How Heat Pumps work

Heat pumps are common & efficient

Electric heat pumps are the essential part of standard household equipment:

  • In fridges, a heat pump moves heat from inside the fridge into your kitchen.
  • In reverse cycle air-conditioners, the heat pump cools a room by moving heat from the room to outside the house. When you reverse the cycle, the heat pump heats the room by transferring heat from outside your home to inside the room.

Heat pumps use electricity to run a fan and compressor – and can be amazingly efficient. A high-performance residential heat pump can use one unit of electrical energy to move six times as much heat energy into your house, an efficiency of 600%.

By comparison:

  • Electrical heaters have an efficiency of 100% as they can convert all the electrical energy into heat, and
  • Gas heaters have an efficiency of between 50% and 95%, as some of the heat generated heats the house exterior.

A Heat pump hot water service

One use of a heat pump is to heat your hot water. You can run the heat pump when the sun is up and use electricity from photovoltaic solar panels to power the heat pump. After installing the panels and heat pump, you heat your water for free, generating no emissions. 

The heat pump heats your hot water by moving heat from the air outside your house into your hot water tank. It uses a refrigerant, a liquid that boils at a low temperature like minus 26 C and works in a cycle as follows.

(The numbered points in the following text further explain the below diagram.)

  1. In the heat pump evaporator, the refrigerant is intially a liquid at low pressure.
  2. Boiling the refrigerant: An electric fan warms the refrigerant by blowing air from outside the house over a heat exchanger, which transfers the heat to the refrigerant. While the air temperature is above minus 26 C, it will heat and boil the liquid refrigerant. The refrigerant evaporates like water becomes steam in a pot on the stove. The cold air of a freezing day will still boil the refrigerant because boiling point of the refrigerant is so low. However, on a cold day, the system is less efficient as the fan must work longer to boil the refrigerant.
  3. In the compressor, the refrigerant is initially a cool gas at low pressure.
  4. Compressing the refrigerant gas: A valve closes, shutting the refrigerant gas in the compressor where an electric pump compresses the gas. As the pressure builds, the gas gets hotter, just as a bicycle pump gets hot as you pump up the tyres. The gas can heat to 95 C.
  5. In the condensor, the refrigerant gas is initially hot and at high pressure.
  6. Producing hot water & cooling the refrigerant: The hot, pressurised gas then passes its heat, via another heat exchanger, to where you want it, to the water in your hot water tank. In doing this, the refrigerant gas cools and condenses. The refrigerant is under pressue so the condensing / boiling point is higher than it was at room pressure in the evaporator.
  7. Pressurised Liquid: Now, this refrigerant is a warm liquid, still under high presssure.
  8. Dropping the pressure: The expansion valve opens and the pressure drops, causing the liquid refrigerant to vapourise. It mixes with the liquid refrigerant at room pressure in the evapourator.
  9. Liquid refrigerant at room pressure: The refrigerant is back where it started in the evaporator, ready to repeat the heat harvesting cycle shown below.

The Heat pump cycle

Refrigerant liquid under low pressure.
(1) & (9)
Evaporator: Fan blown air boils the refrigerant (2)
Expansion valve: Release the pressure (8)Refrigerant gas, cool & at low-pressure (3)
Refrigerant warm liquid at high pressure (7)Compressor: Pump pressurises the refrigerant gas (4)
Condenser: Producing hot water cools the refrigerant (6) Refrigerant gas at high temperature & high-pressure (5)

Further information

Updated: 29 Jan 2022

Australia’s strong sun

Australia could become a renewable energy superpower.  One factor behind this is that Australia gets stronger sun than most developed countries.

Two world maps superimposed

Here is a fascinating map that demonstrates this.

It is two maps superimposed on one another. The first is a normal map of the world.  The second map shows, for each point on the first map, where you would be if you drilled straight down through the centre of the Earth to the other side.

The closer a place is to the equator: (1) the more the sun is directly overhead, (2) the more sunshine it gets, (3) the more electricity is generated from each solar panel, and (4) the cheaper it is for that place to generate electricity from the sun.  This is ignoring other factors like how cloudy a place is.

