Heat pump efficiency: it’s a matter of chemistry!

Heat pumps are, without a doubt, the most efficient heating alternative currently available on the market. However, to maintain efficiency over time, even these types of systems require specific maintenance standards. The maintenance we refer to concerns the entire system and includes both mechanical and chemical elements. Underestimating the chemical reactions occurring inside a heat pump is profoundly damaging in the long term, especially if we consider that these can lead to irreversible failures in terms of efficiency. This article analyses this topic to provide useful information to ensure a heat pump runs efficiently and saves energy.
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Heat pumps are booming, as stated by Assoclima, the Italian Association of Climate Control System Manufacturers. The percentage increases recorded at the end of September 2022 reached +108.2% of volume and +126.9% of value. This trend is in line with the REPowerEU, the European Commission’s plan that, among its several goals, aims to double the number of heat pumps in the next five years. 

The priority, now, is to contain, as far as possible, the soaring energy prices that are getting unbearable for many companies and families, and to rapidly reduce the European dependence on fossil fuels and fast forward the green transition.  

However, it is important to point out that replacing an old natural gas boiler with a latest-generation heat pump is not enough to solve the problem of high energy prices. Although heat pumps are, without a doubt, the most efficient heating systems currently available on the market, this investment must be protected over time with farsighted choices that include planned maintenance. 

But what does heat pump maintenance consist of?  

Heat pumps are not only a bunch of mechanical components but are composed of chemical elements too: the refrigerant gas and the lubricant that, by playing specific roles, contribute to the operation of heat pumps. 

The refrigerant gas carries thermal energy within the system: going through cyclic condensation and evaporation processes, it continuously changes from a liquid to a gaseous state flowing within the pipes and favouring heat exchange and the release of hot (or cold) air into the room.  

The lubricant not only lubricates the moving parts of compressors but also plays a crucial role in eliminating the heat resulting from the compression of the refrigerant gas and so cooling down the internal components, which can reach very high temperatures while the system is running. 

As both are chemical elements, it is natural and physiological that they tend to decay, leading to different harmful reactions that proper and constant maintenance could instead block and prevent. 

What affects heat pump efficiency? Understanding their chemistry  

To name a few causes that affect heat pump efficiency: oil fouling, refrigerant leaks, moisture and acidity, and dirty coils.  

1. Oil fouling 

This is the phenomenon whereby fractions of compressor oil tend to deposit on the internal walls of the evaporator and condenser pipes, reducing heat exchange and, thus, the system’s efficiency.

2. Refrigerant gas leaks

Micro-leaks cause the dispersion of refrigerant gas into the atmosphere, leading the heat pump to consume more energy. These micro-leaks can be caused by welding defects, porosity in the system’s piping, and, as we will analyse better in the next section, corrosion. Whatever the cause, it is essential to act promptly to repair them. Not only will this increase the heat pump efficiency, but it will also protect the environment, preventing refrigerants from spreading into the atmosphere and contributing to the greenhouse effect and ozone layer depletion. 

3. Acidity and Moisture

Moisture flowing inside heat pumps depends on several factors. First, just think of the natural moisture content of the refrigerant gas and lubricant in the system or the residual moisture coming from the installation of the system. In addition, further moisture accumulates over time in operating systems. On the one hand, in fact, the filter drier designed to eliminate it tends to saturate, losing effectiveness; on the other hand, the natural ageing of the oil or, worse, the presence of any leaks tends to form new moisture.

When moisture meets the components resulting from the natural decay of refrigerant gases and lubricants, organic, carbonic, hydrochloric and hydrofluoric acids are produced, leading to the corrosion of rubber and metal parts and to the formation of refrigerant gas leaks. 

4. Dirty evaporator and condenser coils

Evaporator and condenser coils tend to collect dirt: grease, dust, pollen, and leaves, but also smog and saline incrustations, especially when it comes to outdoor units installed on the sea or in particularly polluted areas. Dirt drastically reduces the efficiency of heat pumps as it blocks the heat exchange inside evaporators and condensers. In the case of the latter, dirt blocks the heat released by the refrigerant gas in the transition from a gaseous to a liquid state; in the case of evaporators, instead, it blocks the heat generated by the transition from a liquid to a gaseous state. A dirty heat pump, therefore, consumes more energy as it takes longer to reach the desired temperature.

 

For over 20 years, Errecom has been collaborating with OEMs and studying these problems to solve and prevent them. Considering the importance that heat pumps are increasingly assuming on the market and that the energy demand from air conditioners will triple by 2050, there is no doubt that maintenance is the answer. HVAC technicians must start considering the chemical reactions occurring in heat pumps and prevent them with professional and certified products. Only in this way will it be possible not only to maintain efficiency and cope with soaring energy prices but also to turn the heat pump industry into a more sustainable and greener sector.

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