Assessment on Global Urban Photovoltaic Carrying Capacity and Adjustment of Photovoltaic Spatial Planning
Round 1
Reviewer 1 Report
The work is very interesting and could be accompanied by recommendations for energy policy measures to promote the use of renewable energies
Author Response
Response to Reviewer 1 Comments
Point 1: The work is very interesting and could be accompanied by recommendations for energy policy measures to promote the use of renewable energies.
Response 1: Thanks for your positive comments on this manuscript. We have improved some English expressions and reorganized the conclusion part. The spatial planning of solar PV should be transformed into a concept of carrying capacity, but such planning could not be simply discussed based on PVCC. The tentative methods of this manuscript are available but still needs to be connected with other planning elements (or detailed influence factors) to give both planners and policy-makers the ability to guide the feasible PV spatial planning in each hierarchy, for the time being and in the foreseeable future.
Reviewer 2 Report
- In methods, authors should be more explicit about factors influencing PVCC. for example: adding more factors for rooftop systems.
- Will authors think awareness of PVCC to the end user to help in good terms for policy makers.
Author Response
Response to Reviewer 2 Comments
Point 1: In methods, authors should be more explicit about factors influencing PVCC. For example: adding more factors for rooftop systems.
Response 1: Thanks very much for this constructive suggestion, and we do agree with this. It is necessary to take more detailed factors into account, such as the shadow, the roof slope and the building orientation, etc. But unfortunately, these more detailed factors have to be temporarily ignored, due to the research scale and purpose of this manuscript (and also the difficulty of data acquisition). The main purpose of this manuscript is to make a tentative discussion on how PVCC would affect the strategy determination of solar PV spatial planning in a range that from urban planning to national geospatial planning. Therefore, the geographical scope of this study is proposed as global wide. Considering the replication of these assessments on such geographical scope (worldwide), we only take six main factors into consideration in this study, each of which is supposed to make more significant impact on final PVCC result than the other detailed factors. But this is not to deny the influence of other factors. It is certainly necessary to take them into account into the future work of smaller geographical area (such as regional scale, provincial or state scale and urban scale) to determine the more accurate and feasible optimization strategies. These more detailed factors are temporarily ignored due to the scale and purpose of this study. However, they do have significant impacts on PVCC, but the impacts are relatively lower for such a research scale as global wide. In addition, the hypothetical restrict of the maximum area in roof solar PV is set at 39% only. Therefore, the neglect of ignoring these detailed factors might not significantly affect the assessment result.
Point 2: Will authors think awareness of PVCC to the end user to help in good terms for policy makers?
Response 2: Yes, we have added a new section of 4.4 and refined the conclusion part to illustrate this. The spatial planning of PV might not only be the planning of solar PV itself, the cognition of PV spatial planning needs to be transformed into a kind of urban or even national geographic spatial planning, in the progress of which solar PV utilization should be taken as an important planning element into consideration. The concept of PVCC described in this study established a link between the PV development anticipation and its close relationship to other spatial planning on the one hand, and make people think about PV utilization from a view of Resource and Environment Carrying Capacity on the other hand. Such carrying capacity may in turn become a valid intuitive concept for future PV spatial planning, providing analysis capabilities and methods, with which the spatial planners could make comparisons and decisions to plan future courses of action. At the very least, it is suggested that the framework in this study can be considered as a starting point, aiming to stimulate interdisciplinary discussions between renewable energy developers, urban planners and policy makers. Methods mentioned in this study may be still not precise or comprehensive enough to make implementable planning adjustments independently, after all, only six factors were fit into the comparison, but they do provide the logic to figure out optimal solutions in the process of PV spatial planning by analyzing PVCC distribution and comparing the beneficial effects from each optimization strategy. Therefore, we can conclude that these tentative methods are available but still needs to be connected with other planning elements (or detailed influence factors) to give both planners and policy-makers the ability to guide the feasible PV spatial planning in each hierarchy, for the time being and in the foreseeable future.
Reviewer 3 Report
Please find my comments in the file attached.
Comments for author File: 
Comments.pdf
Author Response
Response to Reviewer 3 Comments
Point 1: English need to be improved. Somewhere sentences are not clear.
Response 1: The manuscript has been proofread thoroughly to correct the English grammar and expressions.
Point 2: What is the basis or rationale for selecting influence factors of PVCC? A sentence should be written to highlight the selection basis.
