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Solar furnace

A solar furnace is a specialized device that harnesses concentrated solar radiation through an array of mirrors or lenses to generate extremely high temperatures, typically ranging from 1,800°C to over 3,500°C, enabling applications such as material testing, metal smelting, and without fossil fuels. The concept traces its practical origins to the mid-20th century, with physicist Félix Trombe constructing the world's first operational solar furnace in Mont-Louis, , in 1949, which reached temperatures of about 3,000°C using a parabolic mirror to focus for metallurgical experiments. This pioneering work laid the foundation for larger-scale installations, culminating in the near Font-Romeu in the , operational since 1970 and recognized as the largest of its kind, featuring a 1,830 m² illuminated by 63 heliostats to deliver 1 MW of power and temperatures up to 3,500°C for advanced research. Solar furnaces operate on the principle of heliostats—movable flat mirrors that track and direct its rays onto a central parabolic concentrator—or directly via large curved mirrors, amplifying solar flux by factors of up to 10,000 times to create a focal point of intense heat for controlled experiments. Notable examples include the National Renewable Energy Laboratory's (NREL) High-Flux Solar Furnace in , which concentrates 10 kW over a 10 cm area to simulate space-like conditions at 1,800°C or higher, and the DLR Solar Furnace in Cologne, , operational since 1994 and used for over 30 years in innovations like at 1,400°C. These facilities have driven key advancements in and , including high-temperature testing of ceramics and alloys for (CSP) systems, eco-friendly metal recycling at 2,000°C, and the production of or fuels like , demonstrating solar thermal technology's potential to replace conventional high-heat industrial processes.

Principles of Operation

Optical Concentration

Optical concentration in solar furnaces relies on reflective or refractive systems to gather and focus incoming onto a small area, achieving the high densities necessary for extreme temperatures. These systems exploit the sun's rays as nearly parallel beams due to its distant position, directing them to converge at a or plane where the is intensified. The primary goal is to maximize the while minimizing optical inefficiencies, enabling applications that require fluxes far exceeding the direct normal (DNI) of . Heliostats serve as the cornerstone for large-scale solar furnaces, functioning as steerable flat mirrors that continuously track the sun's position using two-axis mechanisms to reflect incident rays toward a central receiver. Composed of multiple flat facets, each heliostat maintains alignment with an angular precision typically below 4 milliradians to ensure parallel reflection. In facilities like the High-Flux Solar Furnace at NREL, a single tracking heliostat directs sunlight to a secondary array, demonstrating the scalability of this approach for controlled indoor experimentation. For fixed or smaller-scale setups, parabolic mirrors or dish concentrators provide point-focus concentration through their curved geometry, where the shape directs parallel incoming rays to a single . The and determine the concentration, with the mirror's surface approximating a via faceted segments for manufacturability; for instance, facets with tilt errors under 2 milliradians achieve precise focusing in systems with around 3.8 meters. This design is particularly suited to compact furnaces, as it eliminates the need for extensive tracking arrays. As alternatives for linear focusing, Fresnel lenses and compound parabolic concentrators (CPCs) offer compact, non-imaging that can handle broader inputs, enhancing efficiency in varying weather conditions with diffuse radiation. Fresnel lenses, constructed from concentric grooved prisms, approximate a plano-convex lens to focus linearly or point-wise, as seen in small-scale furnaces achieving high concentrations without mechanical tracking. CPCs, featuring parabolic sidewalls truncated at an acceptance angle, collect both direct and diffuse for linear concentration, maintaining high optical efficiency (up to 80-90%) even under partial cloud cover by accepting rays within a wide range without precise sun-tracking. The mathematical foundation begins with solar irradiance, approximately 1 kW/m² under clear conditions at sea level, representing the direct beam power available for concentration. The concentration ratio C is defined as the total incident power divided by the receiver area, C = \frac{P_{\text{total}}}{A_{\text{receiver}}}, which quantifies the flux intensification; in advanced solar furnaces, this yields peak flux densities up to 10 MW/m², equivalent to thousands of "suns." For example, ray-tracing simulations confirm ratios exceeding 3000 in optimized designs, scaling the base irradiance to extreme levels. Atmospheric effects are already accounted for in the direct normal irradiance (DNI) input, with minimal additional attenuation within the short optical paths of the system. Optical losses significantly impact overall efficiency, including mirror reflectivity limited to 90-95% due to material properties like silvered glass, and cosine effects arising from the off-normal incidence on tilted mirrors, reducing effective by factors such as 0.95 in well-aligned . These factors, combined with and gap losses between facets (up to 5% in heliostat fields and 24% in concentrators), necessitate precise design to approach theoretical maxima.

