Although solar power is currently a relatively small component of total US power usage, its share is growing rapidly. Given its renewable and non-polluting nature, political and social pressure to address climate change issues will continue to increase demand for solar power. Figure 1 shows the recently completed Crescent Dunes Solar Energy Project with a capacity of 110 MW of electricity, which is just one of the utility scale solar plants brought on-line in 2015, comprising approximately 4.8 GW of new solar power capacity.
The major pros of solar power are:
- Clean energy requiring no combustion and emits no greenhouse gasses.
- Inexhaustible and abundant "fuel" supply wherever the sun shines. Figure 2 illustrates the electrical generation potential (in terrawatt-years) for each energy source on Earth, illustrating that solar potential dwarfs all others and could provide about 1,000 times as much energy as the entire world is projected to need in the year 2050. A single year of solar power also exceeds the total recoverable power potential from all non-renewable sources combined.
- Extremely versatile from individual rooftop systems, to distributed generation with multiple medium size systems, to large commercial scale systems.
- Technology exists today and is rapidly improving.
- Silent and no moving parts.
- Generates DC power and can be used to provide power for many uses without conversion to AC.
- Components have 25-30 year life and require minimal maintenance.
- Relatively low operating costs.
The major cons are:
- Intermittent source that is not available at night or under clouds, although new technology such as Concentrated Solar Power plants with molen salt storage as well as improving battery storage technology can help overcome this limitation.
- User requires storage or grid connection for round-the-clock electrical power.
- Relatively high initial cost, especially with storage, although cost is reducing rapidly, with utility scale solar plants experiencing a drop in cost of over 15% in 2015. See the OWOE Topic: How much does it cost to build a new power plant?
- Requires additional hardware (inverter) to convert DC to AC current for typical power uses.
- Less available to supply heating demand (time of day and season).
- Exotic materials required in photovoltaic systems, although new technology and new materials are beginning to address this issue.
- Requires a relatively large amount of open space with associated aesthetic issues.
- Relatively low efficiency (around 17-40 percent), although efficiency values have been steadily increasing with technology advancements.
- Distributed solar power (e.g. rooftop or community) will require modifications to current power generation infrastructure, which is based on large power generating plants located a long distance from the consumer.
With the sharp decline in the cost of solar generated power of the past few years, solar power is now the least expensive form of new energy development on a per Kwh basis in some markets, even considering the historically low price for natural gas. This is in part due to the US Investment Tax Credit, ITC, which gives developers a 30% tax credit for solar plant capital investments. At the end of 2015 the US Congress voted to extend the solar Investment Tax Credit (ITC) for another 5 years, which should help maintain investment in new solar power and help continue to drive down costs. It is not unreasonable to expect that there will be further declines in solar cost, and solar should be very cost competitive in the future, and the best solution in many situations, even without credits.
Of all energy sources, solar power has the greatest potential for technological advances to further reduce cost and improve efficiency.