The ultimate source of power in our solar system is the sun. It heats our world, drives our weather, and provides life in the form of sunlight to plants. It only seems fitting that it should come to provide us with electricity as well. However, it isn’t that simple.
Sunlight is often looked at as being the ultimate renewable power source. It’s free, and will continue to shine long after humanity is a footnote in Earth’s geological record. However, sunlight is not constant. Solar power only works during the day, and is most effective in areas that receive near-constant sunlight with little in the way of clouds or varying weather. Since solar power is intermittent, it cannot normally provide base load power, and instead, like wind, serves to supplement base load, and provide energy during peak times. At this point, another, primary source of power is needed to provide the base load.
There are two ways to get power out of the sun. The first method is thermal. The sun is used to produce heat, which is used in some sort of heat engine to operate a generator. In electrical power systems, this is done with mirrors or lenses to concentrate the sun’s heat onto a central collector. Solar thermal designs, if properly equipped, are able to store heat in media such as liquid salt or purified graphite, and then later use the heat to operate the generator. In this way, a solar thermal system can actually provide power on cloudy days or at night, making it suitable for low-level base load applications. It is not a replacement for conventional base-load systems, though, like hydroelectricity, coal-fired plants, or nuclear power. These solar projects simply cannot provide enough power all the time.
The other method of generating power from the sun is photovoltaic (PV) panels, which are more familiar to most. These flat panels generate electricity directly from light. While there are a few PV power plants, notably in Spain, Germany, Japan and the United States, most PV installations are on homes and in other small-scale operations. PV modules are expensive, but as the technology improves, the cost will go down and the efficiencies will increase. As smart-metering becomes more common, the ability of home-based systems to sell power back to the grid makes them even more attractive. Again, though, these systems are best looked at a supplement, rather than a replacement, for conventional base load systems in most situations.
For solar power to truly become an effective base-load provider, it has to get big, and it has to get out where the sun always shines. Space-based solar power plants have been studied for years, but launch costs are the ticking point. At current costs to get material into orbit, they simply cannot be made viable. Perhaps if future technologies like a space elevator actually occur, then space-based solar power could become a reality.
In the meantime, solar power can be used to help meet peak power needs, and can even provide some of the base load, but it is very location dependent. The future of solar power seems to lie in decentralized power generation, on the scale of homes, commercial buildings, and neighbourhoods.