## Unlocking the Complexity of Heat Pump Efficiency: Exploring COP and COPnet for Informed Insights and Decisions

Understanding COP (Coefficient of Performance)

Today, we're delving into a fascinating and somewhat intricate subject, particularly concerning heat pumps: the Coefficient of Performance, or COP. But before we dive into the topic, I'd like to emphasize that we'll present some key facts. Ultimately, I'll leave you to draw your own conclusions. Let's begin by exploring what experts have outlined about COP.

The Coefficient of Performance Defined

The Coefficient of Performance (COP) of a heat pump is defined as the ratio of useful heating or cooling provided to the work required. This involves the useful heat drawn out as cooling or heat (Q) by the system and the work demanded (W) by the system. However, here's where things get tricky: many manufacturers of traditional heat pumps only consider the consumption done by the compressor, neglecting the energy consumption of the fans. This approach inaccurately suggests that the heat pump extracts energy from the ambient air via natural convection, which isn't the case. We must account for the energy needed to operate the mechanical fans that extract energy from the ambient air. Hence, we propose that the genuine COP should be the ratio of useful energy from the system divided not only by the consumption from the compressors but also by the consumption from the fans.

Considerations for Accurate COP Calculation

1. Introducing COPnet: A Comprehensive Efficiency Metric

Now, let's touch upon something we introduced some time ago: the COPnet or COP of the system. Why did we do this? Well, in our hybrid integrated system, we incorporate two sources of heating or cooling: heat recovery and the heat pump. Correspondingly, we have two energy consumers: the compressors and the fans. To provide a comprehensive assessment, we devised the COPnet or system efficiency coefficient, which calculates the pure efficiency of the unit by considering all sources of heating and cooling divided by all energy consumers. We firmly believe that this presents a more accurate representation of COP.

#### 2.Calculating COPnet

Where:

Qplate/rotary heat exchanger - recovered heat in the rotary heat exchanger (kW)

Qheat pump - heating capacity of the condenser of the heat pump (kW)

Nfans - energy consumption of both (supply and exhaust) fans (kW)

Ncompressors - energy consumption of the compressors (kW)

3.Comparing Hybrid Systems with Traditional Heat Pumps

Additionally, let's compare the COP of our hybrid integrated system - max.e, with that of traditional heat pumps. What sets them apart? It's crucial to remember that traditional heat pumps use ambient air to extract heat, whereas our system draws air directly from the room through our evaporator to extract heat. Consequently, our refrigerant circuit's COP will consistently surpass that of traditional systems. Furthermore, when discussing COPnet, don't be surprised to encounter figures exceeding 10 or even 12. The greater the temperature difference between ambient and room temperatures, the more efficient the heat recovery system becomes, leading to higher useful capacity and elevated coefficients. So, consider these insights and formulate your own conclusions.

4.Example Scenario

A conventional air-cooled heat pump uses ambient air for the evaporation process, and during the winter, this air can reach temperatures of -10°C, -15°C, or even -20°C. Extracting heat from the ambient air is an inefficient process.

In comparison, our hybrids extract air from within the room. Under normal conditions, this air ranges in temperatures from 20÷24°C. Firstly, 65÷80% of the heat is recovered in the rotary/plate heat exchanger, and then at a temperature between 1÷6°C, the air enters the evaporator of the heat pump, thus recovering the other 20÷35%. Using this method, we achieve a COPnet of 10 - 12 and avoid frost formation on the evaporator (which commonly occurs in all conventional heat pumps).

In summary, grasping the Coefficient of Performance (COP) and its thorough assessment via COPnet offers valuable insights into the efficiency of heat pump systems. By accounting for all energy consumers and sources of heating and cooling, COPnet presents a more precise depiction, demonstrating the superior efficiency and performance of hybrid integrated systems compared to traditional heat pumps.

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