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diy solar

In need of off-grid design guidance

cdnorth

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Joined
Jun 29, 2021
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36
Hello Everyone,

Thanks in advance for any advice you have, I eventually overanalyze everything and I feel like I'm not really making much progress so I'm turning to the forum! We are developing a piece of raw land to have two 24' diameter yurts that will be fully off grid. I'm trying to figure out the best way to provide power to both of them as it seems we have just about every other aspect relating to site work planned out and are ready to get going on designing the spaces now! Both of them will likely be used as short term rentals at times so I'm running into some issues trying to estimate loads and would appreciate any input from you experienced folks! So far, below is where I am at for each yurt. A couple of questions, most relating to solar but some to off grid in general:

1. Do all of these loads seem reasonable? Am I grossly over/underestimating anything? Is there anything major that I seem to be missing?
2. How should I calculate a variable speed heat pump daily consumption? I'm looking at Mr. Cool DIY units but am totally open to suggestions on unit model and consumption data I should use to size the system.
3. We were planning to use a propane water heater, stove, fridge, but would love to do electric if it's not cost prohibitive to do so. From an operations standpoint it would be certainly be easier and equipment would be cheaper I believe. Any suggestions here?
4. Would it make sense to have one inverter serve both yurts? Have one main breaker for each space but the main inverter serve both
5. I'm looking at the all-in ones and am being drawn in by the apparent ease of install and cost. I keep going back and forth in the Growatt/MPP vs. Solark or similar. I've literally read just about every article I can find and have spent so many hours going back and forth. If you have any input here, that would be helpful. I'm thinking if both yurts can be fed off of one, that would make the Solark less of a gut punch!
6. To throw another wrench on the pile, we just received a permit to run a campground (well glamping that is) on the property as well with up to 12 sites. I'm definitely excited if/when we move forward with this but I do like the idea of having the solar setup be expandable so we can just expand it as necessary to accomodate this as well.

Sorry for the long list of questions, there's just such a learning curve and I'm trying not to over-research and eventually get tired and order something that isn't ideal, I greatly appreciate any guidance!

Best,
Cole



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Hello Everyone,

Thanks in advance for any advice you have, I eventually overanalyze everything and I feel like I'm not really making much progress so I'm turning to the forum! We are developing a piece of raw land to have two 24' diameter yurts that will be fully off grid. I'm trying to figure out the best way to provide power to both of them as it seems we have just about every other aspect relating to site work planned out and are ready to get going on designing the spaces now! Both of them will likely be used as short term rentals at times so I'm running into some issues trying to estimate loads and would appreciate any input from you experienced folks! So far, below is where I am at for each yurt. A couple of questions, most relating to solar but some to off grid in general:

1. Do all of these loads seem reasonable? Am I grossly over/underestimating anything? Is there anything major that I seem to be missing?

Welcome to the forum.

Yes. No way a hair dryer uses 80W. Most use closer to 1000W.

See #2

2. How should I calculate a variable speed heat pump daily consumption? I'm looking at Mr. Cool DIY units but am totally open to suggestions on unit model and consumption data I should use to size the system.

Example: 12000BTU/hr 20 SEER mini split will use 12000/20 = 600W

3. We were planning to use a propane water heater, stove, fridge, but would love to do electric if it's not cost prohibitive to do so. From an operations standpoint it would be certainly be easier and equipment would be cheaper I believe. Any suggestions here?

Fridges that run off propane take an insane amount of AC power to run them. A typical RV fridge that's only 7.6cu-ft can require up to 5kWh/day. A 10cu-ft energy efficient compressor type fridge will only use about 0.9kWh.

Electric water heaters can be used opportunistically when you have surplus solar.

4. Would it make sense to have one inverter serve both yurts? Have one main breaker for each space but the main inverter serve both

Depends on total power requirements.

5. I'm looking at the all-in ones and am being drawn in by the apparent ease of install and cost. I keep going back and forth in the Growatt/MPP vs. Solark or similar. I've literally read just about every article I can find and have spent so many hours going back and forth. If you have any input here, that would be helpful. I'm thinking if both yurts can be fed off of one, that would make the Solark less of a gut punch!

Yep. The price of the cheap AiO is appealing, but there are enough complaints and issues with them to make me steer away from them for anything I truly want to depend on.

6. To throw another wrench on the pile, we just received a permit to run a campground (well glamping that is) on the property as well with up to 12 sites. I'm definitely excited if/when we move forward with this but I do like the idea of having the solar setup be expandable so we can just expand it as necessary to accomodate this as well.

