Security of Supply and Capacity
Energy
The significant rain event last week contributed to a rapid increase in hydro storage across the country. National hydro storage remains high compared to historical averages for this time of year at 143% of the historical average. Manapouri storage continues to sit above its operating range indicating spill.
Capacity
Residual generation dropped to 217MW on Monday evening due to low wind generation and high demand associated with cold weather. This was close to the 200 MW threshold for issuing a CAN for low residual.
Our NZ Generation Balance planning tool indicates several days across September where there could be a potential generation shortfall if two major assets on the grid were to fail.
Electricity Market Commentary
Weekly Demand
National demand decreased by 8% from the week prior to 812 GWh. Average temperatures have risen since the significant cold snap the week before, helping to temper demand.
Demand peaked on Monday 18:00 at 6750 MW as cold temperatures lingered in the upper North Island regions. Temperatures then jumped up on Tuesday and remained relatively warm for the rest of the week.
Generation Mix
The proportion of hydro and geothermal generation remained high at 66% and 18% of the generation mix respectively. Wind generation increased from the previous week to comprise 7% of the energy mix, bringing the total contribution of renewable generation to 91% of the generation mix for the week.
Wind fell on Monday evening and through the early hours of Tuesday but picked back up for the rest of the week.
Weekly Prices
Average prices decreased since the week prior in alignment with demand. The average prices at Haywards was $62/MWh. Prices tended to remain at $150/MWh during the business week, with periods of near $0/MWh prices overnight as demand lulled. Prices did not exceed $1/MWh over the weekend, as typical low weekend demand coincided with high wind generation, high hydro generation and warm temperatures.
On Wednesday the Island prices separated as the system operator reclassified the HVDC as a single circuit risk. This led to high North Island reserve and energy prices.
On Monday and Tuesday, there was intra-island price separation in the Southland region as a Invercargill-North Makarewa constraint was bound. This is explained in further detail in the market insight.
HVDC
HVDC transfer was, again, entirely northward last week in accordance with high hydro storage and thus high South Island hydro generation. Peak transfer was 860 MW northward on Monday to support high North Island evening peak demand.
On Wednesday morning, between 03:30 and 11:30 am, the loss of both HVDC poles was managed as a single event. This means that the HVDC can not cover its own risk, and so enough reserves must be procured in the receiving island to cover the energy transferred. This led to reduced energy transferred North, high reserve and reserve costs in the North Island and subsequently low energy and reserve costs in the South Island.
Loss of Supply
There was a loss of supply at Ōpunake on Thursday of 4 MW, and at Bunnythorpe on Friday of 37 MW.
|
