These are rough notes and only to be read in conjunction with the article “Weighing the environmental cost of cooling“.
Bosch Compress 3000 uses 0.375kg of R134A (ref brochure)
EcoSpring ES190 uses 0.8kg of R134A and the ES300 uses 1.2kg of R134A
Econergy HP4000LT uses 0.59kg of R134A (Ref technical installation manual)
R143a from California table for 100 year Global Warming Potential for R134A or HFC-134a which is Tetrafluoroethane the GWP = 1430 ref https://ww2.arb.ca.gov/resources/documents/high-gwp-refrigerants other sources quote 1300 with an atmospheric lifespan of 14 years the 40 year GWP would be similar.
The operational CO2-e for NZ electricity is around 0.1 kg CO2-e/kWh plus you need to add the estimated CO2-e for the systems/plant and grid transmission equipment. I actually think the 0.18 kgCO2-e/kWh used by NZGBC in their tools is reasonable.
In the future with a fully renewable grid the electricity will still have carbon emissions that need to be considered. The LCA for electricity for renewable energy (ignoring storage issues) ranges from 0.02 to 0.06 kgCO2-e/kWh wind/hydro/PV/tidal (Ref Life cycle GHG emissions of renewable and nonrenewable electricity generation technologies)
From Econergy website “*Based on a 0.6kgCO2/kWh generated as quoted in ‘MEPS & Alternative Strategies for External Power Supplies’, Punchline Energy, Feb 2007. Average hot water consumption 210L per day.”
Assuming you use 2800 kWh/year with an electric resistance tank heater and rough numbers use a COP of 3 over a minimal lifespan of 5 years which is better?
2800kWh/yr*5yr=14,000 kWh would range from 2,520 kgCO2e at 0.18 kgCO2-e/kWh to 840 kgCO2-e with local PV (assuming 0.06 kgCO2-e/kWh)
Heat Pump using BOSCH Compress and COP=3 and at 0.18 kgCO2-e/kWh yields 840 kgCO2-e plus 0.375kgR134a*1430CO2-e/kgR134a = 536 kgCO2e totals 1376 kgCO2e
at 0.06 kgCO2-e/kWh yields 280 kgCO2-e plus 0.375kgR134a*1430CO2-e/kgR134a = 536 kgCO2e totals 816 kgCO2e. [45% to 3% savings in kgCO2e over 5 years]
—So this means that this DHW Heat Pump is better across the range of grid carbon intensities that make sense and is likely much better if we assume it lasts more than 5 years before leaking the entire refrigerant charge. As these are all-in-one units sealed and charged at the factory like a refrigerator I’d argue for much longer lifespans than 5 years. The oldest one I know of for certain is at PH1NZ <link> is over 8 years old. If we used a 20 year lifespan we’d have.
Heat Pump using EcoSpring ES300 with much higher refrigerant charge (highest I found) of 1.2kg of R134A and COP=3 and at 0.18 kgCO2-e/kWh yields 840 kgCO2-e plus 1.2kgR134a*1430CO2-e/kgR134a = 1716 kgCO2e totals 2,556 kgCO2e at 0.06 kgCO2-e/kWh yields 280 kgCO2-e plus 1.2kgR134a*1430CO2-e/kgR134a = 1716 kgCO2e kgCO2e totals 1996 kgCO2e
—So this means this Heat Pump is nearly the same after 5 years as the electric resistance tank and results in twice as much CO2-e as the electric resistance if we assume pure PV power on the grid and the refrigerant leaks out at 5 years.
[Should plot this data for the different tanks and Refrigerants.]
R32 has a GWP of 675 (two-thirds less than R410a)
For high wall heat pumps they are precharged (often R32) ranges from 1 kg for 3.2kW heating capacity to 1.2 for 7kW then jumps up. If we assume a Low Energy Building (approx 30 kWh/sqm/year for heating and 150 sqm) that’s 4,500 kWh/year with electric resistance heating or let’s just use 10 years before replacement and assume the gas is lost.
Electric resistance = 8,100 kgCO2e
HP (1.2kg of R32)=2,700+810 = 3,510 kgCO2e or 57% savings compared Electric resistance; For our current grid.
For a fully renewable grid
Electric resistance = 2,700 kgCO2e
HP (1.2kg of R32)=900+810 = 1,710 kgCO2e or only a 37% savings compared Electric resistance
Not free the best case would be to use CO2 refrigerant systems like the Mitsubishi EcoDan (Ecodan QUHZ 4.0kW) https://www.mitsubishi-electric.co.nz/ecodan-hot-water-heat-pump/default.aspx or the Reclaim Energy CO2 heat pump https://www.reclaimenergy.co.nz/co2-heat-pump-eco-hot-water/
Note that the Kigali Amendment which is ratified in NZ requires us to reduce HFCs by 85% by 2036. The NZ Government proposes to achieve this by establishing an import and export permitting system for bulk HFCs (that is, HFCs still in their pure form).
- New Zealand’s Greenhouse Gas Inventory 1990-2018, MFE 1496, April 2020. https://www.mfe.govt.nz/
- The Cost of Comfort: Climate Change and Refrigerants by Brent Ehrlich “For HVAC systems, the energy and carbon savings from their use usually outweighs the potential greenhouse gas emissions of the refrigerants over the equipment’s lifespan, but not if these systems are improperly installed, commissioned, or disposed of.” https://www.buildinggreen.com/feature/cost-comfort-climate-change-and-refrigerants
- Life cycle GHG emissions of renewable and nonrenewable electricity generation technologies – Part of the RE-Invest project Authors: Mafalda Silva and Hanne Lerche Raadal Report no.: OR.23.19 ISBN: 978-82-7520-806-2 ISSN: 0803-6659 “Wave and photovoltaic power present the highest contribution to GHG emissions for the considered renewable electricity generation technologies, with an average value of 55.9 and 50.9 g CO2-equivalent per kWh, respectively. Wind power, on the other hand, presents the lowest contribution to GHG emissions with an average contribution of 14.4 and 18.4 g CO2-equivalent per kWh for onshore and offshore locations, respectively. Hydropower presents the second lowest contribution to GHG emissions with reservoir plants presenting an average contribution of 21.4 g CO2-equivalent per kWh and run-of-river plants an average contribution of 19.1 g CO2-equivalent per kWh. Nonetheless, in comparison with the non-renewable technologies, renewable technologies present much lower GHG emissions.”
- “Hydrofluorocarbon consumption in New Zealand” by NZ Ministry for the Environment pub CR 293, August 2018 https://www.mfe.govt.nz/publications/climate-change/hydrofluorocarbon-consumption-new-zealand
Notes for use