Abstract
Domestic hot water use in Canada accounts for roughly 19% and 8% of total residential and commercial building energy use, respectively. After use by building occupants, domestic hot water is disposed of in the sewer system where it mixes with other wastewater streams, typically reaching temperatures as high as 25 °C. Thus, an opportunity exists for recovering low-grade heat from wastewater and using it for meeting local thermal loads. This study uses the Carleton University campus, located in Ottawa, Canada, as a case study for wastewater heat recovery. The campus wastewater energy resource is estimated using a novel method, and a feasibility analysis is conducted on an industrial-scale heat pump that recovers waste heat from the university’s main sewer outflow pipe. The recovered heat is used for heating water at the university’s main athletics facility. Results show that installing a wastewater heat recovery system decreases greenhouse gas emissions and total annual costs by approximately 95% and 8%, respectively, relative to a base case natural gas heating system. Low-grade wastewater heat is an underutilized energy source that is both sustainable and accessible in most urban centres across Canada. Increasing the capacity of wastewater heat recovery systems has the potential to significantly increase energy savings and decrease greenhouse gas emissions in our energy system.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Abbreviations
- GHG:
-
Greenhouse gases
- COP:
-
Coefficient of performance
- BC:
-
Base case scenario
- SHR:
-
Sewer heat recovery scenario
- BCRE:
-
Best-case recoverable energy estimation
- WCRE:
-
Worst-case recoverable energy estimation
- \( \dot{V}\left( t \right) \) :
-
Building water consumption (m3/hr)
- \( \dot{V}_{sewer} \left( t \right) \) :
-
Hourly variation of flow in the main sewer outflow pipe (m3/hr)
- \( V_{heated} \) :
-
Volume of water heated by a building in a set time period (m3)
- \( Q \) :
-
Energy used to heat hot water in buildings (kJ)
- \( \rho \) :
-
Density of water (kg/m3)
- \( C_{p} \) :
-
Heat capacity of water (kJ/kgK)
- \( T_{SP} \) :
-
Temperature of the hot water tanks on campus (°C)
- \( T_{mains} \) :
-
Temperature of fresh water in the water mains (°C)
- \( \phi \) :
-
Heating ratio
- \( V_{total} \) :
-
Total volume of water used in a building during a set time period (m3)
- \( T_{out} \) :
-
Temperature of the outflow from a single building (°C)
- \( \dot{Q}_{Sewer} \left( t \right) \) :
-
Energy in the main sewer outflow pipe (kW)
- \( T_{sewer} \left( t \right) \) :
-
Hourly variation of temperature in the main sewer outflow pipe (°C)
- \( \dot{Q}_{{re\text{cov} erable}} \left( t \right) \) :
-
Hourly variation of energy that is recoverable from the main sewer outflow pipe (kW)
- \( T_{{disch}\mathrm{arg}e} \) :
-
Temperature at which the effluent leaves the Carleton campus and enters the city sewers (°C)
- \( \dot{Q}_{out,BC} \left( t \right) \) :
-
Energy output to meet the domestic hot water load in the base case scenario (kW)
- \( \dot{Q}_{fuel} \left( t \right) \) :
-
Energy content of the fuel entering the boiler in the base case scenario (kW)
- \( \eta_{BC} \) :
-
Average efficiency of the boiler in the base case scenario (%)
- \( \dot{W}_{in,ep} \left( t \right) \) :
-
Energy required to pump effluent from the wet well to the heat pump evaporator (kW)
- \( \dot{Q}_{evap} \left( t \right) \) :
-
Energy absorbed by the heat pump evaporator (kW)
- \( T_{LLT} \left( t \right) \) :
-
Temperature at which the effluent leaves the heat pump evaporator (°C)
- g :
-
Rate of acceleration due to gravity (m/s2)
- \( \Delta H \) :
-
Effluent pump system head loss (m)
- \( \eta_{ep} \) :
-
Effluent pump efficiency (%)
- f :
-
Friction factor
- L :
-
Effluent pump system pipe length (m)
- d :
-
Effluent pump system pipe diameter (m)
- v :
-
Fluid velocity in the pipe (m/s)
- K :
-
Minor loss coefficient
- \( \dot{V}_{\hbox{max} ,ep} \) :
-
Maximum volumetric flow rate through the effluent pump system (m3/s)
- \( v_{econ} \) :
-
Economic velocity of water (m/s)
- \( \dot{Q}_{out,SHR} \left( t \right) \) :
-
Energy output to meet the domestic hot water load in the sewer heat recovery scenario (kW)
- \( \dot{W}_{in,HP} \left( t \right) \) :
-
Energy required to drive the heat pump compressor (kW)
- COP(t) :
-
Heat pump coefficient of performance (COP)
- AC:
-
Total annual cost ($/yr)
- NPC :
-
Net present cost ($)
- i :
-
Discount rate (%)
- \( C_{c} \) :
-
Capital cost ($)
- \( M_{c} \) :
-
