From: J & D Goldman (jmgoldma_at_dwx.com)
Date: 10/03/02
Message-ID: <003e01c26b4a$060a85a0$3edececf@gateway> From: "J & D Goldman" <jmgoldma_at_dwx.com> Subject: Re: Omega Garden - High-density gardening for small spaces/urban farming Date: Thu, 3 Oct 2002 21:00:44 -0500
>My main problem with the Omega garden is the source of the light.
>You're right. Artificial light is expensive. Directing natural
light
>into the
>center might be a better solution, and could be easily done with a
little
>
>bit of optical engineering.
>
>One of the universities designed an optical concentrator which was
>basically a light funnel -- they got concentrations up to 20,000 suns
>at the output orifice. Lower concentrations are easy to achieve. In
>fact, I can think of a half dozen ways to direct light into a system
like
>this.
>
>Then funnel that light into a light pipe system that puts the light
where
>
>you want it.
>
>You're the closest we have to an expert -- does this sound
reasonable?
>
> -- Chuck Knight
Thanks for the plug Chuck, but there are probably people out there who
are more deserving of the "expert" title. Let's say I've studied this
more than some, so let me share a few observations:
Natural lighting: Yes, in most cases natural light intensity will
really blow right past an artificial light source. Think about it.
The orb is 93 million miles away and you can't look at it without
being blinded. There aren't too many bulbs that are that hard on the
eyes! A common problem is when people put plants on a window sill and
supplement with artificial light when its cloudy (e.g. Seattle). The
plants still bend (a "tropism") towards the natural light.
But this isn't just about intensity. Two other main light factors are
light *quality* (what is the "color" of the light in terms of
wavelength mix) and light *duration*.
Duration: For general purposes, 12-16 hours of light each 24 hour
period works fine. There *are* facilities that light 24 hours a day
and it can be done. This does affect different plants to different
degrees and in different ways, but in a lot of cases is more a waste
of power than it is harmful to plants.
Also, with respect to duration, some plants are sensitive to
*photoperiod*. Onion bulbing, for example, is a response to long
days. That's why when Aunt Martha in Texas sends her favorite onion
seeds to son in Minnesota, after planting they bulb very early in the
year are will achieve the colossal diameter of a dime. Fine if you
like green onions, but they will never do much for you on a hamburger.
The long days hit too early in the plants life cycle, they bulb and
that's it. Likewise, the onions Aunt Martha got from Minnesota might
not bulb at all, but provide lotsa onion greens or a great jungle to
crawl through for the kids if the aroma isn't a problem.
To further complicate this, some plants only respond to daylength
if the temperature is right, like potatoes. Tuberization is a short
day response, if the temps are cool enough. An in other cases, its
not *really* a short day response, its a long night response. Think
that's nuts? Well, other people didn't believe it either. The clever
guys who discovered this in the 1920s figured that out by strobing the
plants at night. When they interrupted the "long night", even under
short days, the plant behaved as it did under long days. Yes, urban
lighting "pollution" can affect some plants...
And as to light quality. All that stuff I just told you about
photoperiod? Sometimes its just reds or blues that plants respond to.
If the intensity of certain wavelengths are insufficient, you get no
response to the daylength at all. Different light sources provide
different wavelength balances, incandescent being on the red side,
flourescent being on the blue, and the overpriced "plant lamps" try to
convince you they are best, although in many cases, all they do is
make the plants look nicer to the human eye and eat more of your
electric bill to deliver the light plants really need.
This is a deep and fascinating subject to those of us who enjoy plant
life, and believe me, there is a LOT more to it than I mention here.
I just thought I'd share some of what I have learned to help you sort
through some of the claims you may be seeing on the web.
As to the light pipe idea, looks to me like it should work. The
Japanese were interested in using a superinsulated structure to retain
heat and then bringing the sunlight in via a small opening. This is
the reverse of what you normally see, big open area greenhouse to
catch no-cost sunlight and then paying through the nose to keep the
temperature up. I'm anxious to look at this concept, but using a
dome, of course. :-)
Actually, one day I'd like to build a dome in three halfs. The largest
is the superinsulated north side (part 1), the second largest is the
superinsulated south cover (part 2). This is slightly smaller than the
north side, and rotates back inside the north side on suitable days,
leaving the smallest half (part 3) open to sunlight. Part 3 is glazed
like a greenhouse, and is stationary facing south, just inside of the
cover (part 2) that just swung out of the way.
Of course, we'd keep one Omega barrel going just to remind everyone
that innovation is always worth a shot, even if it looks kinda kooky
at times.
-Dan G.