Wind Energy Curtailment: Historical Case Study

Abstract

Currently, renewable energy projects are growing, and one of the critical unforeseen consequences that has emerged is curtailment. This study focuses on characterizing a full dataset of real operational curtailed electricity from wind energy projects in one-hour time steps, obtained through Supervisory Control and Data Acquisition over the years 2022 and 2025 of operation in Chile. The case study is based on the national electrical system of Chile, and the analysis incorporates both curtailment patterns and more significant features. These results can ultimately be used as an input source for annexed projects, such as energy storage systems or green hydrogen production. The total installed capacity increased from 3.0 GW to 5.0 GW during this period, representing a 66% expansion, while energy generation increased by only 22%. Curtailed energy increased from 7% to 13% of total potential output, equivalent to approximately 3.4 TWh of unused clean energy. Location analysis reveals that around 60% of generation and curtailment occur in northern Chile, where grid congestion is most pronounced. Monthly trends show a pattern that combines a linear upward increase associated with growth in installed capacity and a cyclical seasonal component driven by resource variability. These findings highlight that curtailment has become a structural limitation for renewable integration, primarily due to insufficient transmission expansion and system flexibility.

1. Introduction

The worldwide expansion of variable renewable energies (VRE), particularly wind and solar sources, has been accompanied by an increase in the magnitude and frequency of curtailed energy [1]. Curtailment refers to the reduction of energy output when generation exceeds demand or grid capacity constraints. As such, a portion of the energy is not utilized, even when it is available. From an economic perspective, excessive curtailment reduces the revenue potential of renewable projects, which can discourage further investment in renewable technologies. Environmentally, it leads to a loss of clean energy that could otherwise displace fossil fuel generation, thus increasing carbon emissions. For grid operators, managing curtailment adds complexity to grid operations and requires advanced forecasting and real-time balancing capabilities [2].

The curtailment of renewable energy has been widely studied in the literature. Bird et al. [3] provided an early review of experiences in different countries, showing that generation curtailments exceeded 10% in some cases, mainly due to transmission constraints and institutional factors. Similar conclusions were reported by O’Shaughnessy et al. [4] in their study of global curtailment trends in key markets (Chile, China, Germany, and the USA), highlighting transmission constraints and temporary mismatches between supply and demand as determining factors. Yasuda et al. [5,6] developed a global comparative tool that allows relating renewable penetration levels with generation reduction rates known as the C-E map, facilitating historical analysis and comparisons between different countries. These studies have shown that curtailment is a characteristic of electrical systems with high renewable penetration, primarily influenced by transmission capacity and system flexibility. López et al. [7] analyzed the dynamics of curtailment in California, detailed in 1 h time steps, showing how the simultaneous penetration of variable and conventional generation increases the reduction rates, although with a moderate impact on the levelized costs of electricity, which reinforces the need to evaluate both its causes and its economic effects.

Chile represents a particularly relevant case in this context. Over the past decade, the country has experienced an accelerated increase in the penetration of variable renewable energy. In 2013, the energy generated by solar or wind sources accounted for less than 1% of the total generation [8] whereas, by 2024, their participation had grown to 41% [9]. Additionally, VRE projects under construction represent an additional 2500 MW of capacity, with 178 further projects in evaluation by the Environmental Assessment Service [10]. At present, Chile is one of the markets with the most competitive cost of electricity [11,12,13] and has been projected to be an important producer of green hydrogen [14,15,16,17]. This evolution underscores the expansion of VRE in Chile, consolidating its role as a central component of the energy transition of the country.

