Modeling Future Energy Demand and CO₂ Emissions of Passenger Cars in Indonesia at the Provincial Level

Round 1

Reviewer 1 Report

The paper presents a modelling approach to future energy demand and CO2 emissions from passenger cars in Indonesia. The study is methodological sound and based on a bottom-up approach, which is particularly suitable for regional studies as the one presented. The source of the data is from official statistics and updated. Based on these data and using the model, the validation phase shows very good performance in terms of deviation between model and observations. The proposed scenarios are based on the introduction of new efficient technologies for vehicles and policy instruments. Fuel economy is segmented by powertrain type (diesel, gasoline, PHEV) and engine capacity for gasoline vehicles. However, no distinction is made for other parameters largely affecting fuel economy such as injection type: port-fuel injection vs gasoline direct injection, vehicle segment or mass: SUVs, sedans, etc. This is an important lack of granularity of the methodology and it should be discussed. For what regards PHEVs and BEVs additional comments on how the electricity generation is planned to be close to 0 should be further detailed. I would suggest to further discuss an additional scenario foreseeing lower VKT and lower vehicles/person as a result of green incentives to meet GHG targets worldwide (Paris Agreement).

Other comments.

In general check carefully the references. For example reference 8 is cited as Tian Wu et al. whereas in the reference list only Wu.

In nomenclature section make sure to include all used acronym: for example the following are missing: BOE, BAFU, LCGC, ASIF

Line 39, remove the unnecessary dot "Dargay and. Gately".

Lines 51-53. Rephrase because the meaning is not clear (maybe "Previous studies have shown that transport energy demand can be projected through top-down models, however to determine the impact of technological change...")

Line 57. Add verb: "this study is conducted at the provincial level"

Line 57. "the study have contributions" --> "the study contributes"

Line 98: "The provincial GDPs are in constant prices" rephrase. The meaning is not understood.

Line 126. Use larger fonts in the diagram

Line 153. Use larger fonts in the diagram

Line 199. Check that the equation uses other symbols as those in the explanatory line of line 200

Line 465/467 avoid using print screen to improve readability.

Lines 549 to 559 shall be erased.

Include number of reference on line 561 (i.e., "1" is missing).

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript presents an interesting research on modelling energy demand and CO₂ emissions in Indonesia using a bottom-up approach. In my viewpoint, the novelty of the research relies on the modelling at the provincial level and analysis of disparities among provinces. I also think that the results of this research provide insights on how sustainability-related policies could be differentiated and implemented in the provinces with the attempt to reduce energy demand and carbon dioxide emissions related to passenger cars in the current largest emitting provinces and in the ones forecasted to be the largest emitters by 2050. I believe that the article and its conclusions will be of interest to readers in a wide range of fields, such as energy, climate change mitigation, transport and economics.

The context of the study area is well explained and useful to understand the results of the article, which are appropriately interpreted. The methodology (data collection and analysis) as well as the macro structure of the article are logical. The English language is appropriate and understandable (only minor punctuation mistakes).

I would suggest that few aspects are clarified, beside some small corrections. Below are my comments in a consecutive order following the structure of the article.

Abstract

Page 1, line 13. For clarity to the reader, it would be recommendable to add in parenthesis what is meant with car intensity (fuel economy) and activity (vehicle-km). Page 1, line 17. Typo. Double period after “bottom-up model”, please delete one period.

 

Introduction

Good section that explains the relevance of the study, and an adequate literature review is presented.

Page 2, line 55. Corrections of references in the text: Eom and Schipper [17], Ma et al. [18]… Ko et al. [20]… Page 2, line 61: It may be advisable to specify in the aim of the paper that the study refers to Indonesia. Page 2, line 63. “section 4 provides the conclusions” rather than “section 4 provide a conclusion”.

Methods

The methodology is explained in good detail and in a transparent manner, including data sources and assumptions.

Section 2.5 (pages 5-6). For the estimation of vehicle kilometres travelled (VKT), data sources for fuel costs are provided, but I could not find the source of the VKT data per province. Section 2.6 (page 6, line 178). Please see comments at the end referring to energy units. However, if the authors prefer to present the energy units in litres of gasoline equivalent (LGE), it is advisable to provide the heating values of diesel and biodiesel used to convert into LGE. Section 2.7 (page 6, lines 199-201). Equation to estimate the standard error: please note that the nomenclature in the equation is not consistent to the paragraph explaining the variables in the equation for data points and predicted values (E and E’ in the equation, while Ɣ and Ɣ’ in the paragraph). Section 2.8 (page 7, line 214-215). The statement of “fuel taxes are the right policy…” is quite strong, perhaps use “fuel taxes are an appropriate policy…” Section 2.8 (page 7, line 219). When referring to “develop sustainable transport”, is this statement related to public transport? Section 2.8b (page 7, lines 241-245). As mentioned by the authors, it is highly relevant that the emission factor of electricity in Indonesia is reduced from 224.4 kg CO₂/GJ to 100 kg CO₂/MWh by 2050 (please provide consistent units) based on the IEA Blue Map scenario. Are there governmental plans to decarbonise electricity generation to support this reduction, e.g. Renewable Energy Strategy? If some of these plans exist, it would be advisable to provide a reference in this section. If not, this could be further discussed in the results or in the conclusions as a policy recommendation. Section 2.8c (page 8, line 251). Please use elasticity factor, elasticity variable or just elasticity instead of the elasticity constant. The latter term is slightly confusing.

Results

Results are explained in good detail, including the rationale behind the results and the differences among provinces.

Section 3.1.6 (page 15, lines 371). The standard error for the national model is stated as 1.455.344. Should it be 1,455.344?  Section 3.2.2 (page 21, lines 475-477). The larger CO₂ emissions reduction of the technology scenario may be due not only to the penetration of PHEV and EV, but also to the decarbonisation of the electricity generation, which might be relevant to highlight. Section 3.2.2 (page 21, lines 478-481). Would “range anxiety” be a barrier to overcome the market penetration of EVs? Section 3.2.2 (page 22, line 502). 15.96% instead of 15,96%

Conclusions

Page 22, line 525. It is mentioned that tax regulation or the imposition of fuel tax should consider consuming purchasing power. Could the authors expand on how could this be achieved? Page 23, lines 530. What do the authors mean with “historical situations”?

 

General comments related to units

Throughout the document, it would be advisable to present the energy units using Joules or their multipliers (GJ or PJ) rather than millions of barrels of oil equivalent (BOE) or litres of gasoline equivalent (LGE). This would allow easy comparison with other countries. This recommendation also applies to tables and figures where energy units are presented, i.e. Tables 8 and 10, Figures 8a, 9a, 14a for the three scenarios, and 15a. It is important that authors mention the heating values. Please use “tonnes” to represent metric tonnes. The abbreviation “tons” could represent short tons in the U.S. system units. Please use consistent punctuation format for numbers, i.e. comma to separate thousands, and decimal point for separating integers and decimals. For example, Table 8 uses commas to separate thousands, while Table 10 uses the periods.

Author Response

Please see the attachment

Author Response File: Author Response.docx