Research on Multiple Energy-Saving Strategies for Existing Coach Stations: A Case of the Xi’an Area, China
Round 1
Reviewer 1 Report
Based on a careful analysis, I can formulate the following remarks:
1) The aim of this article, based on the authors’ scrupulous investigations, is to proposes energy-saving design strategies for coach stations in cold regions of China, including envelope structure renovation, the utilization of solar photovoltaic systems for power generation, and the installation of new air heat recovery devices to reduce building operational energy consumption.
2) The topic represents in my opinion a relevant approach of the proposed theme in the field, based on meticulous theoretical and investigations, correlated with experimental results.
3) In comparison with other published material, the authors' contribution adds to the subject area a new approach/methodology, with several significant contributions.
They performed a scrupulous a theoretical analysis, validated by meticulous experimental investigations for optimizing the large coach stations’ energy-consumption.
For the analyzed coach stations, through on-site investigations and field tests of indoor thermal environments in winter and summer seasons, the authors found that the coach stations had energy waste and high-energy consumption, the enclosure structures had poor thermal performance, and the stations lacked effective energy-saving measures.
They proposed a two-stage energy-saving transformation strategies, i.e., focused on the enclosure structures and renewable energy utilization.
By means of the DeST-C software for energy consumption, the external walls, roofs, insulation materials, and glass materials were simulated, and nine different combinations of energy-saving schemes were simulated using orthogonal experiments.
The optimal scheme was selected based on the comprehensive energy-saving rate and economic analysis results, which included using 80mm XPS external insulation for the external walls, low-e hollow glass for the windows (low transmittance type), and an 80mm PUR board for the roof insulation. Finally, the energy-saving rate of this scheme was 26.84%.
The use of rooftop solar photovoltaic power generation and fresh air heat-recovery devices can effectively reduce building energy consumption, and the investment payback period is less than 5 years.
The research results have practical significance for improving the indoor environment of coach stations and saving energy consumption.
4) With the continuous growth of the economy, China, as the world's largest energy 29 consumer, has naturally put energy conservation and pollution reduction work at the top 30 of its agenda. Its energy consumption is mainly concentrated in three areas: buildings, transportation, and industry. In this sense, the large transportation buildings represent one of their major objectives, because they generally have higher energy consumption levels than ordinary public buildings.
The highway transportation industry occupies a dominant position in the transportation system, with: a total mileage of high-ways over 5.1981 million kilometers, the annual passenger traffic of commercial passenger transportation had reached 6.894 billion people, accounting for 71.3% of the total passenger transportation traffic, and the passenger turnover of highways had reached 464.10 billion passenger-kilometers. Consequently, the number of coach stations is continuously increasing.
However, while the number and building area of coach stations continue to increase; their building energy consumption remains high. It is because most of them were built early and designed according to early energy-saving design specifications, with little consideration given to building energy conservation, resulting in poor thermal performance of the building envelope, poor quality if the indoor waiting environment, and high energy consumption of some buildings.
The energy consumption research on coach stations mainly focuses on establishing evaluation indicators and analyzing the important factors that affect energy consumption; while there has been less research on indoor thermal environment analysis and the energy-saving strategies of coach station buildings. There was identified and taken into consideration several influencing factors on the energy consumption of coach stations from four aspects: site selection, hardware configuration, building facilities, and layout technology.
As a major urban transportation hub, the coach station has increasingly high requirements for its indoor environmental quality and thermal performance of the envelope structure.
The authors, based on the selected coach stations, collected building information, passenger thermal comfort feedback, and indoor thermal environment testing through field investigations to analyze the existing problems. These stations are located in a cold region of China, with hot and rainy summers and cold and dry winters.
The analyzed coach stations are: all face the north–south direction; the waiting halls and ticket halls of the complexes are mostly 1-2 stories high; the operating hours are all more than 12 hours per day, and the annual passenger volumes are more than 500,000 people. In addition, the selection of heating and cooling equipment varies from station to station, but the main sources of energy consumption are electricity and water, and the end form of air conditioning is mostly a fan coil unit and fresh air system; they were erected between 1983 and 2013.
In their conceiving the energy saving and conservation, as well as the thermal performance of the building envelope structures no longer meet the requirements of current public building energy-saving design standards. Although the envelope structures and air conditioning systems have been renovated in subsequent operation processes, there are still problems, such as high energy consumption per unit area, low indoor thermal comfort, and low energy efficiency of the air conditioning and lighting systems.
