Upper Styrian Dairy (Austria)
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Obersteirische Molkerei Knittelfeld (Austria)
(Upper-Styrian dairy in Knittelfeld)
- 1. Solar integration
A solar plant has not yet been built. The first step was, to examine possible strategies for energy efficiency and to evaluate the application of solar technology for supplying process-heat in terms regarding technology and economics.
- 2. Industry Sector
- 3. Industrial application
Process-water heating and integration in a central warm-water store
- 4. Process description
- Process flowsheet:
Fig: Flowsheet of the “Upper-Styrian dairy in Knittelfeld”
Processes with thermal energy demand
- 5. Energy flows and temperature ranges
- Main heat supply system and fuel:
- Gas consumption: 228,3 Nm³/month
- 339,57 Nm³/h
- Gas consumption for the processes: 2.771.514 Nm³/month
- Gas consumption for heating: 196.644 Nm³/month
- Energy consumption (Sankey):
Fig: Energy-balance of the dairy
- Temperature ranges and other parameters:
The steam energy which is produced in the boiler, is needed for whey-concentration (38%, 9.100 MWh/a), for heating the boiler-feed water up to 102°C (11%, 2.700 kWh) and for the remaining thermal processes (29%, 6.900 MWh/a), whereof the milk-cheese pre-heating and the heating prior to the whey-concentration are the biggest energy consumers. The reflux-condensate contains 2,5 % of the energy. Heating consumes 8% of the total energy (1.900 MWh/a). 25 % (!) of the energy (5.900 MWh/a) cannot be clearly related to any process. Of this value, the basic demand requires 4.800 MWh/a and 1.100 MWh/a have to be used for balance-adjustment in the process.
- 6. Solar Thermal Plant
6.1 Solar process-water heating
- 6.1.1 Process scheme and description
In total, 65 m³/day of process-water (fresh-water) at 65 °C are needed in the milk- and the cheese-dairy. The fresh water has a temperature of 12°C. Because there is no continuous process-water demand, a storage-tank is necessary, but the hot water can be taken directly from the store. The heat-storage-medium is heated in the collector and heats the fresh-water, which is then gathered in the store, via a simple heat-exchanger.
There is only one heat-exchanger necessary to integrate the solar system, therefore the heat-transfer losses sink and the efficiency of the solar energy rises. The final temperature of the water after the solar system was defined as 55°C. The heating up to 65 °C is done via after-heating. Two solar plants with different solar ratios were simulated.
- 6.1.2 Performance of the planned solar plant
Over the whole year, an energy input of 470 MWh/a with 1000 m² collector area and 584 MWh/a with 1500 m² area can be achieved.
6.2 Integration of the solar system in a central warm-water store
- 6.2.1 Process scheme and description
In this option, the process water shall be heated up to the required temperature of 65°C only by means of the solar system. In this case, the integration of the solar plant into a holistic storage-system would make sense. In the dairy, there are also the boiler-feed water and the “Bruchwaschwasser” (break-washing-water?), which can both be pre-heated to 45°C via heat exchangers with final temperatures of 102 and 65°C. By the integration of solar heat into a central store, all three streams “process-water”, “boiler-feed water” and “Bruchwaschwasser” can be heated. The practical application could be done with a single big “Schichtspeicher” (store), into which the waste-heat for the heat exchangers at 38 and 50°C and the solar energy at higher temperatures can be inserted.
- 6.2.2 Performance of the planned solar plant
The decline of the specific collector-output is clearly visible. Thus the economics of the collector area also decrease. Based on the present state of knowledge, the direct solar process-water heating is preferable to the integration in a central store!
- Pictures of the built solar system:
No information available.
- 7. Energy savings
- Pinch analysis results:
Calculated heat-exchanger network:
The following thermal energy demand has to be supplied additionally:
- Energy savings:
Energy savings with option A (1000 m²): 469.600 kWh/a Cost savings option A: 20.780 €/a
Energy savings with option B (1500 m²): 583.100 kWh/a Cost savings option B: 25.802 €/a
- 8. Economic evaluation
- Economic parameters of the built solar system:
Solar process-water heating:
LITERATURE: AEE INTEC/JOANNEUM RESEARCH (“Styrian Promise”)
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