Heat Generation and Temperature Control

In solar furnaces, concentrated solar radiation is directed onto a , where it is absorbed and converted into primarily through the interaction with high-temperature-resistant materials such as or ceramics. This absorption process rapidly heats the target, enabling temperatures exceeding 3,000°C, with peaks up to 3,500°C achievable in controlled environments like chambers or inert atmospheres such as , which prevent material degradation from oxidation. At these extreme temperatures, a primary challenge is managing heat losses, particularly through , which follows the Stefan-Boltzmann law: the radiative heat flux q = \epsilon \sigma T^4, where \epsilon is the surface , \sigma = 5.67 \times 10^{-8} W/m²K⁴ is the Stefan-Boltzmann constant, and T is the absolute temperature. This fourth-power dependence on temperature results in substantial energy dissipation as , necessitating strategies like low- coatings for reflectivity or active thermal management to sustain operational integrity and efficiency. To prevent receiver meltdown and maintain precise conditions, active cooling systems are integrated, utilizing air or circulation to dissipate excess , while specialized setups may employ cryogenic elements for enhanced in sensitive experiments. Complementary shutter mechanisms, often computer-controlled louvers, intermittently block the incoming beam to regulate and avoid overheating during transient operations. Atmosphere further supports stability by enclosing the in or environments, minimizing convective losses and chemical reactions that could compromise the system. Achieving uniform peak flux distribution across the focal spot—often within ±5% variation—is essential for consistent heating, with designs optimizing heliostat alignment and secondary optics to minimize hotspots and enhance process reliability.

History

Early Developments

The earliest conceptual use of solar concentration for heating dates to ancient times, exemplified by the legendary account of during the of Syracuse in 212 BCE. According to later historical narratives, the Greek mathematician and inventor allegedly employed arrays of polished bronze shields to focus sunlight onto attacking ships, igniting their wooden hulls and sails as a defensive . However, no contemporary records confirm this event, and modern analyses suggest it may be a , as the optical principles and scale required would have been challenging to implement effectively with . In the 18th and 19th centuries, systematic experiments advanced the idea of harnessing heat through simple concentrators. naturalist Horace-Bénédict de Saussure constructed the first "" around 1760, an insulated wooden enclosure covered by multiple glass panes that trapped infrared radiation while allowing visible to enter, achieving internal temperatures up to 100°C suitable for cooking or . This device laid foundational principles for passive heating. Building on this, mathematics professor Augustin Mouchot pioneered active systems in the 1860s, designing a parabolic dish reflector in Alençon that concentrated to boil water and generate , powering a small engine for mechanical tasks and earning acclaim at the 1878 Universal Exposition. Early 20th-century innovations shifted toward practical applications amid growing concerns over scarcity. In 1912, American inventor Frank Shuman erected the world's first solar thermal power station near , , employing long mirrors to heat water and drive steam engines for irrigation pumping, producing up to 50 horsepower and motivated by pre-World War I oil price surges that highlighted the vulnerability of coal-dependent economies. These efforts demonstrated solar energy's potential for industrial-scale heat but remained niche due to economic competition from cheap fuels. The transition to dedicated solar furnaces occurred in the 1940s, driven by wartime needs for high-temperature materials testing in . In , Félix Trombe developed a at Mont-Louis in 1949, featuring a 9.5-meter-diameter parabolic mirror array that focused to reach approximately 3,000°C, enabling experiments on refractory materials without fossil fuels. Key limitations of these early systems included dependence on direct , resulting in intermittent operation, and modest concentration ratios below 100 suns, constrained by manual tracking and rudimentary in the absence of electronic controls.

