Considerations for the Design of Solar-Thermal Chemical Processes

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Janna Martinek ◽  
Melinda Channel ◽  
Allan Lewandowski ◽  
Alan W. Weimer
Keyword(s):  
Solar Energy ◽  
Water Splitting ◽  
Thermal Reduction ◽  
Absorption Efficiency ◽  
Chemical Processes ◽  
Solar Thermal ◽  
System Efficiency ◽  
Field Efficiency ◽  
Definition Of ◽  
Solar Field

A methodology is presented for the design of solar thermal chemical processes. The solar receiver efficiency for the high temperature step, defined herein as the ratio of the enthalpy change resulting from the process occurring in the receiver to the solar energy input, is limited by the solar energy absorption efficiency. When using this definition of receiver efficiency, both the optimal reactor temperature for a given solar concentration ratio and the solar concentration required to achieve a given temperature and efficiency shift to lower values than those dictated by the Carnot limitation on the system efficiency for the conversion of heat to work. Process and solar field design considerations were investigated for ZnO and NiFe2O4 “ferrite” spinel water splitting cycles with concentration ratios of roughly 2000, 4000, and 8000 suns to assess the implications of using reduced solar concentration. Solar field design and determination of field efficiency were accomplished using ray trace modeling of the optical components. Annual solar efficiency increased while heliostat area decreased with increasing concentration due to shading and blocking effects. The heliostat fields designed using system efficiency for the conversion of heat to work were found to be overdesigned by up to 21% compared with those designed using the receiver efficiency alone. Overall efficiencies of 13–20% were determined for a “ferrite” based water splitting process with thermal reduction conversions in the range of 35–100%.

Solar Field Efficiency and Electricity Generation Estimations for a Hybrid Solar Gas Turbine Project in France

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Pierre Garcia ◽  
Alain Ferriere ◽  
Gilles Flamant ◽  
Philippe Costerg ◽  
Robert Soler ◽  
...  
Keyword(s):  
Solar Energy ◽  
Combustion Chamber ◽  
Gas Turbine ◽  
Electricity Generation ◽  
Field Efficiency ◽  
Solar Receiver ◽  
Solar Field ◽  
External Combustion

The production of electricity with gas turbine and solar energy project aims to install at the Themis site (Targasonne, France) a prototype of hybrid solar/fossil gas-turbine system for electricity generation. The system features a 3800kWth pressurized air solar receiver combined with a fossil backup feeding a recuperated 1400kWe Turbomeca gas turbine with an external combustion chamber.

System and component modelling of a low temperature solar thermal energy conversion cycle

2013 ◽  
Vol 24 (4) ◽  
pp. 51-62
Author(s):  
Shadreck M. Situmbeko ◽  
Freddie L. Inambao
Keyword(s):  
Low Temperature ◽  
Solar Energy ◽  
Thermal Energy ◽  
Electrical Power ◽  
Solar Thermal ◽  
Working Fluid ◽  
Small Scale ◽  
Solar Thermal Energy ◽  
Solar Field ◽  
Conversion Technology

Solar thermal energy (STE) technology refers to the conversion of solar energy to readily usable energy forms. The most important component of a STE technology is the collectors; these absorb the shorter wavelength solar energy (400-700nm) and convert it into usable, longer wavelength (about 10 times as long) heat energy. Depending on the quality (temperature and intensity) of the resulting thermal energy, further conversions to other energy forms such as electrical power may follow. Currently some high temperature STE technologies for electricity production have attained technical maturity; technologies such as parabolic dish (commercially available), parabolic trough and power tower are only hindered by unfavourable market factors including high maintenance and operating costs. Low temperature STEs have so far been restricted to water and space heating; however, owing to their lower running costs and almost maintenance free operation, although operating at lower efficiencies, may hold a key to future wider usage of solar energy. Low temperature STE conversion technology typically uses flat plate and low concentrating collectors such as parabolic troughs to harness solar energy for conversion to mechanical and/or electrical energy. These collector systems are relatively cheaper, simpler in construction and easier to operate due to the absence of complex solar tracking equipment. Low temperature STEs operate within temperatures ranges below 300oC. This research work is geared towards developing feasible low temperature STE conversion technology for electrical power generation. Preliminary small-scale concept plants have been designed at 500Wp and 10KWp. Mathematical models of the plant systems have been developed and simulated on the EES (Engineering Equation Solver) platform. Fourteen candidate working fluids and three cycle configurations have been analysed with the models. The analyses included a logic model selector through which an optimal conversion cycle configuration and working fluid mix was established. This was followed by detailed plant component modelling; the detailed component model for the solar field was completed and was based on 2-dimensional segmented thermal network, heat transfer and thermo fluid dynamics analyses. Input data such as solar insolation, ambient temperature and wind speed were obtained from the national meteorology databases. Detailed models of the other cycle components are to follow in next stage of the research. This paper presents findings of the system and solar field component.

