These technologies are mostly currently available. Yet, they are not good enough to replace fossil fuel power plant. Other alternative solution for saving energy is reducing wasting energy. One may see many buildings light is turned on all the time and regardless of people. Some are trying to get the sun light during days, and some are trying to implement new technologies on the lighting system.
Several building uses the lighting system using motion sensor and heat sensor.
It detects motion of people and heat energy of people. They are very cheap and easy to obtain.