20th-Century Advancements

Following , research into solar concentration intensified in under the French National Centre for Scientific Research (CNRS), with physicist Félix Trombe leading experiments starting in 1946 that culminated in the construction of the world's first experimental solar furnace at Mont-Louis in 1949, boasting a 50 kW thermal capacity. This facility marked a significant step in high-temperature solar applications for chemistry and . Building on these efforts, CNRS developed the larger , inaugurated in 1970 with a 1 MW peak thermal output, featuring 63 heliostats each covering 45 m² for a total concentrating surface of 2,835 m² composed of approximately 11,340 individual mirrors. The 1980s saw the international expansion of solar furnace technology, exemplified by the Soviet Union's construction of a major facility in in 1981 near , capable of reaching temperatures over 3,000°C using a large composed of 10,700 small mirrors for materials processing in and . This installation, the largest in , reflected growing global interest in solar thermal research amid energy crises. In parallel, advancements in control systems emerged, with computer-based sun tracking introduced for heliostats in solar concentrators during the , enabling precise alignment and enhancing overall system reliability compared to earlier manual methods. Entering the , solar furnaces integrated with hybrid renewable systems, such as solar-gas combined cycles, proliferated in the to ensure continuous operation and boost dispatchability. Optical efficiencies improved to around 30% through advanced mirror coatings with high reflectivity (up to 91%) and selective surfaces that minimize thermal losses. Challenges in deployments, including accumulation reducing reflectivity by up to 50%, were addressed via electrostatic and periodic protocols to maintain . Efforts to outputs beyond 1 MW, the current maximum for dedicated solar furnaces like Odeillo, have focused on modular arrays for potential 5 MW+ systems in central receiver configurations. These developments underscore a shift toward sustainable, high-impact applications aligned with global climate objectives.

Design and Components

Heliostat Arrays

Heliostats in solar furnaces consist of individual mirrors, typically ranging from 1 to 5 m² in area per facet, mounted on dual-axis trackers that enable precise orientation. These trackers allow for azimuth-elevation or spinning-elevation movements, ensuring the mirrors maintain alignment with throughout the day. The mirrors are arranged in a field surrounding the central tower to optimize incidence angles, maximizing the reflection of toward the while accommodating the sun's path. The field layout often employs parabolic or circular patterns, such as radial dense staggered arrangements, to minimize optical losses from blocking and between adjacent s. Blocking occurs when a heliostat intercepts reflected rays from those in front, while prevents incoming sunlight from reaching rear heliostats; optimized layouts reduce these effects by spacing units strategically based on tower height and solar geometry. The number of heliostats varies widely by scale, from 50 units in smaller experimental setups to over 10,000 in large installations, with the utilizing 63 heliostats covering a total area of 2,835 . Tracking systems rely on sun-following algorithms that compute positions using astronomical models, often integrated with GPS for initial and sensors like cameras or detectors for adjustments. Closed-loop mechanisms correct pointing errors to below 1 mrad, enhancing accuracy by comparing actual positions against targets and iteratively refining motor commands. These systems consume approximately 1-2% of the plant's thermal output in power, primarily for drive motors, with wireless implementations further reducing energy needs by minimizing cabling. Heliostat mirrors are commonly made from silvered or films backed by lightweight substrates, achieving specular reflectivity of around 94%. Silvered provides durability and high optical performance, while alternatives offer cost savings but require protective layers to withstand . Anti-soiling coatings, such as hydrophobic or hydrophilic treatments, are applied to reduce and maintain , with testing showing efficacy in limiting losses to 0.1-2% per day in varied climates. Frames are engineered for wind resistance up to 150 km/h (about 40 m/s), using or composite structures with stow positions to mitigate gust loads and prevent damage. Cost factors for heliostat arrays include initial setup expenses of $100-200 per m², encompassing materials, fabrication, and installation, with commercial benchmarks as of 2022 around $99-140/m² depending on scale and technology. Recent analyses as of 2025 suggest installed costs for large-scale fields can reach approximately $96/m², with high-volume production targets around $70/m². Operations and maintenance (O&M) involve regular cleaning to combat soiling, typically every 1-2 weeks in dusty areas to restore , using automated waterless or low-water systems that account for 10-20% of overall field costs. These cycles are optimized via soiling prediction models to balance energy yield against resource use, particularly in arid regions where dust accumulation accelerates losses. Recent advancements in design, as outlined in the 2023 HelioCon roadmap, aim to reduce costs to $50/m² by 2030 through innovations in , materials, and controls.

