re: solar heating, empirical measu(r)ements & experience
15 may 1996
william r stewart wrote:
>i would recommend talking to a number of different energy consultants.
me too. i usually start by asking "are you familiar with ohm's law?"
that filters out more than half of the "energy consultants" i've met,
but asking this question is sometimes embarrassing all around...
here's another litmus test for an energy expert: what will the average water
temperature be inside a 4' cube full of water surrounded by 5 r20 foam walls,
sitting outside in december, when the air has an average 24 hour temperature
of 36 f and the sun puts 1,000 btu/ft^2/day of heat into the r1 glazed side
of the box? and how will that change over time if we shade the sunny wall?
anyone care to answer that question? i'll offer a $10 reward to the first
person who answers it correctly.
>nick does have a lot of theories, though he considers many of his untried
>pet theories to be far superior to anything anyone else has ever conceived.
it's hard to know how to dissect that sentence :-) it looks like an insult.
and untrue. most of this stuff was conceived a long, long, long time ago.
new weather data, new arrangements of systems and new materials and controls
make it ever more practical and cost-effective and efficient now, but that
isn't the main problem...
yes, i'm smarter than most people ("references please"--i belong to mensa)
and i know a lot more about physics, and i've thought a lot more and in more
depth about solar heating and have more engineering degrees than many house
designers, backyard crackpots and armchair a.e.r posters who like to talk
about alt.energy but haven't done any at all, or pv hobbyists who have
learned how to screw a system together but don't know ohm's law either, and
i do think _some_ of "my solar theories" are the cat's pajamas, especially
the ones that seem to make sense with my simple understanding of physics,
and the ones that really do work... the ones we've been trying out now in a
2' x 4' x 8' tall structure with an electronic data logger and modem inside,
in the real pennsylvania winter outdoors on the roof of the physics building
at ursinus college in collegeville, pa since november 4... and physics prof
paul bashus and i have managed to hornswoggle our solar theories on paper
past the technical review committees of two international conferences in
the last year, as well as a number of phds, who have accepted our solar
closet paper for presentation at the unesco-sponsored world renewable energy
congress in denver from june 16-21 (firstname.lastname@example.org registration
fee increases from $340-740 after today, may 15), whose steering committee
alone has people from 130 countries, and i've talked and run sessions on solar
heating and cooling techniques at several us conferences, but. . .
serious scientists and engineers consider solar closets and sunspaces
"trivial physics" and "unoriginal research."
many scientists are out collecting funding to improve the solar collection
efficiency of some system from 16 to 17% by adding another $10/ft^2 to the
cost of something that already costs $30/ft^2. this kind of solar house
heating technology has been around since edward morse invented the "trombe
wall" in 1881, at least, and it's understood by many people who know what
they are talking about, and a lot more who don't. solar house heating just
hasn't been done well yet, outside of the southwest, on an significant scale,
partly because the field is peopled by ignorant hucksters, partly because
we are still waiting for the government to help make that happen... but
this is lumberyard and hardware store science, not stuff for theses and
nobel prizes and nrel grants. it's waiting for bold entrepreneurs. and
more expensive energy prices, or people who care more about the environment,
or government regulations that make not caring more expensive...
many heating and cooling engineers are working on heating and cooling systems
for skyscrapers, or heat pumps, where the money is today.
i've only been doing this full-time for 2 years now, after 25 years of
electrical engineering, and i'm still learning. some things seem like good
ideas on paper but really do have to be tried out, and improved somehow for
some applications, or proved to be impractical for others, like bubblewalls.
some things don't need to be tested much, like low-thermal-mass sunspaces,
and some things do, like bubblewalls. it's important to know the difference.
bubblewalls are the subject of an old swedish patent (i wish i had a copy.)
the original application was storefront windows. they have been tried in
this country over the years by people like john groh, a new york grower (?)
and dr. merrill jenson at u arizona and dr. otho wells at u new hampshire,
who concluded in 1977 that bubblewalls were not practical night insulation
for commercial plastic film greenhouses simply because those greenhouses
need to be put together so roughly and quickly in the field by unskilled
people (so as not to raise their basic cost of 50 cents per square foot :-)
that leaks in such a system could not be avoided. everyday leaks in plumbing,
plastic film connections, etc. these are real problems, and i don't mean to
minimize them, but they are also application-specific, and not hard to solve.
