An introduction to air compressor heat recovery
Virtually all industries use compressed air. Often called the “fourth utility” because of its tremendous importance to millions of businesses. With this, it is worth diving into how to reuse heat generated from air compressors. This article focuses on industrial waste heat recovery technologies to help you understand.
Producing compressed air comes at a cost. This is reflected in electricity costs, which make up the biggest share of the total cost of ownership of an air compressor. In addition, the energy a compressor consumes also constitutes 99% of its CO2 emissions.
Fortunately, there are opportunities for companies to minimize these energy costs.
Most notably, they can invest in energy-efficient equipment eliminating excess heat.
- For example, a variable speed drive (VSD) compressor can reduce energy consumption by up to 60%.
- In addition, they can optimize their compressed air system to ensure that no energy is wasted. This can be done by preventing air leaks and making sure that the working air pressure is not too high.
How you can ensure that minimal energy is wasted when operating such equipment?
This is where waste heat energy recovery applies.
Recover heat from the compressor
However, there is another source of tremendous waste that is often overlooked.
The compression of air generates a lot of heat. This heat is typically dissipated to ensure the compressor does not overheat and the compressed air is cool enough for its application. In most cases, this heat vanishes into thin air.
That is particularly wasteful, especially considering that over 90% of the electrical energy a compressor uses is converted into compression heat.
By adding waste energy recovery technology to a compressed air system, much of the energy a compressor consumes can be recovered. This involves reusing heat generated elsewhere.
Operating costs are reduced because the vast majority – up to 94% - of compression heat can be recovered. This is the reason such a heat recovery system usually pays for itself in less than three years.
Know how your compressor is cooled
Before deciding to invest in a waste energy recovery system, it is important to make the distinction between air-cooled and water-cooled compressors. The energy recovery process in the former is particularly easy and inexpensive, which makes it suitable even for small compressors.
The heat energy recovery in the case of water-cooled compressors is a bit more complicated. It may involve additional components, such as pumps, a heat exchanger (which is optional in most Atlas Copco compressors) and control valves.
That is why it only makes economic sense for compressors of more than 22 kW. However, the resulting cooling water can generate hot water with a temperature of up to 90° C, which is ideal. This can be used for a variety of processes.
Uses for recovered heat, hot water or steam
That brings us to the next important topic: What can a business do with the recovered heat?
The most obvious example is to use the hot air from an air-cooled compressor to heat a production hall or another building. However, this is limited by the time required for space heating systems, ie during cold weather.
Other uses can be hot water heating for laundries, industrial cleaning and sanitary facilities.
The hot water or steam from a water-cooled compressor has many versatile uses in a wide range of industries.
These include the following sectors and applications:
- Automotive (various production processes),
- pharmaceutical industry (drying and sterilization),
- food and beverage (pasteurization, drying and cleaning),
- textiles (coloring),
- chemicals (various refinery processes),
- electronics (clean room sterilization)
- and many more.
How much can an air compressor heat recovery system save?
It is possible to predict the percentage of energy savings of a green technology. An example is how a variable speed compressor or dryer operates compared to a conventional model.
The savings of an energy recovery system depend on a wide range of factors. These include:
- the types and sizes of compressors
- how often they run
- what type of cooling they use
- the compressed air system,
- the opportunities a company has to use the recovered heat.
In most cases, however, the savings are substantial and some energy recovery systems even pay for themselves after just one year.
An added benefit is that such a system not only lowers production costs but can also significantly reduce the CO2 footprint of a business. This in turn, might make such an investment eligible for government incentives offered for the purchase of green technologies.
Lots of reasons to switch to a waste energy recovery system. Still not sure whether your business will benefit? Simply check in with your Atlas Copco representative, who can give you all the information you need.