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Heat Pumps: A Great Technology With a Few Drawbacks
We are at the beginning of a monumental shift in how we use energy.
Thousands of years ago, humans took the first significant step in using external sources of energy to perform work by burning wood. Today, even with a plethora of whiz-bang technologies, combustion (burning) remains the primary method of energy transfer in most developed countries. We burn gasoline in our cars and natural gas in our homes to heat water and heat spaces. We burn coal, oil, and natural gas to make electricity.
Unfortunately, the supply of dead dinosaurs (fossil fuels) is limited, and many regions that control vast energy resources are not friendly. Even with all our advances, we still fight wars over access to these resources.
The growth of renewable energy promises to change that. We're entering an era where, for the first time, people can get almost all their energy from the elements (wind, water, and sun) without burning things. Renewable energy has become cheaper than fossil fuels, a transition many predicted would never happen. Investment in renewables now makes sense from a business perspective. We are past the days of promoting renewable energy based only on the damage to our environment. Now even the most adamant climate deniers can embrace renewables based on price alone; that's a good thing.
Given the promise of low-cost, carbon-free, clean electricity, it's not surprising that a movement to "electrify everything now" has gained traction and is rapidly accelerating. While I don't necessarily disagree, if we want this movement to succeed, we must be honest about the risks and tradeoffs of adopting new technology.
Before rushing to electrify, we need to consider efficiency.
The car company Aptera is a great example of how combining efficiency with electrification can provide a solution for problems that are hard to solve with electrification alone.
Most car manufacturers are addressing range anxiety by installing bigger batteries. The problem is batteries are expensive and heavy. Plus, the larger the battery, the longer it takes to charge.
Aptera makes a car so efficient it can use a small battery and still provide plenty of range. The car has solar panels on the roof and can travel up to forty miles daily on sun power alone. The Aptera looks different and performs differently than every other car on the road. I am not suggesting it is for everyone, but it showcases the benefits of considering efficiency combined with electrification.
In buildings, the case for efficiency is even more straightforward. High-efficiency homes are easier to heat as they lose less energy via cracks and poor insulation. Heat pumps, the sweetheart technology for building electrification, have minimal excess capacity, which makes efficiency even more important.
Heat Pumps: A great technology with a few drawbacks
Heat pumps are time-tested technology and are a great way to remove combustion devices from buildings. Heat pumps are an excellent solution for the two most significant loads in buildings, space conditioning, and water heating. They are available now and can match or exceed the performance of their combustion appliances, but as with most things in life, there is no such thing as a free lunch.
Heat pumps move heat with refrigerants which absorb heat from one place and transfer it to another.
An air conditioner is a heat pump. Your house is cooled by removing heat from the inside, which is transferred to the outside via refrigerants. Reverse the process, and you can heat the home by moving the warmer air from outside to indoors. Even at frigid temperatures, there is heat in the air, and refrigerants can absorb this heat and move it inside to heat the home. It might seem like magic, but it is just physics at work. Heat pump water heaters work in the same way by absorbing heat from the air and transferring it to the water in a tank.
I was recently at a conference where several presentations promoted the benefits of heat pumps, and a couple pointed out some of their weaknesses. Ask your average heating and cooling professional about heat pumps, and you will often get mixed reactions. Some swear they don't work and will never install them. Good luck to them in 2030 when California bans natural gas heaters, and they go out of business.
Others are testing the water or installing heat pumps on a limited number of projects, often due to utility incentives. A few have embraced the technology and have built their business model based on heat pumps and their advantages.
My experience with heat pumps is that they work great but require a higher level of skill to install correctly. I have often said the problem with gas appliances is that they are cheap, easy to install, and they work. Heat pumps are not as forgiving. Successful adoption of heat pump technology relies on highly skilled technicians, at least today.
Refrigerants Are Not Perfect
The magic that happens with heat pumps requires refrigerants. Refrigerants are dangerous. The first refrigerant, ammonia, is highly toxic to humans in its gas state. If an early refrigerator developed a leak, it could kill the house's occupants. That's a pretty serious concern.
Propane is another excellent refrigerant. It just happens to be highly combustible.
More modern refrigerants have addressed these issues but have other problems. Most are terrible for the environment if released into the atmosphere. Many are thousands of times worse for the climate than carbon dioxide. The California Air Resources Board’s global warming potential (GWP) index gives carbon dioxide a GWP of one. R410a, a very common refrigerant used in residential systems, has a GWP of 2088. This means R410a does thousands of times more damage to the atmosphere when released than carbon dioxide.
The industry is responding slowly. Many heat pump systems require a technician in the field to connect the refrigerant lines as part of the installation. The process can be tricky as it often involves brazing, a process similar to welding. Other applications require flare fittings. The technician in the field must cut the refrigerant plumbing pipes (line sets) and then use a specialty tool to "flare" the end of the tube. The line is then connected to the unit and must be tightened to a specific torque. Remember what I said about needing highly skilled technicians to install heat pumps properly? There are many ways to mess things up, and environmental damage is significant when it happens. Am I downplaying this technology? Absolutely not, but I am pointing out that there is no free lunch.
Manufacturers are responding to the refrigerant issue. Some are using carbon dioxide, which has a GWP of one. Others are working on split systems where the refrigerant is installed and permanently contained at the factory, just like your refrigerator. Hopefully, technology can provide a better solution. I recently talked with a national lab researcher working on phase-change materials for heat pumps that would make refrigerants obsolete.
Encouraging the Technology While Managing Expectations
Heat pumps work differently than furnaces and gas water heaters. We need to encourage the contractors to set expectations with their customers before installing one, so there will be no surprises.
I have installed all kinds of whacky heating solutions. Combined-hydronic solutions with high-efficiency gas water heaters. Solar thermal hot water systems with gas tankless back-ups. Radiant systems with forced air, baseboard radiators, and underfloor heating in the same house. My company also installed central heat pump systems and ducted and ductless mini-splits. I have dealt with the challenges.
If I learned anything in this industry over the years, it would be that people don't like change. But what they despise is change without prior notification. If you are a contractor installing heat pumps, you will have much more success if you educate your clients on the difference between the legacy technology (gas furnaces, gas water heaters) and the new heat pump. Heat pumps transfer small amounts of heat over a long time. Gas appliances do precisely the opposite. Homes heated with a heat pump are more comfortable overall, but people need to know what to expect. You can't expect to turn on a heat pump and warm up a cold house in minutes.
If you are a policy person, it is your duty to learn the reality of the technologies you regulate. Just putting on a hat that says electrify everything is not the answer. Learn about the full impact of these technologies, both the good and the bad. Don’t forget the skilled labor and training the industry needs to succeed. Consider that everything works better when efficiency is a part of the solution.
Efficiency Needs to be a Part of the Solution
The real goal with energy use in buildings should be to use less energy and then utilize electric options to take advantage of renewable generation.
Perhaps most of all, we must realize there is no free lunch. Electrification is happening, but as with most things in life, there are pluses and minuses. I fully support the transition to an all-electric future, but let's be realistic and set expectations. We need to get this right, and blindly promoting one approach is not the answer. If we expect the masses to transition to clean energy, we must be honest about the overall impacts and then set realistic expectations.
In general, most people don't like change. If we want them to be a part of this energy transition, we must be honest about the pros and cons of the solutions we promote. Set the expectation up front, and the change will be much easier.