Despite the differences, one fundamental and common issue for the increased penetration of renewable energy sources in the world's economy is the development of adequate energy storage systems. The field is still at its infancy and there are tremendous opportunities to develop innovative solutions.
Few demonstration facilities are in the developmental stage or have been implemented in the world. I just came back from three weeks trip to Australia and Japan where it has been fantastic to visit some of them!
You can read more about Sabrina Sartoris trip to Australia and Japan here