Residential Grey Water Heat Recovery

Final Design Presentation

� Project/Scope

� Final Design

� Theoretical Simulations

� Model Construction

� Testing Results

� Cost Savings

� Health and Safety

� Design Recommendations

� Future Look Ahead

� Conclusions

� Mission Statement

� “To design, develop and test a safe, reliable, and efficient method to

recover heat traditionally lost from residential grey water in a manner

which reduces the energy costs of a residential building.”

� Residential waste water heat recovery unit for preheating

potable boiler feedwater

� Residential applications modeled and tested

� Showers and dishwashers included as grey water devices

� Model design, construction, and testing at typical operating

conditions

� Recommendations for future testing

� Coil Module

� The coil diameter is six

inches for bending

process

� Bottom is fitted with a

draining valve that runs

to the sewer for

maintenance

� Bypass in case system

backs up

� Coil

� Coils protective coating

provides 2 layers of

separation

� No areas exposed to GW.

� Two Module System

� PW connected in parallel

� GW connected in series

� Stand is incorporated to

ensure over flow from

coil to tank modules

� Would sit in close vicinity

to HWT to ensure

minimal losses through

lines

Reservoir Specification: Quantity

Material PVC, ABS

Total Volume 40 Lt

Greywater Volume 34 Lt

Length 36”

Diameter 10”

Coil Specification: Quantity

Tube Material Copper

Volume 0.5 Lt

Tube Diameter ½”

Tube Length 25 ft

Coil Diameter 6”

� During showers, a 10°C temperature increase predicted for

the potable water in our constructed model.

� Showers are typically 90% of household hot water demand

� The remaining 10% of hot water demand creates potable

flow but no grey water flow in the heat exchanger. The

predicted average potable water temperature rise for our

model is 6.85 °C

� Our multi-stage tests predict a 15 °C average temperature

increase for a typical shower.

� Multi-stage should be more cost effective with higher hot

water demands

� Proof of Concept model

� Reservoir with bottom sealed

� Overspill to allow for flow and

an inlet tube

� Copper coil module attaches to

cover of device

� Drain valve installed for

emptying

� Hoses and hose clamps for

connectors from sink to unit

Bill of Materials Material Quantity Unit Price Total Cost ($)

Copper Tube 1/2" 20ft 2.26$/ft $51.98

Reservoir for Coil Comp. 1 ea. DONATION $50.00

Work Space Fluids DONATION $0.00

Tech Services 10$/hr $115.00

Miscellaneous 3 ea. 10$ ea. $50.00

$216.98 Actual Cost including

Reservoir: 256.98$

� Tested different flow conditions:

� Simultaneous flow

▪ Potable and wastewater flowing (shower and

dishwasher)

� Batch flow

▪ Only potable running (sink and bath)

� Typical Morning

▪ 3 ten minute showers with 5 minute breaks

� Modular design multi-stage flow

▪ Potable water in parallel between two modules

▪ Reservoir temperature of second test at GW out

temperature of first test

� Typical morning testing

� 3 ten minute showers

� Tested different flow rates

� Q = 1.4, 1.6, 2.0, & 2.5 gal/min

� Slower flow rates result in

more heat transfer

� Additional tests:

� Continuous running, Q=2.5

� Decrease reservoir volume

� Modular Design

� 1st stage ΔT Average = 14.50⁰C

� 2nd stage ΔT Average = 11.51 ⁰C

� ΔT Average,1 = 13.00 ⁰C

� Single Module, Q=1.5 gal/min

� ΔT average ,2 = 8.92 ⁰C

� Multi-stage arrangement

feasible with high hot water

demand

� Gain 4 ⁰C using 2nd module

� Feasibility dependant on GW

temperature entering 2nd

module

� Batch Flow Tests - Potable water, Q = 1.5 gal/min

� Test scenarios:

� Sink use, tank temp = 25 ⁰C

� Bath slosh, tank temp = 40 ⁰C

� Potable water temps begin to converge as the heat is being extracted from

the reservoir over time

Test ΔT (⁰C) Efficiency (%)

