Keywords: optimization, sustainability, geothermal utilization, reservoir modeling, hybrid methods, heuristic and metaheuristic methods, discrete approximation, analytical solution.

Natural geothermal energy has generally been classified as a renewable energy source since it recharges at a similar timescale as production from the resource. Aggressive production can lead to situations where further production is not economically viable because without costly human intervention the renewable energy source is unable to renew itself on a human timescale. The goal of our work is to develop a decision supporting system (DSS) to optimize the net present value (NPV) of the revenue from low temperature geothermal systems with respect to operation and expansion costs and environmental-economical factors. The DSS is based on the concepts of Sigurðardottir et al. [1]. The behavior of the geothermal reservoir plays a major part in any analysis of future cost and operational optimization of geothermal systems. Therefore it is necessary to use a sufficiently accurate but computationally efficient model to simulate this behavior. In this study, the reservoir model is based on a lumped parameter description. The new numerical approach presented here exploits the symbolic computation facilities of Mathematica 8.0 to generate analytical solutions in parametric forms. To describe the future for a given planning horizon a probabilistic-possibilistic approach was applied. To solve the optimization problem a hybrid meta-heuristic ANGEL developed by Csébfalvi and Csébfalvi [2] was used. In this paper, we only deal with the potential methodological problems connected to this new long-range, highly uncertain (more or less fuzzy) and challenging optimization problem. The key element of the new DSS approach, namely the lumped parameter model (LPM) handling is illustrated by an "academic" example.

1

S. Sigurðardottir, H. Palsson, A. Valfells, H. Stefansson, "Optimizing Revenue of a Geothermal System with Respect to Operation and Expansion", In Proceedings World Geothermal Congress 2010, Bali, Indonesia, 25-29 April, 2010.

2

A. Csébfalvi, G. Csébfalvi, "ANGEL meta-heuristic method for truss optimization", In Proceedings of the 7th World Congress of Structural and Multidisciplinary Optimization (WCSMO-7), COEX, Seoul, Korea, 21-25 May, 2007.

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