Analysis on the Economic Feasibility of a Plant Factory Combined with Architectural Technology for Energy Performance Improvement
Round 1
Reviewer 1 Report
The work is interesting, particularly in today's reality with the world energy crisis and the search for alternative energy sources to support a green and ecological transition. In particular, we want to evaluate the effects of reducing energy consumption and the possibility of using the resulting savings to pay for the construction of greenhouses with different technology.
However, there are several methodological problems to be overcome for publication in the journal.
First of all, the comparison has to be made under the same environmental and spatial conditions, so that only the effect of the technology can be observed: are the greenhouses on the same plot of land? Are they exposed to the same external environmental conditions (exposure, location, etc.)?
For a correct economic assessment, other elements have to be taken into account:
- How does the level of strawberry production change in the 4 compared conditions?
- Do greenhouses with photovoltaic panels allow the same or a lower production? This certainly influences future entrepreneurial choices.
- The different investment (in amount) generates different depreciation costs and varies according to the assumed duration of the investment and the interest rate applied. Is this not evaluated?
- Do you consider the cost of insurance against damage caused by weather, fire, theft, machine breakdown, etc.?
- Have you or have you not considered the cost of installation?
- How is the solar energy produced treated, distributed? I believe that preparatory investments are necessary, as well as at least a connection to the electricity box outside the greenhouse (with batteries or is it given to the electricity company?). In short, the investments need to be better described in order to understand what they include.
- What is the installable power per unit of installed area and what is the annual production per unit of installed area?
- Are there public incentives to cover all or part of the investment?
- The literature is weak, a comparison would have shown a payback period of at least 10 years, before starting the payback period.
- The pay-back or return model you used is unclear. It looks like the pay-back method but it should be discounted and applied under the condition that the alternative investments have the same NPV (Present Value of Cash Flows Net of Investment) and IRR (Internal Rate of Return) but with the cash flows you only pay back the energy costs and not the initial investment. So you have to provide more elements for a scientific publication of acceptable level, also a literature support.
The literature is very limited and needs to be extensively reviewed.
Good work
Author Response
The work is interesting, particularly in today's reality with the world energy crisis and the search for alternative energy sources to support a green and ecological transition. In particular, we want to evaluate the effects of reducing energy consumption and the possibility of using the resulting savings to pay for the construction of greenhouses with different technology.
However, there are several methodological problems to be overcome for publication in the journal.
First of all, the comparison has to be made under the same environmental and spatial conditions, so that only the effect of the technology can be observed: are the greenhouses on the same plot of land? Are they exposed to the same external environmental conditions (exposure, location, etc.)?
à Thank you for your deep understanding and comments.
à I also agree with your comment about the same environmental conditions. Thus, I added the following sentence to Section 2.1-(1). “For the regional selection, DOE epw files of weather data in Gwangju Jeolla-do, which was located in the southwestern area of Korea where strawberries are widely cultivated, were used and this study assumed that four greenhouses followed the same environmental and spatial conditions (same ground and climate conditions, etc.)”
For a correct economic assessment, other elements have to be taken into account:
- How does the level of strawberry production change in the 4 compared conditions?
à The purpose of this paper is based on the economic analysis of the investment in architectural elements for energy saving when the strawberry conditions were the same. Thus, the design was made under the assumption that there are no significant differences in proper illumination in the daytime, light saturation point, daylight time, and day and night setting temperature as much as possible as the condition to have the same productivity of strawberries. In case the energy-saving elements have economic benefits in our analysis, we think another paper on the verification of strawberry productivity will be needed.
- Do greenhouses with photovoltaic panels allow the same or a lower production? This certainly influences future entrepreneurial choices.
àAs mentioned above, the minimum essential conditions (proper illumination, light saturation point, daylight time, and day and night setting temperature) for plant growth are added to the simulation conditions as presented in Table 1. Accordingly, we assumed that they are the same according to the essential plant growth conditions.
à “These conditions satisfied the minimum conditions for strawberries to grow and the strawberry productivity is the same in our assumption as the purpose of this paper was an economic analysis according to the building energy-saving elements.” which are added to Section 2.1-1.
- The different investment (in amount) generates different depreciation costs and varies according to the assumed duration of the investment and the interest rate applied. Is this not evaluated?
à Section 3.3 has been completely revised and supplemented for economic analysis.
- Do you consider the cost of insurance against damage caused by weather, fire, theft, machine breakdown, etc.?
