| 1. |
- Aichmayer, Lukas, et al.
(författare)
-
Experimental Flux Measurement of a High-Flux Solar Simulator using a Lambertian Target and a Thermopile Flux Sensor
- 2016
-
Ingår i: AIP Conference Proceedings 1734. - : American Institute of Physics (AIP). - 9780735413863
-
Konferensbidrag (refereegranskat)abstract
- A measurement system for the experimental determination of the flux distribution at the focal plane of the KTH high-flux solar simulator was designed and implemented. It is based on a water-cooled Lambertian target and a thermopile flux sensor placed close to the focal point of the solar simulator. Correction factors to account for systematic effects were determined and an uncertainty analysis was performed. The measurement system was successfully used to evaluate the flux distribution of a single lamp/lens-arrangement with a peak flux of 675kW/m².
|
|
| 2. |
- Garrido Galvez, Jorge, 1990-, et al.
(författare)
-
A Detailed Radiation Heat Transfer Study of a Dish-Stirling Receiver : the Impact of Cavity Wall Radiation Properties and Cavity Shapes
- 2015
-
Ingår i: SOLARPACES 2015: INTERNATIONAL CONFERENCE ON CONCENTRATING SOLAR POWER AND CHEMICAL ENERGY SYSTEMS. - : American Institute of Physics (AIP). - 9780735413863
-
Konferensbidrag (refereegranskat)abstract
- A detailed 3-D radiation analysis of a dish-Stirling cavity receiver is carried out to estimate the cavity steady-state temperatures in order to assess the receiver integrity, lifetime and efficiency performance. For this purpose, a parabolic dish was modeled with 5.2 m focal length, 8.84 m aperture diameter and 2.1 mrad typical surface error. Three generic cavity shapes (cylindrical, diamond-shaped and reverse-conical) with three different emissivities (0.2, 0.4 and 0.7) are studied. Worst-case scenario heat generations (total absorbed radiation), maximum steady-state temperatures and energy balances of the cavities are calculated to evaluate the receiver performance. The results show that reverse-conical cavities can significantly reduce cavity wall peak temperatures (by 40-120 K), improve the temperature evenness and decrease the radiation losses by 4-5%. Regarding radiation properties, low reflectivities present lower steady-state temperatures even for low/moderate direct solar fluxes. Due to the lower temperatures, lower total thermal losses are also expected.
|
|
| 3. |
- Guedez, Rafael, et al.
(författare)
-
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
- 2016
-
Ingår i: SOLARPACES 2015. - : Author(s). - 9780735413863
-
Konferensbidrag (refereegranskat)abstract
- 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.
|
|
| 4. |
- Guedez, Rafael, et al.
(författare)
-
Techno-economic Performance Evaluation of Solar Tower Plants with Integrated Multi-layered PCM Thermocline Thermal Energy Storage - A Comparative Study to Conventional Two-tank Storage Systems
- 2016
-
Ingår i: SOLARPACES 2015. - : American Institute of Physics (AIP). - 9780735413863
-
Konferensbidrag (refereegranskat)abstract
- Solar Tower Power Plants with thermal energy storage are a promising technology for dispatchable renewable energy in the near future. Storage integration makes possible to shift the electricity production to more profitable peak hours. Usually two tanks are used to store cold and hot fluids, but this means both higher investment costs and difficulties during the operation of the variable volume tanks. Instead, another solution can be a single tank thermocline storage in a multi-layered configuration. In such tank both latent and sensible fillers are employed to decrease the related cost up to 30% and maintain high efficiencies. This paper analyses a multi-layered solid PCM storage tank concept for solar tower applications, and describes a comprehensive methodology to determine under which market structures such devices can outperform the more conventional two tank storage systems. A detail model of the tank has been developed and introduced in an existing techno-economic tool developed by the authors (DYESOPT). The results show that under current cost estimates and technical limitations the multi-layered solid PCM storage concept is a better solution when peaking operating strategies are desired, as it is the case for the two-tier South African tariff scheme.
|
|
| 5. |
- Topel, Monika, et al.
(författare)
-
Thermo-Economic Study on the Implementation of Steam Turbine Concepts for Flexible Operation on a Direct Steam Generation Solar Tower Power Plant
- 2016
-
Ingår i: SOLARPACES 2015. - : American Institute of Physics (AIP). - 9780735413863
-
Konferensbidrag (refereegranskat)abstract
- Among concentrating solar power technologies, direct steam generation solar tower power plants represent a promising option. These systems eliminate the usage of heat transfer fluids allowing for the power block to be run at greater operating temperatures and therefore further increasing the thermal efficiency of the power cycle. On the other hand, the current state of the art of these systems does not comprise thermal energy storage as there are no currently available and techno-economically feasible storage integration options. This situation makes direct steam generation configurations even more susceptible to the already existing variability of operating conditions due to the fluctuation of the solar supply. In the interest of improving the annual performance and competitiveness of direct steam generation solar tower systems, the present study examines the influence of implementing two flexibility enhancing concepts which control the steam flow to the turbine as a function of the incoming solar irradiation. The proposed concepts were implemented in a reference plant model previously developed by the authors. Then, a multi-objective optimization was carried out in order to understand which configurations of the steam turbine concepts yield reductions of the levelized cost of electricity at a lower investment costs when compared to the reference model. Results show that the implementation of the proposed strategies can enhance the thermo-economic performance of direct steam generation systems by yielding a reduction of up to 9.2% on the levelized cost of electricity, mainly due to allowing 20% increase in the capacity factor, while increasing the investment costs by 7.8%.
|
|
