Sustainable and Highly Efficient

By Anber Rana¹, Piyaruwan Perera¹, and Kevin Feddema^2
1PhD Candidates at UBC Okanagan
²Research Assistant at UBC Okanagan

“Canada’s cold climate means that space heating accounts for a remarkable 61% of the energy used in the average Canadian home. No wonder you should look into heating to find energy savings opportunities!” (NRCan, 2019). Ground Source Heat Pumps (GSHPs) for residential buildings result in 48% energy savings and 97% adverse environmental impacts reduction in the long-run^*.

^{*Compared to residential buildings constructed to comply with minimum requirements stated in the BC building code}

In Canada, residential buildings contribute to 14% of greenhouse gas (GHG) emissions due to their high-energy consumption and dependency on fossil fuels (NRCan, 2016). Hence, it’s vital to reduce extensive energy consumption and improve the utilization of low-emission renewable energy as their primary source of energy.  Since space heating is the forefront of the overall energy use and carbon emissions in Canadian homes, improving efficiency and reducing the use of fossil fuel for space heating can significantly help in addressing the climate change problem.

Domestic HVAC systems frequently contain a space heating system, a space cooling system, and a ventilation system. Homes with Natural Gas heating typically are heated by a furnace or a boiler. It also includes ductwork for forced air systems. In that case, separate equipment for space heating and space cooling is used. However, the heat pump is single all-in-one equipment that can be used for both space heating and cooling. Heat pumps are capable of operating year-round and are a sustainable option compared to conventional equipment.

The primary energy source of the heat pump is changed with the technology used. There are,

1. Air-source heat pumps: extracts heat from the air and transfers to either the inside or outside of the house depending on the season
2. Ground-source heat pumps (GSHP): transfers heat between the house and the ground (also known as earth energy systems)
3. Water-source heat pumps: transfers heat between the house and a nearby water source

GSHP systems are a proven technology that uses the ground as a source of heat in winter and as a sink during summer. Ground Source Heat pumps are known to have efficiencies ranging between 300%-400%; in comparison, the efficiency of gas furnaces are 98% or less.  The mechanism of the GSHP is shown in Figure 1.

The performance of a GSHP depends upon the size of the house as well as the level of insulation, window types, and air tightness. GSHPs are capable of working efficiently under extreme climate and hence, are considered very suitable for Canada’s climate. Typically, annual energy savings for homeowners can be reduced from 30%-70% in heating mode and 20%-50% in the cooling mode, compared to conventional natural gas heating and electric air conditioning systems.

HVAC Systems for Home of Today and Home of Tomorrow

Figure 3 Heating and Cooling Equipment for Wilden Living Lab Homes

This study assesses and compares the performance of 5 series (500A11) ground source heat pump and HVAC system composed of 92% efficient 60,000 Btu Natural Gas furnace with 14.5 SEER 3-ton AC.  Electricity use data for the system for the Wilden Living Lab homes was determined through real-time data monitoring. Figure 4 shows the electricity consumed for the year 2018 where it is seen that electricity bills are expected to be higher for Home of Tomorrow. However, the natural gas use for the Home of Today was 54.16 GJ higher than the Home of Tomorrow, which result in annual savings on utility bills.

Figure 4 Electricity Energy Use and Energy Costs for HVAC Systems in Wilden Living Lab homes

Table 1 shows a comparison of energy consumption, operational cost savings and payback period. It is seen that the overall GSHP in the Home of Tomorrow is providing energy cost savings of up to CA$ 453. Despite the savings in energy bills, a long payback period is associated with the high upfront costs of the Ground Source Heat Pump. Currently, there are no rebates or grants available for GSHPs or new constructions.

Table 1 Comparison of Energy Saving and Payback

The associated carbon footprint (see previous article on carbon footprint) for the HVAC system used in the home of tomorrow is 96.6% less than the conventional natural gas HVAC system used in the home of today. These savings equate to carbon dioxide absorbed by 144 tree seedlings. This shows the significance of GSHP as an environment-friendly technology to achieve provincial and national carbon emission goals.

In a nutshell, GSHP’s are more expensive than natural gas and electric furnaces. But as GSHP technology improves and more stringent actions are implemented to achieve low-carbon buildings the heat pumps may become more economical and environmentally friendly. In the long-run, electricity (hydro) and carbon tax associated with the natural gas become higher and payback times for GSHP may be reduced.

As an additional note, there are financial incentives and loan programs available to encourage existing electricity heated conventional systems to switch to air source heat pumps. The local utility in Kelowna provides rebates of up to CA$2,000 for homeowners who wish to switch to air source heat pumps. Alternatively, a low-interest loan of up to CA$6,500/unit for 10 years at 1.9% is being offered to reduce the burden of the upfront cost of air source heat pumps. However, there are no incentives or rewards available for the heat pumps for new constructions.

 Stay posted for more real-life data results in the future. In next month’s issue, we’ll talk about advantages of combining a geothermal heat pump with a solar PV system!

References

• Denis GS, Parker P. Community energy planning in Canada: The role of renewable energy. Renewable and Sustainable Energy Reviews. 2009 Oct 1;13(8):2088-95.
• Meanwell et al., Closing the Loop: A Survey of Owners, Operators and Suppliers of Urban Geoexchange Systems in the Greater Toronto Area. Toronto and Region Conservation Authority. 2015.
• Heerema D., Gas vs. electricity? Comparing home heating costs in B.C. Electric heat pumps offer several advantages over gas furnaces. Pembina Institute. 2017.
• Geotility. Geothermal heating and cooling systems by Geotility. 2019
• NRCan, Ground-source heat pumps.
• Karytsas, Spyridon, and Ioannis Choropanitis. “Barriers against and actions towards renewable energy technologies diffusion: A Principal Component Analysis for residential ground source heat pump (GSHP) systems.” Renewable and Sustainable Energy Reviews 78 (2017): 252-271.
• NRCan, 2016. Improving Energy Performance in Canada