What is Variable Renewable Energy (VRE)?


Variable Renewable Energy (VRE) is a term used to describe a specific type of renewable energy source. What sets it apart is its non-dispatchable nature, meaning that its output varies and fluctuates. Examples of VRE include wind power and solar power, which differ from controllable renewable sources like hydroelectricity generated from dams or biomass. VRE also differs from more consistent sources like geothermal power.

Wind and solar energy sources have unpredictable characteristics. Changes need to be made in the design and operation of the electric power system. This is done to prevent damage to the system and avoid widespread power outages. These changes are often called renewable integration. In 2018, the share of generation from VRE sources in the United States was 8% of the total with wind sources contributing 80%. The majority of reliability metrics monitored by the North American Electric Reliability Corporation (NERC) remained stable or showed improvement in 2018, indicating that, at current generation levels, VRE sources are not causing extensive reliability issues.

Optimising Variable Renewable Energy Generation: Strategies, Challenges and Grid Expansion

When considering adding more Variable Renewable Energy (VRE) generation, the unpredictability of wind and solar resources makes it difficult to determine if a system with a lot of VRE can meet long-lasting electricity needs. There are multiple ways to evaluate the capacity value of VRE, as well as strategies that enable utilities and power system operators to meet electricity demand using wind and solar sources.

To generate more Variable Renewable Energy (VRE), we need to improve and expand power grids to connect with distant solar and wind resources. By strategically implementing a mix of policies, regulations, and processes, we can encourage investment in extensive transmission expansion. These initiatives not only increase the use of VRE but also delay the need for network upgrades.

Also See: What are Non-Renewable Resources?

Wind and Solar Variability

Wind and solar power production depends on unpredictable weather patterns. A wind turbine usually generates the most electricity overnight and in the early morning, while solar generators are at their peak in the early afternoon.

However, wind turbines typically generate the most electricity during the winter and early spring, although this can vary depending on the region. On the other hand, solar generators usually reach their highest production levels during the summer. When it comes to electricity demand, there are fluctuations throughout the day, with the highest consumption usually happening in the early evening. Electricity usage increases during the winter and summer seasons.

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