To do this you need to design the end system and figure out how to piecemeal it.

Sorry for the long list of questions, there's just such a learning curve and I'm trying not to over-research and eventually get tired and order something that isn't ideal, I greatly appreciate any guidance!

Best,
Cole



View attachment 54600
View attachment 54601
 
I like the idea of a separate system for each yurt. Many inverters you would need to make sure you don’t turn on more than two or three high wattage appliances at once. This avoids someone knocking on your door at night time to turn off the heater to make microwave popcorn.

For the campground, I can;t say much about designing the system. My RV has two 50 amp circuits coming into it, which is your average power input for a fifth wheel. A house has a 200 amp input. Getting solar power put in an off grid fashion with batteries may end up pricing anyone out who would want to stay. Having solar installed that back feeds into the grid would be a much cheaper option.

For planning, locally I use $15k per 5 kw of grid tied panels installed by a contractor who does all the work for you. Rebates would bring the price down. I think 5 kw of panels on average might cover what an RVer expects to use in a campground During the season they turn air conditioning on, which around where I’m at is all day and night most months of the year.
 
Welcome to the forum.

Yes. No way a hair dryer uses 80W. Most use closer to 1000W.

See #2



Example: 12000BTU/hr 20 SEER mini split will use 12000/20 = 600W



Fridges that run off propane take an insane amount of AC power to run them. A typical RV fridge that's only 7.6cu-ft can require up to 5kWh/day. A 10cu-ft energy efficient compressor type fridge will only use about 0.9kWh.

Electric water heaters can be used opportunistically when you have surplus solar.



Depends on total power requirements.



Yep. The price of the cheap AiO is appealing, but there are enough complaints and issues with them to make me steer away from them for anything I truly want to depend on.



To do this you need to design the end system and figure out how to piecemeal it.
Thanks for the reply! I knew the hair dryer would get brought up, normal hair dryers were causing me stress until I found some options for battery powered that we would likely provide. Regarding SEER, that would be for almost ideal testing conditions and would likely operate at lower efficiency. The manufacturers list a maximum input which is what I used and I assume that would be correct for the inverter demand but I'm not sure how to assume how often it is running at partial capacity for battery demands. Thoughts?

I'm on board with an efficient electric fridge, thanks for convincing me! My only problem with the water heater is that I don't think I can assume someone renting the place would run it opportunitically. If it was just for us I think that would work, ill probably end up oversizing everything I guess.

I'll put some more assumptions down for the expansion and see if it makes sense to have one power house and I'll keep thinking about going with a better all in one. Thanks for all the input, giving me more to think about!
 
I like the idea of a separate system for each yurt. Many inverters you would need to make sure you don’t turn on more than two or three high wattage appliances at once. This avoids someone knocking on your door at night time to turn off the heater to make microwave popcorn.

For the campground, I can;t say much about designing the system. My RV has two 50 amp circuits coming into it, which is your average power input for a fifth wheel. A house has a 200 amp input. Getting solar power put in an off grid fashion with batteries may end up pricing anyone out who would want to stay. Having solar installed that back feeds into the grid would be a much cheaper option.

For planning, locally I use $15k per 5 kw of grid tied panels installed by a contractor who does all the work for you. Rebates would bring the price down. I think 5 kw of panels on average might cover what an RVer expects to use in a campground During the season they turn air conditioning on, which around where I’m at is all day and night most months of the year.
I haven't seen anyone running multiple homes on one system but I'm assuming it can be done. Maybe it is just easier to have separate, just trying to simplify the amount of spaces I need for solar since everything will be ground mounted.

Fortunately for the electrical system on the campground side, we are not planning to have any RV sites, it will be a combination of bring your own tent and pre-setup "glamping". Perhaps a few lights and a couple of outlets at each site with a central restroom facility having the majority of the electrical demands. Thanks for all the input!
 
My only problem with the water heater is that I don't think I can assume someone renting the place would run it opportunitically.

I use a hot water storage tank (3000L) which has multiple inputs. I can heat it electrically in summer, or use wood in winter - or a combination thereof - depending. Excess solar (when the battery is full) goes into the tank automatically. You could do something like that, or just go with propane (which I hear is cheap across the pond) on demand heater. Redundancy is key when you're off-grid.
 
