Infrastructure Solutions: Renewable energy surges forward

This installation of Civil Engineering’s Infrastructure Solutions series, which looks at how civil engineers are using cutting-edge techniques to resolve the issues identified in ASCE’s 2017 Infrastructure Report Card, examines the nation’s energy system. The United States’ transition from traditional fossil fuel and nuclear sources to other sources of renewable energy has significant implications on transmission and distribution infrastructure — both on land and at sea.

In the United States, most electricity transmission and distribution lines were constructed in the 1950s and ’60s with just a 50-year life expectancy, according to ASCE’s 2017 Infrastructure Report Card. This patchwork system comprises public and private power generation facilities, transmission and distribution grids, local distribution lines, and substations. This group of infrastructure received a D+ on the report card — a grim assessment. However, there are bright spots within the energy field, as new technological developments and decreasing prices are making the transition from fossil fuel and nuclear power generation to newer forms of renewable energy a successful one. 

ASCE will issue its 2021 Infrastructure Report Card in March. In the meantime, the Society in September published Failure to Act: Electric Infrastructure Investment Gaps in a Rapidly Changing Environment, the latest in a series of reports that quantifies how the persistent failure to invest in our aging infrastructure impacts the American economy. The report reveals that in total, the 48 contiguous states and the District of Columbia are facing a $208 billion investment shortfall in electrical infrastructure investment by 2029, which will increase to a whopping $338 billion shortfall by 2039. (See the chart.)

The report forecasts the United States’ electrical infrastructure investment gap by comparing the projected infrastructure investments that are planned in the nation with its projected needs. The report considers three categories: generation, transmission, and distribution. The United States contains approximately 10,000 commercial generation facilities that use resources such as coal, water, solar, wind, natural gas, nuclear, and other sources to generate electricity. Transmission lines are the “highways” that move electric power over long distances from generation facilities to substations, and distribution lines are the “local roads” that move that electricity locally to its final point of use. Household and business needs, the age of existing infrastructure, and evolving energy technologies and policies were each taken into consideration in the report. 

In the contiguous states, there are three main interconnected electric transmission grids: the Western Interconnection, the Texas Interconnection, and the Eastern Interconnection. Within these three main grids, Failure to Act identified eight regional operating grids for its analysis: West, Southwest, Texas, Midwest, Southeast, Northeast, Mid-Atlantic, and Florida. In the contiguous 48 states, there are more than 640,000 mi of transmission lines that are congested and operating at full capacity, the report card states. The grids in Alaska and Hawaii are similarly congested, according to the report card.

The investment needs vary by region, Failure to Act points out. The West region alone accounts for 33 percent of the investment gap due to its major land expanse and large population. And the Northeast and Mid-Atlantic regions together account for 43 percent of the gap because they contain some of the oldest infrastructure in the United States. While the report focuses on the contiguous states, it also notes that between 2020 and 2039 an additional $6 million is needed for Alaska and $824 million for Hawaii. (The available data for the report did not include non-investor-owned utilities, which are predominant in Alaska, so its listed investment gap may be underestimated, according to EBP US, which conducted research for the study.)

Part of this potential shortfall in electrical energy infrastructure investment in the United States is based on the nation’s shift toward renewable energy sources. “The United States right now is really in a period of significant transition” as its energy generation shifts from one dominated by fossil fuels to one dominated by renewables, says Jason Hedien, P.E., M.ASCE, the vice president of Power and Dams for Stantec, who is based in Chicago. The transition is taking place as additional capacity is built and older generating facilities, such as coal-fired plants, reach the end of their useful lives and are replaced by renewables, he says.

“Renewable energy will minimize carbon pollution and have a much lower impact on our environment, which is why there is such an increase in demand (for) green generation,” adds Robert Molner, the U.S. solar subsector leader in Stantec’s Power and Dams division. “Renewable energy is currently the fastest-growing source of electric generation to update energy infrastructure. And with modern grid improvements, we have the ability to make the grid more resilient and secure without imposing huge costs on consumers.” 