From this map you can see that:

  • Australia is closer to the equator than the developed countries in northern Europe, northern Asia and northern America.
  • Northern Greenland, Canada, Alaska and Russia are as far from the equator as northern Antarctica
  • Melbourne is as far from the equator as southern Spain, so most of Australia gets stronger sun than Spain and most of Europe.
  • Northern Australia is as far from the equator as the border between the Sudan and Egypt.
  • The southern border of the USA is about the same distance from the equator as Port Macquarie (halfway between Sydney and Brisbane). So northern Australia gets more sun than the south of the USA.

Manchester in England is as far north as Macquarie Island is south

Look at this yet another way. Australia gets far stronger sun than most of Europe because we are closer to the equator.

People often think of Macquarie Island as being in the Antarctic as it lies far south of New Zealand at latitude 55 degrees south. Well, Manchester in England lies at latitude 54 degrees north, so Manchester is as far north as Macquarie Island is south – and both experience a similar level of sun exposure.

Northern America and northern Europe get very weak sun compared to most of Australia. Europe would be very cold without the Gulf Stream.

Australia has quality solar resources

So, considering only the factor of sun strength (closeness to the equator), Australia has better solar resources than most developed countries – and we have other advantages too, which mean that Australia could become a renewable energy superpower.

Updated: 21 June 2024

Warm is Not Cool: A Musical Protest


Musical Protests Against Inaction on Global Warming: 2016 & 2019.


Stephen Taberner organised this protest.

(As you might already be able to tell, on this page I have used lots of “dirty funky” words from Stephen’s event promotion.)

Our long-awaited first public outing was on Sunday 19 June 2016.

A marvellous experiment in public protest, inspired by the New Orleans brass bands, the English football crowds, and the Brazilian samba.  We brought our delicious hybrid to the streets.

It was highly enjoyable, highly effective and downright dead, dirty funky. The three contingents of voice, horns and drums intersected in every cool way possible as we protested the woeful lack of attention in these election weeks to the elephant in the policy room: CLIMATE CHANGE.

To get people started, we rehearsed in public on the steps outside the Victorian State Library.  Here we are, learning and brushing up on our songs, chants, and grooves.

Video 1: (1) watcha gonna do (2) Warm is not cool

After the warm-up,  we strutted our stuff at the old shot tower in the Melbourne Central Arcade.  (Sorry, you may need to be on Facebook to see the next two links.)

Video 2: (1) warm is not cool (2) watcha gonna do

Video 3: (1) warm is not cool (No longer available: 9/8/2023)

Later we were in the Melbourne City Square

Video 4: (1) warm is not cool (2) Whatcha gonna do

Then we did our thing in Federation Square.
And then called it a day.

Warm is not Cool: The Sequel: 26 June 2016:

Video 5: In Melbourne Central again: (1) Warm is Not Cool (2) Whatcha Gonna Do.

“Vote the Bastards Out” 2019

We sang this in the streets prior to the 2019 election – to no avail.

Vote the bastards out: Spooky Men’s Chorale

The songs and chants: Lyrics and tunes

Not too many words.  Lots of repetition, harmony and jive.

(The lyrics and tunes are no longer where they were on the web. 9/8/2023)

****** Song: Warm is not cool

You can hear this on the sound cloud links and videos

Warm’s not cool

Warm is not cool
Warm is not
Warm is not
Is not

Yo de aye
Warm is not cool

Did you know that’s the case so
We got to fix up this place

We don’t want to mess up the future

***** Song :  A message to you Turnbull

You can hear this on the sound cloud links and videos

Stop your messing around
Better think of our future
Time to straighten right out
This problem in town

Turnbull, a message to you Turnbull
, a message to you Turnbull
, a message to you Turnbull
, a message to you Turnbull

22 percent of the reef is gone
Turn the coal off.  Turn the solar on

***** Song 3: Malcolm

You can hear this on the sound cloud links and videos.
Each part: bass, mid and top is separate on sound cloud.

Malcolm Turnbull’s got a very nice face
So let’s find him a lovely job in another place

***** Whatcha gonna do:  Call and Response Chant

Whatcha gonna do                  What
When the world gets hot      What
Whatcha going to do               Whatcha going to do
What                                                  When the world gets hot
What                                                  Whatcha going to do

Then Repeat

Try this chant while listening to the above video of us outside the State Library.

