Building a Waste Heat Recovery System

When one thinks of wasted resources, the mind tends to picture certain things: sheet metal, wood, food stuffs, etc. We tend to pigeon hole ourselves into very physical representations of “waste” and focus on mitigating lost profit through eliminating these sources of physical waste. And while this is a valid approach towards waste mitigation and efficient plant management, there are less corporeal forms of waste that can also be addressed. 

Waste Heat, for example, runs rampant in a manufacturing industry that runs on large pieces of machinery that generate massive amounts  of heat — heat that could be repurposed into energy for other processes within a factory! 

Before you disregard these claims as bogus, a study performed by researchers at UC Berkeley just 3 years ago found that the US consumes an average of 100 quadrillion Btus of energy in a given year and, of those Btus, as much as 60% of that energy is dissipated as waste heat.

So, what is waste heat? And, even more importantly, how can that heat be repurposed into usable energy with hardware such as heat exchangers and industrial grade computers? 

What is Waste Heat

To make an abstract term a little more concrete, “waste heat” is energy (heat) produced during the industrial process that is not used in any productive capacity and is then wasted into the environment.

As we mentioned, this waste heat can be produced across many disparate steps during manufacturing. Radiation from industrial equipment, heat discharged from combustion processes, even heated water and steam being expelled are all examples of energy that could be repurposed with the right waste heat recovery system. 

What is Waste Heat Recovery

 A waste heat recovery system, like the name aptly implies, is a system designed to capture this wasted heat and use it to generate electrical or mechanical power or even be reused for other processes that require heating. 

As an example, consider the average furnace in a steel working plant. The furnace heats incoming materials and, in the process, emits heat that is dissipated from its walls and openings. This heat is also often thrown out into the environment through chimneys and smoke stacks. With a waste heat recovery system, a heat exchanger is installed which, instead of sending this heat out into the atmosphere, uses it to perform other tasks such as pre-heating combustion air needed to burn fuel like liquid propane. Many times, this heat can even be recycled and used to heat incoming air that is then pumped back into the furnace, prolonging its operation without needing to waste money on energy needed to heat incoming air.

Unfortunately, as impressive as this sounds, not all heat can be repurposed and converted into usable energy. Higher temperatures of waste heat conventionally provide more energy when repurposed, meaning manufacturers that perform processes that only give off low levels of heat may not see a return on their waste heat recovery investments. 

Thus, there are a few recommended practices inherent to both learning whether your facility gives off enough heat to even warrant building a waste heat recovery system and building said system.  

Building a Waste Heat Recovery System

Building a waste recovery system requires three key things. Firstly, you need to know what kind of heat you’re dealing with — what temperature, how often it’s being produced, and when/where it’s available. All of these variables will have a direct impact on how you build your waste heat recovery system (and may even rule out building one in the first place). 

Secondly, a heat exchanger like the one we mentioned in our furnace example is the tool that will actually perform the capturing and repurposing of heat. There are several types, each fit for different types of manufacturers, and picking the right one is essential to building a waste heat recovery system that provides value. 

And finally, you’ll need a plan for what to do with that waste heat once it has been captured.