Off Grid Help

So Cal · March 2013

I am a Los Angeles base PV provider, Grid tied only thus far. I have studied off grid systems somewhat.
I have a potential client that wants a bid for an off grid system. Its an odd request that has some illogical aspects. I want to give her a budgetary estimate before I spend alot of time sizing and designing a system and undertaking a course of study to fill in my knowlage gaps enough to properly design and install what she wants.

Over view;The property is metropolitan. There is a house on the property (utility connected), but she doesn't want PV for the house, she wants it for a 250 sq ft container conversion that will be on the property which will be her residence. She wants it be completely grid independant. She already knows she will need a generator as part of the mix, that she will not get a utility rebate and will be spending alot of extra money. But its "been a dream" of hers and she wants to do it.

I got a rough list of her loads from my sales person that met with her;
JBL Creature speakers and sub woofer 25watts, daily
Mac computer, daily
iPhone cell phone charger, daily.
Gigi wax pot, once every month for an hr.
Kitchen aid mixer, once a week
The juicer is this one: daily use
http://www.amazon.com/gp/aw/d/B0002VAFVG/ref=mp_s_a_1?qid=1364435175&sr=8-4&pi=SL75 (this is a 1,000 watt juicer)
Dyson’s AM04 heater/cooler
Lighting is 10 low watt bulbs
Outdoor string lights daily basis. Lamps, maybe three, w one eco bulb each.
Flat iron, once a week
Coffee grinder, daily
Hair dryer, once a week
Water heater (on demand unit)
Maytag fridge 19cuft mod:mbf1956hes
Ser:11919935gt
Electrolux dishwasher mod:fdb1050reco
Ser:th62390562
Gas stove frigidaire 4 burner

I don't know if the above is enough information to give a very rough equipment schedule to base a very rough quote on or if I really have to go onto the next step of getting a better watt hour count first.

Can anyone refer me to a package system, equipment recommendation or a supplier/design support for off grid systems?

I would like to give a ballpark estimate and then see if she's still in the game.

The next step would be to Interview her to get a better idea of daily / weekly use of electrical items, trim down bigger loads with better efficiency, lifestyle choices etc. (like that juicer) where posible.

Any advise, referals, comments, recomendations or cautions will be appreciated.

Cariboocoot · March 2013

Re: Off Grid Help

Welcome to the forum.

You're shooting in the dark with that info. You really, really need a firm Watt hour figure to plan around. And the client must understand that's all there is; any extra power has to come from someplace else.

Personally I wouldn't touch that job with a 40 foot power pole. It will be a lot of money for a little power and is likely to come with a whole slew of legal problems that no one has thought of yet (not grid-connected home in a grid area in California?)

Kits aren't going to do you (or anyone) any good because they are comprised of what the seller makes money off of, not what actually suits the user's needs. Off-grid solar electric power systems are highly site-specific.

I have this terrible sense that this could turn in to one of those disasters I'm always having to re-do on a "postmortem" basis.

Eric L · March 2013

Re: Off Grid Help

Things like the dishwasher and the on-demand water heater (if electric) are a non-starter for anything but a very large system, which would never fit on a container conversion; the battery bank alone would need a sizable outbuilding. If she's serious about it she's got to study what people do that live off grid, and follow their example.

Anyway, as Cariboocoot says, your and her real problems aren't likely to be building the system, which is probably doable if she will give up some items, or even the cost. It's the permitting, insurance, and so on involved with doing this in a California city.

Edit to add: if her interest in off grid includes environmental considerations, then your building her a grid-tied installation would be a lot more beneficial than the off grid (all those batteries to buy and replace have an environmental cost).

BB. · March 2013

Re: Off Grid Help

Welcome to the forum So Cal.

To be helpful to your customer, you want to work on them understanding their loads and how much conservation can help save energy and real out of pocket money.

There are two parts to the energy message--Average power usage (i.e., kWH per day/month/etc.) and peak Volt*Amps (hair dryer, well pump, microwave). Those numbers are best measured (i.e., have the customer use a couple of Kill-a-Watt type meters and/or a whole house monitor--neither costs that much) by the customer simulating the new off grid lifestyle. Noting that some devices (like refrigerators/freezers) may use more energy in hot water/no Air Conditioning homes (during summer).

The peak Volt*Amps (remembering that Power = Volts * Amps * Power Factor) sizes the wiring, AC Inverter, and backup generator. The kWH per day sizes the battery bank (as well as any high power loads). The daily loads and battery bank capacity (very large battery banks increase the need for more charging current from array/backup genset) will define the solar array + backup power source(s).

