# 197

Dear Mai Mohamed, Asmaa Elsayed

I read your paper

Evaluation of Renewable Energy Sources for a Sustainable Future: A Multi-Criteria Decision-Making Approach

My comments:

1- Page 2 you say “Wind energy is a clean, renewable source with a relatively low environmental impact during operation”

Yes, it provides clean energy during operation, but from the environmental point of view it also produces hundred of thousands of bird deaths, noise, and at the end of their useful life, the enormous blades must be buried in land fields, because at present there are not further uses for them.

In addition, their load factor may be very variable with the corresponding generation variability. They can work day and night provided that wind is blowing between a range of force, and of course, this is not guaranteed. They are very expensive and capital intensive., are more efficient than photovoltaic (PV) and demanding much less land for the same output than PV

2- Page 5 “This method is advantageous for its ability to emphasize the relative importance of criteria by considering both the absolute and relative differences in criteria values “

Relative criteria values are useful to rank criteria importance and producing trade-offs, useful in compensation methods. Criteria values are useless to evaluate alternatives, berceuse they consider a criterion as the envelop of a series of performance values.

This is irrelevant for alternatives evaluation because it depends on discrimination of these performance values, within the envelope. There is a theorem on this (Shannon). Therefore, the LOPCOW method does not appear to be very useful

3- I would like to know how the MAIRCA method can compare obtained alternatives evaluations with an ideal. TOPSIS uses a similar procedure but using inputted real data.

4- Page 6 “of T2NN [43] In the context of T2NN, linguistic values are used to express subjective assessments or evaluations in decision-making processes. These linguistic values are used to capture the uncertainty”

Therefore, you apply a method with very high subjectivity. How could it be compared with a real-life scenario? Another team of experts could reach different values? Which is correct, the first team or the second?

5- In page 9 you detail the different criteria. Do you really believe that with only five criteria you can evaluate a complex problem like this? I would have added many more like:

· Load factor for wind and PV that depends on many factors

· Relation of wind and PV to wind force, due to over high force wind

· An ancillary work is to construct steel towers for wind turbines, maintenance, loss of energy when the wind passes through rows, of turbines in rows

· Material and environmental cost for dismantling towers at the end of their life

· Possibility of towers and PV sharing available land

· Nearness of constructions or natural mountains that decrease the wind force

· Cost of transportation of blades 100 metres long,

· Wind stability and continuity, etc.

Regarding PV. Depending on:

· Latitude

· Weather

· Max air temperature

· Humidity

· Cost of metal structure

· Cost of cells

· Cost installation

· Environmental contamination, etc.

Same for other alternatives

6- Page 5 “Evaluating renewable energy options requires a comprehensive approach considering environmental, economic, and social factors. However, integrating these diverse perspectives into a cohesive decision-making framework is a significant challenge. One of the main hurdles is coordinating and managing collaboration among experts from different fields

I am 100% in agreement with you. It is interesting what you say in the second d paragraph when speaking about integration. This is exactly the same I say further in my comment. Does your method do it? Apparently not

The third paragraph is still more important and it is something that I have pointed out many times in RG, i.e. how to coordinate the opinions on certain aspects, for instance, between a geologist and an environmental guy, or an engineer and a financial guy? They talk different languages

7- Page 11. You solve a problem and find a ranking of Wind > Geo > Hydro > PV

I also solve this problem using SIMUS method and got: PV > Geo > Wind > Hydro

Your Qi value gives the importance of each alternative and therefore, it is equivalent to the score used in most MCDM methods to quantify the importance of each alternative.

The only difference is that for you the smaller the Qi corresponds to the best a;ternative ,while in general in MCDM the larger the sc ore the better, but of course both are valid

Both rankings are different. Let me tell you something; SIMUS does not use any weights or subjectivity. It is based on Linear Programming (LP) that follows the Simplex algorithm with results guaranteed by a very well-known theorem. Consequently, there is a big chance that its results are correct. This, naturally has no relation with the quality of your procedure and SIMUS. No comparison is made

I perform a sensitivity analysis on both the best alternatives that is Wind in your case and PV in my case.

Both solutions coincide in proving that both solutions are very strong, yours better than mine, in the sense that your shows that criteria have a wider leeway for incr4easing the important criteria., which is a good measure of strength for an alternative.

However, both first alternatives were tested using sensitivity analysis b y SIMUS, which is not really the case here.

Now, look at the scores for each alternative in each case:

SIMUS: 0.51>0.5 >0.32 > 0.20, or PV>Geo>Wind> Hydro

T2NN and

TOPSIS: 0.09> 0.19 >0.13 > 0.19, or Wind>Geo>Hydro>PV

Examining SIMUS result and investigating rationally about this ranking we have these comments from reputed sources

a) ENERDATA-In 2023, global renewable installation reached new records, with 349 GW of new solar capacity (twice the 2022 installations) and 113 GW of new wind capacity.

b- Artificial Intelligence asked about PV vs Wind -Solar PV

Answer: Growth: Solar PV generation has grown rapidly in recent years, especially in China, the United States, the European Union, and India.

c- International Energy Agency (IEA)- Solar PV generation increased by a record 270 TWh (up 26%) in 2022, reaching almost 1 300 TWh. It demonstrated the largest absolute generation growth of all renewable technologies in 2022, surpassing wind for the first time in history. Solar PV generation increased by a record 270 TWh (up 26%) in 2022, reaching almost 1 300 TWh. https://www.iea.org/energy-system/renewables/solar-pv.

I strongly suggest to look curves in Figure “Share of renewable electricity generation by technology, 2000-2030”

Why this sharp difference between SIMUS and 2TNN-MAIRCA, when the latter puts PV in the last place?

Hard to say, however, in my opinion, it is due that SIMUS is the only MCDM method that works considering simultaneously all criteria and all alternatives, that is, considering the initial matrix as the mathematical representation of a system, and in so doing taking into account all the possible interrelationships. I remind that TOPSIS and all MCDM methods (except LP),work considering criterion by criterion.

Since SIMUS does not use weights, it clearly shows that weights do not play any function in alternatives evaluation.

Nonetheless, wind surpasses PV in efficiency and land use and even in cost per MWh produced, but the environment must pay a high price for having blades buried and the end of their life

At present, many laboratories around the world are working on organic photovoltaic cells, (OPV), that if successful will decrees drastically PV cost, contamination, structure, etc.

Coming back to your Qi values. The difference between wind and PV is 0.19 – 0.09 = 0.10

This means that there is a 111% de difference regarding the wind value. This is highly uncredible. since even when wind has some important advantages over wind, in cost, efficiency and land used than PV, these advantages in no case surpass the 100%.

If it were the case, how it can be justified, when according to ENERDATA, installation in 2023 in PV is more that 200% higher than wind? If you consider the percentage of difference between wind and PV in SIMUS, you can verify that this percentage is 44%

These are my comments, hoping that they can help

Nolberto Munier