Updated June 2017

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 truly a very special place. For example, it adjoins one of the three major Aboriginal song lines that traverse Australia. It has major rock formations significant to the Gularabulu people. Their community is a kilometre or two south. The land’s ten acres of natural bush fronts directly onto a tidal lagoon. The Indian Ocean is about 400 metres to the west.

It was agreed with the traditional owners that all rocks and significant trees specifically 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. Broome Shire and FESA allowed the obligatory fire trails to detour away from these areas.

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The upper half of the 10 acre block at Coconut Well. Pic: successfulsolarbooks.com

Our all solar house – cyclone inspired

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 thus an invaluable introduction. 

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

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

Its domed ceiling is 4.3 metres high at its middle. There are no internal walls – only a few minor partitions about 1.8 metres high. 

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The all-steel structure. Despite its size and apparent complexity it was erected in 12 hours. The diagonal steel tubes add strength and double as water drainage for the gutters. Pindan soil really is this colour.  Pic: successfulsolarbooks.com

Our all solar house – how it was built

Our all solar house gains its main wracking strength from its double curvature roof. That roof is fabricated from heavy gauge rolled Colorbond steel. It is secured by 14 gauge Tek screws and cyclone washers at every channel into steel purlins. The purlins are likewise welded to four similarly-curved 200 mm rolled steel joists. A similar gauge terracotta-coloured Colorbond ceiling attaches directly to the purlins’ undersides.

This massively-strong but light roof (an almost aircraft style wing) is tied down by 40 square steel posts. Each post is 100 by 100 mm, and 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.

It was originally planned to have 100 by 200 mm hollow steel section roof supports rolled to the necessary double curvature. This, however,  proved impossible without buckling. The design was thus changed to similar sized rolled steel joists. These were rolled up in Perth, trucked the 2100 km to Broome and welded up into complete end sections. They were then trucked the 4200 km round journey to and from Perth for galvanizing. The Colorbond roofing sections were likewise rolled to the same curvature.

The all-steel structure specifically demanded dimensional tolerances of only a few millimetres. This is closer to watch-making than many a builder’s plus or minus the odd Post Code. The forty 600 mm perimeter tie down beams nevertheless all needed placing within two to three millimetres in all planes. Surprisingly, it all worked. The finished 150-square-metre main structure was within 5 mm across its 25 metre diagonals.

Erected in one day

The steel suppliers erected the main structure. This was assisted by a 200-tonne crane. It positioned the 1100 kg steel beams from 50 metres away. The entire structure was surprisingly erected in a single day. A neighbour 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. We did have invaluable assistance from an ex builder. We started building in earnest in August 2000, and subsequently moved into the semi-completed house in late November. It was finally completed about six months later.

 Our all solar house solar system

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

The original system had thirty, 80 watt 12 volt Uni-Solar solar modules on a north facing existing shed. It was about 200 metres from the house site. This provided up to 50 amps at a nominal 48 volts. About 12 kW/day under the Kimberley’s only too ample sun. It charged via a bank of 24 two volt wet cell batteries. Each was 1000 amp hour – via an 80 amp Outback Power solar regulator. This providing about 48 kW/h. The inverter is a 3.8 kW SEA unit. It has a massive (and needed back then)11 kW peak ability.

Once completed, the solar array was moved closer to the house. To cope with irrigation needs I accordingly added 130 watt mono-crystalline solar panels. The resultant total was 3.4 kW (about 18 kWh/day in peak periods).

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

The original batteries were sadly flogged to lead acid death by a caretaker. They were thus replaced by sixteen 12 volt gel cell batteries – each of 235 amp hour. 

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                    The 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 LEDs). A Fisher & Paykel fridge coped well in Broome’s hot periods. Cooking was via LP gas (using 40 litre cylinders). Water heating was solar only. It worked well even in winter.

The house design was such that cool air from the Indian ocean was further cooled by a full width pond. It was then drawn into the house via almost always open doors, and then extracted by roof located vents. Air-conditioning was deemed unnecessary. Furthermore, 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 on year-round on rainwater, even for toilet flushing. The 280 square metre roof has two 250 mm by 150 mm stainless steel gutters. To protect against cyclones, these are inset between roof and ceiling. Water flows via (diagonal bracing) 150 mm steel tubes. These tee into sunken 200 mm pipes that run alongside 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 can fill in less than one hour!

The water is then pumped up to a 100,000 litre tank, about 75 metres from the house. From there, it 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. This has since frequently been copied.

I specifically designed it to have a dedicated 480 watt solar array that directly drives a Lorentz 48-volt brushless DC motor pump. all day long. There is this no need for batteries. Irrigation water passes initially through the pool. It replaces about 10% each day. Original quotes for the circulation system (all using 230 volts) 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, from the four 120 watt solar modules. Cyclone-protected gutters can be seen here. The protruding section on the left 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 desert between the two. Our all solar house used only 2% of our annual water allocation. The 98% remainder thus 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 it.

Moving on

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 a Counseling, and also a Psychology degree to her original arts B.A. And some Spanish and Mandarin to her existing four languages.

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 Maarit does a bit of heavy blacksmithing. She has a MIG, TIG and arc welding certificate (plus production engineering certificate). She is also totally comfortable using 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. For example, they rejected the original engineering plans. But as I too felt that cyclone protection was inadequate I thus welcomed their requirements.

One downside was the kitchen. Built locally, it is 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, but primarily that our expanding family lived in Sydney, we sold the property in late 2010. Whilst new batteries were required, the system is nevertheless still working well. Our now home (in Church Point – north of Sydney) not surprisingly became an all solar house too!  And Maarit acquired degree number four: a Master of Art Therapy.

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

Our all solar house – further information

Our book Solar Success covers all you’ll ever need to know to buy, design and/or install solar systems for homes and properties. Solar That Really Works is for cabins and RVs. Both are available from specialist suppliers in Australia and New Zealand or directly from Successful Solar Books. 

If interested in RVs etc see our associated caravanandmotorhomebooks.com . It has over 80 articles. 

This article by Collyn Rivers was originally published in the Australian magazine Natural Home Builder. It was updated by Collyn Rivers in 2017.