Breaking the heat wave cycle with heat pump air conditioning

In fact, less than 10% of households in Europe have air conditioning. Keeping the blinds shut during the day, opening the windows during the night and relying on fans and chilled drinks are most Europeans’ method of surviving the summer heat. Air conditioners, on the other hand, are often considered to be loud, expensive, environmentally harmful and lead to colds. Thus, there has never been a high demand for ACs in Europe. 

But that is about to change. 

As this graph shows, the demand for air conditioners in Europe has risen significantly in the last few years. 

Why? The summers are becoming increasingly hotter, meaning that keeping the blinds shut will no longer do the job.

Why do we need to cool our homes?

Global warming presents us with a major challenge: it is leading to heat waves that make extreme heat the new norm. Summer 2022 was the hottest recorded summer in the history of Europe, topping the record breaking summer of 2021. 

A major reason for Europe's extreme rise in temperatures is the Atlantic ocean heatwave, which describes the warming of the sea surface temperature which then leads to an atmospheric circulation pattern that warms the air mass above the sea surface. This year the surface water reached a record temperature of 23.1degrees celsius (ºC) – 1.1ºC hotter than the average surface temperature of the past 40 years.

The warming of the Atlantic ocean surface water is influenced by several factors. One of them is climate change. So if we cannot mitigate global warming, we risk further heat waves in the South of Europe due to heated surface water. 

Effects of extreme heat

Health effects

Failing to cool our homes and interiors to adapt to rising temperatures or extreme heat can have serious health consequences. Heat stress, for example, is caused by the exposure to extreme heat and can increase the risk of injuries, heart strokes, heat exhaustion or heat cramps. The Barcelona Institute for Global Health found that there were almost 62,000 heat-attributable deaths in Europe between May and September 2022. The most were in Italy, followed by Spain and Germany. This shows that we urgently need to prevent heat waves from becoming the norm, while also finding more eco-friendly ways of heating buildings. 

Productivity effects

Loughborough University’s project ‘HEAT-SHIELD’, which focuses on the negative effects of working under increased heat, found that productivity can decrease by 76% if the temperature of the work environment is around 40°C. If the temperature reaches 35°C, productivity already drops by 35%. Both are temperatures often reached in the South of Europe.

What are the options?👀

Now that we know about the serious consequences of overheating, ‘lüften’, a beloved German term for ventilating, may no longer suffice. But there are several other ways to ensure that indoors are kept cool. Let’s take a look at a few more options: 

‍Air Conditioning

One of the most popular methods of keeping an indoor space cool is with air conditioning. While considered a luxury in Europe, nearly 90% of American households have ACs installed. The frontrunners in Europe are Russia, Italy and Spain with a demand of over 1 million units. 

An air conditioner consists of three parts. A compressor, a condenser and an evaporator. Briefly explained, a liquid refrigerant inside the evaporator is converted to gas. Under the pressure, the refrigerated gas is then condensed into a liquid that absorbs an indoor space's heat. The heated air is then blown away from the condenser coils. But to do this, air conditioners need a lot of energy, as does their manufacturering and transport. On top of this, air conditioners release harmful refrigerants that contribute significantly to global warming. In total, 1.95 million tons of carbon dioxide are released annually due to air conditioning. This constitutes 3.94 percent of global greenhouse gas emissions. Solely emitted by air conditioning. 

‍Evaporative cooling systems

The energy crisis caused demand for evaporative cooling systems to surge. In Europe, the revenue for these cooling systems is expected to grow to almost 2,300 million USD by 2028. An evaporative cooler, also known as swamp cooler, provides a steady stream of fresh air into the house. When operating, the windows are partially opened in order to draw out the warm air and replace it with cool air. These cooling systems have lower upfront costs than central air conditioning and use just one quarter of the energy. An evaporative cooling system has an increased energy efficiency as they only use about 10% of the electricity that an air conditioning unit would require. However, they require frequent maintenance because salt and mineral deposits can build up in areas with hard water. In addition, they are only suitable for areas with low humidity.

