Greenhouse gas emissions from the transportation and heating sectors
Fossil fuels used in the production of electricity produce 28% of our greenhouse gas emissions. One would think that reducing our electricity usage would reduce our greenhouse gas emissions. But, some experts suggest that just the opposite is true. They say that we can reduce our greenhouse gas emissions by increasing our electricity consumption for electric vehicles and heat pumps.
Reducing electricity usage would reduce the greenhouse gas emissions associated with the production of electricity. However, electricity is not our only source of greenhouse gas emissions.
We use fossil fuels for 90% of our transportation requirements. And we use fossil fuels for almost all of our residential and commercial heating requirements. This usage accounts for 29% and 12% of greenhouse gas emissions respectively. We can reduce greenhouse gas emissions in these sectors only by reducing their use of fossil fuels. In both cases electricity is the only available alternative to fossil fuels.
Many experts view electric vehicles (EV) as the best way to reduce greenhouse gas emissions in the transportation sector. And state and federal governments are already offering incentives for drivers to purchase EVs. However, only 2% of new cars sold in America are EVs. Buyers have been slow to embrace EVs because of the following:
- Time it takes to charge the vehicle;
- Range of driving on a single charge;
- Cost as compared to conventional cars; and
- Lack of charging stations.
The automobile industry is working on these issues. And it will probably resolve them within the next several years. However, even if the American public fully embraces EVs, there is a question of the extent to which EVs will actually benefit the environment.
EV tailpipe emissions (including emissions associated with electricity used to charge the battery) are less than conventional auto tailpipe emissions. But tailpipe emissions are not the only source of greenhouse gas emissions. The “well to wheel” emissions – that is, tailpipe emissions plus the emissions from electricity required to produce the automobile – must also be considered. And, because of the electricity required to produce the EV battery, it takes more electricity to produce an EV than to produce a conventional auto.
Based on today’s mix of electricity production facilities the “well to wheel” emissions for EVs may actually be greater than for conventional autos. We will not, therefore, get the full benefit of EVs until more electric production is converted from fossil fuels to renewables.
Historically, we have used fossil fuels for almost all of our space heating requirements. But, during the 1970s there was a perception of a natural gas shortage. Without the availability of natural gas we started to use heat pumps fueled by electricity for space heating. After natural gas was once again readily available, heat pumps fell out of favor. In many cases the heat pumps installed in the 1970s were removed and replaced by conventional fossil fueled furnaces. Today, we get virtually all of our space heating from furnaces fueled by natural gas, oil or propane.
Now, with fossil fueled furnaces identified as a source of greenhouse gas emissions, heat pumps are getting a new lease on life. Heat pumps operate in the same way as air conditioners. In an air conditioner the hot air inside the home is transferred to a coolant which is condensed and compressed to transfer the heat outside. In a heat pump the hot air outside the home is transferred to a coolant which is condensed and compressed to transfer the heat inside. Although it may seem counterintuitive, outside air that is as cool as 32 degrees Fahrenheit contains enough hot air to be useful in a heat pump operation. When the outside air goes below 32 degrees the heat pump must use some type of auxiliary heating system to heat the indoor air.
The following video explains the operation of a heat pump:
Heat pumps operate on electricity. And electricity generation produces greenhouse gas emissions. However, even with today’s mix of electric generation facilities, the greenhouse gas emissions from the electricity used to run a heat pump are less than the greenhouse gas emissions produced from a fossil fueled furnace. And the greenhouse gas emissions associated with heat pump usage will further decrease as more electric production is converted from fossil fuels to renewables.
Conversion to EVs and Heat Pumps
No one is going to ask us to immediately replace our conventional autos and fossil fueled furnaces with electric vehicles and heat pumps. In fact, until more of our electric generation comes from renewables the electrization of the transportation and space heating sectors might have limited benefits. Therefore, conversion to electric vehicles and heat pumps should occur over the next 10 or 20 years in parallel with the greening of electric production.
It should also be noted that the current electric generation mix is geared towards meeting a peak demand that occurs on hot summer afternoons when air conditioners are in use. The increased electric consumption associated with the electrization of the transportation and heating sectors could cause a shift in the electricity load curve. This shift will have to be accommodated as new generating plants are added to the system.
I. David Rosenstein worked as a consulting engineer and attorney in the electric industry for 40 years. At various times during his career he worked for utility customers, Rural Electric Cooperatives, traditional investor owned regulated utilities and deregulated power generation companies. Each of his posts in this blog describes a different aspect of the past, present or future of the electric industry.