I use a hot water storage tank (3000L) which has multiple inputs. I can heat it electrically in summer, or use wood in winter - or a combination thereof - depending. Excess solar (when the battery is full) goes into the tank automatically. You could do something like that, or just go with propane (which I hear is cheap across the pond) on demand heater. Redundancy is key when you're off-grid.tya

I use a hot water storage tank (3000L) which has multiple inputs. I can heat it electrically in summer, or use wood in winter - or a combination thereof - depending. Excess solar (when the battery is full) goes into the tank automatically. You could do something like that, or just go with propane (which I hear is cheap across the pond) on demand heater. Redundancy is key when you're off-grid.
That sounds very intriguing! How exactly is yours setup electrically? I believe I've seen some all in one's that specifically have a separate port for excess solar energy to go to one appliance, seems ideal for this. Say the inverter is rated for 6000W output, what size heating coil would you have on this storage tank that wouldn't exceed the inverter limits? I could see a situation where the inverter can't handle the loads and the excess solar energy at the same time. Does the inverter just max itself out and provide what it can to your storage tank?
 
I'm putting DC from the solar side directly in the tank, not through the inverter. There is quite a bit of custom work involved in my set-up, but I'm guessing if you have an all-in-one that has this, why not. A 6000W inverter can handle a 6000W heating coil - it's a resistive load - but of course, no other loads. You can size based on your usage.

My tank looks like this :

energiavaraaja-gebwell-g-energy-ev-3000l-3-bar-1.jpg


Keep in mind that water from this tank never leaves the tank; instead it is considered a 'battery' where exchange coils take heat out for hot water. It has electrical and coils for input as well.
 
Thanks for the reply! I knew the hair dryer would get brought up, normal hair dryers were causing me stress until I found some options for battery powered that we would likely provide.

Link?

Regarding SEER, that would be for almost ideal testing conditions and would likely operate at lower efficiency. The manufacturers list a maximum input which is what I used and I assume that would be correct for the inverter demand but I'm not sure how to assume how often it is running at partial capacity for battery demands. Thoughts?

It's actually a pretty good "average". If you run for several hours, that average should reflect Wh used.

I'm on board with an efficient electric fridge, thanks for convincing me! My only problem with the water heater is that I don't think I can assume someone renting the place would run it opportunitically. If it was just for us I think that would work, ill probably end up oversizing everything I guess.

Agree. You can't trust the unwashed masses.
 
I'm putting DC from the solar side directly in the tank, not through the inverter. There is quite a bit of custom work involved in my set-up, but I'm guessing if you have an all-in-one that has this, why not. A 6000W inverter can handle a 6000W heating coil - it's a resistive load - but of course, no other loads. You can size based on your usage.

My tank looks like this :

energiavaraaja-gebwell-g-energy-ev-3000l-3-bar-1.jpg


Keep in mind that water from this tank never leaves the tank; instead it is considered a 'battery' where exchange coils take heat out for hot water. It has electrical and coils for input as well.
That looks like a very interesting idea, might have ti research a bit more before I just end up with propane instantaneous!
 
Link?



It's actually a pretty good "average". If you run for several hours, that average should reflect Wh used.



Agree. You can't trust the unwashed masses.
Link?



It's actually a pretty good "average". If you run for several hours, that average should reflect Wh used.



Agree. You can't trust the unwashed masses.
Here's a link to the one I was looking at, theres a few others out there as well but this one definitely seems nicer wkth efficient loads and according to the marketing a pretty good battery. It's showing 120wh battery and 4 hours to charge so that would make it a 30 watt charger I guess. For some reason I saw 80 but that seems to be overstating it a bit.


So for example regarding the ductless split, would you say that 600 watts for 12 hours a day in the middle of the summer? Assuming it's cloudy (and running strictly off battery) there would not be as much a need. We're located in northern arizona, gets fairly cold in the winters but nothing crazy and peaks around 90 in the summer so even cooling is minimal. I want to make sure we're covered but saying it's running 24 hours without solar power seems excessive to assume 14400 wh and then backup days when cloudy could lead to a massive battery pack for a relatively small load. Is this correct? Thanks again for all the help, I think I've basically gotten everything to start running with the design!
 
Here's a link to the one I was looking at, theres a few others out there as well but this one definitely seems nicer wkth efficient loads and according to the marketing a pretty good battery. It's showing 120wh battery and 4 hours to charge so that would make it a 30 watt charger I guess. For some reason I saw 80 but that seems to be overstating it a bit.


