The March newsletter from Aegent Energy Advisors is a great overview of issues connecting wind generation and natural gas and, particularly, coal-fired generation.
Renewable Energy Integration and Wind Challenges
Read the full article at Aegent Energy Advisors' websiteGrowing wind capacity will contribute to SBG and greatly increase ramping requirements, just as the Ontario grid's most flexible ramping resource - coal - is being phased out. This means that in terms of accommodating rapid wind fleet growth, the phase-out of coal-fired generation could not be happening at a worse time.
Coal-fired units are particularly valued for their output range flexibility, commonly being able to operate between 10% and 100% of their rated output. A theoretical 100 MW coal-fired unit can then run between 10 MW and 100 MW and is said to have 90 MW of "ramp depth".Natural gas-fired units are replacing coal. They typically have much less flexibility and the amount is a function of a number of factors: simple or combined cycle design, gas turbine type, steam turbine (if applicable) and heat recovery steam generator type and configuration. The vast majority of Ontario's newer gas fleet procured through the Ontario Power Authority's Clean Energy processes are combined cycle plants. The IESO views them as having a minimum output of about 60%, meaning a theoretical 100 MW unit would run between 60 MW and 100 MW and so have 40 MW of ramp depth.To achieve 1,000 MW of ramp depth, about 1,100 MW of coal-fired generation is required while 2,500 MW of natural gas-fired generation is needed. Put another way, the approximately 3,500 MW of coal-fired generation still online in Ontario in early 2012 has about 3,150 MW of ramp depth - the same depth provided by 7,900 MW of natural gas-fired generation.