‍Heat pumps heating and cooling

Yes, you read that correctly! Heat pumps can not only be used for heating buildings during winter, they can also be used to cool in the summer. A heat pump is an energy efficient device that transfers thermal energy by moving heat from a warmer space to a cooler space and vice versa. These systems consist of three components: an evaporator (outdoor unit), a condenser (indoor unit) and the refrigerant. For cooling, the process can be divided into an active and passive part. Active cooling utilizes the compressor and a reversible refrigeration cycle, which is possible with any kind of heat pump.  Passive cooling is possible with both brine-to-water heat pumps and water-to-water heat pumps. This principle uses the temperature difference between the ground and the interior of a house. Circulating heating water absorbs the heat and transfers it to the ground – the refrigeration cycle is in this case not activated. Since there is no cold air current at any time, this type of indoor air cooling requires little additional energy. However, the performance of passive cooling is far below that of active cooling. While this process mirrors how an air conditioning system works, in environmental terms, heat pumps perform far more efficiently. 

The following graph shows that cooling was the biggest driver of electricity demand globally in 2022. While the aspect of ‘more cooling’ contributes to increased demand up to +14 TW/h, heat pumps together with EVs only contribute +8 TW/h.

Air conditioners vs Heat pumps

The most common options for cooling today are air conditioning and heat pumps. While air conditioning might be the most known and widely used option, it is not exactly environmentally friendly. 

As previously mentioned, an air conditioning system  consumes a lot of electricity to function. The recent heatwaves that swept over Europe – especially in the south where temperatures reached 47°C – caused demand for air conditioning to rise. And so has electricity demand. In Milan, the demand surged by 30% in the second week of July, correlating to a heatwave. This led to a peak electricity load of more than 59 GW – in comparison, July 2022 reached a peak of under 52 GW. The intensified use of electricity led to a series of power outages across Italy, as everyone simultaneously plugged in their air conditioning to bear the high temperatures of the afternoon and early evening. This means that the  power grid is often overwhelmed during the summer months. 

Heat pumps’ ability to cool often goes under the radar. While the upfront costs are higher, heat pumps provide a more cost efficient way to heat and cool your home. All-year-round temperature control requires at least one air conditioning unit and a conventional heating system, which combusts gas, wood or oil and is therefore higher in emissions. A heat pump, however, can be across the entire year (depending on the type) and is not reliant on gas. Moreover a  typical household heat pump has a coefficient of performance (COP) of around 4, meaning the energy output surpasses the electrical energy used to power it by a factor of four. For comparison, a conventional air conditioner has a COP of 2.3 to 3.5. 

In addition, propane heat pumps that work with natural and environmentally-friendly propane gas as a refrigerant are now available on the market. This makes it possible to operate a heat pump entirely with green electricity and thus significantly reduce the climate-damaging emissions of heating at home. If a heat pump is coupled with a photovoltaic system and battery , this improves its ecological footprint, keeps running costs to a minimum and alleviates stress on the grid on hot (or cold) days.

Challenges

The switch from air conditioning units to heat pumps poses a few challenges. Regulations define minimum efficiency standards for new cooling units, however, enforcing compliance can be challenging. While many subsidies and incentives exist, the upfront costs of installing heat pumps are still an obstacle, as this means the entire heating system must be remodeled. And the current pace of installation is lagging behind demand due to a lack of skilled workers and technical expertise. The lack of consumer awareness is another significant obstacle to the widespread use of heat pumps, both as cooling and heating devices. To optimize their potential, a more comprehensive approach is needed, integrating cooling strategies into holistic solutions that balance energy consumption and prevent strain on grids during peak usage. Overcoming these challenges requires an effort between policymakers, the industry and the public to drive the further adoption of heat pumps and pave the way for a sustainable cooling future.

Future outlook

The future outlook of using heat pumps as a cooling device is promising, yet challenges remain. An improved regulatory framework that outlines the minimum efficiency for cooling units and greater subsidies for heat pump utilization in buildings and homes pave the way for their widespread adoption. Then in combination with PV and a holistic energy management system, their full potential as a cooling unit can be unleashed. Then a local clean power supply can be maximized, energy consumption and costs minimized and thermal comfort always guaranteed. 

This way we can cool our homes even in times of high temperatures without fear of  triggering the next heat wave.