Abstract
As we approach deeply decarbonized electrical grids worldwide, wind energy shares are rapidly rising and projected to reach or even exceed 40% of all energy generation within a few decades for many parts of the world. With the associated intermittency of wind energy, this large wind energy penetration will lead to progressively problematic mismatches between energy generation and grid demand. Several wind-heavy grids are already experiencing low (or even negative) energy prices when wind energy supply is high and/or grid demand is low, where the result is generation devaluation of wind. This effect can be quantified by the Value Factor, which is the ratio of annual capture price for wind energy relative to that for all forms of energy. Herein, we define the Grid-based Value Factor (GVF) using grid prices while the Net Value Factor (NVF) also includes the effects of grid congestion and wind farm curtailment. Recent data for US grids with wind shares approaching 40% indicate that NVF will also approach 40%, representing a 60% loss in energy revenue due to wind intermittency. However, these losses can be avoided through three main factors: high-capacity grid transmission, government subsidies/support, and high-capacity long-duration energy storage. For worldwide grids without these mitigating factors, the US trends are a harbinger for future devaluation of wind energy at high wind share. To design and develop new concepts of wind turbines and wind farms in such cases, a new grid classification system is proposed based on NVF. Given a Grid Class and Wind Class, the wind energy system design objective can be based on annual system costs relative to spot market energy annual revenue. For example, the Cost of Valued Energy (COVE) is proportional to the ratio of system costs to energy revenue, while Grid Parity Factor (GPF) is the ratio of energy revenue to system costs. Such metrics can then be used to optimize Capacity Factor, on-site energy storage, system control, etc. for a wind turbine/farm. These techno-economic approaches can be coupled with more holistic approaches that integrate consider societal and environmental impacts as we head towards deeply decarbonized grids.