Solar Electric Project

[hayden]

I've got another project going in parallel with my shop construction. My place is 100% off the grid with power being supplied by solar panels and a backup generator. It works great, but as we use the house more and more we have found the system to be undersized and the generator runs much more than I'd like.

So, I'm doing a major upgrade of the system. I'll be expanding the solar panels from a little over 600W to over 3100W, and will be replacing the 4KW 120V inverter with a 6KW 240/120 split phase inverter. On the battery front, I'll be changing from a 24V bank to 48V and jacking up the capacity. I haven't nailed down the exact battery sizing, but I'm thinking of something around 1000Ah @ 24V. My current bank is 800Ah @ 24V.

Since I have a concrete truck coming for my shop foundation, I decided to set the solar panel mounting poles and footings. The first pictures are of the trench I dug for the footings. These babies are 6' deep and will be formed with 36" diameter Sonotubes. There will be two poles spaced 10-11' apart. The poles are aligned E-W so the panels face due south without shading each other.

 

[hayden]

Here are the sonotubes and the poles being prepped. The tube was 12' long and I cut it in half for the two footings. These things are huge, and you can get a sense of it by the way they fill the garage door.

The poles are 16' long, 6' schedule 40 galvanized pipes. Holly molly steel has gotten expensive. The 21' pipes these were cut from cost almost $600 each! Yikes.

I put two riser clamps on each pipe offset by 90 deg. On each clamp I replaced one of the bolts with a much longer bolt that I could use to attach prop poles. I also shackled a lifting chain to the other side of one clamp.

 

[hayden]

And here are the poles and sonotubes getting set in position. I put the tubes in the hole first, then worked the pole into the tube, It was a bit tricky doing it. My tractor was about 2' short of being able to lift the poles high enough to just drive them over the tubes and lower them down. As a result, I lifted them as far as I could with the forks, then hefted the end into the tube by hand. I used the forks because the frame has a nice D-ring that I was able to shackle my lifting chain to. The forks also provided side guards just in case the pole got a way somehow, though it would have been difficult because the chain was shacked at both ends.

Once the pole was down in the hole I could edge the tractor into position to set the pole. I pushed the pole to center the end in the hole, then my wife lowered the pole until the lifting chain went slack. Once the weight of the pole was on the ground, I bolted my braces to those long bolts on the clamps and worked the pole until it was plumb. After the pole was set and braced, I climbed into the hole and leveled the sonotube, then back filled around it with a few inches of crushed stone to keep it from walking around while it's being poured.

 

[3RRL]

Peter, nice project...I was just reading your updates on your other thread too.
I guess it's too late now, but I was going to recommend putting those poles farther apart. It's Summer now and the Sun is high, but as Winter comes around and the shadows get low, you might be surprise as to where the shadows are cast. And that's when you need them to work best since there's less daylight. I don't know if you've seen my thread about my solar project, so I went through all that already.
Will you have the ability to rotate or move the direction your panels are facing? Mine are dual axis but my neighbor sets his manually about 2 or 3 times a year to get the best angles.

 

[hayden]

I'm not planning to use trackers. Up here at the north pole (Vermont) they don't have the advantage that they do further south. If I was using trackers I'd likely have a problem with shading, but the panels will always be facing due south and the two arrays are in the same plane at all times. Right now I adjust the tilt manually twice a year.

I checked the site with a solar pathfinder to be sure my exposure was good, so I'm pretty sure I'm OK. The only issue might be that one pole stand a bit higher than the other so late in the day I might get some shading of the eastern array. However, I've got trees that will shade everything later in the day for much of the year. I'm planning to leave the poles at different heights for now. If it's a problem I can always cut the pole down to match the height of the lower pole.

My fingers are crossed...

 

[hayden]

In between rain showers I managed to get all the electrical conduit in place where it will be embedded in the concrete footings. This approach will take some of the strength away from the concrete, but I think there will still be plenty to hold the main pole.

As you can see from the pictures, there are quite a few pipes. Some of it is for the solar arrays, and some is in anticipation of a hydro shed another 150' down the hill. I figured I'd use the conduit run from the panels to the house for both devices, even though I'm only putting in the solar now. I also have two conduits running in parallel. One for high voltage DC from the panels and ultimately the hydro generator. Code requires that these be in their own conduit and not be shared with other cables. The second parallel pipe is for low voltage control wires. Right now I don't need any for the panels, but some day I might put in a tracker or other monitoring device. I'm also considering relocating my TV dish to the side of the pole so I might need to run coax. Both the high and low voltage conduits then continue on to the eventual hydro shed. For now they will be capped off and burried.

There is also one pipe that runs between the solar mount poles to consolidate the power at one pole before running up to the house.

The pipes running to the house are capped off too for now. Later I'll trench and extend them into the house, but for now I wanted to jump on the poles (actually the concrete footings) while I have concrete tucks coming through.

Finally, I'm ready to pour and hope to tag onto a footing pour tomorrow.

