Solar cooling for production processes

■ Location: Lustenau in Vorarlberg, Austria

■ Solar cooling using an absorption cooling machine

■ Gross collector area: 550 m2

■ Brought into operation: 10/2011

KRAL AG is one of the internationally leading and most innovative manufacturers of screw pumps and flow meters. Since its foundation in 1950 the family business has earned itself an excellent reputation in this sector.

The production work of KRAL AG uses over 50 CNC lathes, milling machines and grinding machines. The energy needed for the cooling of all the heat loads comes to around 320 MWh per year, and in future this energy will be generated by a thermally operated cooling system. Approximately one third of the required heat energy will be produced by a large-scale solar thermal system. The waste heat of several air compressors will also be used and supplied to the cooling machine, while the remaining heat needs will be met by an oil boiler.

120 evacuated tube collectors, of the types CPC 45 and CPC 30, form a collector field of approximately 550 m2 on the roof of the production hall. The solar thermal system works constantly with a minimum temperature of 90 °C in order to power the absorption refrigerator (150 kW). In the winter months the solar yield is used for heating. It is anticipated that 80 to 85% of the solar heat will be used for cooling, with the remainder used for heating.

Overall the solar thermal system is expected to give a yearly yield of around 212 MWh, which corresponds to an annual yield of 420 kWh/m2 of aperture. For the intended operational temperatures this is an exceptionally high yield, which only highly efficient tube collectors can achieve.

Without the solar thermal system, KRAL would require around 28,000L of additional oil per year (corresponding to 75% of the yearly consumption of the boiler system). Due to this the environment would be faced with an annual increase in CO2 emissions of 87 tonnes (310g CO2 per kWh of oil).