New to Solar. Want to Build As I Go . For Off Grid Eventually. Where Start?

CindyR

1) I live in a Condo but am moving into house in 5 months.
2) Will be buying land (out of city) after that to put Cabin Off Grid.
3) On a budget
4) May use system in house (in city) if power outage but not installed on roof -like a solar generator in emergencies
5) Want to build up panels as I go
6) so need inverters and equipment to be rated for more than when I start with one or two panels and batteries- if that is feasable
7) "Grow as I go"
8) Goal is 3kW-5kW system
9) Need to know what best panels to purchase now
10) Only buying 2 to start with
11) And the equipment to run it like an emergency generator till Off Grid is ready in country
12) Help!!

BB.

Re: New to Solar. Want to Build As I Go . For Off Grid Eventually. Where Start?

Welcome to the forum Cindy!

What you are asking is difficult to do with solar power... Growing a system over time is like buying a Honda Civic and growing in to a mini-van and eventually a pickup to a semi... There are pieces that can be migrated between systems--But it is, many times, hardly worth the trouble.

And off grid solar power is not cheap... On a per kWH basis, it easily costs 10x $$$ per kWH vs utility power (if you have utility power on/next to property).

The only way off grid solar makes economic sense is if the system will cost less than stringing wire from the utility easement to your point of use.

Grid Tied solar power (panels+GT Inverter, no batteries, no emergency power usage) can be competitive or even cheaper than utility power in some cases (my power in California is Time of use/Tiered pricing... My summer afternoon power can range from $0.30 to $0.50 per kWH where my solar GT power costs around ~$0.17 per kWH).

Before you purchase any equipment--We should really go through a couple paper design cycles. It is very easy to purchase equipment deals that end up not working well together. Spending a few days understanding that loads (power requirements) and paper designing your system will save you a lot of frustration (and probably money) in the future.

To give you some idea of scale... A relatively efficient home may use 300 kWH per month (10 kWH per day) if using natural gas for heating/cooking/hot water. If you have A/C, you are probably looking at 1,000 to 3,000 kWH per month (33 to 100 kWH per day).

In the "off grid world" (assuming very efficient/minimum use of power) and not a lot of money to throw at a system + generator + fuel--You would be looking at:

• 1 kWH per day (30 kWH per month) = Cabin. Lights, laptop computer, radio, small water pump, cell charger, etc.
• 3.3 kWH per day (100 kWH per month) = Very energy Efficient Home. About the minimum sized system that can support a refrigerator, well pump, washing machine, laptop computer, TV, etc. in a near-normal electric power existence.
• 10 kWH per day (300 kWH per month) = Normal city home with natural gas (or propane). May be able to run a bit of A/C, heat pump hot water, extra freezer, etc...
• 33 kWH per day (1,000 kWH per month) = Add A/C, heat pump for cooling/heating. Possibly some electric stove/Oven use. "Average North American" home electrical usage.

I know nothing about your power usage--The above is just to "frame" the discussion. Note that each system is about 3x larger than the one below. And each step would require pretty much brand new equipment to support the next higher power level (solar panels may be able to migrate--But that can be a bit of a wild card--And solar panels are cheaper then they ever have been before--not the major cost of an off grid power system anymore).

So--Just for a paper discussion, figure around $1 to $2 per kWH (assuming 20 year system life, replace batteries every X years, and replace electronics/inverters/charge controllers every 10+ years).

That $200 per month electric power bill for the average American Home would look like $2,000 per month (over 1/2 of the 20 year costs paid up front just to turn the power on).

In general, when going "off grid" for power, extreme conservation is almost always a better investment of time and money vs just building a larger power system.

Some things, like running grain driers and seasonal water pumping (commercial agucultural) almost never make sense to run from solar--Many farmers use diesel genset for this sort of work.

Which leads us to another suggestion--If you are looking for emergency backup power, a genset plus some stored fuel (always an issue) for 1-2 weeks of emergency power is usually a more cost effective solution vs a true off grid solar power system.

Again, this is some very big rough guesses about a generic off grid power system. Most people overestimate the amount of power a solar power system can provide and underestimate their own power usage/needs.

Power usage is a highly personal set of choices. And we want to help you make informed choices here.

Usually the first thing we suggest is to get a Kill-a-Watt type power meter--You can plug your appliances into the meter (1 to a few days at a time) and measure the average power usage (watts) and amount of power used (kWatt*Hours). Also, look at your power bill over the last few months (or year, if you have that information) and see how much you use today.

