We chose to leave the Melbourne rat race in the mid to late eighties in favour of a 22 acre, heavily timbered bush block in the Central Highlands of Victoria near Daylesford. Self sufficiency was at the heart of this move so it was decided to design a comfortable house that would need very little energy input, and we should be able to tap into nature’s local energy resources. We moved into the ‘off grid’ house in 1992.
Woodrising was built as a reverse masonry veneer house with an attic storey.
The external timber structure – clad with ‘board and batten’ from the local forest – was heavily insulated as was the roof and the periphery of the slab. The internal masonry walls were in effect a ‘heat bank’ or thermal battery. There was no masonry in the upper storey as we did not wish to retain heat there which could be an issue in summer. The upper floor was comfortably warm in winter just from waste heat from downstairs. At the peak of the roof structure there were large vents at each end of the house. These were used to vent air from the building if things got too hot. The house was ventilated using the “stack effect”.
A medium sized PV based power system was installed with backup provided by a pre-WWII aircraft generator (26v, 50A dc) – just add engine!
Over time I noticed that the property had some degraded earthworks that had once been part of Daylesford’s early water supply. It was no great challenge to reactivate some of this old infrastructure and we soon had a small micro-hydro power plant in operation. This setup supplied about 5kwh a day – all day, which was about the energy demand of the house so we were well served for electrical energy. However, by the late nineties, the big drought had set in and eventually the turbine was decommissioned and removed. The creeks had dried up and didn’t look like reviving. They still haven’t.
The property also had a small permanent spring so we had a good water supply. A very small solar pump automatically kept the header tank full.
There was plenty of firewood lying around (congealed solar energy) so that took care of space and water heating as well as cooking . Solar space heating was somewhat modest due to the very heavily timbered forest surrounding the house acting to screen off the solar radiation.
A small dishwasher and all the usual ‘mod cons’ were part of normal life as we did not believe that off grid living required some sort of return to more primitive times. The overall domestic infrastructure was to a very large extent, automatic.
We had many delightful low cost years at Woodrising but there came a time when a single storey house was needed.
The successor to Woodrising is Galaxy Hill, a very different construct altogether. The site is a twenty acre block on a hill with no trees and so had good access to nature’s local wind and solar resources.
The house has no architectural merit but is simple and basic, and so, is easily built.
As I expected to be an elderly retiree at Galaxy Hill, there would be no firewood to carry, cut or even purchase. The idea was that the sun was readily available all day – for most of the year – and at 1kw per square metre, there should be more than enough direct radiant energy available to power a low energy home (or even a high energy one). I like to think of this house as being powered by a thermo-nuclear fusion reactor located at a safe distance from the nearest population centre.
Again, as the daily electrical demand was around 4 or 5 kwh, we didn’t need a very large power plant so a twelve module PV array was set up and a small wind turbine was added as a conversation piece (it doesn’t offer much in comparison to the PV). We moved in late in 2008 and have since added a further eight modules as PV costs have collapsed.
Galaxy Hill is essentially an ‘electricity only’ installation. There is a gas cooker in the kitchen but it is not used. LPG is retained as a backup to solar water heating in poor weather but when this hardware is to be replaced we will expect to use a heat pump type – adding more PV of course. PV modules are distributed on the roof and on the ground. They are arranged to face NE, north and NW. This provides an effective ‘virtual tracker’ where solar current runs at a steady ‘average’ input during the day instead of a peak around the middle of the day when input current values could be dangerously high.
The reverse masonry veneer design feature of the house – similar to Woodrising – has the effect of keeping internal temperatures down in the hot weather as heat is absorbed into the walls.
Thus the internal temperature is always lower than outdoors in summer and there is no need to open windows for ventilation. The heat in the walls thus remains there until the cooler weather comes and thus helps with thermal comfort in winter.
As the house windows are not opened, ventilation is provided by warm, fresh, oxygenated air from an attached greenhouse. (Woodrising also had an attached greenhouse but it was not very effective due to shading from the nearby bush). The ambient temperature range in this region oscillates between zero and 45 degrees. The house internally follows a similar curve between about 15 and 30. The house has no built in heater or cooler although it is possible that as I get older and less active, I might find that an efficient heat pump would have merit.
For much of the year, the batteries, which are inside the house (along with the inverter and control gear) are filled by mid morning and the energy of the sun for the rest of the day is discarded. So a heat pump could be used to make the most of the solar current during the rest of the day to top up the heat energy stored in the walls.
Off grid living is potentially very expensive at the installation stage unless the domestic electricity demand is very small. This proviso can be achieved by ensuring that the architecture is highly energy efficient. So we made sure that both Woodrising and Galaxy Hill were very energy efficient, as buildings. People thinking of going ‘off grid’ need first of all to deal with the energy demand of the building.
Notes: The design characteristics of Woodrising and Galaxy Hill were based on an earlier building designed and built in the Dandenong Ranges in 1982.
SPECS: The Galaxy Hill Power Plant comprised 12 x 170w modules (2kw); 8 x 200w modules (1.6kw) for Total input: 3.6kw.
Battery: 1080Ah FLA. Battery Charger: 60A (SS&L). Inverter: SA32 (2.4kw (cont). Charge Controller: PL60.
This is a self managing system but since it is in the house I can monitor it easily and make adjustments as required.
Woodrising was chosen as the site for the first Sustainable Living Festival in 1998 and was extensively analysed in “The Owner Builder” issue no 85 in 1998. Galaxy Hill was described in ReNew (ATA) issue no 112, in 2010.
