Off-Grid Solar Project - 2KW+ - Request for Feedback

18 Posts
Jan 10, 2008 09:38 pm
Off-Grid Solar Project - 2KW+ - Request for Feedback

Off-Grid Solar Project

Harbor Freight – Part# 90599
Maximum current, 3000 mA.
15 watts max per panel.
Peak voltage: 23.57 volts open current.
Panel dimensions: 12.40'' x 36.42'' x 0.75''; Weight: 9.7 lbs.
Kit includes a
•   regulator with battery connections for charging and maintaining a battery(1+)
•   regulator has 3, 6, 9, 12 VDC outputs

I am building an Off-Grid remote site.  After considering the cost of commercial utilities for power, water, I decided the same, and even lesser cost, of going off-grid would be a wiser investment (and GREENER ).  I need to design and build from the top down, as it were.

I am finding the average cost for the panels them selves seem to be in the range of $6+/watt.  I also found that the panels had a lifespan (? ? ?) of maybe 20 years (is that correct???)

Then I stumbled on this 45watt kit from Harbor Freight –
Retail sale price is $250.  It occasionally goes on sale for under $200.  I am considering negotiating with them to get a bulk discount – maybe go straight to the manufacturer.  I just want the panels. . .  If I can get them for say $50/each or $150/kit (or LESS…), then a ‘24VDC’ array, with about 2200Watts would equal 100 12volt kits???. . . (about $3-$4/Watt. . .)

I figure the panels can be connected in series/parallel to produce whatever array configuration I desire.  I am reasoning that the higher the voltage (48-56 VDC vs. 12-14VDC) will be more efficient to ‘Invert’ to 110/220VAC.  Any specific advice would be greatly appreciated on this initial theory . . . .

My power needs would be:
•   Computer/network power – 7X24
•   Refrigeration – a residential refer and chest deepfreeze – (on demand with high IPP – compressors. . . cant get around it. . .)
•   LP gas water heater – electronic ignition (pilot less)
•   High efficiency front-load washer/LP gas dryer – electronic ignition (pilot less)
•   Lighting – Florescent, LED.
•   LP gas range - electronic ignition (pilot less)
•   Microwave oven
•   Cistern Water storage – electric paddle to circulate water in a 1500 gallon storage tank (something about keeping it from stagnating)
•   Air compressor – for shop tools

I would also have a 5500Watt gas/diesel GenSet.  Wood/coal/pellet/junk mail stove for primary heat.

So what I need to confirm is:
•   Wire size – AWG to run to the panels – 8AWG?. . . 6AWG? To run from the PV array back to the Charge Controller – 100’ for discussion.
•   Wire type – Copper? Aluminum?  Each has a calculable voltage drop/loss back to the Charge Controller (MPPT) – overhead/ buriable NEC spec.
•   Charge Controller – MPPT vs. PWM – MPPT makes more sense – they seem to be available in specific input/output configurations. . . (12, 24, 48VDC)
•   Battery configuration – that I think I have – 12, 24, 48 – each manufacturer has specifications on the float voltage.  I figure I can use Deep Cycle batteries from Wal-Mart (12V 115 ampere hour) – cost around $60/ea.  May be able to negotiate that down for a bulk order. . .
•   Inverter – I am hoping to find something that has a 220VAC output that would match what  commercially connects to the residential main panel – 2 110’s 180* out of phase, with a neutral return.   Would like something which only draws from the DC side when there is an AC demand – doesn’t idle?. . . If 110 is more cost efficient, I can simply bridge the breaker panel.

What am I forgetting. . .?. . .

Any and all comments, suggestions, recommendation are greatly appreciated.

Thank you.
 
163 Posts
Jan 11, 2008 09:29 am
Re: Off-Grid Solar Project - 2KW+ - Request for Feedback

Lots of problems here, so its difficult to decide where to start, but perhaps we can begin by looking at problems associated with using lots of small wattage panels instead of a few large wattage panels.

Each 15 watt panel has a dimension of approximately 3 square feet, therefore 2000 watts of panels will require a minimum of 400 square feet. Do you have that amount of space available on the south-facing side of your roof? If you place them side-by-side on the ground they will stretch for 150 feet or more.

You probably cannot put more that 4 of those panels in a "series" string, so that means you would have about 35 parallel strings going into a controller. That means 35 dc breakers at around $10 each for every string.

You may only get 10 watts or even less from the "cheap" and supposedly 15 watt panel that you purchased, whereas the manufacturer of a UL listed brand name PV panel will stand behind their warranty for 25 years with a guaranteed minimum output.

The system that you have shown will probably act quite nicely in carrying out its intended purpose of trickle charging a 12V battery, but I suspect you will have lots of problems if you try to extrapolate that into a 2kw off-grid power system.
 