Response 2: We have supplemented the selection basis of influencing factors of PVCC in section 2.2. The selection of influencing factors of PVCC mainly depends on the geographical scope to be researched. The main purpose of this manuscript is to make a tentative discussion on how PVCC would affect the strategy determination of solar PV spatial planning in a range that from urban planning to national geospatial planning. Therefore, the geographical scope of this study is proposed as global wide. Considering the replication of these assessments on such geographical scope (worldwide), we only take six main factors into consideration in this study, each of which is supposed to make more significant impact on final PVCC result than the other detailed factors. But this is not to deny the influence of other factors, such as the shadow, the roof slope, the building orientation, etc. It is certainly necessary to take these other factors into account into the future work of smaller geographical area (such as regional scale, provincial or state scale and urban scale) to determine the more accurate and feasible optimization strategies. These more detailed factors are temporarily ignored due to the scale and purpose of this study. However, they do have significant impacts on PVCC, but the impacts are relatively lower for such a research scale as global wide.
Point 3: Source of the data is missing for Table 2? A reference should be given at least in the caption.
Response 3: We have added a note following Table 2 to describe its data source. The data of this table are extracted from the global PVCC assessment results of this study, by calculating the average level of each urban scale, according to the scope of each sample country.
Point 4: Figure quality should be improved, especially Figure 1 and 4. The resolution is very poor.
Response 4: We have improved the quality of these two figures, but these improvements might not be discovered directly in the revised version, since the size limitation of the uploaded file, the resolution of the image will be compressed. Instead, we had packaged them into a zip file, which has been uploaded to the editorial office (in 2000 dpi). In addition, we also uploaded each image (by country) of Figure 4 so that they could be typeset more flexibly.
Point 5: Conclusion of the study very generic and does not provide clear description of the results. The key conclusions/insights derived from the authors’ analysis should be clearly mentioned.
Response 5: Thanks very much for this suggestion. We have added a new section of 4.4 and refined the conclusion part to clarify this. The spatial planning of PV might not only be the planning of solar PV itself, the cognition of PV spatial planning needs to be transformed into a kind of urban or even national geographic spatial planning, in the progress of which solar PV utilization should be taken as an important planning element into consideration.
Apparently, the current so called PV planning are still the continuation of previous cognition of ‘Power distribution and allocation’, in the working mode of which, the city (energy demand side) is still considered as the principal part of planning, and the power planning has to be adjusted passively with the change of urban energy demand. An inevitable result of this is that, still we have to make large scale of investment into building thousands miles of transmission lines, merely to deliver solar energy, the ubiquitous resource on earth, from one place to another. But actually, the main obstacle to the large-scale utilization of solar PV is more likely to be the inadaptability of existing spatial planning, such as population distribution, urban layout or industrial deployment. Therefore, the PV spatial planning proposed in this study is essentially a kind of urban planning or national geographic spatial planning, which could balance the relation between energy demand and supply, coordinated with regional (or urban) economy, resources, social structure and other comprehensive planning elements.
Such ‘PV spatial planning’ requires the active adjustment of urban (and national geographic) planning to adapt the needs of large-scale PV utilization in the future. But it is not meant that solar PV would become the dominant factor to determine the morphology or deployment of the city. Instead, it is just one factor related to many other planning elements (e.g., water resources, food, transportation capacity, natural disasters, ecological or historical protection, etc.). In addition, PV spatial planning does not deny any current attempt of optimization measures, but at least these measures need to be integrated into a hierarchical process to cope with the transformation of geographic and urban spatial planning. For instance: 1) At the very first hierarchy of national geospatial planning, it needs the reasonable deployment of urban location and population scale to reduce the gap of PVCC distribution and maximize the efficient use of local energy. 2）Through the assessment of regional solar irradiation, available land conditions and other planning elements, the function target and PV development anticipate of the city (or region) should be then formulated. 3) Furthermore, at the hierarchy of urban planning, it determines the scope of urban land use, building density control standards, building function layout and the optimization strategy of building morphology, etc. Compare the adjustment strategies of each planning hierarchy, to explore the most effective way to achieve the optimal utilization of solar PV energy. Of course, such ‘PV spatial planning’ is a kind of forward-thinking and might be regarded as a dispensable work for now, because, at least at present, the proportion of solar PV utilization is still at a low level, but with the rapid increasing utilization of renewable energy, such proactive adjustment of urban (or even geographic) spatial planning may be of great significance for achieving higher solar energy supply in the future.
The concept of PVCC described in this study established a link between the PV development anticipation and its close relationship to other spatial planning on the one hand, and make people think about PV utilization from a view of Resource and Environment Carrying Capacity on the other hand. Such carrying capacity may in turn become a valid intuitive concept for future PV spatial planning, providing analysis capabilities and methods, with which the spatial planners could make comparisons and decisions to plan future courses of action. The tentative methods in this manuscript are available but still needs to be connected with other planning elements (or detailed influence factors) to give both planners and policy-makers the ability to guide the feasible PV spatial planning in each hierarchy, for the time being and in the foreseeable future.
