21 July 2012

Preparations for Leaving the Grid

We always planned on a solar-power setup. It's a natural and obvious part of our attempt to live a more sustainable, eco-resilient lifestyle without forsaking all the perks of technology. When we designed the house we knew we would be unable to afford a solar-power installation off the bat, but we planned for it anyway. The design of the house reflects these plans -- the roof is pitched at exactly the right angle to optimally support solar panels at our latitude, key parts of the roof, eaves and walls are easily accessible for trunking additional wiring, the electricity distribution board is positioned close to the anticipated charge controllers and associated hardware to make upgrades relatively painless.

It's a pure application of what we software designers call the "Open Closed Principle" -- a design should be "open" for extension, despite being "closed" to internal changes.

Inspired and motivated by our visit to Ivan's Solar Centre in Scarborough, Cape Town, I have been working (in the conventional sense of "working at a job, for money") for the past several months in order to get enough cash together to install a solar-electricity system. It's not been easy for me... this "working for a living" idea increasingly strikes me as silly, tedious and ridiculous, but it's all in a good cause in the long run, and I have had the great good fortune to fall in with a fantastic bunch of people to work with. I suppose that, insofar as I want the toys offered by the conventional-money system, I choose to play their game. and I'm OK with that.

Aside from the money side of things, we're going to have to make a few changes around here, if we want to get rid of Eskom...

The very first priority is to cut down on our (already quite frugal) electricity consumption.

Water Heating

For most people who want to reduce their reliance on the Electric Grid, the first step -- almost without exception -- is to eliminate any electrically heated geyser, supplementing or replacing it with a solar hot-water system. In South Africa, the geyser accounts for something in the region of 45% of most households' electricity consumption. This in a country that almost entirely receives more Sun energy per square metre than Southern California. Crazy!

We never did install an electrically heated geyser, here at Braamekraal Farm, and have always relied on solar-heated hot-water. We designed hot water system so that the water circulation is driven by the thermosiphon effect, so we don't even need electricity for pumps. The solar water panels are backed up by a (horribly innefficient) gas geyser. We're having a pretty cold Winter, this year, and we've had to resort to the gas geyser for bathtimes perhaps once so far. On average 9kg of LPG lasts us 3 to 5 years for hot bath backup[1]!

So installing solar hot-water panels is not something we need to worry about. Installing them from the start was arguably the single best decision I ever made in my life, and has, at a guess, saved us 20 to 50 times the original cost (especially since I got them 2nd-hand, along with a 2nd-hand insulated geyser for storage.)

Space Heating

Central heating in any form is pretty rare in SA. Few homes have it, though over the past decade or two underfloor electric heating has gained some popularity. People who have it are currently paying very large sums for the privilege, as Eskom's tariffs have jumped hugely over the past few years. And they apparently plan increases of a further 15-20% per year for at least the next 5 years!

Our space heating is provided by an open fireplace. Yes, I know that closed-combustion devices are more efficient. We don't have one. And we are surrounded by abundant scrap wood free for the taking. Honestly, cooling the house through Summer is a bigger problem...

The next Biggies will be the stove and fridge.


Our fridge is now about 20 years old, and showing its age. I don't know its actual energy consumption, and it would be hard to find out without acquiring special test equipment. So, given that it is reaching the end of its life, anyway, we're looking at replacing it with a modern, energy-efficient fridge. Ask around, and everyone will tell you that Bosch make the most energy efficient fridges. Bollocks! These days every manufacturer has models that consume in the 290 - 330 kWH/year range. I've even seen one manufacturer boast a model with less than half that consumption. (The catch is that the price is damn near that of a small house, given which, it is cheaper to simply build a larger photovoltaic system!)

The big deal with refrigerators and energy seems to be to avoid:

  • double-door fridge-freezer systems
  • fridges with cold-water/ice dispensers in the door
  • no-defrost systems because they circulate warm water through the cold compartment to dispel condensation, which is a terrible idea if your concern is energy efficiency

We switched off our deep-freeze a year or two ago, and haven't missed it (aside from the savings evident on our electricity bills!) For the two of us, an up-down fridge-freezer combination is adequate.