Focal Systems and Enclosures

furnaces employ two primary receiver types to capture and utilize concentrated : point-focus receivers, which converge into a small circular spot typically 10-50 cm in diameter for achieving extreme localized temperatures, and linear receivers, such as trough configurations, designed for extended heating zones suitable for processing larger samples. Point-focus systems dominate high-temperature applications in research solar furnaces, delivering fluxes up to several megawatts per square meter within the compact spot. s are constructed from materials capable of withstanding temperatures exceeding 2,000°C, including for its high and thermal stability, and for its oxidation resistance and mechanical strength under thermal cycling. The tower structure supporting the receiver is engineered for unobstructed solar access, typically elevated 30-60 meters to minimize shading from surrounding terrain and heliostat fields, as exemplified by the 54-meter tower at the Odeillo facility. To enhance concentration precision, many designs incorporate parabolic secondary mirrors positioned near the receiver, which refocus the incoming beam from the primary array, potentially reducing the spot size by up to 50% and increasing flux density. This secondary setup ensures a tighter distribution while the tower provides a stable platform for alignment and maintenance. Enclosures surrounding the receiver protect the system and enable controlled environments, often featuring insulated vacuum chambers maintained at pressures around 10^{-3} mbar to facilitate processing and prevent oxidative degradation of samples. is integrated through beam shutters that can rapidly block incoming , alongside remote monitoring systems utilizing thermocouples for direct and infrared cameras for non-contact flux visualization. These enclosures also incorporate water-cooled supports to manage heat dissipation from the base. Safety protocols are paramount given the intense radiant fluxes, with flux mapping techniques employed to identify and mitigate hotspots that could exceed 20 MW/m² and risk material meltdown. Emergency defocusing mechanisms, such as misalignment or attenuator deployment, allow immediate flux reduction, while shielding around the enclosure prevents unintended exposure to personnel and equipment. Scalability is achieved through modular receiver designs, permitting upgrades such as the of specialized absorbers for processes like thermochemical without overhauling the core structure. This supports to evolving needs while leveraging the existing tower and optics infrastructure. Recent developments, including new solar receiver concepts from NREL's 2024 Consortium report, emphasize innovative designs for enhanced efficiency and with .

Applications

Material Processing

Solar furnaces enable the melting and purification of various ores through concentrated , achieving temperatures up to 2,000°C for processes like aluminum without reliance on fossil fuels or . This direct reduction method significantly lowers compared to conventional , as it avoids carbon-intensive energy sources and can reduce climate-altering gas outputs by integrating renewable heat. For instance, refinement for photovoltaic applications benefits from solar purification techniques that produce high-purity material suitable for cells, leveraging the furnace's ability to volatilize impurities at elevated temperatures. In alloy development, solar furnaces facilitate rapid heating and cooling cycles essential for synthesizing advanced materials such as and metal s. These systems reach processing temperatures exceeding 3,000°C in seconds, enabling dwell times under one minute—far shorter than the hours required in traditional electric furnaces—while preserving material integrity through controlled thermal gradients. Examples include the solar synthesis of () from precursors, where the intense, instantaneous flux promotes uniform carbide formation without intermediate melting phases. Similarly, carbides of group Va metals like , , and have been produced via eruptive heating in solar setups, yielding high-purity alloys for high-temperature applications. Solar furnaces also support through carbothermal reduction, converting toxic industrial wastes into inert forms at temperatures around 1,200–1,400°C. This process extracts hazardous contaminants, such as those in dust (containing like and lead), for and safe disposal without generating secondary pollutants. The method uses to drive reduction reactions with carbon additives, effectively recovering valuable metals. Economically, solar furnaces can offer significant operational cost advantages over arc furnaces, potentially up to three times more cost-effective in optimal solar conditions, though production is constrained to peak sunlight hours of 4-6 per day. processing has been applied to zirconia (ZrO₂)-based barrier coatings through surface to enhance durability for components. This application demonstrates scalable of high-performance ceramics with minimal input beyond solar concentration.

