Off Grid Washing Machine only PV system

Cipherion

Want to create a PV array that is small enough to put on top of an enclosed construction trailer(if needed) but would power my washing machine mainly (which is its highest usage). This is not a critical implementation and there is power within 75 feet. Only out of pocket expense here. No loans or hurry on any of it. I will never need more than 1 day of autonomy. If its cloudy for two days I won't run the machine. Here are my projected maximum load(s):


One load of washing at 40 minutes of washing time
120V. @ 10 amps = 1.2 KWH per hour

My average usage would be 0.8 KWH per day (or less). My once time per month daily maximum (probably never) might reach 2.4 KWH.

My solar insolation is as follows:

High: 6.34
Low: 5.23
Average: 5.85

Tentative plan:
1 - 250 Watt Canadian Solar panel CS6P (just picked this for price - open to any.
1 - 30A Solar Charge Controller 720W Panel Regulator with timer and light control (PWM brand) - (already have).
2 - Deep cell batteries rated at 210 amp Hours each (don't have any idea how to calculate this for my loads - guessed and these match my boat battery)
1 - Cen-Tech 2000 Watt Continuous/4000 Watt Peak Power Inverter 87% efficient item#69662 (already have - I can buy a better/small one).

I was thinking of using a small 100 amp Square D breaker panel with QO style breakers (heard you can used these for DC) to feed the inverter. Additionally if this allows for higher loads I may charge my laptop. Please feel free to rip this hodge podge idea to shreds. Need the input. Please advise.

John

Cariboocoot

Re: Off Grid Washing Machine only PV system

Welcome to the forum.

My advice would be to set aside money until you have enough to invest in a system that will work for you.
While you're doing that, read through the forum. Starting with this thread about washing machines: http://forum.solar-electric.com/showthread.php?18670-Washing-Machine-thread
They use quite a bit of power, both in terms of start-up demand and Watt hours.

Some of the problems with your equipment list:
250 Watt panel is likely a "grid tie" panel with a Vmp around 30, which means it will not work efficiently for any battery-based system on a PWM controller. Also it won't provide much in terms of power: maybe 650 Watt hours a day, and about enough current for half the amount of battery you've listed. The inverter is likely an MSW type which the washing machine's motor isn't going to operate at its best on. Might be alright, might not be.

If you haven't already, spend $30 on a Kill-A-Watt meter to get your power usage numbers. It's about the best first investment in solar anyone can possibly make.

Cipherion

Re: Off Grid Washing Machine only PV system

I will try and not make this too long. Basically I have several remotes sites I pack a generator to presently our cabin, my buddies cabin (helping him build one) and I am building a pole barn out in the sticks. Our cabin has a washing machine that I power with a generator that gets WAY to much use for a cabin but with 5 girls in the cabin in the summer there is a load a day. I need additional power above the generator at the cabin when I run my compressor and saws. While I like my generator I have always wanted to get into the solar realm and and putting power to the trailer for convenience, emergency power, and the looming zombie apocalypse while satisfying the geek side of myself seemed like a good bet. I know I could just go buy another generator but I would like to be able to show off my solar "trailer" to my construction buddies while showing it off the my computer programming buddies in the same breath. While I know there is a big push let everyone know load size I figured a washing machine would be my greatest. I have been reading for days and even woke up dreaming about solar. So that being said I am looking to design and build a portable solar bug out trailer that I will actually use. I assume it will not be cost effective with regards to power generation above just buying another generator but since I live in the city and the HOA won't allow solar this is purely a hobbie application. However I don't want to waste money like I did on my rock crawler...lol.

Thanks for the information about the "grid-tie" panels. I wasn't aware that there were differences.

Do you recommend 2 panels for a "washing" machine like application with a MSW inverter? One of the issues I have is that I don't even know what questions to ask. I have read a fair bit but since my desired application of PV should just be a generator I can't find anything to that will suffice.

At the end of the day I would like to have something PV that I can haul around, I made myself, and that is functional and doesn't fry my buddies Playstation or flux capacitor :O .

So I guess to summarize:

2 panels off-grid 240+ watts,
MSW inverter 1500 KW continuous,
no idea what kind of charge controller maybe a morning star, or Xantrex
and associated shut offs, mounting, wire and breakers.

This will not be "upgraded" to power the cabin. Not enough days there to warrant the expense. Any advice is appreciated.