***** Chant: Coal Don’t Dig it

Coal don’t dig it
Leave it in the ground
You’ve gotta get with it


Stephen Taberner taught us these songs and chants

He knows how to work a group!
Here he is leading the Spooky Men’s Choir at a folk festival in Shrewsbury, England.  Good song.  You might even laugh.

Another top song

We Are Not a Men’s Group – The Spooky Men’s Chorale

Andrew Gunner

A solar-powered winery on Sikinos

A remote winery on the island of Sikinos in Greece has a spectacular view and more.  It has solar panels on the roof and battery storage, along with the expected large stainless steel wine vats.  Across the world, it’s happening more, away from the grid, it’s economical to be self-sufficient.

The winery is 2.5 kilometres away from the main village, perched high over its terraced vineyard with views of steep island peaks. There’s a tiny church on one peak and, out of view in a valley below, there’s an ancient Roman temple that became a church.  The wine-dark seas of Odysseus are spread in front of you, with islands dotting the broad sweeping horizon.  You can walk the old footpaths of Sikinos, and most of the ancient agricultural terraces are crumbling, but at the winery, the terraces are in repair, and the vines thrive on the moisture from the morning mists. 

Manalis Winery Sikinos

Temperature, CO2 and Sea Levels move together

Sea levels, Carbon dioxide concentrations, and Global temperatures have moved together over the last 450,000 years.


The graphs show the movement over the last 420,000 years of:

  • Carbon dioxide concentrations in the air (the green line),
  • Global temperatures (the red line), and
  • Sea levels (the blue line).

The carbon dioxide concentrations have fluctuated between about 180 and 280 parts per million (ppm) over this period of 420,000 years, but in the last 50 years, it has rocketed to above 410 ppm. (See the red circle on the green carbon dioxide graph.)  

The sea levels and temperatures have moved with carbon dioxide levels in the past.  This suggests that the recent increase in carbon dioxide will lead to large rises in sea level and temperature.

The graph shows five periods of high temperatures. We are living in one of those warm periods. During the previous warm period, about 120,000 years ago, the temperature was a few degrees warmer than at present, and the sea level rose about 8 meters higher than the present – and carbon dioxide levels were a lot lower than they are now.

The work of Hansen and Sato provided the basis of this graph

(John Englander: Oceanographer)

Glaciers in retreat:

Glaciers around the world are in retreat. Out of 250 alpine glaciers studied, the Taku Glacier in Alaska was the only glacier not retreating until, in 2019, it too began retreating. At 1,500 metres thick, it’s one of the world’s thickest mountain glaciers, now retreating by up to 390 billion tons of snow and ice a year.

(This is a big deal. Mighty glacier finally succumbs to climate change: The Age: 8 Nov 2019)

The glacier altitude feedback cycle

This feedback occurs because the average temperature at the top of a mountain is lower than at sea level – and this is relevant because we have some thick ice sheets, for example:

  • up to 4,900 meters deep in Antarctica,
  • up to 3,000 metres in Greenland, &
  • up to 1,500 meters for mountain glaciers.
More glacial surface meltingA drop in the altitude of the glacier surface
*A rise in average temperature at the glacier surface

When the “glacier altitude feedback” is dominant:

  • more glacial surface melting causes
  • the altitude of the glacial surface to drop, causing
  • higher temperatures at the glacial surface, which closes the cycle by causing
  • more glacial surface melting.

This feedback cycle indirectly increases global temperatures. As the “glacier altitude feedback cycle” decreases the area of reflective glacial ice, the area will absorb more heat from the sun. So, another feedback, the “ice reflection feedback cycle“, will increase global temperatures.

The Extreme Ice Survey

The Extreme Ice Survey collects visual evidence of the impact of global warming on our planet, like time-lapse photos of the contraction of the glaciers.  Outside of the Antarctic, 95% of the world’s glaciers are retreating. See:

  • the film “Chasing Ice”, produced in cooperation with National Geographic. It won an Emmy award as an outstanding nature program, or
  • the TED talk by James Balog in July 2009.

Related pages

Updated 28 March 2022