Maintenance cost ($/yr)
- \( F_{c} \) :
-
Variable fuel cost ($/yr)
- j :
-
Number of periods in net present cost calculation
- \( m_{{CO_{{2^{e} }} }} \) :
-
GHG emissions in equivalent metric tonnes of CO2 (tonnes)
- AEO :
-
Annual energy output (MWh)
- \( e_{{CO_{{2^{e} }} }} \) :
-
Greenhouse gas emission factor (kg/MWh)
- k :
-
Fuel escalation rate (%)
- n :
-
System lifetime (yr)
References
Government of Canada: Canada’s 2017 Nationally Determined Contribution submission to the United Nations Framework (2017)
Environment and Climate Change Canada: Canada’s 2016 Greenhouse Gas Emissions Reference Case. Canada (2017)
Jordaan, S.M., Romo-Rabago, E., McLeary, R., Reidy, L., Nazari, J., Herremans, I.M.: The role of energy technology innovation in reducing greenhouse gas emissions: a case study of Canada. Renew. Sustain. Energy Rev. 78, 1397–1409 (2017). https://doi.org/10.1016/j.rser.2017.05.162
Natural Resources Canada: Energy Fact Book. Natural Resources Canada, Canada (2016)
Environment and Climate Change Canada: Canadian Environmental Sustainability Indicators Greenhouse Gas Emissions. Canada (2017). https://doi.org/10.1016/b978-0-12-409548-9.05178-2
Natural Resources Canada: Improving Energy Performance in Canada. Natural Resources Canada, Canada (2015)
Hepbasli, A., Biyik, E., Ekren, O., Gunerhan, H., Araz, M.: A key review of wastewater source heat pump (WWSHP) systems. Energy Convers. Manag. 88, 700–722 (2014). https://doi.org/10.1016/j.enconman.2014.08.065
Cipolla, S.S., Maglionico, M.: Heat recovery from urban wastewater: analysis of the variability of flow rate and temperature in the sewer of Bologna, Italy. Energy Proc. 45, 288–297 (2014). https://doi.org/10.1016/j.egypro.2014.01.031
Bertrand, A., Aggoune, R., Maréchal, F.: In-building waste water heat recovery: an urban-scale method for the characterisation of water streams and the assessment of energy savings and costs. Appl. Energy 203, 983 (2017). https://doi.org/10.1016/j.apenergy.2017.07.106
Wallin, J., Claesson, J.: Investigating the efficiency of a vertical inline drain water heat recovery heat exchanger in a system boosted with a heat pump. Energy Build 80, 7–16 (2014). https://doi.org/10.1016/j.enbuild.2014.05.003
Dong, J., Zhang, Z., Yao, Y., Jiang, Y., Lei, B.: Experimental performance evaluation of a novel heat pump water heater assisted with shower drain water. Appl. Energy 154, 842–850 (2015). https://doi.org/10.1016/j.apenergy.2015.05.044
City of Vancouver: Neighbourhood Energy Utility. City of Vancouver, Canada (2012)
FVB Energy.: Southeast False Creek Neighbourhood Energy Utility. http://www.fvbenergy.com/projects/southeast-false-creek-neighbourhood-energy-utility/ (2018). Accessed 2 May 2018
Im, P., Liu, X., Henderson, H.: Operational performance characterization of a heat pump system utilizing recycled water as heat sink and heat source in a cool and dry climate. Energies 11, 211 (2018). https://doi.org/10.3390/en11010211
Office of Institutional Research and Planning: Facts and Figures Carleton University. https://carleton.ca/about/facts/ (2017). Accessed 1 May 2018
Fuentes, E., Arce, L., Salom, J.: A review of domestic hot water consumption profiles for application in systems and buildings energy performance analysis. Renew. Sustain. Energy Rev. 81, 1530–1547 (2018). https://doi.org/10.1016/j.rser.2017.05.229
Symonds, G.: Carleton Facilites Management and Planning, Boiler Make-up Water. Personal Communication (2018)
Macdonald, S.: Carleton Facilities Management and Planning, Waste Heat Recovery Project. Personal Communication (2018)
Intertek Testing Services: Consumers’ Directory of Certified Efficiency Ratings for Heating and Water Heating Equipment. Intertek Testing Services, New York (2008)
Biermayer P, Lutz J.: Gas water heater energy losses. EScholarship, 1–23 (2009)
Aguilar, C., White, D.J., Ryan, D.L.: Domestic water heating and water heater energy consumption in Canada (2005)
Dürrenmatt, D.J., Wanner, O.: A mathematical model to predict the effect of heat recovery on the wastewater temperature in sewers. Water Res. 48, 548–558 (2014). https://doi.org/10.1016/j.watres.2013.10.017
International Renewable Energy Agency: Renewable Energy in District Heating and Cooling, A Sector Roadmap for REmap. UAE, Abu Dhabi (2017)
Parker, S.A., Boyd, B.K., Hunt, W.D., Stoughton, K.L.M., Fowler, K.M., Koehler, T.M. et al: Metering Best Practices: A Guide to Achieving Utility Resource Efficiency, Release 3.0. (2015)
Barfuss, S., Johnson, M., Neilsen, M.: Accuracy of In-Service Water Meters at Low and High Flow Rates. Logan, USA (2011)
