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- Soliman, Hady R., et al.
(författare)
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Utilizing Industrial Waste Heat for Power Generation Using sCO2 Cycles
- 2021
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Ingår i: Proceedings of the 4th European sCO2 Conference 2021, sCO2 2021. - : DuEPublico - Duisburg-Essen Publications Online. ; , s. 322-332
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Konferensbidrag (refereegranskat)abstract
- The industrial sector accounts for approximately 30% of the global total energy consumption and 50% of that is lost as waste heat. Recovering waste heat from industries and utilizing it as an energy source is a sustainable way of generating electricity. Supercritical CO2 (sCO2) cycles can be used with various heat sources including waste heat. Current literature primarily focuses on the cycle’s thermodynamic performance without investigating the economics of the system. This is mainly due to the lack of reliable cost estimates for the cycle components. Recently developed cost scaling makes it possible to perform more accurate techno-economic studies on these systems. This work aims to model waste-heat-to-power systems and by performing sensitivity analysis on various system components, attempts to determine which factors require the most attention to bring this technology into commercialization. The industries with the largest unutilized waste heat are cement, iron and steel, aluminum and gas compressor stations. In this work, models of different sCO2 cycle configurations were developed and simulated for these industries. The techno-economic model optimizes for the highest Net Present Value (NPV) using an Artificial Bee Colony algorithm. The optimization variables are the pressure levels, split ratios, recuperator effectiveness, condenser temperature and the turbine inlet temperature limited by the heat source. The results show industries can cut down costs by 8-34M using this system. Furthermore, the system can achieve an LCOE between 2.5-4.5 c/kWh which is competitive with ORC (3.2-18 c/kWh) and steam cycles (3-9 c/kWh). Out of the modeled industries, waste heat recovery in the steel industry yields the highest NPV of 34.6M.
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| 2. |
- Trevisan, Silvia, et al.
(författare)
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Coatings utilization to modify the effective properties of high temperature packed bed thermal energy storage
- 2021
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Ingår i: Applied Thermal Engineering. - : Elsevier. - 1359-4311 .- 1873-5606. ; 185
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Tidskriftsartikel (refereegranskat)abstract
- High-temperature thermal energy storage is becoming more and more important as a key component in concentrating solar power systems and as an economically viable large-scale energy storage solution. Ceramics and natural rocks based packed beds are one of the attracting solutions. For application temperatures above 600 ◦C, radiation heat transfer becomes the dominant heat transfer phenomenon and it greatly influences the performance of thermal storage systems. Coatings with different thermal properties (mainly thermal emissivity and thermal conductivity) could be exploited to modify the effective thermal properties of packed beds. In this work, we present a methodology to account for the thermal effect of a coating layer applied over the pebbles of a packed bed. The influences on the packed bed effective thermal conductivity of several characteristics of the coating material, packed bed arrangement, and filler material are investigated. The results show that low emissivity coatings could reduce the effective thermal conductivity of a rock based packed bed of about 58%, with respect to a similar uncoated solution, already at 800 ◦C. A low emissivity coating could also limit the increase in the thermal effective conductivity from the cold to the hot zone of the storage. Coatings would have a higher influence when applied in packed beds with large size particles, relatively high thermal conductivity of the substrate and void fraction. The application of different coatings, with various thermo-physical properties, in different parts of the storage could modify the effective thermal conductivity distribution and enable a partial control of the thermocline degradation, increasing the storage thermal efficiency.
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| 3. |
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| 4. |
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| 5. |
- Trevisan, Silvia, et al.
(författare)
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Packed bed thermal energy storage: A novel design methodology including quasi-dynamic boundary conditions and techno-economic optimization
- 2021
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Ingår i: Journal of Energy Storage. - : Elsevier BV. - 2352-152X .- 2352-1538.
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Tidskriftsartikel (refereegranskat)abstract
- High temperature thermal energy storages are becoming more and more important as a key component in concentrating solar power plants. Packed bed storages represent an economically viable large scale energy storage solution. The present work deals with the analysis and optimization of a packed bed thermal energy storage. The influence of quasi-dynamic boundary conditions on the storage thermodynamic performance is evaluated. The Levelized Cost of Storage is innovatively applied to thermal energy storage design. A complete methodology to design packed bed thermal energy storage is proposed. In doing so, a comprehensive multi-objective optimization of an industrial scale packed bed is performed. The results show that quasi-dynamic boundary conditions lead to a reduction of around 5% of the storage thermal efficiency. Contrarily, the effect of the investigated design variables over the TES LCoS optimization is only slightly influenced by quasi-dynamic boundary conditions. Aspect ratio between 0.75 and 0.9 would maximize the storage thermal efficiency, while low preliminary efficiency around 0.47 would minimize the Levelized Cost of Storage. This work testifies that quasi-dynamic boundary conditions should be taken into considerations when optimizing thermal energy storage. The Levelized Cost of Storage could be also considered as a more reliable performance indicator for packed bed thermal energy storage, as it is less dependent on variable boundary conditions.
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| 6. |
- Wang, Wujun, 1984-, et al.
(författare)
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A dual-flow choked nozzle based precise pressure controller for high-temperature gas systems
- 2021
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Ingår i: Measurement. - : Elsevier BV. - 0263-2241 .- 1873-412X. ; 184
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Tidskriftsartikel (refereegranskat)abstract
- A novel dual-flow choked nozzle based pressure controller is developed to achieve high-precision pressure control. The primary air flow is mainly used for offering the required mass flow to the test section, and the secondary air flow is used for regulating the total mass flow through the choked nozzle to achieve required pressure levels. The test results show that the precision of the stabilization of the pressure can reach +/- 0.005 bar for cold-state environments with air flow at ambient temperature, and +/- 0.015 bar for hot-state environments with air flow temperature in the range of 797.1-931.5 degrees C. Besides, this pressure controller has fast response. A new pressure steady state can be reached within 23.1 s for air flow at ambient temperature and 70 s for hightemperature scenario. Since no moving component exposed to the high-temperature air flow, it is very suitable for the pressurized test rigs with extremely high-temperature gas flow.
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| 7. |
- Wang, Wujun, 1984-, et al.
(författare)
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Solar selective reflector materials: Another option for enhancing the efficiency of the high-temperature solar receivers/reactors
- 2021
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248. ; 224
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Tidskriftsartikel (refereegranskat)abstract
- The cavity wall is an important part of a cavity receiver in determining the receiver efficiency. Using solar selective reflector (SSR) materials with low solar absorptivity and high thermal emissivity for the cavity wall design is one efficient way to improve the receiver efficiency. In this work, we present a systematic study of the optical and high-temperature stability performances of six different SSR materials: one refractory ceramic fiber-based substrate material (Fiberfrax 140) and five metallic oxide coatings which are prepared by mixing metallic oxide powders of alumina, magnesium oxide and titanium dioxide with commercial inorganic adhesives. The thermal stability was studied by heating up and keeping the six candidate materials in atmospheric conditions at a temperature of 1250 ◦C for 200 h. The spectrum of hemispherical reflectance in the spectrum band 0.25–25 μmwas measured for analyzing the optical performance of the candidate materials. The obtained results show that all the six materials studied have good solar selective reflection characteristics, i.e, low solar absorptivity and relatively high thermal emissivity. Especially, the alumina-coated substrate material shows excellent performances both for thermal stability and solar selective reflection. The solar reflectivity can reach 94.6%.
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