Affordable Heating System Exploration for a Net Zero Energy Experimental Home in Melbourne, Australia

This research explores affordable heating for hydronic systems of a net zero energy experiment home built in Melbourne, Australia. For this research purpose, a 3m-wide 6m-long outbuilding is built next to a backyard garage. Inexpensive 12mm-dia poly tubes are spaced 100mm inside the 55mm-thick tiled concrete which rests on 100mmT (R2.5 m2·K/W) recycled cold-room panels laid on ground. This hydronic floor and ground is insulated from the outdoors by 400mm-deep 40mm-thick (R1 m2·K/W) polystyrene. Simulations show that heating this hydronic floor by a vertical ground heat exchanger with 17°C bottom temperature, together with a hydronic wall radiator heated by 30 evacuated tubes and a 2-cubic meter thermal storage, the indoors could reach the Nationwide House Energy Rating Scheme (NatHERS) respective night and day heating thermostats of 15°C and 20°C across winter. This assumes that the indoor had been at NatHERS temperatures for 5-6 years for the temperature at the bottom surface of the floor to stabilize. Since this warmup period has not been met, the results in this paper show the temperatures with water heated by a sawdust/wood burner. An experiment was also conducted with a compost pile. Two months after its initial 1-month exothermic phase, the temperature at the center was still 32°C. Thus, compost piles will be located outside external walls to help keep the perimeter of the floor warm. To obtain affordable hot water for the indoors to reach 20°C, a 6m-long 750mm-wide flat-belt collector was boxed up and covered with glass. In late autumn, it could only heat water by only 1-2°C and was thus not used in winter. However, by late spring, the empty poly belt had melted, indicating that, the temperature under the glass had reached above 50°C. Typical meteorological year data shows that the solar radiation has tripled that in autumn. Therefore, for future winter experiments, the weak solar radiation would be concentrated, by say, a north-facing parabolic trough with an aperture three times the area of a glazed metallic collector