John

westbranch

Re: Off Grid Washing Machine only PV system

Solar Rule #1 Loads WILL grow over time

Solar Rule #2 see rule #1

So you need to make a realistic estimation of everything you might use to pull power from your toy system...

Cariboocoot

Re: Off Grid Washing Machine only PV system

Some basic about off-grid power systems:

Batteries are the heart of the system. Whatever the load requirements, it is the batteries that provide the power. The solar panels recharge the batteries. Looking at the panels as a system basis will lead to mistakes in design.

Using two 220 Amp hours 6 Volt golf cart batteries as a base (220 Amp hours @ 12 Volts - a minimal system), you would need about 385 Watts of panel with a PWM controller to recharge them. This is if the depth of discharge is only around 25% (roughly 600 Watt hours AC) and 4 hours of good sun. Never mind all the little things that factor in.

With that power capacity in mind, a machine using 800 Watt hours would pull the batteries down to about 66% state of charge. Still within acceptable limits for both batteries and panels.

The problem with MSW inverters is that there's no guarantee the output waveform will be 'compatible' with the load demand. It's a guess at both ends as to how good the waveform is (measured as total harmonic distortion) and whether or not the device you want to run will find it 'acceptable'. As a rule, things with AC induction motors (like washing machines) will not like it. The output will appear to be low Voltage to them, and they will draw more current. Some things will not run at all. Some may burn up. You have to be cautious about it. Almost impossible to know in advance if it will work, or how well.

Off-grid power is expensive. You can use your gen to recharge batteries and then draw from them via inverter for "quiet power". This can be cheaper than solar and more portable. On the whole I don't think you'll see any advantage in running the washer from solar as opposed to from the generator.

NorthGuy

Re: Off Grid Washing Machine only PV system

You may be overestimating the power consumption by the washer machine. Unless you use a "hot" cycle where the machine heats water, it is usually much less.

You can buy a "Kill-A-Watt" meter. It used to be sold in Home Depot, but looks like they discontinued it lately (at least here), so when my old one broke, I had to order it on eBay. It will let you measure the exact power consumption of your machine.

Cipherion

Re: Off Grid Washing Machine only PV system

I am going to buy a Kill-a-watt meter I am curious as to how much I am wasting at home just leaving things plugged in. Thanks for the input. I guess heavy on the washing machine power usage to help account for any power loss.

I think it is really cool that there are knowledgeable guys out there willing to lend input. I didn't realize that there are panels that are off-grid and on-grid. Can anyone tell me what exactly the difference between the two are? Just from a quick precursory look it appears that the on-grid run a bit cheaper. I am assuming that one can use and on-grid for an off grid application. If so can anyone state how this might negatively effect the charging system?

So right now my tentative thoughts are as follows:

2 - 240 panels,
1- Morningstar charge controller
1- pure sine wave inverter (just in case I have to run a laser printer in the mountains...lol)
2- deep cycle 12 volt batteries.

Another quick question is it acceptable to run the batteries down to say 70% and leave them under powered but charging for 48 hours. While I live in a sunny area who knows if I were to ever take the trailer into the mountains for days on end.

westbranch

Re: Off Grid Washing Machine only PV system

simply an Off Grid panel is one that for a 12 v battery will output Vmp of ~17.5 volts so that it can replace the power used. 24V will need 2 v that , 48v 4 x that.

Grid tie panels can virtually be anything else, that with an MPPT Charge controller can be used off grid

Cariboocoot

Re: Off Grid Washing Machine only PV system

You don't want to leave batteries at 70% SOC for too long; it accelerates the sulphation process and shortens their lives.

If there really is charging happening (net current in to the battery) they won't stay at 70%. But it's part of the rules-of-thumb: 25% one day one, 50% on day two, start the generator on day three.

Cipherion

Re: Off Grid Washing Machine only PV system

By the way I found a great post from 2011 that is very similar to what I was thinking about. I thought I would throw it on this post so that others that are looking for a flexible approach may benefit.

www.wind-sun.com/ForumVB/showthread.php?10369-12V-vs-24V-System-for-quot-Off-Grid-Portable-Solar-Power-quot

Cipherion

Re: Off Grid Washing Machine only PV system

Cariboocoot wrote: »

You don't want to leave batteries at 70% SOC for too long; it accelerates the sulphation process and shortens their lives.

If there really is charging happening (net current in to the battery) they won't stay at 70%. But it's part of the rules-of-thumb: 25% one day one, 50% on day two, start the generator on day three.

C - I hadn't heard the 25/50/generator rule of thumb. Thanks for the input.