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Generating Results

Over the last ten years, we have applied innovation and technology to improve efficiency, add generation capacity and grow annual generation yield. Opportunities are often created through the skills and insight of our staff and support companies.

Already we have captured significant shareholder value through enhancement of existing assets. We see many further opportunities in our future enhancement investment programme to deliver value. Proof that a relentless quest for innovation – part of TrustPower’s DNA – can improve shareholder return without major capital investment.


Upgrade creates opportunity for additional 1.9GWh energy yield.

Mangorei tunnel was constructed back in 1959. It carries water from the Maunganui river into Lake Mangamahoe, for generation as well as for New Plymouth’s drinking water.

We relined the tunnel in 2004, refreshing its life expectancy, increasing its capacity by 50% and enabling more water to be diverted into the lake. Innovation enabled a cost-effective solution in a very short construction window.

Increasing yield by 1.9GWh per year, the project achieved upwards of 16% return on investment. It also brought more reliable water supplies to the people of New Plymouth. Further enhancement through capture of flood flows is planned for 2012.


Simple modification leads to 330% increase in water take.

The Arahura Wainihinihi race diverts water from three small catchments into the Dillmans/Kumara scheme. TrustPower’s engineers discovered the intake to the race had poor hydraulic efficiency and therefore lower water diversion than allowed for by our resource consents.

Following trials, our West Coast team discovered a clever modification for the crest profile. Simply by bolting on a steel angle section, they achieved a 330% increase in water take – within the consented volume. This project cost under $100,000 and delivered energy for an additional 340 homes.


Innovative solution minimises flood impacts.

Our Coleridge scheme relies on the diversion of water from the Wilberforce and Harper rivers into the lake, via the Oakden canal. The environment is flood-prone and only water with low sediment volumes is allowed to preserve the lake water quality. During floods, the diversion has to stop due to sediment and debris, traditionally this was achieved by breaching an artificial diversion bund and then re-instating it when the flow returned to normal.

TrustPower’s engineers and consultants designed and constructed three automated radial gates that allow the water flow to be shut off. Concrete housings were precast off-site, then installed and commissioned in the canal, with a very short outage period.

The gates have greatly reduced occurrence of embankment breaching, which now only occurs in large floods. Benefits span increased water volumes, reduced operating costs and greater operational safety.


Belief in local engineering skills delivers world-class results.

After its 2003 purchase, the Cobb scheme quickly became one of our most-prized assets. However, the cost of maintaining its turbines increased, and there was potential 
to make efficiency enhancements.

In 2009, we began thermodynamic efficiency testing: the most accurate way of testing high head pelton turbines. This innovative approach determined the performance of the old turbines, thereby minimising the risks in modelling their replacements.

We then engaged with Christchurch-based turbine designers. Using computer modelling, followed by physical model testing and validation, a new turbine and casing was designed. Engineering fabricators, again Christchurch-based, produced the new 10MW turbines, which were installed by our staff.

The result was an additional 3.2GWh of energy per year, with significantly lower maintenance costs. In addition, a capacity upgrade to 11MW meant improved peaking performance. All this was achieved at a fraction of the cost and complexity required from international turbine suppliers – proving that Kiwi ingenuity is alive and well.


Our specialists deliver the ideal solution.

The speed control systems at many of our generation stations are critical to the quality of electricity, and compliance with system rules. In 2005 these ‘governors’ were near the end of their economic life. The cost and complexity of replacement by overseas manufacturers was prohibitive, so we tasked our own engineers to design, build and prototype the new system.

In the face of significant criticism from beyond TrustPower, the governors have proven ideal, complying with all safety, quality and performance requirements. We have now installed 20 governors and in over 400,000 hours of operation there have been no faults. Savings over traditional governors total $3.4 million and other generation companies have shown interest in the technology.