The expected outcome of utility integrated resource planning (IRP) is the optimum combination of power generation resources that will produce the most cost-effective and reliable generation for the rate-payer. That process is relatively simple for a nuclear and fossil fuel-based system. However, the difficult process of integrating renewable generation has made asset optimization and operational flexibility paramount.
Reaching that goal is often further complicated by external influences. For example, states/nations with Renewable Portfolio Standards often require a set quantity renewable generation to be produced each year.
Others have market-driven rules or have enacted legislation that require placing renewable generation first place in the dispatch queue, thereby pushing conventional assets further down the list, often from baseload to cycling operation. The unpredictability of renewable assets that operate only when the wind blows and the sun shines require more frequent cycling, start/stops, and ramping of assets that accelerates equipment wear-and-tear. Planners have a difficult job optimizing grid efficiency with so many moving parts.
All grid operators want more flexible generation that is available on demand. As additional wind and solar generation come online, some grid operators have elected to rely on market mechanisms to entice developers to construct fast response assets to fill in the inevitable production gaps inherent with renewable generation. Others have installed decentralized “blocks” of gas-fired assets, usually simple cycle combustion turbines or reciprocating engine generators, to provide quick response power when needed. Many utilities are forced to keep assets operating a part-load to satisfy rising spinning reserve margins.
Many utilities have added flexible generation in the form of high-efficiency combined cycle power plants but they remain best suited for operation at or near baseload operation for maximum efficiency.
There is also a steep price to pay in O&M and lost efficiency when cycling or operating a combined cycle plant at part-load. The elegant solution is large-scale energy storage but that technology remains a future promise.
Often these solutions attempt to use fossil generation in ways it wasn’t designed to be used, cycling when renewable energy supplies spike up or down, for whatever reason.
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