From: dpeders1@cc.swarthmore.edu (Daniel Pedersen)
Subject: Re: Energy Ideas -- Solar Power
Reply-To: dpeders1@cc.swarthmore.edu (Daniel Pedersen)
Organization: Swarthmore College
Date: Wed, 6 Jan 1993 22:22:24 GMT

stead@skadi.CSS.GOV (Richard Stead) writes:
> In article <1466300125@igc.apc.org>, ei@igc.apc.org (Essential Information) writes:
> > heat must be cooled by the air conditioning system.  Solar heating,
> > which uses heat from the outside of the building, does not add to
> > the interior cooling load.  Thus, avoided Heating, Ventilation, and
> 
> I don't agree with this.  It seems like well-designed solar systems
> are being compared to poorly-designed boiler systems.  A good boiler
> system would be well-insulated and properly vented so that it does
> not heat the building (unless that is desired).  I think solar
> heating for hot water would still probably beat the boiler, so
> there is no need to consider the HVAC costs.

That would depend on the location and the climatic conditions of your
application.  However, even with relatively low level solar radiation, you
can achieve competitive performance with a solar space and water heater.  In
climates with little sunlight in the winter (Scandinavia), seasonal storage
becomes a viable option.

I mostly agree with Richard about the HVAC costs, but the extra insulation
needed for the indoor boiler would increase the cost for that system.
However, if we're dealing with an existing conventional heating system which
we want to replace with a solar system, then we wouldn't need to account for
the extra insulation.

  One problem with
> solar hot water systems that isn't mentioned here, is the need to
> store the heat.  This has been done by melting certain substances
> (I think sodium sulfate decahydrate has been used, for example).
> By storing the heat, people can have hot water in the morning (when there
> is large demand).

One way of storing heat is in a hot water tank, or in a pebble bed (the
rocks store the heat).  The method you are describing is called phase change
storage, where the energy is stored in the phase change of the substance,
rather than the temperature difference.  Sodium Sulfate Decahydrate
(Glauber's salt) releases water when heated, which dissolves the salt.  When
it is cooled, it solidifies and absorbs the water in its solid phase.  The
most effective method that is widely used is water storage, since the heat
capacity of water is very large, and water is very cheap.

> 
> > WATER DISTILLATION AND PURIFICATION ACHIEVED WITH SOLAR POWER
> > 
> > Solar stills create a continuous gentle steaming of water which is
> > then trapped and allowed to condense. The conventional method,
> > boiling water and condensing it, requires eight gallons of water to
> > provide one gallon of purified water, while solar stills provide
> > one gallon of purified water from just over one gallon of water. 

Hey!!  Does anyone out there have any information or sources on this topic?
I posted a while back, and got some replies, but I'm still collecting
sources.  Specifically, does the person who posted this have the sources for
these figures?  PLease email me at the address below.


-->Daniel Pedersen  -  Keren's Daddy		(215)543-8961
	dpeders1@cc.swarthmore.edu	pedersen@engin.swarthmore.edu
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