By Rachel Ross
In the past four months, the world’s two biggest solar plants have been opened in the southwestern United States.
Agua Caliente, located in Arizona, is a conventional solar photovoltaic plant, producing 290 megawatts (MW) of power.
Completed last month, the plant takes up 2,400 acres of land in the desert to power cities in southern California.
Ivanpah is a solar thermal plant located in California that produces 400 MW of power.
That is enough to power 140,000 homes and accounts for 30 percent of all solar power produced in the United States at this time.
It was opened in February of this year and covers 3,500 acres of desert.
Solar thermal technology is a relatively new alternative to conventional photovoltaics.
Solar photovoltaic panels are semi-conductors that directly convert the sunlight to electricity.
Solar thermal plants use mirrors to reflect and concentrate the sunlight on an alternate location, directly producing heat.
This direct heat can then be used in solar water heating or to drive a heat cycle, such as a sterling engine.
Ivanpah has 350,000 of these mirrors that reflect sunlight onto 69-story-tall towers, concentrating sunlight to heat steam within, which then turns turbines to generate electricity.
The construction of these two plants reflects policy changes in support of renewable power.
Both plants received federal loan guarantees through a program with the U.S. Department of Energy, which means that if the companies who built the plants do not make enough money to pay back their loans, the government will assume the debt obligation.
This means that the burden of initial costs, a major downfall of renewable energy projects, is decreased significantly.
California also mandates that utilities get a third of their electricity from renewable sources by 2020.
All of the energy from the two plants is being sent to California to help utilities meet these requirements.
These policy tactics lend support to the budding renewable power industry.
Solar plants do not release carbon dioxide — unlike conventional fossil fuel plants powered by coal, oil or gas — reducing the impact of the greenhouse effect on the environment. Ivanpah produces the renewable energy equivalent to taking 72,000 cars off the road.
However, there are problems with these solar plants that need to be taken into account.
For instance, though we may view the desert as a void, the large-scale construction that took place to complete these power plants has an impact on the diverse desert ecosystem.
There have also been worries about bird deaths from running into the mirrors or being scorched by the reflected light at Ivanpah.
Additionally, a lot of power is lost from long-distance transmission of the plants’ isolated location in the desert to the cities that use the electricity.
Solar thermal projects in particular have this problem, because they must exist on a large scale and are therefore generally far away from where the power generated would be used.
This is opposed to photovoltaic panels, which are easily implemented on local and small scales.
Perhaps the largest concern about solar power is that the plants don’t produce power when the sun is not shining.
The Ivanpah plant, however, has improved upon many of these problems.
Since solar thermal only directly produces heat, the energy can be stored in various mediums.
This design on solar thermal plants allows for storage of energy overnight or in the event of bad weather, a necessary step in increasing the amount of power utilities can get from renewable sources.
Ivanpah also uses a dry-cooling system, reducing the amount of water consumed by 95 percent, to the amount used by two holes at a nearby golf course.
The construction of these new plants adds tremendously to the importance of renewables in the energy mix.
Although they are great achievements towards reducing the impacts of climate change, there are still concerns about the construction of such large-scale renewable projects that need to be taken into account.
Ivanpah and Agua Caliente are both important steps in the process of transitioning to more sustainable sources of energy.