With that information, and a rough idea of where the solar power system will be located (how much sun does the region receive), we can help you with planning/costing out a solar power system.

-Bill

Thomas

Re: New to Solar. Want to Build As I Go . For Off Grid Eventually. Where Start?

BB hit it good with the automobile analogy....
Buy your stages one size up to facilitate changes that are inevitably very dynamic by scale with solar.
I know this, I have not been able to afford a lot and have had to double replace inexpensive stage components.
Good luck to you
back to my software problem...

CindyR

Re: New to Solar. Want to Build As I Go . For Off Grid Eventually. Where Start?

Wow! I see what you are saying. Thank you so much.

The house we are moving into is a rental for a year till the Off the Grid Home is finished. Our OTG house is low cost with my family doing most of the work so adding the solar was not based on comparative electric cost because we will live this way permanently. (I do like redundancy though) However we are on a budget for getting us to that point. I do want to run our power tools during building the parts of the house that we will do ---with solar.

I just started watching a series by mjlorton on youtube...it looks pretty detailed ...took a ton of notes but still have questions here and there.

Is it okay to run those questions by you from time to time? I am just getting used to this forum stuff and will send pics of my notes and ideas.

BB.

Re: New to Solar. Want to Build As I Go . For Off Grid Eventually. Where Start?

By all means, feel free to ask questions as they come up... You can post them to this thread, and we can follow your path towards whatever your solution(s) end up being.

Power during building... Depends on how much power you need, and if you will be living on-site or not (RV, temporary trailer, etc.).

In general, if you are not using a lot of power (mostly battery powered tools, a few skill saws, gasoline powered mixer, etc.), then you might get away with a 1kWH or 3.3 kWH system to run the smaller loads and even keep a refrigerator on-site.

If your loads are larger (compressor, table saws, etc.)--Plan on using a genset big enough to run those loads (5kW???).

And if you are doomed to running a genset during construction and don't need small amounts of power (i.e., overnight for living on site)--Forget the solar for now. Get a 3.5-5kW genset to run the larger loads, and get a smaller Honda eu2000i to recharge batteries, run smaller tools and lights.

A 5 kW genset may use around 1/2 to 1 gallon per hour of gasoline. A small/quiet Honda eu2000i (1,600 watt max, or 1.6kW) will run around 1/10 to 1/4 gallon per hour--Much more acceptable to provide 10 hours of "continuous power" when working. And fire up the big "noise maker" when running the table saw, planner, etc.

-Bill

CindyR

Re: New to Solar. Want to Build As I Go . For Off Grid Eventually. Where Start?

Thank you too....his automobile analogy made it very clear...lol

I will buy one size up to facilitate changes...if you know of anyone with videos or websites please let me know..I am a very visual learner.

I suppose if I have a smaller array that will not be compatible then I could probably wire it for just the garage of workshop...etc.?

BB.

Re: New to Solar. Want to Build As I Go . For Off Grid Eventually. Where Start?

I should also add.. Some folks have built a smallish off grid power system for the year of construction. And move that to power a small guest cabin/RV connection later (or sell the system to somebody else).

-Bill

NorthGuy

Re: New to Solar. Want to Build As I Go . For Off Grid Eventually. Where Start?

I built my off-grid system little by little, but in a different way.

I first bought a stand-by backup generator. I had to do lot of re-wiring/trenching to do that.

Then I installed inverter and batteries. This gave me a huge UPS for the whole house and I've never had power outages since.

I planned to install panels a year later, but then I decided that there's no reason for me to pay to electric company for another year and installed panels right away.

It is hard to grow battery bank (unless you change all batteries when switching to larger bank), so you need it close to final size. It is impossible to grow inverter. It is easy to grow solar array. However, by the time you have full battery bank, inverter, charge controller and some panels, it'll be easier/cheaper to buy more panels and go off-grid rather than continue paying electric bill.

BB.

Re: New to Solar. Want to Build As I Go . For Off Grid Eventually. Where Start?

Cindy,

Focus on your loads first... Trying to plan on powering a section of the home is difficult to plan/design for.

I had a friend with a full machine shop in his garage (CNC Lathe, Mill, 3 manual lathes, manual mill, and various grinders/cutoff saws. Plus his wife's washer/drier).

My garage, a few lights, garage door opener, and washer+drier.

Which garage/shop to design a system for.