The transition must also take into consideration the increasing energy efficiency of appliances, equipment, and other end users. This is impacting the way utilities need to distribute power and handle growth, according to Hedien.

The utility industry itself has also become more energy efficient, which has resulted in overall demand remaining relatively flat, according to the Failure to Act report. The forecasted generation shortfalls therefore come from policy changes and “are the result of requirements that a certain share of the overall supply come from renewables,” according to the report. Generation shortfalls are the largest share of the investment gap and are expected to be 65 percent of the total shortfall by 2029, dropping to 60 percent by 2039. Transmission shortfalls, on the other hand, will drop from 12 percent of the total in 2029 to 10 percent of the total by 2039. And distribution shortfalls are projected to make up 23 percent of the total in 2029, climbing to 29 percent by 2039.

Increasingly, states are enacting Renewable Portfolio Standards due to growing concerns about climate change, according to Failure to Act. These RPSs require utilities to incrementally increase the amount of their electricity that is produced by alternatives to fossil fuel and nuclear — such as wind, solar, and biomass, among other renewable options.

“Mandated RPSs along with government subsidies have increased the percentage of renewables generated by utilities and have also stimulated market-based demand for renewable energy among business and residential customers,” Failure to Act notes. “Subsequently, renewable energy generation has become more affordable. The combination of mandates and market demands, along with the geographical relocation of generation, amplify the need to build out new infrastructure to support a reliable, resilient, decarbonized electric grid, while maintaining our existing energy infrastructure at a high level.” 

Two areas that are seeing significant growth right now are solar and wind energy generation, according to Hedien. Hydroelectric power, on the other hand, is already relatively built out in the United States so is not growing as quickly, he says. 

According to the U.S. Energy Information Administration, in 2019 renewables generated 17.5 percent of the utility-scale electricity in the United States. Fossil fuels generated 62.7 percent and nuclear 19.7 percent. (Other sources generated a few hundredths of a percent as well). Within the renewable category, the largest generator of energy was wind, at 7.3 percent of the overall total. Second was hydropower, at 6.6 percent. Third was solar, at 1.8 percent, narrowly edging out biomass at 1.4 percent. Geothermal, the smallest renewable category, produced just 0.4 percent of the total.

According to Tom Kiernan, the CEO of the American Wind Energy Association, the organization expects to see wind reach at least 20 percent of the United States’ electricity production by 2030 and continue growing from that point. When combined with solar, hydropower, and energy storage, “we can see renewables at 50 percent or more by 2030,” he says. “So there is huge growth potential.”

Both wind and solar are referred to as intermittent renewables because they generate power only when the wind is blowing or the sun is shining, respectively. “It’s not that easy to predict exactly how much power at any given time a solar installation will generate. And the same goes for wind,” Hedien says. Traditionally, the United States has relied on large, centralized energy generators, often powered by coal or nuclear energy. These could be used to generate a reliable amount of energy on a predicted schedule. This is not possible with renewable energy.

What Hedien refers to as the “great balancing act that occurs 24 hours a day, seven days a week” is the regional grids trying to balance the amount of energy generated with the expected demand in a region. When demand outstrips supply, regardless of how that supply is generated, utilities might need to implement rolling blackouts, such as those that took place in areas of California this summer when the power was turned off to groups of customers briefly, and sequentially, to conserve energy.

To create a more consistent supply of energy drawn from renewable sources, there is an increasing demand for energy storage in the form of batteries. These can even out the flow of energy to the grid by capturing excess energy as it is produced on-site and pushing it out when a renewable source is dormant. Research into how these batteries might best be developed is ongoing.

In the case of wind, technological developments are also increasing reliability of production. “We are now managing the wind farms as holistic units,” Kiernan says. “Developers now have software so that they can optimize the output from an entire wind farm. There are times when, for example, you want to let the wind pass through one turbine, have it not catch as much of the wind, so that the turbines that are behind it can catch more of the wind, and depending on the conditions and the layout of the wind farm … you can actually get significant additional performance from the wind farm (as a whole).” 

