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Powering a 10 star home

A new Christchurch home has received Australasia’s first-ever 10-star eco rating, an award that recognises its energy-neutral, sustainable footprint. The innovative electrical infrastructure designed using PDL by Schneider Electric solutions, enables the home to switch seamlessly between mains and solar power.

The 140m2, two-storey home was designed by Christchurch architect Bob Burnett, a leading advocate of sustainable homes. Its thermally-efficient design includes solar wall framing (it pre-heats ventilation air), a hydronic underfloor heating system and slab-edge insulation (to reduce heat dissipating from concrete floor slabs).

Complementing these are numerous eco-friendly features: rainwater harvesting, reusable grey water, water-efficient fittings, solar power and energy efficient lighting and electrics. The reduced use of heating and electricity should keep the home energy-neutral, leaving it free of power bills.

The 10-star rating was awarded by Homestar, a system run by New Zealand’s Green Building Council. It uses a 1-10 scale to measure factors such as energy and water use, waste, ventilation and health and comfort. Homes built to New Zealand’s current building codes typically rate three or four on Homestar’s scale.

Bob says the thermal and energy efficiency in New Zealand homes lags far behind the rest of the world, and he plans to change that. “Energy-efficiency doesn’t have to be costly. As this home illustrates, it’s actually about using existing technology in a cleverer way – simple but smart.”

The Electrical Solution

The home’s electrical supply is split between conventional 240 volt AC from the grid and a 24-volt DC system from 16 roof-mounted solar panels. Most of the demand is met by the batteries – the home automatically switches to 240 volt mains when the batteries run low. The overall configuration demanded a relatively simple electrical design, but it came with a caveat.

To meet the architect’s energy efficient, sustainability brief, says Schneider Electric’s Dave Chapman (Channel Manager – Residential), “we had to think a little differently. Considering that the home is designed for a family, affordability was key. There is a misconception that energy efficient technology often carries a cost premium. Bob wanted a solution using standard, off-the-shelf technology.”

Dave’s team opted for energy saving techniques such as motion detectors – sensors which switch off lights if no one is in the room, and to support that they enhanced conventional wiring templates.

“For example, we introduced a sunset switch to specific circuits. It automatically renders these circuits active or inactive depending on whether its day or night. By ensuring that specific circuits can’t be used, any chance of accidental wastage is eliminated.”

The home is equipped with PDL by Schneider Electric’s Saturn White range of switches. “Again, while this is one of our standard http://www.eta-i.org/valium.html models, the way they are being utilized is innovative. Using a relay in the switchboard, we’ve created an “all-off” functionality. Specified circuits in the home can be shut down from one switch, again eliminating any possibility of lights or appliances being left on.”

To help the home owner keep track of electricity consumption, an Eco-mind energy monitor has been installed. It gives owners an easy to read and understand tool for managing and modifying their energy use patterns. Because mobile technology has become so prevalent in the modern lifestyle, the home has been equipped with multiple USB charging ports to service devices such as phones and tablets. With a five-star energy rating the USB chargers are particularly energy-efficient, as well as adding to the convenience for the home owners.

Dave says “a smart home means different things to different people, simple products and solutions can be utilized to provide smart outcomes.”

Solar

The home’s solar component was supplied by one of Schneider Electric’s specialist partner companies in Christchurch, Canterbury Power Solutions (CPS).

The system’s 16 photo-voltaic panels are each rated at 260 watts and charge two sodium-ion, 24volt batteries housed within a wardrobe. “The panels’ combined output of 4.16 kW,” says CPS owner Murray Marquet, “is easily sufficient for servicing the two batteries. These are maintenance free and fairly compact – each battery measures 300 by 300 by 900 millimetres (LWH).”

The DC power is converted to 240 volt AC by a Schneider Electric inverter connected to a Battery Management System (BMS). When the BMS senses that battery power is too low, it switches back to the national grid supply. It does this with the help of a simple DIN rail device mounted in the home’s switchboard.

“The switchover is automatic and seamless,” says Murray. “And as a grid-tied system, the solar configuration also feeds electricity back on to the national grid when there is excess battery power. Its clean electricity delivered to the grid at the standard 50Hz frequency. There are no rogue wave-forms.”

Homes with improved energy and thermal performance are likely to become much more common if Bob has anything to do with it. He has been instrumental in establishing Superhome – an industry initiative in Canterbury.

Superhome aims to build some 1,000 homes with a seven or higher Homestar rating over the next three years. A recent Auckland study, he points out, shows that a six-star home only costs about 2.2% more to build than the standard New Zealand three-star home, and that a six-star rating will halve a home’s energy bill.

For more information on Bob Burnett and this project click here 

 Photos courtesy of Bob Burnett.