I want to generate an output raster map which indicates the areas of wind and solar energy potentials. My study area is India. I have created GHI (Global Horizontal Irradiance) raster map (by interpolating point GHI values available). Similarly, I created wind speed map,by interpolating MERRA satellite data. Now for making Wind-Solar hybrid map, if I add the two raster layers by "Raster Calculator" of Spatial Analyst Tool in ArcGIS 10.1, then this is the right way of doing this?
I would first normalize your values, then find the average of those normalized values in each cell.
This assumes that you apply an equal weighting to solar and wind energy generation methods. If you want to weight them differently, multiply the normalized values by the weight before finding the average.
The weighted overlay tool more or less performs this process for you
Combining different data for decision making often has a part of subjectivity, but this can be driven by some expert knowledge.
I would try to reclassify (using reclassify tool) each raster based on this expert knowledge in order to have the same scale (e.g. from zero (very bad) to 10 (excellent) ). Once you have the same scale of appreciation for your inputs, you can combine the two rasters using you weighted average (e.g. with raster calculator) depending on how much focus you want to put on each layer. Again, selecting the weights can be tricky, but if you don't know which layer is the most important, the safest method consists in taking the arithmetic average.
As a remark, it is better to always try to quantify in the same unit if possible. So if you are able to translate wind speed and solar energy into values of electric energy, then you will have a better combination of the two energy sources and you should not try an average but take the maximum of the two sources (assuming that you cannot build both at the same place, the spatially hybrid map would consist in using the best device at each location, not mixing them locally.)