Process Cooling and Power Generation for Plastic Injection Molding Machines with Adsorption Chillers

January 2, 2014

Since May 2013, the TRANSpofix Company has benefited from its combined cooling, heat, and power (CCHP) system located at its headquarters between the German cities of Nuremberg and Regensburg. The company produces its own electricity with the help of three micro cogeneration units (Combined heat and power – CHP) and uses the resulting waste heat for heating and cooling. As an innovative company specialized in the manufacture of state-of-the-art transport systems and the corresponding plastic and aluminum parts (thick-walled polyethylene), it was almost a given that the company would also use an extremely efficient HVACR system.

After careful planning, Willibald Hergeth, managing director of TRANSpofix GmbH, and Andreas Stephan, junior manager of Stephan Heizungsbau GmbH, agreed on a combination of three SenerTec Dachs CHP units and three InvenSor adsorption cooling units. The cooling units developed by the Berlin-based company InvenSor have already received numerous awards for their efficiency. The adsorption chillers are powered by the waste heat from the combined heat and power units installed at the TRANSpofix plant. These types of systems are the state-of-the-art technology available for applications such as cooling server rooms and are now becoming increasingly popular for applications in industrial plastics manufacturing.

The installed CHPs generate power for TRANSpofix’s entire headquarters in Berching as well as for operating the injection molding machines used to manufacture parts. The waste heat generated is then channeled as operating energy to the three InvenSor adsorption cooling units. Excess heat is used to heat the building during the winter. The thermally-powered chillers can generate cooling energy from waste heat using only a minimal amount of electricity. They use water as an environmentally-friendly refrigerant and as such have a significant advantage over the previously used compression refrigeration systems as far as the environment is concerned.

Advanced system acts as a model for the entire industry

The three LTC 10 plus (Low Temperature Chiller) adsorption units operate at TRANSpofix with a combined cooling capacity of 24 kW. As such, they not only cool the injection molding machines, but during the summer also cool the company’s entire office space (900 m2 / abt. 9,700 ft2). At sufficiently cold outside temperatures during the winter, the production systems are cooled with the help of an integrated free cooling function, which allows the waste heat from the CHP units to be available for heating. This is perfection in combined cooling, heat, and power. The cooling energy produced is channeled to the production floor in the form of water and used there to cool the molded plastic parts. Due to the year-round use of the three CHP units and the InvenSor adsorption cooling units, this system is extremely efficient, with a static amortization of the entire CCHP system in only five years – which is an extremely short period of time for major industrial systems.

In fact, the system exceeded the expectations of Willibald Hergeth, managing director of TRANSpofix GmbH: “I have to say that the savings up until now have truly been immense. All of the components of the CCHP system work flawlessly together, and we have had practically no downtime thus far.”

A 3,500-liter hot-water buffer tank is located in the same room as the three adsorption cooling units, and this tank holds the heat that is not directly fed into heating the building or to power the adsorption cooling units. The same applies to the cooling side: Here the company installed a 2,000-liter cold-water buffer tank to meet its needs in the event of a high demand for cold water. Both buffer tanks are controlled as needed, using pump regulation so that a shortage is virtually impossible.

Stephan Heizungsbau put the CHPs into operation in December 2012, with the adsorption cooling units being added in May 2013. Andreas Stephan is extremely satisfied with the entire system: “Installation was smooth, and the initial data confirmed the system’s incredible effectiveness. Since we make full use of the waste heat from the CHPs, the entire system’s amortization period was reduced by a significant amount. I am confident that we will be seeing much more of this kind of CCHP system in the injection molding industry in the future. Our collaboration with InvenSor GmbH was extremely professional, and we will continue to expand this relationship.” Stephan expects the three CHPs to have an annual operating time of approximately 7,500 hours. In order to use the CCHP system in a new production hall as well, Andreas Stephan already installed a fourth CHP unit in November 2013 so that the company can also affordably generate its own electricity and heat here as well.

The InvenSor adsorption units are some of the most user-friendly on the market. For example, the target temperatures for cold water and the recirculation back into the driving cycle are extremely easy to set using the multilingual color-touch display. In addition, the unit is already set up for use in heat pump mode, which can be activated on the device. Using the hydraulic system already integrated into the unit, specialists and planners can implement their special solutions, such as the use of free cooling on cold days, without much increasing the entire system’s complexity and risk of malfunctions. The easy-to-operate start-up mode, automatic operating optimization, and the internet interface which is the included standard combine to make devices from InvenSor into plug-and-play devices that are easy to operate even without significant prior knowledge.