 

[RichNJKubota]

Great job. Does your state of NH/VT have any rebates or other incentives on PV systems? And if so, does the PV system need to be grid tied?
A 600 watt system will not make much power but a 3100 watt system will do much better. Is this your year round house? Hunting cabin? Or?
What about the rest of your energy needs like water heating and space heating?

 

[hayden]

I need to check and see if anything has changed, but last I looked VT (where the property is located) only offered incentives for grid-tied systems. Oh well.

The house is 200 years old but was never electrified and sits about 3/4 mile from the last pole. About 10 years ago I built a trial system to see how inverter technology worked, etc. The first system was a 1 KW 12V inverter/charger, 4 deep cycle marine batteries, and a generator. It was a great success, so I added about 150W of solar panels. We were only using the house on occational weekends so the panels were mainly to keep the system charged up while we were away.

A couple of years later we started using the place more frequently, though still on weekends, and we added a bunch of creature comforts like dishwasher, microwave, washer/dryer, TV, etc. To support that I upgraded to a 4KW 24V inverter/charger, upped the panels to the current 600W+, added a quality built-in 4KW generator, and switched to good quality batteries more suitable to the purpose. It's powering the TV I'm watching now, plus the laptop and satellite internet I'm typing this on.

Now I'm retired (though still pretty young) and we are spending about half our time here. I'm also building a shop that needs to be powered. When we are here the generator runs anywhere from 30 minutes to several hours each day even if the sun is shining. The inverter size of 4KW may seem small, but it has never been a limiting factor, including while we have had construction underway with multiple compressors and other power tools running. However, I use more KWh per day than the panels support - by a lot. The other issue is that my existing system is 120V only and I have the two legs of the 240V split-phase panel tied together. I'd rather be running true 240/120, especially out to the shop. All this has led me to this next upgrade.

One thing we did when we modernized the house was to pay special attention to electric usage knowing that it would be a limited resource. It's amazing what you can do if you pay just a little attention to conservation. At any point during the day or evening we typically are drawing between 10 and 20A from the batteries. That's 250-500W to run the entire house. About half of that is the TV/Sat TV. To get that, we started by pushing everything we could to propane. The heat, hot water, dryer, stove, generator, and even the fridges are propane. Heat is circulating hot water so the only power consumption is a 75W circulator pump. Forced hot air, in contrast, consumes a bunch more than that for the air blowers. Lights are all CF, and I select appliances very carefully. Most are needlessly wasteful. Our dishwasher, for example, had a water boost heater element and an air dry heater. I disconnected both of them and have never missed either.

The best part of the whole thing is that you can live off the grid but still live a normal life. I have all sorts of power tools, compressors, welders, etc. and use them as I would anywhere else. It just takes a little effort and ingenuity.

Peter

 

[cityfarma]

For those who lust after being able to do similar or simply have an interest in renewable energy, have a look at Home Power Magazine: Solar | Wind | Water | Design | Build. they have a magazine available as download or hardcopy that has been of great interest to me over the years.

The magazine covers solar, wind and water power as well as how to reduce the energy you consume.

Cityfarma

 

[hayden]

Agreed - Home Power is a great magazine (probably the only) on the subject.

 

[RichNJKubota]

I used to subscribe to HomePower magazine. Then I dropped the subscription because where I lived was not suitable for PV or other alternative power (middle of small town on tiny lots and lots of trees). But the seeds were planted. We moved and now I live in a solar heated house with PV system and solar hot water system. The house is zero-energy - meaning the solar systems produce all the energy the house needs.
That's why I asked allot of questions. And I see you too have the bug to be more self sufficient. Of course, you have to be since you have no connection to the grid. We are grid tied here.
Peter - you may want to consider a solar hot water system. We have no backup. Just solar hot water and so far we've done OK. It's been running now for about 10 months. There were a few days in the dead of winter when we washed dishes by hand and either took warmish showers or waited for a sunny day. On sunny days in the winter there is enough hot water left over to provide a bit of heat to the house.
One day I'll put a small electric whole house instant hot water heater for backup. Probably before next winter.

 

[saltman]

Great info. I am going to be going through the same thing as you in about a year. The difference being that I am way south of you and have way less energy demands due to the temperatures and consistant sunlight. I am in San Diego County and my location gets maybe 7 inches of rain/ cloudy weather a year. (few days a year)

My home will be off grid and as in Vermont no incentives for any rebates here in California unless your on grid.

My system will be just a big larger than your original system to power a 1700 square foot house. I will use propane for heat, to operate the stove, hot water heater and the back up generator. I may add a panel so I can use a regular Refrigerator so I will have about 1500 watts of solar panels.

Am I being too optimistic to think I can power a well insulated and totally low energy designed home in a warm climate with 4.5-6 kilowatt system?

I am a conservationist.. (frugal) and my on grid power consumption in and old leaky house with old appliances/ T.V's I use double what I plan for my new home.

 

[hayden]

Glad to see another addict. My name is Peter, and I have a solar system. I haven't touched the grid for years.

I haven't done hot water and would like to one day. I just haven't had the time to learn enough to design a system, confirm it will meet out needs, etc. I think it's one of the more effective ways to directly tap solar energy and is too easily overlooked by most people, including me. One more project to add to the list......

