I have never really understood the difference between a heat pump and an A/C myself.
Any expert care to explain it in layman's terms?
Any expert care to explain it in layman's terms?
An air conditioner uses a compressor to convert a refrigerant and sends the compressed fluid through a condenser. The condenser rejects heat from the system into the environment. This is the component of an air conditioner that is found outside. The compressed fluid is then passed through an expansion valve and into an evaporator where it is allowed to expand. Expansion is a process that requires heat. The heat flows into the expanding fluid from the environment inside the home. Air is blown across the evaporator coils to transfer heat energy from the home into the fluid which is then returned outside.
A heat pump is capable of reversing the flow of heat energy. The flow of fluid is reversed from an air-conditioner using something called a reversing valve. The compressor sends compressed fluid into the home where heat is rejected through the evaporator coil. The fluid then flows into the condenser coil and is allowed to expand outside, drawing in heat from the outside environment. The heated fluid is then returned to the compressor and the cycle continues.
In HVAC terminology an Air Conditioner is a one way physical heat pump and a heat pump is a bidirectional physical heat pump. Hopefully that helps clear it up a bit.
If you are able to run this system backwards, you could in theory swap which side is a heat sink (the cold side) and heat source (the hot side). While a traditional A/C cannot do this, heat pumps can electronically switch which side of the system is collecting the heat and which side is releasing it.
This is an improvement over resistive heating (think space heater) because we’re not pumping electricity into some filament that resists current flow and emits off heat due to the resistance. Instead, we are taking heat from inside and moving it out or taking heat from outside and moving it in.
Fun fact, a resistive heating device is a rare case of something being 100% electrically efficient in that all the energy it uses will be turned into heat, whereas heat normally is a byproduct of imperfect conductors, which everything is, and is therefore considered wasted energy in almost all other applications.
My understanding is that you get considerably more heating per watt-hour with a heat pump than with resistive heating, though. I get that it's not creating that heat but moving it, but still that seems like even more efficiency from the perspective of energy consumption per useful heat made available.
OP said electrical efficient so the goal is conversion of electricity to heat and it’s 100% efficient.
Even an electric heater compared to a propane heater is more electrically and energy efficient, but it’s not as storage-efficient (because fossil fuel gases have much higher energy density per volume AND weight than lithium batteries).
A heat pump is more electric bill-efficient.
I am not an engineer and I am only nitpicking to have fun, so don't engage me if it's not fun, but doesn't some of the energy go into degradation of the materials used to build the device?
I said 100% electrical efficiency because from the prongs of the plug, through the conductors in the appliance cord, the rheostat, all electrical connection and contact points, and of course the hearing element itself all will product heat as a consequence of electricity flowing through, and being resisted by, it’s various components.
It was pointed out that this does not mean “energy bill efficient” which is totally correct: this whole thing is a somewhat silly thought experiment to consider what it really means for something to be efficient.
The closest analogy that I know of is in electrochemical processes where some of the energy input is allowed to take different forms. If you put in 85 units of electrical energy, 15 units of waste heat from a different process, and get 90 units worth of product, your process is 90% thermodynamically efficient, but has better than 100% electrical efficiency. In the case of a heat pump, measuring units of heat per Watt-hour is a bit like this in that some of the input energy (for the heat generation) has already been provided by a different process.
There's a process called a "vapor compression cycle" which essentially works by moving energy from a cold area to a hot area (which makes the cold area colder and the hot area hotter).
Air conditioning is when you put the cold side of a vapor compression cycle in a building to keep it cool.
The term "heat pump" most typically refers to a device where the hot side of the vapor compression cycle is put in a building to keep it warm.
However, many heat pumps have an air conditioning mode, where the hot and cold sides of the vapor compression cycle switch places depending on the season. So air conditioner refers only to cooling, while heat pump may refer to heating along or a device which can both heat and cool.
* Heat pumps, when referring to HVAC technology specifically, refer to systems that are essentially the same as A/C units, except they're designed to work in reverse.
* The term "heat pump" when used in Europe, more-often refers to geothermal heat-pumps ( https://en.wikipedia.org/wiki/Ground_source_heat_pump ) which is very different to an A/C-style heat-pump, though achieves similar end-result (livable indoor room air temperature).
As someone who spends a lot of time in the year in both North America and Europe I frequently come across people confusing the two.