The main factors affecting the energy consumption of coach station buildings are climate zoning, building age, enclosure structure status, building orientation, cold and heat source equipment, indoor personnel density, etc., while the reconstruction of existing coach station buildings is mostly envelope structure retrofitting, adding energy-saving measures, etc.
In response to these problems, and with the aim of reducing building energy consumption, combined with the geographical and meteorological environment of area, the authors analyzed the energy-saving strategy of bus passenger stations. They had taken into consideration the use of high-efficiency heat insulation materials for the building envelope to reduce heat loss, and the use solar photovoltaic power generation and fresh air heat recovery to reduce building power consumption.
Through the simulation of different thicknesses of exterior wall and roof insulation materials and building energy consumption under exterior window glass materials, they found that with an increase in the insulation material thickness, the energy-saving rate increased significantly, but the upward trend gradually tended to be flat.
The building energy consumption of different material combinations was calculated using DeST software. The energy-saving rate and net present value were combined, and the best enclosure structure combination was selected, that is, the external wall adopting 80mm XPS external insulation, the external window glass adopting low-e film-coated insulating glass (6 +9+6) (low permeability type), and using 80mm PUR board for the roof insulation. The energy-saving rate of this scheme is 26.84%.
The solar photovoltaic power generation system can effectively utilize the large-area roof space of the passenger station; this investment payback period was about 5...6 years.
Using a heat recovery device to pre-treat fresh air is also an effective measure to reduce energy consumption.
The energy-saving effect of using total heat recovery is better than sensible heat recovery, and its investment payback period is less than 3 years.
The obtained performances are very promising and I express my hope to continue their very interesting and useful theoretical and experimental researches.
5) In my opinion, the presented conclusions are suitable related to their research results and prove that they reached the proposed goal.
6) The references in my opinion are very appropriate and their number underlines the scrupulosity of the authors.
7) In this paper, the graphical illustration is well conceived and realized and consequently they contribute to a better understanding of the performed theoretical investigations as well as to underlining the experimental validation of the proposed methodology.
I encourage publishing in a new contribution their further results.
Author Response
Please see the attachment.Thank you!
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This paper describes a typical case study of energy performance analysis applied to an existing building, a coach station in this case, and a detailed analysis of possible measures for its improvement.
The paper is well written, arguments are clearly presented and they follow each other’s logically. Lack of novelty is the shortcoming of this work, since it is obvious that energy efficiency measures result in overall energy performances. However, authors included also the economic assessment, which is very useful to contextualize the work and put into prospective. In my view, this economic evaluation overcomes the shortcoming and make this paper a good work being comprehensive and informative.
I recommend to add a brief description of DeST-C software, the algorithm behind it and why it was chosen. In fact, results are obtained from this software and readers should have clear which are the limitations or advantages of this software.
Author Response
Please see the attachment.Thank you!
Author Response File: Author Response.pdf
Reviewer 3 Report
The review
The paper entitled " Research on Multiple Energy Saving Strategies for Existing 2 Coach Stations: A case of Xi'an area, China" presents a case study.
The paper includes interesting content, but a few things caught the reviewer's attention:
1. In the abstract, the authors write that coach stations have high energy consumption 8 and the indoor waiting environment is poor quality and it is the reason for the urgent energy-saving transformation. Such a sentence does not show the connection between these two factors. This should be specified.
2. Descriptions of drawings do not contain the necessary items, i.e. a description of the axes, units… In order to conduct a discussion on the results of the study, this must be changed.
3. One of the subchapters is entitled General situation of the coach station. It is necessary to specify what situations the authors have in mind (economic, energetic, historical,…?). If more than a few factors are described, I suggest writing i.e. description of the subject of study.
4. The description of figures 6 and 7 are the same: Three-dimensional building model drawing in DeST software. They do not relate to their content. It is necessary to describe what is in the drawings, not in which program they were made.
5. The study does not have much scientific value, but the results do not raise any major concerns. However, the method of data presentation and the discussion concerning them is very poor. This is a simple description of the conducted research and does not contain a clear research thread. This is a form of a report.
6. The conclusions of the study are quite general.
7. The content of the paper contains many grammatical and editing errors. English is poor. I propose to apply linguistic and editing proofreading.
I propose to consider publishing the paper after it has been rewritten, taking into account any comments indicated in the review.
The content of the paper contains many grammatical and editing errors. English is poor. I propose to apply linguistic and editing proofreading.
Author Response
Please see the attachment.Thank you!
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
All reviewer's comments have been addressed by the authors, it is suggested to publish the paper in the current version.
The text still has some minor typos, please read it carefully.
Author Response
Please see the attachment.Thank you for your valuable comment.
Author Response File: Author Response.pdf
