According to Iberdrola repowering a wind
farm “mainly consists of replacing (partially or totally) the old turbines
with more powerful and efficient models using the latest technology. Repowering
can multiply the generating capacity of a wind farm and significantly increase
electricity production. The reason is simple: each new turbine produces more
energy than the old ones and therefore fewer units are needed. According to
data from EoLIS 2022, WindEurope's annual event, on average, repowering reduces
the number of turbines in a wind farm by a quarter, while increasing the
installed capacity of the wind farm by a factor of 2.7 and tripling its
electricity production.”
There are
several reasons that repowering wind farms have become more profitable including
technology and efficiency improvements, turbine size increases, more output per
turbine, inefficiency of older wind farms with low-tech turbines deployed in the
best wind conditions, electricity demand and prices, and regulatory incentives.
The benefits
of repowering wind farms vary by site and include increased production capacity,
efficiency improvements, cost reduction, improved grid integration, preservation
of employment, and increasing low-carbon electricity.
Wind and solar
power both have large land footprints and to be able to get more power out of
the same amount of land with upgraded and repowered projects is desirable.
According to the DOE, this is sort of equivalent to a brownfield/greenfield
situation: “Wind repowering enables owners to retrofit power plants on
existing sites with new and/or refurbished technology, including erecting
taller, more efficient wind turbines to increase productivity. Repowered
projects can often gain further cost-saving advantages, relative to new
greenfield (or vacant-lot) developments, by using existing grid connections and
infrastructure.” They also mention wind-heavy Denmark which has some very old
wind projects still producing and who has been repowering those projects with better
tech for many years. In 2019 wind repowering in Denmark represented a staggering
86% of gross added capacity and 87% of added wind turbines. From 2012 through
2019 Denmark had a 1.3 GW gain in capacity and a reduction of 109 wind turbines
through repowering projects. Other repowering considerations in Europe and everywhere
else for that matter include the benefits of reducing noise emissions, better
aesthetics, and political considerations.
Wind Tech Advancements: Bigger is Better and More
Height and turbine
size increases have led to wind power efficiency improvements. Specifically, hub
height and rotor diameter increases are the big factors in improving efficiency.
Hub height refers to the distance from the ground to the hub of the turbine. According
to the DOE: “hub height for utility-scale land-based wind turbines has
increased 73% since 1998–1999, to about 98 meters (~322 feet) in 2022. That’s
taller than the Statue of Liberty! The average hub height for offshore wind
turbines in the United States is projected to grow even taller—from 100 meters
(330 feet) in 2016 to about 150 meters (500 feet), or about the height of the
Washington Monument, in 2035.”
Higher towers for wind turbines mean stronger higher altitude
winds can be captured. Higher altitude winds have less friction from ground
elevation variations, tall trees, and other land obstacles. As the figure below
shows, most of the taller wind turbines are deployed in the windy areas of the
Midwest and the hilltop elevations of the Northern Appalachian Mountains. Hub
heights have increased fairly steadily for over a decade.
Rotor diameters
have also increased steadily through the past decade. According to the DOE: “Back
in 2010, no turbines in the United States employed rotors that were 115 meters
(380 feet) in diameter or larger. In 2022, the average rotor diameter of
newly-installed wind turbines was over 130 meters (~430 feet)—longer than a
football field, and almost twice the wingspan of a 747.” A few days ago, I heard about a planned deployment
of a wind turbine with a rotor diameter of around 900 feet. Longer turbine
blades can capture more wind at any wind speed, including slower speeds.
According to DOE: “Being able to harvest more wind at lower wind speeds can
increase the number of areas available for wind development nationwide. Due to
this trend, rotor swept areas have grown around 645% since 1998–1999.”
Two drawbacks
of larger turbine blades are transportation and installation challenges. Longer
blades and taller tower sections are difficult to transport, especially around
turns, under bridges, and highway overpasses. They can also be more difficult to
install. These problems are being addressed.
The largest
wind turbine in the world became operational in 2023. It’s an offshore turbine,
“the MySE 16-260, built by Mingyang Smart Energy for the China Three Gorges
Corporation. It’s now operational and contributing to the power grid in China.
