SOLAR POWER

[watertrade]

Hi,

This weekend I'm looking at a house that is off the grid. The power lines come to the border of the property so it’s possible to have town power put in but at a cost. I'm hoping any experienced solar power users could give me some advice as to what I should be looking for and what I should know about solar power - the house was built in 2005 so I presume the solar was installed at the same time. There is a generator to charge the batteries if needed.

Wondering mainly about maintenance, problems, life span etc.

There is plenty of info on the net but is there anything they don't tell you!?!

Cheers

[Legba]

They don't make 12 volt washing machines.

[watertrade]

They don't make 12 volt washing machines.

yeah,

if 12 volts was all you had to rely on it would be hopeless.

I'm pretty sure a 240 system is a minimum.

[reshroomED]

Actually, you can readily buy 12VDC washers. Off the top of my head, I can't think of a household appliance that isn't available.

The problem with high-current draw devices (most items with motor, compressor, or heating element) at low voltage is that you will need *extremely* heavy wiring if they are more than a few feet from the battery-bank. So the usual set-up is a combination of 12VDC devices (low current - lighting etc) and 240VAC for the more costly to run gear.

Things to look at are battery-bank size (Ah), type (should be deep-cycle of some description), and age, panel capacity (W) and type, inverter capacity and type, and genset capacity (W).

It's near impossible to say what these should be without knowing how much power you will be using, but bigger is definitely better in this case.

Location is also a major factor as solar is only good when the sun's shining. If the house is in the ACT I'd suggest contacting a solar system *installer* in your state and find what actual percentage of the time you can expact the panels to be operating.

Maintenance consists of keeping the panel surfaces relatively clean, and periodic checking of batteries.

All components should have a greater lifespan than you, bar the batteries, which could need replacement every 5 - 10 years.

This is all pretty general, so if you can provide some more info or ask for specifics I can probably reply in more detail.

cheers,

ed

[Torsten]

you can get pretty much all appliances in 24V [incl washing machines], but you might not have much of a choice in brands and features.

personally I would run all lighting on 12V and have most of my small appliances modified to 12V too. High power appliances like powertools and washing machine I'd run from a 240V inverter. The benefit of such a set up is that you won't have much power loss for the 12V applications and you only have to run the wasteful inverter when you are actually in need of 240V. I've seen plenty of set ups that work like this. It requires a bit of planning and foresight so you have a 12V spine throughout the whole house [12V need a really really thick wire to travel distances] and a dividing wall that has all the 240V plugs on it [eg kitchen, laundry and workshop sharing the same wall].

If you've got plenty of money then just plan for the extra 20% power you need for inversion to 240V and have an otherwise normal house. This latter option might be more suitable if you are planning to sell the house at some point and your potential buyers would be likely to put in grid power.

Generators are good for emergencies, but you really don't want to rely on them daily with the way the fuel prices are going.

[watertrade]

thanks for the help guys - I will get some photos tomorrow and make some notes.

I think whatever happens I will have to change my lifestyle a bit in regards to power consumption.

Ed, I'm hoping to see who installed the system and then go and have a chat with them. the property is just on the NSW side of the ACT border on the eastern side of a small hill.

I will let you know how I go.

this is probably the closest weather station.

http://www.energymatters.com.au/climate-da...amp;find=Search

cheers

[watertrade]

ok I went and have a look at the property.

the solar stuff is as follows..

The solar charge controller is this one..

http://www.energymatters.com.au/plasmatron...ller-p-100.html

there are 6 of these exide 4RP1600 batteries.

It doesn't really make much sense to me at this stage.

T & Ed, are you guys on solar?

Edited June 8, 2008 by watertrade

[reshroomED]

Don't have solar myself but used to design and build low voltage measurement and control syestems for the oil/gas industry, so have a fair knowledge of such.

OK, that's a 24VDC system with 1600 Ahr of battery storage (a Google of "exide 4RP1600 price" may be of interest).

Really comes down to how big are the panels and batteries, and how much juice will you use in a day.

Roughly it goes like this:

Panels will provide 'X' Watts.

Batteries will store 'Y' Amphours, in your case being 1600Amphours, so it's sort of like your batteries will supply a 1Amp load for 1600 hours or a 1600Amp load for 1 hour. But now it gets a bit wobbly, because the more you drain your batteries, the faster they will die, ie. taking a battery down to 80% of charge may give a life of 5000 cycles (each taking it down to 80% then recharging), whereas using it until 50% charged will give something like 1000 cycles (these are just ballpark figures). So you really want to only drop your batteries to 75% or so.

