Off-Grid Solar Setups

[Got2BTru]

Seems like you should get yourself a good tractor and backhoe and dig the ditch yourself, put the conduit and pull boxes in to their specs and just have them pull the wire. I did this on my house, but it was only 220' from the pole. You'll save enough to pay for the tractor. I also bought an off-road forklift for the project and it too has paid for itself over and over. Then it will move on to another project somewhere, but my tractor stays!

By all means add hydronic radiant in your slab!!! But drive it with thermal solar. Very low cost of operation, also does domestic hot water and there is no heating system more comfortable. Last winter we used three 70 watt circulators, running during the day, to heat our 2,800 sq ft house through the winter. No energy source other than solar. But I also have a wood stove in case we want an evening fire or to take the chill off a surprise cool morning. Now, in the spring, summer and fall months, we have 650 gallons of domestic hot water on tap for occasional bathroom floor heat and unlimited showers. I can't imagine a cheaper or more comfortable heating system! Then, if you need to, you could add a simple air conditioning system that is entirely separate from your heating system. I added a simple duct system and wired the house for air conditioning, but I doubt I'll ever install it.

My priorities in the house design included a steel frame, but most of the structure is 2/6 and 2/8 walls with blown in insulation and blown in attic insulation. Not the absolute lowest heat loss, but totally practical and a structure that is incredibly strong.

I don't like propane, so I only put it in for cooking with the rangetop. I installed a cast iron boiler that runs on oil for backup if needed. Then I modified it to be more efficient than originally designed. We also have an electric water heater that remains permanently switched off unless the solar is shut down for more than about three days or in the event of severe winter conditions for an extended period. In the end, the cost of heating is insignificant

Be sure to include practicality in your design considerations. For instance, you might sacrifice a bit of theoretical R value for much simpler construction or lower cost or stronger structure. R value is only one of many considerations

I was initially told (on the phone) by National Grid that I can't dig the line for the electrical conduit. We'll see as I get closer and someone comes out to give me a firm price, etc.

What info can you point me to for your Steel Frame? I'm wondering if that's the way to go vs. timber frame since the style of house I'm looking at wouldn't benefit from the timber frames.

 

[Raspy]

Chris,

I dug my trench, installed the pull boxes and installed the conduit according to the power company's specs. These were minimum 5' deep to the top of the conduit, approved pull box every 100' and 3" PVC conduit with sch 80 risers. They also wanted a pull line installed in the conduit. Then they inspected it and installed the wire, etc.

My 48 X 60 steel frame came from Miracle Steel (now out of business) and was designed to be a steel shop building. I added overhangs and deleted the external steel siding so I could build it with conventional wood framing. The roof perlins are 2X10s sitting on 24" centers on steel trusses placed on 12' centers with a 4 & 12 pitch. Roof is double sheeted with OSB.

 

[dave1949]

I was initially told (on the phone) by National Grid that I can't dig the line for the electrical conduit. We'll see as I get closer and someone comes out to give me a firm price, etc.

<snip>.

There are third party contractors here in Maine that install electric service that is accepted by the utility. They usually are less expensive. The only difference I could find between the utility and contractor install is if the utility does it they will maintain the line to the transformer (last pole in my case). If the contractor does it, then tree trimming and repairs are on me. I chose the utility but I only have three poles, about 600' so the price difference wasn't that much.

You could check into that to see if it is an option for your location.

 

[Redneck in training]

We have geothermal HP with floor heating/ forced air AC in our current house but if I would do it again I would do mini splits. We have one unit with two indoor handlers in my shop office and guest room and I like them better than geo. Not speaking about the cost of the geo plus floor heating and forced air. Geo costs at least three time as much as mini splits even though we did a kot of the work DIY.[/QUOTE

I agree with you on this point - We have a very low cost for our GSHP and it works well but I also have 2 mini-split units (for ares that duct work was difficult to get to) and would much rather have $18,000 of PV on my roof along with a couple more mini-split units: Put out warmer air in heating mode and worked this winter at -5' F, able to control each area independently, have back up if a unit breaks down, lower peak load than my GSHP along with well to pump water.

DIY PV is very quick pay back (our electricity is ~ $0.13/kWh) - looking into adding it to current house but most likely will wait and install during the build of next house.