578 Posts
Jan 11, 2008 11:07 am
Re: Off-Grid Solar Project - 2KW+ - Request for Feedback

regardless of the where you get them from, i would not use non -ul-ce-csa-tuv listed modules on anything larger than a simple 1 or two module project. 

I would especially not put them on a house.  It is not uncommon to see quality UL listed modules under 4.50 per watt. 
look at the evergreen 170 for example.

you dont want 26+ strings of modules.  the cost of wiring and balance of system equipment will eat up your savings on the bargain no-name modules.

james
Alt-E staff

AltE
"Making Renewable Do-able"
http://www.altEstore.com/

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
 
184 Posts
Jan 11, 2008 11:41 am
Re: Off-Grid Solar Project - 2KW+ - Request for Feedback

It would be helpful if you would better define your power needs.  Consider checking each item with a Kill-A-Watt meter.  Record kwh, and the hours-per-day that each item runs.  Motor starting current is also an important consideration.  Does the cistern motor run continuously?  You're off to a good start, with energy-efficient lights/appliances and alternative heating.   

John 
« Last Edit: Jan 11, 2008 11:43 am by John Dalhaus »
 
18 Posts
Jan 13, 2008 06:04 pm
Re: Off-Grid Solar Project - 2KW+ - Request for Feedback

John B.  Thank you for your honesty.  I humbly admit I don’t know. . .   OK. . . sounds like the "Bargain Panels" may not be the way to go.  I will have plenty of space to mount panels on the Southern roof line.  Is my thought of “the higher the DC voltage to invert, the more efficient” on track?  (48V vs. 24V or 12V).

Thank you.
 
18 Posts
Jan 13, 2008 06:25 pm
Re: Off-Grid Solar Project - 2KW+ - Request for Feedback

Thank you, James.

The evergreen 170 – is that considered a 12V or 24V panel?

170-Watt PV Module  - 
Rated power: 170 watts  - 
Voltage (@ max. power): 25.3 volts  - 
Current (@ max. power): 6.72 Amps  - 
Open circuit voltage: 32.4 volts  - 
Short circuit current: 7.55 Amps  - 
LxWxD (inches): 61.8 x 37.5 x 1.6 (5’ X 3’)  - 
Weight: 40.1 lbs.  - 

If it’s a 24V/170W panel, it would be $765/ea (@ $4.50/Watt) – that would be about 14 panels – For a 48V/2200W array = 24 panels. . .  that’s like $11,000 – $22,000 (24V vs. 48V)             
Even though the 48V system may be more efficient to invert to 110, that’s twice the up-front cost in the array. . .  Need to do more research into my constant vs. occasional power needs. . .  Is there some place local to the Seattle, WA area I can go preview PV panels?
 
18 Posts
Jan 13, 2008 07:28 pm
Re: Off-Grid Solar Project - 2KW+ - Request for Feedback

Thank you, John D.

I found this GenSet calculator (one of many) at the following link:
http://www.harborfreightusa.com/guide/select_generator/

I am modeling my initial need from the specs on a 31’ Airstream I have access to.  It has a 110V/30A power system.  It has a 3Way power refer (12VDC/110VAC/LP Gas), a 6Gal electric water heater, a central LP gas forced air heating system, and a roof AC unite.  All this on a 30A main breaker.  I would reason that (winter operation) the refer, the central furnace and the water heater might come on and run at the same time.  By the same token, the AC unite would replace the Heater in summertime.  That’s where I came up with the 2500Watt calculation.  Just a modle now. . .
I work at home on the internet.  So I am calculating:
Constant:
•   Internet access router = 25-30 Watts
•   Laptop (typical) = 50 Watts

Occasional/mandatory: (24hr available)
•   Refrigerator = 700/2200 (run/start)
•   Deep Freeze = 700/2200 (run/start)
(I think these are a little high. . .)

Occasional:
•   Microwave = 600 Watt
•   Washing machine (front load) =
•   Dryer (gas) = 700/1800 (run/start)
•   Cistern pump = 800/1300 (run/start)

Misc. lights – florescent – 15W/ea (60W-light)

Its going to be tight – I’m trying to size for worst case – 6 hours/day charging and operation, to cover the 18hrs with no sun. . .  going to require a substantial battery bank. . .  The question is. . . can I recharge it in 6 hrs. . .

The cistern (water tower) anti-stagnate paddle was going to be a stand alone thing – 1500 gal tank on a 20’ water tower with a tiny, gear reduced 12V motor to slowly turn the paddle – 5-10RPM – I don’t think it has to run constantly so I was going to simply mount a set of panels on top of the tank – just run when the sun’s up. . .  The pump runs when the rain barrel float says “full”, then it pumps 50Gal up into the tower and shuts off.  Almost sounds like I need closer to 3Kw. . .

