Solar Thermal Steam Research Articles

A Solar Thermal Steam Propulsion System Using Disassociated Steam for Interplanetary Exploration

Sustainable space exploration will require using off-world resources for propellant generation. Using off-world-generated propellants significantly increases future missions’ range and payload capacity. Near Earth Objects (NEOs) contain a range of available resources, most notably water-ice and hydrated minerals. However, water-bearing regolith needs to be excavated and the water extracted. Water is a compelling choice for fuel as it is readily available in interplanetary space and easily stored. In this paper, we propose using solar concentrators, which can efficiently convert incident sunlight into heat without the need for moving parts. When water is heated up to 4000 K, a value consistent with high-performance refractive materials, it experiences significant disassociation into H2, O2, OH, H, and O components, providing a path for adding considerable additional chemical energy per degree of temperature increase, and producing theoretical specific impulse (Isp) values in the range of 643 s to 659 s.

A Simulation Study of Solar Thermal Steam Generation for Thermal Recovery of Thick Oil Based on Aspen Plus

High-temperature steam injection is a common means of thermal recovery of thick oil. Although the steam injection boiler currently used for thick oil injection can achieve fast start-stop control, the power consumption of the pump is large, and the boiler control is demanding. Besides, a large amount of fossil fuel is needed to supply the heat required for steam heating. Using solar thermal to realize the transformation of solar energy-molten salt heat energy-steam energy can effectively reduce the burning of fossil fuels and realize clean thermal recovery of thick oil. To ensure the actual demand of thermal recovery of thick oil, it is necessary to determine a reasonable steam evaporation volume and vapor phase fraction. This paper simulates a solar thermal heat exchange system for molten salt-steam based on Aspen Plus. The simulation results show that the heat load and required solar panel area of all heat exchangers rise when the evaporation volume increases. However, the superheater grows most slowly. When the vapor phase fraction at the evaporator outlet rises to 1, there is no phase change heat transfer in the superheater, and its heat load plummets to 230 kW.

Laser-treated wood for high-efficiency solar thermal steam generation.

Solar-driven water vaporization is considered one of the most sustainable ways to solve water scarcity. The design of highly efficient solar absorber systems has received extensive attention. Here, we report a novel light absorption material for water evaporation using laser-treated wood. The obtained laser-treated wood possesses interconnected 3D porous networks formed by the random construction of carbon arrays and a hydrophilic surface due to the oxygen implantation by laser treatment. When under 1 sun solar-simulated light irradiation (1 kW m−2), the surface temperatures of dry and water-saturated wood reach 59.5 °C and 40.4 °C, respectively, indicating good heat localization. As a result, the laser-treated wood under 1 sun illumination shows high solar to vapor efficiencies of 93.1% and 92.6% for pure water and seawater, respectively, which are higher than that of most wood-based reported photo-thermal conversion materials. Therefore, the fabricated laser-treated wood may pave the way for harvesting solar energy to produce clean water at low cost.

Feasibility study on solar thermal process heat in the beverage industry

Solar energy provides a minor percentage of the thermal demand of industrial processes globally. This paper proposes a new analytical energy model for the simulation of a solar thermal steam boiler system to be integrated into an industrial environment with steam parameters at 180 °C. The purposes of this study were to evaluate the influence of solar irradiation on the share of solar steam generation and to clarify how the levelised costs of energy are influenced by different technical and economic parameters. A solar steam boiler system with parabolic trough collectors is modelled and simulations for two scenarios of 1.5 and 2.0 MW thermal output at annual irradiation of 919 kWh/(m2a) were carried out. According to the results of the feasibility study a solar share of 17–23 % of total annual steam generation is feasible without the integration of a thermal storage. Levelised costs of solar steam generation of 55–60 EUR/MWh were determined under current market conditions at mid-latitude regions. The proposed concept can benefit the wider integration of solar process heat. Beyond a solution for the production process, the integration into a connected district heating network offers further potential to reduce its primary energy factor.

