(187c) Modeling and Designing Renewable Energy Systems in Rural Areas with Flexible Operating Units

Designing energy systems with flexible inputs is increasingly important because distributed and renewable energy production forms an increasing fraction of the energy supply (Marsden, 2011; Tabassum, Kashem and Mathew, 2018). Distributed energy systems are thought to be less prone wide-spread service interruptions, and renewable energy production tends to be intermittent. For these reasons, distributed energy systems have quite different challenges compared to centralized ones, and novel design and modeling methods are in demand and have been proposed. We present a new approach to this problem focused on the structure of the system itself which not always considered in adequate detail.

In addition, the growing public interest in making energy generation more sustainable (Kutscher, Milford and Kreith, 2018) has created a rising interest in the use of renewable energy sources like wood, grass, manure, etc. Because these energy sources depend on agriculture, they are making necessary the design of energy systems able to manage flexible inputs. In addition, because these sources are low value commodities, their transportation for long distances is impractical. Sustainability, however, has a social and economic component consistent which makes the revitalization of local and regional economies also a priority. This is important because it creates stakeholder with a vested interest in sustainable energy generation.

Previous work applied the P-graph methodology to design the structure for an energy system based on biomass in rural conditions (Vance et al., 2015) typical for central Europe. But flexible inputs to the energy generation process where not explicitly considered. A more recent extension of the P-graph framework makes it possible to have flexible inputs to a production process, and this also makes the use of more accurate equipment models possible (Éles, Heckl and Cabezas, 2020). This flexibility is important because as already mentioned, the availability of the sources of renewable energy, e.g. biomass, is not steady but variable with seasons, weather, and other conditions. Hence, in this work a method based on the aforementioned extension of the P-graph methodology is proposed to design the structure of a renewable energy system in a rural area. The study uses the data collected for the region around Bad Cell in Upper Austria, Europe. Then the notion of flexible operating units is applied to the new case study, giving us the possibility of identifying optimal composition of biomass feeds and energy plant sizing given the particular geography of the region. Our model includes the collection and transportation of local renewable resources, fermenters and combined heat and power (CHP) plants, and the operation of all of these is optimize for profit from generated heat and electricity. This is again important because it has the potential of creating local stakeholders with a vested interest in the success of renewable energy generation.

The results of this work highlight the importance of thoroughly considering the effect of system structure in the design and optimization of renewable energy systems. They also offer some concrete examples where profitable energy generation systems can be established and operated in a central European setting. Future work will include a more careful consideration of system dynamics and more detailed analysis of the environmental sustainability of such processes.

References

• Éles, A., Heckl, I. and Cabezas, H., 2020. Modeling technique in the P-Graph framework for operating units with flexible input ratios. Central European Journal of Operations Research, pp.1-27.
• Kutscher, C.F., Milford, J.B. and Kreith, F., 2018. Principles of sustainable energy systems. CRC Press, Boca Raton, Florida, USA.
• Marsden, J., 2011, April. Distributed generation systems: A new paradigm for sustainable energy. In 2011 IEEE Green Technologies Conference (IEEE-Green) (pp. 1-4). IEEE.
• Tabassum M., Kashem S.B.A., Mathew K. (2018) Distributed Energy Generation—Is It the Way of the Future?. In: Garg A., Bhoi A., Sanjeevikumar P., Kamani K. (eds) Advances in Power Systems and Energy Management. Lecture Notes in Electrical Engineering, vol 436. Springer, Singapore. https://doi.org/10.1007/978-981-10-4394-9_61
• Vance, L., Heckl, I., Bertok, B., Cabezas, H. and Friedler, F., 2015. Designing sustainable energy supply chains by the P-graph method for minimal cost, environmental burden, energy resources input. Journal of Cleaner Production, 94, pp.144-154.