Solar thermal

Free to download eBook on Practical Solar Tracking Design, following the sun solar tracking system, sun tracking system, sun tracker system, solar tracker system, sun positioning system, and sun path tracking with follow the sun position calculation (azimuth, elevation, zenith), sun trajectory, sun following system, sunrise tracking, sunset tracking, sunlight-phases, dawn, dusk, moon-phase, twilight, moonrise, moonset calculator. Solar Tracking is a key Technology to unlock the full potential of RE in RES.
In harnessing power from the sun through a solar tracker or solar tracking system and following the sun, renewable energy system developers require automatic solar tracking software and solar position algorithms. As a result of the apparent motion of the sun, a sun path on-axis sun tracking system such as the altitude-azimuth dual axis or multi-axis solar tracker systems use a sun tracking algorithm or ray tracing sensors or software to ensure the sun's passage through the sky is traced with high precision in automated solar tracker applications, right through summer solstice, solar equinox and winter solstice using sun positional astronomy.

In general, this book may benefit solar research, sun surveying, sun position applet, solar energy harvesting, solar energy tracker and sun tracking solar panel applications in countries such as Africa, Mediterranean, Italy, Spain, Greece, USA, Mexico, South America, Brazilia, Argentina, Chili, India, Malaysia, Middle East, UAE, Russia, Japan and China. This book on practical automatic Solar-Tracking Sun-Tracking is in .PDF format and can easily be converted to the solar tracking system sun tracking system .EPUB .MOBI .AZW .ePub .FB2 .LIT .LRF .MOBI .PDB .PDF .TCR formats for smartphones and Kindle by using the ebook.online-convert.com facility.

From sun tracing software perspective, the sonnet Tracing The Sun has a literal meaning. Within the context of sun track and trace, this book explains that the sun's daily path across the sky is directed by relatively simple principles, and if grasped/understood, then it is relatively easy to trace the sun with sun following software. Sun Surveyor and Sun Position computer software for tracing the sun are available as open source code, sources that is listed in this book. This book also describes the use of satellite tracking software and mechanisms in solar tracking applications using Sun Microsystems and other processor architecture.
Using solar equations in an electronic circuit for solar tracking is quite simple, even if you are a novice, but mathematical solar equations are over complicated by academic experts and professors in text-books, journal articles and internet websites. In terms of solar hobbies, scholars, students and Hobbyist's looking at solar tracking electronics or PC programs for solar tracking are usually overcome by the sheer volume of scientific material and internet resources, which leaves many developers in frustration when search for simple experimental solar tracking source-code for their on-axis sun-tracking systems. This booklet will simplify the search for the mystical sun tracking formulas for your sun tracker innovation and help you develop your own autonomous solar tracking controller.

By directing the solar collector directly into the sun, a solar harvesting means or device can harness sunlight or thermal heat. This is achieved with the help of sun angle formulas, solar angle formulas or solar tracking procedures for the calculation of sun's position in the sky. Automatic sun tracking system software includes algorithms for solar altitude azimuth angle calculations required in following the sun across the sky. In using the longitude, latitude GPS coordinates of the solar tracker location, these sun tracking software tools supports precision solar tracking by determining the solar altitude-azimuth coordinates for the sun trajectory in altitude-azimuth tracking at the tracker location, using certain sun angle formulas in sun vector calculations. Instead of follow the sun software, a sun tracking sensor such as a sun sensor or camera with vision based sun following image processing software can also be used to determine the position of the sun optically. Such optical feedback devices are commonly used in solar panel tracking systems and dish tracking systems.

Dynamic sun tracing is also used in solar surveying and sun surveying systems that build solar radiance, irradiance and DNI models for GIS (geographical information system) and database systems. In such solar resource modelling systems, a pyranometer or solarimeter is used in addition to measure direct and indirect, scattered, dispersed, reflective radiation for a particular geographical location. Sunlight analysis is important in flash photography where photographic lighting are important for photographers. GIS systems are used by architects who add sun shadow applets to study architectural shading or sun shadow analysis, solar flux calculations, optical modelling or to perform weather modelling. Such systems often employ a computer operated telescope type mechanism with ray tracing program software as a solar navigator or sun tracer that determines the solar position and intensity.

