by What are Absorption Chillers?
Unlike traditional electric-powered compression chillers, sorption are driven by thermal energy rather than electricity. This makes them more environmentally friendly as they reduce the need for electricity in cooling operations. Sorption use absorption refrigeration technology which involves a chemical solution and two heat exchangers. During the operation, thermal energy is used to separate and recombine the constituents of a working pair of fluids such as water/lithium bromide. This allows heat to be upgraded into cooling capacity.
How do Absorption Chillers Work?
In an Absorption Chiller, a low-pressure refrigerant like water vapor is absorbed into a concentrated liquid solution such as water/lithium bromide. This solution is heated by the external heat source to raise its temperature and vapor pressure. The refrigerant vapor separates from the solution and moves to a condenser where it condenses into a liquid. This warm liquid refrigerant then flows through an expansion device where its pressure and temperature drop. It next enters an evaporator and absorbs heat from the chilled water or space that needs cooling, causing the refrigerant to vaporize. The low-pressure refrigerant vapor is then absorbed back into the incoming strong solution, releasing heat and completing the thermodynamic absorption cycle. The diluted solution is regenerated for reuse by removing the refrigerant vapor using heat and pressure.
Types of Sorption
There are generally two main types of sorption – single effect and double effect. Single effect sorption are the most basic and commonly used type. They utilize one generator and one absorber/condenser. Double effect sorption have a higher coefficient of performance (COP) as they incorporate two stages of vaporization and condensation allowing more useful cooling from each unit of heat input. They make use of two absorbers/condensers and two generators to covert heat energy more efficiently into cooling capacity. Other variants include triple effect chillers which provide an even higher COP.
What Heat Sources Can be Used?
Sorption are very flexible in terms of heat sources that can be utilized for operation. Common heat sources include natural gas, diesel, propane, biogas, biofuels, solar thermal collectors, waste heat from power plants, engine generators, and industrial processes. Natural gas is the most widely used fuel currently due to its ready availability and relatively low cost. Waste heat streams that would otherwise be lost can effectively power sorption, providing “free” cooling. Solar thermal systems paired with sorption also prove beneficial for green cooling applications.
Benefits Over Compression Chillers
Compared to electrically-powered vapor compression chillers, sorption offer various economic and environmental benefits. Since they are driven by heat rather than electricity, sorption can help reduce peak electricity demand, lower energy bills significantly and lessen CO2 emissions from fossil fuel power plants. They allow utilizing cheaper off-peak utility rates or on-site waste heat streams that would otherwise go to waste. This makes them especially cost-effective for large installations involving district heating/cooling. Their simple design with few moving parts also translates to reduced maintenance needs. Absorption cooling lends itself well to utilizing renewable energy sources like solar and biogas/biofuels as heat inputs.
Applications
Common applications of sorption include:
– Large commercial buildings and campuses for air conditioning and process cooling loads.
– District cooling/heating schemes utilizing waste heat from industrial plants.
– Hospitals, hotels and other facilities with round-the-clock cooling needs leveraging cogeneration.
– Manufacturing plants for machine cooling and thermal process requirements.
– Developments powered via solar thermal/biogas based microgrids.
– Large data centers and server farms utilizing exhaust heat from servers for cooling.
– Hybrid solar cooling systems optimizing use of solar thermal collectors.
Improving Efficiency and Cost Competitiveness
Research efforts are ongoing to boost the COP and reduce the cost premium of sorption compared to electric chillers. New working pairs, advanced designs, use of lower grade waste heat are some areas of focus. Manufacturers are coming up with optimized chillers integrating inverter technology, modular designs and improved heat and mass transfer surfaces. Use of new refrigerants is driving down unit sizes and costs. Wider application of high efficiency double/triple effect chillers would significantly curb emissions globally. Government incentives and renewable energy policies incentivizing waste heat recovery would make solar/waste-powered sorption even more competitive. Growing district cooling markets also promise to aid absorption technology adoption.
Sorption powered by low-grade heat present an attractive sustainable cooling solution compared to electric chillers. While upfront costs may be higher currently, their lower operating costs and environmental benefits make for a compelling business case especially in large buildings harnessing waste heat streams. Absorption cooling technology is expected to play a bigger role globally in achieving energy efficiency and emissions reduction targets set by nations. With continued advancements, it has excellent long term prospects.
*Note:
1.Source: Coherent Market Insights, Public sources, Desk research
2.We have leveraged AI tools to mine information and compile it
Ravina Pandya
Ravina Pandya,Content Writer, has a strong foothold in the market research industry. She specializes in writing well-researched articles from different industries, including food and beverages, information and technology, healthcare, chemical and materials, etc. LinkedIn