Electrically produced heat is very costly. Typical hair dryers use about 1000W because that's what it takes to dry hair in a worthwhile time frame.

There's a claim of up to 4 hours run time depending on settings... I'm sure that's only with the fan on low and now heat. Specs:
  • Cordless & Battery Operated with 120 Wh of Battery Capacity
  • Quiet Operation
  • High energy density Lithium Ion Cells with Silicon Anode Technology
  • Ability to Operate continuously while plugged in to the wall (AC Power)
  • Dual 500W Heating Coils (DC and AC)

To operate it on high, like a regular hairdryer, you're looking at 120/1000 = .12 hr or 7.2 minutes. This is not opinion. This is math. Then you need a 90 minute recharge according to the claims.

IMHO, this is vaporware in terms of usability for 30 minutes or to only use 40Wh of power. For it to work for 30 minutes, it could only put out 240W before the battery is depleted. I think there's a reason they designed it to work continuously while plugged into AC power. It would completely suck otherwise.

Best to measure "normal" use of a legit hairdryer and measure it with a kill-a-watt. Then you'll know what it really takes.

If one can get their hair dry in 7.2 minutes, then you're golden, but that's 3X more than the spreadsheet's 40Wh.

Lastly, but above all else, if the wife is unhappy with the performance of the hair dryer, the hair dryer is no good. :)
 
So for example regarding the ductless split, would you say that 600 watts for 12 hours a day in the middle of the summer? Assuming it's cloudy (and running strictly off battery) there would not be as much a need. We're located in northern arizona, gets fairly cold in the winters but nothing crazy and peaks around 90 in the summer so even cooling is minimal. I want to make sure we're covered but saying it's running 24 hours without solar power seems excessive to assume 14400 wh and then backup days when cloudy could lead to a massive battery pack for a relatively small load. Is this correct? Thanks again for all the help, I think I've basically gotten everything to start running with the design!

Those are based on yearly averages, but what else do you go off of? You definitely don't go off the max power as that's definitely wrong-er.

FWIW, cloudy days still produce juice depending on ambient light. Pretty common to see 20-30% and more of rated in N. AZ (our place is ENE of Show Low off 61 towards St. Johns) on cloudy days. Temps there have been at 100°, and my neighbor, who hasn't had A/C for 25 years, is sizing a system.
 
Electrically produced heat is very costly. Typical hair dryers use about 1000W because that's what it takes to dry hair in a worthwhile time frame.

There's a claim of up to 4 hours run time depending on settings... I'm sure that's only with the fan on low and now heat. Specs:
  • Cordless & Battery Operated with 120 Wh of Battery Capacity
  • Quiet Operation
  • High energy density Lithium Ion Cells with Silicon Anode Technology
  • Ability to Operate continuously while plugged in to the wall (AC Power)
  • Dual 500W Heating Coils (DC and AC)

To operate it on high, like a regular hairdryer, you're looking at 120/1000 = .12 hr or 7.2 minutes. This is not opinion. This is math. Then you need a 90 minute recharge according to the claims.

IMHO, this is vaporware in terms of usability for 30 minutes or to only use 40Wh of power. For it to work for 30 minutes, it could only put out 240W before the battery is depleted. I think there's a reason they designed it to work continuously while plugged into AC power. It would completely suck otherwise.

Best to measure "normal" use of a legit hairdryer and measure it with a kill-a-watt. Then you'll know what it really takes.

If one can get their hair dry in 7.2 minutes, then you're golden, but that's 3X more than the spreadsheet's 40Wh.

Lastly, but above all else, if the wife is unhappy with the performance of the hair dryer, the hair dryer is no good. :)
Haha, I totally understand, for running a short term rental, it may be worth ordering something like this and just seeing. I should probably assume the 500W at a minimum though to be safe! At the end of the day, it's still an "off grid" accommodation and someone may just be happy to have a hair dryer available. Best case, the hair dryer has figured out how to stage the heaters and airflow to get an equivalent discharge temperature that actually works well. Fortunately, my wife let's her hair air dry and says she could go without entirely! :)
 
Those are based on yearly averages, but what else do you go off of? You definitely don't go off the max power as that's definitely wrong-er.

