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- Downpours beaten
- Lead law' update
- Reality check
- On the hunt
- Health check
- Survey results
- Fire goes green
- Double dipping
- Flow reduction
- UK farming misery
- Bugs eating through fat
- 'Super' solution
- Luxury goes green
- O2 overcomes, too
- Norway shows the way
- Dubai: Changing landscape
- Harsh environment
- Democracy brings water
- Government leads the way
- Extracting oil from stand
- Heat Pumps: The new era
- Sao Paulo's hotel unique
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- Testing times 'down-under'
- iFlush: The digital revolution
- Much more to good design
- New lead policy
- India's modern sanitation
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- From Hutong to high-rise
- Attracting woman engineers
- Contemplating the future
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Don't let a valuable resource go down the drain.
Until recently, recovering heat in
wastewater discharged from fixtures
and appliances in dwellings,
commercial buildings and industrial plants was a
largely neglected source of energy.
However, with the rising cost of energy and
the need to reduce greenhouse gases, greater
attention is being given to this readily available
and clean
energy source.
Several heat-recovery systems are now
available, particularly from companies in
Canada, and new systems are also being
developed in Europe.
Andre Cayer is president of Watercycles
Energy Recovery, which is based in the Canadian
province of Saskatchewan. The company
manufactures the Watercycles heat-recovery
system and exports to the United States
and Europe.
Cayer says the system is designed to recover
energy from water being flushed down the drain
in residential and commercial applications.
It uses no energy itself, and there are no
moving parts.
“The Watercycle, which has a copper coil
system and forms part of the wastewater pipe,
extracts heat from the wastewater. This heat
is then conveyed to the incoming fresh water
before it reaches the water tank, thus preheating
the supply. The system will extend the
life of a hot water tank and reduce the stress on
a tank-less water heater.
“In residential situations, the Watercycle
requires no maintenance and has no effect
on lifestyle while saving money and reducing
greenhouse emissions. The system will recover
its cost in two to seven years, and this is based
on shower use only.
“For commercial applications, the main
opportunities are in areas such as multiple
shower installations in fitness centres and
swimming pools, and dishwashers in commercial
kitchens. The cost is greater due to the fittings
and installation time involved, but savings are
also greater because of the higher volume of hot
water consumed in a commercial setting.
“In the case of dishwashers, the water
temperature is also a factor, due to the delta T
(change in temperature). The greater the
difference between incoming fresh water and
heated wastewater, the faster the heat travels,
and therefore there is greater effectiveness.
“There is a C$100 (US$98) government
grant across Canada for home-owners who
retrofit, and in Saskatchewan the grant is
C$200 (US$197), which is 30% of the purchase
cost. There are also grants in Saskatchewan and Ontario for installations in new homes. In
addition, several natural gas companies are
offering grants to builders and home-owners in
various provinces.
“Despite the grants, our largest market is
the eastern US, where energy costs are three
times those of Canada, so people can’t afford
to throw energy away. Our main goal is to have
Watercycle installed with tankless and solar
water heating systems.
“Tankless systems are designed for
groundwater temperatures of about 20ºC
(68ºF). In locations where the water is 10ºC
(50ºF) or less they have difficulty meeting the
demand and a larger unit is required, which will
of course consume more energy.
“The Watercycle will put water into the
tankless system over 20ºC no matter how
cold the incoming water is (for our standard
58 long unit). This wastewater heat-recovery
system will also increase the amount of days
the solar system can provide 100% of the hot
water needs. It will provide more energy per
dollar spent than increasing the size of the solar
collection system.”
Renewability Energy, based in Ontario,
manufactures the Power-Pipe drainwater heatrecovery
system, which the company says is
installed in many commercial, industrial, multiunit
apartment and residential applications in
Canada, the US and Europe.
According to Renewability Energy vicepresident
marketing Walter Urban, the US
Department of Energy and Natural Resources has
identified water heating as the second largest
energy use in American and Canadian homes,
accounting for 20-30% of home energy costs.
“Showering is typically the highest hot water
load, and about 90% of the energy used to
heat water in a home is wasted to the sewer,”
Urban says.
“A standard water heating system can be
downsized by about 40% with the Power-Pipe
because of the additional water heating capacity
provided. A typical family of four will reduce
greenhouse gases by one ton (1 tonne) per
household per year by using a Power-Pipe.
“The patented Power-Pipe consists of copper
tube wrapped tightly around an inner copper
drainpipe. The unit becomes part of the drainage
stack, usually in the basement of a building,
by cutting the drainpipe and using the
supplied connectors.
“The exterior coils become part of the
freshwater supply line by diverting it to the
Power-Pipe.
“A key feature of its operation is the way
drainwater clings to the inside pipe wall and
falls quickly, creating a ‘falling film’ that readily
imparts its heat to the pipe wall. Efficiency of the
system depends on the length and diameter of
the Power-Pipe installed and the water flow rate.
“Manifolded systems are available for
industrial and commercial applications to split
large flows across multiple Power-Pipe units.
