No resource is 100% reliable: US polar vortex and energy

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No resource is 100% reliable: US polar vortex and energy

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US polar vortex and energy

This is the third blog in the no resource is 100% reliable series

Catherine Mitchell, IGov Team, 30th July 2015

The USA suffered some of its coldest weather ever over a few months as a result of the polar vortex in early 2014. PJM, the nation’s largest grid operator with nearly 190,000 megawatts (MW) of power generation across 13 states in the Mid-Atlantic and Midwest, set 8 of its top 10 winter peak records in its history, and called the weather extreme a 1-in-10 event. MISO, the nation’s second largest grid operator with 175,000 MW of generation in its Mid-Atlantic and South market, set a new peak demand record on January 6, when much of its region experienced the coldest temperature for 20 years. Texas also hit a peak demand record at 8.00am on 7 January. Power and heat were maintained across the US despite record energy demand and despite major problems  with fossil generation, which was not being able to provide power when it was called upon because of the effects of the cold (for example, a record 22% called in PJM did not come on, against the 7% average).

What happened?

FERC, the Federal Energy Regulatory Commission, asked all the US grid operators for data to explain how they had dealt with the extreme weather conditions. It is because of the published data sources that we know exactly what happened to each power plant during that time (eg PJM)

Many of the power plants that were out of service in PJM as peak energy demand rose were out of service because of operational problems like frozen coal stockpiles, boiler tube failures, faulty ignitions or just simply refusing to start up in the cold because of having been off line for months. PJM is now working on corrective measures – requiring tests to ensure operational capability – as well as thinking about new financial incentives.

ERCOT detailed how supplies tightened to peak demand at 8 am on the 7th January when 3,700 megawatts of generation was forced to shut overnight on top of nearly 10,000 MW of generation that was already shut for the season or for planned maintenance. About 1,800 MW of the 3,700 MW of the forced outages were weather-related, including two large power plants in north central Texas. One power plant totalling 474 MW shut unexpectedly at about midnight. Another power plant totalling 464 MW shut, followed by a third plant of 892 MW which shut at 6:31 a.m. At 8:11, another sudden loss of generation fossil occurred totalling 901 MW, dropping the grid’s frequency 59.855 Hz.

Are the Grid Operators worried for the future?

Grid operators in the US, as here in Britain, have to provide forecasts for expected demand and how that demand will be met.

In the PJM area, the 22% unexpected outage rate of fossil fuel plants led to the use of aging coal-fired plants owned by AEP, which were planned for closure. Immediately after the polar vortex, there were calls to keep these coal plants open on security grounds. However, PJM, have said that the plans for closure should go ahead because their ongoing and future plans for development of the network mean there will be no need for them – and hence there is no need for customers to pay for them. PJM confirmed which plants will cease to operate and these include the 9 AEP coal plants (accounting for 5400 MW). PJM confirmed they have more than enough resources to meet its reliability needs for the following winter after accounting for these retirements. Its needs through 2017 will be met by existing coal, gas, and nuclear power plants supplemented by nearly 19,000 MW of new power generation (much of it renewables), energy efficiency resources, and power imports from neighboring regions of the country, plus over 12,000 MW of demand response. The combination of resources will more than offset the approximately 15,000 MW in expected regional coal plant retirements, leaving PJM with about 20 percent more capacity available than needed to meet projected demand.

Moreover, PJM and most other grid operators set the level of power they can expect from wind based on its summer performance, when wind speeds are at their lowest annual levels. This minimises wind expectation but also (probably) reduces the effective reserve margin. In other words, even though PJM says the reserve margin is around 20%, it is probably higher.

Similarly, MISO reported to FERC it has sufficient power capacity and demand response resources to meet this summer’s and next winter’s projected demand. This, as with PJM, would come via new plants (many of which are renewable), energy efficiency investments, new operational measures and imports.

Renewables, demand response and imports – all invaluable for grid reliability

Wind power has been an important contribution to grid reliability (see ERCOT , PJM, MISO, California ISO (CalISO), New England-ISO  (NE-ISO). NE-ISO told the House Energy & Commerce Committee that renewable energy resources were an important part of the energy mix during the 2013-2014 winter, contributing low cost emissions free power during high demand. They also said that demand response resources performed well and were a valuable part of maintaining reliability during the winter season.

Xcel Energy of Minnesota said [after wind had provided 46% of total energy output in the Upper Midwest region on 5 January 2014] that ‘wind brings great value to our customers as a cost-effective and clean resource . . . . we’ve learned a lot about how to reliably and safely integrate wind energy onto our system . . . . by using state-of-the-art wind forecasting tools we have saved Upper Midwest customers more than $15 million in fuel costs since 2009. Wind resources at 3 a.m. on 5 January 2014 provided 1622MW of the 3512MW Xcel’s customers were using in Minnesota and neighbouring States. The previous record was set in April 2013, when wind generation met 42% of customer demand.

Polar Vortex and Energy Debate in US

The 2013-2014 Polar Vortex provoked a deep debate in the US about how to maintain grid reliability – across the spectrum of the energy industry. FERC promotes an energy efficient, interconnected US with high levels of demand response. States respond differently to this vision. ConEdison called for transparency of discussion about customer solutions and responsibilities. PJM released an integration report which said that it predicted 30% of its electricity from renewables by 2026 and that it would not be a problem. Nevertheless, the polar vortex clearly showed that fossil fuels were not without problem, and renewables, the demand side and flexibility all helped (reduce, flatten and flex).

Lessons Learned

There are two key lessons about energy system operation which needs to be learned.

Firstly, no resource is 100% reliable, and secondly, because of that we need to have as energy efficient and flexible energy systems as possible.

In general, the debate over resource reliability, centres on whether renewables can be relied on. However, this is wrong because the reality is that no resource is 100% reliable. It must also be remembered that fossil and nuclear cannot always be relied on, as this example of the polar vortex, and another blog about the Belgian Nuclear Winter, illuminates. Each system has to be operated so that resource characteristics and unexpected occurrences can be dealt with satisfactorily – and this is perfectly possible and nothing unusual, irrerspective of whether it is a high penetration renewables system or a fossil / nuclear based system.

Unlike coal and natural gas plants in the US polar vortex of 2013-2014, energy efficiency and demand side response perform well in all weather conditions. Renewable energy offers zero-cost fuel no matter the weather – and some renewable resources perform at very high levels during the winter months when gas supply is under the most pressure.

The global energy future is uncertain. However, one thing that is not uncertain is that energy systems need to be able to operate flexibly to meet reliability needs as cost effectively as possible, whilst meeting our environmental objectives. That means reducing our total energy use, flattening the demand curve via demand side response and increasing flexibility, via interconections, storage and so on. Expanding these resources is the best no-regret way to meet our energy needs – both on an every-day basis and in winter and summer extremes.

No resource is 100% reliable series:


This blog was updated on 3rd August – to provide links to the wider series.

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