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1202Re: [hreg] Solar Air Conditioners

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  • Kevin L. Conlin
    Sep 1, 2001
      Hi Robert, I believe that the biggest reason the solar/absorption chillers
      don't work well with solar is the reason you stated, the high flow rate,
      plus most solar thermal water heaters are not very efficient in the
      temperature range these units need to run efficiently, typically around
      boiling, 200 degrees plus. Although evacuated tube absorbers can reach this
      range comfortably, they do not work well in Houston because of the
      relatively low insolation levels. A large array is required. When I was in
      the solar thermal business we did a feasibility to use solar AC at Moody
      Gardens. The evacuated tube solar array was huge, as were the insulated
      storage tanks, and the system was very expensive. Typically these
      absorption units are designed to run on low grade steam left over from
      manufacturing. I have seen large industrial systems like you mentioned that
      have been running for decades with little maintenance and few problems, so
      the technology is sound and proven, just not real compatible with most solar
      thermal technologies.

      To answer your earlier question, I believe the best prospect for splar AC is
      the combination of efficient/traditional/passive solar home design, a
      geothermal heat pump with a a ground loop. The reality is that if you build
      a good passive solar/energy efficient home with a high SEER AC/heating unit,
      your utility bills will be reasonable enough that a solar electric system is
      no longer needed, but certainly a lot more practical. A few texas
      architects, such as Mac Holder, Pliny Fisk, Laverne Williams and Bob Batho
      have mastered the Texas climate with these combinations and their homes use
      only a fraction of what your and my home use. As for builders getting it,
      forget it! These architects are laying the technical groundwork for future
      builders, not today's. As observed earlier, most are too stupid and greedy
      to care about the people actually living in their homes. Sorry for the long
      reply, but this topic sure has generated some interest. Best Regards,
      kevin
      ----- Original Message -----
      From: "Robert Johnston" <rjohnsto@...>
      To: <hreg@yahoogroups.com>
      Sent: Friday, August 31, 2001 8:58 PM
      Subject: RE: [hreg] Solar Air Conditioners


      > I hadn't noticed the weblinks in my quick read before.
      > Adsorption/absorption chillers
      > are not new. We have one in the building where I work. They are
      efficient
      > on an
      > industrial scale. I don't know what factors have kept them from scaling
      > down to
      > home use, but it would be interesting if they could.
      >
      > Actually, I suppose you could consider this a variant on the dessicant
      drier
      > tech
      > I mentioned, since silica after all is a dessicant.
      >
      > The Krum link is to Houston; anyone know these people? They appear just
      to
      > be
      > distributors, but maybe they might have some idea of the factors that
      limit
      > downsizing.
      >
      > These units are industrial size, of course. Wonder if scaledown is even
      > practical.
      > These units are 6' x 9' x 9' and the input hot water flow is around 10
      cubic
      > feet/min.
      > That is a little fast for most solar hot water heaters to produce! They
      > seem better
      > suited to cogeneration in industrial systems that generate heat.
      >
      > Anybody else have some thoughts on this?
      >
      > Robert
      >
      > -----Original Message-----
      > From: William M. Bell, Jr. [mailto:wmb@...]
      > Sent: Friday, August 31, 2001 6:50 PM
      > To: hreg@yahoogroups.com
      > Subject: Re: [hreg] Solar Air Conditioners
      >
      >
      > Robert:
      >
      > Thanks for the interest. I am not opposed to ammonia. It simply makes life
      a
      > little more complicated.
      >
      > I "designed" a system that used chilled water to cool and heated water to
      > heat. The main problem was that it required a rather large, insulated
      > holding tank. I proposed to use a concrete tank and bury it.
      >
      > I found a simpler design that used silica gel and water. It uses
      > solar-heated water to squeeze the water out of the silica gel. If you
      looked
      > at the web site that I listed, you can see a commercial application of
      such
      > a system. It has much going for it: few moving parts; no corrosive
      > chemicals; no excessive pressures or temperatures; and simple. The only
      > problem is that I can't find any residential applications and information
      is
      > scarce.