Because industrial and commercial systems run
for a large part of the day, energy savings can
be substantial. Payback on industrial systems
typically ranges from four to 16 months.”
Urban says there are numerous examples in
industry where the installation of Power-Pipe has
resulted in substantial energy savings, including
at the Unilever Ragu food processing facility in
Peterborough, Ontario.
“At that facility, hot that is used for cleaning
product containers, and was previously wasted,
is now recovered by a Power-Pipe system
and pre-heats steam feed water used in the
cooking process.
“This turnkey engineered heat-recovery
system, which was installed at a cost of about
C$27,500 (US$27,000), saved more than
C$26,000 (US$25,600) in the first year of
operation, resulting in a payback of just over
a year. The system includes a heat meter
to accurately quantify energy savings and
operational performance.”
ReTherm Energy Systems, based in the
Canadian province of Prince Edward Island,
produces the ReTherm heat-recovery system,
which is aimed particularly at the residential and
small-business sectors.
General manager Kevin Coulson says the
system is capable of recovering up to 30% of
drainwater heat, is easy to install, does not need
maintenance, and requires zero space because
it forms part of the wastewater drain pipe. “In
addition, ReTherm has a stay-clean design, as
the fast moving water on the vertical centre
section continually scours the heat transfer
surfaces, thus preventing build-ups.
“This system is also easy to install. In
homes under construction, installation can be
completed in one or two hours, and retrofitting
typically requires four to six hours.
“We have found that many businesses
commonly waste enormous amounts of hot
water energy every year, and they often have a
water heating system that is substantially and
needlessly oversized.
“By pre-heating fresh water via a heatrecovery
system, it’s possible to double or even
treble overall water heating capacity. Large
volumes of drain water can be accommodated
with multiple ReTherm units that can be
configured for specific needs.”
Waterfilm Energy in Medford, New York,
invented the GFX shower water heat-recovery
system incorporating a gravity-film heat
exchanger made from standard DWV copper
drainpipe surrounded by a coil of copper
water tube.
The inventor, Dr Carmine Vasile, says about
80% of the heat leaving a typical showerhead is
carried away in the drainwater. “We offer six standard heat exchanger models
for recycling 40-75% of the drainwater heat.
Actual savings depend on the shower flow
rate, plumbing system and type of GFX system
installed.
“For a two-bathroom house with two showers,
two bathroom sinks, kitchen sink, dishwasher
and clothes dryer, one Model S3-60-LC or
S4-60-LC will do the job at normal cold water
supply pressures.
“Best efficiency is achieved by providing
pre-heated water to the entire house, but it
can also just be fed to the water heater and/
or the cold water input of a shower. If plenty of
pre-heated water is mixed with hot water at the
shower, far less hot water is needed to provide a
comfortable shower.”
Developments in Europe
In the March 2007 edition of WPR we
reported on the development of a heatrecovery
technology called LowHeat, which
is designed to capture low-grade heat in
wastewater from the whole of a commercial or
domestic building.
The project is being advanced by a
consortium of 12 small and medium-sized
enterprises in six European Union countries.
Alastair Green, research and development
engineer at UK-based consortium member
AK Industries Limited, says patents to protect the LowHeat technology are now in place and
promotion can now proceed.
“Setting up a test installation is the
top priority, and the main focus will be on
industrial and commercial applications, rather
than residential.
“The potential for large cost savings is much
higher in these instances. Businesses such
as laundrettes or dyeing facilities are prime
candidates, as they produce huge amounts of
hot water that is just poured down the drain.
“Recovering even a small portion of this heat
energy would result in substantial cost savings
and would highlight the real potential of this
technology.
“Another benefit with industrial and
commercial applications is that the installation
itself tends to be less complicated. This type of
property will often use a single drain outlet for
most of the wastewater, whereas with residential
applications there can be outlet drains all around
the property, making installation more difficult.
“That said, once we have a test installation
set up, and customers in the industrial and
commercials areas are seeing real benefits, we
do have plans to explore the residential market.
“At AKI we are also developing another
wastewater heat-recovery device called Warmit,
which is aimed at recovering heat energy directly
from a shower. In effect, LowHeat is the followon
project from Warmit, taking the idea to the
next level by recovering wastewater heat energy
from an entire property.”
New product in the Netherlands
In the Netherlands, the Itho Company has
developed an updated version of its WTW
shower water heat-recovery system.
Itho’s Ronald Jense says the new DWTW
system features an aluminium double-wall
drainpipe section so that if there is a leak the
wastewater cannot come in contact with the
fresh water, and any leak can be detected from
outside the unit.
“This very lightweight unit, which is
constructed of aluminium and PVC, has an
efficiency of about 60%. By passing through the
DWTW, the shower drainwater cools from 38ºC
to 25ºC (100ºF to 77ºF), and the incoming cold
water temperature increases from 15ºC to 25ºC
(59ºF to 77ºF).”
The company expects substantial demand
for the new system, particularly in the dwelling
construction market.
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