Updated June 2016

Our all solar house was self-built in five months. Hi-tech construction resulted in a superb and workable water-front home in Australia’s far north. It was even built using mainly solar energy. This article tells how we did it. 

The site at Ngungnunkurukan (locally known as Coconut Well), 21 kilometres north of Broome, is a very special place. It 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 agreed with the traditional owners that all rocks and significant trees be left untouched and 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. Broome Shire and FESA 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. Pic: successfulsolarbooks.com

 Cyclone Rosita

We moved onto the land in April 2000.  Cyclone Rosita struck ten days later. We sheltered from the 285 km/h (180 mph) gusts by burying our OKA off-road (ex-mining) truck to its chassis and strapping a table over its windscreen. Whilst scary, the cyclonic wind was an invaluable introduction. As the site is high up and totally exposed caused us to rethink the engineering – so as to cope with such forces.

Our main requirements for our all solar house were for light and space that would form a natural extension of the Indian ocean and and dunes to our west. And likewise to the untouched bush behind us. The original concept was good but, as an engineer myself, it was no surprise that the architect’s plans were rejected (by Broome Shire) as having totally inadequate cyclonic strength. They were subsequently and brilliantly re-done by Garry Bartlett of B&J Building Consultants (in Broome).

Our all solar house uses a mix of aircraft and structural engineering rather than conventional building techniques: there is not a single mud brick, straw bale or structural timber in it!

Its domed ceiling 4.3 metres high at its middle and has no internal walls – only a few minor partitions less than two metres high. 

Coconut well - the completed structure web

The all-steel structure. Despite its size and apparent complexity it was erected in just 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. The Pindan soil really is this colour.  Pic: successfulsolarbooks.com

Our all solar house gains its main wracking strength from its double curvature roof fabricated from heavy gauge rolled Colorbond steel. This is secured by 14 gauge Tek screws and cyclone washers at every channel into purlins welded to four similarly curved 200 mm rolled steel joists. A similar gauge terracotta-coloured Colorbond ceiling is attached directly to the underside of the purlins. This massively-strong but light roof (an almost aircraft style wing) is tied down by 40 square steel posts (each 100 by 100 mm) embedded into a 600 by 600 mm steel reinforced concrete perimeter beam. Diagonally sloping 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. The floor is ochre-coloured polished concrete.

A major building problem was having the originally planned 100 by 200 mm hollow steel section roof supports formed to the necessary double curvature without buckling. This proved not possible so the design was 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.

The all-steel structure demanded dimensional tolerances of only a few millimetres: closer to watch-making than many builders’ plus or minus a centimetre or two. The forty 600 mm perimeter tie down beams 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 25 metre diagonals.

The steel suppliers erected the main structure — assisted by a 200-tonne crane that position the 1100 kg steel beams from 50 metres away. The entire structure (as shown above) was erected in a single day. Our closest neighbour (a kilometre away) told us: ‘When I left for work there was an empty space – I came home eight hours later and a big house was there’.

Contractors were used for concreting, roofing, internal plumbing and non-solar electrical work but, apart from that, all else was done by my wife Maarit and myself with the invaluable assistance of an ex builder who was living locally at the time. We started building in earnest in August 2000 and moved into the semi-completed – but already our all solar house – just before Christmas 2000. It was finally completed about six months later.

I built designed and built the initially 2.5 kW solar system for our all solar house prior to starting the house construction. Almost all of the power needed for building was supplied by that system. This, even more than the unusual house design, puzzled the contractors. They knew the closest grid power was over 20 km away – yet here was 230 volts at considerable wattage. It was truly hard to persuade them it really was only from solar. 


