Enhancing the Profitability of Solar Tower Power Plants through Thermoeconomic Analysis Based on Multi-objective Optimization

AbstractSolar tower power plants with integrated thermal energy storage units represent one of the most promising technologies for enhancing the economic viability of concentrating solar power in the short term. Tower systems allow higher concentration ratios to be achieved, which in turn means higher fluid operating temperatures and thus higher power cycle efficiencies. Moreover, the integration of storage allows power production to be shifted from times where there is low demand to periods where electricity prices are higher, potentially enhancing the profitability of the plantdespite representing an additional upfront cost.The variable nature of the solar resource and the myriad potential roles that storage can assume, together with the complexity of enhancing the synergies between the three blocks: the solar field, the storage block and power block, make the design of these power plants a challenging process. This paper introduces a comprehensive methodology for designing solar tower power plants based on a thermoeconomic approach that allows the true optimum trade-off curves between cost, profitability and investment to be identified while simultaneously considering several operating strategies as well as varying critical design parameters in each of the aforementioned blocks.The methodology is presented by means of analyzing the design of a power plant for the region of Seville. For this location, results show that similar profits, measured in terms of the internal rate of return, can be achieved from different power plant configurations in terms of sizing and operating strategy, each associated to different investments. In particular, optimum configurations found corresponded tolarger power blocks with medium-to-large solar field and storage blocksthat allow the plants to operate continuously throughout the day and be shut down during midnight. Moreover, it isshown that for a fixed power block size it can also be economically interesting to consider smaller storage unitsand adopt instead a peaking strategy, as this can still be profitable whilst representing a lower investment, thus lower risk

La microcirugía como técnica para disminuir incapacidades

El reimplante de un miembro o de un dedo y la transferencia de tejido simple o compuesto ya no es un hecho fantasioso en nuestra época.To reimplant an extremity or a finger or to transfer simple or complex tissue is no longer a fantasy in our times

Techno-economic performance evaluation of direct steam generation solar tower plants with thermal energy storage systems based on high-temperature concrete and encapsulated phase change materials

Nowadays, direct steam generation concentrated solar tower plants suffer from the absence of a cost-effective thermal energy storage integration. In this study, the prefeasibility of a combined sensible and latent thermal energy storage configuration has been performed from thermodynamic and economic standpoints as a potential storage option. The main advantage of such concept with respect to only sensible or only latent choices is related to the possibility to minimize the thermal losses during system charge and discharge processes by reducing the temperature and pressure drops occurring all along the heat transfer process. Thermodynamic models, heat transfer models, plant integration and control strategies for both a pressurized tank filled with sphere-encapsulated salts and high temperature concrete storage blocks were developed within KTH in-house tool DYESOPT for power plant performance modeling. Once implemented, cross-validated and integrated the new storage model in an existing DYESOPT power plant layout, a sensitivity analysis with regards of storage, solar field and power block sizes was performed to determine the potential impact of integrating the proposed concept. Even for a storage cost figure of 50 USD/kWh, it was found that the integration of the proposed storage configuration can enhance the performance of the power plants by augmenting its availability and reducing its levelized cost of electricity. As expected, it was also found that the benefits are greater for the cases of smaller power block sizes. Specifically, for a power block of 80 MWe a reduction in levelized electricity costs of 8% was estimated together with an increase in capacity factor by 30%, whereas for a power block of 126 MWe the benefits found were a 1.5% cost reduction and 16% availability increase

Trypanosoma cruzi infection induces up-regulation of cardiac muscarinic acetylcholine receptors in vivo and in vitro

The pathogenesis of chagasic cardiomyopathy is not completely understood, but it has been correlated with parasympathetic denervation (neurogenic theory) and inflammatory activity (immunogenic theory) that could affect heart muscarinic acetylcholine receptor (mAChR) expression. In order to further understand whether neurogenic and/or immunogenic alterations are related to changes in mAChR expression, we studied two models of Trypanosoma cruzi infection: 1) in 3-week-old male Sprague Dawley rats chronically infected with T. cruzi and 2) isolated primary cardiomyocytes co-cultured with T. cruzi and peripheral blood mononuclear cells (PBMC). Using [³H]-quinuclidinylbenzilate ([³H]-QNB) binding assays, we evaluated mAChR expression in homogenates from selected cardiac regions, PBMC, and cultured cardiomyocytes. We also determined in vitro protein expression and pro-inflammatory cytokine expression in serum and cell culture medium by ELISA. Our results showed that: 1) mAChR were significantly (P < 0.05) up-regulated in right ventricular myocardium (means ± SEM; control: 58.69 ± 5.54, N = 29; Chagas: 72.29 ± 5.79 fmol/mg, N = 34) and PBMC (control: 12.88 ± 2.45, N = 18; Chagas: 20.22 ± 1.82 fmol/mg, N = 19), as well as in cardiomyocyte transmembranes cultured with either PBMC/T. cruzi co-cultures (control: 24.33 ± 3.83; Chagas: 43.62 ± 5.08 fmol/mg, N = 7 for both) or their conditioned medium (control: 37.84 ± 3.84, N = 4; Chagas: 54.38 ± 6.28 fmol/mg, N = 20); 2) [³H]-leucine uptake was increased in cardiomyocytes co-cultured with PBMC/T. cruzi-conditioned medium (Chagas: 21,030 ± 2321; control 10,940 ± 2385 dpm, N = 7 for both; P < 0.05); 3) plasma IL-6 was increased in chagasic rats, IL-1&#946;, was increased in both plasma of chagasic rats and in the culture medium, and TNF-&#945; level was decreased in the culture medium. In conclusion, our results suggest that cytokines are involved in the up-regulation of mAChR in chronic Chagas disease