Off the grid

Off the grid is a lovely romantic notion but it's completely out of the question for the majority of us. It means, inter alia,

  • Purchasing a huge battery pack of at least 10,000 dollars.
  • And, going without power and hot water if there is an extended period of inclement weather.

The batteries remain the single most expensive item in your budget if you plan to build a solar farm.




My own battery pack which is moderate in size, but certainly not sufficient to go off the grid, cost nearly twice as much as our large inverter; big enough to heat two ovens and a heap of small electronic equipment simultaneously, but hopeless once the sun goes down.

They are not only expensive, but they remain relatively fragile. If you discharge them regularly beyond their tolerance you can easily shorten their lives by a half or more.

A large part of the problem is that the batteries currently being used are new technology, and nobody really knows how deeply you can discharge them, or how often. Different sites will proclaim wildly different claims. In the case of my lead crystal batteries, the claims vary by fifty percent.

To my mind, it makes no sense to shorten the lives of your expensive batteries by a half or more just to save 500 dollars of electricity from the grid per annum.


Off the grid

Off the grid is a much better prospect, of course, if you live in Arizona where there's little cloud cover. Every evening you are assured of a geyser full of hot water, and batteries that are fully charged.

But then you have to pipe in water from some distant source.

For the majority of us, with access to both a municipal water supply and the electrical power grid, to my mind, it makes more sense to remain connected, but to reduce our consumption of these utilities.




Another consideration is that the inverter itself draws considerable power, whether you are using electricity or not; mine requires nearly 100 watts just to keep the element activated.

Leaving the inverter switched on all night whilst you are asleep, just to power perhaps three 10 watt flood lights, and the fridge which might come on twice for a short period, would draw in excess of a kilowatt hour and place a considerable drain on a small battery pack. It makes more sense to turn it off when you go to bed, and draw a small amount of electricity from the grid.

The purist who wants to be off the grid will see it differently. He is willing to sacrifice his batteries and that's okay; different strokes for all folks. But it is quite an expensive luxury beyond the means of the majority.

For those who live in an area where there is frequent wind, or running water at night, it's another matter; but they are the lucky minority who have other sources of green energy.


Harvesting rainwater

Harvesting rainwater from the roof is a simple business involving a network of underground pipes from the gutter downpipes (labelled 1 and 2), leading to a series of tanks or, better still, an underground reservoir. If you're off the grid then you must have battery power to supply the pump. 

These underground standard sewage UG110mm pipes collect the water from the downpipes, delivering the rainwater to a silt trap from which it overflows into a 25,000 litre reservoir.

Harvesting sunlight

Harvesting sunlight is becoming more affordable; the price of photovoltaic panels is coming down all the time. Also they are getting larger in size. I have just purchased three new PV panels, 1.5mx1.0m, 305W each.

Shadows on PV panels is something to consider.


Solar generator

Solar generator means connecting the panels to a regulator known as a MPPT, and then to batteries and the inverter; it's a relatively straight forward business. See solar powered generator for more details.

Think hard about the size of the inverter for your home before making a start; upgrading costs a lot more in the end. I wish I had gone straight to this 10kW big boy; then it would have hurt only once!

And never go to anything less than a 48V system; the losses in the cabling is much greater at lower voltages.

In short, do it properly the first time. Think, plan, read, talk to people before making a hasty start. Otherwise it hurts many times over.


Change over switch

Change over switch is vital if you are harvesting sunlight, but also want to remain connected to the utility. You'll still need it if you're off the grid, to connect to a generator in times of inclement weather.




There are many different ways of connecting up your electrical supply. I have my own home grown ideas, borne out of several years of experience.

  1. We have circuits that are entirely energised by the inverter, using solar power. When it's switched off at night they cannot be powered up. Our computers for example are supplied entirely from our own electricity; only clean, reliable energy for them.
  2. Then there are circuits that can be energised from either the grid, or the inverter, using a change over switch to toggle back and forth. For example, the electric oven can be powered during the day by the inverter when the sun is strong. At night however, if we use the oven which is rare, it can only be heated by the mains supply.

It is a manual system; if one sees a front approaching, then I can manually change over ahead of time to make sure the batteries are fully charged before the stormy weather arrives.

Fully automated systems also exist; for a price.


Solar power energy

Solar power energy is there to be had, but it does have pit falls. In theory, in the absence of inclement weather, it can enable you to go off the grid.

In short we use less than 5kl of water and less than 600 kWh of electrical power per annum from the grid, but I'm still very pleased we are connected. That's less than most folk use in a month.

Going off the grid would be a pipe dream for us; it would mean investing at least another $5000 in batteries. And we would still have cold showers when a five day mist envelopes our village; it happens several times every year, living on top of an escarpment.




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