What Is Air Compressor Heat Recovery?

Heat recovery for air compressors captures waste heat generated during the compression process and repurposes it for useful applications like water heating or hot air for space heating. When air compressors operate, most of the electrical energy consumption is converted into heat energy. A heat recovery system takes this excess heat from the compressor – also known as waste heat – and reuses it, significantly cutting energy costs. This process transforms the compressed air system from being solely an energy consumer into a valuable source of reusable thermal energy, leading to a more sustainable and efficient operation.

A well-designed compressed air system allows companies to recover heat, turning this excess heat into usable energy for heating systems. This reduces reliance on external heating methods such as fuel oil or natural gas, offering financial and environmental benefits. Let us explore how heat recovery technology works in air compressor heat recovery systems.

The Scale of Wasted Energy in Air Compression

Compressing air is an energy-intensive process where efficiency is critical to operational costs. A staggering 94% of the energy used by a compressor is converted into heat. In older or less efficient systems, this means up to 90% of the electrical energy consumed can be lost. Without a heat energy recovery system, this substantial thermal energy is often simply vented into the atmosphere, leading to higher energy bills and increased carbon emissions.

How Does Heat Recovery Work in Air Compressors?

Compressing air produces significant heat – up to 94% of the total energy used is converted into compression heat. Without a recovery system, this energy is wasted. An introduction to air compressor heat recovery shows that it allows businesses to recover waste heat from the compressor’s exhaust heat and reuse it to heat water or warm air, improving overall energy efficiency.

In water-cooled systems, a heat exchanger – such as a PTG heat exchanger – transfers the thermal energy from the oil or cooling circuit to process water, which can be used for boiler feed pre-heating, cleaning, sanitation purposes, or space heating. These recovery systems can heat water to 70 °C or higher, significantly reducing the energy required from gas or electric heaters.

Alternatively, in air-cooled compressors, hot ambient air expelled from the cooling system can be ducted into indoor spaces, helping to heat buildings using hot air heat recovery. This method is especially useful in colder months and can be more efficient when hot air heat recovery is compared to fuel oil-based heating is considered.

Modern compressors further enhance this process. For example, Variable Speed Drive (VSD) technology optimises heat recovery by adjusting the motor speed to match air demand, maximising the potential for energy recovery. New Atlas Copco models can even be fitted with state-of-the-art, built-in Energy-Recovery Systems.

The usable heating energy volume depends on several factors:

• The energy volume of a rotary screw compressor
  
• Whether the compressor is cooled continuously or intermittently
  
• The working air pressure and air temperature
  
• The condition and design of the cooling systems

By installing the right setup, even small compressors can participate in waste heat recovery. Heat recovery can make a measurable difference in an operation’s total energy consumption and forms a key part of any effective industrial energy recovery process.

For detailed figures, it’s best to calculate the usable heating energy based on your specific system and application needs.

Uses for Recovered Heat, Hot Water or Steam

The recovered hot air or heat from the compressor can then be transferred through water-cooled or air-based systems, making it available for various heating purposes. These practical applications include:

• Water Heating: Generating hot water for uses such as cleaning, sanitation, or as pre-heated water for industrial processes like pre-heating a boiler system or providing heating for washroom facilities.
• Space Heating: Using the hot air or water for space heating systems to warm premises, which is especially valuable during colder months.
• Industrial Processes: Supporting industrial heating systems, such as in food and beverage production where precise temperature control is crucial.

By installing these systems, businesses can recover heat energy and convert it into useful energy for applications like water heating, reducing the need for other energy sources.

Key Components in Heat Recovery Systems

Air Compressor Heat Recovery is the process of capturing the hot air expelled during the compression phase and redirecting it to useful purposes, like heating hot water or providing space heating.

Main Components:

• Rotary Screw Compressors are popular for their efficiency and reliability in large-scale operations. They are ideal for air compressor heat recovery because they generate significant excess heat that can be easily captured.
• Heat Exchangers transfer heat from the compressor to process water or air. These systems, especially when equipped with PTG systems, help industrial manufacturers lower energy costs by reducing the need for additional heating sources.

Benefits of Using Heat Recovery for Air Compressors

Heat recovery is a valuable way to improve the efficiency and sustainability of any industrial air compressor system. As highlighted in the introduction, a large share of the energy used during compression is converted into heat. A well-designed waste energy recovery system captures this heat and converts it into usable energy for heating water or air.

Energy and Cost Savings

Heat recovery systems can heat water to over 70 °C using the waste heat generated during compression. This reduces the need for traditional heating systems powered by gas or electricity. The return on investment (ROI) is often achieved quickly, typically seen within 12-24 months. When equipped with PTG heat exchangers, even smaller compressors can provide sufficient heat for industrial processes or space heating. In many cases, heat recovery compared to fuel oil heating results in lower energy bills and faster returns on investment.

Environmental and Operational Efficiency

Using hot air heat recovery reduces carbon emissions and supports sustainability goals, contributing to the UK’s Net Zero targets and enhancing a brand’s green credentials. Warm air from the air cooler or compressor exhaust can be redirected into buildings, particularly useful during colder seasons. This helps maintain proper ventilation, improves ambient temperatures, and supports the performance of the equipment as the air cools before discharge to outdoor air. Atlas Copco compressors are a good example of systems designed to support this type of energy reuse effectively.

