University of Twente Student Theses
Can state-of-the-art numerical modeling result in a more efficient and economic design of power plants?
Both, Annet (2016) Can state-of-the-art numerical modeling result in a more efficient and economic design of power plants?
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| Abstract: | In coastal regions, some power plants use ambient water for cooling, which increases the temper- ature of the water used. The behavior of the outfall plume has an indirect effect on the capital and operational cost of a power plant. The design of a power plant configurations is most often based on computer model predictions. Currently, separate models are available for the near field and far field, which are both dependent on the input values and assumptions made by the mod- eler. This makes it difficult for non-expert clients to judge the quality of the model outcomes. This study objectively investigated the added value of state-of-the-art recirculation modeling compared to a typical straightforward modeling approach for the optimization of the intake and outfall configuration of a power plant. Because of the wide range of variation in the above stated problem, the problem was assessed using a case study. This case was carefully chosen in order to capture the most important and relevant parameters such as the residual current, wind, ambient temperatures and a nearby river discharge. Two models were set up, the first using a straightforward model approach (Approach A) and the second using state-of-the-art model approaches (Approach B). The aim of Approach A is to estimate the intake and outfall configuration with a quick and simple assessment. This was done by selecting a common consultancy practice model, a 3D far field model. The ambient conditions were selected based on common weather conditions. Approach B included state-of- the-art model approaches in order to assess the problems processes more physically correctly. This was achieved extending Approach A with a dynamically coupled near-far field model and selecting the ambient conditions with the SBAM-method. In order to assure an objective design process, a design framework was set up beforehand, which included 18 predefined designs and fixed criteria to select the 'best' option. Based on the two models, two offshore intake and outfall configuration designs were proposed. The value of the two Approaches was evaluated base on offshore capital costs and recirculation costs. In this case study, Approach A highly overestimated the temperature in the near field for all diffuser designs. Due to this, designs were rejected by our design framework that were found suitable in Approach B. The proposed design by Approach A will be located further into the sea resulting in a longer outfall pipeline. This results in an additional $1.035 million capital costs for the Approach A based design compared to the Approach B based design, an increase of 23%. Furthermore, additional maintenance can be tens of thousands of dollars per year and the operational costs will also be larger for a design with a longer pipeline system. For all investigated designs, the yearly averaged intake temperature assessed by Approach A was within 30% of the assessed intake temperatures of Approach B. In terms of recirculation costs, this amounts to a difference of $300.000 in the lifetime of the power plant. In conclusion, this case study helps to clarify that cases exist where an added-value for a state- of-the-art modeling approach can be found. In terms of capital costs, a state-of-the-art approach based design is expected to have smaller capital costs because suitable designs are rejected by the straightforward approach which are not rejected by a state-of-the-art model. This study also suggested, that the recirculation costs computed by a straightforward based model are overly optimistic, in case of a diffuser design. This could result in unforeseen costs for the operator. Finally, the results obtained from this case study suggest that a state-of-the-art approach has limit added value when designing an open surface outfall but it is expected to be more when less advantageously scenarios are selected in the straightforward approach. Finally, the model results of a state-of-the-art based model approach are less sensitive to the models input and thus expected to be more reliable. |
| Item Type: | Essay (Master) |
| Faculty: | ET: Engineering Technology |
| Subject: | 56 civil engineering |
| Programme: | Civil Engineering and Management MSc (60026) |
| Link to this item: | https://purl.utwente.nl/essays/70581 |
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