à Section 3.3 has been completely revised and supplemented for economic analysis.
- Have you or have you not considered the cost of installation?
à The installation cost is included in all construction expenses, which is mentioned in Section 3.1.
- How is the solar energy produced treated, distributed? I believe that preparatory investments are necessary, as well as at least a connection to the electricity box outside the greenhouse (with batteries or is it given to the electricity company?). In short, the investments need to be better described in order to understand what they include.
à The power circumstance in Korea has a high population density in terms of the site. Thus, except for some islands whose population density is very low, most power is provided by the KEPCO, and all costs for electricity installation for agricultural facilities are borne by the KEPCO.
- What is the installable power per unit of installed area and what is the annual production per unit of installed area?
à The annual production is derived in the result in Figure 4.
- Are there public incentives to cover all or part of the investment?
àThe Korea Energy Agency (KEA) supports the project of solar power in rural areas and the KEA provided the fund for the investment cost with a 1.75% of interest rate. We expect that the result of this study will change the current direct tax-free fuel support into electricity in the rural areas in line with the zero-carbon goals, resulting in a shift into the indirect carbon emission items.
- The literature is weak, a comparison would have shown a payback period of at least 10 years, before starting the payback period.
- The pay-back or return model you used is unclear. It looks like the pay-back method but it should be discounted and applied under the condition that the alternative investments have the same NPV (Present Value of Cash Flows Net of Investment) and IRR (Internal Rate of Return) but with the cash flows you only pay back the energy costs and not the initial investment. So you have to provide more elements for a scientific publication of acceptable level, also a literature support.
à As you suggested, we performed the analysis in Section 3.3 using the discounted payback period based on the case-by-case installation cost and energy expense, changing from a simple comparison of the installation cost compared to the energy usage.
Thank you for your deep understanding and comments.
please see the attachment.
Author Response File: 
Author Response.doc
Reviewer 2 Report
The paper complies with the requirements of the journal in terms of subject matter
The literature review process lacks broader comparative data on the direction of greenhouse crop process development due to energy demands.
Comparative literature is also lacking regarding the extent of assessment of CO2 emissions at the level of component products required to produce plant factories (carbon footprint).
The study did not include a literature review on the feasibility of using biomass for energy purposes with a reduced carbon footprint
The methodology did not include the exact climatic parameters affecting winter energy demand rates. The full cycle of temperature changes and their effects on heating losses and summer energy demand for the Korean study area were not considered. The authors draw attention to this factor in the conclusions.
In the conclusions, unnecessary repetition in lines 234-238 of information about the research methodology.
In the description of GHG, the description of the unit kt:(kt CO2 eq.) is missing.
A valuable paper for revision after corrections and supplementing the introduction with elements of literature review.
Author Response
Thank you for your deep understanding and comments.
please see the attachment
Author Response File: Author Response.doc
Round 2
Reviewer 1 Report
The paper has now improved and can be published Congratulations on the work done
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
In this manuscript, economic analysis was considered for typical greenhouse and plant factory, it was interesting.
However, the title didn’t clearly show the importance of this study.
The structure of the whole manuscript was not well and logically organized.
The term of greenhouse and plant factory was mixed together.
The case selected is not common and has little guideless for the production and plant factory construction.
The equations were not given that how the primary energy consumption and the related CO2 emission were calculated.
The figures’ quality should be improved to match the journal.
Reviewer 2 Report
This is an interesting experiment to compare four different greenhouse configurations to evaluate the energy consumption and CO2 emissions. Following comments and suggestions for authors' consideration.
- Are these set temperatures (daytime and nighttime) in Table 1 for the heating activation? It would be good to specify it clearly
- In Table 2, Is Case 1 (the Control) the most widely used strawberry cultivation configuration in South Korea? It might be good to mention it in the research design section; also Should it be more specific indicating "no artificial lighting" under "Lighting type and quantity heading?
- According to Figure 3, it is obvious that PV panel installed in Case 2 and Case 4 have surplus energy production to fulfill the required energy for heating and lighting. However, it is all depending on the establishment cost and how the benefit generated in terms of the fruit production. Based on the summary figures in Table 5, there's little difference in the recovery periods among Case 2, Case 3 and Case 4. The question is whether farmers are willing to spend significant investment up the front for PV panel installation (as indicated in Case 4); it would be ideal to compare the cost and energy consumption with the fruit production and quality in the future study
