All Solar House

Updated July 017

Our all solar house was built in just five months (in 2000). It used (then) hi-tech materials and techniques resulting in a pleasant and very workable living space on a stunningly beautiful site in Western Australia’s far north Kimberley.

The site at Ngungnunkurukan (locally known  as Coconut Well), 21 kilometres north of Broome, is a very special place. The site adjoins one of the three major Aboriginal song lines that traverse Australia. It has major rock formations significant to the Gularabulu people, whose community is a kilometre or two south. The land’s ten acres of natural bush fronts directly onto a tidal lagoon and then the Indian Ocean about 400 metres to the west.

It was accordingly agreed with the traditional owners that all rocks and significant trees be left untouched. Furthermore, that no access be allowed onto an exceptionally sacred part of the site. Also, as far as possible, to avoid having heavy earth moving machinery close to that area. The Shire and fire authority explicitly allowed the obligatory fire trails to detour away from these areas.

Coconut well from air jpg

The upper half of the 10 acre block at Coconut Well. 

Cyclone Rosita

We moved onto the land in April 2000.  Cyclone Rosita, however, struck ten days later. We sheltered from the 160 km/h gusts by burying our OKA off-road truck to its chassis. We also strapped a table over its windscreen. Whilst scary, the plus 160 km/h wind was nevertheless an invaluable introduction. As the site is high up and totally exposed to cyclonic winds it caused us to rethink the engineering. This was thus done: so as to cope with up to 240 km/h.

Our main requirements were for light and space. Furthermore we sought a home that would form a natural extension of the Indian ocean and dunes to our west. And likewise the untouched bush behind us. The original concept was good. But as an engineer myself, it was no surprise the structure was officially rejected – for inadequate cyclone protection. It was subsequently and brilliantly re-done by Garry Bartlett of B&J Building Consultants (in Broome).

All solar house – structural engineering

The resultant all solar house (of steel and glass) has a structure that is closer to a steel bridge than a house. It is a hi-tech design using structural engineering rather than building techniques. There is not a single mud brick, straw bale or piece of timber in it! It is also rare in having a ceiling 4.3 metres high at its centre.

Coconut well - the completed structure web

The all-steel structure. Despite its size and apparent complexity it was erected in one 12 hour day. The diagonal steel tubes add strength and double as water drainage for the gutters. The gutters (not yet added) are protected from cyclones by being between the upper and lower Colorbond roof layers. Pindan soil really is this colour.

The steel suppliers erected the steel structure — assisted by a 200-tonne crane ‘borrowed’ for the day. Even at that capacity the crane worked hard. It had to position 1100 kg steel beams at its full extension of close to 50 metres. Contractors were used for concreting, roofing and internal plumbing but, apart from that, all the work was done by ourselves, with the invaluable assistance of an ex builder

All solar house – power for building

Power for building was supplied almost entirely by solar. I therefore built a 28-module system prior to starting construction. They charged twenty-four 2.0 volt wet cell batteries – each of 675 amp hour via a Plasmatronic PL 40 solar regulator.

This provided 4 kW, and up to 11 kW surge. It could readily drive a nine-inch angle grinder. This, even more than the house design, tossed the contractors. They knew there was no mains power. Yet here was 230 volts at considerable wattage. It was surprisingly hard to persuade them it really was solar.

Double curvature roof

 The all solar house’s main strength is its double curvature roof of heavy gauge Colorbond steel. This is secured by 14 gauge Tek screws and cyclone washers at every channel into purlins. These are likewise welded to four similarly double curved rolled steel joists. A similar gauge terracotta-coloured Colorbond ceiling attaches directly to the purlins’ underside. This (in effect massive but light beam) is tied down by forty 100 by 100 mm square hollow steel posts. Each is embedded into a 600 by 600 mm concrete perimeter beam.

Diagonally located 150-mm, 20 mm thick, steel tubes provide further support. They also double as water down pipes. The remainder of the house is almost entirely cyclone-proof toughened glass sliding doors. Each has slide-open stainless steel security mesh. There are no internal walls as such. The floor is ochre-coloured polished concrete.

The first major building problem was having the planned rolled steel section roof supports formed to the necessary double curvature without buckling. This proved not possible. The design was thus changed to similar sized rolled steel joists. These were rolled up in Perth, trucked the 2100 km to Broome, welded up into complete end sections and then trucked the 4200 km round journey to and from Perth for galvanizing. The roofing sections were rolled to the same curvature.

All solar house – tight tolerances

The all-steel structure demanded dimensional tolerances of only a few millimetres. This is closer to watch making than builders’ typical plus or minus a centimetre or two. The 600 mm perimeter beam has over 40 beam tie downs. All needed placing within two to three millimetres in all planes.

Surprisingly, it all worked: the finished 150-square-metre main structure was within five millimetres across the diagonals.


The solar system

As noted above, the original solar system was designed and built just prior to starting work on the house. When the all solar house was completed, the solar array was moved closer to it. To cope with irrigation I added further 130 watt solar modules. The result was 3.4 kW (about 18 kWh/day in peak periods).

