Solar Power
Video Introduction:
Text Intro:
The sun delivers an enormous amount of energy to the planet all the time in the form of solar radiation. This energy ends up in many places, like sugars in plant cells, heat in the air and some is even reflected into space by ice sheets. Only recently has this solar radiation become available directly as electricity.
Solar photovoltaic (PV) panels work by using semiconductive materials like silicon that are responsive to incoming sunlight. When a portion of sunlight, called a photon, strikes the correct silicon atom, an electron is released and it’s movement is captured as electric current. Many millions of silicon atoms placed in a wafer can provide enough electric current to make a solar panel viable.
There are other methods to generate electricity using solar energy that rely on the heat of incoming sunlight. A “tower of power” uses a field of reflective mirrors to focus sunlight on a central chamber where water is boiled into steam (Figure 1). Like both the nuclear and fossil fuel generation technologies, this steam is allowed to pass through a turbine which spins an electric generator.
Figure 1. The Ivanpah “tower of power”. www.brightsourceenergy.com
Like wind facilities, solar facilities are designed to capture a given resource and so don’t come in any specific sizes. For reference, a 1000 MW facility would be considered very large. There are minimum amounts of solar radiation required to make solar PV facilities economical (and even tougher requirements for solar thermal plants like the one shown in Figure 3).
- Upfront costs – The technology behind solar PV generation is maturing, which continuously brings down costs, but solar plants are still relatively expensive at $4,000,000 per MW of installed capacity.
- Fuel costs – Free!
- Flexibility– Like wind generation, solar power is an intermittent resource that can't be turned on or off as needed. Output can vary daily (with clouds and no output at night), and seasonally especially in Canada where days are shorter or longer throughout the year and the sun is in a different position in the sky. The typical output for a single solar panel, as a fraction of total possible output, is shown in figure 2 below.
Figure 2. Typical solar panel power output as a fraction of total possible output. http://www.ilsr.org/how-electricity-pricing-can-boost-distributed-solar-part-1-0/
- Capacity Factor - Solar PV systems have capacity factors around 20%, but this figure would decrease the more north the facility was located.
- Environmental impact – The only emissions associated with solar power are from construction and manufacture and are around 55 g CO2 per kWh. There are several special minerals and metals required to make a solar panel and the extraction of these has negative impacts.