Analysis of Concentrating Solar Thermal System to Support Thermochemical Energy Storage or Solar Fuel Generation Processes

2019 ◽  
Author(s):  
Patrick Davenport ◽  
Janna Martinek ◽  
Zhiwen Ma
Keyword(s):  
High Temperature ◽  
Energy Storage ◽  
Solar Energy ◽  
Concentration Ratio ◽  
Operating Conditions ◽  
Solar Thermal ◽  
Superior Performance ◽  
Collection System ◽  
Thermochemical Process ◽  
Solar Field

Abstract A Concentrating solar thermal (CST) system integrated with a high-performance solar receiver can provide high-temperature process heat to drive thermochemical energy storage (TCES) or thermochemical fuel production processes with improved equilibrium conversion and fast reaction rates. An advantage of integrating a CST system with a thermochemical process is the ability to store chemical energy in large quantities for continuous downstream operations. However, a challenge in the effective conversion of solar energy to power or fuels is that high-temperature thermochemical process operating conditions require a high solar concentration ratio for efficient operation which imposes design difficulties for solar energy collection. Integration of the solar collection system with a thermochemical process affects the system efficiency and final product cost due to the relatively high solar field cost. Thus, optimization of the collection system provides a significant opportunity to reduce cost of solar thermochemical power or fuel. In this paper, we present a solar field layout strategy and assess the feasibility of a novel planar-cavity receiver to drive thermochemical processes with reaction temperatures in the range of 500–900°C. The complete solar collection system performance is examined and importance of conducting coupled field/receiver analyses is demonstrated by illustrating how improved spillage control by a modified heliostat aiming strategy impacts system radiative losses downstream. The planar-cavity receiver shows improved performance with increasing concentration ratio and superior performance over a flat plate receiver operating under the same prescribed operating conditions.

scholarly journals Optimizing Large-Scale Solar Field Efficiency: Latvia Case Study

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4171
Author(s):  
Ilze Polikarpova ◽  
Roberts Kakis ◽  
Ieva Pakere ◽  
Dagnija Blumberga
Keyword(s):  
Solar Energy ◽  
Influencing Factors ◽  
Heat Carrier ◽  
Thermal Energy ◽  
Solar Collector ◽  
Energy Production ◽  
Large Scale ◽  
District Heating ◽  
Field Efficiency ◽  
Solar Field

Solar energy transformation technologies are increasingly being used worldwide in the district heating sector. In the Baltic states, only one district heating company has implemented a large-scale solar collector field into its thermal energy production system, which is analyzed within this research. In this study, we analyzed the first year operation of the solar field, solar collector efficiency, and several influencing factors, i.e., ambient air temperature, heat carrier flow, and the temperature difference between the supply and return heat carrier temperatures. The study includes collecting and compilation of the data, analyzing influencing factors, and data analysis using the statistical analysis method. In addition, the research presents a simplified multi-regression model based on the actual performance of a large-scale solar field, which allows for forecasting the efficiency of solar collectors by taking into account the main operational parameters of the DH system. The results show that solar energy covers around 90% of the summer heat load of a particular district heating system. However, they also show room for improvements in producing all the necessary heat in the summer using solar energy. The regression analyses show that the most significant correlation between all parameters examined was obtained in May, reaching R2 = 0.9346 in solar field efficiency evaluation. This is due to several suitable conditions for solar energy production, i.e., placing solar collectors at an angle for them to be the most productive, having enough space in the storage tank, and the demand for thermal energy being still higher than in the summer months.

Effective Approaches for the Improvement of Solar Energy Collector Efficiency in Town Buildings

2012 ◽  
Vol 209-211 ◽  
pp. 1723-1726
Author(s):  
Yun Peng Zhang ◽  
Shun Xiang Sun ◽  
Yan Hou
Keyword(s):  
Solar Energy ◽  
Clean Energy ◽  
Building Energy ◽  
Absorption Efficiency ◽  
Solar Thermal ◽  
Thermal Arrest ◽  
Energy Usage ◽  
Solar Absorption ◽  
Collector Efficiency ◽  
Energy Shortage

In order to reasonably make good use of solar energy---a kind of typical and clean energy, especially increase the efficiency of solar energy usage in town buildings, this paper introduces and analyzes solar Thermal-arrest Technology by way of how to increase solar absorption efficiency and how to decrease collector heat loss, finds an effective way to increase the efficiency of present solar collectors. Solar Thermal-arrest Technology is good for being widely used in town buildings. Its reasonable development is helpful to reducing building energy consumption and the relief of present energy shortage in China.

