Monday, 28 October 2013

Harvesting the Sun ...

We have had a couple of request to supply some details regarding our solar installation here at the farm. 

Taking the path of supplying your own power is a constant learning curve, and thus the solution evolves from all aspects, if designed and though out properly most solar installations are scale-able, but not always at a small cost. 

Our system is 12V DC, this meaning that our nominal system voltage between batteries (storage) and inverter (DC to AC conversion)  is running what you would in essence find under the hood of your car. These guys are just a lot larger and heavier 64kg each.

1000ah Lead Crystal battery bank

The logical flow of energy is as follows.

Sun ->PV Array ->Solar Charge Controller ->Battery Bank ->Inverter ->Load 

We have a 750W PV Array, this consists of 3 250W 24V solar panels connected in series. giving us 750W @ 72VDC @ 9-10amps. These panels terminate on a 60A MPPT Solar Charge controller. This device regulates the charging current and voltage to your batteries. The Battery bank consists of 5 200AH 12V Cells connected in parallel giving us 1000AH of storage @ 12V. or 12000WH - AH multiplied by volts, then our AC power that keeps our appliances and lighting run is supplied by a 2000W inverter. 

This is the typical end of day read out on the Solar charge controller.

This gives you a good indication as to the amount of energy brought into the system that day, the second part to this delicate balancing act is obviously knowing what you are drawing from the system daily. To do this we use a nifty little device called an Owl Energy Meter, which gets connected to our 220V AC input. This device then monitors what we are using in real time logging all the historical data too.  

To the right is the Owl showing a current draw of 193W, this is very handy as you get a real time indication as to how much power you are drawing from the batteries at all times. 

Below is the 2000W inverter which takes our 12VDC storage and converts it to 220VAC. The 2000W is just the amount of concurrent power we can draw at any one time, don't think we have come anywhere close to the limit yet.

There is one thing to keep in mind, living off power provided by the sun is mind-blowing, but there are drawbacks too, we undertook a whole different lifestyle and awareness while prepping our move to the farm. All our appliances are "green" A+ rated or better, no toaster or electric kettle, even washing dishes the old fashioned way. Our hot water is a supplied by a gas geyser. 

Our current daily average power consumption for last month was 2.2KWH, the average family home in SA is using 12-16KWH, with North America way above that at 32-38KWH a day. We are still running a 660L fridge, 9KG Washing machine, 47" LED TV, internet, laptops, 9 5W lights (not used concurrently), 3 10W LED spot lights and a 50W fan, as mentioned above we are just very aware of how and when we use all this.