This, combined with the increased construction of winds farms in places like Texas, means that multiple wind farms can also potentially be operated in a way that balances one another’s supplies. This, according to Kiernan, can make wind energy reliable enough for use as a base-load supply, meaning it can continually meet a region’s needs without the need for additional resources. “They can plan on it; they know what the wind forecast is for the next five minutes, 10 minutes, (or the) day ahead, so they can anticipate virtually exactly what the wind performance is going to be, and then manage (generation) accordingly,” Kiernan says.

Taking this theory of wind resource management to an even higher level, another way to even out the supply and lower the cost of electricity is to increase the transmission possibilities between regional grids. “We need to bridge across some of the seams in the country, where you’ve got these different grids,” Kiernan says. “There are not enough connections. What we’ve learned is (that) sometimes the best thing to do for one grid, if it’s producing a whole lot of extra electricity, is to send it to the grid next door.” 

Creating diverse renewable portfolios also enables a region to further improve the reliability of its renewable energy production. “Some producers … will take a wind farm and a solar farm and some battery storage and combine that and turn to a utility and say, ‘Hey, we will guarantee you X amount of electricity day in, day out,’” Kiernan says. “So, that (concept of) variability is old news. The new news is we’re out in the market providing electricity where and when you need it, and guess what? It’s also clean and affordable.”

Hydroelectric pumped storage is a way to generate a consistent amount of power precisely when it is needed and then store any excess energy that might otherwise be wasted. Facilities that use this technique have two reservoirs, an upper and a lower, either in an open system connected to an existing watercourse or in a closed-loop system unconnected to a watercourse, Hedien explains. The water is released from the upper into the lower reservoir, and a consistent amount of power is generated as the water flows. During times of low energy demand, low-cost electricity is used to pump the water back to the top reservoir so the process can be repeated whenever energy is needed. “What’s nice about closed-loop systems is that the environmental impacts of developing these types of facilities are easier to mitigate because we are not impacting a natural watercourse,” Hedien notes. (The EIA notes that hydroelectric pumped storage systems typically use slightly more energy than they produce annually. However, as storage facilities, they ensure that renewable energy generation can exist on demand.)

Microgrids connected to a larger grid are also useful in extending the ability of the main energy grid to meet renewable policy goals and generate power, Hedien says. This is because they can collect and use energy locally, but when they overproduce, they can send the extra to the main grid, and when they are not generating enough, they can draw energy back from the grid. 

Even smaller renewable fields — such as rooftop solar on a large building or residence — can feed the grid as well. But the grid’s ability to accept power from all these small distributed generation resources must be managed carefully. “To try and manage that feed into the grid is a challenge,” Hedien says. 

A large number of smaller generating units can actually be more desirable because if one unit stops producing, others might still be able to, according to Maria L. Tome, P.E., M.ASCE, the managing director for Energy Efficiency and Renewable Energy at the Hawaii State Energy Office. She points out that if there are a few large units and one goes down, it puts much greater stress on the system and reliability could be affected.

Smart buildings and electric vehicle charging stations can also work in conjunction with energy grids to ensure that grids are not overburdened during peak periods, according to Tome. While much research is still necessary in this area, Tome envisions situations in which such interactive and efficient infrastructure can better balance the flows from a microgrid. A smart building can automatically turn off a water heater or air conditioner for five to 10 minutes, for example, to reduce energy consumption in an unnoticeable way, or 25 electric vehicles could be charged slowly over the course of an eight-hour work day rather than simultaneously, and quickly, when they are all plugged in at the start of the work day.

The redundancies offered by diversified portfolios, microgrids, battery storage, and smart infrastructure are even more important for isolated grids, such as those in Hawaii and Alaska, that cannot buy energy from other grids when their supplies run short. “It does allow for a certain amount of integrity within,” Tome says. “If we’re going to experience a technical problem, it will probably be one of our own making.”

