Mid-way between the autumnal equinox and winter solstice we
find ourselves in the unenviable position of short days and long nights, and
looking forward to even shorter days and longer nights for some weeks to come.
Despite this, our renovated, passive solar villa has been performing well – the
indoor temperature has not dropped below 18 degrees in 2013. (More on this in
subsequent columns.)
The scientific explanation for the change in day length is
that the Earth’s axis is ‘leaning’ the Southern Hemisphere away from the sun
slightly more each day until June 21st. The way we perceive the sun
in relationship to ourselves is that it rises a little further northeast and
sets a little further northwest each day, as well as hanging lower in the sky
at noon. Mind you, this is gradual. It takes 6 months for the ‘tilt’ to change
from the sun’s highest point in the sky – and longest day of the year – and its
lowest point in the sky.
A good eco-designer takes his of her lessons from nature.
And nature takes his or her lessons largely from the sun. Using the transitive
property, you can get the rest.
In the space below, I’ll explain two examples of good
eco-design that take full advantage of the predictable behaviour of the sun:
one biological and one physical.
WBG, sold out quick-as.
If you were at Whanganui’s Saturday market for its last
session before Christmas 2012, you may have been among the lucky few to have
purchased The World’s Best Garlic. There is a lot that goes into growing The
World’s Best Garlic besides humility. One important ingredient is timing. When
I arrived in New Zealand five years ago I was told: “Plant garlic on the
shortest day of the year and harvest it on the longest.” Generally speaking,
this translates into June 21st to December 21st.
Please be aware, however, that this has nothing to due with
full moons, cow poo vortexes, or Grecian Formula 44. It does have to due with
soil temperature and gradually increasing sunlight day by day for half a year.
Also be aware that growing The World’s Best Garlic involves
the right kind and amount of compost, mulch, and watering regimen, all of which
are highly protected trade secrets.
The other example of good eco-design involves two examples
of solar hot water that are dramatically different from one another but each
serves its own users most appropriately. One system is set on an acute angle
and one on an obtuse angle to the sky. In other words, one system is set up for
maximum efficiency in the winter and one for maximum efficiency in the summer.
Solar hot water set for a winter sun.
The solar hot water system on our home is set for a winter
sun angle because we know that there are fewer total hours of daylight in
winter, and that our insulated tank loses more heat each night in July than in
January. There also tends to be more rain and clouds in winter, so we need to
take advantage of every clear patch and fine day.
Even set at this high angle, our system can boil over any
given day of the summer if we don’t use enough hot water. This ‘boiling’ water
shoots down the gully trap as a safety feature to the system.
Solar hot water set for a summer sun.
So who, you may ask, would set their solar hot water system
for a summer angle when there are plenty of long, fine days. Answer: YMCA
Central’s Raukawa Falls Adventure Camp. They get heaps of visitors all summer
long, many of whom want a warm shower at the end of each day. But for much of
the winter, the camp lays more or less dormant, and a back-up wood-fired hot
water system can easily fill in when needed.
As spring follows winter, so form follows function…if the
design is good.
