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Increasing the energy efficiency of buildings
Chris CironePhD Candidate, Agricultural and Biological Engineering
Hot Water Heater
MixingValve
Cold Water Supply
Drain Water
Shower
Billable Energy
Hot Water System—How it Works
Shower drain water contains 80-90% of the thermal energy imparted by the hot water heater.
Showers
Clothes Washing
Dishwashing
BathsOther
End Use of Hot Water
Energy Flow Diagram for Shower Water
Primary Energy
Conversion and Distribution Losses
Losses to the Environment
Heater Conversion and Storage Losses
Hot Water Distribution LossesLosses Enjoyed by User
Losses due to EvaporationLosses to Building Drain Lines
Water Heating
Electricity Generatio
n
3
Waste Heat Recovery from Shower Water
Hot Water Heater
Heat Exchanger
ThermostaticValve
Cold Water Supply
Drain Water
Shower
4
Heater Conversion and Storage Losses
Primary Energy
Conversion and Distribution Losses
Electricity Generatio
n
Energy Flow Diagram for Shower Water
Primary Energy
Conversion and Distribution Losses
Losses to the Environment
Heater Conversion and Storage Losses
Hot Water Distribution LossesLosses Enjoyed by User
Losses due to EvaporationLosses to Building Drain Lines
Electricity Generatio
n
Losses Recuperated by Heat Recovery
Water Heating
with Drain Water Heat Recovery (DWHR)
5
6
Vertical RecuperatorsVasile & Vasile (1986)
Commercialized
Independently tested by several labs, however most Natural Resources Canada at the forefront of this effort. (Zaloumn et. al. 2007)
Independent Testing
Benefits of Drain Water Heat Recovery• Reduced utility bill for water heating• Reduces carbon footprint• Typically positive returns on investment (ROI)
• Increased hot water capacity for water heater• Increases available hot water duration (storage heaters)• Warmer supply temperatures (tankless heaters)
• Allows for smaller hot water heater to be installed• Can limit the energy throughput and increase service life of heating
equipment• Reduce peak electrical demands
What’s holding us back?• Economic benefit is directly felt only by energy consumer
• Property owner is not necessarily the energy consumer• rental properties• neighborhood developers
• Length of ownership does not justify the investment.• Lack of public knowledge regarding the technology
• Limited independent source performance data• long-term performance data• field studies to verify laboratory results• secondary benefits not well understood
• Limited financial analysis to support the investment decision
• Lack of tradesperson knowledge regarding technology• Potential plumbing code restrictions
• Limited or non-existent municipality incentives• Energy prices are too cheap to justify the capital cost
• Cost-prohibitive retrofit• Unit not compatible with house type.