Many open-source sun following and tracking algorithms and source-code for solar tracking programs and modules are freely available to download on the internet today. The purpose of this booklet is to assist developers to track and trace suitable source-code and solar tracking algorithms for their application, whether a hobbyist, scientist, technician or engineer. The solar library used by solar position calculators, solar simulation software and solar contour calculators include machine program code for the solar hardware controller which are software programmed into Micro-controllers, Programmable Logic Controllers PLC, programmable gate arrays, Arduino processor or PIC processor. PC based solar tracking is also high in demand using C++, Visual Basic VB, as well as Windows and Mac based software for sun path tables on Matlab, Excel. Some books and internet webpages use other terms, such as: sun angle calculator, sun position calculator or solar angle calculator. As said, such software code calculate the solar azimuth angle, solar altitude angle, solar elevation angle or the solar Zenith angle (Zenith solar angle is simply referenced from vertical plane, the mirror of the elevation angle measured from the horizontal or ground plane level). Similar software code is also used in solar calculator apps or the solar power calculator apps for IOS and Android smartphone devices. Most of these smartphone solar mobile apps show the sun path and sun-angles for any location and date over a 24 hour period. Some smartphones include augmented reality features in which you can physically see and look at the solar path through your cell phone camera or mobile phone camera at your phone's specific GPS location.

Software algorithms predicting position of the sun in the sky are commonly available as Java applets, C++ code, Basic, GBasic and QBasic code, Matlab and Simulink procedures, TRNSYS simulations, Scada system apps, Labview module, mobile and iphone apps, tablet apps, and so forth. At the same time, PLC software code for a range of sun tracking automation technology (mechatronic, electrical, pneumatic, hydraulic drives and motors) can follow the profile of sun in sky for Siemens, HP, Panasonic, ABB, Allan Bradley, OMRON, SEW, Festo, Beckhoff, Rockwell, Schneider, Yokonawa, or Muthibishi platforms. Sun path projection software are also available for a range of processors, including Siemens S7-1200 or Siemens Logo, OMRON PLC, Ercam PLC, AC500plc ABB, National Instruments, PIC processor, Arduino, and so forth. Analogue or digital interfacing ports on these processors allow for tracking orientation angle feedback through one or a combination of angle sensor or angle encoder, shaft encoder, precision encoder, optical encoder, magnetic encoder, direction encoder, rotational encoder, tilt sensor, inclination sensor, or pitch sensor. Note that the tracker's elevation or zenith axis angle may measured with an altitude angle, declination angle, inclination angle, pitch angle, or vertical angle, zenith axis. Similarly the tracker's azimuth axis angle be measured with a azimuth angle sensor, horizontal angle, roll angle sensor.

Many solar tracker applications cover a wide spectrum of solar energy and concentrated solar devices, including solar power generation, solar desalination, solar water purification, solar steam generation, solar electricity generation, solar industrial process heat, solar thermal heat storage, solar food dryers, hydrogen production from methane or producing hydrogen and oxygen from water (HHO). Many patented or non-patented solar apparatus include tracking in solar apparatus for solar electric generator, solar desalinator, solar steam engine, solar ice maker, solar water purifier, solar cooling, solar refrigeration, USB solar charger, solar phone charging, portable solar charging tracker, solar cooking or solar dying means. Your project may be the next breakthrough or patent, but your invention is held back by frustration in search for the sun tracker you require for your solar powered appliance, solar generator, solar tracker robot, solar freezer, solar cooker, solar drier, solar freezer, or solar dryer project. Whether your solar electronic circuit diagram include a simplified solar controller design in a solar electricity project, solar power kit, solar hobby kit, solar steam generator, solar hot water system, solar ice maker, solar desalinator, hobbyist solar panels, hobby robot, or if you are developing professional or hobby electronics for a solar utility or micro scale solar powerplant for your own solar farm or solar farming, this publication may help accelerate the development of your solar tracking innovation.

Presently, solar energy conversion is widely used to generate heat and produce electricity. A comparative study on the world energy consumption released by International Energy Agency (IEA) shows that in 2050, solar array installations will supply around 45% of energy demand in the world. It was found that solar thermal is getting remarkable popularity in industrial applications. Solar thermal is an alternative to generate electricity, process chemicals or even space heating. It can be used in food, non-metallic, textile, building, chemical or even business related industries. On the other hand, solar electricity is wildly applied in telecommunication, agricultural, water desalination and building industry to operate lights, pumps, engines, fans, refrigerators and water heaters.