Reviewer 4 Report
The reviewed publication does not bring anything new to the subject of renewable energy sources. The proposed methodology is not entirely clear or too complicated. The results obtained are also predictable and do not say anything new on this topic. In denser urban buildings, energy consumption is higher, transmission losses will be lower and assembly areas will be limited (despite the large number of roofs), but they may be obscured by other buildings. In this version, in my opinion, the article is not suitable for publication.
Author Response
Response to Reviewer 4 Comments
Point 1: The reviewed publication does not bring anything new to the subject of renewable energy sources. The proposed methodology is not entirely clear or too complicated. The results obtained are also predictable and do not say anything new on this topic. In denser urban buildings, energy consumption is higher, transmission losses will be lower and assembly areas will be limited (despite the large number of roofs), but they may be obscured by other buildings. In this version, in my opinion, the article is not suitable for publication.
Response 2: Thanks for your comment, it is not doubt that ‘in denser urban buildings, energy consumption is higher, transmission losses will be lower and assembly areas will be limited (despite the large number of roofs), but they may be obscured by other buildings’. But the purpose of this manuscript is not about to improve the evaluation methods to derive a more accurate and convincing of solar PV potential. Instead, we were trying to get the assessment result by the simplest way-the utilization factor-to avoid the replication of this progress. The main purpose of this manuscript is about to make a tentative discussion on how PVCC would affect the strategy determination of solar PV spatial planning in a range that from urban planning to national geospatial planning. We therefore have added a new section of 4.4 and refined the conclusion part to clarify this. The current so called PV planning are still the continuation of previous cognition of ‘Power distribution and allocation’, in the working mode of which, the city (energy demand side) is still considered as the principal part of planning, and the power planning has to be adjusted passively with the change of urban energy demand. But actually, the main obstacle to the large-scale utilization of solar PV is more likely to be the inadaptability of existing spatial planning, such as population distribution, urban layout or industrial deployment. Therefore, the PV spatial planning proposed in this study is essentially a kind of urban planning or national geographic spatial planning, which could balance the relation between energy demand and supply, coordinated with regional (or urban) economy, resources, social structure and other comprehensive planning elements.
Such ‘PV spatial planning’ requires the active adjustment of urban (and national geographic) planning to adapt the needs of large-scale PV utilization in the future. But it is not meant that solar PV would become the dominant factor to determine the morphology or deployment of the city. Instead, it is just one factor related to many other planning elements (e.g., water resources, food, transportation capacity, natural disasters, ecological or historical protection, etc.). In addition, PV spatial planning does not deny any current attempt of optimization measures, but at least these measures need to be integrated into a hierarchical process to cope with the transformation of geographic and urban spatial planning. For instance: 1) At the very first hierarchy of national geospatial planning, it needs the reasonable deployment of urban location and population scale to reduce the gap of PVCC distribution and maximize the efficient use of local energy. 2）Through the assessment of regional solar irradiation, available land conditions and other planning elements, the function target and PV development anticipate of the city (or region) should be then formulated. 3) Furthermore, at the hierarchy of urban planning, it determines the scope of urban land use, building density control standards, building function layout and the optimization strategy of building morphology, etc. Compare the adjustment strategies of each planning hierarchy, to explore the most effective way to achieve the optimal utilization of solar PV energy. Of course, such ‘PV spatial planning’ is a kind of forward-thinking and might be regarded as a dispensable work for now, because, at least at present, the proportion of solar PV utilization is still at a low level, but with the rapid increasing utilization of renewable energy, such proactive adjustment of urban (or even geographic) spatial planning may be of great significance for achieving higher solar energy supply in the future.
The concept of PVCC described in this study established a link between the PV development anticipation and its close relationship to other spatial planning on the one hand, and make people think about PV utilization from a view of Resource and Environment Carrying Capacity on the other hand. Such carrying capacity may in turn become a valid intuitive concept for future PV spatial planning, providing analysis capabilities and methods, with which the spatial planners could make comparisons and decisions to plan future courses of action. At the very least, it is suggested that the framework in this study can be considered as a starting point, aiming to stimulate interdisciplinary discussions between renewable energy developers, urban planners and policy makers. Methods mentioned in this study may be still not precise or comprehensive enough to make implementable planning adjustments independently, after all, only six factors were fit into the comparison, but they do provide the logic to figure out optimal solutions in the process of PV spatial planning by analyzing PVCC distribution and comparing the beneficial effects from each optimization strategy.
Round 2
Reviewer 3 Report
Comments are adequately addressed and improvements are made in the manuscript.
Reviewer 4 Report
I would like to thank the authors for their extensive comment with explanations of the purpose of the work. However, in my opinion, their results still do not contribute much to the current topic of photovoltaics and the possibilities of its use. The proposed indicators are poorly described and are based on unclear principles, and the obtained results are not very different for different areas, so I do not know what importance they may have when making decisions about spatial planning in cities. The changes introduced in the text are minor, mainly editorial and linguistic, a slightly larger comment was added only in the conclusions.
