Whats the difference between conventional central air conditioners/heaters and heat pumps? And what makes them so much more energy efficient?
In a nutshell, these units move heat, while conventional systems generate heat. They manipulate the environment rather than physically changing it, using home energy utilities (electricity and/or gas).
In the heating mode, they can use up to 40% less energy! And who can't live with that?
The Anatomy of a Heat Pump
These pumps use a refrigeration system consisting of a compressor (advanced ones are scroll compressors), one copper tube coil outdoors and one indoors, both using aluminum fins to help in heat transfer (like a heat sink).
These typical units are called split systems because of this indoor/outdoor coil configuration. They use a central fan to circulate the air.
When in the heating mode, the refrigerant in the outside coil absorbs available heat which causes it to evaporate into a gas state. Then, the indoor coil does just the opposite, releasing the heat, and changing the refrigerant back to liquid.
As stated above, pumps are best for moderate climes. When the mercury drops below 40 degrees, electric resistance coils must kick in to help (think of a bread toaster), decreasing efficiency.
Advances in Energy Efficiency.
Developments over the past 30 years in air-source heat pumps have delivered 1.5 to 2 times more in energy savings. A few of these tweaked units are the reverse cycle chiller, the cold climate heat pump, and the all-climate heat pump.
What is a Reverse Cycle Chiller (RCC)?
Best for homes that use electricity rather than gas, these units allow homeowners the flexibility to choose between air distribution systems. Want a radiant floor system? No problem. How about a forced air system pumped into multiple zones? Ditto.
A large, insulated water tank is integral to the RCC. The pump cools or heats the water, depending on the season. In the winter, coils can deliver hot water to a radiant floor system.
Some employ a Refrigeration Heat Reclaimer (RHR). It operates in a similar fashion to a desuperheater coil.
What is a Cold Climate Heat Pump?
Because it uses a back-up booster compressor, this unit can operate efficiently down to 15 degrees Fahrenheit (-9.44 degrees Celsius). Additionally, it uses a heat plate exchanger (economizer), if included, to bring efficient operation to conditions below 0 degrees (-17.77 Celsius).
Preliminary studies show an impressive 60% improvement over standard air-source pumps! The downside? They're not yet available to the general public on a large scale. Look for that to change.
What is the All-Climate Heat Pump?
The interesting thing about this variation is that it is specifically targeted to very cold climates, rather than a mix of warm/cool environments. This really opens up the market for consumers in the upper reaches of both North America and Europe.
Its downside? The initial cost of the unit. But if the savings predicted by Wenatchee Valley College in Washington, (up to 60%!), prove comparable to residential savings, this unit will pay for itself in short order.