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Technical
An
array of solar hot water panels is mounted on the roof of the kiln
or on an adjacent building. Water is pumped in a closed circuit
between the panels and the heat exchanger inside the kiln. Heat
is extracted from the water which then returns to the panel array
for re-heating.
The
circuit involves a "Day" and "Night" loop with a diverter valve
controlling the direction of the water flow according to the commands
of the Differential Temperature Controller. An auxiliary water heater
is incorporated in the circuit to "top up" the temperature if required.
In the standard format this is the indirect fired gas unit, but
any external heat source could be used. Most operators use gas to
bring the kiln to temperature where it is maintained by the solar
circuit with occasional top ups from the gas auxiliary.
The
kiln can be run as Solar only, Gas only or a combination of both.
A programmable microprocessor allows a full range of control options
where any kiln climate can be achieved. Humidity control is maintained
by a balance between venting and fogging. Remote monitoring and
control from a PC is optional, and the system is compatible with
moisture content based control programmes.
Construction
Our kilns are fully engineered structures of thermal panel, with
aluminium, stainless, galvanized, and epoxy coated components for
maximum life. The standard kilns are designed for W 41 wind speed
(150 k/hr) and higher ratings are applied where necessary. Thermal
efficiency and air sealing has been a major design objective with
all our kilns as we require them to be capable of operating on solar
heating alone if necessary.
Auxiliary
Heating
We have developed
a safe and economical system with minimal compliance cost and easy
accessibility. Our gas unit is externally mounted and flued, feeding
hot water to the heat exchanger inside the chamber. The heat exchanger
is designed to be coupled to a waste wood hot water system if desired,
replacing or supplementing the gas unit.
Operating Costs
These vary according
the timber charge and the kiln temperature required, but drying
25 mm air dry hardwood from 25% to 10% MC costs $2 - $4 per m3
for gas in Australia. (USD $1 - $2 per m3 )
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