In parallel with the VRE expansion, curtailment has become one of the main challenges for renewable integration in Chile. The country presents a marked geographical imbalance between the location of renewable resources and electricity demand. Most wind and solar potential is concentrated in the northern regions, while demand is primarily located in the central zone. To mitigate this mismatch, the northern and central power systems were interconnected in 2017, producing a significant and immediate reduction in curtailment. Levels fell from around 14% that year to approximately 2% a few years later [18,19]. However, this improvement proved temporary since curtailment has experienced a consistent and explosive increase in recent years. While curtailed energy was 453 GWh in 2021, curtailment from VRE reached 5900 GWh in 2024 [18]. This increment exposes a structural problem in the integration of more renewable energy, highlighting the need for enhanced grid management strategies to accommodate the VRE supply. In terms of curtailment, the relevance of wind projects is not completely understood, as it is either studied by coupling it with solar projects or analyzed in cumulative time frames; namely, monthly or yearly trends [2,18,20,21,22]. There is no general rule on which VRE (wind or solar) has a larger contribution to total curtailment [3,5,7]. Nevertheless, the recent steep increase in maturity of storage technology [23,24] or coupled projects that take advantage of such resources [25,26] make it attractive to unveil the full potential of this type of VRE.

Although curtailment of energy from VRE sources has been extensively studied worldwide, most research has focused on combined solar and wind curtailment, limiting insights into system-specific renewable integration. In Chile, where wind energy penetration has rapidly increased, no comprehensive assessment based on actual operational data has been reported. This study addresses this gap by analyzing a large dataset of real-time generation and curtailment exclusively from wind parks within the Chilean National Electric System (SEN). The analysis includes normalized metrics, temporal curtailment patterns, and seasonal trends. These trends are contextualized within both local and international frameworks, providing a valuable data-driven resource to inform future energy applications. Additionally, this work delivers an open-access, reproducible dataset to support subsequent techno-economic and policy analyses.

The rest of the article is organized as follows. Section 2 provides details of the dataset and gives an overview of the case study while describing the methodology applied in the analysis. The results and more relevant patterns are discussed in Section 3, and the study is concluded with final key remarks in Section 4.

2. Data and Methods

2.1. Generation and Curtailment

This research uses data from Chilean wind energy parks. The generated [27] and curtailed [28] electricity values are sourced from the operational documentation of the National Electrical Coordinator (CEN). A time-resolved database of wind energy generation and curtailment with 1 h intervals has been constructed. The raw data are obtained from the CEN’s Supervisory Control and Data Acquisition (SCADA) system. Data validation is performed by checking for negative values and overshoot conditions—that is, cases where generation and curtailment exceeded the nominal capacities (NEP) across the complete dataset. The latter resulted in no data being discarded. Figure 1a presents, as an example, the energy generation profile for the Tchamma wind park over the entire timeline, while Figure 1b depicts the curtailed electricity for the same period.

This study collects additional information from technical sources [29]. Raw data for each wind energy park can be downloaded by name; alternatively, the code-format database used in this work is accessible via its public repository (https://github.com/RSotoValle/WindGenandCurtChile (accessed on 16 November 2025)).

Table 1. Sample of information from each wind energy park [29].

Item	Information
ID	1
Wind park name	Tchamma
Region, code	Antofagasta, AN
City	Calama
Net effective power, NEP	171.78 MW
East coordinate, UTMWGS84	492341
North coordinate, UTMWGS84	7511625
Officially operative since	21.02.2022

presents an example of additional park-level data in addition to energy-related information.

A total of 51 wind farms are evaluated over a 42-month period, spanning from January 2022 to June 2025. The combined installed capacity amounts to approximately 5054 MW. Additionally, comprehensive energy generation data for the entire Chilean SEN—including hydroelectric, solar, thermal, and other sources—are obtained from the annual reports of the CEN [30,31,32,33], which allows allocation of each generation plant’s share. This count of wind parks excludes projects classified as small and medium generation (<9 MW). To illustrate the level of representativeness,

Table 2. Contribution of the wind park sector in Chile and this study [30,31,32].