Scalable and Long-Term Value

Heat exchangers are available in different configurations to suit a wide range of compressor types. Heat recovery can make a significant impact on heating costs depending on compressor size, usage patterns, and how the recovered heat is applied. The savings that can be achieved using hot air heat are considerable in many industrial air applications. An Atlas Copco representative or a Control Gear specialist can assist with identifying the most effective solution for your site. A detailed heat recovery brochure can often provide specific performance data for different models.

How Much Can an Air Compressor Heat Recovery System Save?

In many cases, 50 – 94% of the waste heat from air compressors is recoverable. Modern systems can recover up to 90% of the energy supplied to the compressor. Here is what affects the savings:

• Larger or oil-free compressors generate more heat, which can be captured.
• Continuous running saves more than sporadic running.
• If you use heat for an industrial heating system or service water heating, the savings will vary based on how effectively the heat is utilised.
• Well-maintained systems with good recovery mechanisms will capture more heat.

In financial terms, you could save 10 – 30% on total energy costs for industrial operations. At Control Gear, we recommend a site assessment to get an accurate quote before deciding the best course of action.

Challenges in Heat Recovery Systems

While energy recovery systems offer clear benefits, there are also some challenges to consider:

Compatibility

Not all compressors are designed to work with heat recovery systems. It is important to select a compressor that is compatible with a heat exchanger system. Screw compressors, for example, may require special modifications or an integrated heat recovery solution to optimise performance.

Initial Costs

The upfront investment for energy recovery equipment can be substantial. However, the payback period is generally short, and government rebates or tax credits for energy-efficient upgrades may be available to help offset these initial costs.

Infrastructure Requirements

Retrofitting a system to accommodate heat recovery may require adjustments to existing infrastructure, such as installing new ductwork, plumbing, or electrical systems to support air heat recovery and water heating.

Temperature Mismatch

The temperature of the recovered heat must match the application’s needs. A heat recovery calculator can help determine if the system will provide enough heat for specific processes, such as air for space or process water heating.

Seasonal Variability

The best application for recovered heat may change with the seasons. For example, waste heat is better suited for space heating in colder months and can be redirected for hot water production during warmer periods, requiring a flexible system design.

Maintenance

Regular maintenance of steel plate heat exchangers is necessary to ensure the system remains efficient. Dirt buildup, clogging, or wear and tear can affect heat transfer efficiency, reducing the system’s overall benefits.

How to Maximise the Efficiency of Your Heat Recovery System

To ensure your heat recovery system operates efficiently, consider the following steps:

• Select the Right Equipment: choose compressors that are designed for heat recovery, such as models with integrated heat recovery options from Control Gear and Atlas Copco UK.
• Optimise Heat Exchangers: use high-quality heat exchangers to minimise heat loss during transfer. Water-cooled and well-maintained air-based systems will help capture and use as much excess heat as possible.
• Conduct Regular Audits: use a heat recovery calculator to evaluate your system’s performance and ensure it meets your energy and heating requirements. Regular energy audits, such as a comprehensive AIRScan audit, can also help you identify areas for improvement and calculate the potential savings.
• Maintain the System: professional maintenance, such as cleaning and checking components like heat exchangers, and oil coolers, will ensure the system continues to work efficiently over time. This will help recover heat without performance issues and comply with carbon emissions and energy consumption targets.

Compressed Air Heat Recovery – The Next Step

Heat recovery for air compressors is a powerful tool for improving energy efficiency and reducing operational costs. By using air compressor heat recovery systems and optimising heat exchangers, businesses can repurpose waste heat for useful applications, such as space or process heating, reducing overall energy consumed.

At Control Gear, we specialise in providing solutions that maximise energy savings through effective recyclable heat strategies. Whether you are interested in compressor heat recovery for water heating or exploring options for air heat recovery, our team can help you implement the right system for your needs.

Ready to reduce energy consumption and lower energy costs? Contact Control Gear today to learn how we can help you make the most of your compressed air system with heat recovery solutions.

FAQ

What types of compressors work best with heat recovery systems?

Industrial air compressors, particularly rotary screw models, are well suited to heat recovery due to the high volume of compressor heat they generate. When equipped with PTG heat exchangers, these systems can recover waste heat efficiently and repurpose it for heating applications such as hot water or space heating.

How can heat recovery reduce energy costs in industrial settings?

By capturing the compressor’s exhaust heat, heat recovery systems can heat water to usable temperatures, often above seventy degrees Celsius. This reduces the need for traditional heating fuels such as gas or oil. Heat recovery compared to fuel oil systems, usually delivers noticeable cost savings and improved energy efficiency over time.

Can heat recovery systems be added to existing compressor installations?

Yes, waste energy recovery systems can often be retrofitted to existing air compressor setups. While integration can be complex and require careful design, with proper ventilation and the right heat exchanger in place, even air-cooled compressors can contribute to energy savings. A site assessment can help calculate the usable heating energy and determine the best configuration.