In Hawaii, where each island operates its own independent grid, battery storage in conjunction with renewable energy is crucial to ensuring a more even supply, according to Tome. The state has met its RPS goal of being 30 percent renewable by 2020 and plans to reach 100 percent by 2045, Tome says. Solar, wind, and geothermal are all being used in the state along with energy storage systems, and research into alternate sources of renewable energy is ongoing, she says.

“If you are looking at the potential for the future, there are a lot of possible synergies,” Tome says. “Wave energy is an area of interest, but it’s not being commercially bid into any of the renewable-energy combos at the moment. I could see, especially with global climate change … as we begin to look at devices to manage situations at the coast, if you’re building something along the shoreline to divert or reduce the impact of the waves on the land, why not capture that energy somehow? You could be protecting your shoreline and capturing energy at the same time.”

“The next big technology is offshore wind, which is becoming a lot more popular in the U.S., providing renewable energy without the need for land,” says Molner. “The wind is typically much stronger over bodies of water, resulting in increased power production and efficiencies.” 

One example of diversification that also incorporates offshore wind is the Coastal Virginia Offshore Wind pilot project by Dominion Energy. The project will include two 6 MW wind turbines located approximately 27 mi off the coast of Virginia Beach. The turbines are expected to provide power to 3,000 homes at peak output. The construction is a steppingstone to a 2,600 MW commercial-scale offshore wind development that will provide energy to up to 650,000 homes. 

Both projects are part of Dominion Energy’s commitment to having systems that can provide 3,000 MW of solar and wind energy in development or fully operational by 2022, according to the project’s website. The first two pilot turbines will be operational later this year and are the first offshore wind turbines to be located in federal waters, according to the energy company. (The first offshore wind farm in the United States was the Block Island Wind Farm off the coast of Rhode Island, which came online in 2016). 

Dominion has also received approval from its State Corporation Commission to move forward with four battery-storage pilot projects that will offer combined storage of 16 MW. The battery storage will be used in conjunction with the state’s wind- and solar-generating fields to maintain reliable energy service to its customers, according to the utility’s website.

Vineyard Wind, off the coast of Massachusetts, is another utility-scale offshore wind project that is currently in development. It will be located 15 mi off the coast of Massachusetts and, as currently planned, will generate power for 400,000 homes and businesses using large turbines that can each potentially generate at least 9.5 MW of power. The wind field could be operational as soon as 2023, and Massachusetts hopes to have 3,200 MW of offshore wind operational by 2035. The latter is the equivalent of 20 percent of the electricity used within the state, according to the Vineyard Wind website.

In general, larger turbines “will provide for more energy production and allow for less variability, more reliability, and easier integration into the grid,” Molner says. The larger rotors are able to capture more wind and at higher elevations, which increases their production. “Lower-elevation turbines are not able to capture or harness that same amount of wind energy as much as the larger and higher-elevation turbines are,” he says.

The Vineyard Wind turbines will be located in water between 35 and 45 m in depth and will be fixed to the seafloor. The turbines’ siting is still being designed to ensure that concerns from local fishers and the U.S. Coast Guard are fully considered. But, as Rasmus Miller, the engineer-procure-construct director for Vineyard Wind, is quick to point out, care is being taken with the environmental considerations. “Why make a green future if you are just going to be destroying something else? That’s not in our DNA,” he says. 

The Vineyard Wind project, being the first of its size, is also helping to get the United States’ large-turbine offshore wind supply chain up and operating, he says. “When the industry started, it was much simpler because everything was smaller, but it was also much more expensive. Today we have highly specialized turbines that have a wingspan (of) … 200 meters,” he says. Coordinating the availability of ships that can handle the transportation of material and construction of these enormous turbines is one of the challenges being faced, but Miller is confident that the supply chain in the United States will become established and more offshore projects will be built once that is the case.

“I think that this first project will serve as a catalyst for all the ambitious goals that the government is supporting along the eastern seaboard,” Miller says.

This article first appeared in the October 2020 issue of Civil Engineering.