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re: utility costs
7 apr 1999
 wrote:
>nicksanspam@ece.vill.edu wrote:
 
>i've sometimes wondered what would happen if a homeowner covered their lawn
>with aluminum foil, all arranged to reflect the noon sun onto the house.

foil blows away, gets dirty, and oxidizes with moisture, vs. white pebbles
over weed barrier or snow or a large shallow frozen pond, to gain 30% or so.

>imagine a giant solar collector that increases the amount of light on those
>dark winter days, and makes things toasty warm as well.

steve baer's working on "sameshine" produced by a large moving mirror
controlled by a microprocessor (for now) that reflects and concentrates
sun into a powerful beam that shines in one window all day. he sometimes
directs 10 new mexican suns into his office window, enough to make
a sheet of newspaper burst into flame. 

he writes (with his usual charming elegance):

   heliostats--sameshine vs sunshine

   a heliostat reflects light onto a target. the sun may be at its
   original strength (less losses on reflection) or it may be concentrated 
   or dispersed. the amount of sun a heliostat is able to reflect to an
   ideal target over a day is greater than the amount of sun striking
   any fixed surface of the same area but not quite as great as the best
   tracking surface, for the heliostat turns only halfway into the sun. 

   think about the thousands of ways the sun could be used if it did
   not move in the sky. we cannot prevent the sun going off and on,
   for the earth still spins and clouds come and go, but we can easily
   and eventually inexpensively have the sun stand still. today no one
   craves the sun to stand still. if we suddenly could produce inexpensive,
   reliable heliostats, there would not likely be an immediate large
   demand for them. it will take time for people to discover that sunlight
   passing through space always in the same direction has a multitude
   of uses that turning sunlight cannot have. such sunlight will indeed
   need a new name, samelight, and sameshine. 

   lighting

   a square foot beam of sunlight can replace 200 watts of electric
   lights but sunlight moves and is soon shining in the wrong place.

   samelight can be distributed directly by beam or fiber optics. samelight
   can be dispersed inexpensively; 20 square feet of samelight can light
   a 2000 square foot building. to light, samelight needs electricity as
   a partner for the predictable and unpredictable periods of unlight
   (when there is no direct beam radiation.

   in the southwest, over a year, a thousand watts of samelight could
   replace 2000 kwh of electricity. this saves $200/year yet the capital
   costs of transforming sunlight into samelight should be no more than
   $500/kw ($2500 for a 5 m^2 heliostat--8'x8') and yearly costs should
   not exceed $40/kw of samelight, $50/5m^2 heliostat maintenance, and
   $150/5m^2 set aside for replacement.

   water heating

   samelight can be directed at a protected target that never freezes.
   samelight can be concentrated. samelight, unlike sunlight can easily
   be converted to extremely high temperatures, heat storage can be
   accomplished in smaller volumes than has been traditional in solar
   energy systems. for instance, with samelight we can cycle a cubic foot
   of rocks through 500 f which gives an energy storage of 500x200btu/f 
   = 10,000 btu/ft^3 or 3 kwh/ft^3 vs 1/5 this with sunlight.

   note that samelight can take on several entirely different tasks--as
   providing light when light is needed (light stands first in line since
   we cannot store light as we can store heat) and if light is not needed,
   a heliostat can be directed to a different target where samelight is
   converted to heat, electricity, cold, or mechanical power.

   electricity

   samelight can be converted to electricity with concentrating fresnel
   lenses using pv cells. these same cells can be cooled convectively with
   water or other liquid and the energy used as both electricity and light.
   no inconvenient outside, flexible coupling needed. samelight can power
   stirling engines to produce electricity. during unlight, gas or other
   fuel can kick in.

   refrigeration

   this is the perfect task for samelight. samelight can operate existing
   absorption refrigeration equipment. samelight is most abundant during
   times when refrigeration equipment is most needed and extra samelight
   can produce ice to store cool during times of unlight.

   a commodity

   the same heliostats can be used for all the above tasks. a heliostat
   can be moved from one building to another or one task to another. the
   heliostat, once many uses have become established is a commodity which
   will be manufactured, after a time, by several large and efficient
   manufacturers. 

   ten heliostats might be used one decade to pump ground water and then 
   during the next decade (after the well was pumped dry) the same
   heliostats could be used to refrigerate a motel.

   heliostats and samelight can be used extensively in space and on other
   planets as we colonize them. indeed, samelight and the uses we discover
   for it here on earth may be the crucial boost to give us confidence to
   get off our asses and out into space. some planets have no clouds and
   therefore abundant samelight. in space, samelight is as easy to have
   as sunlight.

   problems

   the great problem i see with samelight is fire hazard. it will be
   tempting to make concentrating heliostats that throw a beam of
   concentrated, lethally hot sunlight, rather than reflecting one sun
   to fixed concentrating targets. concentrating targets are inherently
   safe; no hot spot wanders about, but concentrating heliostats can
   easily wander and start fires. this hazard may be so great that even
   if a safe business is started using flat heliostats and concentrating
   targets the devices will soon be misused and the entire business
   brought into jeopardy and perhaps finally failure.

   first uses

   trivial uses may lead the way. the first heliostats may shine on
   north facing billboards.

   sameshine engineering

   civil engineering is much simplified by having gravity always work
   in the same direction. how could we construct buildings and canals
   and bridges if gravity changed its direction during the day?
   furniture toppling from one side of the room to another each day,
   objects sliding north and south with the seasons. naval and
   aeronautical engineers must face the problems the civil engineer
   avoids, for boats and planes pitch and roll. in solar engineering,
   no one has the luxury of the civil engineer. the sun never stands
   still; it moves all day and each day is different than the last.
   the solar engineer accepts these impossible circumstances because
   he knows nothing else. once the widespread introduction of
   heliostats produces a new branch of engineering of sameshine and
   samelight, these new engineers will marvel at how their predecessors
   grappled with the constantly turning sun. a race of sailors that
   never touched land would not even know to identify seasickness.
   samehine engineers will understand and forgive the previous
   problems of solar engineers--after all they had to deal with
   unceasing sun-sickness and did not even know it.

   some of the symptoms of engineering sun-sickness have been low
   temperatures, low efficiency, and high prices.

>with enough aluminum foil, you could place a roast in the window and have a
>fully cooked meal an hour or two later.

sure.

>along the alternate energy lines, how about illuminating your house
>with one of those little battery operated laser pointers?  they put out
>a bright light. just put a diffusing lens on the front and voila!

sounds dimmish.

>laser has gotta be more efficient than cf.

i'm not sure about that.

>you could put your house on wheels and move it to the south...
>oh, waitaminute, that's been done.

people who live on boats might make their houses face the sun all day with
a small automatic tracking winch and an ew line and a fixed anchor rode to
the south. good building land is becoming scarcer. a local house near a
creek is for sale for $19,900, a bargain if you don't mind floods :-)
why not build tracking houses on barges on shallow ponds in flood plains?

>if you live in a small house, chickpeas have a surprising amount of stored
>energy...

i think your bias is showing here, harry...

nick




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