 

[hayden]

Saltman,

Glad to hear you are joining the ranks... and glad to see you are looking at your overall energy consumption as part of moving off-grid. The economics of conservation is way better than power generation. Besides, blind consumption is a big part of our current energy problem and people need to become more aware of the energy consequences of everything they do.

I think a 4-6KW system will be plenty. Unless you have electric heat, cooking stove, AC, a FHA heating system, or some other large device it will be more than enough. In the 8 years or so of using a 4KW system we have never maxed it out, and we never pay attention to what's running at the same time. I've seen the microwave and a hair dryer running at the same time and nothing trips. The better inverters can all crank out a good bit more than their rated power for a number of minutes which will cover almost any situation. I actually think many inverter installations are grossly oversized, but that's a different thread.

I've also found the 4KW generator to be more than enough even though it's quite small. I could charge my batteries a little bit faster with a bigger generator, but not by a lot since I'm almost running at the max charge rate for the battery bank size. Also, propane (and gas and nat gas as well) generators are most efficient at or near full power, so having them fully loaded while you are charging is generally good. An oversized generater will just run lightly and inefficiently and waste fuel. The inverter chargers and/or the battery bank size will also limit how fast you can charge the batteries and consequently how much load it's possible to put in the generator.

 

[jim_n_nh]

You most likely know of this but near Rutland in July is Solarfest. I have gone for several years... While not offgrid I have reduce my electric load to almost nothing. Super insulated house heated by passive solar and a Woodstock woodstove.

 

[srossman]

One day I'll put a small electric whole house instant hot water heater for backup. Probably before next winter.

Rich, It's great to see someone fairly close by that has gone completely solar. I've had the seed planted in my head for a while now, and wasn't sure if it would be feasible to try and go off the grid.
You may want to look into a propane fired whole house hot water heater. When my water heater when last year, I looked at an electric whole house hot water heater and determined that it takes a lot of electricity to be able to run the electric on demand hot water heaters, and the gpm wasn't that good.

 

[TDVT]

Great to see your project. I know it's becoming more common & practical even way up here in VT. I have a big stack of HOME POWER magazines myself.

We had done the preliminary stuff for a grid-tied system but the expense was still too high. Then we went a bought a new tractor, then re-did the roof & shot the solar project all to @#$%. But the kids are off in school so our power consumption has dropped quite a bit. We'll get to it eventually.

I have some solar HW panels I bought surplus, sitting in the barn (for a few years now) & had thought about finally setting them up on a pole mount as you are doing. So I will be paying close attention!

 

[mikim]

When solar is your only option it's worth it ... but to try to go total solar when utility is available with cost savings in mind ... it's just not there. Initial expense of solar has a 10+ yr payback not counting maintenance and replacement. There just isn't any cost savings there at all. And I have a perfect location for a major solar system on the south facing barn roof -- but it just cost too darn much yet. NOW saying that -- I have every intention of using solar here and there as a convenience thing on a limited scale. Outdoor light at the well house. Water pump on a rainwater collection system (to supply the house when/if the well goes out). Lighting & fans at the greenhouse....etc. I wish you and everyone that goes solar the absolute best -- and hope more folks do get into it so as to hopefully drive prices down to make it more feasible for everybody. If more states and utilities like in Cal. would subsidize it better - we could really reduce our use of fossil fuels.

 

[jim_wilson]

It has been a while since I have on TBN - I have been doing some research here and there to figure out if solar electric is a viable option for me. In the past TBN has always been a good source of info for these types of things so I figured I would start checking thru the posts here. MA has put in place a Solar power incentive program which aims to bring the cost of a solar system down - but from my calculations still not down enough to make it a feasible alternative to being on grid. At least not where I am located.

Does anybody have any links to where I could learn more about solar electric power? The Homepower magazine looks interesting - I will check that out.

Any other recommended reading to do - or companies that supply solar equipment?

BTW - I also ran across the thread where you had the pics of the new tractor Peter - pretty nice.

 

[hayden]

When solar is your only option it's worth it ... but to try to go total solar when utility is available with cost savings in mind ... it's just not there. Initial expense of solar has a 10+ yr payback not counting maintenance and replacement. There just isn't any cost savings there at all. And I have a perfect location for a major solar system on the south facing barn roof -- but it just cost too darn much yet. NOW saying that -- I have every intention of using solar here and there as a convenience thing on a limited scale. Outdoor light at the well house. Water pump on a rainwater collection system (to supply the house when/if the well goes out). Lighting & fans at the greenhouse....etc. I wish you and everyone that goes solar the absolute best -- and hope more folks do get into it so as to hopefully drive prices down to make it more feasible for everybody. If more states and utilities like in Cal. would subsidize it better - we could really reduce our use of fossil fuels.

I agree. Off-grid, it makes economic sense right from the start. On-grid, it currently only makes economic sense if there are sufficient rebates. That said, there are lots of people to whom being eco-friendly trumps economics. They are the pioneers who will help drive the volumes that will broaden access to those who only consider the economics. We should thank them for their forward thinking and for paving the road for those less adventurous.