ERCOT Summer Planning Reserve Margin (%) Reported in May of Previous Year 45 42.6% 40 35 32.5% 30 26% 20.1% 18.9% 17.5% 14.8% 15 13.3% 13.6% 17% 16.5% 17.1% 14.3% 12.6% 18.2% 13.8% 14.3% 11% 10 Target Reserve Margin Is 13.75% 2018 2016 2015 2014 2013 2012 2011 2010 2009 2008 2007 2006 2005 2004 2003 2002 2001 0 2017 May 2019 Update 5 8.6% 2020 23% 20 2019 (%) 25 Year figure 2. The ERCOT reserve margins have fallen dramatically. november/december 2019 <8 0 <9 0 <1 00 <1 10 <1 20 <1 30 <1 40 <1 50 >1 50 <0 <1 0 <2 0 <3 0 <4 0 <5 0 <6 0 <7 0 Duration (%) more than 95% instantaneous penetration of VRE is essen- Future Markets: Large Overhaul or tial in meeting the Irish government's target of 70% annual Incremental Adjustments? renewable supply by 2030. The primary question being asked is how significant the Australia has observed increasing interventions in the design changes need to be to enable a market with a nearly market for the purposes of maintaining system security. In full supply of renewable energy. Although many electricity 2018, AEMO intervened to commit synchronous units in South Australia for a minimum of 40% Duration Curve of Dispatch Prices in South Australia* 16 of all intervals to maintain sysMedian of AUD$90/MWh Median Price of AUD$66/MWh tem strength (as high as 65% in 14 During Interventions at Other Times some months). Most of AEMO's 12 interventions have occurred dur10 ing periods of lower prices (Fig8 ure 3) or when the gas fleet is on 6 outage. In these periods, there is 4 an absence of incentives to keep 2 units committed. Nonsynchronous generation (primarily wind) 0 has also been curtailed to maintain system strength. This emphaRange of Prices (AUD$/MWh) sizes the importance of having a Dispatch Price During Intervention Dispatch Price During Other Periods market design that fully incorporates the full suite of technical requirements critical for operat- figure 3. The duration curve of prices during system directions in Australia. The ing a complex electrical system. asterisk denotes unadjusted dispatch reference price for South Australia during 2018. ieee power & energy magazine 61