Contribution/Year	2022	2023	2024
Total energy, $E_T$ [GWh]	83,005.3	83,637.1	85,519.0
Total wind share [GWh]	8832.1	9911.1	11,083
This study, G [GWh]	8635.7	9699.3	10,549
Representativeness	97.8%	97.9%	95.2%

shows the total energy generation, the overall share of wind power, and the contribution of the 51 wind farms analyzed in this study, which consistently accounts for more than 95%.

2.2. Methodology

The methods used to analyze the data are presented. First, the data is clustered to perform different analyses in terms of hours, days, months or the full cumulated energy through the timeline and in three groups; namely, potential energy (E), generation (G) and curtailed (C) electricity according to Equations (1)–(3), respectively.

$$\begin{array}{c}{E}_i={NEP}_i·T,\end{array}$$

(1)

$$\begin{array}{c}{G}_i=\sum _{j\in T}{G}_j,\end{array}$$

(2)

$$\begin{array}{c}{C}_i=\sum _{j\in T}{C}_j,\end{array}$$

(3)

where i is the corresponding wind park, and T is the cumulated time, which can be by 1 day, 1 month or the complete 42 month dataset. Additionally, global trends are analyzed by means of the average of each concept as shown in Equation (4).

$$\begin{array}{c}\overline{{\chi }_i}={\displaystyle \frac{1}{N_T}}\sum _1^{N_T}\sum _{j\in T}{\chi }_j,\end{array}$$

(4)

where, $\chi$ can be E, G or C and $N_T$ is the number of analyzed periods; i.e., by months $N_T=42$ or by days $N_T=1277$. It is important to mention that at the beginning of the study—January 2022—there are 34 projects (∼3048 MW) in operation while by the end of it—June 2025—another 17 (∼2006 MW) were gradually incorporated in the generation and curtailment data according to the operation date (see Table 1). Therefore, $N_T$ only considers when each wind park is actively in operation.

Additionally, the wind share is defined as the percentage obtained from the wind generation, G, over the complete electric energy dispatched in the Chilean SEN, $E_T$, according to Equation (5):

$$\begin{array}{c}p={\displaystyle \frac{G}{E_T}}.\end{array}$$

(5)

Finally, the curtailment ratio r is calculated to evaluate the proportion of curtailed over the available potential energy [3,4,6,7], according to Equation (6):

$$\begin{array}{c}r={\displaystyle \frac{C}{C+G}}.\end{array}$$

(6)

3. Results and Discussion

The results are presented at three levels: (1) cumulative analysis of energy quantities (potential, generation, and curtailment); (2) localized characterization across temporal clusters to establish behavioral patterns, supplemented by statistical quantification of the case study; and (3) international-scale comparison. For conciseness, only the most significant findings are presented, with each topic discussed sequentially. The complete dataset is made available in the public repository (https://github.com/RSotoValle/WindGenandCurtChile (accessed on 16 November 2025)). to ensure reproducibility and enable further analysis.

During the 42 months of the study, a maximum available energy of approximately 128.7 TWh is estimated following Equation (1), using NEP and the contribution period of operation of each wind park. Analogously, a total energy of 34 TWh and 3.4 TWh represents generation and curtailment, respectively (Equation (4)). Figure 2 shows the distribution of such energy magnitude over the different regions in the study case.

The areas with the highest penetration of wind energy are also those with the highest levels of curtailment. As shown in Figure 2a, from the 51 wind parks analyzed, the largest contribution is located in northern Chile (∼60%), while a significant remaining proportion (∼36%) is from the south region, mostly skipping the central part of the country. In this distribution, the relative share of nominal installed capacity in a region is proportionally reflected in the generated and curtailed energy in the same area (Figure 2b). This trend aligns with findings in other worldwide electrical distributions, where regions with high VRE penetration exhibit high curtailment levels [1,3,7,34,35]. It is remarkable that the low performance between the potential energy and real generation magnitudes (0.26) is within the low-performing wind energy capacity factor range [36,37,38,39].

