When manufacturers begin exploring waste heat recovery or industrial heat pumps, the conversation often moves quickly towards equipment.
Which heat pump should we use?
What temperature can it deliver?
How large should the heat exchanger be?
What efficiency can the supplier guarantee?
These are important questions, but they are not the first questions that should be asked.
A high-performing piece of equipment does not automatically create a successful industrial decarbonisation project. It must be connected to an available heat source, serve a useful demand and operate within the physical and operational constraints of the factory.
That is why process integration frequently matters more than equipment selection.
A factory is not a blank sheet of paper
Most industrial waste heat recovery projects are retrofits. The factory is already operating, the production equipment is already in place and the site may have been modified several times during its working life.
New equipment must fit around existing:
- Ductwork and pipework
- Production schedules
- Temperature requirements
- Control systems
- Electrical capacity
- Maintenance access
- Structural limitations
- Safety procedures
- Planned shutdown periods
A heat pump may perform perfectly under its rated conditions. But if the available heat source falls below the required temperature during part of the production cycle, the system will not deliver the expected output.
A heat exchanger may be highly efficient. But if it adds too much resistance to an exhaust system, it could affect process airflow, fan energy or production performance.
The equipment can be technically sound while the overall project remains poorly integrated.
Start with the process, not the product
Effective process integration begins by understanding how energy moves through the factory.
Where is heat generated? When is it available? How does its temperature and flow change? What else is contained in the exhaust stream? Where is the factory currently purchasing energy to create heat elsewhere?
The strongest opportunity is not necessarily the hottest exhaust. It is usually the source that can be matched reliably with a useful and consistent demand.
For example, an exhaust stream may contain a considerable amount of recoverable heat during production. However, if the hot-water demand occurs several hours later, the two energy flows cannot simply be connected directly. Thermal storage, revised operating schedules or a different integration strategy may be required.
Similarly, low-grade heat should not automatically be dismissed. It may not be hot enough for direct reuse, but it could provide a suitable source for an industrial heat pump that upgrades it to a useful process temperature.
Industrial waste heat utilisation is therefore not only about capturing energy. It is about making that energy available in the right form, at the right temperature and at the right time.
Source and demand must be studied together
Waste heat recovery systems are sometimes assessed by calculating how much energy is leaving a stack, dryer or cooling circuit. That identifies the theoretical opportunity, but it does not establish how much of the energy can be used.
A proper assessment should consider both sides of the system.
On the source side:
- Temperature and flow rate
- Operating hours
- Production cycles
- Moisture content
- Dust or corrosive contaminants
- Seasonal variation
- Pressure limitations
On the demand side:
- Required delivery temperature
- Timing and duration
- Minimum and peak load
- Existing boiler or burner operation
- Process quality requirements
- Opportunities for thermal storage
- Acceptable backup arrangements
Recovering more heat than the factory can use does not improve the business case. In some situations, a smaller system that operates consistently may provide greater value than a larger system designed around an occasional peak condition.
This is why equipment should be sized around actual operating data rather than existing equipment capacity or a coldest day assumption.
Integration must protect production
Manufacturers do not invest in industrial energy efficiency to make production less reliable.
Any new system must operate without compromising product quality, cycle times or output. It also needs to respond safely when conditions change.
This means answering practical questions before the equipment is ordered:
- What happens if the heat source becomes unavailable?
- Can the existing boiler or an electric heater provide backup?
- How will the system respond during start-up and shutdown?
- Can individual parts be isolated for maintenance?
- Will a bypass be required?
- How will the new controls communicate with existing equipment?
- Can the factory continue operating during installation?
- How will performance be measured after commissioning?
These are process-integration questions. They determine whether the system becomes a dependable part of production or an additional operational burden.
Controls are part of the engineering solution
Industrial processes rarely operate at one fixed condition.
Production rates change. Product types change. Exhaust temperatures fluctuate. Heat demand rises and falls. Equipment is taken offline for cleaning and maintenance.
The control system must constantly manage these variations.
It may need to decide when recovered heat should be sent directly to the process, when it should charge a thermal store and when an existing boiler or electric heater should provide supplementary heating. It must also prevent unstable switching between systems and respond appropriately to faults.
A strong mechanical design with weak control integration will not achieve its intended performance. Controls should therefore be developed as part of the process design, not added at the end of the project.
Installation is also part of process integration
Even the right technical concept can run into difficulty if it has not been designed for the realities of a live site.
Factories often have congested plant areas, restricted lifting routes and limited opportunities to connect to critical production equipment. Most construction may be completed while the site remains operational, but final connections can still require carefully planned isolation windows.
Off-site fabrication, phased installation and early coordination with the site team can reduce disruption. However, these decisions need to be made during design. They cannot be left until the equipment arrives.
At wienerberger’s Warnham brick works, Heatcatcher delivered a system that recovers heat and water from seven operational drying-chamber exhausts. The recovered energy supplies two 1.3 MW thermal high-temperature heat pumps, which provide hot water at up to 90°C to heating systems installed within the chambers.
The system was integrated into an existing operational factory. That required more than selecting heat pumps with the appropriate output. It involved connecting seven exhaust stacks, installing a heat recovery tower, modifying the drying chambers, integrating new hot-water heating systems and coordinating the work around ongoing production.
The project also created benefits beyond gas and carbon savings. Condensed water is returned to the manufacturing process, to significantly reduce the sites water consumption.
That wider value came from considering the complete process rather than treating the heat pump as a standalone asset.
A similar principle applied at wienerberger’s Sandtoft concrete roof-tile factory. Existing curing chambers had been heated by oil-fired boilers. The integration of air-source heat pumps required modifications to the existing hot-water system and controls, together with thermal buffer tanks to help match supply with the curing load.
Again, the equipment was only one part of the solution. The project depended on understanding seasonal heat-pump performance, the thermal requirements of the curing process and how the new system would work alongside the existing installation.
Technology should follow the site assessment
There is no single technology that is right for every factory.
Depending on the process, the appropriate solution might involve direct heat reuse, a gas-to-water heat exchanger, a heat recovery tower, thermal storage, an industrial heat pump or a combination of technologies.
The purpose of the feasibility stage is not to justify a predetermined product. It is to identify which heat decarbonisation solutions are technically and commercially appropriate for that site.
This requires a technology-agnostic assessment of:
- Recoverable heat
- Useful demand
- Required temperatures
- System efficiency
- Installation constraints
- Operational resilience
- Capital and operating costs
- Carbon reduction
- Maintenance requirements
- Future production plans
Only once those factors are understood should specific equipment be selected.
The best equipment is the equipment the process can use
Manufacturers do not ultimately need heat pumps, heat exchangers or thermal storage tanks. They need reliable process heat with lower energy use, lower emissions and an acceptable commercial return.
Equipment selection contributes to that outcome, but it cannot deliver it alone.
The success of industrial process waste heat recovery depends on how well the system fits the source, demand, site, controls and production schedule. When these elements are considered together, energy recovery from waste heat can become a dependable operational asset.
When they are considered separately, even excellent equipment can underperform.
The right question is therefore not simply:
“Which technology should we install?”
It is:
“How will this technology work within the process that keeps our factory running?”