In this paper, a configuration of photovoltaic-thermal hybrid solar collector embeddable in an indirect solar dryer system is studied. In the present structure of the solar photovoltaic/thermal air collector, the air goes through a double pass below and above the photovoltaic module. A system of electrical and thermal balance equations is developed and analyzed governing various electric and heat transfer parameters in the solar hybrid air collector. The numerical model planned for this study gives a good precision of results, which are close to the experimental ones (of previous literature), and makes it possible to have a good assessment of energy performance regarding the studied configuration (temperature, electric and thermal powers, electrical and thermal efficiencies, etc.). The numerical results show the energy effectiveness of this hybrid collector configuration and particularly its interesting use in an indirect solar dryer system that provides a more suitable air temperature for drying agricultural products. The values of the electrical, thermal and overall energy efficiencies reaches 10.5%, 70% and 90% respectively, with a mass flow rate of 0.0155 kg/s and weather data sample for the month of June in the Algiers site. The results presented in this study also reveal how important the effect of certain parameters and operating conditions on the performance of the hybrid collector.

Given rapid depletion of conventional energy sources and environmental degradation caused by their over exploitation, the renewable energy sources are believed to be the future. Technologies utilizing renewable energy sources differ significantly from one another, not only with regard to technical and economic aspects but also in relation to their reliability, maturity, and operational experience in utility scale conditions. Technologies used to harness solar energy have emerged as the most promising and mature since solar energy is abundant, freely available, and it has commercial potential too. This paper presents a review of advancements made in the field of solar thermal technology with a focus on techniques employed for its performance enhancement. It also covers the description of different types of solar collectors to facilitate the systematic understanding of solar thermal technology and the novel modifications realized in each category of solar collectors have been highlighted to promote the use of solar energy in routine activities. Performance enhancement techniques such as geometrical modifications on the absorber plate, use of solar selective coatings and nanofluids have been given a special attention.

The paper presents the operational results of a real life residential microgrid which includes six
apartments, a 20 kWp photovoltaic plant, a solar based thermal energy plant, a geothermal heat pump,
a thermal energy storage, in the form of a 1300 l water tank and two 5.8 kW h batteries supplying, each,
a couple of apartments. Thanks to the thermal energy storage, the solar based thermal energy plant is
able to satisfy the 100% of the hot water summer demand. Therefore the thermal energy storage represents
a fundamental element in the management of the residential demand of thermal energy. It collects
renewable thermal energy during day-time to release it during night-time, effectively shaving the peak of
the thermal energy demand. The two electric storages, on the other hand, provide the hosted electrical
subsystems with the ability to effectively increase the self-consumption of the local energy production,
thus lowering the amount of energy surplus to be sold back to the grid, and increasing the self-sufficiency
of the microgrid. For instance, the storage has supported self-consumption up to the 58.1% of local energy
production with regard to the first battery, and up to the 63.5% with regard to the second one. Also, 3165
and 3365 yearly hours of fully autonomous activity have been recorded thanks to the first, and the second
battery respectively. On the other hand, the yearly average efficiency amounts to 63.7%, and 65.3%
respectively, for the first and second battery. In the second part of the paper we propose a computational
framework to evaluate the overall performance of the microgrid system, while accounting different operating
conditions and energy management policies. From this perspective, the framework acts as a useful
modeling and design tool, to assess the opportunity of employing alternative energy management system
topologies and strategies. Eight different configurations, with growing complexity, have been derived
from the original system on purpose. The simulations, carried out based on real data related to one-year
time period, have provided results showing that, the higher the integration level of electrical and thermal
storage is, the higher degree of self-sufficiency can be achieved by the microgrid, and, in turn, the more
consistent the yearly energy saving become. Nevertheless, despite the energy cost reduction achievable with the availability of storage systems in the Leaf House, their high investment cost made them not
really profitable at the current price conditions for devices and energy purchase.

