Will this system work?

[JeffG2583]

Hi everyone, so I'm brand new to this forum, but have been hanging around reading various posts for a few months now. I've watched a ton of videos from Will and others regarding solar, and things like this really interest me. I love the idea of not having a power bill as well. I'm looking to do a solar system with a new house we are about to build, so we will be insulating it well. We will also be choosing energy efficient appliances including a geothermal heat pump with desuperheater and heat pump water heater.

I can't go grid-tied because the base power bill here is $40 and they are currently charging over $5 per kW of solar panels per month just for having solar. For me that would be a BASE power bill of $110 ($40 + (14 * 5) before using a single watt. By my math, I'd never be able to provide enough extra power back to the grid to make up that difference since they also don't offer any time of use rates...just one flat rate for the co-op I'd have to use. Their buyback rate is what they call an "avoided cost", which is $0.05/kWh.

I estimate my power usage would be around 50 kWh per day +/-
I'd like to use 2 x 6000XP inverters with 16kW of bifacial 390w panels ground mounted. We have 28 acres.
For battery, I was thinking 60kW (12) of either the EG4 or the Ruixu(?) batteries.
I will have a 10kW propane backup generator which will burn 1.5 gallons per hour.

I'm located in central Alabama. I'd just like to know if you think this system would work. I'd really like to go this route if possible, so I'm open to any suggestions on changes to the system.

One last question I have, is I currently have a nice 4 post enclosed server rack that I'd like to use for the batteries if possible. Can I purchase just the bus bars and covers to go in it, or do I have to purchase the specific cabinets that hold 6 batteries? I'd like to avoid that cost if possible.

Thanks.

 

[DIYrich]

Find out if an occupancy permit requires a grid connection.

50 kwh of daily usage and 12kw of inverter seems a little low. Seems like you have a big house. If so, you may need 3 or 4 to run a large ac.

Rule of thumb is 3x of daily usage in batteries (150 kWk?) and enough pv to recharge on one good day (30kw?). You can rely on propane instead. Pencil out the cost.

For a primary residence with no grid, I would consider a more proven system like Outback. Sure it will cost more, but you pay for it once. Although having 4 6000xp does provide some redundancy.

Consider building the system in stages (but plan for a large system). Just in case you are oversizing.

 

[JeffG2583]

So it looks like I had a decimal in the wrong place on my power usage estimate. My new estimated power usage is 36kWh per day. Also, I have a question about using an existing enclosed 4 post server rack to mount batteries in. If I were to use this, can I purchase the bus bars to install? If so can you give me an idea of what I would need? Thanks.

 

[DIYrich]

Need to figure usage during summer (peak solar) vs winter (less solar from panels). Take into account ac and heating needs. Size system for each time of year, and build the larger of the two.

For off grid, the rule of thumb is 3 days of usage for batteries (108 kWh of batteries for 36 kWh daily usage). Generator is for longer bad weather.

Size your panels to recharge batteries on one good day of solar (so you can last another 3 days of bad weather). That would be about 20-30 kWh of panels (less production per panel in winter) for 100kWh of batteries.

 

[chrisski]

One last question I have, is I currently have a nice 4 post enclosed server rack that I'd like to use for the batteries if possible. Can I purchase just the bus bars and covers to go in it, or do I have to purchase the specific cabinets that hold 6 batteries? I'd like to avoid that cost if possible.

If this build will get inspected, I doubt your server rack will work. Each battery is limited to 20 kWh and batteries must be separated by 3' unless installed in a UL approved case and the total kWh in this case is still 20 kWh or less.

As far as bus bars, the odds of you finding a bus bar for your situation are pretty low, but busbars can be built with copper flat bar. My copper busbars are homemade out of 1/4" x 3/4" and drilled with a hand drill. Will come out much better with a drill press. The measurements were too precise for me to send off.

I'm looking to do a solar system with a new house we are about to build,

Whoever you're building the house with, just make sure they are wiling to conserve. Although I have no problems with "ultra" energy conservation, my family has no desire for it.

Most people I know want to conserve as long as they don't have to spend extra money on appliances or use less power with th3e ones they have. They will unhook a phone charger when they're done and feel good about themselves. Especially on the fifth rainy day in a row where the noisy 15 kWh generator is on.

Honestly, with Net Metering going away and the electric consumers getting charged by power companies for solar installations, the break even point is far away to never.