How’m I doin?. . .
 
163 Posts
Jan 14, 2008 09:14 am
Re: Off-Grid Solar Project - 2KW+ - Request for Feedback

If it’s a 24V/170W panel, it would be $765/ea (@ $4.50/Watt) – that would be about 14 panels – For a 48V/2200W array = 24 panels. . .  that’s like $11,000 – $22,000 (24V vs. 48V)             
Even though the 48V system may be more efficient to invert to 110, that’s twice the up-front cost in the array. . . 

Jack,

Power (measured in watts) = Voltage x Amperage, so two 170W panels (24V/7A) will give you 340 watts whether they are connect in parallel producing 14A at 24V or in series producing 7A at 48V. However, there is a lot more to putting a system together than just selecting the panels. You will need to read some more on the basics of electricity and PV system design. This is probably a good place to start.
http://howto.altenergystore.com/

 
578 Posts
Jan 14, 2008 10:16 am
Re: Off-Grid Solar Project - 2KW+ - Request for Feedback

the evergreen 170 is an 18v nominal module.

its electrical characteristics, as a result of the nubmer of cells, are in between a 12 and 24 volt module.  look at one of each to compare.  we say what type it is on every spec page.

this type of module requires an mppt controller if you plan on having a battery bank.

keep using the forum and the how to section,
here is a book if you want to learn more in one place

http://store.altenergystore.com/Books-Workshops-Videos/Solar-Electric-and-Passive-Solar/Photovoltaics-Design-Install-Manual/p481/

come out for a workshop if you are close!

cheers,

james
Alt-E staff

AltE
"Making Renewable Do-able"
http://www.altEstore.com/

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
 
18 Posts
Jan 16, 2008 01:05 am
Off-Grid Solar Project - 2KW+ - Request for Feedback

James -
What do you think of the SunWize SW150 or SW160 24V Solar Panel?
Model Rated  Rated   Rated   Open    Short
      Power  Voltage Current Circuit Circuit 
     (Watts) (Vmp)   (Imp)   (Voc)   (Isc)   
SW150 150    33.4    4.50    42.0    5.11   
SW160 160    33.4    4.79    42.0    5.43   

MPPT Charge Controllers:
Are these charge controllers adjustable by default?  Let me give you a little more of my background. . .
I worked in telecommunication back in the 70's and 80's.  I worked "inside plant" - Central Office.  The phone systems work on DC, -48V.  They are all on batteries.  For example:
The rural locations I worked in employed a string of single-celled, 1100Ah batteries - 24-25 in a string.  Typically we used Lorain Flotrol rectifier/chargers.  A redundant pair, 100 Amp, that load share (hard wire sensing).  These rectifiers are totally adjustable to whatever the battery string needs to "Float".
A typical single cell is 2.2-2.3Vdc – so 24 wired in series = 52.8-55.2Vdc float voltage.
So when I’m talking 24V, I really mean 28.4 – 29.0 Vdc float.
I’m having a little trouble finding this granular of information on the MPPT controllers.  Do you know which ones are adjustable to this level of accuracy, and to achieve that output, what panel voltage do they need to be coupled with?
 
578 Posts
Jan 17, 2008 11:24 am
Re: Off-Grid Solar Project - 2KW+ - Request for Feedback

generally all of the mppt controllers can do this.  they will auto sense the battery bank, and have appropriate defaults programmed in.  mx 60, blue sky, apollo, and xantrex xw mppt 60, will all have appropriate setpoints out of the box.

as far as the modules, i would say they are okay, but not a first choice.  I am not sure if those are ul listed or not.  my favourite 24v nominal modules are the solarworld 165/175 mono, the sharp 175/180/185 mono, and the sharp 170 (poly).  If the sunwize modules are UL listed, then they will be fine for a home application, grid tie or off grid.  generally i shy away from recommending non UL listed modules for applications for homes.

I will check on the UL status of the sunwize modules for you.

james
Alt-E staff

AltE
"Making Renewable Do-able"
http://www.altEstore.com/

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
 
578 Posts
Jan 17, 2008 01:05 pm
Re: Off-Grid Solar Project - 2KW+ - Request for Feedback

sunwize 150 and 155 are UL listed, 160 are not.

james
Alt-E staff

AltE
"Making Renewable Do-able"
http://www.altEstore.com/

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
 
18 Posts
Jan 17, 2008 05:31 pm
Re: Off-Grid Solar Project - 2KW+ - Request for Feedback

Thank you, James.
I will research the Panels you suggested and get back to you.  Due to the limited Sun sightings here in the NW I'm figuring on over-engineering my system by 100%.  If I build a 2500Watt system I figure I'll average 50% (1250Watts).  I will be implementing as many conservative energy applications as possible - DC appliances & lights, 14VDC outlets alongside the 110VAC, Carosine lanterns from Aladdin Lamps, etc.
I'll be in touch. . .
 
