Submarine Transmission - TRED
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Submarine Transmission

Realistic Solutions

Moving to a zero-carbon future is an achievable challenge. It means moving away from fossil-fueled power generation and transportation. And a wide variety of renewable resources need to be brought on line to serve the existing electrical load and new transportation load.

Fossil legacy

The power system of today was built around fossil resources. Fossil generating plants and the high-voltage transmission lines connecting them to our cities and towns are in one place. But the power resources of the future – sun, wind, geothermal, biomass and hydro – are in new, different places.


The power system of today is largely “dispatchable”, meaning that we choose when to burn fuel and make power. That makes it easier to match the production and consumption of power from moment to moment because power is not typically stored at scale. Renewable resources, however, are mostly variable and non-dispatchable. Renewable power is produced when the resources are available, like on windy and sunny days. Variability in renewable energy production occurs daily and seasonally, so we need creative short and long-term solutions to make sure that power continues to be available to serve our needs when the weather changes (or the sun sets) and variable renewable power plants are not generating power.


We can store power in batteries and in other ways. But that involves a cost both in terms of the batteries themselves and in energy losses – what is called “round-trip efficiency” which reflects the loss of power when a battery is charged and discharged. Today’s batteries typically go from charged to discharged over four hours. So batteries are of limited help with the seasonal fluctuations of renewable power.

Batteries typically provide four hours of backup supply and have a service life of 7-10 years. Transmission has a 50-80-year service life and delivers the important benefit of “regional diversity”.

The power of a region

Transmission is the glue that holds our sustainable future together. Transmission throughout California’s renewable resource-rich areas and throughout the western region can gather renewable power and connect it to the grid serving the western region. Think of this as our “interstate power highway.” The sheer size of the western region gives us the advantage of many large renewable resources all experiencing production peaks and troughs at different times. When all are connected over the regional grid the combined variability of the total mix is much less than the individual variability of any particular renewable power plant. That’s good for reliability and it means we can become sustainable faster and cheaper, spending less on batteries.

Environmental justice

Several Los Angeles neighborhoods are burdened by polluting fossil-fueled power plants. It’s a burden that typically falls on the poor and people of color and it has health consequences, including increased rates of asthma, heart disease and other ailments.

Transmission can bring clean power from far away into the cities and feed the sites where we want to close fossil power plants. Ratepayers pay a premium to keep many of these plants running because they are considered critical for local reliability. With new transmission providing an alternate source of clean power to these communities the old, polluting fossil plants are no longer reliability critical and can close. And the people living nearby can breathe easier.

Realistic and Achievable

As important as transmission is to a reliable power system the truth is that people don’t want to see transmission towers and lines, and clearing land for right of way to build and operate transmission has a significant environmental impact. We have also seen in recent years that power transmission and distribution lines have sparked disastrous wildfires. For these reasons new transmission has become almost impossible to build.

Our transmission solutions work better and can be built. We use modern HVDC (high-voltage direct current) transmission technology that allows for efficient power transmission over long distances underwater and underground. Our cables are buried underground and placed on the seabed out of sight. The environmental impact is small and offshore/underground circuits give grid operators more flexibility to isolate and shut down certain above-ground transmission circuits at times of high wildfire risk, providing an important tool to minimize wildfire destruction. Using a sea-based and underground route is key to bringing clean power right into the cities where more power, reliability and resiliency are needed.