Early last month, CMC’s Michael Ozeh, energy engineering manager, led a well-attended lunch-and-learn session on building electrification. For those of you who couldn’t attend, here’s some highlights of the event.
At its simplest level, energy efficiency focuses on reducing consumption, Ozeh said. Decarbonization focuses on reducing or eliminating carbon dioxide (CO2) emissions, primarily by switching from fossil fuels to clean energy sources, or by being more energy efficient. Electrification involves switching devices or processes that directly use fossil fuels to run on electricity such as switching gas furnaces to heat pumps.
“Energy efficiency and electrification, which we now know is a form of decarbonization, are not mutually exclusive; they often work best in tandem,” Ozeh said. “For instance, an energy-efficient home with high-performance insulation is better suited to benefit from electrification technologies like heat pumps. They are complementary strategies with shared goals.”
Within the building sector, the four key areas for electrification are space heating and cooling (using heat pumps), water heating (using electric or heat pump water heaters), cooking (using electric or induction cooktops) and laundry (using electric dryers). However, because heating and cooling systems typically account for a large portion of a building’s energy use, heat pumps are often a primary focus in discussions about building electrification.
How Does a Heat Pump Work?
The evaporator is the coil where the refrigerant absorbs heat (from outside in heating mode, from inside in cooling mode) causing it to evaporate (turn into a gas). Next, the compressor takes the low-pressure refrigerant gas from the evaporator and compresses it, significantly increasing its pressure and temperature.
The condenser causes the high-pressure refrigerant gas to release its heat (to the inside air in heating mode, to the outside air in cooling mode), causing it to condense back into a liquid. Finally, the expansion valve takes the high-pressure liquid refrigerant from the condenser and rapidly reduces its pressure (and consequently its temperature), preparing it to absorb heat again in the evaporator.
Although there are several types of heat pumps, the most common is the air source heat pump, Ozeh said. These units are suitable for mild and moderate climates and can be either ducted (like packaged heat pumps) or ductless (like most mini-splits) systems. Ductless Heat pumps are ideal for retrofitting homes without existing ductwork. For colder areas, there are cold-climate heat pumps that can efficiently heat homes in lower temperatures.
In contrast, ground-source heat pumps extract heat from the ground. They can maintain a more stable temperature and are more efficient in colder climates. They do, however, have a higher installation cost.
Heat pumps can use nearby water as a heat exchange medium, too. These are known as water-source heat pumps. This type of heat pump provides efficient heating and cooling and is great in areas with accessible and consistent water sources. The biggest challenge to water-source heat pumps is the necessity to be near a sufficient water supply.
“One of the biggest benefits of electrification is the significant cuts in greenhouse gas emissions, which combats climate change, especially when powered by renewable or clean electricity sources,” Ozeh said. “Electrification also improves air quality and public health by eliminating combustion emissions from vehicles and buildings, drastically improving outdoor and indoor air quality and reducing associated respiratory or health issues. This is particularly important in vulnerable communities.”