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Power To The People

Tuesday, May 06, 2008

By Fiona Barber

Imagine locking up your holiday house and heading home secure in the knowledge the power you’ve just used is about to be returned to the national grid and credited back to you. And best of all, you didn’t have to do a thing.

“Over the course of the year, the amount of power they send back should equal the power they draw down from the grid,” explains Arhaus director Dan Heyworth.

This is the sort of energy-conserving future Martin and Liz Irvine have planned for their family when they build their holiday home at Tupare on the shores of the Kaipara Harbour – and by next summer it should be a reality.

The Auckland business couple wanted an out-of-Auckland getaway that was energy neutral – or better – for themselves and their three children aged 20, 17 and 13. So they called in the experts and the result is a plan for a four-bedroom energy-efficient home which harnesses solar power for electricity and water heating and includes a host of features designed to capture and store heat and energy.

The Irvines will hook up to the national grid and use all the electricity they need when they’re at their nine-hectare property at the Tupare Peninsula development, a 50-minute drive north-west from downtown Auckland. But when they’re away, the surplus they generate from their solar system, which uses photo voltaic cells on the roof, will be fed straight back into the national supply.

Martin and Liz Irvine bought their lake-side, coastal land four years ago, so they’ve had plenty of time to plan their 250 square metre environmentally-friendly retreat, which they hope to start building in May.

“I said to my wife Liz, ‘I want this to be energy neutral and, as much as possible, sustainable.’ That was our starting point,” says Martin who is managing director of Warwick Fabrics. Liz is also a director of the firm.

Arhaus, an Auckland sustainable design and building company, is responsible for the plan which involves three low-impact rectangular buildings.

“Over the course of the year, the amount of power they send back should equal the power they draw down from the grid,” explains Arhaus director Dan Heyworth. “To make that work you have to design the house so it is very energy efficient – make sure the house doesn’t overheat and in winter you want to be able to store energy.

The home, he says, is “passive solar” designed. This involves an insulated concrete slab which stores heat, double glazing and making sure the house is facing just the right direction. “Then we’ve calculated the eves to make sure the strongest sun is kept out but the winter sun is allowed in.”

The house will be insulated with an eco-wool product – “double insulation of a typical house” – and will have energy-efficient lighting and appliances. On top of the photo voltaic cells, the Irvines’ retreat will have a separate solar system using copper tubes to heat water.

The energy efficient considerations, Heyworth says, will add 5-10 per cent on to the cost of the building project, but that investment should be regathered within 10 years in energy savings and in the house’s added value.

“It takes clients like this who are forward thinking,” he says. “They see the value in doing this”

Powersmart is providing the solar system for the project and director Mike Bassett-Smith is a big fan of clients connecting to the grid if you can, rather than using batteries. “There’s a preconception that being off the grid is more sustainable. It’s a misplaced view.

“Batteries are what’s required for storage and storage is the limiting factor – that’s what dictates how much energy you can use and at what times.”
Batteries, he adds, have a life of 9-10 years and are 80 per cent efficient – for every 10 units of electricity you put in, you only get eight back.

“These factors start to add up. The grid is a much better financial choice and environmental choice. In New Zealand most energy is generated by clean sources – hydro.”

It is a system, Bassett-Smith says, that offers the best of both worlds; all of the efficiencies and none of the limitations. And “because there are no batteries, the working lifetime of the on-the-grid system is 25 years-plus”.

His company has just finished a system for a new home in suburban Nelson. “We put in a reasonably small solar system for $22,000. That should provide all the electricity for the life of the home.”

He says that house will also use 75% less energy than the average NZ home. “We offer the chance for the homeowner to own their own energy.”
The set-up, he says, does not require any change in lifestyle, wiring or the way the home looks. And when you’re designing a home from scratch, like the Irvines, it is not a huge addition to the budget when you think about it from the start.

And word must be spreading. Powersmart, says Bassett-Smith, is “amazingly busy”.
The company also has systems for older homes, but given the buildings were not designed to be so energy efficient, they do pose some challenges.

The Irvines, meanwhile, hope to be in their holiday home by Christmas, but their energy-efficiency plans may not stop there. Martin Irvine has his eye on another source of power. “I’d like to have wind power on top of the solar power – so we’re completely sustainable,” he says.

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arhaus.co.nz
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tupare.co.nz

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Power To The People