Small System

[marks]

My girlfriend and I are moving to a small house/cabin that is not connected to the grid.

There is a very small solar system installed: 300w of panels, 600w inverter, 4 - 12v 105ah batteries and a 20A regulator.

We want to run lights (LEDs), a fridge/freezer that uses 258kwh/year and is rated at 160w, a laptop, a desktop with a 650w power supply (estimate it uses about 400w), a washing machine and a couple of other smaller appliances.

I do realize that we will have to upgrade but budget is VERY tight so we do not mind running things like the washing machine on sunny days only, maybe my desktop too.

So, what I am asking is, what is the smallest system we can get away with?

I am particularly looking for advice from people with personal experience of running a really small system but obviously will welcome comments and suggestions from anyone who thinks that they can help.

We live in South Africa at about 34 degrees South and have a Mediterranean climate.

We are TOTALLY new to solar and have been researching on the net but I have to admit that I am feeling quite overwhelmed by the intricacies and also the jargon that is commonly used so I would ask whoever answers to please make it as easy to understand as possible.

Thanks.

Mark

[Naptown]

take a look at the items in my sig line particularly the off grid battery design and the calculator. Use the gaisma site to find the worst solar month of the year and go from there.

[thastinger]

Mark, is there a way to connect your cabin to the grid? I ask because you say money is very tight. You're talking about a 10K+USD system to run what you listed, then you still need a generator and will have to replace the batteries every few years thereafter. What you have now won't even run that fridge.

[marks]

Mark, is there a way to connect your cabin to the grid? I ask because you say money is very tight. You're talking about a 10K+USD system to run what you listed, then you still need a generator and will have to replace the batteries every few years thereafter. What you have now won't even run that fridge.

No way for us to connect to the grid.

[thastinger]

Well, you're either going to have to sell a kidney or get into energy conservation mode. You can convert a chest freezer to act as a fridge and it will only use .5Kwh/day which makes it 50% more efficient than the fridge you listed but you won't have a freezer. You can convert it for 60USD via a Johnsons controls external thermostate. Your desktop (if it is truely 400W) is a huge power hog, you'll have to figure out how attached to it you are.
Have you looked into a generator to run some of the larger loads?
Do you get alot of wind there?

[marks]

I used an online calculator to determine the power usage of my PC but am not sure how accurate it is. I do need it but not all the time.
Not sure about the wind as there is a mountain close to us that may block the predominant wind in winter.
I know we are going to have to make sacrifices. I just thought there may be creative ways to get around the problem, like making play when the sun shines.
My idea was to work out what I need for the worst case i.e. months with lowest solar insolation but to leave out the PC and the other power hungry stuff from that equation. Then just use them when I can.
Will also have generator backup.
The important thing will be to run the fridge/freezer all the time then laptop and lights when needed (calculated about 6 hours a day for each).
My biggest concern is getting the sizes right for the inverter and generator as I believe that you can damage appliances if they do not get enough power. Also, not sure if you can damage the inverter is asked to give too much power (worried about power surges when certain things start up).

[mschulz]

I used an online calculator to determine the power usage of my PC but am not sure how accurate it is. I do need it but not all the time.
Not sure about the wind as there is a mountain close to us that may block the predominant wind in winter.
I know we are going to have to make sacrifices. I just thought there may be creative ways to get around the problem, like making play when the sun shines.
My idea was to work out what I need for the worst case i.e. months with lowest solar insolation but to leave out the PC and the other power hungry stuff from that equation. Then just use them when I can.
Will also have generator backup.
The important thing will be to run the fridge/freezer all the time then laptop and lights when needed (calculated about 6 hours a day for each).
My biggest concern is getting the sizes right for the inverter and generator as I believe that you can damage appliances if they do not get enough power. Also, not sure if you can damage the inverter is asked to give too much power (worried about power surges when certain things start up).

Get a Killawatt meeter ASAP and start tracking your consumption of those items. I was surprised at the difference in actual consumption vs calculated. It saved me 300watts per day. Unfortunately the fridge is the hardest part I found. The way I am going (part time use so may not work for you) is the Engel T 45 fridge, as it works on 24v and draws 13 watts / hour. That fridge is going to kill you but the good news is that during the winter when there is not as much sun, it runs less.

[russ]

Get a Killawatt meeter ASAP and start tracking your consumption of those items. I was surprised at the difference in actual consumption vs calculated. It saved me 300watts per day. Unfortunately the fridge is the hardest part I found. The way I am going (part time use so may not work for you) is the Engel T 45 fridge, as it works on 24v and draws 13 watts / hour. That fridge is going to kill you but the good news is that during the winter when there is not as much sun, it runs less.

Excellent points and the killawatt meter is not expensive - you can find it locally or on line.

[Shockah]

Excellent points and the killawatt meter is not expensive - you can find it locally or on line.

Ditto.

I gifted 5 at Christmas. Amazon.com was the best price at the time... with free shipping.