Here are some impressive stats about this colossal turbine:
Rotor diameter: 260 meters (853 feet)
Swept area: 53,902 square meters (580,196 square feet)
Power output: 16 megawatts
Tower height: 152 meters (499 feet)
Generator weight: 349 metric tons (385 US tons)
Expected annual energy production: Around 66
gigawatt-hours, enough to supply approximately 36,000 homes.
Wind Repowering Economics
A new report
by Enverus concludes that wind repowering is gaining momentum. With significant
cost increases for wind projects due to inflation and the cost of borrowing,
more wind repowering projects are seeing better upsides than new builds. Choosing
to repower over building new reduces capex and operation and maintenance costs and
increases power production. Another advantage of repowering can be the ability
to do it while keeping existing premium-priced power purchase agreements (PPAs)
that have remaining time on the term of the agreement. Enverus quotes subsidiary
Enverus Intelligence Research (EIR) VP Scott Wilmot: “Depending on PPA
price, repower economics can be preferable to a new build if a 5% capacity
factor gain can be realized. This is a low benchmark to clear given the turbine
efficiency gains and degradation we have observed. Projects older than 12 years
(pre-2012 vintage) can realize capacity factor gains of 10%-20% through a
repower — this makes repowering an easy economic decision,” Wilmot said.
Enverus also reports that the current repowering
capacity at 7GW is about equal to new-build wind projects under construction. They
also note that EIR identified 261 potential targets in its database
representing almost 21,000 MW. Thus, it appears that wind repowering will
continue to compete strongly with new builds. “Wind developers plan to add
some 6.5-7.5 GW of energy to the grid through repowering projects in 2024. That
means 2024 could tie 2019 for the most repowering projects in a single year.”
Another advantage to repowering over new builds is that the interconnections
are already there, as are the roads, prepared sites, permitting and regulatory
approvals, and some other infrastructure. Wilmot predicts that wind repowering
will continue to proliferate in the near to midterm as its economics continue
to look better than keeping older underperforming projects online.
The fact that
wind repowering can happen fast, much faster than new builds, and can significantly increase the power output
of a wind farm also means that it can quickly increase revenues not just for the
developers but also for those who lease the land to them, who will also benefit
from longer terms.
Stranding Some Assets Early Can Be Profitable
Wind
repowering is one example that shows that stranding some of these
underperforming and inefficient (according to modern standards) projects can be
economically wise. This is especially true for renewables that can still
receive new production tax credits since they have been extended for another
ten years in the U.S. Wind repowering also addresses land scarcity and mostly bypasses
public opposition to new projects. These advantages can tip the scales and result
in repowering being more economical than keeping older and inefficient projects
online. Thus, early retirement of those original assets is a net benefit.
References:
The
upside of repowering wind: Why developers may blow new life into existing
onshore over new builds. Enverus. January 31, 2024. The
upside of repowering wind | Enverus
Repowering
will represent nearly half of all new wind capacity in 2024: Enverus. Emma Penrod.
Utility Dive. February 22, 2024. Repowering
will represent nearly half of all new wind capacity in 2024: Enverus | Utility
Dive
Repowering
of wind farms: Do you know what repowering of wind farms is and how it is
carried out? Iberdrola. Repowering
of wind farms - Iberdrola
Wind
Turbines: the Bigger, the Better. Liz Hartman. U.S. Dept. of Energy. Office of
Energy Efficiency & Renewable Energy. August 24, 2023. Wind
Turbines: the Bigger, the Better | Department of Energy
The Largest and Most
Powerful Wind Turbine Ever Built Is Now Operational. David Nield. Science Alert.
July 24, 2023. The
Largest And Most Powerful Wind Turbine Ever Built Is Now Operational :
ScienceAlert
Wind Repowering Helps Set the Stage for Energy Transition. U.S. Dept. of Energy. Wind Technologies Office.June 2, 2021. Wind Repowering Helps Set the Stage for Energy Transition | Department of Energy
Wind repowering: Unveiling a hidden asset. H. Doukas, A. Arsenopoulos, M. Lazoglou, A. Nikas, and A. Flamos. Renewable and Sustainable Energy Reviews. Volume 162, July 2022, 112457. Wind repowering: Unveiling a hidden asset - ScienceDirect
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