The Power of Energy Efficiency

4 09 2011

We recently purchased three new LED globes for the kitchen to test from here.  I was hopeful they would do the job, but they actually perform over and above all expectations.  At about the same time, our power “bill” arrived, and this led me to finally post something about just how efficiently our house runs.  Hardly anyone believes we can run a house “with everything” (except a swimming pool, I draw the line there) on virtually zero energy.  As they say, the proof’s in the pudding, so here is a scanned copy of “the bill”…… (click on the bill for a clearer/enlarged view)

There are two sections to this invoice.  One is the amount of power we consume, and the other is the amount of excess power we generate via the solar power.  As you can see, the Utility states we use 2.5 kWh/day, and we generate an excess of 7.4 kWh/day (in some of the worst solar weather I have ever had to endure – and I sure hope those numbers go up soon).  That we pay only $0.2069 for what we use, and collect $0.5200 for our solar energy certainly helps us in getting an invoice in credit.  But the point lost on many people is that the main reason we have achieved this is because of the strategies we have undertaken to reduce our consumption from some 20 kWh/day 20 years ago, to just 2.5 today.  If you notice that the chart went up from the previous quarter, it’s because we started up a second freezer when we slaughtered our pigs and ran out of freezer space.  I expect that by Christmas we will have it turned off again, especially now we have a going AGA to cook our roasts in….

I have already explained how we reduced our refrigeration cost right down with the “Cool Idea”.  But I haven’t yet disclosed how we heat our water up as successfully as we do.  As far as I am concerned, there is only one way to heat water, and that’s the solar way.  Furthermore, if you do it properly, it is possible to achieve 100% solar fraction (that’s jargon for never boosting!), a little trick I picked up whilst learning all about Renewable Energy at the then Ithaca TAFE in the 90’s.

Basically, you have to tilt the collectors such that they are optimised for winter when the sun is weaker, the days shorter, and the water you want to heat is the coldest.  To calculate the best angle of tilt in the winter, take your latitude, and add 15 to 20 degrees. This will give you the angle from the horizontal at which the panel should be tilted which here on the Sunshine Coast is about 40 degrees.  Then, remove the tank from the roof, and put it inside your house somewhere warm, standing upright.  A vertical tank will not mix cold water with hot anywhere near as much as a horizontal roof mounted one.  Of late, most solar heaters are split systems like this, though most people still install them outside on verandas.

I should also mention the importance of a water saving shower head.  We bought ours twenty years ago when we first started living on tank water, and whilst I doubt it is still available, it is incredibly efficient at under 4 L/minute (about 1 US gallon for Americans).  The less hot water you draw from your tank the less you need to reheat, particularly important in cloudy weather.

You will notice our collectors are on a South facing roof, and as such need to be tilted up on a frame to face the equator at the winter angle.  This has been through destructive winds twice now…… and it hasn’t yet blown away!

To reduce one’s consumption to the level we have certainly requires commitment.  And attitude too.  You often have to spend money up front to make the gains, but I can assure you we are laughing all the way to the bank as the cost of power starts soaring.  I firmly believe that it is only a matter of time before you who read this have to pay the same rate we collect for our solar electricity for the energy you consume.  Will you be able to afford your current wants?

We did two other things in the past 18 months to lower power usage from 4 to 2.5 kWh/day.  One was to replace the 120W PC that used to live here with not one but two laptops.  They are rarely both on at once, but at just 40W each, does it matter?  And then, as digital TV becomes the norm, we replaced our aging 130W CRT TV not with a gigantic plasma screen or similar LED TV, but a same size 23″ LED backlit LCD device that barely uses 30W.  We don’t miss a big screen, because we have never owned one.  And yes I will admit that whenever we see someone else’s  monster TV that can be seen from space, it almost takes your breath away… but then, so do our power bills!

If you have been following this site for a while, you should know we never heat nor cool this house (though of course the AGA will make the place nice and toasty in winter!) because it is passive solar designed – ie the sun shines through into the house all day long in winter, and never in summer.

And those LED lights?  Well they have certainly come a long way, ours look just like an old fashioned incandescent light bulb, except they only consume 5W a pop.  At $20 I know they are not cheap, but they will outlast me with an expected life of 50,000 hours (which at 5 hours a night is over 27 years).  Unlike CFLs (at left), they have no Mercury to ditch in landfill (there are still no recycling facilities around here) and I like them so much I will replace another three as soon as I recover from the AGA Saga!

EDIT:  Since writing this, we have improved our consumption to even lower levels…………