Gruskos, R.: Utility Flow Metering for Steam and Heated/Chilled Water: A Tutorial. International District Energy Association (2015)
Szyszko, G.: Energy and Flow Measurement for Hydronic Systems. Association of Energy Engineers Southern California (2013)
City Of Ottawa: Lemieux Water Purification Plant—2017 Drinking Water Quality. Canada (2017)
City Of Ottawa: Britannia Water Purification Plant—2017 Drinking Water Quality. Canada (2017)
Office of Energy Efficiency & Renewable Energy: Purchasing Energy-Efficient Commercial Boilers. Washington DC, USA (2016)
Lunt, J.: Condensing storage water heaters. J Light Constr. 1–7 (2009)
SHARC Energy Systems: Technical Information: SHARC 660SS Wastewater Solids Filter. Canada (2015)
Maritime Geothermal: Engineering Specification: High Temperature Water to Water Heat Pump. New Brunswick (2018)
Mitsubishi Heavy Industries: Water to Water Centrifugal Heat Pump; Heat Recovery Type. Japan (2018)
Janna, W.S.: Design of Fluid Thermal Systems, Third. Cengage Learning, Stamford, USA (2015)
Cat Pumps: Pumps and Accessories Price List. Minneapolis, USA (2012)
Jenkins, G., Kuo, C-Y.: The economic opportunity cost of capital for Canada—An empirical update. Discount Rates Eval. Public Priv. Partnerships, Kingston, Canada (2008)
State of Michigan: Miscellaneous Industrial Costs, vol. 12. Lansing, USA (2003)
Thomson, J.A.: National Plumbing & HVAC Estimator. Associated General Contractors of America, Carlsbad, USA (2016)
US Energy Information Administration: Updated Buildings Sector Appliance and Equipment Costs and Efficiency (2016)
Duquette, J.: Carleton University, Cost Data. Personal Communication (2018)
Abdelalim, A., O’Brien, W., Shi, Z.: Visualization of energy and water consumption and GHG emissions: a case study of a Canadian University Campus. Energy Build 109, 334–352 (2015). https://doi.org/10.1016/j.enbuild.2015.09.058
Ontario Ministry of Energy: Ontario’s Long Term Energy Plan: Delivering Fairness and Choice. Ontario, Toronto (2017)
World Bank: Commodity Markets Outlook—World Bank. Washington DC, USA (2017)
SHARC Energy Systems: Case Study 1 Sharc System—Leisure Centre. Nottingham (2014)
United States Department of Energy: Geothermal Heat Pumps 2018, pp. 10–3. https://www.energy.gov/energysaver/heat-and-cool/heat-pump-systems/geothermal-heat-pumps (2018). Accessed 11 April 2018
The Atmospheric Fund: A clearer view on Ontario’s emissions: practice guidelines for electricity emissions factors (2017)
Office of Air Quality Planning and Standards AP-42: Compilation of Air Pollutant Emission Factors. North Carolina (1995)
US Environmental Protection Agency: Overview of Greenhouse Gases 2018, p. 5. https://www.epa.gov/ghgemissions/overview-greenhouse-gases#methane (2018). Accessed 12 April 2018
ASHRAE: ASHRAE Handbook—Service water heating. ASHRAE (2015)
Dewerth, D., Becker, B.: Comparison of collected and compiled existing data on service hot water use patterns in residential and commercial establishments (1993)
Carleton University: Carleton Dining Services 2018. https://dining.carleton.ca/ (2018). Accessed 2 May 2018
Culha, O., Gunerhan, H., Biyik, E., Ekren, O., Hepbasli, A.: Heat exchanger applications in wastewater source heat pumps for buildings: a key review. Energy Build 104, 215–232 (2015). https://doi.org/10.1016/j.enbuild.2015.07.013
Environment and Climate Change Canada: Technical Paper on the Federal Carbon Pricing Backstop 2017, p. 26 (2017)
Acknowledgements
The authors would like to thank the Carleton Discovery Center for partly funding this research through their ICUREUS programme. The authors would also like to thank Carleton University’s Facilities Management and Planning group for their close cooperation and support in acquiring building consumption data for this project.
Author information
Authors and Affiliations
Corresponding author
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2019 Springer Nature Switzerland AG
About this paper
Cite this paper
Chow, C., Duquette, J. (2019). Assessment of a Heat Pump-Based Wastewater Heat Recovery System for a Canadian University Campus. In: Vasel, A., Ting, DK. (eds) The Energy Mix for Sustaining Our Future. EAS 2018 2018. Springer Proceedings in Energy. Springer, Cham. https://doi.org/10.1007/978-3-030-00105-6_9
Download citation
DOI: https://doi.org/10.1007/978-3-030-00105-6_9
Published:
Publisher Name: Springer, Cham
Print ISBN: 978-3-030-00104-9
Online ISBN: 978-3-030-00105-6
eBook Packages: EnergyEnergy (R0)