# 201

Dear Godswill Osuma and, Nadia Yusuf

I read your paper

Towards an Optimal Renewable Energy Mix for the European Union: Enhancing Energy Security and Sustainability

My comments:

1- I have read the full paper and I am impressed for the richness of the references but fundamentally, because the paper states very clearly what is obvious, but if my memory serves me well, I have only seen it in this paper and in another one.

It refers to the need of considering a problem holistically, that is, simultaneously with all criteria and alternatives, and that the paper illustrates so well. It is something that I have been preaching in loud voice along many years in Research Gate. However, people continue using MCDM methods that do not adhere to this basic requirement, and analyze each criterion separately and then add up the values of each one, apparently not realizing that real-life projects are not the same as blackboard examples used in university classes teaching MCDM, without realizing that a final result is normally not equal that the addition of the parts.

Practitioners are not to be blamed, but the methods, that do not consider that the initial decision matrix is a system, and as that, criteria are not independent but normally highly related. There are more than 200 different MCDM methods, but only one of them allows to perform this system analysis: ‘Linear Programming’ (Kantorovich,1939), (Dantzig, 1948), by considering the problem holistically. This development was so important that Kantorovich was awarded the 1956 Nobel Prize on Economics.

This paper is so full of truths that for me is a pleasure to recommend its reading

2- However, I am not in agreement with the authors that wind energy will be the renewable for the future, at least partially. The authors do not consider some issues as the load factor of both systems, that is the ratio between energy actually generated in one year and the energy that could be generated.

The reason is simple, photovoltaic cells need solar irradiation that in part, depends on the latitude of each site, and also exists, even with cloudy days, between certain hours, probable since 9 in the morning to perhaps 17.00 hours. In that interval the sun irradiation is maximal and obviously there is none before dawn and after sunset.

Wind energy depends on wind force between certain limits, and if wind is blowing, generation can take place day and night. But what happens if the wind is not blowing? Generation is zero.

In this aspect, PV has the advantage that in a certain interval these is always guaranty of generation that can be expanded up to midnight, by using another system of sun radiation called PV Thermal, where radiation is used to heat water at very high temperature and stored, which permits generation until about midnight. In addition, there are laboratories that are working in using organic PV or (OPV), at a very reduced cost and even cells using another not contaminant minerals.

Another disadvantage of wind is environmental, since the blades made with resins do not have any further use and must be buried in land fields.

3- Page 14 “The future of the region’s energy security will depend on the EU’s ability to maintain a balanced and resilient energy mix. “By combining the integration of renewables with a strategic phase-outof fossil fuels, the EU can potentially meet its environmental objectives”:

This is so important a subject that cannot be reduced to a simple comment of mine. Please allow me to extend on this matter.

These is a very good point, and the main word is ‘balanced‘, that can be only achieved by a holistic analysis. The bold word is, according to my opinion, the only way to achieve zero emissions by 2050 and ‘phase-out’ is the key word.

The balance is obtained combining the construction of renewable generation units, taken into account forecasted increases of energy demand, and, at the same time phasing-out progressively old fired installations.

Naturally, this can take many years, consequently, the period between 2025 and 2050 must be considered, making the balance and the phase-out simultaneously in each period, that is, this is a dynamic scenario, that can only be addressed using Linear Programming, as per my understanding.

Why?

In part because the need for holistic approach, but also due to the extensive gap among these years, it must be divided in periods, and the decisions values for the next one based on the last one, i.e. there is a need to consider precedence. That is, in 2030 make the analysis for 2030/2035 on the base of what happened in 2025/2030, new demands and new advances in electricity generation, like for instance, using organic PV solar cells (OPV), as well as political considerations.

You said that the EU estimated that by 2030 the share of renewables would be about 45% which in my opinion was over optimistic. I wouldn’t be surprised if they did not consider the construction time for new wind, PV, and biomass installations. In 2022, I did the calculation for 2035 following the above-mentioned procedure, and obtained a total value for renewables of 34%, and an estimate that the 100% would be reached around 2075, unless nuclear fusion plants, (See ITER), still in tests, are put in operation about 2040. Also, AI says that the EU has an ambitious goal for 2050

However, I did not consider the energy that can be generated by renewables and stored in packs of batteries, that can even sustain deliveries of up 50 MWh. Obviously, they will probably will reduce the interval to reach zero emissions.

4- In page 16 your formulas indicate a linear regression to link criteria, but even when this is an acceptable procedure, you add-up each one of these expressions, which in my opinion, does not address the problem. You list energy mix, renewable energy consumption, foreign investment, GDP per capita, e missions, world indicators and variance on inflation factor. Thus, you cover four economics indicators, demand, renewable participation, and two indicators, which is correct, but what about health, people approvement, workers compensations, environment, land use, etc.? In addition, where is the construction of new renewable plants?

It does not contemplate either the mutual influence of each criterion on the others, like energy mix and the construction of new units, also linked to investment and GDP/capita, etc., however you show that this relation in formula (3), and also in page 16 you detail some more interrelations, formulas (5), but only considering pairs of criteria.

5- However, my concern is related with the fact that you determine pairs of correlations, and from that you assume a cause-and-effect relationship, that may not exist. For instance, you say that since energy mix strongly correlates to renewable energy consumption. I am afraid that it possibly is not true, because from the correlation you deduct that if energy mix increases it affect consumption and this is probably inexact..

Remember that correlation indicates that two variables in crease/decrease in the same sense, i.e. If one increases the other must also increase and that is not what a correlation measures. For instance, consumption due to many different reasons like an increase due to better economic conditions allowing many people to buy and enjoy more electricity, like a fridge, even when the ix has not changed

Page 25 “FDI may not directly impact the energy mix” I believe it is the opposite, the investment can be directed to building a OPF farm, that did not exist as an option before.

Page 25 “The interaction between GDPPC and CO2 emissions in Eq. (4) shows no significant impact on the energy mix, indicating that economic growth within the EU does not necessary lead to a cleaner or more diversified energy mix when considered in isolation”

I think that this is a conclusion very difficult to prove or believe, since the GDPPC can in ease due to many different concepts, for instance a considerable improvement in the prices of commodities that the country exports. Therefore, economic growth that depends on hundreds of issues may lead to the necessity to add more sophisticated options to satisfy demand. For instance, in some countries a large farmer cultivating peanuts can modify the mix by using the shell of the grain as fuel

6- Page 26 “This finding is consistent with research suggesting that without targeted policies, economic growth alone does not guarantee a transition towards a sustainable energy mix”

I agree, and the word here is ‘targeted’. If you do not have targets for your goals or criteria, it is

impossible to register progress or setbacks

7- Page 26 “On the other hand, solar photovoltaic energy shows a negative and significant effect in the Fixed Effects and GMM models.This could reflect challenges in integrating solar”

And wind does not have fix effects? I think that along the day the irradiation may change, but the solar cell continues working albeit with different outputs, while in the same period the wind can vary from very weak to very strong, and out of established limits in ceases to generate. There could also be no wind at all

It is obvious that your paper approaches the zero emissions problem very seriously, and in much more depth that other studies I have seen, but I believe it is incomplete, since not all interrelations between all criteria and energy sources are taken into account simultaneously.

I will be delighted If you wish to discuss this subject with me either publicly or privately

Nolberto Munier