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Solar Cottage a very comfortable and economical place to live, in a very peaceful and pretty setting on the east coast of Tassie, within walking distance of all the amenities in Triabunna. I wanted a house with a low environmental footprint that was very economical to run. I have used aspects of the tiny house movement to reduce the size of my home to a size I need as oppose to designing a home for future buyers. I intend to live here for as long as I can. Passive solar designed, runs on power generated by an off-grid power system and collects rainwater from each roof (garage, shed and house).
My aim was to build a house that was comfortable for one or two people, simple to build, with no mortgage, and economical to run. At 40 sm2, it is small rather than tiny, with one bedroom, a open plan lounge/kitchen area with the laundry in the bathroom. The floor plan is rectangular with a skillion roof. The house is orientated to the north for maximum solar input. Most sunny days provide enough heat gain for the evening, and the average winter temperature inside (without heating) is 12 degrees warmer than outside.
The materials used are readily available:
- Colourbond outside and pine lining inside
- Floor is darkened concrete for passive solar gain
- Full height double-glazed windows
- Insulated floor, walls and ceiling.
Power was not available on the block, I installed an off-grid solar power system in the shed, later connected underground to the house. The panels are hinged on the north wall of the shed for maximum winter efficiency, at a low sun angle of 30 degrees. This placement reduces wind stress, and makes all of the structure and cabling accessible for maintenance. It’s easy to clean, and adjust the angle. The house requirements are relatively low, so the system is small. The panels provide 450 watts into 400 amp-hour lead-acid batteries. The yearly cost of $350 is less than grid power, which would be about $450 per year. While the system produces much more power than I can use, it remains disconnected from the grid to avoid the daily connection fee ($336 per year). The average daily load is 1kWh or 80Ah, and the batteries easily handle the occasional spell of two or three overcast days during winter. The average discharge is about 15%, dipping down to 40% at times in winter. The lights (30W in total) are 12 volt units sourced from marine, camping and electronics stores; they run on a separate 12V circuit, which makes it easy to modify. It is handy to have some electrical knowledge and skill for these 12 volt circuits. Finally, a 2kW inverter provides 240V power for the fridge, washing machine, and various power tools. However, the lead-acid batteries provide a little less, with a total recommended maximum output of about 1.5kW.
This size system requires a few changes of machines and habits. For example, I have a range of battery tools which can be recharged on sunny days, and I wait for sunny days to do work which requires heavy use of larger 240V power tools. And I don’t use high power household devices such as hair driers, toasters, and electric kettles. (Electric kettles are especially evil, drawing 2kW.) For one person, it turned out that gas was cheaper than electricity for cooking and hot water, at about $290 per year (electric would be more economical for a larger household). Gas also has the advantage of being unaffected by low energy production during darker winter weather. Space
heating is provided by a small pellet fire. These units have many advantages. As well as being incredibly efficient, it occupies little space, uses recycled sawdust for the pellets, has no exposed flame or embers, and produces a tiny ash residue. It requires 240V for the igniter and fans, but the power requirement is small. My yearly cost is about $150 for about 10 bags of pellets.
While mains water and sewage are connected to the house, rainwater is collected from each roof on the buildings into 9000 litre tanks, mainly for the toilets and summer watering in the garden. There’s lots of room on the block for raised vegetable garden beds and fruit trees, as well as native Tasmanian plants, partly to reduce the wind across the originally bare block.
There is a large area available for food gardening, as well as growing Tasmanian native plants. Solar Cottage is a short walking distance to the town centre reducing my reliance on using a car.
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