Typical Morning

Q = 1.4 gal/min 9.85 30%

Q = 1.6 gal/min 8.92 28%

Q = 2.0 gal/min 8.62 24%

Q = 2.5 gal/min 7.68 23%

Multi-Stage Design

1st stage (Q = 0.75 gal/min) 14.50 43%

2nd stage (Q = 0.75 gal/min) 11.51 49%

Batch Flow

25⁰C Tank (Q = 1.5 gal/min) 5.43 30%

40⁰C Tank (Q = 1.5 gal/min) 9.75 42%

� Cost Savings based on

40% of Fresh water

demand being hot water

used in this device

� Additional 5% comes from

Dishwashers

� These were the average

values for Canadian

households in 2004

� The cost savings are dependant on two parameters. � Average temperature rise for potable water

� Hot water demand

� Plot shows ten degree rise for incoming potable water

against hot water demand

� Hot water demand varies from 20 gallons per day to 60 gallons per

day for a typical household

� The trend shows that as HWD is increased, the cost savings

per year increase

� The trends are based on the unit energy consumption

equation

0.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

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13.7

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Cost savings ($/Year)

Savings per year

0

200

400

600

800

1000

1200

1400

10.6

13.7

16.9

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Cost Savings (KW-Hr/Yr)

KW-Hr/Yr

0.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

10.6

12.7

14.8

16.9

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25

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29

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Co

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Model vs. Predicted Cost Savings

Savings per year

Model Savings per year

� The only major safety risk is potential contamination of

potable water supply by greywater.

� Risk is mitigated by using two layers of material separation between

potable water and grey water and no potable water joints exposed to

greywater.

� Potable water lines at greater pressure than greywater therefore if

leak occurs potable water will leak into greywater.

� Product has a useful life of at least 10 years and the majority

of components may be recycled at the end of its life.

� Include Baffles in the second prototype

� Baffles are discs that will increase the mixing of

the grey water inside the reservoir

� Gives the hot water entering from the bottom

more time to reach the top, creating a more even

temperature profile in the tank

� Reduce the volume in the second prototype

� With such a large tank used in the model testing,

the mixing was poor

� A smaller volume in the Reservoir will result in

higher convection coefficient surrounding coils

� Multistage for higher hot water demand

� Explore other means of reducing potable water

transit time

� This results in greater heat exchange to the potable water

� Possible avenues to explore:

� Increasing diameter of the copper coil

� Parallel flow between modules

� Recommended end use:

� Use in conjunction with energy efficient fixtures

� Homes with high hot water loads

� More efficient for shower users than bath users

� Further prototypes should be developed and tested

� Using the design recommendations obtained from the first model.

� Greater information about GWHR system performance

� It is recommended that a GWHR system monitoring and evaluation

program be implemented by installing the system in several

residential houses and evaluating performance.

� Develop installation guidelines.

� Installation guidelines and a tool for predicting energy savings should

be made available to potential consumers.

� Market evaluation.

� There is little information about consumer interest in GWHR systems

therefore surveys should be conducted to determine potential market

information.

� It can be concluded that:

� There will be cost savings that will exceed the initial capitol cost of the

product

� There is a great potential for cost savings with larger family

households or multiple roommate arrangements

� Implementation would be the next step in the design process

� Also the construction of a new prototype that has the proper

geometry

� Fluggen Industries would like to acknowledge the following

people and companies:

� Steve Bruneau (Project Supervisor)

� Dave Snook (Tech Services)

� Gerry Piercy (Ccore)

� Craig Mitchell

� Modern Paving

� Proskiw, G.(1998). Technology Profile: Residential Greywater

Heat Recovery Systems.

� Eslami-nejad, P., & Bernier, M. (2009). Impact of Grey Water

Heat Recovery on the Electrical Demand of Domestic Hot

Water Heaters.

� Environment Canada http://www.ec.gc.ca/eau-

water/default.asp?lang=En&n=F25C70EC-1

Any Questions?

ResidentialHeatRecovery.weebly.com

� Able to warm larger amounts of

water during non peak hours

� Volumes of GW and PW equal.

� PW volume increased, therefore

slower flow through tank

� Tank holds roughly 20 ltwater

� Needs to withstand city water

pressure on end caps