Super-Absorbers by Randomly Distributed Titanium Spheres

Electromagnetic wave absorbers have been widely investigated in these years. Nevertheless, the structural models were mainly based on the metal-insulator-metal metamaterials. In this work, we show a study on the achievement of ultra-broadband perfect absorption via a randomly distributed titanium spheres in the hydrogel layer. In the visible and near-infrared range ( $0.38-2.0\,\,\mu \text{m}$ ), the spectral average absorption reaches 93.6%. Taking the absorption efficiency above 90% into account, the bandwidth of the spectral window is 1386 nm. Moreover, the maximal absorption is even up to 98.9% in this open structure since there is no metal reflector back. In particular, these impressive absorption properties can be well maintained under complex electromagnetic surroundings, indicating the insensitive response to the polarization and incident angles. The particle plasmons and the near-field coupling effects for the adjacent spheres in-plane and out-of-plane are the main contributions for the ultra-broadband absorption. The absorption properties together with the simple structural characteristics including the flexible hydrogel layer will hold wide applications in the solar energy related technologies such as the solar thermal steam generation, desalination, macula-removing, and biological sterilization.

Concentrated Solar Thermal Steam Cooking System: An Application in DTU Hostel

Feasibility study of Concentrated Solar Thermal Steam Cooking System has performed for climatic conditions of Delhi by taking the case of DTU boys hotel mess to replace LPG cooking system. Energy requirement for mass cooking in DTU mess is calculated to be 288981 KWh which till now is fulfilled by 15 LPG cylinders each of capacity of 14kg. An attempt is made to fulfill this requirement with solar energy using Scheffler Dish, although it is also known that complete energy requirement cannot be fulfilled due to unavailability of solar radiations at night, in monsoon and sometimes in winter. Almost 50% of energy requirement i.e.143880 KWh can meet by this system using 25 Scheffler Dish of 16m2. Calculations for CO2 emission due to burning of LPG in DTU hostel mess is also done which comes out to be 189 tonne and it is shown that with implementation of such a cooking system almost 50% of CO2 emission can be controlled. Effect of DNI, optical efficiency and temperature difference of feed water and steam is shown in this work. Cost of this project that is bear by DTU is around 62 lakhs with payback period of 2.84 years. This system has proposed with keeping in mind that it could prove a model to encourage other institutions in Delhi for implementing this technology for mass and collective cooking.

Solid Oxide Steam Electrolysis with Integration of Solar Heat

The experimental coupling of a commercial high-temperature steam electrolyzer and a solar thermal steam generator has been realized for the first time at the German Aerospace Center (DLR). A high flux solar simulator and a solar steam receiver were used to generate superheated steam which was fed to a commercial 12-cell electrolyzer stack from an industrial supplier (SolidPower, Mezzolombardo, Italy). After optimization of the operating parameters of the different system components the system could be operated properly at 770 °C and a steam flow of 12.0 slpm (standard litres per minute), 0.58 kg/h respectively. The open circuit voltage (OCV) of the stack was 10.4 V. Approximately 8.4 slpm hydrogen was produced at a current density of -1.25 A/cm2 and a voltage of approximately 17 V corresponding to a steam conversion rate of 70%. The electrical efficiency of the electrolyzer was 93% related to the lower heating value. The experimental setup of the prototype system is presented and results with regard to solar steam generation and electrochemical performance of the electrolyzer are reported.

