This is post two of our four-part series on renewable energy. If you tuned into our blog post yesterday, we introduced the idea of using renewable energy as a way to keep up with economic demand while reducing our impact on the environment. It may have left you with some questions about what our options are – so keep reading to learn about some of the major trends in renewable energy, including solar and wind power!
What is Solar Energy?
Plants are able to harness energy from the sun, so why can’t we? Solar energy is generated by converting the sun’s thermal energy into electrical energy. Solar energy is the most abundant renewable energy source available and generates clean, reliable, and affordable electricity without releasing greenhouse gases and other air pollutants. There are two ways in which solar energy can be converted into electricity:
- Photovoltaics: Photovoltaic cells (PVs) change sunlight directly into electricity.
- Solar thermal/electric power plants: Solar thermal/electric power plants generate electricity by concentrating solar energy to heat a fluid and produce steam to power a generator.
Solar installations in the US have become much more widespread, increasing seventeen fold since 2008. When operating at optimal conditions our current solar capacity can produce enough energy to power 4 million American homes.
What are the Pros of Solar Energy?
1. Abundant: Solar energy is the most abundant resource on earth and has strong potential to help us meet our growing energy demands. Currently, the world consumes about 15 terawatts of energy (1 terawatt = 1 trillion watts). The sun deposits 173,000 terawatts (TW) of solar radiation on the surface of the Earth continuously – that’s more than 10,000 times our current energy demand! Surprisingly, one does not need to live on the equator to benefit from solar energy. Germany generates about 7% of its total electrical needs from solar energy.
2. Zero emissions: Producing solar power does not release harmful emissions into the atmosphere.
3. Siting: Small scale solar may be installed almost anywhere. Many solar panels may be placed on rooftops of existing buildings – reducing their land footprint. Large-scale solar thermal/electric power plants have a larger land footprint, as they require a lot of space.
4. Low maintenance: When installed properly, solar panels require very little maintenance.
What are the Cons of Solar Energy?
1. Intermittent: Solar energy – while abundant – is not constant. The amount of solar energy hitting the earth’s surface varies depending on the time of day, time of year, weather patterns, and location. Most cities experience the greatest demand for power in the afternoon and early evening when solar energy is not able to be captured it its greatest potential. Solar energy plants are also vulnerable to changes in cloud cover and weather patterns – a plant’s efficiency may be significantly compromised by a cloudy day or afternoon storm.
2. Energy storage: One solution to the challenge of intermittent energy sources is investing in energy storage. In these systems, batteries and other devices store generated energy for later use. Unfortunately, energy storage systems right now are costly and underdeveloped. We need to make a commitment to advancing research and development in energy storage technologies, such as flow batteries and grid energy storage systems, if we are serious about transitioning into a new energy model where energy demands are met from renewable sources.
3. Cost: It is very expensive to bring a solar plant on line. While technological advances and federal incentives have caused the cost producing solar energy to fall dramatically over the past 20 years, solar energy production is still more expensive than coal and natural gas. One way to examine the competitiveness of different energy sources is to compare levelized energy costs. The levelized cost of energy (LCOE) is calculated by taking the total cost to build and operate a new power plant over its lifetime divided by its expected energy output –measured in dollars per kilowatt hour ($/kW-hr). Coal and natural gas have low LCOEs ($.07-.$14/ kW-hr). The LCOE of solar power is nearly double that of coal and natural gas, averaging between $0.13 and $0.24/kW-hr.
*It is important to note that growing demand for energy coupled with federal incentives may lower the levelized cost of solar energy in the future. Solar energy is economically-competitive with conventional energy sources in several states, including California, Hawaii, Texas, and Minnesota.
4. Rare earth materials: Many photovoltaic cells are made of rare earth minerals like silicon and other metals like mercury, lead, and cadmium. These materials required in PV cells can be rare, expensive, and potentially harmful to the environment.
What is Wind Energy?
Wind energy is energy extracted from air flow using wind turbines. Wind turbines convert kinetic energy (energy from motion) into mechanical power and then electricity. A single 1 Megawatt (MW) turbine can generate enough electricity to power 225-300 homes. Wind energy makes up 4.4 percent of the total US electricity generation. In the last 10 years installed wind capacity has increased by nearly 880%. In 2012, wind was ranked the number one source of new U.S. electricity generation capacity – representing 43% of all new electric additions.
What are the Pros of Wind Energy?
1. Low levelized cost: Wind energy has a very low levelized cost of energy (LCOE). The cost of wind energy has come down 85% over in the last 20 years. Recall, average LCOE for coal and natural gas range between $0.07 and $0.14/kW-hr. Wind ranges between $0.08 and $0.20/kW-hr, making it a competitive option for those living in the right geographic areas.
2. Small environmental footprint: Wind energy does not produce harmful atmospheric emissions. Wind farms also have a small land footprint, allowing for the land beneath them to be used for other purposes like farming and cattle ranching. Futhermore, wind turbines have a relatively low impact on species populations. The effects of turbines bird and bat populations has been a long contested within the scientific community, however, a recent National Wind Coordinating Committee report concluded that these impacts are low and do not pose a threat to species populations.
3. Quick construction and high payback: Wind has one of the fastest “energy payback times” of any source of electricity. With careful siting and community outreach, wind farms can be built in a fraction of the time it takes to install their conventional counterparts (coal and natural gas). Some wind farms can be completed in less than a year, meaning they can begin recovering the cost and energy expended to build the farm much earlier – sometimes in as little as three to eight months.
What are the Cons of Wind Energy?
1. Siting and transmission: The best sites for wind farms are often located in remote locations far from areas in which energy demand is high. Transmission is necessary in order to bring electricity from wind farms to cities. Unfortunately, a great deal of energy is lost in transmission. The EIA estimates that 6% of energy produced in the U.S. is lost during transmission and distribution, this figure becomes much higher when the distance the energy must travel increases.
2. Energy storage: Similar to solar energy, wind is an intermittent energy source. Therefore, more sophisticated technology in energy storage must be adopted to help store excess energy produced when demand is low.
Feeling like a renewable energy expert yet? You will be by the end of this series! Tune next week to explore the benefits and limitations to hydro, tidal, biomass, and geothermal energy.
Post 1: Why do Renewable Energy Sources Matter?
Post 2: What are the Pros and Cons of Solar and Wind Energy?
Post 3: What are the Pros and Cons of Hydro and Tidal Energy?
Post 4: What are the Pros and Cons of Biomass and Geothermal Energy?