# 208

Dear John Paul Galvan

I read your article

Suitability Analysis for Solar Energy System Development using GIS and AHP in Cagayan Province, Philippines

My comments:

1- In the abstract you mention that your work is based on a combination of GIS and AHP. The first is obviously a must, the second is very dubious. Why I say this? Because AHP involves weighting the importance of the different terrain levels using personal preferences, and in reality, a serious and costly project dealing with solar energy is not selected based on personal preferences, but in facts.

In addition to this, do you think that a problem of this complexity can be solved based on only three criteria, very well chosen by the way, but completely insufficient, and because of that results probably are not reliable.

2- Your presentation of the problem is impeccable, for the amount of information you furnish, and for the abundant references.

3- In page 5 you say “The selection process for suitable sites for the PV system is affected by several factors and criteria, which are generally categorized as technical, economic and environmental (Charabi and Gastli, 2011)”

I am afraid that said reference is not very helpful. Locational analysis like this, depend on many more criteria, related to weather, population density, environment, social issues, benefits, costs, demand, etc., however, in one of them, in environment, you mention and very rightly, buffers zones and land-use land-co er aspects someting that I have not seen in most projects related to solar applications, perhaps because most of them were on isolated and desertic areas while your province has a moderate population density.

I guess that the scores to layers you talk about comes from the Fundamental Scale in AHP, which does not have any scientific foundation

4- In page 6 “In this study, the solar insolation data used was taken from Geospatial Toolkit (GST)”

You should tell the reader that it is a map-based software application. Remember that the reader may be somebody not familiar with these types of technologies.

5- In Section 2.6 you address the AHP model you use. In my opinion, it is a very simple method and not able to address this complex problem due to several issues as:

Using pair-wise comparison between different criteria or situations in something that humans d, many times during a day, it is what guide our movements, it is a very valuable tool.

But assigning a quantitative value of preference is an aberration. Can you say for instance that study is say three times more important that work, or that tenderness is two times better that love, or than comparing two football teams that elegance is three times more important than coordination? Please, think about this.

· Why the DM preferences must be transitive? There is no reason for that, and usually they are not. Why if his/her estimate are not transitive? He is forced to correct him/herself. Where is the logic?

I could continue, but I think that this is enough. However, the most important issue against AHP. ANP and most MCDM methods is that they consider each criterion individually, when all of them should be taken at the same time. You cannot ‘optimize’ each criterion and sum all of them to get a result. As a simple example: If you have to cook a stew that includes meat, species, vegetables and fish. The final taste of the dish results for the interaction or mix of all ingredients with their different tastes, not from the individual taste or property. In other words, you have to work with intersection not with sums.

AHP demands by construction, that all criteria must be independent. Dou think that environment is independent of the economic aspect? For instance, a huge solar farm uses land and then altering the original landscape. It can create reflexion problems that may affect airplanes flight. Look at wat AI says about: “The heat generated by the solar panels can alter the local climate by creating updrafts that lead to cloud formation and potentially increased rainfall?

6- In technical aspects, Section 3.1 page 10

Excellent analysis, however, there is something extremely important that your study does not consider and that can completely change your results. There are temperature and humidity, nominated by experts as the most important criteria.

Cagayan Valley has a temperature between 26°C and 32 °C, and rarely below 24 and above 32.

Do you know that the maximum temperatures that PV plants work efficiently is 25 °C? Above that, the output decreases sharply and may cause losses of 30%. Why this was not considered in your paper?

Regarding humidity the average humidity is 82 % and that causes corrosion and decrease in the energy output

In addition, why did you only consider solar power when the province has excellent sires for wind energy generation is the order of hundreds of MWh. am not saying that you are wrong, but it is evident that a previous analysis between these two modes of electric generation among these two sources must be performed, and even sharing the available space.

These are my comments. I hope they will be of help

Nolberto Munier