SMALL HELIOSTATS CSP SYSTEMS ON LONG-SPAN HANGING ROOFS

ABSTRACT Building Integrated Concentrating Solar Power (BI-CSP) schematic studies with small scale exterior two-axis tracking heliostats anchored on and semi-shading long span hanging roofs with elevated receiver(s) are presented for populated urban and rural locations. Hanging roofs (inverted shallow dome shape) with two-way structural cables and mostly square infill prefabricated slabs/panels supported from a perimeter horizontal circular donut shape rim-girder-platform without a center tension ring studies are for comparing to radial cable structural configurations with a center tension ring. Cable gap grouting between slabs/panels form a pre-tensioned inverted shell structure after temporary weights are removed. Securing vertical heliostat posts studies include: three vertical bolts cast in grout gap two-way cables intersections for three point adjustment of horizontal post base plates; and one-axis adjustable manufactured post brackets bolted to sloped roof surfaces at holes cast in the gaps/slabs. A main case study schematic is around a 30m/100ft diameter hanging roof with a 0.07 sag/diameter ratio with around 271 1m2 heliostats for 230kWt solar thermal steam or air to around 300degC/572degF building integrated thermal energy storage (molten salt, firebricks, etc.) and applications (water purification, cooling, industrial process heat, etc.). A BI-CSP hanging roofs R&D project proposal is outlined: with a circular roof study diameter range of around 25m/82ft–200m/656ft diameter for comparing two-way and radial cable structural configurations for distributed steam stations and a wide range of application temperatures.

Techno economic design of a solid oxide electrolysis system with solar thermal steam supply and thermal energy storage for the generation of renewable hydrogen

The dependency of renewable energy systems on environmental influences such as sun or wind availability is one of the greatest challenges in the energy transition. For this purpose, it is important to develop electro chemical storage systems for long-term storing of renewable electricity in the form of hydrogen or methane. In the presented work, an electrolysis system with solid-oxide electrolyser stacks is designed. A solar thermal receiver is used to produce the steam supplied to the electrolyser stacks. On the other hand, a thermal energy storage, using a phase change material, is used for the extension of the operational hours during the night time. The system is optimized to minimize the levelized costs of hydrogen and compared to a system without a thermal energy storage. Finally, the cost sensitivity for the four main components of the cost structure is evaluated and discussed.

Functionalized Graphene Enables Highly Efficient Solar Thermal Steam Generation.

The ability to efficiently utilize solar thermal energy to enable liquid-to-vapor phase transition has great technological implications for a wide variety of applications, such as water treatment and chemical fractionation. Here, we demonstrate that functionalizing graphene using hydrophilic groups can greatly enhance the solar thermal steam generation efficiency. Our results show that specially functionalized graphene can improve the overall solar-to-vapor efficiency from 38% to 48% at one sun conditions compared to chemically reduced graphene oxide. Our experiments show that such an improvement is a surface effect mainly attributed to the more hydrophilic feature of functionalized graphene, which influences the water meniscus profile at the vapor-liquid interface due to capillary effect. This will lead to thinner water films close to the three-phase contact line, where the water surface temperature is higher since the resistance of thinner water film is smaller, leading to more efficient evaporation. This strategy of functionalizing graphene to make it more hydrophilic can be potentially integrated with the existing macroscopic heat isolation strategies to further improve the overall solar-to-vapor conversion efficiency.

Martensitic transformation in an intergranular corrosion area of austenitic stainless steel during thermal cycling

An oxidation-assisted martensitic phase transformation was observed in an austenitic stainless steel after thermal cycling up to 970°C in air in a solar thermal steam reformer. The intergranular corrosion areas were investigated by electron backscatter diffraction (EBSD), transmission Kikuchi diffraction (TKD) and transmission electron microscopy (TEM). The structural-and-chemical maps revealed that within intergranular corrosion areas this martensitic transformation primarily occurs in oxidation-induced chromium-depleted zones, rather than due to only sensitization. This displacive transformation may also play a significant role in the rate at which intergranular corrosion takes place.

