All threeIf you were building an off-grid ~2000sq. one story/level home in northern Arkansas climate, what type of HVAC system would you use with solar?
In floor radiant heating? Geothermal? Mini splits? Etc.
If you have geothermal as a source. What is the need for mini splits?New house would have radiant floor, first.
With geothermal as a source. And mini splits for the less used areas. And yes, a sand battery for sure.
It's the only affordable way I can find to heat in winter with summer production.
Mostly a backup.If you have geothermal as a source. What is the need for mini splits?
Hybrid system. The geothermal is the central unit with mini heat exchangers in the individual rooms.If you have geothermal as a source. What is the need for mini splits?
I also vote ground source heat pump with radiant flooring for heating. Backed up by mini splits and wood heat.
For A/C, mini splits with backup window units sitting safely in storage. I would also consider a room or two thats buried deep and maybe even some earth tubes with natural air flow. Not sure how to keep them from getting musty. That way you can still have some where cool to sleep during the apocalypse
Your probably right with some of the newer flooded condenser switching they are doing. The ground source is such a hugh up front cost.Without a doubt, in that climate, I'd go with an air source mini split heat pump. AC + heat, very efficient with generally ~ 3:1 coefficient of performance, and in your area, will likely never be cold enough for them to perform poorly.
We have two Daikins (not bad) and one Mitsubishi (fantastic) in three separate buildings, and I live in Maine. Even at sub-zero, they kept us nice and toasty. We'll put a Mitsubishi in the next house we build, as well. There are lots of different, somewhat exotic ideas people have about how to heat and cool a house. But for a reliable, relatively carefree approach to using solar, it's just about impossible to beat a modern heat pump mini split from one of the top tier brands.
Hey Oz, Im probably not to far from you. Yea, not allot of deep soil in the Ozarks for putting in ground loops.I'm in southern Missouri. At my house we have passive solar high mass, radiant infloor, geothermal, a wood boiler and miniplits but I wouldn't steer you that way precisely.
In order: Passive solar high mass design, mini-splits, propane and biomass (firewood).
Forget geothermal unless you've got money to waste. Very few contractors around here do it (well) and in 10 years there won't be any so good luck getting it worked on.
All of my off grid customers from the last 10 years or so have mini-splits, radiant in floor, propane and at least one 120g electric water heater (some have up to 5) with a 5,500 watt element.
Crazy, right? Well not if you think about it. Once you've got enough PV and inverter to run a few minisplits in the summer you've got a ton of spare capacity in the shoulder months and more than a few days in the dead of winter. Dump all that capacity into heating water for use in a radiant infloor heating later on. When there's not enough free hot water the propane boiler fills in the gaps.
I understand advantages of wood. But I’m looking for the convenience of not having to deal with it as I am getting older. I’ll probably over build with PV and batteries. The area I’m looking at rarely gets below freezing.If you have wood, and need the heating requirements in winter: wood gasification burner coupled to radiant with a large buffer tank. It probably doesn't get as cold there as it does where I am, so you can use a lot less wood or last longer on a full buffer. If you then have excess solar, you can use the heat pump (geothermal or air based) coupled to the same buffer tank. The good thing with having a wood option: I case of an emergency (imagine: all power down) I could run my entire heating system off of a couple of lead acid car batteries for days.
Of course, a regular high efficiency wood stove (or even better, a masonry fireplace) would be good to have too in addition. No power required, and the built in oven in mine allows for cooking food in case things go very very wrong...
Curious, did they run it through your hot water tank too? They did mine and claim it really helps. Just bought a massive 188gal tub and it fills up 3/4 before running out then heats up pretty fast.I completed a 2500 sq ft house in west Arkansas near Ft Smith about a year ago. I installed a Water Furnace 4 ton Geo Thermal HVAC system with 2 zones. It works great with a Sol-Ark 15K, 6.5 KW solar array, and 15KWH batteries. I think Arkansas does not get cold enough to be worth the expense of radiant flooring. The HVAC has variable speed compressor and fans; it starts with low current draw and ramps up slowly to heat and cool the house. so it works great with an inverter. It is a heat pump; it really works by moving heat back and forth between the 4 wells in the ground which are around 60 degrees all year round and the house. Since the house is generally set around 70 degrees you only have about a 10 degree difference between ground and house. A rather small amount of energy is required to move this small amount of heat. I generally see around 10 amps being required to run the HVAC. These numbers move around depending on the conditions, but the system has proven itself cheap to operate with little added complexity. It is also very quiet.
The tax credits pretty much made up the difference in cost between ground and high efficiency air sourced systems. Drilling the wells for the water loops was really biggest cost difference between ground and air sourced systems, but as I said the tax credits pretty much took care of that. The drilling of 4 200 ft wells took a couple of days, but drilling company brought in a rigg that did the job in about 2 days. Another thing to consider is that there are no components sitting outside in the weather so less over all wear and tear.