This final paper is devoted to renewable energy sources, both conventional and modern, that are present in the developed parts of the world, including Croatia. It is pointed out why we must focus on renewable energy sources and stop the depletion of fossil fuels as soon as possible, as well as preserve the environment which has already suffered a lot of pollution. Most commercial renewable energy sources are listed and explained and it is explained how the world and Croatia itself must adapt to a larger percentage of energy production from renewable sources. Already available and tested potential solutions are given, which could, with a good motivation and some legal adjustments, become an advantage for Croatia over the previous, less famous trend of investment and building of renewable energy sources. Croatia, with its geographical position and biological diversity, has a lot of potential, on water as well as on land, which could be used for the benefit of obtaining renewable energy. With proper and wise management, Croatia could become an example for some developed countries. With such an effort to set up the equipment to collect energy from renewable sources, we haven’t solved the whole preceding problem, because every solution of energy production on this way has shortcomings that need to be kept at a minimum level. In fact, there is a solution that is already available thanks to new technologies that have recently been developed, which are listed and described in this paper. The solution is the storage and conversion of excess energy and exploitation of this surplus energy when we do not have sufficient production from renewable sources. Finally, it is displayed how to set up a parameter between the production, supply and demand for energy, and all the potential that Croatia has for such a system is shown.