reading):








In case someone wants to know about the controller circuit, here is the schema:

 

[jbkrntrprz]

Finally after 18 month I've completed the installation of my DIY off-grid system. It was an incredible amount of work, much much more than previously expected.

Tomorrow will be the final inspection of the cities building division and on Friday the inspection of the power company - I'm very nervous...

Here are the key points:

• Single family home with 200A service and about 2100sqft living space, attached 2 car garage and RV garage
• Central heat pump for cooling and heating, everything electrical, no natural/propane gas, no wood fireplace
• Off-grid system with 39kW inverter power, grid only as backup if really required (disconnected most of time via remote controlled contactors).
• Permission to treat it as a "generator solution" with a manual transfer switch and I have the permit to have a permanent AC-in connection to the grid, independent of the transfer switch position!
• 18.5kWp solar bifacial modules 460Wp, 40 PV modules organized in 8 strings, strings with 4, 5 and 6 modules in series (no parallel modules), most modules on concrete tiled sloped roof (8 on RV garage flat roof), PV module orientation is 17x south, 11x north, 6x east, 6x west (not ideal roof for solar).
• LFP batteries (40kWh are allowed, organized in two separate racks)
• Emergency shutdown features for many possible failure scenarios
• Fully integrated in existing smart home to implement "smart" energy management and remote monitoring/controlling

View attachment 211059

For final testing, I've used the system for the last 5 days and everything is working so far as hoped. The batteries have about 63% SOC remaining in the morning before new solar production begins (this will change in summer for sure). Between 11am and 12pm the batteries are fully re-charged.

Because of the implemented ducted mini spit the AIO's running very nice cool and because of the modded fans, they are really quiet now.

The next charts showing an example of a 24h cycle while testing (full PV production between 6:30am and about 12pm until the batteries are fully re-charged):
View attachment 211060

View attachment 211061

View attachment 211063

Load and consumption situation of the house:

• 21,000kWh per year consumption
• 114kWh highest peak consumption per day (usually end of July or beginning of August)
• Highest consumption between May and August (2,000kWh to 3,000kWh per month)
• High power consumption devices sorted by power
• Central heatpump: 5,800W (max. 7kW, <=15kW inrush)
  ▪ Dryer: 5,200W
  ▪ Water heater: 4,470W
  ▪ Wall oven: 3,500W
  ▪ Coocktop large field: 3,300W
  ▪ RV garage mini split: 2,500W
  ▪ RV parked in the driveway: 2,000W
  ▪ Microwave: 1,700W
  ▪ Coocktop 3 small fields: 3x1,400W
  ▪ Washer (front loader with heating element): 1,200W
  ▪ Pool pump: 1,200W
• High energy consumption devices sorted by runtime:
  ▪ Pool pump: 8 hours only on daytime
  ▪ Central heatpump: in high summer days it runs about 60%-90% of the time constantly (60% at night), in winter time it runs about 20%-30% of the time
• Power requirements so far:
  ▪ house idle consumption is about 500W
  ▪ AIO idle/self consumption is about 550W for all six units
  ▪ while pool pump is running 8-9h over the whole day the base house load is about 2000W total
  ▪ never seen more than 24kW power consumption at a time – but it may happen
  ▪ possible worst case could be: 2000W idle with pool pump + 5000W heatpump + 4500W water heater + 3500W oven + 6500W for 3 coocktop fields + 200W dryer + 2500W RV garage mini split + 2000W RV in driveway connected to the house + 1200W washer = 32.5kW is still below rating of 39kW with reserve for e.g. toaster, water cattele, microwave, tools, etc.

Unexpected challenges / missed considerations while building:

• AIO's were extremely loud (our master bedroom is located behind the inverter wall), so I had to modify the fan control of all 18 fans in all 6 AIO's to enable a temperature controlled fan speed. Because they heat up quickly under charging conditions, I had to implement an active equipment cooling on top of this to make them really quiet. To achieve this, I've installed a 9,000 BTU ducted mini split which cooling power is controlled via smart home rules, depending on the AIO temperatures. Now they are usually around 50-52°C, even under high load (charging and inverting).
• I've implemented an emergency shutdown circuit (I wanted to have that to be able to sleep with a better feeling) which shutdown the system in case of smoke detection or too high AIO temperatures or too high battery temperatures or camera detects fire or manually remote if I want. In case of an emergency is detected, the PV modules are shutdown via TIGO module level PVRSS, the batteries are disconnected from the AIO's via 600A relays, the AC-in's are disconnected from the grid via contactor if connected (usually the are always disconnected anyway). Because these three different types of disconnect's are NO (normally open) operated, I've needed to build a blackstart UPS to initially startup the system.

I am totally amazed and very pleased that my LED pulsing/flickering problems are completely gone - without doing anything! While in building phase, I've noticed the LED pulsing problem a couple of times and I thought many hours about how to solve it. I have no idea why this problem completely disappeared, independent if solar production or not, clouds or not, battery charging or discharging, high or low load,...

I'll update this thread from time to time with new pictures, findings, data, issues, etc.

So how long have you worked for Nasa? SpaceX could use you!!

 

[WindWizard]

If those ducts above your eg4's are what I think they are then they are highly flammable. They look like metal but they are really just plastic. You can tell how flammable they are by just taking a lighter to a piece of one and see if it catches on fire easily.

 

[G00SE]

If those ducts above your eg4's are what I think they are then they are highly flammable. They look like metal but they are really just plastic. You can tell how flammable they are by just taking a lighter to a piece of one and see if it catches on fire easily.

If something catches the flex duct on fire, I’d think he’d have far more significant issues to be concerned about by then

 

[fmeili1]

So how long have you worked for Nasa? SpaceX could use you!!

It's no rocket science, just a bit of electrical engineering, don't overrate it. A little basic knowledge, enough care and enough patience are often enough.

 

[fmeili1]

If those ducts above your eg4's are what I think they are then they are highly flammable. They look like metal but they are really just plastic. You can tell how flammable they are by just taking a lighter to a piece of one and see if it catches on fire easily.

They are made out of thin aluminum.

 

[Daddy Tanuki]

They are made out of thin aluminum.

no fire concerns there!

 

[KellyDood]

You have created A Thing Of Beauty