noun [en-er-jee trans-mish-uhn]
the travel of energy from its point of origin to the consumer
Energy has to travel--often very long distances--before it reaches the consumer. Transmission can often result in additional environmental impacts, such as an increased carbon footprint and life cycle costs.
Forms of energy and their processing vary widely, but most of them follow the same basic steps to get from their origins to the consumer:
- Fuel and Harvest. A fuel source is be prospected, located, and then developed (like wind farms) or extracted (like strip mining coal).
- Processing. Fuel is transported to a processing facility. This can be quite a long trip - such as coal traveling to the Midwest by rail from Virginia or Wyoming, or a shorter trip - such as corn headed to the ethanol factory via semi-truck. Or it can be no trip at all, as in the case of methane capture facilities located at feedlots, or with turbines spinning in the wind.
- Distribution. Once processed into a usable form, the fuel travels to consumers - gasoline moving by tanker from refineries to gas stations, or electricity moving through power lines from power plant to substations to consumers.
- Use. Consumers transport energy in their daily lives, too - often in the form of batteries that power cell phones, iPods, PDAs, and laptops. Consumers also drive to places (like gas stations) in order to purchase energy.
- Disposal. After a fuel is produced, there are often by-products to clean up and transport somewhere else - the storage of nuclear waste, for example, or the disposal of batteries.
The transportation of electricity is an important conversation, especially as the development of renewable energy changes the role of transmission in our energy use.
Electrical transmission takes places through a sophisticated and complex network that was primarily developed around nonrenewable fuel sources. Electrical energy cannot be stored (with the exception of batteries, which are not economical to construct or use on a large scale). So once electricity is generated, it must be dispatched.
Once generated, electricity enters the grid through a substation located at the generating facility. It then travels along high-voltage transmission lines that move energy quickly over long distances. Transmission lines end at substations that are located at the edges of various energy markets, like a city or an industrial facility, where the energy is distributed to users.
The recent push for increased renewable energy means that there are an increasing number of generation sites, such as wind farms. However, to get that power to the market, wind farms need transmission lines. Transmission lines are not readily available in rural areas. They are also expensive to build and cannot be built without the cooperation of several key stakeholders. In order to fully utilize the potential of renewable energy sources, generation sites, government agencies and municipalities must work together to change the way we construct and maintain transmission lines.
HIGH VOLTAGE DIRECT CURRENT LINES
High voltage direct current (HVDC) is the preferred technology for moving large amounts of power across long distances. HVDC results in overall higher efficiency and reliability than an equivalently-sized alternating current (AC) system moving the same amount of power.
In Direct Current (DC) lines, the flow of electric charge runs in only one direction. In Alternating Current (AC), the movement of electric charge periodically reverses direction. The major advantage of DC power lines is their efficiency - less energy is lost as it is transmitted and there is no need for reactive compensation along the line. DC (Direct Current) flows steadily through the wires without changing direction many times each second. It also flows through the entire conductor rather than at the surface. As a result DC (Direct Current) transmission lines typically lose less power than AC transmission lines.
HVDC has other benefits as well:
More efficient: Over long distances, HVDC transmission can move more power with less electrical losses than an equivalent AC transmission line.
Lower Cost: Higher efficiency means a lower transmission cost, helping renewable energy compete against other power sources.
Improved Reliability: HVDC transmission can enhance system stability, allow the operator complete control over power flow, and facilitate the integration of wind from different resource areas.
Smaller Footprint: HVDC transmission lines require narrower right-of-way footprints, using less land, than equivalent AC lines.