Integration methods for solar heat into industrial production processes
In many developed countries, even in moderate climates, the use of solar energy in thermal plants offers a CO2 free alternative to other energy supplies. The aim of this project was the development of a method for optimized integration of solar heat in industrial/commercial processes which are run in batch operation.
In industrial applications however, solar energy will in most cases only be able to supply one part of the necessary energy demand due to several external factors, and the question how and when this energy can be integrated into the process takes by far more consideration and planning than with conventional heat supply systems. Prior to investigations about the integration of solar energy all other energetically, financially and organisationally sensible possibilities should be utilized. For the analysis of the existing processes the Pinch-method can be applied.
The following steps, which are described in further detail in the report in the discussion of the three case studies, have to be taken to analyse the ideal integration of solar thermal plants in existing heat supply systems:
- Systematic compilation of energy streams
- Calculation of the minimal theoretical heat- and cooling demand
- Determination of the heat demand, that can be efficiently supplied by solar thermal heat
- Design of a heat exchanger network
- Design of the solar thermal plant
- Economical evaluation
The Pinch method enables statements of the theoretical minimal energy demand for heating and cooling and the maximal possible internal heat recovery. It also gives information at which energy levels and to what extent energy for cooling and heating has to be supplied.
The integration of solar thermal energy in industrial processes has to be done across the Pinch. The Pinch method here provides information at which temperature ranges the integration is most efficient. From the case studies of this project followed that a development of a common Pinch- and simulation programme is not necessary. In fact further research has to focus rather on the further development of the Pinch programme for the application at low temperature processes and the link to additional functions (e.g. cost functions). In the area of solar simulation the programming of a tool designed for industrial applications is necessary for further calculations.
In the design of the heat exchanger network for existing plants the user will always consider present pipelines, the positioning of buildings, existing plant components etc. and will have to chose the economical best option out of the remaining alternatives. The theoretical minimal demand for heating and cooling will therefore not be able to be reached in practical applications.
The investigation of the three case studies showed that by a systematic analysis of the thermal heat demand in most cases a high savings potential can be identified. Combined with the integration of solar energy a promising alternative proposal could be elaborated for all companies.
DI Christoph Brunner und Univ. Prof. DI Dr. Hans Schnitzer
JOANNEUM RESEARCH Forschungsgesellschaft mbH
Institut für Nachhaltige Techniken und Systeme- JOINTS
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TU- Graz, Institut für Ressourcenschonende und Nachhaltige Systeme (Werkvertragspartner)
AEE INTEC - Institut für nachhaltige Technologien (Werkvertragspartner)