So Cal wrote: »

I am a Los Angeles base PV provider, Grid tied only thus far. I have studied off grid systems somewhat.
I have a potential client that wants a bid for an off grid system. Its an odd request that has some illogical aspects. I want to give her a budgetary estimate before I spend alot of time sizing and designing a system and undertaking a course of study to fill in my knowlage gaps enough to properly design and install what she wants.

Over view;The property is metropolitan. There is a house on the property (utility connected), but she doesn't want PV for the house, she wants it for a 250 sq ft container conversion that will be on the property which will be her residence. She wants it be completely grid independant. She already knows she will need a generator as part of the mix, that she will not get a utility rebate and will be spending alot of extra money. But its "been a dream" of hers and she wants to do it.

Not a problem--We all have dreams and we try to help people to obtain those dreams without too many surprises.

For you--I would suggest using around $1 to $2 per kWH for the "cost" of off grid power (capital costs, installation, maintenance, battery replacement every 5-7 years or so, new electronics such as inverter+charge controllers every 10+ Years) divide by the estimated consumption. Also note that most people can only reasonably average around 65-75% of the system's PV capability every day--It is not practical to use 100% every day (there are opportunity loads, backup genset usage, etc. that may up the usage percentage--But for planning I would start with those assumptions).

I got a rough list of her loads from my sales person that met with her;

As always, need actual Watt*Hours measurements of her daily average usage. But here is my starting guesstimate.

JBL Creature speakers and sub woofer 25watts, daily * 4 hours per day = 100 WH per day
Mac computer, daily 30 watts * 10 hours per day = 300 WH per day
iPhone cell phone charger, daily. 3 watts * 5 hours = 15 WH per day
Gigi wax pot, once every month for an hr. 300 watts * 1 hour = 300 WH (during sunny weather)
Kitchen aid mixer, once a week 300 Watts * 20 minutes (1/3rd hour) = 100 WH (sunny weather?)
The juicer is this one: daily use http://www.amazon.com/gp/aw/d/B0002VAFVG/ref=mp_s_a_1?qid=1364435175&sr=8-4&pi=SL75 (this is a 1,000 watt juicer) 1,000 watts * 1/10 hour per day = 100 WH per day
Dyson’s AM04 heater/cooler 1,450 watts * 5 hours per day = 7,200 WH per winter day (how much sun?)
Lighting is 10 low watt bulbs 8 bulbs * 10 watts * 10 hours per day = 800 WH per day (more in winter?)
Outdoor string lights daily basis. Lamps, maybe three, w one eco bulb each. 3 * 10 watt bulbs * 4 hours = 120 WH
Flat iron, once a week 1,200 watts * 1 hour = 1,200 WH per week
Coffee grinder, daily 300 watts 8 1/10th hour = 30 WH per day
Hair dryer, once a week 1,800 watts * 1/2 hour per week = 900 WH
Water heater (on demand unit) (need exact unit--Some use no power, some use significant power)
Maytag fridge 19cuft mod:mbf1956hes call it 1,500 WH per day
Ser:11919935gt
Electrolux dishwasher mod:fdb1050reco Unknown... If using heat to dry dishes, can be >1.5 kWH per day
Ser:th62390562
Gas stove frigidaire 4 burner Unknown--Ovens typically use ~500 watt heater to light burners

I don't know if the above is enough information to give a very rough equipment schedule to base a very rough quote on or if I really have to go onto the next step of getting a better watt hour count first.

Look at the numbers--There are somethings that do not belong on solar power (off grid). Those include electric heaters, standard natural gas ovens, and other appliances with electric heat.

If natural gas is available, that is the way to go for heating.

If solar powered heating is still needed, then an efficient Mini-Split heat pump can be used off grid (of course, these are larger PV systems). Also, few people use heat pump based water heaters here too (like this GE Geospring unit).

Can anyone refer me to a package system, equipment recommendation or a supplier/design support for off grid systems?

Before we go there, lets look at the basic system design first (of course, our forum is hosted by Northern Arizona Wind & Sun--So we always suggest starting on their website first--but buying from NAWS is not a requirement to participate on the forum--we are all volunteers here and do not work for/with NAWS).

I would like to give a ballpark estimate and then see if she's still in the game.

I will go through the math using rules of thumbs to size the system--From there it is much easier to pick components that meet the size of the system needed (off grid solar components need to be sized to the needs, and it is very difficult to "add to" an off grid system to get more power if it was undersized--and over sizing is also very expensive--so getting accurate power estimates is critical).

The next step would be to Interview her to get a better idea of daily / weekly use of electrical items, trim down bigger loads with better efficiency, lifestyle choices etc. (like that juicer) where posible.