In this paper, the energy performance of a photovoltaic/thermal collector equipped with a direct PV air circulation device is studied experimentally and numerically. In this system, the air circulation through the collector duct is ensured by a low input power DC fan that is directly connected to a PV module of small power capacity. In fact, depending on which period of the year the PV/thermal collector is being employed, a 4 Wp or 12 Wp PV panel is used to supply the electrical power to run the DC fan respectively for cold/winter or hot/summer periods. Therefore, the air flow rate under which the present hybrid collector operates is variable and highly affected by the incident solar radiation intensity. A theoretical model for the present hybrid system, in which air flow rate is introduced as a simple empirical correlation relating flow rate to solar radiation, was developed and obtained numerical results have been validated by experimental ones. Simulation and experimental results have been found in reasonably good agreement in terms of PV cell temperature, outlet air temperature, and electric PV peak power. Moreover, the obtained results revealed that low flow rate PV-assisted air circulation systems, if properly sized, would be very attractive for cold periods and winter conditions because of the high air temperature difference they could produce which is a key parameter for space heating applications. On the other hand, the high flow rate system seems to be very suitable for summer conditions where priority is given for the ventilation of PV modules to lower their cells temperature. The suggested PV/T collector design offers the advantage to be self-energy dependent and seems to have a great potential in remote areas.

Prinsloo, G.J., Dobson, R.T., Mammoli, A.A. 2016. Model based design of a novel Stirling solar micro-cogeneration system with performance and fuel transition analysis for rural African village locations. Solar Energy 133, p 315-330 doi:10.1016/j.solener.2016.04.014

This paper describes the performance of a hybrid renewable energy system (HRES) integrated with a combined heat and power cogenerative smart microgrid as remote area power supply (RAPS) in deregulated district energy systems. The research focus on 100% renewables follows on from the ideas of the international energy society (ISES) 100% renewable energy drive, the IEEE smart villages initiative, international renewable energy alliance (IREA), the smart electric power alliance (SEPA) and the alliance for rural electrification (ARE). The proposed hybrid biogas based sun tracker concentrated solar hybrid renewable domestic hot water and power generation system. This alternative energy system design is suitable for space heating, household lighting and cooling refrigeration loads in smart villages, eco-estates, game-farms and remote islands. The study highlights the benefits of embedded generation in integrated and interactive smartgrid configurations for decentralised and district energy systems. International development initiatives such as the Alliance for Rural Electrification and the IEEE Smart Village program have been calling on engineers from developing countries to assist in reducing energy poverty through the design and development of custom designed small-scale sustainable renewable energy solutions. This paper describes the thermodynamic and electrical modeling, simulation and synthesis of a novel kit-based concentrating solar power combined heat and power or hybrid solar cogeneration system. It describes the decentralized solar co-generation system based on a combined cycle Stirling micro-CHP system that includes a low maintenance linear free piston Stirling engine with waste heat recovery, ideal for small business, residential or domestic solar home systems. The concentrating solar combined cycle power and energy system has been designed as a cost-effective community shared solar micro-combined heat and power unit to help enable solar energy utilization within the physical and socio-economic reality of isolated rural areas. This modular plug-and-play unit intends to serve as a stand-alone 100% renewable energy solar powerpack in rural microgrid energy distribution network applications where it will deliver around 3 kW of heat and 1 kW of electricity in distributed generation configurations. The focus of this paper is on the model based design approach in which the main components of the proposed solar micro-combined heat and power system have been systematically modeled on the TRNSYS and Matlab Simulink simulation platforms. This discrete digital modeling approach follows the design guide of the National Renewable Energy Laboratory Village Power Program wherein computer models are used to predict system performance. The TRNSYS model application is extended to meet compulsory World Bank and Development Agency funding and humanitarian investment requirements in terms of providing energy reform and fuel transition projections as part of proving the suitability of newly proposed solar technologies for remote area power applications. The proposed computer model applies statistical weather data to explore the