UPDATE: This post was previously titled "4 reasons why heat pumps are not going to save the planet" which some readers thought was mean to heat pumps. But I will never change my position on calling them Geothermal.
I get very nervous, writing about heat pumps. Everybody yells at me. When I wrote a recent post about heat pump startup Dandelion, their publicist called it an "inaccurate rant" -and it is a spinoff from the "don't be evil" company so I must have been wrong. Our poor comments moderator has to take a day off every time I touch this subject. Or go back to one of my oldest posts on the subject and read my "uninformed drive-by 'journalism'."
But I can't help myself, banging my head against the wall on these issues, and I am going to do it again right now. I apologize in advance to our comments moderator. It started when I read David Roberts' article on VOX, Most American homes are still heated with fossil fuels. It’s time to electrify. He is right. But then he goes through the story of how he couldn't afford a heat pump or even a "fancy-pants ductless mini-split" to replace his oil furnace, so he piped in gas and has felt guilty ever since.He then lists 5 things we have to do to boost electrification, worrying about supply, without noting the single most important one: We have to radically reduce demand for energy. Those fancy-pants mini-splits are not very expensive at all if you have a well-insulated, well sealed house. That might have been hard to do in David Roberts' house but if the money that people spend on ground source heat pumps was put into insulation, windows and sealing properly, they probably wouldn't need ground source heat pumps.
Then TreeHugger Megan wrote New heat pump technology heats and cools houses at lower cost about a new "dual-source heat pump" which frankly sounded to me like the worst of both worlds. In one of her sources, a professor Greenough from a partner in the project, De Montfort University Leicester, is quoted:
Geothermal energy is the future – it’s a clean and sustainable source of power. It does not produce greenhouse gases that can be harmful to the atmosphere. Most people rely on gas but there is a limited supply of fossil fuels, whereas geothermal heat pumps can make use of the practically limitless heat from the sun that falls on the ground and warms the air around us.
Now I am loath to criticize another professor but really, after reading that feel that I have to go back and start over.
1. Heat pump systems should not be called Geothermal.
The term Geothermal should be reserved for "energy systems that rely on elevated temperatures deep underground from the Earth's mantle." That's what they do in Iceland. Proponents of using the word for heat pumps claim, like Professor Greenough, that the heat comes "from the sun heating the ground around us." But then what is "geothermal cooling"? A heat pump moves heat from inside the house to either the air or to the ground, in exactly the same way your fridge moves heat from your food to your house.
And it all gets more confusing and difficult for the Geothermal supporters, now that Air Source Heat Pumps are getting so efficient. Even they are beginning to realize that the sexy Geothermal name no longer fits for their businesses. Now, people have to decide among heat sinks: do you go ground source? Air source? Water source? Why is one "heated by the earth" and the air conditioner running backwards isn't? The difference is specious. This is not pedantry; it's confusing.
2. Heat pump systems are not necessary clean and sustainable.
Heat pump systems are not "a clean and sustainable source of power." They are not a source of power at all. Heat pumps are pumps. They are powered by electricity. You can't necessarily say "It does not produce greenhouse gases that can be harmful to the atmosphere"; If the electricity is made from fossil fuels then the heat pump is powered by fossil fuels. It is more efficient than direct resistance heating by electricity, but if the electricity is made from natural gas, because of generation and transmission inefficiencies, according to some calculations it is actually a less efficient source of heat than burning the gas directly.
3. Heat pumps will not make your home comfy and womb-like
David Roberts points to a post by Nate Adams, who writes that heat pumps can give you "womb-like comfort." Heat pumps do not deliver comfort. They deliver heat. But the house that Nate discusses has been insulated and sealed to reduce the heating load enough that the heat pump works. It is the windows and the walls and the air sealing that make the house comfortable, and the comfort would be identical whether there was an efficient heat pump or a furnace burning whale oil or coal. Read Robert Bean, who says "you simply can't buy comfort - you can only buy combinations of buildings and HVAC systems which if selected and coordinated properly can create the necessary conditions for your body to perceive comfort."
4. Heat pumps are not the answer, they are one of many tools.
I agree with David Roberts and Nate Adams, we have to Electrify Everything! Heat pumps and solar panels are all useful tools. But the first thing we have to do is use radical building efficiency to Reduce Demand! Renovate or build to Passive House standards or as close as you can get and then you have a wide range of technology options. And your home really will be comfy and womb-like.
The comments are now open.