I understand wanting to look a a system and see how they are put together. But I would again suggest a Kill-a-Watt meter, looking at your power bill, and then pencil a system design.

We could look at 300 watt AC inverters or 6kWatt hybrid inverter-chargers with generator support. It is interesting (at least to me)--But will probably confuse you.

I like to get the paper system sizing first--Then you can look at equipment appropriate to your needs. After you have gone through the various steps, the second time will be much easier. :roll:

Take a look at 2manytoy's website... He started small and got to a mid-sized system that provides backup power to his home. Lots of DYI sections to his system.

http://2manytoyz.com/ (about 1/2 way down the page)

-Bill

Thomas

Re: New to Solar. Want to Build As I Go . For Off Grid Eventually. Where Start?

I think the tightest solar modules available are 12w @ 12v[1A] I do not think it gets any better that that ratio for future figuring...

northerner

Re: New to Solar. Want to Build As I Go . For Off Grid Eventually. Where Start?

I built my system as I went along and relied on grid power till I had enough solar power and storage to go off grid. One of the biggest issues for me was deciding on the battery/inverter voltage to go with. I had decided on a 24 volt system, but realized afterwards that with the size of my system, perhaps should have gone with a 48 volt system. The downside of adding to battery capacity as you go, is that you wind up with more parallel paths with each battery bank you add, which is not good. The other thing to consider is that with a 48 volt system, any expansion means putting in 2 x the number of batteries, than with a 24 volt system. But if your looking at a 3 to 5 kw system, I would recommend going with a 48 volt system.

As others mention, it's best to figure out what your destination loads will be, and they you have something to work towards. What you could do is put in a good size inverter and 1/2 the battery bank that you will eventually need. You would then have a year or so to add the second battery bank. I would also recommend a good quality mppt charge controller. This way you will be able to put in place arrays of three 24 volt solar panels. You could add panels, and if necessary charge controllers as you go. A small genset will do for now such as a Honda eu2000.

With my system, I was able to run any power tools with a 870 ah battery bank at 24 volts. I have just recently upgraded my bank to 1305 ah, which gives me a much better comfort margin. I am just in the process of doubling my solar array (in preparation for winter) from 1.4 kw to 2.8 kw. My usage in summer has averaged 3.5 kwh per day, but could be close to double that in winter. I have had only about 20 hours of generator run time with my small eu2000 in summer, but expect significantly more run time this winter, even with the larger solar array.

CindyR

Re: New to Solar. Want to Build As I Go . For Off Grid Eventually. Where Start?

What do you think about enphase micro inverters? Correct me if I am wrong, but don't they convert from DC to AC at/on each panel and wouldn't that be a good thing? If one panel looses due to some problem won't this type be more efficient?

Are these only for systems that are tied to the Grid?

How does that work with the battery bank? (the DC part ...if it is already AC...a little confused about this)

BB.

Re: New to Solar. Want to Build As I Go . For Off Grid Eventually. Where Start?

The short answer is that Enphase Micro inverters are pretty much identical functionally to the large string/central GT inverters.

There are discussions about which is better (micro inverters or central inverters) is probably not useful here.

In general, GT inverters are for use with grid/utility power systems.

It is possible to connect a GT inverter (micro or central) to an Off Grid sine wave inverter and create a micro-grid. The off grid inverter sets the frequency and voltage for the grid (such as 120/240 VAC 60 Hz).

If there is enough sunlight, the GT inverter will help share powering the loads, and if there is "excess power" from the GT inverter, it can actually drive power "backwards" through the OG inverter and charge the battery bank (there are some more details about how to control charging the battery bank--beyond what I need to discuss in this post).

In general, there is usually no good reason to use GT inverters on an off grid system. It may make sense if you have a long distance from the solar array to the battery bank+charge controller, or if there is a distributed charging setup (multiple solar arrays, micro grid going to multiple houses/buildings).

-Bill

ggunn

Re: New to Solar. Want to Build As I Go . For Off Grid Eventually. Where Start?

CindyR wrote: »

What do you think about enphase micro inverters? Correct me if I am wrong, but don't they convert from DC to AC at/on each panel and wouldn't that be a good thing? If one panel looses due to some problem won't this type be more efficient?

Are these only for systems that are tied to the Grid?

How does that work with the battery bank? (the DC part ...if it is already AC...a little confused about this)

Microinverters are difficult to impossible to use for off grid systems.