Off-grid system review

[Amy@altE]

Again, much of our energy use will be during the day, in one of the sunniest/dryest parts of Hawaii (350 days of sun). Probably 20-25Kwh during the day, if I'd have to throw a figure out there (including the 3hp water pump, appliances, etc.). At night, we won't use more than 5-10Kwh (led lights, tv, possibly one load of dishes).

Generators are not my specialty, so I can't help you there, but I can show you the math for the solar and batteries, which does in fact line up with the numbers SunKing gave you.

If you are thinking 35kwh a day, I'm guessing 5 sun hours for worst case in Dec, then for the array, 35,000Wh / 5 sun hours / .67 system inefficiencies = 10,447W of solar / 280W SolarWorlds = 38 panels.

35,000Wh / .92 inverter inefficiencies /.5 (50% DoD) x 2 days autonomy x 1.11 (temp compensation for 60F) = 169kWh / 48V = 3519ah 48V battery bank. I know you said it's always sunny, so you may not think you need the 2 days autonomy, but what that also does for you is most days you'll only use 25% of your battery, which will make them much happier than 50% every day.

It's worth it to think of other ways to fuel your heat needs. You can drop this down dramatically, and make it more practical and affordable.

[mschulz]

Thanks, appreciate the input and clarifications. Will provide an update when the project is done.

I am glad to hear that you have not purchased anything yet. I really think you should read some of the stickies here http://www.solarpaneltalk.com/forumd...ectric-systems as it will help you understand what everyone is talking about. It really helped me a lot and saved me a lot of money. Getting your designed wrong the first time is expensive as most of the things you are going to buy will not play nice in and upgrade and you will have to buy all new stuff. 35KW is a "**** Ton" of power to try and take off the grid. Amy@altE last post about trying to take some of your loads to gas/propane, etc. is the very first step and think of this way. With this system, running a generator, you are going to need to have diesel, propane or gasoline delivered to your home. Why not put in a big propane tank, use it to run a generator, stove, clothes dryer, and refrigerator with it. Put a solar hot water heater on the roof. All these things will help get your usage down to a manageable amount to use solar.

Secondly, I recommend talking to your neighbors that have been doing this for a while. I am sure at least 50% of them have made all the mistakes you are about to and they might be able save you from them.

[Living Large]

Chris Olson is a member here, and has all electric appliances. You may want to look at a thread he posted, on using what he calls "gen support". It is out of the box thinking, which may or may not be attractive for your need/application.

http://www.solarpaneltalk.com/showthread.php?14485-Sizing-Off-Grid-Systems-And-Using-Gen-Support

[russ]

Chris Olson is a member here, and has all electric appliances. You may want to look at a thread he posted, on using what he calls "gen support". It is out of the box thinking, which may or may not be attractive for your need/application.
http://www.solarpaneltalk.com/showth...ng-Gen-Support

He has a very large system due to his northern location - it is designed to get a reasonable amount of generation in the winter - it is over sized most of the year so that works great for him.

[Cult of Dionysus]

Would it be possible to use propane instead of electric for the stove, dryer, and oven? Even better, a clothes line instead of a dryer? As I'm sure you know, anything that makes heat or cold use the most amount of power. The fact that you are using most of the power during the day doesn't help with an off grid system, you still have to put all of the power into the battery bank before you can use it, so you'll be beating up your batteries during the day.

One of the many things I did not know. Thought that you could draw straight from the inverter while the panels were producing power, with a little help from the batteries to stabilize things.

Secondly, I recommend talking to your neighbors that have been doing this for a while. I am sure at least 50% of them have made all the mistakes you are about to and they might be able save you from them.

We are the first to build in this location... So we are very much on our own.

With this system, running a generator, you are going to need to have diesel, propane or gasoline delivered to your home. Why not put in a big propane tank, use it to run a generator, stove, clothes dryer, and refrigerator with it. Put a solar hot water heater on the roof. All these things will help get your usage down to a manageable amount to use solar.

Will go back to the drawing board with the all-electric appliances. We bought them during the Black Friday sales period, but think we can still return them, or otherwise, sell them to someone else (they are still boxed up). Sounds like we'll save a heck of a lot more, even if we'd sell them at a loss.

Again, appreciate everyone's feedback.

[Mike90250]

Forget the Generac brand. They do not cover off-grid warranty. Look for a 1800 RPM genset, liquid cooled, with a 4 pole alternator. Someone on the islands sells/configures them, your system, as planned, will be using the genset quite a lot of the time for your loads, and you may want to clue the genset dealer that you will have many start/stop cycles, which is hard on diesels.
Don't oversize the genset, or it can be prone to wet stacking.
(edit 800, 900 or 1200 RPM even better for low noise & long life
see http://www.smokstak.com/forum/showthread.php?t=31028 post #3 for more info )

It appears your plan trades propane gas appliances for much less efficient usage of diesel and solar to power them. Is this because there is no propane service in your area? That would be the only valid reason, because you will be both buyig a lot of diesel, and replacing the batteries because of severe service.

