As renewable energy sources such as wind and solar become a larger part of the overall United States’ energy portfolio, energy producers and system operators have an opportunity to take advantage of expanding options to introduce renewable energy to the power grid.
Renewable energy is one of the fastest-growing energy sources in the United States. Total annual electricity generation from wind power in the United States increased from about 6 billion kilowatt-hours (kWh) in 2000 to about 338 billion kWh in 2020, according to the U.S. Energy Information Administration.
During the past decade, solar power has grown at an average rate of 42% annually, resulting in more than 89 gigawatts of solar capacity in place today across the United States, according to Solar Industry Research Data.
Read part 1 of our white paper- 2021 Power Generation and Renewable Energy Trends, to learn how fossil-based power generation technologies are rapidly evolving and renewable technologies are being scaled to meet the demands of the 21st-century market.
The rise of renewable energy is a result of many factors, including a favorable regulatory environment, technological advancements, and increased demand for clean energy in electricity markets.
As this trend continues to grow, solutions to accommodate the fluctuating supply and demand associated with variable renewable energy--from utility-scale wind farms to residential rooftop solar panels--become critical. A solar installment or wind farm that can capture and monetize oversupply is more efficient. In fact, experts in a YaleEnvironment 360 article have described energy storage as the true bridge to a clean-energy future.
Utility-scale batteries are used to store and distribute energy, increasing reliability and resilience for energy producers. Due in part to advancements in technology, the cost of utility-scale battery storage has dropped dramatically in recent years nearly 70% between 2015 and 2018, according to the EIA. The EIA predicts battery storage will increase by nearly 7,000 MW in the near term.
Customer and third-party-owned distributed energy generation and storage units are also becoming more common. Single-family households are installing rooftop solar panels. Microgrids are serving university campuses with small wind turbines. Large hospitals are generating electricity with a reciprocating engine combined heat and power (CHP) system for its own heating, cooling, and electricity.
As these trends continue to grow, the implications for existing energy grids become more complex. Connecting solar, wind, and other utility-scale renewable energy sources into the grid are difficult in part because current grids are designed for a centralized distribution model. Grids built decades ago were not designed to efficiently accommodate widely distributed generation.
The United States electricity grid is aging. According to the U.S. Department of Energy, 70% of the U.S. electrical grid’s 160,000 miles of high-voltage transmission lines are more than 25 years old. Many transformers that either step up or step down the voltage to accommodate distribution are roughly the same age. Other components still in operation were installed more than a century ago.
While the grid has served energy needs well for decades, today’s energy demand does not resemble the needs that drove its initial design, or the needs that have emerged since its mid-century expansion. Today’s energy consumption has grown more complex, straining the capabilities of the grid.
Electric utilities have increasingly invested in replacing and modernizing this aging infrastructure. The U.S. publicly owned electric utilities spent an estimated $52 billion on electricity transmission and distribution infrastructure in 2019, representing about half of the total capital expenditures.
This investment in modernization is in part driven by the need to accommodate grid integration of renewable energy sources.
One way in which renewable energy systems are connecting to the grid is through smart grid technology. Smart grids enable the efficient integration of renewable energy sources, critical for the transition to clean energy.
In modernizing the energy grid, smart grid digital technologies are being deployed across the transmission and distribution system to help grid operators improve operational efficiency, reliability, flexibility, and security, and to reduce electricity consumption. Rather than replacing elements of the existing grid, smart grid technologies improve efficiency by digitalizing, upgrading, and expanding the current electrical grid.
Smart field devices and sensors are key elements of smart grid technology. These monitor processes, communicate data to operations centers, respond to digital commands, and adjust processes automatically. In modern smart grids, Phasor Measurement Units help operators assess grid stability. Advanced digital meters provide information to consumers and automatically report outages. Relays automatically sense and recover from faults in substations and automated feeder switches reroute power around problems. Batteries store excess generated electricity, accessible on-demand to the grid.
To further enhance smart grid capabilities, communications networks share data among devices and systems, while information management and computing systems process, analyze, and help operators access and apply data coming from the grid.
Another growing technology for grid integration of renewable energy sources is high-voltage direct current (HVDC). Electrical grids have long been based on alternating current (AC). In the early days of electricity, transformers could reduce AC voltages, but nothing similar existed for making direct current (DC) safe for residential use. With technological advances, however, this has all changed. During the past two decades, numerous HVDC transmission systems have been built throughout the world. These are long-distance lines carrying DC electricity that are separate from the AC transmission lines in the grid.
HVDC power systems transmit electricity over long distances more efficiently. Transmitting AC at lower voltages increases resistance in the transmission line conductors. Resistance generates heat, resulting in the loss of electricity as it travels through the line. Over long distances, the cost of power loss over high-voltage AC power lines exceeds the added cost of the HVDC converter stations over the lifetime of the system. This breakeven distance has been estimated at 800 km (500 miles) for overhead lines and 50 km (31 miles) for underground and undersea cables.
This means it can be more cost-efficient to transmit electricity over DC rather than AC power lines when the customers are consuming electricity hundreds of miles from where the power is generated. Renewable energy sources such as wind farms, large solar arrays, and hydroelectric power are often great distances from the population centers they serve.
HVDC systems are helping countries around the world advance toward renewable energy grid interconnection. The United States has 20 HVDC systems in operation, including a 3,100 MW capacity line that transmits electricity 845 miles from Oregon to the Los Angeles area. China, a leader in this technology, is in the process of building a massive national electrical grid based on a hybrid system of UHV (ultra-high voltage) DC lines for power transmission from its provinces in the north and west and an AC network for distribution to its population centers near the eastern coast.
From transmission and distribution applications to energy storage solutions and power conversion systems, Parker offers a wide range of solutions on the leading edge of the grid modernization trend.
To learn more about power transmission and distribution, read our white paper 2021 Power Generation and Renewable Energy Trends – Part 1.
The article was contributed by the Filtration and Energy Teams.
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