Alternative Energy



Heat and Geothermal Pumps

The Ultimate Heat Pump
Nesjavellir Geothermal Power Plant in Iceland
Photo credit: Gretar Ívarsson


Heat Pumps


A heat pump is an air conditioner with a valve that

lets it switch between air conditioning and heating.

When the valve is switched one way, the heat pump

acts like an air conditioner,the other way it reverses

the flow of Freon and acts like a heater.

Photo credit: USDOE

Remember that Freon can and does pick up

heat all the way down to 360 degrees below zero.

The hotter the weather, the more heat that Freon picks

up from the air and the closer the temperature gets to

360 degrees below zero, the less heat that it picks up.

Freon can still pick up some heat at 359 degrees below zero.


Remembering this can help in understanding why

we can save money with Alternative Energy.


The heat pumps being used today run on 220 volts, but

if we use wind and solar power to run the compressor,

fan and relay the electric company will only need to

be used as a backup system.

Heat pumps can be extremely efficient in their use of energy.

But one problem with most heat pumps in colder weather

is that the coils on the outside air unit collect ice.

The heat pump has to melt this ice periodically, so it

switches itself back to an air conditioner, then,

an electric coil heater comes on to heat up the coils.

To avoid pumping cold air into the house in air conditioner mode,

the heat pump can light up burners or electric strip heaters

to heat the cold air that the air conditioner is pumping out.

Once the ice is melted, the heat pump switches back

to heating mode and turns off the burners.


Geothermal Heat Pumps


A Geothermal Heat pump works just like the ones that have

been around for years, except because the ground water

is around 55 degrees, not the outside temperature,

the compressor runs for a shorter period of time

and therefore costs less to operate.


The heat exchanging tubes are in the ground, instead of in the air.

In a geothermal system, water-filled tubes buried in the ground

pick up the ground’s heat about 50° to 55° year round

and circulate that water to the heat pump.


You have to use a compressible gas system, or Air conditioner,

when you compress the Freon from a large volume

to a small volume, you also compress

the larger volume’s heat, so by definition,

there’s a lot more heat per unit in the smaller volume,

the surface of what’s holding the compressed gas gets hot too.

Photo credit: USDOE

Now, if you blow air across that hot surface, you can heat your house.

When you blow air across the hot surface, you take the heat out

of the compressed gas, cooling it and the gas turns

into a liquid.


In order to turn it back into a gas, you have to warm it up

take the pressure off and give it a place to expand into.

At this point in the cycle, the fluid is now just about

freezing temperature (32°), so the 50° water

from the ground has plenty of heat to warm

it up, unlike the outside air in colder weather.

Photo credit: USDOE

When you want to cool your house, the system runs in reverse,

heat from the house expands the liquid into a gas and

the warmed water in the ground loops stores its heat

in the earth from warm water temperature,

to the 50 to 55 ground temperature.


Ground source or Geothermal heat pumps have

several advantages over fuel burning furnaces.

They’re environmentally friendly and efficient.

Since the energy to heat your house comes from the sun

and the earth’s core, all you pay for is the electricity

to run the compressor, the blower and the water pump.

It’s common to get 3 to 5 times the energy

out of a heat pump than what you put into it.


Geothermal systems help heat your hot water.

Compressors are not 100% efficient and produce a little

“waste” heat, called “superheat”, since the compressor’s

job in the heat pump is to make gas hot.

Today’s Geothermal systems have a water-filled jacket,

called a “desuperheater” which takes that extra heat

and pumps it into your water heater.

Every time the compressor runs to either heat or

cool your house you’re getting “free” hot water.

Geothermal systems are versatile and quiet and

its really easy to have forced-air heating and cooling,

or radiant in-floor heat, in your basement or garage.



Places to learn more:

Department of Energy

Heat Pumps

Geothermal Education

Geothermal Heat Pumps

Geothermal Technologies Program

Geothermal Heat Pump

Geothermal Heat Pumps

Heat Pumps, How Well Do They Work?

How Air-Source Heat Pumps Work

How the Heat Pump Operates


For further information about any

of these and other energy saving ideas,

please contact me.



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Responding To Inquisitive minds Since August 21, 2008

Last edited November 12, 2022

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