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Solar Heat Integration Network

Final Report Summary - SHINE (Solar Heat Integration Network)

The “Solar Heat Integration Network” SHINE is an international PhD network on Solar Thermal Engineering, with a focus on “Solar District Heating”, “Solar Heat for Industrial Processes”, and “Sorption Processes and Materials”.
The ITN project was coordinated by the Institute of Thermal Engineering at Kassel University, Germany. 13 PhD students were hosted by six universities and five private sector partners from all over Europe (DE, SE, DK, ES, CH, AT). The project launched in autumn 2013 offered six specialized and structured PhD courses on solar thermal engineering.

Research Objectives
The focus of the SHINE-project was on large solar heating systems and new applications as well as new storage technologies and materials, specifically sorption processes. The project covered detailed experimental work on materials, components and systems, as well as system integration analysis, numerical modelling and optimization. Chemical investigations on sorption materials were carried out.

a) Solar District Heating
The three main objectives of work in the field of solar district heating were:
- to optimize complex hydraulic configurations and strategies,
- to analyze advantages and disadvantages of centralized and decentralized solar fields, and
- to develop design and operating strategies for solar heating and cooling district heating systems.
Six PhD projects have contributed to achieving these objectives. They elaborated a wide variety of models and tools for district heating systems. Among others, a general tool to model complex hydraulic networks was developed and calibrated, used for scientific investigations. Its accuracy was verified with an individual collector and for a collector field. Moreover, models for flow distribution in collectors and collector fields were validated for a solar collector field in Denmark. They were used to analyze collector field design and operating strategies, resulting in new suggestions for improved control.
Additionally, SHINE researchers developed new models for the design tool Polysun. The tool is widely used in practical applications by engineering offices and trade. The accuracy of the models for district heating networks was verified by inter-comparison with the research tool TRNSYS and against measurements for the Vallda Heberg solar block heating system in Sweden. The tool was then used for a case study on large scale collector fields in the final SHINE PhD course.
Another outcome of the project is a techno-economic analysis of the Vallda Heberg system that has both centralized and decentralized collector fields. The analysis shows that the use of a novel distribution piping system leads to significant reduction in heat losses and better cost-effectiveness.
Furthermore, SHINE researchers developed forecast models to optimize operational strategies to use available thermal storage for a specific solar district heating and cooling system in Mallorca, ES.
An innovative approach to realize cost-efficient large solar heating systems are drain-back systems. SHINE researchers developed and calibrated a model for drain-back solar collectors, as well as new operational strategies for an existing plant.
Another key outcome of the SHINE project was the development of a new methodology for calculating the cost of solar thermal heat. The methodology was developed within the expert group of the International Energy Agency IEA SHC Task 54, with significant contributions by SHINE PhD students.

b) Solar Heat for Industrial Processes
The main goal in the field of industrial processes was to facilitate the integration of solar thermal technologies. The main objectives followed by the three PhD students from “Solar Heat for Industrial Processes” were:
- to reduce the large planning efforts requiring specific expert knowledge to integrate solar heat into existing heating systems for industrial processes,
- to develop parabolic trough solar collectors that can provide operation temperatures of up to 250°C used for industrial processes, and
- to develop a methodology for the quick assessment and comparison of process heat collectors.
For this purpose, several existing and running industrial solar process heat systems were studied throughout the project and the developed simulation models were validated with data from the existing systems.
In order to support the development of better and cheaper solar thermal collectors for high temperatures required by the industry, optical simulations were developed and an existing open-source ray-tracing program was improved. Different simulations and parameter studies were carried out in order to compare solar thermal technologies, and also other low carbon heat sources such as heat pumps and direct resistance heating with photovoltaics. These tools allow a better comparison among different collectors suitable for industrial process heat.
Through the research performed in the field, clear pathways are being developed to encourage a rapid adoption of using solar heat for industrial applications. The developed simulations tools are providing solutions not only for the collector and system optimization, but lower the planning effort, costs and risks associated with solar thermal projects.

c) Sorption Processes and Materials
Focus of a third work package of the SHINE project was on solid and liquid sorption materials as well as sorption processes. One of the objectives was to reach a higher energy density compared to sensible water storage and to prove a seasonal thermal storage concept with high solar fraction. Moreover, the SHINE PhD students investigated various adsorption and absorption processes with numerical and experimental means to attain a better understanding of the heat and mass transfer processes and to increase the performance of the processes, for example, by surface modifications or the use of new sorption materials.
Two of the individual SHINE projects focused on the adsorption/desorption processes of water steam on zeolites. Closed adsorption cycles were set up in laboratories for different applications. Experimental investigations showed a promising performance of the processes. The identified challenges are particularly related to the evaporation process and to the high desorption temperatures of around 200°C. New guidelines for the construction of efficient evaporators have been developed through detailed investigations of evaporation processes. Novel numerical models were developed and used to predict long term system performance.
Moreover, a test rig was mounted to investigate the influence of non-ionic additives on the transport phenomena of an absorber with a horizontal tube bundle. A vacuum cell enabled measurements of the surface tension of different liquids with various surfactants at reduced pressure in a saturated atmosphere, thus representing the real operating condition of the absorber. Additional investigations were carried out on chemical modifications and combination of fluid solid hybrid materials. Commercially available materials (zeolites) were analyzed and novel Metal-Organic Frameworks (MOFs) were synthesized within the SHINE project. The heat of sorption and adsorption isotherms were measured and implemented in numerical models in close cooperation between the partners.

www.solar.uni-kassel.de/solnet