The concentration of curtailment in northern Chile is directly associated with the spatial mismatch between the centers of generation (north) and consumption (center). This imbalance favors the transmission congestion within the SEN. Indeed, the main 220 kV and 500 kV corridors that connect the northern and central regions operate close to their thermal and security limits, particularly under the N-1 contingency criterion, which requires the system to remain stable even after the unexpected loss of a single transmission element. This operational condition effectively reduces the transfer capacity available for north–south energy flows during periods of high wind generation and low local demand [20,40]. This bottleneck is recognized as a structural cause of renewable curtailment, and the delayed implementation of network reinforcements has maintained these constraints [20].

Global results reflect some of the trends in the timeline of the case study. Consequently, the clustering of the energy accumulation for each of the 42 months is presented in Figure 3. Although the installed power increased by 66%, there is an unmarked increment in generation; in fact, the generation over January 2022 is roughly 800 GWh while, by the same month three years later, it increased to 975 GWh—only a 22% increase. In contrast, curtailment shows a qualitative progressive increment; indeed, it exhibits a 176% increment in the same time threshold as generation. The total curtailment corresponds to 3.4 TWh, distributed as 0.64 TWh in 2022, 0.84 TWh in 2023 and 1.45 TWh in 2024, corresponding to 68, 56 and 71 million USD, respectively, based on the monthly average marginal cost [30,31,32] in the period examined. These results are complemented by recent technical studies that have monitored the curtailment from VRE in Chile, coupling solar and wind [20].

Figure 4 presents the monthly evolution of the curtailed energy ratio (Equation (6)) alongside the progression of nominal installed capacity. The analysis reveals two superimposed dynamics: an increment trend and a seasonal cycle. The increasing component reflects a proportional relationship between installed capacity (NEP) and curtailment, indicating a systematic coupling amenable to parameterization. The seasonal component, driven by periodic climate variations, exhibits pronounced peaks during warm months and minima during cold months. These coupled behaviors underscore the nonlinear interaction between capacity expansion and environmental forcing. The data show a consistent installed capacity increase of 22% by year, whereas the annual average curtailment ratio increases by 6.8%, 7.4%, and 12% across the 2022, 2023 and 2024 observation periods, respectively. This decoupling arises because capacity growth does not follow seasonal patterns, resulting in misleading system-level inferences. Consequently, individual wind park assessments are necessary to isolate seasonal effects and ensure comparability across installations.

For comparison, it is useful to contrast these results with international experiences, such as the case of California. Between 2015 and 2021, wind curtailment in California remained below 5%, following a generally downward trend with peaks occurring during the warmer seasons, particularly in the early years of the period [7]. Over the same timeframe, installed wind capacity showed moderate variation, declining from 6108 MW to 5609 MW between 2015 and 2017 before increasing again to 6142 MW in 2021 [41]. In contrast, annual wind curtailment in Chile has risen steadily, from 7% to 13% over the past three years (2022–2024), alongside substantial growth in installed capacity. Despite these differing trajectories, data from both regions indicate a consistent link between installed capacity and curtailment, confirming that curtailment tends to increase in parallel with capacity expansion when grid adaptation is limited.

Figure 5 presents the C–E map, which plots the relationship between curtailment ratio and wind penetration. The map also enables comparison across different time horizons, emphasizing evolving trends. A selected group of countries is highlighted to illustrate the most relevant patterns and behaviors, reported by Yasuda et al. [6], in relation to the study case. For instance, some European countries have maintained wind curtailment levels under control despite their high share in the generation mix. Countries like Germany, Denmark, and Spain have curtailment rates below 5%, even though their wind power penetration ranges from 15% to 30%. This performance is explained by a combination of factors, including a robust transmission network, high interconnection capacity with neighboring countries, and the availability of thermal power plants with high operational flexibility. Conversely and similar to the current state of the Chilean system, countries such as China, Italy, and the United States have experienced significant increases in curtailment due to the spatial mismatch between the centers of generation and consumption, leading to transmission congestion. These countries have significantly reduced curtailment levels (between 2010 and 2019) through various measures. In Inner Mongolia (China), curtailment shows two significant increases (Figure 5). The first was due to the rapid expansion of wind power capacity, which exceeded the available infrastructure, and was mitigated by a massive expansion of the transmission network. The second was associated with the low flexibility of coal power plants, a problem addressed through conversion programs to improve their operational responsiveness. Furthermore, priority dispatch policies for renewable energy sources were implemented, which helped to reduce curtailment.

