Ontario system operator notes substantial role of nuclear

26 February 2019

Nuclear power plants produced 61% of Ontario's electricity in 2018 and remain a "substantial form of generation" while supporting system reliability, according to newly released data from the Canadian province's Independent Electricity System Operator (IESO).

IESO's system control room (Image: IESO)

Total electricity demand for the year was 137.4 TWh, which was in line with 2015 and 2016 figures but slightly higher than 2017, when demand had been lower due to mild conditions. More than 93% of the electricity generated in Ontario in 2018 came from non-greenhouse gas emitting sources. Nuclear's 90.1 TWh of generation accounted for 61% of grid-connected generation in 2018, with hydro providing 36.2 TWh (25%), gas and oil 9.6 TWh (6%), and wind 10.7 TWh (7%). Biofuels and solar, at 0.4 TWh and 0.6 TWh respectively, each accounted for less than 1% of grid-connected generation. Ontario closed its last coal-fired power plant in 2014.

Present capacity is sufficient to maintain reliability in Ontario through 2019, but new electricity supply may be needed in future. Citing a long-term forecast it released last year, the IESO said: "Ontario is emerging from a capacity surplus and there is a potential need for additional supply as early as 2023." The operator has begun work on a programme to "improve and strengthen" the structure of the existing market in recognition of changing needs, it said.

Peak demand - 23,240 MW - was in September for the third year in a row, a trend attributed to warm weather "lingering" into the autumn months while output from embedded solar generation is decreasing due to shorter and less intense daylight hours, the IESO said.

Most of Ontario's solar facilities are connected to the distribution, not the transmission, system. So-called embedded resources such as solar, coupled with price incentives such as the Industrial Conservation Initiative, which encourages large industrial customers to reduce their consumption at peak times, continued to help flatten demand peaks, the IESO said. Distributed embedded resources have grown rapidly over recent years - at the end of 2018 the province had over 4100 MWe of such generation - but this growth has now "largely plateaued", it added.

Nuclear manoeuvring

The IESO highlighted the capability offered by Bruce Power to reduce output from its nuclear plants by about 300 MW each, referred to as "nuclear manoeuvring". This provides "valuable" flexibility to the system at times of low demand when surplus baseload generation (SBG) exists, while also helping to avoid nuclear shutdowns, the IESO said. Planning nuclear outages to take place during periods of SBG saw the total number of nuclear manoeuvres reduce from 511 in 2017 to 115 in 2018, representing a total of 168 GWh, with no nuclear shutdowns required in the year.

The IESO said its variable dispatch system, which allows the system operator to flexibly dispatch grid-connected wind and solar, also helps to avoid the need to shut down nuclear during periods of SBG. System reliability and economic efficiency are also supported by the ability to import and export electricity, with exports helping to manage periods of SBG and imports supplementing local resources during times of high demand. With exports of 18,591 GWh and imports 8,438 GWh for 2018, Ontario continued to be a net exporter of electricity.

Eighteen of Canada's 19 operating nuclear units are in Ontario: Ontario Power Generation's six units at Pickering and four units at Darlington, plus Bruce Power's eight units. Bruce is due to begin a long-term refurbishment programme at six of its units, which will allow the plant to continue operating until 2064. The IESO in 2015 entered into a long-term agreement to secure 6300 MWe from Bruce units allowing Bruce to begin investing in life-extension activities for units 3-8 in readiness for the long-term refurbishment programme that will commence with unit 6 in 2020. The operator in November verified a final cost estimate for the Bruce 6 refurbishment CAD2.185 billion dollars (USD1.652 billion), saving about CAD150 million for customers over original estimates.

OPG is also in the process of a long-term refurbishment programme at Darlington, which began in 2016 with unit 2. That unit's refurbishment is scheduled for completion this year and preparations for work to start on unit 3 next year are under way.

Researched and written by World Nuclear News