performance, feasibility and fuel transition effects for the solar micro-combined heat and power system in terms of electricity and hot-water generation as well as fuel wood replacement at various locations in Southern Africa. The results show the annual power and hot water generation capability of the system for various sites across Southern Africa, and demonstrates a significant potential in reducing fuel wood usage for villages in these areas. This technology and analysis principles would also be valuable in environmental CO2 sequestration analysis, energy sustainability studies, techno-economic analysis as well as cost benefit studies for greenhouse gas (GHG) mitigation and adaptation technologies. Africa is a developing countries situated in one of the most vulnerable continents to climate variability. Climate change threatens food security and water stress from droughts and floods as well as potential extinction of plant and animal species, calling for nature conservation to reverse wood-land degradation, deforestation and erosion.
This universal distributed generation Stirling engine generation system is ideal for decentralized pre-paid energy co-operatives and pay-as-you-go solar home business models towards empowering remote off-grid villages and indigenous communal living in village communities through indigenous local sustainable energy sources. Energy production from thermodynamic micro-CHP system forms the core of a smart energy system infrastructure that makes up the rural energy system able to serve rural village communities-sustainably. It is intended to ensure sustainable rural development by providing sustainable energy that could displace traditional fossil fuels. The system uses indigenous energy resources, and with added photovoltaic PV or wind energy generation to ensure fossil fuel displacement in replacing fuels such as kerosene, paraffin, candles and wood fuel that cause human health issues and illness due to smoke inhalation. Such hybrid biofuel or biogas solar system provide a sustainable green energy solution and household home heating or district heating solution based on zero-net-energy 100% renewables. It is offered as a humanitarian aid technology to help service coalitions in support of entrepreneurial ventures into engineering for change in remote isolated off-grid rural communities at the bottom of the pyramid.
Follow on work describes the cyber-physical system aspects with smartgrid energy management and control modeling for coordination and optimization of the overall village power system. The integrated community solar and community microgrid solutions are novel in the context of thermo-electrical cogeneration, virtual power plants and hierarchical control structures for remote rural islanded village applications. Hybrid photovoltaic PV, eolica wind, small hydro and biogas cogeneration (poly-generation, tri-generation or hybrid-generation) in multi-carrier pico-grid, nano-grid or micro-grid dispatch can be used for power n energy delivery to drive appliances such as direct current DC LED lighting, fridges, radio, satellite TV, entertainment systems, and sanitation in islanded network configurations. This includes a flexible smart energy management in smart-grid architecture, data analytics and smart-meter instrumentation that includes machine-learning and artificial intelligence with mathematical and economic optimization in demand management, automated demand response, demand management and flexible controllable load curtailment. The intelligent energy management system aspects include customer engagement in control automation, intelligent self-learning, predictive optimization, energy profile or load forecasting, solar forecasting and battery energy storage integration in managing energy reserves. With smart-meter dashboard analytics, this will ensure renewable energy integration in dispersed generation with energy storage (battery, fuel-cell, tank) to ensure practical energy management that deals with the uncertainty, variability, flexibility and energy security in small-scale heat and power microgrids.
Highlights include customer engagement and cooperation in community solar energy utilization in physical & socio-economic reality of isolated rural areas; Localized rural electric power solution to ensure self-sufficient prosumer based energy in community smartgrids; Digital numerical modeling of custom designed kit-based concentrated solar tracker Stirling CSP micro-CHP system; Simulation prediction of CSP system performance in isolated rural African contexts to improve resource coordination and energy preservation; Analysis on fuel transition projections & rural energy generation reform; Need for hot water geyser type energy storage and dispatch; Demonstration of the personalized approach to power supply within sociological relevance and sustainability merit of customized community solar technology.
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https://www.researchgate.net/publication/301659032_Model_based_design_of_a_novel_Stirling_solar_micro-cogeneration_system_with_performance_and_fuel_transition_analysis_for_rural_African_village_locations

