ARCHIVED - Effects of ECM Furnace Motors on Electricity and Gas Use

Download the full pdf document

Executive Summary

An evaluation of the impact of Electronically Commutated Motors (ECM*) on electrical and gas energy use has been carried out at the Canadian Centre for Housing Technology (CCHT) in Ottawa, Canada. The purpose was not only to demonstrate the ability of the high efficiency ECM motor technology to save large amounts of electrical energy in moving air in forced air heating and cooling systems, but also to quantify the amount of any extra natural gas that would be required during the heating season, and extra electrical energy that could be saved in the cooling season, in a climate that is typical of the Canadian winter heating season.

The two CCHT houses were benchmarked (run with the normal permanent split capacitor (PSC) fan motors in both) to show that their operation was nearly identical for 17 days during the heating season, and for 29 days during the air conditioning season. Heating season testing was done over 29 days between February 15th and May 25th 2002, and clearly showed significant reductions in the use of electricity, and corresponding increases in natural gas use. Cooling season testing occurred over 41 days between August 1st and October 3rd 2002, and showed reductions in electricity use for both the furnace fan and the air conditioner compressor.
The HOT2000 energy simulation model was used to generalize the results to an entire year, for both mid- and high-efficiency furnaces in a variety of house types in four Canadian cities. The house types are R-2000, typical new, typical existing, typical row, and typical row with ⅓ horsepower (HP) fan motors. (All other houses have ½ HP motors.) The cities are Winnipeg, Toronto, Ottawa and Moncton. Excluding the rows with ⅓ HP motors, the results for houses that operate the furnace fan in continuous circulation mode can be summarized as follows:

• Savings of electricity are more than 1,500 kWh/year in all cases. For houses without air conditioners, they range from 1,535 kWh/y in a new house in Ottawa and existing house in Toronto to 1,823 kWh/y in a row house in Moncton. With air conditioning, the range is from 2,795 kWh/y in an existing house in Winnipeg to 2,991 kWh/y in a row house in Moncton. As a percentage of electrical use by the entire house, the savings range from 13% to 18% without air conditioning, and from 20% to 25% with air conditioning. Electrical savings are independent of furnace efficiency.

• Increased use of natural gas due to an ECM is greater than 150 m3/year in all cases. It ranges from 152 m3/y in an R-2000 house with a high efficiency furnace in Toronto to 222 m3/y in an existing house with a mid-efficiency furnace in Moncton. The percentage increase in gas use for the entire house ranges from 4.7% in a typical existing house with a high-efficiency gas furnace in Ottawa to 9.7% in Moncton R-2000 and row houses with medium-efficiency furnaces. For the detached houses, the less energy efficient houses have larger increases in m3, but as a percentage of total they are smaller. Increases are higher with mid-efficiency furnaces.

• Natural gas prices in the four cities vary by 37%, and electricity prices vary by 60%, so one might expect net dollar savings to be most dependent on the price of electricity. In Winnipeg, which has the lowest electricity (and gas) prices, net savings due to an ECM are the smallest, ranging from $14 to $30 per year without air conditioning, and $81 to $106 with air conditioning. In Moncton, with the highest electricity (and gas) prices, the net savings in houses without air conditioning are the highest at $38 to $75, but the net savings with air conditioning are intermediate at $144 to $182. In Toronto, with intermediate electrical (and gas) prices, the net savings without air conditioning are intermediate ($40 to $ 68), but the savings with air-conditioning are the highest ($147 to $180.)(Savings in Ottawa are $1 to $7 less than in Toronto.) So net annual savings from an ECM can vary from $14 to $180 depending on the price of electricity and other factors. In detached houses, net savings are almost always higher in the more energy efficient ones, and are higher with high-efficiency furnaces.

• If electrical savings are assumed to be from coal-fired electricity, net reductions in greenhouse gas (GHG) emissions due to an ECM range from 1,314 to 1,674 kg CO2/y without air conditioners, and from 2,703 to 2,964 kg CO2/y with air conditioners.

• If GHG emissions are based on provincial mixes of generating fuels, the effects of ECMs on GHG emissions range from an increase of 381 kg CO2/y – in Winnipeg where most electricity is hydro-electric – to a decrease of 312 CO2/y. Only Moncton showed any decreases; in the other cities the smallest increase was 73 kg CO2/y.

The effects of ECMs on GHG emissions depend strongly on whether the saved electricity is coal-fired or produced by the average provincial mix. This is a controversial topic, with some people convinced that coal is always the “swing fuel”, and others claiming that this exaggerates the GHG reductions. Using the provincial mix probably underestimates reductions because it is likely that generation from fossil fuels would be reduced before those from capital intensive nuclear and hydro generation (both considered to produce no GHGs). For this reason, it seems most likely that ECMs do result in net GHG reductions in most or all cases, but the size of the reductions is debatable.

In houses that do not operate furnace fans in continuous circulation mode, the effects of ECMs are positive, but far less significant. The ranges are: Electrical savings: 128 to 434 kWh/y, natural gas increases: 11 to 29 m3/y, net dollar savings: 5 to 20 $/y, GHG reductions (coal) 116 – 424 kg CO2/y, and GHG effects (provincial mix): increase of 50 to reduction of 25 kg CO2/y. However, ECMs would allow such houses to switch to continuous circulation with no significant increase – usually a decrease – in utility bills. Continuous circulation provides benefits of more even distribution of fresh air and temperatures, and is especially important in houses that use the furnace fan to distribute fresh air to the house. Thus, ECMs can be part of a package promoting better circulation, comfort and health.

Gas utilities serve a mixture of houses that do and do not have continuous circulation. Some are involved in replacing furnaces, and so have an opportunity to promote furnaces that have ECMs and the capability of continuous circulation. Thus, the results have clearly demonstrated that ECMs can offer a unique gas load building opportunity to gas utilities, can save the typical homeowner money on overall energy costs, and offer benefits to the environment through reductions in GHGs associated with conventional electric power generation. The project has shown and confirmed that ECMs offer a unique fuel switching opportunity for natural gas to displace electricity with an overall efficiency about twice that of the best technology that currently exists for generating the same amount of electricity directly from natural gas.

The results also demonstrate the usefulness of the CCHT houses for carrying out important research projects on overall energy use, and their very sensitive ability to measure secondary and tertiary results of a very small change in one of the houses.