A Waitomo cave's facilities are now powered by a new Caterpillar microgrid technology system, with a solar/battery system with diesel backup after a project between the site’s owners and operators and Gough Power Systems. This off-grid solution now powers the ticket and tour office at Ruakuri Cave​s, and a water pump for farm irrigation.

It was unveiled at an official opening for the new visitor centre in late January. Ruakuri is one of several caves in the Waikato and are a major tourist attraction for their glow-worms and limestone formations.

Tourism Holdings Limited, which operates the site under a lease from the Holden Family, is a signatory to the Tourism Sustainability Commitment and says renewable energy is a key part of the partners’ sustainability vision.

Gough Power Systems Segment Manager Hybrid Energy Solutions Grant Kirchmann says the generator has not run since the project was commissioned in November, as it's only designed as a standby option. "There has been zero fuel burn, which the benefits of 100 percent renewable electricity and free electricity generated from the sun," says Grant.

The microgrid uses two Caterpillar 4 kW inverters, an 8 kW bi-directional inverter, and 20 kWh of BYD lithium batteries stored in a dust tight enclosure. The 9.87kW's of Caterpillar thin film photo voltaic (PV) panels are installed on a fixed tilt ground mounted structure.

The system is backed by a Cat 11 kW DE11 10kVA prime generator.

"The solar is designed at a 1.2 AC/DC ratio to optimise winter energy yield," Grant says. More PV panels, inverters, and batteries can be added to the modular system if demand increases.

A cloud-based software system sits behind the plant, providing the owner and operator with remote access to plant information such as yield and energy balance. Ongoing maintenance requirements depend on how often the generator runs. Maintenance is required when the generator runs for more than 500 hours in a year. The PV panels are self-cleaning, says Grant, and Gough Cat will monitor the site remotely.

Micro-grid solutions are becoming increasing popular as an alternative way to supply power where replacing existing network assets is uneconomic. Gough CAT is working on two further micro-grid projects in Fiji, of 8 MW and 2 MW, while a 400 kW project is being advanced in New Zealand.

"This was Gough's first Hybrid project and we are proud to say it had very successful conclusion as it not only met the client's needs but exceeded them as a sustainable and highly reliable solution," says Grant.

For more information contact Grant Kirchmann at Gough Power Systems on 0800 93 39 39 or www.terracat.co.nz