‘Only a mix of measures leads to success’

Prof. Sauer, energy efficiency according to DIN ISO 50001 is now a ‘must‘ at every large company, but is primarily based on individual measures. Is this approach sufficient to tap into the potentials leading to a sustainable energy supply?
No. Unfortunately, implementing individual measures is not sufficient. Besides increased efficiency, a sustainable energy supply also gives consideration to renewables on the supply side, if possible, and it has to be coordinated with the energy consumption. We are therefore pursuing an overarching approach at the IPA in order to analyse the dependency of various measures and achieve an overall optimisation in this way.

How do you proceed at the start of a corresponding project?
To determine the overall optimisation in a complex energy system, we have to combine the various individual measures using a simulation model. This enables us to adapt the design and the operation of the systems accordingly.

If only a mix of different regenerative energies leads to success, what are the prerequisites for being able to combine multiple measures?
Our project with Mercedes-Benz AG and its Factory 56 is one example of this. There, we have jointly developed an overarching energy and load management system that allows us to actuate various systems such as ventilation systems, PV systems and energy storage technologies in combination. In addition to efficient operating states, this also enables us to maximise the PV system’s own consumption and to react to the energy market depending on the situation.

Are these also the measures that the Fraunhofer IPA implements to support food producers?
We are working together with food producers on the topic of climate-neutral production in various projects. The steps involved build on one another: increase in energy efficiency, integration of regenerative energy sources and increase in the self-usage rate of renewable energies. We can help to reduce energy consumption, particularly in the areas of waste heat recovery and the evaluation of usage strategies. Unfortunately, this is an aspect that is still being paid too little attention in the food industry.

So many producers may well not be aware of how much energy is lost by not using waste heat. What solutions do you offer for companies to exploit their potentials better?
Together with the companies, we develop transformation paths to an electrified heat supply using heat pumps, for instance, integrate alternative fuels such as biogas and hydrogen, optimise the procurement of renewable energies and establish interfaces to the energy market. As an application-oriented research institute, we can offer particular added value in this respect. Our energy flexibility audit enables us to identify potentials and therefore increase the self-usage rate.

You can only structure your use of energy efficiently if you have a detailed overview of your consumption. What are the milestones for companies on the energy data analysis roadmap?
The energy data analysis enables us to derive targeted digital services in order to optimise CO2 emissions and the cost effectiveness of the energy system ‘at the push of a button’. In our experience, many companies are already collecting their energy data to a certain extent, but are still not using them sufficiently. The first step initially involves identifying relevant data sources and analysing their quality. Based on this, various algorithms can be used, for instance, to derive energy efficiency measures or to detect anomalies in the signal path.

Can you explain that using an example?
As part of the KMU-Innovativ CS4I project, for instance, the Fraunhofer IPA has developed solutions for reducing the carbon footprint in the beverage industry – in this case, that of Gerolsteiner Brunnen GmbH & Co. KG. Specifically, digital services are developed that initially provide support in generating a live carbon footprint which can be used as the basis for deriving efficiency measures.

What obstacles do you encounter in doing this?
First of all, it proves challenging to include emissions along the entire value chain, from cultivating the apples for the apple juice spritzer up to and including the emissions for transport to the end customer. It is important for companies to register the emissions of the upstream and downstream supply chain in order to arrive at a comprehensive understanding of their own emissions. Investment decision instruments were additionally developed in order to transparently factor in sustainability aspects when purchasing a new filling line, for instance. It is important to establish an understanding of the fact that emissions have to be factored in as early as during investment decisions.

You mentioned that it is also important to detect anomalies. What do you mean by that?
Compressed air, for instance, is used to inflate PET bottles in the beverage industry and is one of the most expensive forms of energy in the industry. Detecting anomalies for the compressed air system can help to identify expensive and CO2-intensive leaks, ideally immediately after they occur, and to automatically report them to the maintenance department. To do this, it is first necessary to take a look at which sensors are already installed and how they have to be supplemented if necessary. Anomaly detection can then be trained based on the measured data in order to subsequently implement continuous system monitoring.

Let us move on to sector coupling. Is it an option for the food industry and if yes, in which form can this concept be integrated into the production processes?
One important approach is coupling the electricity and the heat sector. A large part of the energy used in food production is needed in the form of heat and cold. Electrifying the heat supply therefore makes it easier to use electricity from renewable energies. Another option is offered by cogeneration, as it enables the total energy input to be reduced and can supply electricity, heat in the form of steam or hot water and, if necessary, also cold at the same time. Due to its high, continuous demand for process heat at low to medium temperature levels, both cogeneration plants and heat pumps are suitable for the food industry. A compressed air heating system (CAHS) additionally offers the option of generating compressed air and heat.

A balance between energy generation and consumption also has to be ensured at all times. What role can regenerative energy sources play in that?
The disadvantage of regenerative energy sources is that energy generation can vary significantly depending on the time of day and the season. If a high proportion of electricity is generated using renewable energies, an imbalance can therefore occur between generation and demand. To restore the balance in such situations, it is necessary to implement measures that make demand more flexible – by using storage systems, for instance. Food industry companies can provide support on both the generation and the consumption side in this.

… meaning?
By producing regenerative energy on site, the company can cut its energy costs and contribute to the decarbonisation of the industry. The location’s energy flexibility can be increased on the consumption side by building storage systems, for example, but other technical and organisational measures can also be implemented. Regarded as a low-temperature storage system, for instance, cold stores can be cooled more or less extensively in a defined, limited temperature range. This can be used to temporarily increase the consumption load and reduce it again later on.

One of the focuses at the Fraunhofer IPA is the development of thermal energy supply concepts and technologies that meet sustainability and economic requirements. What approaches do you see here for designing future-proof processes for the food industry?
The majority of heat is still generated by combusting gas or oil today. The necessity of transformation can therefore be used as an incentive to rethink thermal energy supply concepts. The intelligent coupling of various technologies, hybrid or bivalent energy supplies and consideration of H2-ready technologies are promising in this regard. This combined approach enables ecological added value to be generated in the short term and economic advantages to be achieved in the long term. As mentioned before, another option is the use of cogeneration plants and heat pumps to reduce the total energy input and therefore also increase sustainability. In addition, renewable fuels are already able to significantly reduce greenhouse gas emissions today and will be able to avoid them completely in the long run with hydrogen.

Another specific example to finish off with: a demonstrator with which the feasibility of a bivalent compressed air supply was validated was set up at Fraunhofer IPA as part of the ‘SynErgie’ project – is such a system an option for the food industry? What prerequisites need to be met for it?
The hybrid compressed air heating system is able to generate compressed air, heat and electricity at the same time using gas and electricity. In normal operation, the CAHS is powered by the gas motor, which drives a compressor and therefore generates compressed air. The heat from the exhaust gas and the compressor can be used in parallel. If less compressed air is needed, an electric motor can be used as a generator to produce electricity.

What are the advantages of this?
In the case of negative electricity prices, compressed air can be generated by the electric motor as a motor. The hybrid CAHS therefore offers the advantages of a long service life and high efficiency as well as the flexibility of switching between gas and electricity as fuels. Base load applications are particularly sensible in this case, because it always has to be ensured that the generated heat is used in normal operation (via the gas motor). Industrial sectors with high compressed air and heat requirements are therefore particularly suitable for integrating hybrid CAHSs – and that also includes the food industry.