578 Posts
Jan 17, 2008 05:52 pm
Re: Off-Grid Solar Project - 2KW+ - Request for Feedback

50% derating on an off grid system is about right, anything more is just being more conservative and wont hurt.  I would suggest not to bother with dc circuits wired through the house.  maybe one or two appliances (fridge) hardwired, and maybe emergency lights, but dual wiring the house is totally not worth the effort and the money spent on conductors for the voltage drop of dc wiring wastes the measly 8% efficiency saved by not using the inverter.  i would go all ac with the possible excetption of a sunfrost fridge, but even those come in ac.  that is what i would do if i had a clean slate off grid project.  my two cents . . .

james
Alt-E staff

AltE
"Making Renewable Do-able"
http://www.altEstore.com/

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
 
9 Posts
Jan 17, 2008 09:46 pm
Re: Off-Grid Solar Project - 2KW+ - Request for Feedback

I was also going to run a 24voltDC and 120AC both and like James said did not seem worth the wire cost and effort.

I than sat in each room of my current home to determine what was truly AC and what was DC.   TV, radios, network switch, computers and all other electronics devices are DC.   I took some of these apart and found converting most of them to DC was a simple task.
Now I am running DC most places and the AC only the few places it was needed.

Some items were interesting for example a LinkSys network switch.   Wall transformer says 7.5volts DC at 1.5 amps.  The power circuit was rated for 3volts to 30volts DC.  At 14volts DC it draws .015amps.
 
18 Posts
Jan 21, 2008 05:21 pm
Re: Off-Grid Solar Project - 2KW+ - Request for Feedback

Thank you, David and James. . .
I did the same thing, evaluating what I could either convert, or was already compatible with DC.  For instance, using DC adaptation instead of AC transformers - using a car adapter for the cell phone, making a DC adapter for the network router and HUB, same thing for the laptop. 
When I wire in an AC socket in the kitchen counter area, I’ll use a 4-plex with a switch and single duplex socket – for the microwave or coffee maker – and switch it off when not in use – don’t need the ‘clock’ – try to eliminate as many ‘ghost’ drains as possible.
I think if I wire at least 1 DC tri-plex in each room that will be sufficient.  This is primarily in a 50X10 loft space in my shop – a 1-BdRm efficiency to live in while I’m building the house.  If I REALLY get to missing my electric conveniences I can get just about any kind of appliance from JC Whitney or a truck stop – lots of 12V toys. . .

I need to do more research on power distribution for this –
Does each panel require a separate breaker. . .
How does all this combine into the inverter and charger – I know how it does electrically, but I’m not sure where to put breakers – ins and outs. . .

More later. . .
 
578 Posts
Jan 21, 2008 05:43 pm
Re: Off-Grid Solar Project - 2KW+ - Request for Feedback

great, glad you are making progress for a solution for your needs.

regarding DC load center/disconnects/distribution panel,

this is probably the best chocie for a system of your size.

http://store.altenergystore.com/Enclosures-Electrical-and-Safety/Electrical-Enclosures/DisconnectLoad-Enclosures/Dc/Outback-FlexWare-FW500-DC-breaker-enclosure/p5576/

this will give you room for 2 inverter breakers and I think 8 loads, or 1 charge controller and 6 loads. 

we have the old version, the PS2DC in our office.  very roomy and comes with good schematic.

james
Alt-E staff

AltE
"Making Renewable Do-able"
http://www.altEstore.com/

Tel: 877.878.4060 x107  or +1.978.562.5858 x107
Fax: 877.242.6718  or +1.978.562.5854
 

Disclaimer and Disclosure

The Alternative Energy Store, Inc reserves the right, within its sole discretion, to refuse or delete any posting or portion thereof, or terminate or block the access to this forum.

The opinions and statements posted on this forum are the opinions and statements of the person posting same, and do not constitute the opinion or act of the Alternative Energy Store, Inc (AltE). The Alternative Energy Store, Inc does not endorse or subscribe to any particular posting. No posting shall be construed as the act or opinion of the Alternative Energy Store, Inc.

Click here for BBB Business Review

McAfee SECURE sites help keep you safe from identity theft, credit card fraud, spyware, spam, viruses and online scams
Desktop Website | Mobile Website

Share

Click on an icon to share! If you don't see the method you want, hover over the orange "+".

Feedback

What can we do to help you?

Please enter a summary
Sorry, the copyright must be in the template.
Please notify this forum's administrator that this site is using an ILLEGAL copy of SMF!
Copyright removed!!