Basic Build Advice

[Chordaroy]

Hi
I’ve got a bush shed and just starting in solar. I would like to run a fridge of solar my old gas one gave up on me.
I’ve been given 8 190w panels and have a 1500w modified sine wave inverter.
I would like advice on where to put my money to finish the project.
First use the 240v fridge freezer I’ve got or buy the flash 12-24v solar fridge?
Batteries- based on above might be as many as four 100 amp/hr ones to run 240v fridge, yes? Solar fridge uses 40amp hours a day apparently. Not sure about 240v fridge because it doesn’t run all the time I’m thinking it could need 200amp,hours a day (guess) maybe more.
Controller. What size to manage 8 panels into 12 or 24 volt array. Only thinking 12 cause I’ve got the 12v inverter but that could be sold to get a 24v one if it’s cost effective and helps with battery array costs.

Any help would be greatly appreciated.

Chord

 

[John Frum]

Hmm... what is the make and model of the 240vac fridge freezer?

AC Electric motors don't like modified sine waves.

That fridge is actually 240VAC@60hz?

 

[Chordaroy]

Oh. Wasn’t aware of the AC motor issue. Been running a small bar fridge off it ok. I thought the modified inverters had improved lately.
The fridge/freezer is a Westinghouse RJ340M (727 kWh/year). Not sure of Hz?
I have a upright freezer Palsonic PAL180FZ (362kWh/year).

I did read somewhere that freezers run on low as fridge are a better option than a fridge so the kWh/yr figures might attest to that.

My main question is around where to put my money to get a fridge up and running. Obviously I need batteries and a controller/regulator but I'm looking at a 12-24v fridge as an option as well. Obviously trying to do it as cheaply as possible but with an eye on future expansion.

Thanks for the reply.

 

[John Frum]

Oh. Wasn’t aware of the AC motor issue. Been running a small bar fridge off it ok. I thought the modified inverters had improved lately.
The fridge/freezer is a Westinghouse RJ340M (727 kWh/year). Not sure of Hz?
I have a upright freezer Palsonic PAL180FZ (362kWh/year).

I did read somewhere that freezers run on low as fridge are a better option than a fridge so the kWh/yr figures might attest to that.

My main question is around where to put my money to get a fridge up and running. Obviously I need batteries and a controller/regulator but I'm looking at a 12-24v fridge as an option as well. Obviously trying to do it as cheaply as possible but with an eye on future expansion.

Thanks for the reply.

inverter conversion penalty is ~0.85

 

[John Frum]

Seems you are in australia where 230vac@50hz is the national standard.
Here is North America fridges and freezers are usually 120vac@60hz.

 

[Chordaroy]

Sorry I don't know what that penalty means. Yes I am in Australia.
My kitchen fridge is 50hz. The one in the garage must be as you point out just cant get to it at the moment. Typical garage full of crap.
J

 

[John Frum]

Converting from dc to ac is 85 percent efficient.

 

[JeepHammer]

Converting from dc to ac is 85 percent efficient.

I always consider the losses for the charge controller and the batteries along with inverter.
Depending on battery chemistry, the losses are commonly 30-35% and sometimes more.
Add in 'Idle Time' the fridge ISN'T running and the inverter is still drawing 150 Watts or more on 'Stand By' and you can count on 35% or more in losses...

Inverters with Low Consumption in standby mode (Often 15 Watts instead of 150 Watts) have limitations, but are generally worth the effort.
They can't have ANY load on them for the low power 'Idle' mode to kick in,
For instance a mechanical thermostat in a fridge that DOESN'T consume power like an electric thermostat will,
The draw from a wall transformer or thermostat transformer will cause the inverter NOT to go into 'Idle'...
So you have to pay attention to what's hooked up and drawing power for an inverter with low power/idle mode to work.

I found this out the hard way,
The reason my power strip outlets with wall transformers plugged in are on a twist knob timer.
Hook up what you want charged, twist the knob to connect, when the devices are charged the transformers don't keep sucking power and keep the inverter in full power mode.

A fridge made for solar power is a little more expensive, but it will have more insulation & will have a mechanical switch thermostat instead of grid tied poor insulation & electric thermostat.
We say "Solar System" for a reason, when done the most electrically efficient way everything works together in a planned system...

There is a reason 'Grid Tied' inverters are so efficient (no charge controller or batteries) at 96-99% efficient.
It's true they will 'Clip' any over production from the panels, which you MUST consider as Losses (from maximum production POTENTIAL),
BUT,
They allow for direct usage from panels to appliances without charge controller, battery or inverter losses common in smaller battery systems.

Even stand alone mini-grids (AC coupled), are 96% efficient since the batteries only set the timing of the sine wave when the sun is out and panels are producing.
Batteries only come into play at night or when sun isn't shining.
High voltage batteries are more efficiently charged from high voltage panel output (less conversion losses) so even the battery side is more efficient.

With a sun sensor switch, your batteries can charge from grid tied AC output fairly efficiently and cut off batteries at night so you don't get a 'Charge Loop'.
Switches are $15 a piece, commonly used at 230/240Vac on outdoor security lights so it's cheap & simple to do.