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Low hanging fruit in decarbonisation of buildings? Wastewater Heat Recovery (WWHR) systems



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Every day, more than 22,000,000 m³ of hot water are consumed by European homes alone. It is a major source of energy consumption for new housing, and yet 80 percent of this heat ends up in sewers and is wasted. Considering hot water is mostly used in showers, recovering waste heat from shower drains could be a simple way to save up to 70 percent wasted energy and related CO2 emissions.

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Low hanging fruit in decarbonisation of buildings? Wastewater Heat Recovery (WWHR) systems

  1. 1. Low hanging fruit in decarbonisation of buildings? Wastewater Heat Recovery (WWHR) systems Robert Pintér, European Copper Institute, Green and Healthy Buildings Team Leonardo ENERGY Webinar, 26 November 2020, 13:00 CET
  3. 3. Introduction • EC: buildings are responsible for approximately 40 percent of energy consumption and 36 percent of CO2 emissions in the EU • New built sector: growing share of energy to produce hot water, dramatic fall in energy needed for space heating • Daily 22 million m3 hot water used in EU homes • 80 percent of the heat ends up in sewers • Up to 70% of energy wasted in shower drains can be cost effectively and simply recovered | Wastewater Heat Recovery (WWHR) systems3
  4. 4. Growing share of energy for hot water production (Switzerland) | Wastewater Heat Recovery (WWHR) systems4 Source:
  5. 5. How WWHR works? • No moving parts, no electricity required (mostly) • A heat exchanger transfers heat energy of wastewater to incoming fresh water supply and warming it from around 10 up to 30°C • Why showers? • Highest consumption of hot water (≈ 80%) • Hot water demand and drain water available simultaneously • Easy heat exchange • Relatively unpolluted wastewater, ideal for heat exchange • A wastewater heat recovery system could effectively recapture and reuse instantly up to 70 percent of waste energy, reducing energy consumption in a cost-effective manner. | Wastewater Heat Recovery (WWHR) systems5
  6. 6. Basic Principle | Wastewater Heat Recovery (WWHR) systems6 Fresh water incoming at 10°C preheated to 30°C arriving at the mixing valve, reducing the need for hot water from the boiler. For more schemes (individual and multi-dwelling solutions) see the White paper
  7. 7. Product examples Horizontal type heat exchangers | Wastewater Heat Recovery (WWHR) systems7
  8. 8. Product examples Vertical type heat exchangers | Wastewater Heat Recovery (WWHR) systems8
  9. 9. Installation Plumber connects: • potable water in- and outlets (preheated) • Drainage out- and inlet (vertical) For manufacturers, product specifications visit: WWHR Europe | Wastewater Heat Recovery (WWHR) systems9
  10. 10. Product safety In WWHR systems double-walled heat exchangers are required by EN 1717 “Protection against pollution of potable water in water installations and general requirements of devices to prevent pollution by backflow”. Double-walled tubes ensure that domestic hot water and grey water are reliably separated. Moreover, the standard-compliant leakage gap makes it possible to detect leakages. | Wastewater Heat Recovery (WWHR) systems10
  11. 11. Efficiency • The lower the flow rate, the higher the efficiency – the higher the flow rate – the higher the performance. • Efficiency, as a percentage of energy gained from drain water varies by systems used, up to the value of around 70 percent. | Wastewater Heat Recovery (WWHR) systems11 Vertical type heat exchanger with over 60% efficiency.