Scientific and Industrial Research

Solar furnaces facilitate high-temperature simulations that replicate atmospheric re-entry conditions, achieving temperatures around 3,000°C to test materials such as heat shields for . At facilities like ' National Solar Thermal Test Facility, these tests evaluate the resilience of nose cones, sensors, and thermal protection systems for missions including NASA's Mars Sample Return, offering a cost-effective alternative to arc jet facilities at approximately $21,000 per day. Similarly, the German Aerospace Center's (DLR) high-flux solar furnace conducts irradiation tests under vacuum to assess shock resistance and material behavior exceeding 2,000°C, supporting certification of components. In thermochemical studies, solar furnaces enable investigation of reaction kinetics under concentrated solar flux, particularly for via -splitting cycles where high heat drives the dissociation of into and oxygen. The National Renewable Energy Laboratory's (NREL) High-Flux Solar Furnace supports this through experiments at 1,300°C as part of the HydroGEN Advanced Materials , focusing on metal reactions for efficient fuel cycles. DLR's facility similarly demonstrates solar-driven generation, exploring materials for enhanced thermochemical efficiency in energy storage and conversion processes. Optical and plasma research benefits from the precise flux control in solar furnaces, enabling experiments like solar-pumped lasers and arc-free techniques. NREL's furnace has been used to design high-brightness Nd:YAG solar-pumped lasers, leveraging concentrated for efficient in potential space applications. Flux uniformity also supports studies of high-temperature s generated without electrical arcs, aiding analysis of material properties under controlled solar irradiation. Industrial R&D utilizes solar furnaces for developing advanced solar receivers and biofuels through processes like pyrolysis at high temperatures around 1,500–1,900°C, converting feedstocks into and other fuels. NREL's setup tests receiver components for plants, while studies on solar-thermal of , such as mallee wood, demonstrate yields of and bio-oil under direct solar heating. These efforts advance sustainable alternatives to fossil-based processes, with patents emerging from furnace-based reactions like decarbonization. Collaborative programs, including EU-funded initiatives, drive solar furnace research in areas like metal extraction and thermochemical . The SOLZINC successfully piloted for production from ores, storing in metallic form for applications. At CNRS-PROMES in Odeillo, the Next-CSP (2016–2021) involved 10 European partners to develop particle-based receivers, yielding advancements in high-temperature solar chemistry and numerous peer-reviewed publications on solar-driven processes.

Notable Installations

The , situated in in the French Pyrenees at an altitude of approximately 1,700 meters, represents the world's largest solar furnace and a flagship installation of the French National Centre for Scientific Research (CNRS). Constructed between 1962 and 1970 by CNRS at its PROMES laboratory, the facility measures 54 meters in height and 48 meters in width, evolving from earlier prototypes like the Mont-Louis furnace to enable advanced high-temperature research. The furnace employs 63 heliostats—movable flat mirrors—covering a total reflecting area of 2,835 , which direct onto a large off-axis parabolic mirror with an 18-meter and 1,830 surface. This configuration concentrates radiation to deliver a peak thermal power of 1 MW, achieving flux densities up to 10 MW/ and temperatures exceeding 3,000°C—potentially reaching 3,500°C—in a focal spot approximately 0.5 in size, equivalent to the area of a small cooking . Operations occur within an eight-story tower housing experimental chambers on multiple levels, allowing controlled atmospheres, high-vacuum conditions, and in-situ diagnostics like pyrometry and for precise material testing. The provides about 1,500 to 2,000 hours of annual operation, depending on weather, supporting diverse experiments in material synthesis, storage, and high-temperature processes without byproducts. Key innovations include the pioneering use of a large field with computer-controlled two-axis tracking implemented in the , enabling precise sun following and optimization of energy capture, which was unique at the time and set standards for subsequent concentrator designs. operational modes, integrating auxiliary heating for conditions, further enhance reliability for continuous experimentation. Over its five decades of service, the furnace has facilitated thousands of research projects, training more than 1,000 scientists and engineers while influencing global thermal technologies through collaborations in European initiatives like SFERA and SOLLAB; its sustainable approach to high-temperature research has been highlighted in publications on ethics and applications.

Other Global Examples

The Parkent Solar Furnace in , commissioned in 1987, consists of 62 arranged in a heliostat field, achieving a thermal power output of 1 MW for high-temperature applications. It has been utilized for high-temperature materials processing, including synthesis of ceramics and fireproof materials for industries such as and , and recent applications in eco-friendly . In , the Mont-Louis Solar Furnace, operational since 1951, features a 20 m tower and delivers 50 kW (0.05 MW) of concentrated solar energy, serving as an early prototype for advanced installations like Odeillo. It conducted pioneering tests, focusing on melting and alloying processes under controlled solar heat to explore non-fossil fuel alternatives for metal production. United States examples include the White Sands prototype built in 1958 for the US Army at , with a 35 kW (0.035 MW) capacity for simulating re-entry conditions in testing through intense flux exposure. Modern efforts at incorporate hybrid furnaces, combining concentrated with auxiliary heating systems to enhance reliability for thermochemical and materials research. The DLR Solar Furnace in Cologne, Germany, operational since 1994, is used for research in solar hydrogen production and high-temperature materials testing at up to 1,400°C. It has supported innovations in renewable fuels and alloys for over 30 years as of 2024.
FacilityPower Output (MW)Mirror CountPrimary Use
Parkent, Uzbekistan (1987)162 heliostatsMaterials processing and steel recycling
Mont-Louis, France (1951)0.05N/A (parabolic mirror)Early metallurgy tests
White Sands, USA (1958)0.035N/AMissile testing simulations
Sandia Labs Hybrid, USA (modern)0.0161 heliostat + concentratorThermochemical hybrid research
DLR, Germany (1994)N/AN/ASolar hydrogen production and materials research
Odeillo, France (1970, reference)1.063 heliostatsGeneral scientific research

