Spectral Beam Splitting Research Articles

A conical spiral methanol steam reforming reactor for spectral splitting-based concentrating photovoltaic-thermochemical hybrid production

The spectral beam splitting (SBS) photovoltaic-thermochemical hybrid system improves the solar thermal energy grade through photon energy cascade distribution and methanol steam reforming (MSR) reaction. Given the deficiency of MSR reactor development for dish-concentrating SBS systems, the conical spiral structure is introduced to the receiver/reactor in this work, thus facilitating efficient absorption of circular beams and ameliorating the adaptability of the production. Based on specially designed spectral beam splitter, the Monte Carlo ray tracing (MCRT) method is employed to simulate the non-imaging optical process and optimized reflective cone structure. Thermodynamics and kinetic models of the reactor are established and experimentally validated. The analysis results show that the reflective cone advances the optical efficiency of the reactor to 76.95%, and the conical spiral structure helps to enhance heat and mass transfer for utilization of the catalytic space. The mid/low-temperature reaction prefers a solution flow rate of less than 1.53 mL s−1 and a water-methanol ratio of 1.4–1.9, with the maximum solar thermochemical conversion rate of 54.5%. Moreover, the upgrading in photothermal and photovoltaic heat exceeds respectively 0.62 and 8.97 at less than 600 W m−2 of irradiation, demonstrating the adaptive potential of the reactor. In summary, the research results contribute to broadening the operating conditions of the hybrid production and the full-spectrum penetration of solar energy in distributed scenarios.

Next-generation solar technologies: Unlocking the potential of Ag-ZnO hybrid nanofluids for enhanced spectral-splitting photovoltaic-thermal systems

In traditional hybrid concentrating photovoltaic-thermal (PV-T) collectors, suboptimal utilisation of the solar spectrum results in elevated temperatures that adversely affect PV cell efficiency. In this context, solar spectral beam splitting (SBS) designs have emerged as they promise improved solar spectrum utilisation with reduced optical losses. In particular, fluid-based SBS filters, such as novel Ag-ZnO/water hybrid nanofluids, have attracted attention as they present a significant advantage over conventional filters (e.g., anti-reflective coatings, selective coatings, bandpass filters, long-pass/short-pass filters, dielectric filters). These nanofluid filters serve as both heat transfer and thermal storage mediums, enhancing the overall efficiency of PV-T systems. Full-spectrum solar utilisation via SBS enables down conversion in the UV region, transmission of visible and near-infrared light (crucial for Si PV cell optoelectronic efficiency), and absorption of the infrared region. A Ag-ZnO/water nanofluid filter-based PV-T system is investigated and is shown to achieve a thermal efficiency > 65 % with good electrical performance. Optimal conditions include an Ag-ZnO concentration of 50 ppm, solar irradiance of 800–1000 W/m2, and optical thickness of 20 mm. The integration of this type of nanofluid filter enhances spectral selectivity, reduces PV cell temperatures, improves heat extraction, and offers dual functionality: cooling and filtration, making it a promising and economically viable candidate for commercial PV-T applications.

Experimental study on a direct-expansion micro-channel PV/T evaporator using water-ZnO nanofluid as the spectral beam splitter

Introducing nanofluid (NF) as the spectral beam splitter (SBS) in photovoltaic/thermal (PV/T) evaporators can significantly enhance their performance and energy flexibility. In this study, a novel direct-expansion micro-channel evaporator using water-ZnO nanofluid as SBS (i.e., NF-MC-PV/T evaporator) was manufactured. Particularly, the stability of low-viscosity water-ZnO nanofluid was first optimized and natural convection within the NF-MC-PV/T evaporator was directly formed. Further, a direct-expansion heat pump system based on the NF-MC-PV/T evaporator was developed and tested. According to the findings, adding sodium hexametaphosphate as a dispersant with the dispersion ratio of 1:5 and ultrasonic treatment for 1.5 h can achieve the optimal stability of water-ZnO nanofluid. The nanofluid's natural convection can reduce the evaporator's operating temperature and improve the PV module's temperature distribution uniformity. Specifically, the NF-MC-PV/T evaporator's operating temperature was lower than the environment temperature and a pure PV module. Besides, the PV module's temperature distribution was uniform in the direction perpendicular to the refrigerant flow with a max temperature gradient of only 4.59 °C. The typical photothermal efficiency of the NF-MC-PV/T evaporator reached 102.55 % while the heat loss coefficient was only 4.37. Moreover, the average photothermal efficiency, photovoltaic efficiency, and COP of the system were 103.58 %, 12.03 %, and 5.09, respectively.