I'd love to have another refrigerator for lagering beers, but I have some alternative ideas for fermentation cooling who's description will have to wait for another day...


Next is our (electric) stove. J loves her oven. And she bakes. A lot! In fact she is one of the staples of the weekly Blitz Barter, trading delicious loaves of seed-stuffed, whole-wheat bread to the whole community. The stove is easily replaced by a combination of gas cooker (not so usual in this country!) and a wood-burner. The wood-burner we will place in the lounge area (there's a section of wall specifically designated for this in our original designs) and it will double as a space-heater for Winter. Additionally we might extend the hot-water plumbing from the solar hot-water panels to coil around the chimney or through the back of the stove as cloudy-day hot-water backup! A lovely example of the permaculture-principle: Each design element should support multiple functions.

Originally I had ideas of building a biogas system to supply gas for cooking, but research suggests that biogas digesters are better suited to village-scale operation; a smaller group of people fail to generate sufficient biomass for the digester to work at efficient temperatures.

Sun-drying Tomatoes on the roof is always a bit
hit-and-miss in our relatively humid climate.
The oven will be a bit more challenging.

I will probably rebuild the Pizza Oven that we experimented with a few years back. Then, too, I've been wanting to build a solar oven for a while, now. The chief difficulty I have faced is sourcing suitable reflective material along with enough money for the building materials. For indoor, For Winter baking we will have the wood-stove. The idea of the Pizza and Solar ovens is to avoid firing ovens indoors during the larger part of the year when the weather is too hot for indoor baking. Solar ovens and dryers also play extremely well into J's extremely sought-after rusks ("biscuit" to American, I believe) and our preserving fruit and veg by dehydration.

The chiefest difficulty of all is J's emotional attachment to her oven.

Everything Else

Our lighting is already (old-school) fluorescent tubes, so consumption is already low, and easily converted to 12V DC to avoid inverter losses. Replacement with LED lighting is a possibility, but I am not convinced that the price/energy balance makes sense yet. Maybe in a few years?

One of the oddball things that we do have to worry about is our water pumps. We have 2 pumps, one supplying household water (via a header-tank situated in the roof) and another pumping dam-water to the garden and brewery (for coolant water - I promise it's not used in the beer!) Their energy consumption could be quite significant, but I don't know yet. My instinct is that, though they draw an appreciable current while they're working, they don't work very often, nor for very long. I still need to do the math on these to figure whether the cost of replacing the motors with DC motors will outweigh the cost to run the existing motors from a battery/inverter setup. I guess that much will hinge on how much current the draw, which affects inverter sizing.

The other significant electric-energy consumers are my computer, which is switched on for around 12hours a day. I might have to replace it with a laptop or one of the newer low-power machines. (I hate laptop computers, though.)

We will also need to "tidy up" all the small parasitic devices - myriad battery chargers, microwave-oven clock, cordless phone that needs constant powering, DSL router, TV... the current-draw of any one or even a few of these things is tiny. But they're on all the damn time.

It's quite difficult for me to size a photovoltaic system, despite having years of records of our actual electrical energy consumption, mainly because we still use the electric stove/oven, and that's a huge factor. So our current consumption of 250kWH/month might be halved without it, but we don't really know and, I suppose, will have to take an educated guess.

I do have a sense of urgency about this. Aside from Eskom increasing their prices hugely (and we're in the category of their users that always get hit the hardest by their increases) I think that photovoltaics are currently at a sweet-spot of availability and price. As time ticks by and energy supplies globally become more fragile, erratic and expensive, prices of alternative energy systems will b driven upwards.

My so-far-still-rough estimates indicate that I can put together a photovoltaic system of adequate capacity which should pay for itself in 3 to 4 years. Not too many investments can boast such a quick payback.

Time to get serious and get Eskom the hell off my lawn!

[1] And the house design allows for the gas geyser to be easily replaced by an outdoor, wood-fired heater, or circulated via the (planned) wood-stove[2] chimney.

[2] See later in this post...

1 comment:

  1. Your article makes more sense, the nature itself can help us to live efficiently without over using our resources. Keep up the good work.


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