OLYMPUS DIGITAL CAMERA

 The main solar array (a further bank of mono-crystalline solar panels were installed shortly after this photograph was taken (2005).

The original batteries were sadly flogged to death by a caretaker. They were replaced in 2007 by sixteen gel cell 12 volts batteries. Each is of 235 amp hour. The Plasmatronic regulator was replaced by an 80 amp Outback Power unit.

 battery bank coconut well

The 16 by 12 volt (235)  amp hour gel cell battery was connected in series-parallel to provide 940 amp hours (45 kWh).

 SEA inverter web

The SEA 48 volt dc -230 volt ac inverter has a peak capacity of 11 kW. An Outback Power 80 solar regulator  can be partly seen (bottom left).The small unit under the SEA is a Xantrex energy monitor.

The all solar house runs totally on 230 volts from the inverter.

Lighting & ventilation

All lighting was compact fluorescent (this was before the era of LEDs). A very efficient Fisher & Paykel fridge coped well in Broome’s hot periods. Cooking was via LP gas (using 40 litre cylinders). Water heating was solar only – and worked well even in winter.

The house design was such that cool air from the Indian ocean was cooled yet further by a full length pond. Moreover, it was then drawn into the house via the many almost always open doors. It was then extracted by roof located vents. Air-conditioning was deemed unnecessary. A cool ocean breeze developed by midday almost year around. 


 Water

The bore water is rare in being crystal clear. It is possibly the purest in the world. The water comes from the Leopold Ranges some 700 km north-west of Broome (with untouched land between the two). We used only 2% of our annual allocation. The unused remainder pours into the Indian Ocean.

Despite that bore water, the main house runs year-round on rainwater, even for toilet flushing. The 280 square metre roof has two 250 mm by 150 mm stainless steel gutters. These are inset between the roof and the ceiling (specifically for cyclone protection). Water flows via the (diagonal bracing) 150 mm steel tubes. These tee into sunken 200 mm pipes that run the full length of both sides of the house. They fill a 14,250 litre holding tank behind and north of the house that catches the torrential seasonal rain.

That tank fills in less than one hour. The water is then pumped up to a 100,000 litre tank 100 metres from the house.Water is supplied to the house by a pressure pump and 500 litre water pressure tank. The pump replenishes the pressure tank once or twice a day. This is a very efficient and silent way of pumping water. The off-the shelf 0.75 kW pump runs just twice a day for about three minutes each time.

 

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Kitchen with a view

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                  Walls of glass bring the outside in.

Swimming Pool

An above-ground rendered concrete block 31,000-litre swimming pool attaches to the house. This, as with all of the property, runs from solar alone. It has an interesting and originally unique way of operating. It uses a 480 watt solar array. This directly drives a Lorentz 48-volt brushless DC motor pump. There are no batteries. Irrigation water input feed passes through the pool replacing about 10% each day.

Original quotes for the circulation system (based on 230 volt technology) were around $60,000. Ours cost $7500 in 2002.  (Full details are in Solar Success.) 

coconut well air pool view

The crystal clear water of the solar swimming pool. The circulating pump runs all day. It is driven from the four 120 watt solar modules seen here. Inset cyclone-protected gutters can also be seen. The protruding section on the left is an ultra-strong cyclone shelter. (Full details of the pool are in Solar Success.)

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Easy clean bathroom

Sewerage is septic. We would have preferred a more ecologically sound system, but (then) Shire regulations prevented it.

Broome Shire was genuinely helpful. They rejected the original engineering plans. But as I already felt that cyclone protection was inadequate I thus welcomed their requirements.

One downside was the kitchen. Built locally, it was very poorly made. “Call yourself a cabinet maker” said Maarit to one of them, “you’re not even a half-decent bush carpenter!”.

Maarit

My now-psychologist and somewhat feisty Finnish-born wife (Maarit) has a sculpting background. She acquired Welding and Production Engineering Certificates at Broome TAFE in anticipation of building. Maarit is still comfortable using big power tools such as nine-inch angle grinders.

It was (and still is) not a good idea for any tradesman or sales person to patronise her in hardware stores! 

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Maarit does a heavy blacksmith job on a roof tie-down plate (she had a ‘do not mess with me’ reputation amongst tradesmen in Broome!).

We started building in earnest in August 2000 and moved into the semi-completed house but already all solar house just before Christmas.

A time to move on

The all solar house worked well for us for ten years. Whilst there I wrote and published five books. I also spent three years at Notre Dame University auditing the Aboriginal Studies course. Meanwhile Maarit acquired two university degrees, and added some Spanish and Mandarin to her existing four languages.

But as our expanding family lived mainly in Sydney, we sold the property in late 2010.  Our home (in Church Point) has of course become an all-solar house too!.

This article was originally published in Natural Home Builder. It was updated by Collyn Rivers in 2011, 2014 and 2017.

Further reading

Collyn Rivers’ book cover every aspect of designing, installing and using solar. Solar Success relates to homes and properties. Solar That Really Works relates to cabins and RVs. For every aspect of RV electrics see his Caravan & Motorhome Electrics.