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Innovative combined heat, cold and power (Trigeneration) at Offenburg University of Applied Sciences
(2013)
The aim of the paper was to investigate the energy saved in the shift from separate generation of thermal and electrical energy to trigeneration at the energy facility in Offenburg University of Applied Sciences (HS OG). The energy facility at HS OG used a traditional heating system and electricity from grid until 2007 afterwhich they installed a trigeneration system to meet its continuously changing dynamic thermal and electrical demands. This paper highlights the methodology that had been derived to analyze and study the effect of this shift based on the energy consumption data available from 2004 to 2011, which were scarce due to the limited monitoring. From the energy analysis, we concluded that 8 % primary energy was saved in this shift at the energy facility of HS OG. And from economical perspective 5 % useful thermal energy and 39 % useful electrical energy was saved in this shift at the energy facility of HS OG. Nevertheless, the term energy saving, in general, is very relative and complex to define in such a changeover.
The energy supply of Offenburg University of Applied Sciences (HS OG) was changed from separate generation to trigeneration in 2007/2008. Trigeneration was installed for supplying heat, cooling and electrical power at HS OG. In this paper, trigeneration process and its modes of operation along with the layout of the energy facility at HS OG were described. Special emphasis was given to the operation schemes and control strategies of the operation modes: winter mode, transition mode and summer mode. The components used in the energy facility were also outlined. Monitoring and data analysis of the energy system was carried out after the commissioning of trigeneration in the period from 2008 to 2011. Thus, valuable performance data was obtained.
Micro gas turbines (MGTs) are regarded as combined heat and power (CHP) units which offer high fuel utilization and low emissions. They are applied in decentralized energy neration.
To facilitate the planning process of energy systems, namely in the context of the increasing application of optimization techniques, there is a need for easy-to-parametrize component models with sufficient accuracy which allow a fast computation. In this paper, a model is proposed where the non-linear part load characteristics of the MGT are linearized by means of physical insight of the working principles of turbomachinery. Further, it is shown that the model can be parametrized by the data usually available in spec sheets. With this model a uniform description of MGTs from several manufacturers
covering an electrical power range from 30kW to 333kW can be obtained. The MGT model was
implemented by means of Modelica/Dymola. The resulting MGT system model, comprising further heat exchangers and hydraulic components, was validated using the experimental data of a 65kW MGT from a trigeneration energy system.
Polygeneration systems are a key technology for the reduction of primary energy usage and emissions. High costs, lack of flexibility and effort for parameterization hinder the wide usage of modeling tools during their conceptual design. This paper describes how planning tools can be structured for the conceptual design phase where only little information is available to the planner. A library concept was developed using the principles of object-oriented modeling to address the flexibility issue. With respect to cost and expandability, the open-source modeling language Modelica was chosen. Furthermore, easy-to-parameterize component models were developed. In addition to the improved library concept and novel component models, an easy-to-adapt control concept is proposed. The component models were validated and the applicability of the library was demonstrated by means of an example. It was shown that the data usually obtained from spec sheets are sufficient to parameterize the models. In addition to this, the control concept was approved.
The aim of this research work was to develop a boiler model with few parameters required for energy planning. The showcase considered for this work was the boiler system of the energy center at Offenburg University of Applied Sciences. A grey box model of the boiler was developed systematically starting from model abstraction, simplification, model break-down and to the use of empirical correlations wherever necessary to describe the intermediate effects along with the use of information from manufacturer’s specification in order to reduce parameters. This strategy had resulted in a boiler model with only 6 parameters, namely, nominal burner capacity, water gallery capacity, air ratio, heat capacity of wall, thermal conductance on flue gas and hot water side. Most of these parameters can be obtained through the information available in the spec sheets and thus an energy planner will be able to parameterize the model with low effort. The model was validated with the monitored data of the showcase. It was tested for the start-up, shut-down behavior and the effect of storage.