Four Ways To Increase Transmission (Text Version)
This is the text version of the video Four Ways to Increase Transmission.
This video details four options NREL is researching to increase power transmission capacity in the United States. It shows how each option could help the U.S. transition to a clean energy future where many energy sources are far away from the population centers they would serve.
[Animation of a car driving along a road overlaid on a map of the United States.]
[Narrator speaks]
If you’ve ever road-tripped across the United States, chances are you saw a lot of power lines.
[Graphic of power lines animates on along the road.]
And in a new high-renewable-energy future, you might see even more.
That’s because it’s going to take a lot more wind and solar to decarbonize and a lot more transmission to deliver all that electricity from the windiest and sunniest regions to where people live.
[Animation zooms in on power lines, additional power lines fade up then fade out, additional yellow dots animate onto the power lines, then an additional set of power lines with extra yellow dots animates on.]
To increase transmission capacity, we can increase the number of transmission lines, increase how much power the lines can carry, or both.
Like any long-lived infrastructure, it will take some careful planning to figure out the right combination of options to maximize transmission—both old and new.
[Text on screen: Dynamic Line Ratings]
Option 1 is to change the way we operate transmission using dynamic line ratings.
A line rating is the maximum amount of electricity that a transmission line can safely carry.
[Animation zooms out to reveal cars and trucks driving on a highway in the foreground.]
Think of it like the maximum speed a driver can go. Grid operators often set a conservative line rating based on the worst-case conditions for the transmission system.
Super-hot days when conductors can overheat and cause the wires to sag, touch trees, and cause fires.
But, just as traffic conditions can vary, so can the weather conditions that affect transmission lines.
On cold and windy days, the wires can safely handle more power.
Dynamic line ratings are like adjustments to driving speed based on road conditions.
Just as drivers slow down in snowy or icy weather and speed up in dry or sunny weather, system operators use dynamic line ratings to adjust transmission capacity based on real-time factors like temperature and wind speed.
Dynamic line ratings enable more power on transmission lines when conditions allow—without compromising safety.
[Text on screen: Flexible Alternating Current Transmission Systems]
Option 2 is to retrofit existing transmission or build new transmission with devices called flexible alternating current transmission systems, or FACTS.
Almost all power lines use alternating current, or AC, which has historically been the most cost-effective way of generating and transmitting electricity.
But grid operators can’t actually tell electricity where to go on AC power lines.
That means, even if we build a big transmission line, electricity might still travel on small, overloaded lines. It’s like a driver that doesn’t use a navigation app and takes inefficient routes.
FACTS are the navigation apps of transmission.
[Animation of two sets of power lines with FACTS devices on them. Power flow dots transfer from the smaller lines to the larger lines, with a finger pointing at each of the sets of lines.]
These hardware devices attach to new or existing transmission and monitor and analyze power flow in real time to steer electricity to the lines that are under-utilized.
[Animation zooms back out to show the road and a GPS app along with both sets of power lines. Text on screen: … to optimize the flow of traffic or power.]
Both FACTS and navigation apps continuously assess the changing conditions to optimize the flow of traffic or power.
[Text on screen: Higher Voltage AC Lines]
Option 3 is to build new higher voltage AC lines.
Higher voltage lines are like superhighways that can carry a lot more electricity than lower voltage lines.
[Text on screen: One line with 2x voltage = 4x the amount of power.]
A line with double the voltage can carry four times the amount of power. In some cases, existing AC lines can be retrofitted to be higher voltage.
[Text on screen: High Voltage Direct Current (HVDC) Lines]
Option 4 is to use high voltage direct current lines, or HVDC lines.
[Animation of power lines with two cables per line and yellow dots indicating power flow.]
HVDC lines have several benefits over AC lines.
[Text on screen: Benefit #1: Can control the flow of electricity.
First, electricity on HVDC lines can be controlled, which increases the utilization of the lines.
[Text appears at the bottom of the screen: DC/AC]
HVDC lines use additional hardware called converter stations that convert DC electricity back into AC to be used on the grid. These converter stations are also what allow electricity to be controlled.
[Text on screen: Benefit #2: More cost effective at transmitting electricity very long distances.]
Second, HVDC lines are more cost effective at transmitting electricity very long distances.
It's normal to lose some electricity when transmitting it long distances, but HVDC lines lose less compared to AC lines.
[Text on screen: Benefit #3: Smaller footprint to carry the same amount of electricity. Finger points at differing number of cables per line.]
Third, because an HVDC line has two wires compared to three on an AC line, it has a smaller footprint while carrying the same amount of electricity.
[Text on screen: 5 HVDC lines in the U.S.]
Right now, there are only five HVDC lines in the U.S.
As more wind energy is deployed in remote locations, we’ll mostly likely have to build some more lines, and HVDC lines are an effective and efficient option.
The bottom line: Building our clean energy system of the future will require more transmission capacity to move low-cost renewable electricity into population centers.
With careful planning and a combination of transmission options, the U.S. can optimize the use of existing lines and help reduce some of the need to build new lines—cruising to our clean energy destination, faster and cheaper.
[Animation ends, NREL logo appears.]
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