Moving to a new post because I will probably hit the per post character limit here.

-Bill

Photowhit · March 2013

Re: Off Grid Help

So Cal wrote: »

Dyson’s AM04 heater/cooler
Hair dryer, once a week
Water heater (on demand unit)
Maytag fridge 19cuft
....lifestyle choices etc. (like that juicer) where posible.

Any advise, referals, comments, recomendations or cautions will be appreciated....

I really wouldn't worry a lot about the juicer unless it's used for more than a half hour a day, it's likely not a huge load over all checking the fridge for it's usage and dyson heater/cooler for usage and wattage. and the on demand hot water heater should be a gas unit like the stove. If she's not been there before I think 'Coot has good advise, since her expectations will likely not be met, it might well lead to a bad reference.

Ooops, I forgot, check with the local permitting body to see if and what is allowed. Metro areas can be 'funny' about things.

Cariboocoot · March 2013

Re: Off Grid Help

One thing the OP might want to look at: the clients present utility bill. If she's living her preferred lifestyle now the consumption listed there may be a fairly good representation of expect power. It will probably also be an eye-opener.

For what it's worth, off-gridders tend to be minimalists and get by on <3kW hours per day. You can do it bigger, but of course that's more space, more equipment, and more money.

BB. · March 2013

Re: Off Grid Help

So--To give you some basic guidance:

~3.3 kWH per day (100 kWH per month) for a small off grid energy efficient home with "normal" electric appliances (lights, fridge, well pump, washing machine, laptop computer, energy efficient TV, etc.) is a good aim point.

You could probably live a very "near normal" off grid home with 8-10 kWH per day (240 to 300 kWH per month). You might even squeeze a heat pump A/C system or water heater in there (and using natural gas/propane for heating/cooking otherwise). Heat pumps are ~2-3x as efficient vs using resistance heating elements for those tasks. And makes it possible to economically use off grid PV power for those tasks. Even using a microwave+induction hotplate/range can be doable.

The average North American home uses around 1,000 kWH per month (~330 kWH per month) and probably 2-3x that amount of all electric homes/heavy Air Conditioner usage...

Anyway, from those numbers, I will start with 8kWH per day (the customer would still need to do a lot of conservation). Remember, at $2 per kWH for off grid power, we are looking at:

8 kWH per day * 30 days per month * $2 per kWH = $480 per month "effective" power bill (vs ~$48 per month for grid power)

So--Sizing the battery bank. 1-3 days of storage and 50% maximum discharge. Pick 2 days as a good middle number (use 48 volts for battery bank with a system this large):

8,000 WH per day * 1/0.85 inverter efficiency * 1/48 volt battery bank * 2 days of storage * 1/0.50 maximum discharge = 784 AH @ 48 volt battery bank

That is a good size battery bank and could support a ~6-9 kW AC inverter.

To size the solar array, we need to size it for the minimum rate of charge of the battery bank... 5% to 13% is generally the suggested charging range (charge during day, use most energy at night):

784 AH * 59 volts charging * 1/0.77 panel+charge controller deratings * 0.05 rate of charge = 3,004 watt array minimum
784 AH * 59 volts charging * 1/0.77 panel+charge controller deratings * 0.10 rate of charge = 6,007 watt array nominal
784 AH * 59 volts charging * 1/0.77 panel+charge controller deratings * 0.13 rate of charge = 7,810 watt array "cost effective maximum

And, we have to also look at how much sun you get in the area to make sure we replace the energy used. Using PV Watts with a fixed array tilted to latitude for Long Beach California:

Month    Solar Radiation (kWh/m 2/day)  
(kWh)
1      4.43  
2      5.00   
3      5.52     
4      6.21    
5      6.12      
6      6.09       
7      6.63       
8      6.79       
9      6.18    
10      5.46      
11      4.81 
12      4.34   
Year      5.63

I "toss" the bottom four months and assume generator usage usually--In this case, a metro area, using a generator very much is going to be looked down on (noise, smell, fuel storage, etc.)--So if this is very sunny area--We can use 4 hours of sun per day and cover 12 months a year (on average, stormy weather excepted).

So based on an 8kWH per day load with 4 hours minimum average sun per day:

8,000 WH per day * 1/0.52 system efficiency * 1/4.0 hours of sun per day = 3,846 watt array minimum

So, a solar array from 3,846 watt to 7,810 watt would be the suggested range. And ~6,007 watt array should be fine (and give extra power if the customer uses more than planned). (obviously the numbers are "not that exact"--Just keeping digits so you can check my math and follow where they come from).

Before we go down the equipment line--What are your thoughts so far?

-Bill

Off Grid Help

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