If you leave aside the environmental aspects of renewable energy and look at the purely economic factors one can see why investing in renewables is increasing becoming more popular, both for the investment world and government or local authorities.
The global energy investment in the first quarter of 2015 is estimated by Bloomberg at US$ 310 billion. Slightly down from a peak of US$ 318 billion in 2011. Wind and solar are still capturing the lion’s share of that investment but that is only because both are long established and there have been some very large projects, particularly in offshore wind which is capital hungry and heavily subsidised.
Bloomberg gives a good overview of the relative costs in their 2013 report which is graphically presented below.
Geothermal power has been left behind wind and solar in terms of both growth rate and installed capacity but it is an area of renewable energy development that is sure to see massive gains in the near future. As is tidal energy when the ongoing development starts to produce cost effective and simply deployable systems for both rivers and offshore.
Also tidal power showed a very high LEC in 2013 but it must be remembered that there is no real information on tidal systems due to the very small number of systems deployed and those being mostly developmental or trial arrays.
Geothermal came in at just under $100 for a binary plant and very cheap indeed for a flash steam plant.
Both tidal and geothermal have significantly less impact on the environment than solar or wind and so are expected to grow significantly in popularity, both for the investors and for the local and central government authorities that will be instrumental in their deployment. It is also expected that as these technologies develop, are deployed and costs reduced their position on the global scale of cost effectiveness will drop significantly and eventually become two of the most economical of the renewable energy systems available.