Yes, the space is a major issue. There is limited amount space which is sunny enough and which is not used not used for crops, livestock grazing or as wildlife reserve. Some countries have more of such space than others. Some countries have none. Anyway, there is no reason to rely on only one renewable source, when we have so many options. Renawables should be chosen according to local environmetnal factors. In one area it is mroe efficient to build geothermal power plant, while in other solar based or wind based etc.