dr. wells says that windows in solar houses may be a different situation,
since they can be made more carefully... he also says he only got a us
r-value of 1.5 or so out of his 3"-6" thick poly film pillows, so it seems
we need to improve the bubbles themselves somehow, make them smaller and
longer lasting, with thicker walls perhaps, or go work on something else.
dr. aristid v. gross of temple u and the blind belgian physicist joseph
plateau (1801-1883) both made bubbles that lasted over a year...
dr. wells was using an open system, more dustprone than a closed one, making
bubbles at the top of a 25' x 196' double poly film greenhouse to fill the
double poly film walls all round. he put slits in the plastic film, some
with sewn-in zippers (he said sewing zippers into poly film isn't easy),
to let some air out at the endwalls. he found he had to make more bubbles
every 2-4 hours, to keep the walls full of bubbles. dr. jenson experimented
with a photosensor to do this automatically, and also tried adding dyes to
the bubble solution, which were diluted so much in bubble from that they
had little effect. another way to keep the glazing cavities full is to keep
a layer of bubbles moving slowly from bottom to top in a continuous fashion.
another is to use temperature sensors to measure the r-value. dr. wells
said the small bubbles tended to settle out quickly and become liquid
again at the bottom...
another problem: dr. wells mentions that the bubble distribution was not
uniform--big bubbles and open spots, thermal shunts with no bubbles, up to
1-2' in diameter would often develop. this might happen less if bubbles
move continuously up from the bottom instead of intermittently down from
the top of the cavity. dr. wells used a basic solution of 3% type e dust
reduction foam (a better choice might have been firefighting foam) from mine
safety supply in pittsburgh (now mine safety appliances at (412) 776-7700?)
with 1% propylene glycol as antifreeze, because when the bubbles freeze
inside the outside layer of poly film, they break, and the r-value goes
down and their friction against passing bubbles goes up, and he didn't want
water frozen in pipes either. can we make frozen bubbles that don't break?
yes. that's been done, often, in public at the san francisco exploratorium
by dr. ilan chabay, called "one of the world's foremost authorities on
frozen bubbles," in john cassidy's _unbelievable bubble book_ for children
(klutz press, 1987.) has dr. wells ever talked with dr. chabray or dr. grosse?
i don't think any physicist would call bubbles trivial physics. child's play
maybe, but not trivial :-) we need more child-like physicists.
there is at lot of work to do in this alt.energy field, and a lot of it,
like preventing leaks or finding the right soapy solution is not that
technically difficult. there isn't a lot of funding, but there's a lot of
work to do, a lot of opportunity for serious backyard builders and high
school science fair students to do interesting things that may later become
good, cost-effective, reliable, simple socially-useful techniques and
products, given some common sense and education and patience and a lack
of greed and shortsightedness.
some things need to be tested and developed a lot, others are no-brainers,
if we start thinking from scratch. not everyone wants to live in an
experimental bubblewall house, but lots of people like sunspaces. there's
a huge gap between commercial plastic film greenhouses costing for 50 cents
per square foot and residential sunspaces costing $50-150 per square foot.
who will fill it? nrel? no...
there's another gap between serious scientists who say all this is trivial
well-understood physics, while they collect their salaries working on more
and more exotic research, and alt.energy.renewable experts who say it won't
work, it's been tried before, trombe walls are the cat's pajamas, etc, etc.
>i would have to say that distributing the energy evenly to where it is
>desired is yet the most important half. many houses have been built
>where some rooms overheated while others grew cold. distributing the
>heat to zones at specific times during the day is an interesting challenge.
sure, that's important, but let's collect the heat to begin with, will, and
then worry about that problem. or wear a sweater in one room and take it off
in another. that's hvac. air pushers, ducts and fans and blowers and zone
controls, to move warm air out of our sunspace or solar closet around the
house. not too hard in a new house, and harder in a retrofit, unless we can
mix the warm air into a big room or dump it into a return grate somewhere,
somehow. that's a lot better understood than solar heating. straightforward
everyday cranking, for someone who knows how to do it.
it's a snap to save energy in this country. as soon as more people become
involved in the basic math of heat transfer and get a gut-level, as well as
intellectual, grasp on how a house works, solution after solution will appear.