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Hot Water

Water is heated for consumption (kitchen, laundry, bathroom) or as a means to heat the development (radiator or in-floor heating loop).

Solar contribution to water heating reduces demand for use of other fuels.
Environmental support fuels can be wood where woodlot source is connected, or gas through the acceptable calorific value of the fuel.
Electrical heating draws high power input beyond the capacity of most renewable energy systems, or uses fossil fuel sourced mains electricity.
Gas fuels can span the range from conventional fossil fuel sources to more environmental land fill retrieved gases or agricultural waste gases (methane) right through to hydrogen from electrolysis. The latter has the lowest pollutant output, combustion of hydrogen leaving water as residue.

Water heating by solar means

can result in water temperatures from tepid to hot, dependant on installation effectiveness and season.
Good clear solar access, correct inclination, effective thermosyphon of heated water, deliberate obstruction of backsyphon of heated water releasing heat to atmosphere, insulation of tanks and panels, avoiding wind chill of panels; all these detail issues contribute to system efficiency.
Systems using conductive fluids should not be used where sited on water collection roofs as release of fluid when pressurised can contaminate water collection.
Tepid solar heated water can be boosted at point of use to minimise boost heating required.

A variety of water heating systems already operating in projects from this practice include:-

  • in roof space solar hot water storage system (470 l.) with winter wood fire wet back boost operating from rain water supply operating since 1985 in home and office of this architect at Monarto South - nil fossil fuel use
  • in roof space solar hot water storage system (470 l.) with winter wood fire wet back boost operating from rain water supply operating since 1990 in home at D'Estrees Bay, Kangaroo Island
  • nil fossil fuel use with mains electric boost operating since 1992 from rain water in home addition at Silver Sands
  • in roof space solar hot water storage system (240 l.) with mains electric boost operating since 1993 from rain water in home at Lewiston
  • in roof space solar hot water storage system (300 l.) with wood stove wet back boost operating since 1994 from rain and creek water in home at Wistow - nil fossil fuel use
  • home made solar hot water storage system operating from rain water since 1994 in home at Bower - nil fossil fuel use
  • roof mounted solar hot water storage (300 l.) with gas boost and 12V DC ignition powered from renewable energy system operating from rain water since 1995 in home at Inman Valley
  • currently under development - solar hot water pre-heat storage feeding to modulating instantaneous gas hot water boost at point of use for new solar powered warehouse at Ridleyton in inner Adelaide - minimum fossil fuel use

The philosophy in each of these installations is to:-

  • maximise on-site self sufficiency (wood lot, rain water)
  • minimise energy demand (minimum off-site or fossil fuel energy)
  • maximise service life (rain water, gravity feed or <40psi pressure) in each installation to suit the circumstances of each project.
Prominent outcomes are:-
  • maximising solar contribution to heating,
  • minimising boost and requiring occupant intervention to instigate boost,
  • using renewable power for boost where practicable,
  • using low ion content in rain water to maximise hot water service life,
  • adjusting occupier expectations/use habits to achieve minimum services demand.This includes carrying out laundry operation in sunny weather, etc.

The buildings themselves in these projects also follow a low energy demand philosophy. Space heating is in part by passive solar, though in some designs the summer ventilation focus also reduces north facing glazing, accepting that the low winter passive heat gain rates achieved is in the dry arid project locations still sufficient to achieve comfort.

A number of these projects incorporate specific internal greenhouse spaces which can be sealed from or opened to the home to encourage summer outward ventilation and winter heat inward flow.

Projects at Wistow, Bower, Finnis, Myrtle Bank use these, while the Inman Valley project has a sun room with pergola shading to grade between winter passive gain and summer cross-ventilation. The result is minimised formal space heating requirements.

A number of project designs (Mt. Barker and Carey Gully sites) incorporate in-slab warm water piping from solar roof collectors for space heating, but these are not yet operational.

The remnant space heating demand then in these various projects is achieved from wood fire fueled from on-site wood lot. That fire source in some projects is also cooking source and finally has a wet back hot water boost role - notably in the Monarto, D'Estrees Bay and Wistow projects.

Total energy demand for these projects thus is between 0.8 to 1.7kWhr/day and make reliance on modest size renewable energy system without back up practicable.

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