Now you're left with 400Amphours out of your 1600Ahr storage.

You've got a 24VDC system and assuming that this solely powers an inverter (bumps the voltage up to 240VAC), and that the inverter is 80% efficient, gives you *very*roughly 7680Whrs per day (Watts = Volts x Amps, so 24VDC x 400A = 9600W x 80% = 7680W). That's 7.68KWhrs as you'd read it on your power meter in the average house so around $1.50 worth of electricity.

So you need to check the Wattage of all the items that your planning to use regularly and add it up (All electrical devices have their power consumption in W on them somewhere). Fridges use about 700Whrs/day, multiply hrs used by Watts used for other devices.

This figure needs to be less than 7680W or you'll need generator assistance, and your panels need to be able to supply the amount used (up to the 7680W max storage).

From memory average usage is around 7.5KW/day, bust best verify this.

cheers

ed

[watertrade]

Thanks Ed, that’s great -

Your calculation of 7.68KWhrs for one battery - x6 for 6 batteries gives a total of 46KWhrs a day

The average daily usage on my last power bill was 9.9KWh (we use gas for heating and hot water) and have evaporative cooling

It seems (from what I have read) these systems are designed to potentially store a few days worth of energy for cloudy days.

Which makes 46 Kwh sounds about right...

From the actewAGL website ---> the average Canberian uses 8000KWh a year = 21.9KWh a day!

I have looked up the number of cycles and % discharge for those batteries.

1500 cycles to 80% DOD

2500 cycles to 50% DOD

3300 cycles to 30% DOD

4000 cycles to 10% DOD

if I'm using roughly 20% of the charge I will get about 3500 cycles / days - about 9.5 years use from the batteries (maximum at 20% ) and about 20years from the panels.

Thanks Ed - that’s helped put it into perspective.

Do you know anything about pumping water?…. ;) just kidding.

Edited June 9, 2008 by watertrade

[ENtiTY]

Ahhh, I'm affraid WT that those calcs were for all the batteries together Each battery is 4V, by 6 is 24V at 1600 Ah. 7.68KWhrs is the total for all the batteries not each. You'll need to re-think how you use your power in that house.

[watertrade]

hmmm indeed - thats not going to cut it! mains power is about 100 meters from the house - might have to get the mains connected if I want to continue my energy hungry lifestyle!

[watertrade]

I should really know this...

but if one battery is 1600Ahr - 6 batteries = 9600Ahr or doesn't it work this way?

[ENtiTY]

I should really know this...

but if one battery is 1600Ahr - 6 batteries = 9600Ahr or doesn't it work this way?

Depends how they are connected. If all the batteries were connected + to + and - to - then you would have 9600Ah @ 4V but seeing as the system is 24V then the batteries must be wired + to - to achieve 24V with an Ah value of 1600.

I don't know dick about solar power systems but I do know how to wire batteries

[Otorongo]

7.68 kWh a day is huge. My average is 2.2 kWh / day, and that with an ancient fridge, electric cooker and my laptop on for 16 hours.

[kadakuda]

if your really worried about energy suckers like heaters/air con/range etc, you can always hook up to the main and only use it for your 220 appliances. here things like heat/aircon/stove etc generally run off 220. use the solar for the smaller stuff like lighting and tv.

we use about 5kw a day and thats for some air con, constant fan/computer and a bunch of plant lights. we also use water on demand style water heater instead of a water tank that is always heated. but these systems, though saving long run juice, have a huge draw at once to supply the hot water fast...

[TG83]

Not sure if it applies everywhere, but a friend of mine down here just got a 2kw system installed that feeds directly back into the grid. He uses grid power alone but with the solar feeding back in he never pays any electricity bills. That seems to be where things are heading in the city at the moment for the serious solar guys who are willing to fork out the $10k-20k, then you also have no problems about draining too much energy. Use the panels to pay the bills

[synchromesh]

http://www.youtube.com/watch?v=I8PxCmBs-qc

[Guest svarg26]

to keep your current lifestyle and live off grid. you really should consider buying or building a wind turbine. a 24v wind turbine will easily run a washing machine. i run my pool pump for 5hrs a day, everyday and run my laundry with a wind turbine.

hope you enjoy it as much as i do.

peace.

[synchromesh]

Sounds great man. Thanks for the info.

[San Rainbow]

how big is your turbine svarg?