Superhydrophilic MoS2@Polypyrrole hydrogel with dual photothermal-water activation properties for synergistic solar steam generation

Integrated solar thermal steam generation and heavy-oil recovery projects have garnered interest because of their ability to decrease the variability of steam generation costs arising from fluctuations in natural gas prices as well as life-cycle carbon dioxide emissions. The viability of a solar thermal steam generation system (with and without natural gas back-up) for thermal enhanced oil recovery (TEOR) in heavy-oil sands was evaluated in this study. Using the San Joaquin Valley as a case study, the effectiveness of solar TEOR was quantified through reservoir simulation, economic analysis, and life-cycle assessment of oil-recovery operations. Reservoir simulation runs with continuous but variable rate steam injection were compared with a base-case Tulare Sand steamflood project. Reservoir properties and well geometries were drawn from the literature. 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 for this reservoir setting. Oil production rates for a system without natural gas back-up to moderate injection rates do, however, show seasonal variation. Economic viability was established using a discounted cash flow model incorporating historical prices and injection/production volumes from the Kern River oil field. This model assumes that present day steam generation technologies could be implemented fully at TEOR startup for Kern River in 1980, for the sake of comparison against conventional steam generators and cogenerators. 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, with production data from 1984 to 2011. 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 it is independent of natural gas. Because there are very little emissions associated with day-to-day operations from the solar thermal system, life-cycle emissions for the solar thermal system are significantly lower than conventional systems even when the embodied energy of the structure is considered. Here, we estimate that less than 1 g of CO2/MJ of refined gasoline results from the TEOR stage of production if solar energy provides all steam. By this assessment, solar thermal based or supplemented steam generation systems for TEOR appear to be a preferred alternative, or supplement, to fully conventional systems using natural gas (or higher carbon content fuels), especially in areas with large solar insolation.

Enhanced direct steam generation via a bio-inspired solar heating method using carbon nanotube films

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

Energy, exergy and economic (3E) analysis of integrated solar direct steam generation combined cycle power plant

Sustainable and low-cost cellulose aerogel-based absorber for solar steam generation

Synergistic Tandem Solar Electricity-Water Generators

High performance carbonized corncob-based 3D solar vapor steam generator enhanced by environmental energy

The use of solar thermal steam generation for heavy-oil recovery has the advantage of reducing carbon dioxide emissions, as well as offsets the cost variability of steam generation due to fluctuations in natural gas prices. Daily cyclic fluctuations in steam injection rate associated with sunlight hours, along with hydrocarbon production and heating/cooling of rock cause changes to reservoir stress. This paper focuses on the dilation and compaction behaviors associated with continuous but variable-rate solar generated steam injection. Our approach integrates geomechanical models with the reservoir simulation model. The challenge with integrating geomechanics with reservoir models is to find accurate and sufficient data for stress field and orientation, dilation and compaction pressures, and the fracture pressure for the formation. We evaluate the viability of a solar thermal steam generation system with natural gas back-up for thermal enhanced oil recovery (TEOR) in heavy-oil sands that includes geomechanical coupling with the reservoir. Coupled reservoir-geomechanical simulation runs with continuous variable steam injection were compared with the base-case uncoupled Tulare Sand steamflood project. Sensitivity analyses for dilation parameters were studied to understand their effects on the overall oil recovery and breakthrough times. Significant pore pressure variation to trigger compaction was not observed for reasonable day-time injection rates of up to 1000 BBL cold-water equivalent (CWE)/d in high permeability formations. The injection pressures were maintained much below the fracture pressure of the formation in all cases. To summarize, a solar thermal steam generation approach for thermal enhanced oil recovery is a promising technique for supplementing steam generation in areas with large solar insolation.

Solar steam generation has drawn high levels of attention from the research community in recent years due to its wide application and abundantly available energy source—sunlight. To the best of the author's knowledge, a specialized overview of photothermal semiconductor solar steam generation has not been conducted to date. In this review, the recently reported solar evaporators using metal oxide semiconductors as the photoabsorber material are investigated, from the perspective of nanostructure, synthesis method, and installation method. A timeline sequence map is generated with the CiteSpace analysis tool to visualize the trend of metal oxide semiconductors as photoabsorbers. The nanostructure of metal oxide semiconductor is emphasized, due to its significant effect on regulating photothermal efficiency in solar steam generation. In addition, other considerations are suggested to enable a fair evaluation of future synthesized photoabsorbers, including cost, stability, reproducibility, recyclability, and regenerative ability. A brief summary of divergent application of solar steam generation is conducted to show the merits of solar steam generation, as well to provide insights for production of photoabsorbers targeted to varying usage and scenarios. Furthermore, the challenges and opportunities of metal oxide solar steam generation system are elaborated from the viewpoint of the authors, with the aim to provide useful insights for future development of photothermal solar steam generation.

Concentrating solar thermal technologies are drawing more attention since it can substantially contribute to a carbon-neutral society. The solar receivers are essential in this technology to convert solar energy efficiently into thermal energy. Moreover, high-temperature steam generation is the promising application for concentrated solar power plants or industirial processes. Therefore, the direct solar steam generator has been gaining more attention due to its advantages of low operation and maintenance costs. Most solar steam generator designs consist of a tube with helical configuration because of its high heat exchange performance and compactness. However, only few studies address solar steam generators with conical helical tubes. Thus, both experimental and simulation data of this design are scarce. This paper shows the successful development and experimental testing of a solar steam generator with a conical helical tube. The experimental results proved that the developed solar steam generator can produce high-temperature steam of 600 °C at an inlet pressure and mass flow rate of 150–200 kPa and 2.5 kg/h, respectively. The overall calculated energy efficiency (thermal and optical efficiency) was 60–62%. In addition, a coupled 1D-3D numerical model was implemented to analyze the solar steam generator’s performance. The model consists of a 3D cavity heat transfer model and a 1D two-phase fluid flow model. The numerical analysis demonstrated the ideal generator’s performance (energy efficiency of 68–69%) and the great impact of convection in the heat losses (50% of the total energy losses). Although more research of the convection is required, the presented results provide a basis for designing further, upscaled solar steam generators employing conical helical tubes.

