The whole idea of space colonization is founded on two facts: the abundance of extraterrestrial mineral resources and the availability of huge amounts of cheap Solar energy. There are basically two approaches to harvest Solar energy for space settlements: photovoltaic cells and solar-thermal power plants. The latter uses the heat from our Sun to heat a fluid, which is used to drive a turbine.
A challenge for photovoltaic arrays, is their efficiency. But there is exciting news from this field, according to The Science Daily, scientists from North Carolina State University have designed a method to increase solar array efficiency up to 45%. This would mean less Solar cells are needed to produce energy.