Process simulation has become an accepted tool for the performance, design, and optimization calculations of solar desalination process units. Solving the mathematical models representing these units and systems is a tedious and repetitive problem. Nested iterative procedures are usually needed to solve these models. Also, the process configurations are characterized by existence of a number of recycle streams. To tackle these problems, several researchers have developed different methods, techniques, and computer programs for the simulation of a very wide range of variety of solar desalination process units and systems. It is of interest in this work to show and demonstrate a new program working under Matlab/ SimuLink environments for solar desalination processes calculation and modeling. Using these environments a visual design and simulation for different types and configurations of standalone (common) and solar desalination processes can be performed. Embedded user block programming with SimuLink is implemented to construct a flexible reliable and friendly user-interface package. The solar heating systems and desalination plant components (named here as blocks), such as heat exchangers, flash chambers, evaporators, pumps, steam ejector, compressor, reverse osmosis membrane, pipes, etc., are stored as icons in a visual library. This library enables the user to construct different configurations by just clicking the mouse over the required units (blocks). The interface aids designers, and operators to perform different analyses and calculations such as energy, exergy, and thermoeconomics. Typical desalination processes such as multi stage flash, and reverse osmosis are presented to show the wide scope and the validity, reliability, and capability of the developed package.

This paper presents the performance tests carried out on a lab-scale latent heat storage (LHS) prototype during charging and discharging processes. The storage unit is a shell-and-tube type heat exchanger with embedded finned tubes, designed for an LHS capacity of 10 MJ. A ternary mixture comprising of potassium nitrate, sodium nitrate and sodium nitrite in the weight proportion of 53:7:40 is used as the phase change material (PCM). Hi-Tech Therm 60 is used as the heat transfer fluid (HTF). Performance parameters viz., melt fraction, charging/discharging time and energy storage/discharge rate were evaluated at different operating conditions. The effects of HTF inlet temperature and flow rate on the storage characteristics of LHS prototype were analyzed. It is observed that the temperature variation in the angular direction of the prototype during charging process is significant. This is due to the natural convection heat transfer that occurred around the molten layer of PCM while melting. During the discharging process, the angular temperature variation is negligible as the solidification phenomenon is controlled mainly by the conduction heat transfer. It took about 124 min/131 min for charging/discharging of the LHS prototype.

This paper reviews the current status of microgeneration technologies at the domestic scale. Overviews are given for nine such technologies, grouped into three sections: (a) low carbon heating: condensing boilers, biomass boilers and room heaters, air source and ground source heat pumps; (b) renewables: solar photovoltaic panels, flat plate and evacuated tube solar thermal panels and micro-wind; and (c) combined heat and power: Stirling engines, internal combustion engines and fuel cells.

Reviews of the construction, operation and performance are given for the leading commercial products of each technology. Wherever possible, data are presented from the field, giving the actual prices paid by customers, efficiencies and energy yields experienced in real-world use, reliability and durability, and the problems faced by users. This information has a UK focus but is generally relevant in the international context.

Two issues are found to be prevalent throughout the microgeneration industry. Total installed costs are a premium and vary substantially between technologies, between specific products (e.g. different models of solar panel), and between individual installations. Performance in the field is found in many cases to differ widely from manufacturers’ quotes and laboratory studies, often owing to installation and operational problems. Despite this, microgeneration has demonstrated substantial improvements over conventional generation in terms of fossil fuel consumption, carbon dioxide emissions and energy cost, provided that the appropriate technologies are employed, being installed and operated correctly according to the load requirements of the house and their physical location.

An analysis of the temperature stratification inside an Integrated Collector Storage Solar Water Heater (ICS-SWH) was carried out. The system takes the form of a rectangular-shaped box incorporating the solar collector and storage tank into a single unit and was optimised for simulation in Scottish weather
conditions. A 3-month experimental study on the ICS-SWH was undertaken in order to provide empirical data for comparison with the computed results. Using a previously developed macro model; a number of improvements were made. The initial macro model was able to generate corresponding water bulk temperature in the collector with a given hourly incident solar radiation, ambient temperature and inlet water temperature and therefore able to predict ICS-SWH performance. The new model was able to compute the bulk water temperature variation in different SWH collectors for a given aspect ratio and the water temperature along the height of the collector (temperature stratification). Computed longitudinal temperature stratification results obtained were found to be in close agreement with the experimental data.

Hydrogen production through solar energy technology plays a very important role in the development of sustainable energy systems. Traditionally, a wide variety of methods are available for hydrogen production from conventional sources such as natural gas, coal, oil and etc. Their
application, however, contributes to emission of ozone depleting gases such as CO2. This paper reviews the recent developments of hydrogen production methods related to solar-hydrogen production for remote area application. The methods discussed are thermochemical,
photoelectrochemical and electrochemical where water is the basic raw materials. From this review, the low overall efficiency of photoelectrochemical and thermochemical process makes them
non-attractive for remote areas application. This paper concludes that the most suitable method for
hydrogen production for remote area application is electrochemical process where electrolyzer represents the most important process to obtain hydrogen without any emission of air pollutants or greenhouse gases. This paper will be useful for solar hydrogen system manufacturers, academicians and researchers.

Solar thermal water splitting (STWS) produces renewable hydrogen from water using concentrated sunlight. Because it utilizes energy from the entire solar spectrum to directly drive the redox reactions that split water, it can achieve high theoretical solar-to-hydrogen efficiencies. In two-step STWS, a metal oxide is first heated by concentrated sunlight to high temperatures to reduce it and produce O 2 . In the second step, the reduced material is exposed to H 2 O to reoxidize it to its original oxidation state and produce H 2 . Various aspects of this process are reviewed in this work, including the reduction and oxidation chemistries of the active redox materials, the effects of operating conditions, and the solar thermal reactors in which the STWS reactions occur, and a perspective is given on the future optimization of STWS.