Hydrogen Production by Solar Thermochemical Water-Splitting/Methane-Reforming Process

Solar Energy ◽  
2003 ◽  
Author(s):  
Tatsuya Kodama ◽  
Yoshiyasu Kondoh ◽  
Atsushi Kiyama ◽  
Ken-Ich Shimizu
Keyword(s):  
Hydrogen Production ◽  
Metal Oxide ◽  
Water Splitting ◽  
Thermal Energy ◽  
Experimental Studies ◽  
Reduction Process ◽  
Thermal Reduction ◽  
Solar Thermal ◽  
Solar Thermal Energy ◽  
Solar Thermochemical

Two different routes of solar thermochemical hydrogen production are reviewed. One is two-step water splitting cycle by using a metal-oxide redox pair. The first step is based on the thermal reduction of metal oxide, which is a highly endothermic process driven by concentrated solar thermal energy. The second step involves water decomposition with the thermally-reduced metal oxide. The first thermal reduction process requires very-high temperatures, which may be realized in sun-belt regions. Another hydrogen production route is solar reforming of natural gas (methane), which can convert methane to hydrogen via calorie-upgrading by using concentrated solar thermal energy. Solar reforming is currently the most advanced solar thermochemical process in sun belt. There is also possibility for the solar reforming to be applied for worldwide solar concentrating facilities where direct insolation is weaker than that in sun belt. Our experimental studies to improve the relevant catalytic technologies are shown and discussed.

Efficient Co-Harvesting of Solar Energy and Low-Grade Heat by Molecular Photoswitches for High Energy Density, Long-Term Stable Solar Thermal Battery

2019 ◽  
Author(s):  
Zhao-Yang Zhang ◽  
Tao LI
Keyword(s):  
Energy Density ◽  
Solar Energy ◽  
High Performance ◽  
High Energy ◽  
Solar Thermal ◽  
High Energy Density ◽  
Low Grade ◽  
Thermal Battery ◽  
Low Grade Heat

Solar energy and ambient heat are two inexhaustible energy sources for addressing the global challenge of energy and sustainability. Solar thermal battery based on molecular switches that can store solar energy and release it as heat has recently attracted great interest, but its development is severely limited by both low energy density and short storage stability. On the other hand, the efficient recovery and upgrading of low-grade heat, especially that of the ambient heat, has been a great challenge. Here we report that solar energy and ambient heat can be simultaneously harvested and stored, which is enabled by room-temperature photochemical crystal-to-liquid transitions of small-molecule photoswitches. The two forms of energy are released together to produce high-temperature heat during the reverse photochemical phase change. This strategy, combined with molecular design, provides high energy density of 320-370 J/g and long-term storage stability (half-life of about 3 months). On this basis, we fabricate high-performance, flexible film devices of solar thermal battery, which can be readily recharged at room temperature with good cycling ability, show fast rate of heat release, and produce high-temperature heat that is >20<sup> o</sup>C higher than the ambient temperature. Our work opens up a new avenue to harvest ambient heat, and demonstrate a feasible strategy to develop high-performance solar thermal battery.

Efficient Co-Harvesting of Solar Energy and Low-Grade Heat by Molecular Photoswitches for High Energy Density, Long-Term Stable Solar Thermal Battery

2019 ◽  
Author(s):  
Zhao-Yang Zhang ◽  
Tao LI
Keyword(s):  
Energy Density ◽  
Solar Energy ◽  
High Performance ◽  
High Energy ◽  
Solar Thermal ◽  
High Energy Density ◽  
Low Grade ◽  
Thermal Battery ◽  
Low Grade Heat

Solar energy and ambient heat are two inexhaustible energy sources for addressing the global challenge of energy and sustainability. Solar thermal battery based on molecular switches that can store solar energy and release it as heat has recently attracted great interest, but its development is severely limited by both low energy density and short storage stability. On the other hand, the efficient recovery and upgrading of low-grade heat, especially that of the ambient heat, has been a great challenge. Here we report that solar energy and ambient heat can be simultaneously harvested and stored, which is enabled by room-temperature photochemical crystal-to-liquid transitions of small-molecule photoswitches. The two forms of energy are released together to produce high-temperature heat during the reverse photochemical phase change. This strategy, combined with molecular design, provides high energy density of 320-370 J/g and long-term storage stability (half-life of about 3 months). On this basis, we fabricate high-performance, flexible film devices of solar thermal battery, which can be readily recharged at room temperature with good cycling ability, show fast rate of heat release, and produce high-temperature heat that is >20<sup> o</sup>C higher than the ambient temperature. Our work opens up a new avenue to harvest ambient heat, and demonstrate a feasible strategy to develop high-performance solar thermal battery.

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