Beer without hops? Inconceivable! Much of the world's finest hops originate from the Hallertau region in Bavaria, where top quality hops plants have been growing for centuries. A main goal of any subsequent processing is to maintain this quality. The plant, which is part of the hemp family, must be carefully dried after harvest while it is still as fresh as possible. Until recently, the systems for drying hops have been mostly controlled manually, which often resulted in either too much or not enough water being removed from this vital beer flavor ingredient, subsequently degrading the shelf life or brewing results. The company ATEF Euringer & Friedl GmbH decided to address this problem: With the help of a refined plant and control system solution based on B&R technology, hops can now be processed almost fully automatically, faster and with less energy - and all this while maintaining the hops' top quality.

In early autumn, visitors are greeted with warm, aromatic air as they enter hops cultivator Johann Brenner's new plant close to Pfaffenhofen in Hallertau (also called Holledau). Every second, workers thread the ends of the hops vines, which can grow up to seven-meters in length and are cut just above the ground when harvested, into a device that lifts them close to the ceiling of the plant, where they are moved into a picking machine. The flower clusters are then separated from the rest of the plant, and actual processing of the flower clusters into a product that can be stored and further processed is begun.

"When doing this, drying and conditioning the hops are crucial steps. They considerably influence the quality of the hops and the price that can be attained by the hops cultivator," explains Michael Friedl, Co-owner and Managing Director of ATEF Euringer & Friedl GmbH, the company that automated the system components for this process using B&R technology.

Visualization and control of the hops drying system takes place using a Power Panel 420 from B&R.

The picking machine separates the flower clusters from the rest of the plant.

The compact ACOPOSinverter X64

Drying and conditioning retains the quality of the hops

The hops are green when harvested and have a water content of 80 to 85%. Therefore they must be dried immediately in order to prevent spoilage. If this does not occur, the hops heat up after a short time in storage, which negatively effects appearance and reduces the amount of alpha acid (the flavoring compounds that give the beer its typical bitter note and increase its shelf life). Directly after harvesting and automatic picking, the flower clusters are normally - as with hops cultivator Johann Brenner - placed in kiln dryers where warm, dry air flows through until the water content is approximately 8.5 to 9%. In large conditioning chambers where the hops are stored for several hours after the drying process, conditioned air ensures even distribution of the moisture in the hop. Afterwards, the hops are ready for storage and can be pressed in bales.

"However, the problem with most drying and conditioning systems used until now is that improper drying behavior of the hops caused by the structure of the flower clusters is not sufficiently accounted for. For example, the power of the heaters and the design of the sensors used in the systems are not implemented correctly and the air composition, temperature and humidity are controlled manually according to the gut feelings and experience of the respective user," explains Michael Friedl. "As a result, the systems often use energy ineffectively; they just 'simmer' the hops (which greatly decreases the drying power) or waste too much energy."

In the past, automation of the drying process failed because, among other things, there was no controlled variable and the air velocity inside the kiln could not be measured directly at all positions - that is until ATEF, in close cooperation with the work group for hops cultivation, production engineering from the Bavarian State Research Center for Agriculture decided to take things into their own hands.

"We took a look at a series of measurements from the research center and found out that the residual moisture in the hops can be derived from the "moisture sorption isotherm curve". We use this information to control the air composition using B&R technology. We calculate the average air speed, which is also critical for the drying process, according to the laws of thermodynamics using the known energy content of the incoming and outgoing air and can in this way optimally adjust the condition of the air to the actual requirements," explains the ATEF Managing Director. Improvements to the construction of the systems and clever use of the heat produced by the process do the rest.

Energy consumption reduced to nearly the theoretical minimum

The results of all these measures are impressive: The system designed by ATEF for the hops cultivator Johann Brenner only requires 16.5 liters of fuel oil to dry 50 kg of hops, reduces consumption in relation to conventional solutions by almost half and comes extremely close to the theoretical minimum value of nearly 15 liters determined by the laws of physics. At the same time, the drying time of approximately one and a half hours shortens to one hour after being dumped into the drying mechanism until the transition time and the output increases from approximately four kilograms per square meter of kiln in an hour to approximately 7.5 kilograms of dried hops. ATEF has made substantial progress in this area with its 'Klimabox'.

"The hops leave the system with optimum quality and this is done with a high degree of repeatability and minimum drying and conditioning costs. Because of the high degree of automation and the simple and clear user interface, the system can be operated by almost anyone," says Michael Friedl in summary.

B&R products reduce costs for procurement and maintenance

"In spite of these benefits and the short amortization time of the system, the investment costs are top priority for many operators. For us, the costs of acquisition, service/maintenance and replacement part storage were decisive when selecting our automation partner."

ATEF didn't have to look long for the right partner, as the ATEF Managing Director explains: "I had already heard many positive things about B&R and was enthusiastic about the price/performance ratio of the products right from the start. For example, the I/O is characterized by low maintenance costs because the electronics can be exchanged quickly and individually since they are isolated from the wiring, which substantially reduces the costs of the purchasing spare parts. I was also enthusiastic about the fact that I could take care of the entire control software including the visualization application with the Automation Studio engineering environment from B&R and did not need several tools - as is normally the case with other suppliers. That made the engineering work much easier and saved money as well."

Automation Studio: Effective code generation and error searching

From the automation expert's perspective, engineering was also faster because Automation Studio has an ANSI C interface and therefore it is possible to effectively create and in particular debug the software.

A B&R Power Panel 420 serves as hardware platform for the control software and visualization application. It makes the automation solution more economical because a separate controller is not required thanks to the integrated CPU. The panel is installed in the door of the controller switching cabinet at a central location in the system. The DIN rail mounted B&R X20 System I/O modules are connected with the panel using the fast and economical X2X Link communication solution. The ATEF engineers also used X2X Link to integrate the power equipment and motor monitoring modules as well as some additional I/O modules in a power cabinet over 50 meters away into the automation architecture, and this also included drives from B&R.

B&R frequency inverters reduce problems caused by faulty operation

"In this system, we also use frequency inverters from B&R and are therefore one of the first users to configure and control these devices via bus," adds Michael Friedl. "We decided on this procedure in spite of the risks generally associated with such a step because in the past we had some maintenance calls that were initiated by users or operators reprogramming the inverters, either inadvertently or for assumed 'optimization' reasons."

A step that ATEF did not regret. The inverters perform their jobs to the satisfaction of everyone involved and the drives have the settings that have been tested and approved by ATEF written to them when the controller is restarted so any adjustments made by others are thrown out.

There are now 14 systems that ATEF have planned and must care for with only a few employees, so the technology must be nearly maintenance-free, as stated by the ATEF Managing Director. "We can only implement our plan and clearly increase the number of systems sold per year if the technology is reliable and low-maintenance, as is the case with the B&R products."