Canadian households consumed 1.3 million terajoules of energy in 2015. Natural gas accounted for 51% of the total energy consumed. Alberta consumed the most natural gas when compared to other provinces with an average annual use of 117.3 gigajoules per household (Canada(a), 2017). In Alberta, furnace heating systems account for 94% of the equipment used in households, with natural gas being the primary heating fuel at 91% (Canada(b), 2011). Currently, alternative forms of heating through the use of renewable energy, such as wind and solar power, accounts for less than 2% of the energy consumed for space heating (Canada(b), 2011).
With Canada’s commitment to the Paris Agreement, which aims to accelerate actions and towards a sustainable low carbon future (NRC, 2020), alternative forms of space heating are required to reduce the carbon footprint of this sector. The main type of space heating equipment used in Canada are forced air furnaces and electric baseboard heating systems, accounting for a 57% and 27% share respectively of all types used (Canada(c), 2020). The purpose of this report is to perform a life-cycle analysis of the current space heating technology used in the municipality of Calgary, Alberta.
Key environmental, economic and social indicators will be identified and reviewed for the purpose of developing functional units. The functional units will serve as the comparative basis for the evaluation of an alternative to natural gas based forced air space heaters. Life–cycle assessment is a cradle to grave evaluation of a current practise’s sustainability which includes all processes involved with the procurement of raw materials to the disposal and re-use at the end of a product’s life.
Omitted from the analysis is the energy required to transport, install and dispose of the conventional HVAC unit and the “Alternative Technology”. Figure 1 – Primary heating systems in Canada (Canada(b), 2011) Figure 2 – Average energy use per household in Canada by province (Canada(a), 2017) The amount of energy used
For the purpose of this review, the energy consumed per household in Calgary will be based on average values that have been listed above from available data for Canada, Alberta and Calgary statistics. Figure 3 – Average energy use per household in Canada by dwelling type (Canada(c), 2020)
A forced air furnace uses natural gas as a fuel source, with electricity used as a secondary source, to heat air that pulled in from outside the dwelling. The burner assembly uses a spark to ignite a mixture of natural gas and air. The air that is heated from the combustion process passes through a heat exchanger to heat air that is then circulated thought-out the building. The furnace is typically manufactured from materials such as steel, galvanised steel, aluminium and cooper with an estimated life span of 20 years (Shah, Col-Debella, & Ries, 2008). Figure 4 – Schematic of a forced air furnace system (https://www.crystalflash.com/news/furnace-not-working/)
Operational Energy Use and Carbon Intensity
Based on the data obtained from various sources – (Canada(a), 2017) (Canada(b), 2011) (Canada(c), 2020) – households in Alberta used on average 117.7 gigajoules of energy per year. 51% of the total consumed energy use is in the form of natural gas. Natural gas consists of roughly 90% methane and has an energy density of roughly 55MJ/kg (Hanania, et al., 2020). This equates to average usage of natural gas of 1,091 Kg of natural gas per household per year. According to the Energy Information Administration, natural gas emits 50.3 kg of CO2e per GJ of gas burned (EIA, 2020).
This would result in the average household producing 3,020 kg of C02 per year. According to the 2016 census, the number of occupied private dwelling is Calgary is 519,685 (Canada(d), 2017). This will result in 1.57 million tonnes of C02 emitted per year by households in Calgary. Alberta average for the residential section is 8,056 kT based on values from 1990 to 2017 (Canada E. a., 2020). The CO2 emitted in Calgary would amount to 20% of all province wide residential emissions. Need to add estimates of CO2 emissions for manufacturing of the units.
Embodied and Operating energy
The embodied energy of a building element is the energy consumed through the manufacture, transport, installation, operation and maintenance through to the final disposal. There are challenges associated with estimating the embodied energy or carbon used to produce a conventional HVAC system. This can be attributed to the numerous materials needed to produce the system and data gaps which result in a more difficult task in estimating the life cycle embodied energy of HVAC systems and other materials used in building construction (Medas, Cheshire, Cripps, Connaughton, & Peters, 2016). For the purposes of this study, only the manufacturing and operating energy will be considered for the comparison.
As significant amounts of energy are required to manufacture HVAC systems, omitting the embodied energy would be an oversight when trying to compare a fossil fuel burning system to one that utilizes a renewable energy source such as solar. To provide a reliable method for comparison, the embodied energy should be quantified for a total life cycle assessment. (Koubogiannis & Nouhou, 2016) has shown the embodied energy of a steel heating system can be estimated by multiplying the mass of the heating unit by 26MJ per Kg. This encompasses the energy required to manufacture the materials used in construction and the energy used in the assembly of the unit.
Gas furnace product specs were reviewed to determine typical weights of furnaces used in Calgary. They were found to vary between 120 and 160 lbs or 55 kg to 75 kg (Goodman, 2020). This would result in an embodied energy of 1.43 to 1.95 gigajoules for a furnace unit through applying the values estimated by (Koubogiannis & Nouhou, 2016). The total life-cycle energy costs can be estimated by combing the embodied energy from the manufacturing with the operational energy use through the combustion of natural gas.
The average value estimated for the embodied energy is 1.69 GJ (1.43 + 1.95 / 2 = 1.69 GJ). The life-time operational energy use of the unit can be estimated as 1,200.5 GJ (117.7 x 51% GJ/year over a 20 year lifespan = 1,202.23 GJ) of energy. Thus, the manufacturing process only accounts for 0.14% of the life cycle energy consumption. Displacing the energy use of natural gas provides the unique opportunity to reduce the overall the dependence on fossil fuels and lower the greenhouse gas emissions significantly for this sector.
Economic and Social Indicators
Purchase, Operational and maintenance Costs
The average cost of natural gas from the past 2 years (Alberta, 2020) is: • $1.84 / GJ – Regulated Rate • $3.98 / GJ – Fixed Rate • $2.89 / GJ – Variable Rate The cost of natural gas is relatively low but other administrative and distribution charges account for roughly 60% of the billing costs to the consumer based on the fixed natural gas rate (Alberta, 2020). Using the amount of energy consumed by Albertan households from the data above, a household can expect to pay between $8 and $10 per gigajoule of natural gas supplied. This would cost the consumer $470 to $600 per year, depending on the rates chosen.
Over the lifetime of the unit assuming 20 years operation, this translates to a cost of $9,400 to $12,000 to operate. These values correlate well with the national average costs established by the Energy Start program for small to medium size high efficiency furnaces (Energy-Star, 2020). Typical purchase prices vary from $3000 to $6000 in Calgary (Furnaceprices.ca, 2020). This price band applies to typical high efficiency furnaces of 80% annual fuel utilization efficiency (AFUE) and up.
Installation is usually also included in this cost. Homeowners in Calgary can expect to pay up to $150 dollars per year for basic maintenance. More significant costs can be incurred to repair more crucial components of furnace such as the furnace motor or heat exchanger. Repairs of this nature can cost between $1,200 and $2,400. The total installation, operating and maintenance costs of a furnace can now be estimated.