Fuel-Operated Auxiliary Heaters Are a Major Additional Source of Vehicular Particulate Emissions in Cold Regions
, Markus Nikka 2, Miska Olin 1, Sampsa Martikainen 1, Antti Rostedt 1, Anssi Arffman 2 and Santtu Mikkonen 3,4,*Round 1
Reviewer 1 Report
This Brief Report showed that Fuel operated auxiliary heaters (AHs) can be noteworthy sources of particle emissions. It is a potential issue to understand more details about it and to reduce the pollution.
Author Response
We thank the reviewer for understanding the value of our work and for the positive recommendation.
Reviewer 2 Report
This brief report looks at the use of auxiliary heaters and their effect on emissions, namely particulate matter. Although AHs are mainly used in nations with colder climates, the authors suggest that their relatively effect is quite high. A well written brief report and interesting read.
Please see my comments [line by line]
14: contributionS to .. and even THE global emissionS budget.
19:This raises THE ...
21: correct this, as it is not a proper sentence
22: More research ..
23: AHs
28: Two major ...
29: THE acceleration
31: to cause APPROXMATELY 8.9 million
37: aerosolS
39: {q} is it ageing state or state of ageing (not sure about wording here?)
43: {q} is it reduced to the UNDER the detection limit? Is that what you mean?
54: {q} I am not sure what you mean here about the long soak?
62: {q} Why don't more AHs use power from the grid? Is so, wouldn't this be great for emissions?
73-74: where is your reference?
77-78: not sure what you actually mean in this sentence, can you re-word it?
88: A fleet ...
89: from daily use FOR the experiments...
91: combusting THE same fuel...
92-94: Did you get the petrol from the same station? I know that the fuels vary from station to station (even if using gasoline, not all gasoline is equal). Not sure how much of an effect that could have?
95: Similarly, I would think that a vehicle 0 years old would have significantly lower emissions that a 19 year wagon! Also, the replaced parts may have additional effect.
97 ...but otherwise, according to our knowledge, all ...
100-101: what was your rationale for selecting a speed of 60km/h?
102-103: ...activate THE AH manually. Instead, the ...
104: below THE threshold ...
109-110: similar TO that WHICH will ...
111: Why are you comparing to the standards in the Netherlands? I thought the study was done in Finland?
122 and other parts... use the correct symbol for degrees C!
WHAT IS THE PURPORSE OF DILUTED VS UNDILUTED SAMPLING?
158: In Fig 2, A time series OF examples ...
Figure 2 - This is a nice figure. However, why don't you add a third panel for your Skoda Octavia 1.0 hybrid? It would be nice to see that for comparison purposes!!!
The CPC and ePNC look similar for the Alhambra but not the Octavia 2.0, why?
Suggestion add {gasoline} and {diesel} in brackets beside each vehicle and also {hybrid} if you add that.
Figure 3 - The arrow on your figure is not in the correct place.
215-216: driving. However, this ...
219: ... raises THE question .. on their HIGH emissions.
221: take A stand on ..
223: heaters.
Overall, a well done and interesting study!
Author Response
Please find the point-by-point answers to reviewer 2 in the attached pdf.
Author Response File: 
Author Response.pdf
Reviewer 3 Report
- I think the assumptions here are a little off. I believe the vehicle engine is used as the auxiliary heater after the car engine has warmed up, some heaters may not even blow air into the cabin till the engine is warmed up. Additional warm-up time is needed when the ambient temperatures are lower. The current MOVES emission formulation accounts for the cold start emissions, to essentially “warm up” the engine. This is a known/measured emission and accounted for in the cold starts of engines.
- The research here does nothing to account for when the vehicle is in-motion, which as stated above the engine temperature is used to heat the vehicle cabin, thus not significantly increasing the energy demand on the engine. I believe the air conditioner is a larger consumer of energy in a vehicle, this is because while air can be warmed by the engine temperature, it cannot be cooled in the same way, additional energy is needed to cool the vehicle cabin air, thus the reason why models such as MOVES and HERMES account for the air conditioning explicitly, but not the heater.
- If this auxiliary heater is fuel-powered, requiring more energy from the vehicles engine, this additional energy demand is analogous to the air conditioning adjustments currently in MOVES and other emissions models such as HERMES. The MOVES team at U.S. EPA has done significant work on PM emissions for winter vs. summer with ambient temperatures differences, for example:
- Nam, E., 2008. Analysis of particulate matter emissions from light-duty gasoline vehicles in Kansas City. US Environmental Protection Agency.
- Was there any consideration to the ambient temperature where the vehicle was tested? Many heating/cooling systems rely on temperature differential, so ambient temperature can affect the overall emissions and power demand from the vehicles engine. Would also be nice to know the cabin temperature (and cabin size) through the measurements.
- It would be nice if inferences from this data could be used to estimate the impact of the results, organization could help the reader understand the overall goal of the measurements better. The vehicles in Table 1 are sorted by Fuel then registration year, although the gasoline is sorted newest to oldest, and diesel is sorted oldest to newest. This organization seems odd.
- Table 1 says “mild hybrid”, what does that mean? FIGURE 2 has the measurements for the hybrid Skoda Octavia, as the only hybrid studied, I question why use it here to compare with a diesel vehicle (Seat Alhambra)? This hybrid engine does change energy demands/priorities for the vehicle, so this is almost a “3rd class” of vehicles, potentially representing a step toward the “electrification” the authors elude to in multiple places.
- Figure 2. I do not understand what the blue highlighted areas (possibly plateau) are representing. Please clarify in both panels the different “phases” of the test, such as turn-off. Figure 2 needs more explanation in general, labeling these plots could help significantly.
- Figure 3 is hard to read. It contains a lot of information, but it is all small. I would suggest changing this figure, potentially have bars vertical, then break up the plot into the different vehicles/fuels or heater modes. Or potentially a table would be more impactful here.
- The general conclusion, that heaters add to the emissions of vehicles when idling is contradicted in Figure 3 for the BMW530d vehicle. Can the authors expand on this?
- Figure 3 suggests that the VW Sharan has no emissions when idle. Can this be correct? There appears to be a read “X” in the figure, this is not explained.
- I believe the overall conclusions are a stretch. It is unclear to the reader that these conclusions are backed up by the data/figures/tables. This data is valuable, but the lack of clarity in the presentation leave the reader underwhelmed.
Author Response
We thank the reviewer on the helpful comments making our manuscript stronger. Please find the point-by-point answer to review in the attached pdf.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
see attached
Comments for author File: Comments.pdf
Author Response
We thank the reviewer on helpful comments improving our manuscript. Please find the point-by-point answer in the attached pdf.
Author Response File: Author Response.pdf
