Energy Recovery for Air Compressors
Today, we will discuss energy recovery for air compressors, an important topic for those seeking to optimise their industrial processes. Compressed air systems are major energy consumers, making them an ideal focus for energy-saving efforts. By harnessing the excess heat generated by these systems through heat recovery, businesses can tap into a valuable source of energy conservation.
We will examine the connection between heat and air compressors and delve into the benefits of heat recovery systems. We’ll look at the potential energy savings, seasonal factors, and how modern air compressors incorporate heat recovery in their design.
By the end, you’ll have a better understanding of how heat recovery can help you reduce energy costs, lower CO2 emissions, and improve the sustainability of your operation. So, let’s get started on our journey into the world of energy recovery for air compressors!
Table Of Contents
The Idea Behind Energy Recovery
The processes behind a compressed air system result in high levels of excess heat. Simply put, this is a consequence of compressing air in significant volumes. It’s unavoidable in compressed air setups used in a wide range of manufacturing, vehicle workshops, and environments, where air-powered tools are used.
While the energy consumed cannot be captured post-use and reused per se, harnessing the excess heat generated by compressed air systems is possible. Whether referring to energy recovery or heat recovery with air compressors, the aim is the same: Harness the excess compressor-related heat to reduce energy requirements elsewhere.
This is one of the primary purposes of a heat recovery system. It also reduces CO2 emissions too.
Understanding How Heat and Air Compressors Are Intertwined
Estimates vary, but it is understood that when excluding the initial cost of the compressed air machinery, almost all the subsequent running costs are energy-related. Therefore, anything that reduces the overall energy footprint is worth pursuing.
Why is heat generated at all?
Because compressed air systems use nearby or outside air as an input, then compress it into a smaller space. This activity produces compression heat, a by-product of the process. However, compressed air must be cooled, so the heat is extracted from the system before the compressed air is made available. The extracted heat is then considered ‘waste heat’.
Excess heat is often expelled outside the rear of the factory. Hot air from an oil-free compressor is devoid of oil particulates, so does not pose a risk to the environment. A cooling water system is sometimes used to reduce the total heat level for safety purposes. However, these approaches won’t directly or indirectly save energy.
What is the Potential Level of Energy Saved?
As much as 94% of the energy used for air compressor systems is potentially saved by using its waste heat for water heating and/or space heating uses.
Let’s give an example to illustrate how energy savings are possible:
A plant with an air compressor consumes 400 kW spread over 7,000 hours of annual production activity. For the plant, this adds up to 2.8 million kWh annually in energy. For operations like this, the energy bill is something they’d like to reduce if they could.
Some of the 400 kW is used by running the compressor.
The plant also requires considerable space heating in the colder months to keep employees warm. Expelled hot air from waste heat is already filtered. It only needs to be distributed to where heating is required within the plant, etc.
Also, if running long shifts and providing bathrooms with sinks and possibly showers on-site, then both hot and cold water is required. Instead of relying solely on the existing heating systems for hot water, waste heat from the compressor provides warm water for showers and the hot water taps for sinks too. This reduces boiler usage, saving considerable energy and cuts down wear and tear on plumbing-related equipment too.
Do Heat Recovery Levels Vary Depending on Utilisation?
For example, when using waste heat to deliver hot water to bathroom facilities in a plant, the temperature matters.
Imagine that an oil-free rotary screw compressor and heat recovery system targets a hot water temperature of 90°C, the energy-saving potential is expected to be close to 94 per cent. However, when the water must be adjusted by a few degrees, this alters the energy-saving calculation. Not by much, but it’s fair to say that it does.
Is Heat Recovery Affected by Different Seasons?
When it comes to recovering heat and seasonality, let’s tackle this from a practical level.
Hot Water Systems
To provide hot water, the heat exchanger (or sometimes a PTG heat exchanger) inside the air compressor captures excess heat. Adjustments made to temperature levels ensure it’s suitable for the plant’s hot water system. This avoids tapping the hot water boiler or firing up the water heater unnecessarily.
Colder months typically cause workers to use the hot water in the bathroom facilities more frequently. In the UK, it gets colder in November, and we still sometimes experience chilly days in April. This provides a good run of months where hot water is used frequently, in the warmer months, less so.
Space heater systems, including radiators, have more seasonal usage patterns. While larger plants or factories are difficult to keep warm, nevertheless, space heating won’t be useful all the time.
However, given variable UK weather, plentiful opportunities exist to let air compressor-derived space heating do its work. This saves on fuel oil, heating water for a network of radiators, etc.
Do All Air Compressors Have Heat Recovery Potential?
Modern air compressor systems often include heat recovery within their design. Screw compressors are useful for heat recovery, as are oil-free air compressors for somewhat streamlining the recovery process.
Given that heat recovery lowers energy bills, there is also a market for separate heat recovery equipment to augment an existing compressor system. This is good news to help reduce the total industrial electricity consumption overall.
Compressor Plant Location vs. Utilisation Location
One limitation of heat recovery systems is the need to be as close as possible to where excess heat is to be used.
Therefore, when planning to use hot water for bathrooms and showers, the compressor plant room, or installation location, benefits from being closer to where these are situated.
Similarly, to use space heating in the factory, it’s helpful if the ductwork from the compressor plant room to where workers are situated isn’t extensive. Otherwise, the ductwork installation cost is higher, and some heat will be lost along the route.
Let Anglian Compressors Reduce Your Energy Bill
Heat recovery is a critical aspect of air compressor usage to lower energy costs. As compressed air specialists, Anglian Compressors can set up improved systems or supply a new air compressor system for enhanced air heat recovery.
Depending on the implemented system, the cost of heat recovery equipment is often recovered within 3-4 years. This provides true savings to businesses for years to come. Get in touch.
Contact us below.