  12. 12. Efficiency | Wastewater Heat Recovery (WWHR) systems12
  13. 13. Where to use WWHR systems? Residential • single family houses • multifamily houses Non-residential with higher hot water consumption • sport facilities, hairdressers, hotels, swimming pools… Due to ease of installation ideal for also for renovation. | Wastewater Heat Recovery (WWHR) systems13
  14. 14. Current market situation • Europe has the greatest technological lead in the world on this subject, with 326 patent applications since 2010, which is 70 percent of all patent applications in the world. • Together, WWHR systems have already recovered 300 GWh corresponding to the annual domestic hot water consumption of 17,000 households. | Wastewater Heat Recovery (WWHR) systems14
  15. 15. Acknowledgement of WWHR technology in national building codes and standards • France: RT2012 and forthcoming RE2020 where WWHR can contribute to targets for heat from renewables. • The Netherlands: WWHR systems are included in the calculation software for new construction projects as they have a positive bearing on the energy performance of a building. This is the case for the existing EPC (energy performance certificate) regulation. It will also be the case with the BENG (nearly energy neutral buildings) regulation that will be used from 01 January 2021. • UK: In October 2019, the Ministry of Housing, Communities and Local Government (MHCLG) published a consultation on the Future Homes Standard, regarding changes to Part L of the Building Regulations for new dwellings. WWHRS is widely recognised as one of the most cost- effective SAP-listed energy efficiency technologies available, and proposed changes to Part L in 2020 suggest WWHRS will have an even bigger impact under the new regulations. | Wastewater Heat Recovery (WWHR) systems15
  16. 16. Energy and CO2 emissions calculation of a sample household Energy consumption and emissions of shower systems depend on many variables, e.g. temperature of incoming cold, hot water and shower water used, shower time, fuel used to heat water (electricity, gas…) size/design of shower enclosure and flow rate. In our example: | Wastewater Heat Recovery (WWHR) systems16 Shower time: 9 min./shower Cold water temperature: 10°C Hot water temperature from the boiler: 60°C Mixed shower water temperature: 38°C Flow rate: 9.2 l/min Number of days: 365 Number of residents per home: 2.30 CO2 emission coefficient (based on Dutch standard NTA8800, “Energy performance of buildings - Determination method): Electricity: 0.34 kg/kWh Gas: 0.183 kg/kWh WWHR unit efficiency: 56% (market average)
  17. 17. Energy and CO2 emissions calculation of a sample household In this sample household, with deployment of an average efficiency (56%) WWHR system, 833 kWh electrical energy and related 283 kg of CO2 emissions can be saved, or consumption of 85 m3 natural gas, equivalent to 153 kg CO2 can be avoided. 37% of energy consumption and CO2 emissions avoided | Wastewater Heat Recovery (WWHR) systems17 Household Without WWHR Household With WWHR Household Saving with WWHR Hot water preparation Energy demand per year CO2 emissions per year Energy demand per year CO2 emissions per year Energy saving per year CO2 emissions saving per year Electricity 2,264 kWh 770 kg 1,430 kWh 486 kg 833 kWh 283 kg Gas 231 m3/year 414 kg 144 m3/year 262 kg 85 m3/year 153 kg
  18. 18. RETURN ON INVESTMENT • Electricity and natural gas prices vary across Member States and there is a wide range of WWHR systems available on the market, so the exact return on investment needs to be calculated specifically for each project. • An average family can save around €50-150 annually on their hot water bill after deployment of a WWHR unit and this justifies the investment into this safe, energy efficient, environmentally friendly, simple, and easy to install, operate and maintain system with a long lifespan. | Wastewater Heat Recovery (WWHR) systems18
