Lake Waikaremoana

Ensuring a secure electricity supply in New Zealand presents a multifaceted challenge, particularly during periods of high winter demand and low lake levels. 

Nationally, the primary goal is to address generation shortfalls during peak winter demands. Regionally, maintaining a balance between demand and supply while ensuring security of supply can be equally challenging when local lake levels are low. 

Recently, following the experience of Cyclone Gabrielle, the focus has shifted to enhancing infrastructure resilience in response to climate change-driven extreme weather events, which are increasing in frequency and intensity.

Resilient infrastructure

Cyclone Gabrielle highlighted these challenges with flood waters engulfing Redclyffe substation and inundating key control and electrical equipment built at ground level in the 1970s. Only after months of clean up and repair work is this critical substation that connects the region to the national grid back to normal pre-cyclone configuration.  

Jason Larkin General Manager Commercial Regulatory Unison

Although these emergency repairs replaced and raised critical equipment above the ground, it remains vulnerable to future extreme weather events. Transpower and Unison have explored options for either relocating the substation to a less vulnerable site or reinforcing the existing infrastructure. The goal is to ensure the substation can endure future flooding, seismic activity, and other natural disasters. 

Adopting modern design standards and advanced flow modelling will elevate and secure the existing site, ensuring its operational reliability even during extreme weather conditions. This initiative reflects a broader commitment to modernising infrastructure to cope with the realities of climate change.

Regional constraints

Regional supply security also currently depends heavily on the availability of local generation sources, such as the Lake Waikaremoana hydro scheme operated by Genesis Energy, in combination with supply from the national grid. 

Maintaining security of supply requires coordination between local generation, local distribution networks and the national grid operator (Transpower).  This is especially crucial during peak winter demands when the combined capacity of local generation and the national network is stretched to meet regional needs. 

This challenge is something that we’ve been working with Transpower on for some time. Transpower has satisfied its regulatory obligations around an efficient investment to install a third interconnecting transformer at Redclyffe, increasing the capacity to supply the region from the national grid. This addition is a significant step towards enhancing winter security of supply for the region, offering a buffer against potential shortages during critical periods or when the lake level is lower than usual.

Managing national winter peaks

In addition to building and maintaining the national grid, Transpower’s role also involves managing the electricity market to ensure supply meets demand, particularly during periods when renewable energy sources might be insufficient. New Zealand’s electricity generation is predominantly renewable, with over 85% sourced from hydro, geothermal, and wind, with solar being a new but growing addition. 

However, the variability of these sources requires robust coordination to maintain system balance. The challenge lies in the intermittent nature of renewable energy; the sun doesn’t always shine, and the wind doesn’t always blow, which can create gaps in supply that need to be managed carefully.

Transpower coordinates closely with distributors and large industrial customers to manage demand, especially during supply shortages. This coordination includes requesting measures such as throttling back industrial processes or distributors controlling residential hot water heating. These efforts are designed to smooth out demand peaks and ensure that supply remains consistent. 

In extreme cases which usually coincide with cold still winter evenings where electricity demand is high and there is limited wind generation, market measures and coordination efforts aren’t enough to maintain the balance between supply and demand. In these circumstances, controlled outages might be implemented to prevent system overloads, with priority given to critical services like hospitals. This tiered approach to maintaining security of the electricity system ensures that even in the worst-case scenarios, the most vital services continue to receive power.

Consumers play a key role in security of electricity supply

Consumers also play an increasingly significant role in maintaining supply security. Demand-side response mechanisms, where consumers adjust their usage based on price signals or through automated systems, are becoming more prevalent. These mechanisms not only help balance the system but can also offer financial incentives to consumers, making them active participants in ensuring a secure electricity supply. As technology advances, the integration of smart appliances and electric vehicles into the grid provides additional flexibility and responsiveness, further stabilising the supply-demand balance.

Consumer participation and demand side flexibility can be implemented quickly, and often at much lower cost than building additional capacity in lines and generation to meet growing peaks.  This way, consumers can play a role in enhancing both the security and affordability of their electricity supply.

Working together to ensure reliability and affordability

Unison takes a proactive approach by continuously monitoring supply into and through our network and collaborating with Transpower to anticipate and address potential current or future supply issues. This involves planning future network upgrades and maintaining a coordinated approach with generators and other stakeholders to ensure a reliable and affordable electricity supply for customers. 

By doing so, Unison plays a key role in ensuring a seamless integration of regional and national efforts in maintaining supply security. This collaborative effort is crucial in addressing both current demands and future growth, ensuring that infrastructure keeps pace with our communities energy needs as technological advancements introduce new ways of using, producing and storing energy, transport is electrified, and our population and economy grows.

In conclusion, ensuring the security of New Zealand’s electricity supply requires addressing both immediate and future challenges through resilient infrastructure, national and regional coordination, and active consumer participation. 

As the country continues to integrate more renewable energy sources and electrifies transport and industry while facing increasing climate volatility, these efforts are essential to maintaining a reliable, sustainable, and affordable electricity system. 


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1 Comment

  1. To give a balanced view of the supply situation some mention needs to be made of Whirinaki Power Station. There appear to be issues as to why this has rarely been seen to be assisting regional supply. Ironically the NZ government paid for Whirinaki for exactly that reason, during a hydro shortage in the early 2000s.

    Another obvious improvement in supply security would be to have Whakatu directly fed from one of two circuits coming over from Taupo. At present both circuits go into Redclyffe and when Redclyffe goes out Whakatu goes out at the same time.

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