      >
      > Geothermal is cool, no pun intended. The main problem that I have
      > encountered is that it is expensive to drill several wells and there is
      also
      > a fear that you could contaminate your drinking water. That is geothermal
      > that uses water wells. I have also heard of geothermal that circulated
      water
      > through pipes located 10+ feet below ground. A friend of mine worked with
      a
      > company that uses directional drilling to dig the lines for fiber optic
      > cable and conduit. He thought that it would be an easy matter to use their
      > machine to drill the circulating lines. My biggest obstacle, is that I
      have
      > no idea how much line, etc that I would need. Lack of knowledge has
      stopped
      > me once again. My thought was that I could put a coil in my air
      conditioner
      > blower, before it got to the a/c coil, so that I could pre-cool my air.
      The
      > idea was that if it worked well enough, the a/c would not need to kick in.
      I
      > wanted to find a small circulating pump (again, I had no idea what size)
      and
      > have it run by a solar panel. The hotter it is outside, the more it pumps.
      I
      > have a friend in Lake Jackson who drilled several wells and used it to
      cool
      > his house. It worked OK for a while, but then he had problems with his
      > wells.
      >
      > Anyway, I think that this is an interesting area and we would all benefit
      > from sharing our knowledge.
      >
      > ----- Original Message -----
      > From: "Robert Johnston" <rjohnsto@...>
      > To: <hreg@yahoogroups.com>
      > Sent: Friday, August 31, 2001 6:14 PM
      > Subject: [hreg] Solar Air Conditioners
      >
      >
      > > Between the Nigerian Scams and the Environmental Spams, the good stuff
      is
      > > hard to find here! However, there wasn't much comment on this note from
      > > Billy Bell except Kevin pointing out the inefficiencies of
      thermoelectric
      > > cooling (especially if tied to a solar cell!).
      > >
      > > However, it is an extremely interesting question and one I'd love to see
      > > more discussion on. This is obviously one of the main barriers to this
      > area
      > > ever achieving the kind of renewable energy freedom that some other
      parts
      > of
      > > the country can do. The use of water as an evaporative coolant OK in
      > > Arizona but not Houston--too humid already! In any case, even in a
      closed
      > > system it wouldn't make a good medium for an efficient A/C.
      > >
      > > Anybody want to comment on what they think has the greatest potential in
      > our
      > > area?
      > > Things that come to mind for me (besides ceiling fans, insulation, etc.)
      > > are:
      > >
      > > 1. Dessicators. I know that natural gas fired units are now used for
      > > commercial buildings in some locations. I don't know if any efficient
      > solar
      > > units have been designed. But if you could dry out the air, that would
      > help
      > > a lot. And then you might even be able to put a little cool water back
      in
      > > as evaporative coolant as in Arizona.
      > >
      > > 2. Geothermal units. I'm puzzled why these haven't taken off, unless
      it
      > is
      > > their installation expense. Why are they so expensive? Are they not
      > good?
      > > A local A/C guy told me there are lots of problems with mold and odor in
      > the
      > > heat pump part of the installation. I don't know if that is true. He
      is
      > > death on heat pumps **period** for that reason, and prefers straight
      > A/C's.
      > > But there is still something appealing to me of trying to cool
      compressed
      > > gas with ground temperature rather than air temperature medium. I've
      seen
      > > some of the numbers posted on the web (very high S.E.E.R.), but there is
      a
      > > lot of hype by vendors. Since these aren't that popular, is it because
      > they
      > > don't work that well in practice, or is it just the cost of
      installation?
      > > What is the payback period in this area, then? These are some questions
      > I'd
      > > like to see discussed.