  19. 19. EU 28 Energy Statistics, 2017 19 Item Value Energy for domestic hot water preparation 495 TWh Share of hot water used for shower out of total hot water used in households (see table below) 80% Energy for shower hot water in households 396 TWh Final energy consumption 12 329 TWh Household's final energy consumption 3 344 TWh Share of hot water in households final energy consumption 14,8% Share of hot water used for shower in final energy consumption 3,21% Use of hot water in households according to JRC report “MEErP Preparatory Study on Taps and Showers” Share Bath 6% Shower 80% Tap, washbasin 7% Tap, kitchen - drinking/cooking 0% Tap, kitchen - dish washing 5% Tap, indoor - clothes washing 2% Tap, indoor - other uses 0% Outdoor 0% Total hot water demand in taps and showers 100% | Wastewater Heat Recovery (WWHR) systems
  20. 20. Energy demand and carbon footprint of shower hot water in the EU / saving potential | Wastewater Heat Recovery (WWHR) systems20 Type of fuel Share (2017) Gas 47% Electricity 19% Oil and petroleum products 11% Derived heat 11% Solid fuels 2% Renewables and wastes 10% Share in heating shower hot water Energy Demand Total (TWh/y) Saving potential with WWHR (37%) (TWh/y) CO2 emission coefficient (NTA 8800) kg/kWh CO2 emissions (million tonnes/y) Saving potential with WWHR (37%) (m. t./y) Electricity 19% 74.89 27.21 0.34 25.46 9.92 Gas 47% 189.91 70.27 0.183 34.75 12.86 TOTAL 264.81 97.98 60.22 22.28 66%
  21. 21. 2030 WWHR SCENARIO – ENERGY SAVING POTENTIAL IN 2030 By 2030: • Renovation Wave Strategy: 35 million buildings renovated (82% residential) • New dwellings: 16 million completed 2030 WWHR scenario: annual savings in 2030 if WWHR deployment rate is 50% | Wastewater Heat Recovery (WWHR) systems21 Renovated Newly built Number of dwellings by 2030 28 700 000 16 000 000 2030 WWHR Scenario – number of dwellings by 2030 (50 percent of dwellings deploying WWHR) 14 350 000 8 000 000 Household annual energy saving (kWh/year) See household level table 800 800 Total annual energy savings in 2030 (TWh/year) 11.48 6.40 Grand total energy savings in 2030 (TWh/year) 17.88 Grand total energy savings in 2030 (Mtoe/year) 1.54
  22. 22. Energy and GHG emissions savings by Renovation Wave Communication „The Commission has proposed in the Climate Target Plan 2030 to cut net greenhouse gas emissions in the EU by at least 55% by 2030 compared to 1990.” „To achieve the 55% emission reduction target, by 2030 the EU should reduce buildings’ greenhouse gas emissions by 60%, their final energy consumption by 14% and energy consumption for heating and cooling by 18%” (compared to 2015) | Wastewater Heat Recovery (WWHR) systems22 GHG and final energy savings in buildings Final Energy Consumption (Mtoe) -14% (2030 vs. 2015) GHG (Mton CO2-eq) -60% 2030 vs. 2015) 2015 370 456 2030 (BSL scenario) 334 239 2030 Green Deal (REG scenario) 320 180 Savings needed 50 276
  23. 23. Contribution to 2030 targets of the Renovation Wave – 2030 WWHR scenario | Wastewater Heat Recovery (WWHR) systems23 Share of WWHR in final energy savings target of the RW: 3.07% WWHR contribution (1,54 Mtoe) Share of WWHR in GHG emissions savings target of the RW: 8.07% WWHR contribution (22,28 Mt)
  24. 24. Additional Benefits • Hot water preparation system can be designed smaller • Reduced capacity of installed renewable systems (photovoltaic, solar thermal or heat pumps) or renewable energy generated on site can be used for other purposes than hot water. • Circular construction: systems have a long lifespan and contain easy to recycle and highly recycled materials (copper, stainless steel). • Real time production: the recovery and generation of energy adapt continuously and in real time with the usage, without over-or under- production (no storage and control system necessary) • Aesthetics: systems are integrated into showers, in ducts or technical rooms, so they are hidden. | Wastewater Heat Recovery (WWHR) systems24
