Compression Chillers vs. Absorption Chillers—Key Differences, Efficiency, and Applications

Industrial chillers are key equipment for achieving dynamic temperature control and rapid cooling. Chillers are generally classified into compression chillers and absorption chillers, based on the method used to drive the refrigerant cycle.

Compression chillers are the most common type. Scroll chillers, screw chillers, and centrifugal chillers are all common types of compression chillers because they rely on a compressor to compress the refrigerant to achieve refrigeration. Absorption chillers, on the other hand, use thermal energy to drive the refrigerant and absorbent to circulate refrigeration.

What are the specific differences between the two?

Aspect	Compression Chillers	Absorption Chillers
Drive	Electric motor + compressor	Heat energy, no compressor
Core Parts	Compressor, condenser, expansion valve, evaporator	Evaporator, absorber, pump, generator, condenser
Efficiency (COP)	~4.0, high efficiency	0.6–1.2, lower
Response	Fast, flexible load control	Slow, high thermal inertia
Capacity Range	Small to large (labs → industry)	Large-scale only
Energy Source	Electricity	Steam, hot water, waste heat
Applications	HVAC, semiconductor, pharma, labs	Central cooling, power, steel, chemical
Cost	Lower purchase & maintenance	Higher cost & water use

Drive Method and Refrigeration Principle Differences Between Compression and Absorption Chillers

Compression chillers rely on a mechanical compressor. When powered on, a motor drives the compressor’s rotor (for scroll or screw compressors) or impeller (for centrifugal compressors). The compressor draws in refrigerant gas, compressing it and raising both its temperature and pressure.

The refrigerant is then discharged and enters the condenser, where it exchanges heat with cooling water or air, condensing into a liquid. The refrigerant then passes through an expansion valve to reduce pressure and temperature before entering the evaporator, absorbing the heat from the coolant.

In contrast, absorption chillers operate without a compressor, using thermal energy to circulate the refrigerant. Take a typical LiBr-H2O system as an example. After evaporating in the evaporator, the refrigerant forms low-pressure vapor.

However, unlike the refrigeration cycle of a compression chiller, it does not enter the compressor directly. Instead, it is absorbed by the LiBr-H2O solution. The absorbent takes in the refrigerant vapor, generating a low-pressure area that is pumped to the generator.

Within the generator, heating with steam, hot water, or gas causes the refrigerant to separate from the solution. Because the vapor is released through heating, the refrigerant pressure is already elevated, eliminating the need for compression by a compressor and allowing it to be directly fed to the condenser for condensation. Absorption chillers also do not require expansion valve throttling, so the cooled refrigerant enters the evaporator for evaporation.

Compression Chillers vs Absorption Chillers Key Differences Efficiency and Applications - absorption chillers (Image 1)

Compression Chillers vs Absorption Chillers Key Differences Efficiency and Applications - chiller comparison (Image 2)

Structural Differences Between Compression and Absorption Chillers

Comparing the refrigeration principles of the two, you’ll find that their internal structures are different.

The core components of the compression chiller’s refrigeration cycle are the compressor, condenser, expansion valve, and evaporator. Since a compressor extracts and compresses the refrigerant, it’s essential in this system. The expansion valve plays a crucial role in lowering the pressure of the high-pressure liquid refrigerant.

However, an absorption chiller can create negative pressure by absorbing vapor in the absorbent, or it can increase pressure by releasing vapor through heated solution. In other words, the pressure change in the system is controlled by the absorbent and the pump, eliminating the need for a compressor and expansion valve. As a result, the main components include the evaporator, absorber, solution pump, generator, and condenser.

Compression Chillers vs Absorption Chillers Key Differences Efficiency and Applications - compression chillers (Image 3)

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Performance Differences Between Compression Chillers and Absorption Chillers

The performance differences between compression chillers and absorption chillers are generally reflected in cooling efficiency, response speed, and cooling capacity.

Compression chillers have higher energy conversion efficiency. While system type, configuration, and operating conditions vary, most units can maintain a COP of around 4.0. In particular, units equipped with variable frequency drives (VFDs) can maintain a high COP even at low loads.

Although many companies choose to use waste heat to power absorption chillers to save electricity, the overall COP of absorption chillers is still much lower, typically between 0.6 and 1.2.

Are you curious why most semiconductor fabs choose compression chillers over absorption chillers? This is because absorption systems have greater thermal inertia and cannot adjust cooling capacity in a timely manner according to load.

When loads fluctuate frequently, compression chillers, which can adjust cooling capacity in a timely manner by adjusting compressor speed and expansion valve opening, offer advantages.

Furthermore, screw, scroll, and centrifugal chillers are suited to different heat loads, allowing for a suitable compression chiller to meet specific needs, from small laboratories to large industrial applications. Absorption chillers are commonly used in large-scale centralized cooling systems ranging from several hundred to several thousand kilowatts.

Application Differences Between Compression and Absorption Chillers

Because different types of compression chillers cover a wide range of cooling capacities, they have a wide range of applications. Small scroll chillers are commonly found in laboratories and medical institutions. Large screw chillers are very common in building HVAC systems and in industries such as the chemical and pharmaceutical industries.

In short, whether you need cooling equipment from a few kilowatts to several hundred kilowatts, you can find a suitable model among compression chillers.

Absorption chillers have a relatively low electricity dependency, making them suitable for large-scale projects that prioritize energy savings, such as centralized cooling systems or those in the steel, chemical, and power industries seeking to utilize waste heat from factories.

Compression Chillers vs Absorption Chillers Key Differences Efficiency and Applications - industrial cooling systems (Image 4)

Cost Differences Between Compression and Absorption Chillers

Absorption chillers generally have higher purchase costs than compression chillers due to their more complex design and additional internal components. Consequently, they require more maintenance time and costs. Regarding operating costs, the absorber in an absorption chiller requires water, resulting in higher water bills over time.

Conclusion

LNEYA is a Chinese chiller manufacturer specializing in the design and production of compression chillers. We offer scroll chillers and screw chillers in a variety of performance levels, allowing us to tailor the optimal solution for your unique application.

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