What Is Intermittent Renewable?
An intermittent renewable refers to a type of renewable energy source whose availability fluctuates and cannot be controlled by grid operators, due to its dependence on natural phenomena such as sunlight, wind, or rainfall. Unlike dispatchable power sources, intermittent renewable generation is not constant and can vary significantly over short periods, presenting unique challenges and considerations within the broader field of energy finance. Key examples include solar power and wind power, which generate electricity only when the sun shines or the wind blows. The integration of intermittent renewables into the power grid necessitates sophisticated solutions to maintain grid stability and reliability.
History and Origin
The concept of harnessing natural forces for energy is ancient, but the widespread adoption of modern intermittent renewable technologies gained significant momentum in the late 20th and early 21st centuries. Early renewable energy efforts largely focused on hydropower and later, advancements in wind turbine technology and photovoltaic cells made solar and wind viable for large-scale electricity generation. As environmental concerns grew and the cost of fossil fuels became more volatile, global interest in renewable energy accelerated. The International Renewable Energy Agency (IRENA) notes that global investments in renewable capacity additions reached USD 570 billion in 2023, representing a 27% increase from the previous year, with a significant portion allocated to variable renewable energy sources like solar and wind.7 This surge in investment and technological progress has driven down costs, making intermittent renewables increasingly competitive.
Key Takeaways
- Intermittent renewable sources, such as solar and wind, produce electricity based on the variable availability of natural resources.
- Their output cannot be precisely controlled or dispatched on demand, posing challenges for grid stability.
- Integrating energy storage solutions and improving grid infrastructure are crucial for managing the variability of intermittent renewables.
- Despite intermittency, these sources are vital for the global energy transition and reducing reliance on fossil fuels.
Interpreting the Intermittent Renewable
Understanding an intermittent renewable means recognizing its inherent variability. For energy systems, this implies that the amount of electricity generated from, for instance, a wind farm, will depend on prevailing wind speeds, which can change hourly or daily. Similarly, a solar installation's output will vary with sunlight intensity, cloud cover, and time of day. This variability means that while an intermittent renewable source may have a high installed capacity, its actual output over time, known as its capacity factor, can be lower than dispatchable sources. Effective integration often requires robust energy storage systems, demand-side management, and advanced grid modernization techniques to balance supply and demand reliably.
Hypothetical Example
Consider a utility company planning its energy portfolio. They decide to invest in a new 100-megawatt (MW) solar farm. This solar farm is an intermittent renewable asset. On a sunny day, the farm might generate near its full 100 MW capacity during peak daylight hours. However, as the sun sets, its output drops to zero. On a cloudy day, its output might only reach 30 MW or less.
To ensure consistent electricity supply to its customers, the utility cannot rely solely on this solar farm. They might complement it with flexible natural gas plants, which can quickly ramp up or down, or with large-scale battery storage systems that can store excess solar power generated during the day and release it when solar output declines. The capital expenditure for such a combined system would reflect the need for both generation and flexibility. This strategic investment in a mix of sources helps mitigate the challenges posed by the intermittency of the solar farm.
Practical Applications
Intermittent renewables are central to global efforts to decarbonize electricity generation. They are widely applied in:
- Utility-Scale Power Generation: Large solar and wind farms are developed to feed electricity directly into national and regional power grids. In the first three months of 2025, the combination of wind and utility-scale and small-scale solar provided nearly a fifth (19.0%) of the total U.S. electrical generation.6
- Distributed Generation: Rooftop solar panels on homes and businesses allow for on-site electricity production, reducing reliance on the central grid.
- Microgrids: Localized grids often incorporate intermittent renewables, sometimes paired with storage, to enhance energy independence and resilience.
- Green Bonds and Sustainable Finance: Financial instruments like green bonds are increasingly used to fund projects related to intermittent renewables, reflecting growing interest in sustainable investment practices. investment
- Energy Portfolio Diversification: Utilities and energy companies integrate various intermittent and dispatchable sources to create a balanced portfolio that addresses both environmental goals and reliability needs, thereby managing risk management in their energy supply. The U.S. Energy Information Administration (EIA) provides extensive data and analysis on the growth and contribution of various renewable and alternative fuels in the U.S. energy mix.5
Limitations and Criticisms
The primary limitation of an intermittent renewable is its lack of dispatchability. This presents challenges for grid operators, who must ensure a constant balance between electricity supply and demand to prevent blackouts. When wind speeds drop or the sun sets, alternative power sources must quickly compensate for the loss of generation. This requires either maintaining flexible fossil fuel plants, significant energy storage capacity, or strengthening transmission infrastructure.
Critics often point to the need for "firm capacity" to back up intermittent generation. For instance, some argue that coal still plays a role in providing steady baseload power in areas where battery storage and other flexible sources are lacking.4 The reliance on natural conditions means that high penetrations of intermittent renewables can increase the complexity of managing the power grid, requiring advanced forecasting and control systems. The Federal Energy Regulatory Commission (FERC) has been actively working on modernizing interconnection rules and reliability standards to better integrate these technologies into the grid.3,2,1
Intermittent Renewable vs. Baseload Power
The distinction between intermittent renewable sources and baseload power lies in their operational characteristics and role within an electricity system.
| Feature | Intermittent Renewable | Baseload Power |
|---|---|---|
| Output Control | Variable and uncontrolled (dependent on natural factors) | Consistent and dispatchable (controllable output) |
| Predictability | Subject to weather variability; forecasted with limits | Highly predictable and stable |
| Examples | Solar PV, Wind | Nuclear, Coal, Geothermal, large Hydropower, Gas |
| Role in Grid | Provides clean energy when available; requires backup | Provides steady, foundational electricity supply |
While an intermittent renewable contributes to the overall energy supply, its variability means it cannot reliably serve as the sole source for continuous demand. Baseload power sources, on the other hand, are designed to run continuously at a stable output, providing the minimum level of electricity required by a grid over a 24-hour period. Integrating the two types effectively is crucial for a stable and decarbonized energy future.
FAQs
What are common examples of intermittent renewables?
The most common examples of intermittent renewables include solar power (photovoltaic and concentrated solar thermal) and wind power (onshore and offshore wind farms). Their generation depends on the presence of sunlight or wind.
How do energy systems handle the intermittency?
Energy systems address intermittency through various methods, including the deployment of energy storage technologies like batteries, pumped-hydro, or hydrogen storage. They also utilize demand-side management, which encourages consumers to shift electricity usage to times of high renewable output, and flexible conventional power plants that can quickly adjust their generation. Enhanced transmission infrastructure and smart power grid technologies are also crucial.
Are all renewable energy sources intermittent?
No, not all renewable energy sources are intermittent. While solar and wind are the most prominent intermittent renewables, other forms like geothermal energy and hydropower (particularly run-of-river or reservoir-based hydropower with storage) can provide consistent, dispatchable power. Biomass energy can also offer a more constant supply compared to solar or wind.
Why are intermittent renewables important despite their challenges?
Intermittent renewables are critical because they are emissions-free during operation and utilize inexhaustible natural resources. Their increasing cost-effectiveness makes them economically attractive. They play a vital role in reducing greenhouse gas emissions, combating climate change, and enhancing energy independence. The ongoing energy transition relies heavily on their expanded deployment.