Smaller-Scale Variants

Household Solar Ovens

Household solar ovens are compact devices designed for everyday cooking in homes, particularly in regions with abundant and limited access to traditional fuels. These appliances harness through concentration or trapping methods, enabling users to bake, boil, or fry food without or fossil fuels. They typically consist of reflective surfaces and insulated enclosures that capture and retain heat from direct , making them suitable for off-grid living and sustainable practices. Box-style solar ovens, one of the most common household variants, feature an insulated box made from materials like wood, metal, or cardboard, lined with reflective surfaces such as aluminum foil to maximize light capture. A transparent or lid allows to enter while trapping heat inside, often reaching temperatures of 150–200°C for baking and roasting. These designs originated in the 1970s, with pioneers like Barbara Kerr and Sherry Cole developing affordable cardboard models that influenced widespread adoption. For instance, Solar Cookers International's early prototypes emphasized simple construction using readily available materials, promoting their use in developing areas for tasks like pasteurizing water or cooking grains. Parabolic solar cookers, another popular household option, employ a portable dish-shaped reflector, typically 1–2 meters in diameter, to focus onto a central pot or pan, achieving higher temperatures around 300°C suitable for or quick . Users manually adjust the dish's orientation every 15–30 minutes to track , with optical efficiencies ranging from 40–60% under optimal conditions. This concentrating approach provides faster cooking compared to box styles but requires more user intervention for alignment. Adoption of household solar ovens has been significant in off-grid regions, particularly in , where over 1.2 million units have been distributed by programs through the Ministry of New and Renewable Energy. These devices reduce consumption by 30–50%, alleviating and lowering household fuel costs while providing smoke-free cooking that decreases respiratory illnesses from indoor . In rural households, this shift supports by reducing time spent collecting fuel and exposure to harmful smoke. Despite their benefits, household solar ovens face limitations, including complete dependence on direct , rendering them ineffective on cloudy days or at night. Cooking times are generally 2–4 times longer than gas or electric methods, often requiring 2–3 hours for a full meal, which can challenge busy schedules. Modern variants emphasize portability and ease of use, with foldable parabolic or box models that pack into carrying bags for or travel, priced between $20 and $100. Innovations include lightweight aluminum frames and adjustable reflectors for better stability, enhancing accessibility for consumer markets while maintaining core concentration principles.

Experimental and Educational Devices

Experimental and educational solar furnaces are compact devices designed to demonstrate the principles of solar concentration and high-temperature generation in controlled settings, such as classrooms, laboratories, or small-scale environments. These systems typically employ parabolic mirrors or Fresnel lenses to focus onto a , achieving temperatures sufficient for basic experiments without the of large installations. They serve as hands-on tools to illustrate concepts like radiative , optical concentration ratios, and applications, often used in physics, , and curricula. Commercial educational kits, such as the Solar Furnace Physics Demonstration Kit, utilize a 30.5-cm mirrored parabolic dish to concentrate solar radiation onto a receiver positioned at its 18.5-cm , enabling rapid heating that can boil liquids or melt low-melting-point materials like or . Similarly, devices from educational suppliers feature adjustable 30-cm parabolic mirrors focusing light onto a 20-mL container, to 100°C in minutes under direct , with mirror angles tunable over 180° for optimal alignment. These kits emphasize safety features, such as non-staring focal points, and include guides for experiments on and effects. In experimental contexts, small-scale solar furnaces built with Fresnel lenses allow for higher-temperature demonstrations, concentrating sunlight to focal points reaching up to 422°C in ambient conditions of 17°C, suitable for material testing or . A parabolic prototype constructed from 914-mm mild with reflective mirrors achieved steady temperatures of 95°C for applications like water or basic , highlighting scalable designs for student projects in . Such devices facilitate quantitative studies on and receiver , fostering understanding of energy's potential in sustainable technologies.