There are many ways to harness energy in light ... sunlight in particular.
The first and most obvious but often appreciated is the cultivation of fuel crops that use light (more water and CO2 from the air and minerals in the soil) to build biomass that can then be converted through various media to energy. Same time). There are a number of technologies (anaerobic digestion, gasification, pyrolysis) that reduce carbon to energy, trap GHGs and offer a carbon co-product that can be returned to the earth.
This can be done for the same or less per kW capacity than coal or NG power plants (see Terrastar.com for more information). In addition, vegetable matter effectively "stores" energy for later use.
Photovoltaic panels continue to fall in cost and more storage options will soon be available. We will soon find that, following the rules of supply and demand, the price of electrons will fall in price.