How large of a system do you have that triggered the "industrial generator" interpretation? around here I think it is 15 kW

Here it is 10 kW peak DC. We have 24 kW peak DC with room on racking for another 8-10 kW. It should generate little over 36,000 kWh/year. I figured when I add split unit heat/AC in the shop it will generate just about what we will use. There is a link to our PV under my signature.

Here is a link to passive heated building not to far from where I live: The Zen of Passive Solar Heating Panel Design

 

[KiwiBro]

This should be an interesting exhibition

The Battery Show | Home

 

[KiwiBro]

Regarding isolating the slab from ground temp, I have used a system of interlocking plastic domes called cupolex . no serious foundations needed unless significant point loads. Instead, it acts like what we call here a floating or raft floor.

Cupolex Commercial Residential Gallery | Cupolex Building Systems

Generally touted as a way to conserve concrete but can decide what top thickness required if chasing thermal mass. Not complete isolation but good enough compromise given the price and time savings.

 

[Raspy]

Regarding isolating the slab from ground temp, I have used a system of interlocking plastic domes called cupolex . no serious foundations needed unless significant point loads. Instead, it acts like what we call here a floating or raft floor.

Cupolex Commercial Residential Gallery | Cupolex Building Systems

Generally touted as a way to conserve concrete but can decide what top thickness required if chasing thermal mass. Not complete isolation but good enough compromise given the price and time savings.

This can also be done with "void forming", which accomplishes the same thing, but should be simpler and cheaper to do because it uses a cardboard type material that goes away and leaves open space.

Isolation from dry ground is something I don't worry about. Heating some dry ground below the slab with direct conduction, only increases the affective mass somewhat and seems the same as increasing the slab thickness. In my case I put in an 8" slab to deliberately increase the mass. Heating some ground under the slab does not necessarily mean heat loss.

Some radiant is designed to be as low mass as possible and some to be very high mass. Each has their value for specific applications. For instance, a low mass system could give you a quick shot of heat in the morning without a lot of BTU loss when nobody is home during the day and a high mass can act as partial storage to lower the average solar temperature and actually increase efficiency. It also stabilizes the temperature in the house. In my case, I like the stability, even though I like windows open as much as possible. When heat is needed, it often doesn't have as far to go, or as much to make up and severe winter temperatures in the garage can be weathered longer without freezing a pipe.

In multi-floor homes the slab basement can take the cold edge off the entire house. Then radiant zones in the bathrooms and kitchen greet people when they get up, by warming their feet. Since the baths and the kitchen are relatively small areas, the boiler appears to be oversized and heating response is fast. Timing the thermostat means the floor is warm when they get up, but does not stay warm all day, therefore the bill stays low and the overall temperature stays even. A warm greeting without overheating the house.

Many older radiant heated homes are VERY inefficient because of large single pane glass and no roof or wall insulation. In those cases, it's very important to time the system. The underslab, potential losses are not only impossible to deal with, but not a measurable portion of the overall problem.

 

[KiwiBro]

Another we looked at is that former being a series of bladders that double as water storage once concrete has cured.

 

[KiwiBro]

The Battery Show exhibition is on soon ( The Battery Show | Home ). I suspect two things:

1. What will be revealed at that show will amaze many people. I haven't been so stoked with the near-commercial battery tech coming down the pipeline as I am right now. People use the term too often but it's game-changing, me thinks.

2. The financial ponzi scheme that has propped up utterly unsustainable greed and immorality is likely to topple off a cliff, wiping out almost all substantial funding routes open to all but a few of the great tech advances. The race is well and truly on between bringing these advances to market, and there being a market left to tap into to fund such tech. Personally, if I had to choose between getting the tech and the next great economic crash, I'd choose the latter because the mo-fo world deserves an absolute ***-kicking over its behaviour for too many years now, as much as it will also hurt many people who don't deserve it.

 

[Redneck in training]

I was reading other solar forums and they indicated that battery life span is the biggest (and most costly) issue / concern.

Iron Edison makes Ni-Fe batteries that can tolerate 90% discharge. The initial investment is higher than more common batteries but since they last longer they are actually cheaper.
https://ironedison.com/preconfigured-off-grid-systems