SummarySolar steam generation has proven to be a sustainable method to handle water shortage. Various materials for solar steam generation have been introduced in the past few years. However, the utilization of tedious and complicated synthesis to generate a photoactive layer is a matter of concern in the fabrication solar steam generation devices. Thus, improved methods toward cost‐effectiveness by exploring economical materials with simple manufacturing process are urgently and essentially needed. In this study, we first report on manufacturing hybrid membranes using commercially accessible materials, that is, cellulose paper and pencil graphite. The proposed method is to trace and coat a cellulose paper directly with a pencil without the use of solvents and chemicals, and it is possible to create an ecofriendly photoactive layer without a complicated process. The formed pencil graphite‐traced membranes were successfully utilized in solar steam generation and showed excellent steam generation rate of 4.32 kg/m2h which is almost 3.5 times more than that of pristine membrane at solar intensity of 3 Sun. The developed method could be widely utilized in the field of solar steam generation, since it is very facile and simple, and can be integrated to other commonly used materials for solar steam generation such as fabric and wood. In addition, on‐site production is possible, so it has a potential to be utilized in remote and resource‐limited areas for steam generation.

This paper reports on the start-up of Phase 1 of a Solar Steam Generation facility (SSG) and its export to the existing steam headers of the Amal oil field, located in the south of Oman. Significant considerations within the SSG are reviewed and the impacts on the client's systems identified and discussed. Operational performance indicators on SSG and Client facilities are studied, primarily based on process operating data and equipment stability records, to ensure that the supply of variable steam from solar generation does not create any detrimental effects on the existing facilities. Of particular interest is to assess the success of a variable rate steam injection mode and the impact this has on Client facilities: system pressures, conventional steam generator operation, and wellhead steam injection rates. Previous simulation work has demonstrated that this mode of operation is essentially equivalent to fixed steaming rates provided the same daily equivalent of steam is injected in both cases. However, this has never been demonstrated in the field for extended periods. Operational data showed that, as anticipated, the Client's systems were able to accomodate the cyclic swings in header pressure and the induced variable flows through their fixed, manual chokes. Data showed that the Client's conventional steam generators (HRSGs) continued to operate as normal without noted issue. The changing pressure in the Client's steam header propagated back to the solar steam generation facility which was able to easily manage its operations automatically, causing no disruptions to its operations. No safety-related incidents arose, and all processes were well-managed on-site. This study demonstrates for the first time the performance of large-scale solar steam generation facilities operating alongside conventional steam generation and distribution systems with the two disparate systems seamlessly integrated. It also demonstrates that variable rate steaming has practical application within this field. This highly dynamic process has been sympathetically and successfully added to an existing large, steady-state operation without introducing significant issues to either system.

Improving steam generation and distilled water production by volumetric solar heating

Solar steam generation with low-cost and excellent energy efficiency is of great significance for alleviating an energy crisis, reducing water pollution and promoting seawater desalination. However, there are still numerous challenges for solar steam generation system to practical energy utilization. In this review, based on our previous research, we summarize various methods of solar steam generation, photothermal conversion mechanism and efficiency. We studied a series of effecting factors for solar steam generation. Our systematic investigation provided a clearer understanding of how to design and optimize the photothermal conversion system to improve the steam generation rate and energy conversion rate, including improving light absorption, reducing heat loss, and optimizing water supply. This article aims to make a comprehensive review of present solar steam technology, so that people can better apply photothermal conversion technology. Meanwhile, it also provides a route for the selection of photothermal materials, the design and optimization of the photothermal conversion system.

The integrated solar plant concept was initially proposed by Luz Solar International [1] as a means of integrating a parabolic trough solar plant with modern combined cycle power plants. An integrated plant consists of a conventional combined cycle plant, a solar collector field, and a solar steam generator. During sunny periods, feedwater is withdrawn from the combined cycle plant heat recovery steam generator, and converted to saturated steam in the solar steam generator. The saturated steam is returned to the heat recovery steam generator, and the combined fossil and solar steam flows are superheated in the heat recovery steam generator. The increased steam flow rate provides an increase in the output of the Rankine cycle. During cloudy periods and at night, the integrated plant operates as a conventional combined cycle facility. Two studies on integrated plant designs using a General Electric Frame 7(FA) gas turbine and a three pressure heat recovery steam generator are currently being conducted by the authors. Preliminary results include the following items: 1) the most efficient use of solar thermal energy is the production of high pressure saturated steam for addition to the heat recovery steam generator; 2) the quantity of high pressure steam generation duty which can be transferred from the heat recovery steam generator to the solar steam generator is limited; thus, the maximum practical solar contribution is also reasonably well defined; 3) small annual solar thermal contributions to an integrated plant can be converted to electric energy at a higher efficiency than a solar-only parabolic trough plant, and can also raise the overall thermal-to-electric conversion efficiency in the Rankine cycle; and 4) annual solar contributions up to 12 percent in an integrated plant should offer economic advantages over a conventional solar-only parabolic trough power plant.