By Robert Brecha, University of Dayton [This article first appeared in The Conversation, reprinted with permission]
To help curb climate change, President Biden has set a goal of reducing U.S. greenhouse gas emissions by 50%-52% from 2005 levels by 2030.Achieving this will require converting as much fossil fuel-powered activity as possible into electricity as quickly as possible, and then generating electricity from low- and carbon-free energy sources such as wind, solar, hydro, and nuclear.
The buildings in which people live and work consume a lot of energy.Commercial and residential buildings accounted for more than one-seventh of U.S. greenhouse gas emissions in 2019.New heating and cooling strategies are an important part of this puzzle.
Fortunately, there is an existing technology that can do this: Electric heat pumps are three to four times more efficient than furnaces.These devices heat homes in winter and cool them in summer by moving heat in and out of buildings instead of burning fossil fuels.
As a scientist specializing in renewable and clean energy, I study energy use in housing and what climate change mitigation means for industrialized and developing countries.I think powering buildings with clean, renewable electricity is an important strategy that also saves consumers money.
Most heating systems in the United States use forced draft furnaces that run on natural gas or electricity, or in some cases heat oil.To heat a building, the system burns fuel or uses electricity to heat the air, which is then blown through ducts into individual rooms.
A heat pump works more like a refrigerator, extracting energy from the air inside the refrigerator and dumping that energy into the room, making it cooler.To heat a building, a heat pump takes energy from the outside air or the ground and converts it into heat for use in the house.
Here’s how it works: Extremely cold liquid circulates through the coils of the heat pump outdoor unit.The fluid absorbs energy in the form of heat from the surrounding air, which is hotter than the fluid.The fluid evaporates and then circulates into the compressor.Compressing any gas heats it, so the process generates heat.The steam then moves through coiled tubing in the heat pump indoor unit to heat the building.
In the summer, the heat pump operates in reverse, taking energy from the room and transferring heat outside, even though it’s hotter outside — basically, it functions like a bigger version of the refrigerator.
Heat pumps require some electricity to operate, but relatively few.Modern heat pump systems transfer three to four times as much thermal energy in the form of heat as the electricity consumed to do the job, and homeowners pay for it.
By contrast, converting energy from one form to another, as traditional heating systems do, always wastes some energy.This is true of burning oil or gas to heat the air in a furnace or using an electric heater to heat the air – although in this case there is waste in generating electricity.About two-thirds of the energy that power plants use to generate electricity is lost in the process.
Retrofitting residential and commercial buildings with heat pumps can improve heating efficiency.When combined with the switch from fossil fuels to renewable energy, it can further reduce energy use and carbon emissions.
Increasing restrictions and aggressive policies on the use of fossil fuels are driving sales of heat pumps in the U.S. and internationally.Heat pumps are currently used in 5% of the world’s heating systems, a proportion that needs to increase to a third by 2030 and even higher after reaching net-zero emissions by 2050.
In warmer regions where heating needs are relatively low, heat pumps are less expensive to run than furnaces.Tax credits, utility rebates or other subsidies may also provide incentives to help cover up-front costs, including federal incentives reinstated by the Biden administration.
In extremely cold climates, these systems have an additional internal heater to help.The unit is not very efficient and can significantly increase electricity bills.People living in cold regions may consider geothermal heat pumps as an alternative.
These systems take advantage of the fact that the ground is warmer than the air in winter.Geothermal systems collect heat from the earth and transfer it into buildings using the same fluid and compressor technology as air source heat pumps.They are more expensive because installing them involves digging to bury the pipes in the ground, but they also reduce electricity usage.
The new, smaller “mini-split” heat pump system works well in all but the coldest climates.These systems do not require ducts to carry air through the building, but connect to wall-mounted units to heat or cool individual rooms.They are easy to install and can optionally be used in a single apartment, making it easier to retrofit larger buildings.
Even with the best heating and cooling systems, installing proper insulation and sealing a building’s leaks is key to reducing energy use.You can also experiment with your thermostat to see how much you can heat or cool your home while keeping everyone comfortable.
To help determine if a heat pump is right for you, a good source of information is your electricity provider.Many utility companies offer home energy audits that can identify cost-effective ways to make your home more energy efficient.Other good sources include the U.S. Department of Energy and the U.S. Council for an Energy Efficient Economy.As the push to electrify society gathers pace, heat pumps are poised to play a central role.
[The Conversation's science, health and technology editors pick their favorite stories.every Wednesday.]
This article is republished from The Conversation under a Creative Commons license.Read the original text.
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