Our all solar house solar system

I designed and built the original system using 30 by 80 watt 12 volt Uni-Solar solar panels located on the north facing roof of an existing shed, about 200 metres from the house site. These provided up to 50 amps at a nominal 48 volts (about 12 kW/day under the Kimberley’s only too ample sun). These charged a bank of 24 two volt wet cell batteries – each of 1000 amp hour – via an 80 amp Outback Power solar regulator. The batteries were connected in series parallel –  providing about 48 kW/h. The inverter was a 3.8 kW SEA unit – that had a massive (and needed) 11 kW peak ability. When the all solar house was completed, the solar array was moved closer to it. To cope with irrigation needs it was later expanded by adding 130 watt mono-crystalline solar panels, resulting in a total of 3.4 kW (about 18 kWh/day in peak periods).

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

The original batteries were flogged to death by a caretaker we employed for a time. They were replaced by sixteen 12 volt gel cell batteries – each of 235 amp hour. 

battery bank coconut well

The 16 by 12 volt (235)  amp hour gel cell batteries were connected in series-parallel to provide 940 amp hours (45 kWh). Pic: successfulsolarbooks.com

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. Pic: successfulsolarbooks.com

Our all solar house ran totally on 230 volts from the inverter. 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 width pond and 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 as a cool ocean breeze developed by midday almost year around. 

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Original plan and elevation of the house – the pool location (shown here) was deemed impractical. It was moved to the side.

Water

Despite excellent 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 inset between the roof and the ceiling (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: in accompanying passing cyclones. That tank can fill in less than one hour! The water is then pumped up to a 100,000 litre tank that is 100 metres from the house. Water is supplied 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.

Pix: successfulsolarbooks.com

 

Swimming pool

An above-ground rendered concrete block 31,000-litre swimming pool is attached to the house. This, as with all of the house and property, runs from solar alone. It has an interesting and originally unique way of operating. I designed it to have a dedicated 480 watt solar array that directly drives a Lorentz 48-volt brushless DC motor pump (there are no batteries). Rather than using chloride, the irrigation water input feed passes through the pool replacing about 10% each day. Original quotes for the circulation system of our all solar house’s swimming pool (all based on traditional 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, driven from the four dedicated 120 watt solar modules seen here. The inset cyclone-protected gutters can be seen here. The protruding section on the leftof the house is an ultra-strong cyclone shelter. Full details of the pool are in Solar Success. Pic: successfulsolarbooks.com

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

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The easy clean bathroom was designed and built by my wife, Maarit Rivers.  Pic. successfulsolarbooks.com

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

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

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 Maarit does a bit of heavy blacksmithing. With a MIG, TIG and arc welding Certificate (plus production engineering) behind her, she is also totally comfortable using big power tools such as nine-inch angle grinders. It is not a good idea for tradesmen, or sales-people in local hardware stores, to patronise her re engineering matters! Pic: Broome TAFE College.

We had none but genuinely helpful cooperation from Broome Shire. They rejected the original engineering plans but as I already felt that cyclone protection was inadequate I welcomed their confirmation and 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”.)

With some regret, primarily that large bush properties require ongoing major maintenance, but also as our expanding family lived mainly in Sydney, we sold the property in late 2010. Whilst new batteries were required the system was still working well in 2016. Our now home (in Church Point – north of Sydney) rapidly became an all solar house too!  And Maarit acquired her MA.

The all solar house cost us about A$220,000.  

(This article was originally published in the Australian magazine Natural Home Builder. It was updated by Collyn Rivers in 2016.)

Successful Solar Books and its associated company (Caravan and Motorhome Books) publishes and sells constantly updated books and articles on all aspect of solar and also RV electrics by writer/engineer Collyn Rivers. Click here for his bio. Our current books in this area are Solar Success (that has all you’ll ever need to know to buy, design and/or install stand-alone solar systems for homes and properties.) Collyn’s book Solar That Really Works is for cabins, camper trailers, caravan and motor home. Both are available from specialist suppliers in Australia and New Zealand or directly from Successful Solar Books. 

If interested in caravans or motorhomes please see our associated website caravanandmotorhomebooks.com