      > >
      > > As far as ammonia goes, Billy--I know it is not nice stuff, but it used
      to
      > > be used in refrigerators long ago, so with proper engineering I guess it
      > was
      > > managed OK. (Before my time, so I have no first hand experience). I
      also
      > > know that TDC put some ammonia cooling systems on a couple of new
      warden's
      > > homes at the prison farm south of Lake Jackson on the corner of
      > > FM2004/FM2611 and State Hwy 36. It is a duplex unit. The houses have
      > > optimally sloping roofs aimed towards the sun, and then on the rooftops
      > were
      > > solar collectors. They may have had solar hot water too--I don't
      > > recall--but I remember reading in the newspaper when they built them
      about
      > > their ammonia cooling systems. This would have been around 1981-85
      > > timeframe. I also know that the collectors are now gone, but I don't
      know
      > > why. It could just be that TDC didn't want to fuss with them--e.g., it
      > may
      > > have been environmentally "cool" (pun intended) to use solar on state
      > > institutions at that time, but the maintenance expense for handling such
      > an
      > > unusual system that was different than all the other onsite A/C's might
      > have
      > > caused rethinking of the project down the road. Or, it may be that the
      > > units just didn't hold up to use. I don't know, but I assume you could
      > find
      > > out more by asking around, or writing TDC.
      > >
      > > In any case, if any of you have some thoughts on the subject of solar or
      > > just more efficient air conditioning/cooling, why don't we see if we can
      > get
      > > a discussion going on this subject and enlighten ourselves?
      > >
      > > Robert Johnston
      > >
      > > -----Original Message-----
      > > From: William M. Bell, Jr. [mailto:wmb@...]
      > > Sent: Wednesday, August 29, 2001 9:23 AM
      > > To: hreg@yahoogroups.com
      > > Subject: Re: [hreg] Digest Number 281
      > >
      > >
      > > > Wow! What an email regarding the livestock industry and the whales.
      Who
      > > are
      > > > they from? tpwc---ENVIRO ALERT <envir_456@... doesn't do much
      for
      > > me.
      > > >
      > > > Steve Stelzer
      > >
      > > I thought that livestock produced methane, which was a renewable? Just
      > > Kidding ; ) Although I appreciate information of this sort, I am more
      > > concerned that this discussion group stays on target.
      > >
      > > By the way, I have been doing a great deal of looking around in my spare
      > > time (which is not much) at solar air conditioners. There a number of
      > > alternatives out there. It sounds strange until you view solar as an
      > energy
      > > source (heat). Most solar air conditioners work by a process called
      > > adsorption. An efficient, economical solar a/c system, that could be
      used
      > in
      > > residential cooling would be an important contribution to renewable
      > energy.
      > > Think of the amount of heat generated in this city by a/c and the amount
      > of
      > > electricity that is wasted producing this heat.
      > >
      > > The adsorption units that I have looked at use either ammonia
      > (refrigerant)
      > > and calcium chloride (absorber) (or some other chemical) or water and
      > silica
      > > gel. The water and silica gel seems most promising to me. Ammonia is too
      > > dangerous to have inside my house and it makes it difficult to work out
      a
      > > system in which I can keep it outside. Water, however, is safe and when
      it
      > > evaporates, absorbs a great deal of heat.
      > >
      > > There is also a solid state alternative that I have not had much
      > opportunity
      > > to explore. They use solid state refrigerators in small outdoor coolers.
      > > When you pass a 12V current through the diode, one side gets hot and the
      > > other side gets cool. Perhaps, we could use the hot side to pre-heat our
      > > water to the hot water heater and the cold side to chill water that
      could
      > be
      > > used to cool the house, if needed. The unit could be attached to solar
      > > panels that produce the 12V current. The hotter it is outside, the
      harder
      > > the unit works. I like that!
      > >
      > > Some helpful web sites: http://www.caddet-ee.org/nl_html/001_02.htm
      > > http://www.adsorptionchiller.com/
      > >
      > > Billy Bell
      > > PO Box 926
      > > Fulshear, Texas 77441-0926
      > >
      > > 713-439-1115 Telephone
      > > 281-346-0994 Fax
      > > wmb@...
      > >
      > >
      > >
      > >
      > >
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      > >
      > >
      > >
      > >
      > >
      > >
      > >
      > >
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      > >
      > >
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