34 Coronation Street
Bellingen NSW 2454
sales@solardry.com.au Phone: 61 2 6655 2100
Fax: 61 2 6655 2017
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  Solar Collectors on SG 100 Kilns
Solar Collectors on SG 100 Kilns

An array of solar hot water collectors is mounted on the roof of the solar kiln or on an adjacent building. Water is pumped in a closed circuit between the collectors and the heat exchanger inside the kiln. Heat is extracted from the water which then returns to the collector array for re-heating.

4 x SG 50 Kilns
4 x SG 50 Kilns

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.

Kilns can also be run using Solar heating alone if required. 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.


Our kilns are fully engineered structures of thermal panel, with aluminium and stainless components for maximum life, they are designed to suit specific site conditions.
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.
All kilns are supplied as complete pre-cut kits and don't require specialist construction techniques should clients wish to do their own building.
However SDA also offers a turnkey installation service.

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 $1.70 - $3.40 per m3 )

International Conversions

25mm =   1 inch
1 m3 =   424 board feet
timber =   lumber
kiln =   dry kiln
timber kiln =   lumber dry kiln
50-60 Degrees Celsius =   120-140 Degrees Fahrenheit
A$1 =   US$ 0.94 approx

Economic And Environmental Benefits

Greenhouse Gas

Current world concern with energy use and greenhouse gas emissions brings us to examine energy costs involved in drying lumber.

The most important difference between Solar Dryers Australia and other kiln manufacturers is that up to 80% of the heating energy to dry the timber in the kiln is derived from the sun.

This single factor represents a huge saving not only the running costs for the kiln but also a very significant saving in the amount of green house gas produced to dry the timber.

The savings are so significant that with our SG100 kiln the savings in the gas heating costs alone can pay for the outright cost of the kiln within 7 years*1 under favourable weather conditions*2.

Currently Solar Dryers Australia has around 100 solar kilns installed, representing the saving of over 3,500 tonnes of CO2 per year and saving its customers an average of AUD$1.2 million in gas costs per year*3. This is equivalent to taking 780 cars off the road*4 or 532 family houses off the electricity grid*5.
These figures of course will grow with the number kiln sales.

Buying a solar kiln will lock in operating costs for drying timber and reduce exposure to ever rising fuel costs.
Below is a graph showing the gas cost savings for one of our customers with 13 kilns with respect to rising LPG gas costs.

Gas Use Comparison between SDA kilns and traditional kilns for one of our major clients

*1 The payback period is based on 26 full charges of 100 m3 of timber being run through the SG100 kiln each year and a gas cost of $3.50 per m3 of timber for the Solar Dryers Kilns and $17.50 per m3 of timber for a conventional gas fired kiln (based on drying 25mm boards). These gas usage figures have been calculated from customer feedback and is an average, not a best case scenario for our solar kilns nor a worst case scenario for conventional gas kilns.
*2 Favourable weather conditions means a normal summer and winter for the east coast of Australia with allowable cloudy days. Once again our figures are based on an average year, not a best case scenario where all the days of the year are sunny.
*3 These combined gas cost savings are calculated on 26 full charges of timber being processed in our 30m3 and above kilns and 15 full charges being processed in our kilns that are smaller than 30m3. All calculations above are based on 25mm hardwood boards.
*4 The average CO2 emissions for a car has been calculated from the NACE (National Average Carbon Emissions) data supplied by the Australian Federal Chamber of Automotive Industries (www.fcai.com.au). We have used the 2007 average new car emission values for light vehicles (under 3.5 tonnes) which is 226.1 grams of CO2 per km driven. We used the widely excepted value for the average distance a car travels in one year which is 20,000km. This has provided us with a standard emission value for an average car of 4.522 tonnes per year.
*5 The average CO2 emission values for a family home is based on 17kWh per day or 6205kWh per year which relates to 6.63 tonnes of CO2 production.

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