We just bought a lot, and have started the planning phase for an all-electric passive house. All the design, sizing, build work will be handled by professionals, but I suspect that they won't have much experience doing what we want because there isn't much demand for a grid-tied-off-grid-capable housing around here. My goal is to better understand the options, devices, trade-offs, etc. around selecting from the massive pool of approaches to solving that problem.
The house is going to be on a 33x150 lot the Chicago suburbs and it will be grid-tied. We get power outages surprisingly often (out for 30-45m last night). I would like the system to seamlessly handle the off/on grid transition without any downtime. We have a NG generator at our current house and it takes ~30s to transition, so all the sensitive electronic devices have to have UPS, I have to reset a bunch of clocks and other state storing devices every time it happens. I would like to make that go away along with having the ability to be mostly self-sufficient.
We have two EV and the house will be all electric, I'm guessing we'll need at least 400A service. We haven't had that discussion with the architect yet to get their thoughts, so mostly a way to frame the discussion right now.
The roof of the house and detached garage will be flat and angled south to maximize PV potential. I suspect that the architect will want to use AC coupled panels because that's what people do around here. We have AC coupled now because it totally made sense for our house, but I'm not sure what the right answer is here given our goals and design freedom with the new house.
I suspect that the architect will want to use either Tesla or Enphase AIO battery stacks because it's what they will be familiar with and they are very consumer friendly. It's the "safe" choice. I'm not in love with this idea for a few reasons; cost, Tesla battery chemistry, load restrictions, and scaling complexity being the top few. It would be great to better understand the trade-offs around this approach vs. my current thinking.
My current thought is to use something like an EG4 18k (or Sol-Ark 15k) to handle the battery/PV/grid integration; sizing at one hybrid-inverter per 200A panel. Probably starting with ~30kW of PV and 30kWh of battery, and add more battery/PV as we figure out consumption. This isn't as "safe" because I'm probably going to have to push for it, and do a lot of education around the trade-offs with the architect to get them on-board.
Inital Questions:
The house is going to be on a 33x150 lot the Chicago suburbs and it will be grid-tied. We get power outages surprisingly often (out for 30-45m last night). I would like the system to seamlessly handle the off/on grid transition without any downtime. We have a NG generator at our current house and it takes ~30s to transition, so all the sensitive electronic devices have to have UPS, I have to reset a bunch of clocks and other state storing devices every time it happens. I would like to make that go away along with having the ability to be mostly self-sufficient.
We have two EV and the house will be all electric, I'm guessing we'll need at least 400A service. We haven't had that discussion with the architect yet to get their thoughts, so mostly a way to frame the discussion right now.
The roof of the house and detached garage will be flat and angled south to maximize PV potential. I suspect that the architect will want to use AC coupled panels because that's what people do around here. We have AC coupled now because it totally made sense for our house, but I'm not sure what the right answer is here given our goals and design freedom with the new house.
I suspect that the architect will want to use either Tesla or Enphase AIO battery stacks because it's what they will be familiar with and they are very consumer friendly. It's the "safe" choice. I'm not in love with this idea for a few reasons; cost, Tesla battery chemistry, load restrictions, and scaling complexity being the top few. It would be great to better understand the trade-offs around this approach vs. my current thinking.
My current thought is to use something like an EG4 18k (or Sol-Ark 15k) to handle the battery/PV/grid integration; sizing at one hybrid-inverter per 200A panel. Probably starting with ~30kW of PV and 30kWh of battery, and add more battery/PV as we figure out consumption. This isn't as "safe" because I'm probably going to have to push for it, and do a lot of education around the trade-offs with the architect to get them on-board.
Inital Questions:
- If loads exceed the inverter capacity in a grid-tied hybrid system will they seamlessly pull additional power from the grid? Best scenario is charging both EV at the same time (~22kW) as normal household loads like the heat pumps, stove, cook tops, etc.
- DC vs AC PV? I have a decent handle on the high level trade-offs around this choice. In our current setup it totally made sense to opt for micro-inverters, but I don't know much about the real world trade-offs of a DC system. I'm leaning toward DC because the conversion losses associated with round-tripping might be larger than potential shading concerns. The panels will be on a "unshaded" roof facing south, but it is semi-urban residential area so there is some potential that the trees on the other side of the alley from our garage may shade the panels on the garage a little.
- Is the hybrid inverter sizing scheme sensible or should we be sizing larger?
- Is a hybrid inverter setup the best way to do this? If not, what are the better options?
- What other things should we be aware of? Very much at the I don't know what I don't know phase :D.