John J Todd - Eco-Energy Options Pty Ltd and Michael Greenwood - AHHA Testing Laboratory
Department of the Environment and Heritage, June 2006
This research was commissioned by the Commonwealth Department of Environment and Heritage to investigate the proposed changes to the Australian and New Zealand Standard for the measurement of particulate emissions from wood-burning residential heating appliances (AS/NZS4013).
Emission measurements were made on four models of woodheater. The tests were conducted at the Australian Home Heating Association Laboratory in Adelaide, South Australia between 14 February and 22 April 2005. Emissions were measured for 108 test cycles, including tests conducted to (a) the AS/NZS4013 methodology, (b) the proposed revised methodology and (c) a new real-world protocol methodology. Two of the heater models were modified after initial testing by fitting an automatic air supply triggered by opening the fuel loading door and closed over a predetermined period by a timing device.
The proposed revised method differs from the AS/NZS4013 method for medium and low burn-rates in that only two minutes is allowed between adding a new fuel load and turning the combustion air to the medium or low setting (compared to 10 to 20 minutes delay in the AS/NZS4013 method).
The key outcomes of the research were:
- All four heaters recorded increased emission factors when tested to the revised method. For two heaters the emission factor doubled and for two heaters it tripled. This strongly supports the assumption that the revised test method is more stringent than the current test method.
- One of the four heaters achieved emission factors less than 4g/kg for both the AS/NZS4013 method and the revised method. The other three heaters 'failed' the revised method.
- The one heater that passed when tested to the revised method had a low emission factor when tested to AS/NZS4013 (1.8g/kg). This suggests that some heaters already on the market would meet the 4g/kg limit without modification. It also suggests that some heater models could easily be modified to pass when tested to the revised method, simply by increasing the minimum air supply. There is some evidence to suggest that heaters with smaller fireboxes would be more likely to respond to this type of modification.
- Two of the three heaters that failed the revised method were modified by adding an automatic additional air supply. After modification they both achieved emission factors less than 4g/kg when tested to the revised method.
- This research did not attempt to modify the two heaters for commercial production. The aim was to demonstrate that a simple and inexpensive solution is possible. Commercial modifications would need to be robust and aesthetically acceptable. There is no reason to suspect that this is not possible, although it is unlikely that a simple add-on device would be practical (i.e. some redesign/retooling would be required).
- The modifications used in this research focussed on a door-triggered timing device. Other possibilities are briefly discussed in the report, including temperature triggered systems and improved secondary air systems.
- Automatic controls open up new possibilities for reducing emissions and improving efficiency.
- A new emission test method was developed and trialled as part of this research. Referred to as the 'real-world protocol', the method includes measurement of emissions during the light-up phase as well as high, medium and low burn-cycles. After the light-up phase, larger logs are used (i.e. considerably larger than those specified in AS/NZS4013) and a larger total fuel load is used for the low burn. The operation of the heater is intended to more closely reflect use in people's homes.
- Emission factors for the real-world protocol, when averaged over all four heaters, were the same as the four-heater average for the revised method. Both were 2.5 times larger than the four-heater average for the AS/NZS4013 test method. However, the ranking of the four heaters from cleanest to smokiest altered for each of the three methods.