I practice a bit of load shifting myself, only running the water pump, when there is ample sun to charge the batteries at the same time. But you still need to monitor the cloud cover while running heavy loads, or you will be on diesel power and low batteries. I don't think you grasp the lifestyle shift you will HAVE to make going off-grid AND all electric.

[Amy@altE]

With advances in technology, it is possible to get a really good efficient electric fridge these days. Be sure to check the EnergyStar rating. There are plenty rated for about 1kwh a day usage, which is manageable, about 1 solar panel and 100ah of your 48V battery bank. That's just about 25% higher than the SunFrost DC fridges that are designed for solar systems, so not so bad. Go to EnergyStar's site and check out the fridge you got, it may not be too bad. http://www.energystar.gov/productfinder/

I just saw your previous posts from the summer asking about daytime loads. Running loads during the day does give you a little advantage, but not enough to make the difference you were thinking about.

[SunEagle]

Forget the Generac brand. They do not cover off-grid warranty. Look for a 1800 RPM genset, liquid cooled, with a 4 pole alternator. Someone on the islands sells/configures them, your system, as planned, will be using the genset quite a lot of the time for your loads, and you may want to clue the genset dealer that you will have many start/stop cycles, which is hard on diesels.
Don't oversize the genset, or it can be prone to wet stacking.
(edit 800, 900 or 1200 RPM even better for low noise & long life
see http://www.smokstak.com/forum/showthread.php?t=31028 post #3 for more info )

It appears your plan trades propane gas appliances for much less efficient usage of diesel and solar to power them. Is this because there is no propane service in your area? That would be the only valid reason, because you will be both buyig a lot of diesel, and replacing the batteries because of severe service.

I practice a bit of load shifting myself, only running the water pump, when there is ample sun to charge the batteries at the same time. But you still need to monitor the cloud cover while running heavy loads, or you will be on diesel power and low batteries. I don't think you grasp the lifestyle shift you will HAVE to make going off-grid AND all electric.

I remember reading about a post back in January about an Earl Bakken building an Off Grid Estate called Bakken Hale in the Kona District of Hawaii. He was going to install a 1MWh Aguion battery bank to support his 176kw solar panel system which would help him reduce the amount of time to run his propane generators.

Of course this guy is a multimillionaire but he is off grid and in Hawaii so maybe the OP can afford to install a smaller system.

[Living Large]

With advances in technology, it is possible to get a really good efficient electric fridge these days. Be sure to check the EnergyStar rating. There are plenty rated for about 1kwh a day usage, which is manageable, about 1 solar panel and 100ah of your 48V battery bank. That's just about 25% higher than the SunFrost DC fridges that are designed for solar systems, so not so bad. Go to EnergyStar's site and check out the fridge you got, it may not be too bad.

This is my plan. My largest loads are the water pump and the fridge. There is a propane fridge currently in the off grid cabin I would convert to solar, and I am planning to replace it with an electric simply to live in the lifestyle to which I am accustomed. I like to cook and heat with gas, so it was a natural fit to plan for propane AND not increase the size of the solar system. There are trade-offs to all these decisions, and the degree to which one wants thrift, comfort, etc helps determine what choices are made.

[Mike90250]

... He was going to install a 1MWh Aguion battery bank to support his 176kw solar panel system which would help him reduce the amount of time to run his propane generators. ..

Well, maybe a 1MWh Aquion will have some pretty low Internal Resistance, and would be useable !

[Cult of Dionysus]

With advances in technology, it is possible to get a really good efficient electric fridge these days. Be sure to check the EnergyStar rating. There are plenty rated for about 1kwh a day usage, which is manageable, about 1 solar panel and 100ah of your 48V battery bank. That's just about 25% higher than the SunFrost DC fridges that are designed for solar systems, so not so bad. Go to EnergyStar's site and check out the fridge you got, it may not be too bad. http://www.energystar.gov/productfinder/

I just saw your previous posts from the summer asking about daytime loads. Running loads during the day does give you a little advantage, but not enough to make the difference you were thinking about.

Yup, that was a bit of a curveball thrown my way, but I shouldn't have taken one posters input as gospel. Have been able to cancel/return my appliances. So now need to research propane appliances. The water heater is already solar...

What will end up now drawing the most power will be the tv and the 3hp Grundfos pump, but with a soft starter, that shouldn't be a huge issue.

