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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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