In Italy, the concentration of wind power generation in the south compared to demand in the north resulted in congestion episodes that were mitigated by reinforcements to the transmission infrastructure, along with the adoption of dynamic line rating. In the United States, regions such as ERCOT face similar constraints due to the imbalance between wind power generation in the Panhandle and demand in east-central Texas, which has driven targeted investments in transmission. The Irish electricity system, which is relatively isolated and with limited interconnection capacity, faces significant operational challenges under conditions of high wind power penetration. This combination limits the availability of external support and requires managing most stability requirements internally, particularly due to the non-synchronous nature of wind generation. To supervise and control the instantaneous share of generation without physical inertia, the system non-synchronous penetration indicator is employed. When this indicator exceeds the operational limit established, wind curtailment is applied to restore secure operating conditions. Initially set at 50%, this limit has been progressively raised through technological and operational enhancements implemented under the “Delivering a Secure, Sustainable Electricity System” (DS3) program, reaching 65% in 2020 and projected to increase further in the coming decade [20]. Hence, international comparisons reveal that the transmission infrastructure, regulatory environment and operational flexibility of each electricity system influence the evolution of curtailment.

For completeness,

Table 3. Overview of curtailment causes and regulatory responses by country and world sector. Synthesized and modified from [6].

Group	Country	Curtailment Causes	Policy & Regulatory Actions
Europe	Denmark	Geographical mismatch between generation and demand; Static Thermal Rating Limitation; Low inertia system condition	Transmission expansion;Implementation of dynamic line rating; Increase of System Non-Synchronous Penetration operational limits
	Germany
	N. Ireland
	Ireland
	Italy
	Spain
	UK
North America	SPP	Geographical mismatch between generation and demand	Transmission expansion; Storage
	ERCOT
	MISO
	CAISO
	NYISO
	ISO-NE
	PJM
China	Mongolia	Geographical mismatch between generation and demand; Competition between different energy sources; Thermal fleet inflexibility	Transmission expansion; Shift installation to demand centers; Retrofit program for existing coal plants; Priority access policies
	Xinjiang
	Gansu
	Jilin
	Shanxi
	Yunnan
Chile		Transmission congestion between north and center; Low flexibility;Demand concentration	No priority dispatch;Delayed implementation of flexibility mechanisms

provides a summary of the comparative cases from regions that have experienced notable increases in curtailed wind energy, along with the corresponding mitigation measures adopted. The dataset consolidates information reported by Yasuda et al. [6] and the present study.

To address the curtailment problem, Chile is implementing measures aimed at mitigating its structural causes. Given that the primary constraint is associated with transmission capacity, several expansions within the National Electric System are currently planned. These include the 1400 km Kimal–Lo Aguirre HVDC line and new 500 kV corridors connecting Antofagasta, Atacama, and Coquimbo. These projects are expected to increase north–center transfer capacity and progressively reduce structural curtailment [20,42]. However, beyond technical and infrastructure-related constraints, non-technical factors also influence curtailment dynamics in the SEN. The Chilean electricity market operates under a centralized dispatch model based on marginal cost optimization, where variable renewable generators compete with conventional sources [11]. Although the regulatory framework guarantees non-discriminatory access to the grid, in practice, the absence of effective priority dispatch for renewables and limited market signals for flexible consumption or storage can exacerbate curtailment during periods of low demand and transmission congestion. Additionally, delays in implementing flexibility mechanisms designed to reward rapid response from generation, storage, or demand-side resources reduce incentives for storage investment and demand response participation [43]. Therefore, mitigating wind curtailment in the SEN requires not only physical expansion of transmission capacity but also regulatory adjustments that better align market operations with the variability of renewable generation.

