Right-size dimensioning: Demand-orientated design of high-temperature heat pumps
"Don’t worry, you grow into it": What may be true for children's clothing is the wrong approach when it comes to generating process steam and heat with high-temperature heat pumps. Designing heat pump systems in industry requires new strategies to prevent energy waste and optimise costs. We have already implemented such strategies and will explain how they work.
Decarbonising the industry
Cost-optimised and energy-efficient use of process heat
The continuous high demand for process heat and steam in the industry – in the face of high energy prices and the simultaneous goal of decarbonization – is prompting more and more companies to rethink or at least review their heat generation and utilisation. In this article, we take a look at the Right-Rize-Approach for the optimum design of high-temperature heat pumps: an approach aimed at a demand-oriented, highly cost-optimised and energy-efficient use of process heat, advancing decarbonization at the same time.
Optimum sizing of industrial heat pumps
The good news: manufacturers of industrial heat pumps have been thinking for some time about how to size and design heating systems in order to meet demand and optimise costs. Because thinking big is easy – the real art is to dimension industrial heat pumps in such a way that they can cover the heat demand at all times without being oversized. This effectively reduces system and energy costs and optimizes the climate benefits of heat pumps.
The traditional design of process heating systems: often oversized
To understand how the Right-Size-Approach works, we first need to look at how boilers for generating process steam and hot water have been sized to date.
In the past, the design of traditional heating systems focussed on the highest temperatures required within a specific industrial process. Let's take the generation of process steam as an example: numerous industrial processes still work with steam that is generated using fossil fuels.
In simple terms, the traditional technical approach to dimensioning such systems can be summarized as follows:
- Identification of the heat sink in the system or plant that places the highest demands on temperature and pressure of the steam used.
- Summation of all maximum thermal loads in the entire system.
- Design of a heating system that can deliver the total heat output plus safety margins of the system. The system is designed to meet the requirements of the 'most demanding' heat sink in the long term.
- Adjustment of temperature and pressure of the process steam in those parts of the system or plant with lower demands. This means that the steam temperature and pressure is adjusted ‘downwards’, for example by valves. However, unused energy is lost in the process.
In the past, this approach has proven to be reliable and effective when designing heating systems. Effective, but not efficient: The calculated flexibility of the system and the uncertainty regarding the process requirements lead to an immense waste of energy.
Imagine, for example, that you drink several cups of tea every day. This requires a brewing temperature of 80 degrees Celsius. However, you heat your water to 100 degrees Celsius in the kettle and then leave it to cool. Now imagine that your kettle has a volume of 50,000 litres and boils water continuously seven days a week, even though you only need water at 100 degrees Celsius in exceptional cases and 80 degrees Celsius is almost always sufficient. This is energy inefficient and therefore not economically feasible.
The Right-Size-Approach for high-temperature heat pumps: efficient and economical
With industrial heat pumps for generating process heat and process steam, the traditional approach can be reversed: These systems are designed to meet the base demand of the plant and the heat generation is adapted accordingly to the higher temperature requirements of individual processes.
- Identification of an suitable heat level, i.e. the required output at different temperature levels and selection of the levels according to relevant criteria such as output or existing waste heat potential.
- Identification of higher required temperature levels of individual processes in the plant or factory.
- Selection of appropriate technologies for the required higher steam or water temperatures: These might be booster industrial heat pumps, gas-fired or electric boilers or MVR systems (mechanical vapour recompression or steam compression), which can raise the pressure and temperature of the steam if required, but which may be smaller in size compared to the classic design approach.
- Designing the heat pump according to existing waste heat potentials and the required base load, providing the appropriate temperature level – thus continuously meeting the base demand of the system. If necessary, the selected supporting technologies can be adapted to higher temperatures or pressures in individual production steps. This means that virtually no unused energy is lost.
This Right-Size-Approach reduces the power requirement and energy consumption of the entire system. This leads to lower system costs because the utilized heat generators can be designed to be smaller and do not have to run continuously. This also significantly reduces operating costs and the environmental impact.
The highest temperature requirements of these systems are then provided, for example, by separately connected booster heat pumps or electric boilers – while operating costs can be significantly reduced on the whole.
In summary, it can be said that in most cases it is advisable to design the heat pump in such a way that either the existing waste heat is optimally utilised or, if this is available in unlimited quantities, the heat sink is optimally served. As the investment in a heat pump amortises more quickly with increasing operating time, it is often designed for base load operation and the peak load is generated by other means. However, if the aim is maximum CO2 savings, designing the system for peak load is advisable.
Opportunities of the Right-Size-Approach for industrial heat pumps
Global data from the US non-profit research organisation American Council for an Energy-Efficient Economy (ACEEE) shows that the total energy consumption of industrial heating systems can be reduced by 40 to 60 percent if systems for generating process steam and process heat based on fossil fuels are replaced or downsized by optimally dimensioned industrial heat pumps.
The Right-Size-Approach enables the components for steam generation to be expanded as required, allowing other system components to be downsized and their operating times reduced. In combination with other regenerative heat generators such as electrode steam generators or the use of biomethane and hydrogen, demand-based and yet highly cost-optimised heat and steam generation solutions can be created. This also allows for a gradual transition from fossil fuels to a decarbonized process heat generation. High-temperature heat pumps utilise waste heat at a low temperature level to provide heat at a higher temperature level via the so-called temperature lift. In many cases, the use of high-temperature heat pumps allows for transition from centralised to modular steam generation systems, which enables better process control through advanced digital technologies.
This modularity means that parts of the heating system can be shut down when they are not needed without having to switch off the entire system. The inherent efficiency of high-temperature heat pumps reduces power supply requirements, electricity consumption and CO2 emissions in most application scenarios.
This approach often requires a shift in thinking: the demand-based design of heating systems can lead to uncertainties among project managers regarding the performance and reliability of the system. Our consultations with clients and our experience in realising such projects show that these concerns are unfounded. Process heating systems that are dimensioned according to the Right-Size-Approach are powerful, reliable, fail-safe and naturally supply the required process heat in the desired quality at all times. However, they work more economically and efficiently than oversized systems. When it comes to steam and heat generation today, the motto is: performance optimisation instead of performance maximisation.
Conclusion: Demand-led design of high-temperature heat pumps reduces operating costs and improves the environmental footprint
The Right-Size-Approach to the design of high-temperature industrial heat pumps represents a decisive advance in energy-efficient process heat generation. Instead of relying on oversized systems that waste an unnecessary amount of energy and resources, this approach enables demand-based and cost-optimised dimensioning of heating systems according to the motto: "As much as necessary and as little as possible".
For steam pressure, the rule is:
"As high as necessary, as low as possible"
Adapting process heat generation to actual requirements helps companies to position themselves for the future, considerably reduce their operating costs and significantly improve their environmental footprint.
The modularity and flexibility of high-temperature heat pumps is pioneering in this respect: it enables individual system components to be shut on or off as required. This adaptability enables better, more precise process control, supply-oriented utilisation of energy and significant savings in energy costs. While there are may still be uncertainties and a need for consultation when designing according to the Right-Size-Approach, one thing is clear: the days of oversized process heat systems are over. The path is leading towards customised, more efficient solutions that offer optimum performance rather than maximum performance – such as the modular industrial heat pump ThermBooster™ developed by SPH.
For industry, this approach not only provides economic benefits , but also offers the opportunity to actively contribute to climate protection and energy transition. This makes companies not only sustainable, but also sustainably economical and sustainably successful.