Thanks also to the poster who mentioned the low rpm generators.

[Living Large]

Yup, that was a bit of a curveball thrown my way, but I shouldn't have taken one posters input as gospel. Have been able to cancel/return my appliances. So now need to research propane appliances. The water heater is already solar...

What will end up now drawing the most power will be the tv and the 3hp Grundfos pump, but with a soft starter, that shouldn't be a huge issue.

Thanks also to the poster who mentioned the low rpm generators.

Do you have an old tube type tv? I just liquidated my Sony Trinitron, on the small side at 27"/110 pounds. It used 120W or something like that. My LED replacement uses 30W, I believe. I think plasma use more power.

As pertains to generators, you will find various opinions. What I found was liquid cooled are better for long term operation (hours) than air cooled. But, they don't come small enough for my application (I am planning to use the smaller Generac, 6000W). Diesel, gasoline, propane. For me, I am in a northern climate so propane or gasoline looks good. I don't want to store gasoline, and I'll have propane anyway. Then what about noise level. Lower RPM = quieter, generally speaking. Sizing the generator properly - at what load is it most efficient? 230V/115V or 115V? These are all things to think about, depending on your situation. FYI - I found researching generators pretty tedious.

[SunEagle]

Do you have an old tube type tv? I just liquidated my Sony Trinitron, on the small side at 27"/110 pounds. It used 120W or something like that. My LED replacement uses 30W, I believe. I think plasma use more power.

As pertains to generators, you will find various opinions. What I found was liquid cooled are better for long term operation (hours) than air cooled. But, they don't come small enough for my application (I am planning to use the smaller Generac, 6000W). Diesel, gasoline, propane. For me, I am in a northern climate so propane or gasoline looks good. I don't want to store gasoline, and I'll have propane anyway. Then what about noise level. Lower RPM = quieter, generally speaking. Sizing the generator properly - at what load is it most efficient? 230V/115V or 115V? These are all things to think about, depending on your situation. FYI - I found researching generators pretty tedious.

If sound is a problem there are a number of companies that make "sound reduction cabinets" for generators. It may be cheaper to go with something like that then a low noise generator.

[mschulz]

Yup, that was a bit of a curveball thrown my way, but I shouldn't have taken one posters input as gospel. Have been able to cancel/return my appliances. So now need to research propane appliances. The water heater is already solar...

What will end up now drawing the most power will be the tv and the 3hp Grundfos pump, but with a soft starter, that shouldn't be a huge issue.

Thanks also to the poster who mentioned the low rpm generators.

This is great news, you are are going to thank yourself in the long run. Next thing you really need to do, is try to get a good estimate of how many watts you are going to use each day. I know this may be hard with out having your loads in use at the time, but estimate as best you can, then everyone here can help you design the correct sized system for your needs.

With this off grid lifestyle, every time you buy something that runs on electricity, you need to count the watts, like someone on a diet counts their calories.

[Cult of Dionysus]

As it stands right now your batteries are sized to only support 9.2 Kwh per day, and your panels are sized to support 26 Kwh per day. Do you see any problem with that statement? It means you get to replace them in less than a year. You are going to fry your batteries with 160 amps of charge current. That is I assume you know a 8400 watt panel system requires two very expensive 80 amp MPPT charge controllers.

If I get a pair of 80 amp charge controllers, coupled with an appropriate inverter(s) with gen-support, and if I avoided depleting the batteries by keeping the DoD around 25%, would that protect the batteries and give me 5-7 years of use? Or would the charge controllers not prevent the batteries frying?

If sound is a problem there are a number of companies that make "sound reduction cabinets" for generators. It may be cheaper to go with something like that then a low noise generator.

Yeah, and I can even put the generator with the cabinet semi-underground (with ample drainage on those rare occasions when it rains) and surround the whole area with a low rock-wall, cover that up somehow, and have the access point facing away from the house.

As pertains to generators, you will find various opinions. What I found was liquid cooled are better for long term operation (hours) than air cooled. But, they don't come small enough for my application (I am planning to use the smaller Generac, 6000W). Diesel, gasoline, propane. For me, I am in a northern climate so propane or gasoline looks good. I don't want to store gasoline, and I'll have propane anyway. Then what about noise level. Lower RPM = quieter, generally speaking. Sizing the generator properly - at what load is it most efficient? 230V/115V or 115V? These are all things to think about, depending on your situation. FYI - I found researching generators pretty tedious.

Honestly, it's a bit overwhelming. But since I'm moving away from having to produce 100Kwh a day, perhaps a pair of Honda EU3000iS would provide the support I need. Not only would I have redundancy, but when the system only needs a little gen support, I'd only run one relatively quiet, efficient unit.