Making the Most of the Existing Grid

We need more grid to facilitate the move to a zero-carbon power supply.  But new power lines are expensive and slow to build. There is a growing interest in new technologies that make it possible to get the most out of the existing grid.

The power grid is rapidly shifting from fossil-fueled to clean generation, and from centralized power plants to distributed ones. Moreover, the power grid is increasingly supplying all-electric homes and electric vehicles. These shifts are changing where electricity is produced and consumed, and when it is available and needed.

But the power grid — the poles, wires, transformers, and substations — was built over the past century to facilitate the where and when of the old system. Large old power plants were often sited in industrial zones near water while new wind and solar generators are more likely to be in rural areas. All-electric buildings and cars will drive up demand on neighborhood distribution grids, and boost electric demand for winter heating.

It’s easy to call for rebuilding our power grid, and indeed some rebuilding and expansion is unavoidable. But that is an expensive, long-term, and sometimes difficult proposition, and is already driving up the cost of electricity, which in turn makes the switch to clean electrification harder.

A better first step is to make the most of the existing grid. Using smarter digital controls, real time communications, and new technologies, companies are expanding the capacity of the current system.

New power lines are being built, but only with great effort. The SunZia line, a 550 mile line across New Mexico and Arizona, will enable 3,500 megawatts of new wind generation, enough for 3 million households. Ava customers will be part of that, supplied from Pattern Energy’s current Tecolote Wind project near Duran, New Mexico, and a new project in Lincoln County, expected online in 2026. The SunZia line took 12 years to get through the permitting process, yet was being challenged in court even as construction began this summer.

The California Independent System Operator (CAISO) in their 2023-24 transmission plan, approved in late May, is expecting 26 projects around the state, with a total capital cost estimated at $6.1 billion. The big ticket items are two large new lines, totalling 400 miles, that would connect anticipated offshore wind farms off the north coast near Humboldt.

Ava has not signed up for any offshore wind yet, but is a member of California Community Power (CC Power), a Joint Powers Authority that conducts joint power procurement with nine CCAs. CC Power signed an MOU in May to investigate developing an offshore wind project off the central coast near Lompoc.

Big new lines open up big new clean energy developments. But companies are also looking to do more with existing lines, by retrofitting them with new more capable wires and adding smart “grid enhancing” technologies.

Transmission lines are typically made of copper wrapped around an aluminum or steel core. They can soften up when they get hot, causing lines to sag and potentially hit trees and start fires. New “composite core” lines, shown in the figure, have a core made of carbon fiber, which reduces sag and the number of towers needed, and increases capacity.  The carbon-fiber cores are about 50% stronger and 70% lighter than steel cores, allowing the line to use more conductive aluminum without adding weight.  Replacing or “reconductoring” existing wires can double the throughput at a much lower cost than building new lines.

A report from UC Berkeley’s Goldman School of Public Policy and GridLab finds that reconductoring US power lines would enable the US to hit 90 percent renewable energy by 2035, while saving $85 billion by 2035 and $180 billion by 2050.

An even bigger boost can be had by converting long-distance alternating current (AC) lines to direct current (DC). While this requires the installation of expensive AC-DC converters, it can increase the throughput by as much as eight times.

Grid controls can also be an effective strategy. A suite of technologies known as GETs — grid-enhancing technologies — bring digital monitoring and controls to a formerly analog system. 

While GETs can get very technical, those that affect line ratings may be the clearest example. The capacity of a line can be affected by air temperature and wind; hot weather reduces the lines throughput, due to the risk of sagging. But a line’s capacity rating is often just a single number, set by an engineering calculation based on average conditions. Dynamic line ratings (DLRs) take real-time weather conditions into account, giving a more accurate number as conditions change.

Research by Idaho National Lab and others has found that cooling winds can increase the amount of current a line can carry by 10 to 40 percent above a static rating that does not take wind into account. Since a nearby wind farm will be producing more power at that windy time, the line could likely carry more of that wind power, reducing the risk of curtailment.

Deployment of DLR technologies has delivered stunning results. LineVision did a pilot project with New York utility National Grid to test DLR sensors and controls, along with five miles of circuit rebuilds. The project is expected to reduce curtailments from two large wind farms by more than 350 megawatts and increase overall transfer capacity by an average of 190 megawatts. In Pennsylvania, utility PPL deployed a DLR system that saves over $23 million per year, at a cost of only $250,000.  A rebuild of that line would have been about $50 million. 

The case for GETs and reconductoring is so strong that bills are moving rapidly through the legislature (AB 2779/Petrie-Norris and SB 1006/Padilla) requiring their consideration in planning grid improvements. 

California is one of 21 states that in May joined the Federal-State Modern Grid Deployment Initiative, committing to “accelerate the near-term deployment of more advanced, commercially available grid technologies to expand grid capacity and build modern grid capabilities on both new and existing transmission and distribution lines.” 

California utilities have been aggressively adding grid monitoring and controls, but mostly aimed at reducing the risk of wildfires. Protective Equipment and Device Settings (PEDS) automatically turn off power within one-tenth of a second if an object like a tree branch contacts a distribution line.

PG&E started deploying PEDS in 2021 across 11,500 miles of distribution circuits in High Fire Threat Districts, cutting fire ignitions in the first year by 68 percent.  More detailed grid monitoring and controls also allows cutoffs to be more accurate, reducing the number of customers affected and the duration of the outages.

Southern California Edison (SCE) has used reconductoring to reduce wildfire risk.  Along their Big Creek corridor, transmission towers were short enough that sagging wires ran the risk of touching trees.  Replacing the lines with advanced conductors reduced the risk of sag and avoided the need to build taller towers — and it doubled the capacity of the line. Construction time was reduced from 48 months to 18 months, and it saved customers $85 million, according to SCE.

Even bigger projects have been proposed.  CAISO is planning a new 180-mile line running from near Los Angeles to Las Vegas, with an estimated cost of $1.5 to $2 billion. As an alternative, Lotus Infrastructure has proposed converting an existing line from AC to high voltage DC, reusing the existing conductors, towers, and insulators to boost the line capacity by 2200 Megawatts.