According to the Texas Renewable Energy Industries Alliance (TREIA) renewable energy is defined as:Any energy resource that is naturally regenerated over a short time scale and derived directly from the sun (such as thermal, photochemical and photoelectric), indirectly from the sun (such as wind, hydropower and photosynthetic energy stored in biomass), or from other natural movements and mechanisms of the environment (such as geothermal and tidal energy). Renewable energy does not include energy resources derived from fossil fuels, waste products from fossil sources or waste products from inorganic sources.
In short, renewable energy is any energy source that is naturally replenished, like that derived from solar, wind, geothermal or hydroelectric action.
For more information about the City of Irving’s codes and permitting requirements related to installation of solar, wind and geothermal systems on residential and commercial structures, contact the Inspections Department at (972) 721-4900.
Photo: The solar panels atop West Irving Library.
The sun has produced energy for billions of years. Solar energy is the sun's rays (solar radiation) that reach the Earth. This energy can be converted into heat and electricity. Radiant energy from the sun has powered life on earth for many millions of years.
In the 1830s, the British astronomer John Herschel famously used a solar thermal collector box – a device that absorbs sunlight to collect heat – to cook food during an expedition to Africa. Today, people use the sun's energy for a variety of purposes.
Heat and Electricity
When converted to thermal energy, solar energy can be used to heat water for use in homes, buildings or swimming pools; to heat spaces inside homes, greenhouses and other buildings; and to heat fluids to high temperatures to operate a turbine that generates electricity.
Solar energy is converted to electricity in two ways:
- Photovoltaic (PV devices) or solar cells change sunlight directly into electricity. Individual PV cells are grouped into panels and arrays of panels that can be used in a wide variety of applications ranging from single small cells that charge calculator and watch batteries, to systems that power single homes, to large power plants covering many acres.
- Solar thermal/electric power plants generate electricity by concentrating solar energy to heat a fluid and produce steam that is then used to power a generator.
Benefits and Limitations
There are two main benefits of solar energy:
- Solar energy systems do not produce air pollutants or carbon dioxide.
- When located on buildings, solar energy systems have minimal impact on the environment.
There are two main limitations of solar energy:
- The amount of sunlight that arrives at the earth's surface is not constant. It varies depending on location, time of day, time of year and weather conditions.
- Because the sun doesn't deliver that much energy to any one place at any one time, a large surface area is required to collect the energy at a useful rate.
Photos: (Top) Wind turbines generate electricity at Irving ISD's Lady Bird Johnson Middle School. (Bottom) Texas leads the nation in wind-powered electric generation capacity.
Wind turbines use blades to collect the wind’s kinetic energy. Wind flows over the blades creating lift similar to the effect on airplane wings, which causes the blades to turn. The blades are connected to a drive shaft that turns an electric generator, which then produces electricity.
Electricity Generation With Wind
In 2014, wind turbines in the United States generated about 4 percent of total U.S. electricity generation. Although this is a small share of the country's total electricity production, it was equal to the electricity use of about 17 million U.S. households in 2013.
The amount of electricity generated from wind has grown significantly in recent years. Electricity generation from wind in the United States increased from about 6 billion kilowatt-hours (kWh) in 2000, to about 182 billion kWh in 2014.
- According to the U.S. Energy Information Administration (EIA), Texas leads the nation in wind-powered generation capacity with more than 12,000 megawatts.
- EIA reports that in 2013, Texas generated almost 36 million megawatt hours of electricity from wind energy.
- In 2013, 12 states accounted for 80 percent of U.S. wind-generated electricity: Texas, Iowa, California, Oklahoma, Illinois, Kansas, Minnesota, Oregon, Colorado, Washington, North Dakota and Wyoming. (Source: U.S. Energy Information Administration)
- As of May 2014, the United States is home to 46,000 operating wind turbines. (Source: Wind Energy Foundation)
- Unlike nearly every other form of energy, wind power uses virtually no water. By 2030, U.S. wind power will save nearly 30 trillion bottles of water. (Source: Wind Energy Foundation)
Photo: Did you know that Irving’s West and South libraries use geothermal energy to help heat and cool the buildings?
The word geothermal comes from the Greek words geo (earth) and therme (heat). Geothermal energy is heat from within the earth. We can recover this heat as steam or hot water and use it to heat buildings or to generate electricity. Geothermal energy is considered a renewable energy source because the heat is continuously produced inside the earth.
People around the world use geothermal energy to heat their homes and to produce electricity by digging deep wells and pumping the heated underground water or steam to the surface.
People also make use of the stable temperatures near the surface of the earth to heat and cool buildings.
Geothermal Energy Facts
According to the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy:
- Geothermal energy is available 24 hours a day, 365 days a year. Geothermal power plants have an average availability of 90 percent or higher, compared to about 75 percent for coal plants.
- Geothermal energy emissions are low. Only excess steam is emitted by geothermal flash plants. No air emissions or liquids are discharged by binary geothermal plants, which are projected to become the dominant technology in the near future.
- At The Geysers field in California, which has been in operation since 1960, power is sold at $0.03 to $0.035 per kWh. A power plant built today would probably require about $0.05 per kWh. Some plants may charge more during peak demand periods.
Photo: The Hoover Dam is a hydroelectric facility completed in 1936.
Hydropower is one of the oldest sources of energy. Hydropower was used thousands of years ago to turn paddle wheels to help grind grain. The nation's first industrial use of hydropower to generate electricity occurred in 1880, when 16 brush-arc lamps were powered using a water turbine at the Wolverine Chair Factory in Grand Rapids, Mich.
Because the source of hydroelectric power is water, hydroelectric power plants are usually located on or near a water source.
The first U.S. hydroelectric power plant opened on the Fox River near Appleton, Wis., on Sept. 30, 1882.
Hydropower is the largest renewable energy source for electricity generation in the United States. In 2014, hydropower accounted for about 6 percent of total U.S. electricity generation and 48 percent of generation from all renewables. However, only 3 percent of the nation’s 80,000 dams currently generate power. A U.S. Department of Energy-funded study found that 12 gigawatts of hydroelectric generating capacity could be added to existing dams around the country.
- U.S. Department of Energy (DOE)
- Estimating Appliance and Home Electronic Energy Use
- For more information about the City of Irving’s codes and required permits related to solar and other forms of renewable energy installation, please contact the Inspections Department at (972) 721-4900.
- Get Your Power from the Sun – A Consumer’s Guide (DOE)
- Guide to Passive Solar Home Design (DOE)
- Installing and Maintaining a Home Solar Electric System (DOE)
- Look for renewable energy incentives at the Database of State Incentives for Renewable & Efficiency
- Natural Resources Defense Council
- Passive Solar Home Design (DOE)
- Texas State Energy Conservation Office (SECO)