Solar-generated steam for oil recovery: Reservoir simulation, economic analysis, and life cycle assessment

The viability of solar thermal steam generation for thermal enhanced oil recovery (TEOR) in heavy-oil sands was evaluated using San Joaquin Valley, CA data. The effectiveness of solar TEOR was quantified through reservoir simulation, economic analysis, and life-cycle assessment. Reservoir simulations with continuous but variable rate steam injection were compared with a base-case Tulare Sand steamflood project. For equivalent average injection rates, comparable breakthrough times and recovery factors of 65% of the original oil in place were predicted, in agreement with simulations in the literature. Daily cyclic fluctuations in steam injection rate do not greatly impact recovery. Oil production rates do, however, show seasonal variation. Economic viability was established using historical prices and injection/production volumes from the Kern River oil field. For comparison, this model assumes that present day steam generation technologies were implemented at TEOR startup in 1980. All natural gas cogeneration and 100% solar fraction scenarios had the largest and nearly equal net present values (NPV) of $12.54 B and $12.55 B, respectively. Solar fraction refers to the steam provided by solar steam generation. Given its large capital cost, the 100% solar case shows the greatest sensitivity to discount rate and no sensitivity to natural gas price. Because there are very little emissions associated with day-to-day operations from the solar thermal system, life-cycle emissions are significantly lower than conventional systems even when the embodied energy of the structure is considered. We estimate that less than 1g of CO2/MJ of refined gasoline results from the TEOR stage of production if solar energy provides all steam. By this assessment, solar thermal or supplemental solar generation systems appear to be a preferred alternative to fully conventional systems using natural gas in areas with large solar insolation.

Thermodynamic analyses of solar thermal gasification of coal for hybrid solar-fossil power and fuel production

Thermodynamic analyses are performed for solar thermal steam and dry gasification of coal. The selected types of coal are anthracite, bituminous, lignite and peat. Two model conversion paths are considered for each combination of the gasifying agent and the coal type: production of the synthesis gas with its subsequent use in a combined cycle power plant to generate power, and production of the synthesis gas with its subsequent use to produce gasoline via the Fischer–Tropsch synthesis. Replacement of a coal-fired 35% efficient Rankine cycle power plant and a combustion-based integrated gasification combined cycle power plant by a solar-based integrated gasification combined cycle power plant leads to the reduction in specific carbon dioxide emissions by at least 47% and 27%, respectively. Replacement of a conventional gasoline production process via coal gasification and a subsequent Fischer–Tropsch synthesis with gasoline production via solar thermal coal gasification with a subsequent Fischer–Tropsch synthesis leads to the reduction in specific carbon dioxide emissions by at least 39%.

The ANU solar thermal steam engine: performance analysis

This paper describes the results of a series of experiments that were performed to define the performance of the uniflow piston-operated valve steam engine developed by the Australian National University (ANU) for solar thermal applications. The results are fitted by least-squares regression to simple power series expressions that correlate the power output and engine inlet pressure to steam temperature, thermal power input and condenser pressure. The performance of the engine is examined by comparison with an idealized frictionless and quasi-static model. The idealized model is used to assess the relative importance of the effects of friction and non equilibrium thermodynamic conditions in the engine. The exergetic performance of the ideal engine is examined to demonstrate the fundamental limitations of this engine technology. It is concluded that high piston/cylinder forces during the first stages of expansion pose a significant barrier to the enhancement of engine efficiency through the use of higher temperatures and expansion ratios. © 1998 John Wiley & Sons, Ltd.

The ANU solar thermal steam engine: performance analysis

This paper describes the results of a series of experiments that were performed to define the performance of the uniflow piston-operated valve steam engine developed by the Australian National University (ANU) for solar thermal applications. The results are fitted by least-squares regression to simple power series expressions that correlate the power output and engine inlet pressure to steam temperature, thermal power input and condenser pressure. The performance of the engine is examined by comparison with an idealized frictionless and quasi-static model. The idealized model is used to assess the relative importance of the effects of friction and non equilibrium thermodynamic conditions in the engine. The exergetic performance of the ideal engine is examined to demonstrate the fundamental limitations of this engine technology. It is concluded that high piston/cylinder forces during the first stages of expansion pose a significant barrier to the enhancement of engine efficiency through the use of higher temperatures and expansion ratios. © 1998 John Wiley & Sons, Ltd.