I've never used or built a solar heater for the express purpose of
liquifying honey.  However, I was in the solar industry for awhile and
suggest that, while the project is certainly doable, controlling the
temperature will be harder than you might imagine.

A closed solar collector will reach temperatures well above boiling
(water) in no time flat.  Several factors will impinge on the temperatures
achieved inside the collector: angle to which the collector surface is
raised; size of the collector aperature; time of year (sun angle); cloud
cover; and probably most important for this problem, the amount of air
bled from the system to control the temperature.

The simplest system would be to put the honey in a non-reflective
container and leave it in the sun.  You would have no control whatever
over the temperatures achieved.  Convection would quickly begin since the
honey on the sun-facing surface would liquify first and begin to move.
Whether that movement would be sufficient to keep the honey temperature
near its melting point could be easily ascertained by installing a
recording thermometer on the sun side near the top of the container.
However, once the bulk of the honey in the container becomes liquid, the
temperature of all of the honey should rise fairly rapidly.

A solar collector in which a container of honey is placed (and shaded from
direct insolation) and which uses air as the medium with which to heat the
honey can be built inexpensively.  Even if the temperature of the air in
the box becomes much higher than the "safe" temperature of honey, I
_suspect_ the higher air temperature will not do much damage since the
amount of heat carried in the air is far less than the amount of heat
which honey is capable of absorbing.  However, until the honey liquifies
and begins to move (convection) or after the upper limit temperature
(100F-115F) has been achieved in the honey container, so long as there is
sun, the temperature of the honey will continue to rise.

Ideally, a air based collector for this purpose will have an unrestricted
source of air at the intake (bottom) and a thermostatically controlled
valve (louvre) at the top where the air temperature is sampled near the
honey container.  Once again, the reservoir of honey should not be in
direct sunlight.  The control should be set so that there is free flow of
air through the collector once the honey reaches the desired temperature.
The temperature of the air moving freely through the collector will be
only slightly higher than ambient air temperature.

The down side: if honey in a collector is not completely liquified during
the day and is left in the collector after the sun sets, cooling in the
collector will be rapid via radiation to the sky.  This phenomenon can be
controlled by covering the collector glass with an opaque material.

I should think the best solution would be to use a liquid collector (water
or glycol), a thermostatic control which keeps a water bath at the
terminal temperature desired, and a reservoir in which the sealed honey
containers can be submerged.  If the collector can be situated below the
reservoir, a thermosyphon will occur in a closed loop and no pump will be
required.  The construction cost of such a system could be considerable.
However, if built out of appropriate materials, it should have very low
maintenance and $0 operating costs.

In the long run, a water bath system should do the job more efficiently
than an air system.  Maybe I'll work on it.


On Sat, 10 Mar 2001, huestis wrote:

> Hi all,
>
> Since we are discussing liquefying honey would someone comment on using =
> solar honey melters?


---------------
Richard Yarnell, SHAMBLES WORKSHOPS | No gimmick we try, no "scientific"
Beavercreek, OR. Makers of fine     | fix we attempt, will save our planet
Wooden Canoes, The Stack(R) urban   | until we reduce the population. Let's
composter, Raw Honey                | leave our kids a decent place to live.