Solar Power
Solar power has been promoted for quite a few years now as the ideal energy source since it offers the benefit of being able to provide energy with little to no environmental impact. This has made solar power an area where a lot of investment has been made. Yet despite all of this investment solar power has remained a fairly small part of our energy supply. There has certainly been some progress made over the years and there are applications for which solar power is an ideal solution. Nevertheless we are still a long way from the point where solar power is one of our major sources of power.
The biggest problem that needs to be overcome in order for solar power to become more widely used is the fact that the sun doesn't shine all of the time. The sun is only available as a power source half of the time at best. In reality is available even less often than that because it isn't practical on cloudy days. This means that we either need to find a way to store excess energy that is generated on sunny days or an alternative source that can be used when the sun isn't available. A third option of putting satellites into space that will be able to generate solar power twenty four hours a day and beam it back to earth is probably prohibitively expensive. There has been good progress made in storing the energy generated by solar power but we are still a long way from practical applications.
The other main reason that solar power has remained relatively limited as an energy source is the high cost of the equipment required. In most cases unless solar power reaches the point where the cost savings of generating electricity this way will offset the cost of installing the equipment there will be little demand. For all the talk about the environmental advantages of solar power ultimately it has to be competitive in terms of cost. Currently that isn't the case. The hope is that with further development solar power will be able to offer electricity for a lower total cost but we are still a long way from that point. In order to get to that level a lot of challenges are going to have to be overcome.
Solar power looks likely to remain an area where there is a lot of research and development being done. It is probably still the most likely of the alternative energy sources to become mainstream. However it still has a long way to go and quite a few obstacles to overcome. In all likelihood the increasing cost of other sources of energy will likely make solar power more competitive and that is the best hope for the future. Until that time comes however it is likely that solar power is going to remain confined to specialist and small scale uses.