Model cogeneration – efficiency in Germany
An advanced system at a company in southern Germany provides process cooling and power generation for plastic injection moulding machines with adsorption chillers and micro cogeneration units.
For the past year the TRANSpofix Company has benefited from a 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 specialising in the manufacture of state-of-the-art transport systems and the corresponding plastic and aluminium 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, and Andreas Stephan, junior manager of Stephan Heizungsbau, agreed on a combination of three SenerTec Dachs CHP units and three adsorption cooling units from Berlin-based InvenSor.
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 moulding machines used to manufacture parts. The waste heat generated is then channelled 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.
The three LTC 10 plus (Low Temperature Chiller) adsorption units operate at TRANSpofix with a combined cooling capacity of 24 kilowatts. As such, they not only cool the injection moulding machines, but during the summer also cool the company’s entire office space of 900 square metres. 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.
The cooling energy produced is channelled to the production floor in the form of water and used there to cool the moulded 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 amortisation of the entire CCHP system in only five years – which is an extremely short period of time for major industrial systems.
A 3500-litre 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 2000-litre 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.
“Installation was smooth, and the initial data confirmed the system’s incredible effectiveness,” says Heizungsbau. “Since we make full use of the waste heat from the CHPs, the entire system’s amortisation 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 moulding industry in the future.”
Heizungsbau says he expects the three CHPs to have an annual operating time of approximately 7500 hours.
In order to use the CCHP system in a new production hall as well, he installed a fourth CHP unit in November 2013 so that the company can also affordably generate its own electricity and heat here too.
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 colour-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 optimisation, 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.