  25. 25. Policy recognition needed for WWHR Foster use of systems  EPBD article 2: WWHR to be defined as „energy from renewable sources”.  EPBD to recognise WWHR as energy source generated on-site in primary energy factors used for the determination of the primary energy use expressed in kWh/m2/year with the aim to take contribution of WWHR to energy savings into account. In the definition of NZEB, recognition is needed that WWHR can reduce hot water needs.  EPBD to introduce a building renovation passport (as proposed in the Renovation Wave) to provide long-term, step-by-step renovation roadmap, explicitly including WWHR systems.  EPBD to introduce minimum energy performance standards for existing buildings (as proposed in the Renovation Wave), to reach a minimum renovation rate, consider WWHR in calculations  EPBD to introduce a ‘deep renovation’ standard (as proposed in the Renovation Wave), explicitly including WWHR.  RED (or/and EPBD) to introduce requirement to use „Minimum levels of renewables in buildings” (as proposed in the Renovation Wave), facilitate use of waste heat at building level, take WWHR contribution into account Energy Performance of Buildings Directive Renewable Energy Directive | Wastewater Heat Recovery (WWHR) systems25
  26. 26. Policy recognition needed for WWHR Foster use of systems  Energy labelling: package label for heating systems: possibility to include WWHR as a subsystem in the label (next to solar collectors, storage tanks, controllers, …) Ecodesign and Energy Labelling  Article 14 (Promotion of efficiency in heating and cooling): Member States shall include wastewater heat recovery systems in buildings in their energy efficiency and renovation programs (Long Term Renovation Strategies). Energy Efficiency Directive | Wastewater Heat Recovery (WWHR) systems26
  27. 27. Locker room showers : one collective WWHRS or multiple individual WWHRS ? Case study: Public swiming pool in Cernay, France. Built in 2020 34 showers Hugo Durou, European Association for WWHR, Nov. 26th 2020
  28. 28. individual WWHR 260mm 450 mm 460 mm isometric view Obox
  29. 29. WWHR showers 1 & 2 cold water water heater cold water mixer overflow drain WWHR showers 3 & 4 cold water mixer WWHR showers ... cold water mixer drain WWHR showers 33 & 34 cold water mixer overflow overflow overflow individual WWHR × 17 Obox
  30. 30. collective WWHR grey water grey water to sewerSupporting poles Load = 100 kg black water 758 753 803mm 147 mm Obox C
  31. 31. collective WWHR shower room #1 water heater mixer shower room #2 mixer shower room #3 mixer drain WWHR shower room #4 cold water mixer overflow cold water Obox C
  32. 32. énergie perdue dans les tubes avant Obox C 23% énergie perdue parce que montage "ballon seul" 26% énergie perdue parce que Obox C n'a pas 100% d'efficacité 18% énergie récupérée par Obox C 33% individual WWHR collective WWHR Energy lost in pipes before Obox C 27,3 MWh/yr Energy because preheating only water to water heater 30,6 MWh/yr Energy lost because Obox C has not 100% efficiency 21,3 MWh/yr - Energy recovered 39,8 MWh/yr Energy lost before Obox 16,8 MWh/yr Energy lost because preheating only water to shower mixer 34,1 MWh/yr Energy lost because Obox has not 100% efficiency 15,7 MWh/yr - Energy recovered 52,4 MWh/yr Energy lost in pipes before Obox C Energy lost because preheating only water to water heater Energy lost because Obox C has not 100% efficiency Energy recovered énergie perdue dans les tubes avant Obox C 14% énergie perdue parce que montage "ballon seul" 29% énergie perdue parce que Obox C n'a pas 100% d'efficacité 13% énergie récupérée par Obox C 44% Energy lost in pipes before Obox Energy lost because preheating only water to shower mixer Energy lost because Obox has not 100% efficiency Energy recovered × 17
  33. 33. Energy recovered 39,8 MWh/yr Hot water energy reduction -33% Cost (WWHRS hardware) 8 433 € Cost (installation) 1 200 € Payback / ROI 3,3 yr Energy recovered 52,4 MWh/yr Hot water energy reduction -44% Cost (WWHRS hardware) 9 846 € Cost (installation) 6 000 € Payback / ROI 4,1 yr individual WWHR collective WWHR × 17
  34. 34. Robert Pinter, European Copper Institute Hugo Durou, European Association for WWHR Thank you | Presentation title and date34 For more information please contact