Overall, in the case study, nominal capacity, generation, and curtailment are distributed in broadly comparable proportions across Chilean regions. Nonetheless, total curtailment has expanded its ratio over the past three years (2022–2025), contrasting with the evolution observed in other markets. This pattern is primarily driven by the rapid increase in installed capacity, which has not translated into a proportional growth in effective generation. The evidence suggests that Chile is entering a critical stage in which curtailment is likely to rise further, as mitigation strategies remain at an incipient level of development. With installed capacity expected to nearly double once pending projects commence operation, the system faces growing challenges in balancing renewable integration with grid flexibility—underscoring the urgency of implementing coordinated adaptation measures before curtailment reaches structurally unsustainable levels.

4. Conclusions

This study focuses on real generation and curtailment data from 51 wind parks in Chile. First, a characterization of the total energy and nominal effective power was performed considering the whole accumulation between January 2022 and June 2025. Subsequently, particular focus was placed on the timeline of events between capacity increase and the performance metrics of generation or curtailment.

In terms of the relationship between installed, generated and curtailed energy, the results show a strong geolocation correspondence between wind penetration and levels of curtailment percentages, reflecting a resource distribution that exceeds the effective utilization capacity of the electrical system. In fact, curtailed energy increased from 7% to 13%, while installed capacity grew by 66%, indicating that transmission and operational constraints are the main limitations to renewable integration. The sustained growth in curtailment represents an effective reduction in the wind capacity factor, mainly caused by grid congestion in northern regions and insufficient flexibility in the national electric system.

There is evidence of a sustained upward trend in wind curtailment in Chile, associated with the rapid growth of installed capacity and the limited capacity of the electrical system to absorb such expansion. Furthermore, the monthly analysis reveals a coupled pattern mixed up with the upward trend; namely, a cyclic seasonal behavior. This combination demonstrates that, although operating conditions can fluctuate throughout the year, the sustained increase in wind capacity remains the main factor driving the rise in curtailment when grid adaptation is limited. From a system-planning perspective, the consistent increase in curtailed electricity ($r=C/(C+G)$) underscores the need to strengthen transmission infrastructure and implement flexibility-enhancing measures, such as storage, demand management, and wind-to-hydrogen integration. Without these actions, a significant fraction of clean generation potential will continue to be lost.

Regarding the wind capacity factor, the increase in curtailment in Chile implies an effective reduction in the capacity factor of wind sources due to a mismatch between renewable expansion and grid capacity, once more confirming that limitations in transmission and operational flexibility are critical factors restricting the efficient integration of wind energy. The open-source dataset generated in this work provides a reproducible foundation for future techno-economic analyses of curtailment mitigation and for quantifying the marginal cost of grid adaptation in Chile and similar high-penetration renewable systems.

From an operational perspective, reducing the escalating levels of curtailment in the SEN requires prioritizing the timely completion of the transmission reinforcements already under development; particularly the Kimal–Lo Aguirre HVDC line and the new 500 kV corridors between Antofagasta, Atacama, and Coquimbo. These projects directly target the structural north–center congestion identified in this study and therefore constitute the most immediate pathway to relieve system-wide constraints. In parallel, strengthening the overall flexibility of the SEN remains essential to accommodate the variability associated with growing wind penetration. Enhancing the ability of the system to manage rapid supply–demand fluctuations—regardless of the specific technological or regulatory instruments used—will reduce reliance on curtailment as an operational measure. As these structural and operational conditions improve, surplus wind energy could also be directed toward complementary applications—such as storage or, in the Chilean context, hydrogen production—as illustrative pathways to extract value from energy that would otherwise be curtailed.