FWIW, cloudy days still produce juice depending on ambient light. Pretty common to see 20-30% and more of rated in N. AZ (our place is ENE of Show Low off 61 towards St. Johns) on cloudy days. Temps there have been at 100°, and my neighbor, who hasn't had A/C for 25 years, is sizing a system.
I lived in show low for one year and my parents have been up there for I think 12 years now, great area! We'll be quite a ways west, just north of williams, elevation is very similar to show low and so is the weather. There's a lot of people who don't have AC in those areas but I'd like to add if it doesn't cause massive issues, which it doesn't seem it will. I think the 20-30% of max makes sense but my engineer brain is telling me to size the inverter for the maximum just incase! I'll refine my calcs based on our discussion, add in some information for the future campground data and see where I land! Thanks again for all the help, this forum seems tremendously supportive of helping!
 
That looks like a very interesting idea, might have ti research a bit more before I just end up with propane instantaneous!

Also depends on the cost of your fuel. If propane is cheap and practical, it's a good option. Over here, it's not. I only use it for cooking in winter (in summer: outdoor kitchen or induction). Wood on the other hand is cheap and plentiful here, so that's my fuel of choice for all my heating requirements (and it gets cold here...).
 
Also depends on the cost of your fuel. If propane is cheap and practical, it's a good option. Over here, it's not. I only use it for cooking in winter (in summer: outdoor kitchen or induction). Wood on the other hand is cheap and plentiful here, so that's my fuel of choice for all my heating requirements (and it gets cold here...).
Not sure if I'd say propane is cheap, not nearly as cheap as natural gas typically is but propane would be the only option in that way. Due to fire restrictions being present for a good chunk of the summer, we're already going with propane fire pits at each site so propane water heaters seems to be a natural progression assuming it overcomplicates the solar system.

On another note about the inverters, am I correct to assume that it sounds reasonable to subtract a diversity factor from the overall inverter needs? For example, I want the batteries to be sized for the overall daily need and that makes sense. For the inverter though, I can't imagine that everything will be plugged in and on at once. How do people factor this in, just take a best reasonable guess with a factor of safety of what you think will be reasonably on all at one time? Is it possible to implement a control strategy to prevent larger loads from turning on if the inverter is highly loaded? What I'm thinking is that I don't care if the heat pumps come on right now or in five minutes (or 30 minutes for that matter) but I do care if the lights shut off because the heat pump kicks on and overloads it. If I have a 6kw inverter, is there a way to lock out the heat pumps (or similar loads) unless the current load is under 3kw or something similar? Just trying to think about controls and if that's even possible. It seems overkill to severely oversize the inverters for non-critical loads.

Sorry for all the questions, I feel like I've researched a lot and am narrowing it down and hopefully can start laying out the final design shortly and have everyone tear it apart! Trying to minimize the amount of feedback I get then and would rather get it now. Thanks so much for all the help!
 
Is it possible to implement a control strategy to prevent larger loads from turning on if the inverter is highly loaded?

It's possible, but I don't think this exists out of the box. I'm working on something that could be used to do just that, but it's in the early stages of development and definitely not something out-of-the-box. You need something that acts as a supervisor and has an overview of everything and can control individual devices. One possibly easier method would be to put the higher loads on a timer and make sure they don't overlap. That should be easier, using a socket timer for example.
 
Just my own observation here: why electrical outlets at tent sites?! I read, “off-grid, yurt, solar, camping, rental”…and then hair driers and outlets at tent sites come up. Incongruous with a remote stay?

It’s like listing ducks, chickens, geese, turkeys, pheasant, partridge and bicycles; something seems off. I feel like you haven’t sorted out your target audience/customer.

Just my thoughts anyways. I know off grid, remote, and primitive are not all in the same subsets, but I just am not seeing the market.
 
Just my own observation here: why electrical outlets at tent sites?! I read, “off-grid, yurt, solar, camping, rental”…and then hair driers and outlets at tent sites come up. Incongruous with a remote stay?

It’s like listing ducks, chickens, geese, turkeys, pheasant, partridge and bicycles; something seems off. I feel like you haven’t sorted out your target audience/customer.

Just my thoughts anyways. I know off grid, remote, and primitive are not all in the same subsets, but I just am not seeing the market.
Hello,

Thanks for the thoughts! We're not exactly going for remote, we're about 10 miles from town with no existing electrical service so everything has to be off grid. I know we have a lot going on but we will have two higher end yurts go up first and then we will be building out a campground with (eventually) 12 "glamping" sites. These sites will basically be a hotel room inside a canvas tent so it's definitely higher end than just camping.
 
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