Comprehensive performance analysis of CST-PV system based on spectral beam splitting film

Abstract In this paper, a novel linear Fresnel concentrator (LFC) with a rotating platform was constructed, and a novel concentrated solar thermal and photovoltaic (CST-PV) hybrid system utilizing spectral beam splitting was established on the LFC. A spectral beam-splitting film (SBSF) was coated on the PV cell’s inner glass wall, replacing the LFC’s primary reflector. The SBSF can transmit the solar spectrum of 300-1100 nm to the photovoltaic (PV) cells and reflect the remaining solar wavelengths to the absorber to generate heat. The LFC’s cosine efficiency and end efficiency after azimuthal compensation by a rotating platform were calculated through theoretical analysis. The effects of temperature on the efficiency of PV and linear Fresnel solar systems were studied through experimental and numerical simulations. The comprehensive utilization efficiency evaluation method was established. The results show that the LFC’s end efficiency and cosine efficiency in this paper, after azimuthal compensation, increased by 31.7% and 33.7%, respectively, compared with the east-west and north-south axis placement. The comprehensive utilization efficiency of the CST-PV system based on SBS is 61.58%, which increased by 13.47% compared to that of the single fixed PV system.

Improved Land Use Efficiency Through Spectral Beam Splitting in Agrivoltaic Farms

Installing photovoltaic (PV) collectors above arable land (Agrivoltaics) can aid with the shortage of available land area for solar power generation and food production. Most open field agrivoltaics are based on opaque PV devices which absorb photosynthetically active radiation (PAR, 400-700 nm), reducing crop yield and increasing variability in light distribution across the field. This research evaluates the performance of spectral beam splitter integrated photovoltaic (BSIPV) modules using a PV performance model. A high percentage (66 %) of PAR incident on the spectral beam splitter is transmitted effectively to the plants, while the near infrared radiation (NIR, > 700 nm) is reflected to the adjacent bifacial opaque photovoltaic module to generate power. In the model, seven rows of modules were placed uniformly across the field at a height of four meters from the ground. Considering a cool season (November – March) in Yuma, Arizona, in a conventional opaque PV agrivoltaic farm received 43 % lower total daylight integral (TDLI) across the season in comparison to open field with a coefficient of variation (ratio of standard deviation to mean expressed in percentage) of 56 % in TDLI across the field. On the other hand, the BSIPV agrivoltaic farm limited the drop in TDLI to 7 % in comparison to open field and the coefficient of variation to 14 % across the field. Thus, BSIPV showed a 36 % improvement in TDLI relative to the conventional opaque PV agrivoltaic farm. The results of the current study justify further research on the proposed collector concept.

Performance analysis of a novel solar Linear Fresnel concentrator system based on spectral beam splitting

Photothermal and photovoltaic are the most common and commercialized ways of utilizing solar energy. However, they cannot use solar energy efficiently. SBS (spectral beam splitting) technology is an efficient solar energy utilization technology that can realize the full spectrum utilization of solar energy. The current work involved: (1) Proposing a SBS-LFCs (linear Fresnel concentrator system) based on spectral beam splitting. In this system, the SBS photovoltaic panel replaces the conventional linear Fresnel concentrator lens, which can realize photovoltaic and photothermal utilization at the same time; (2) Developing a spectral splitting thin films configuration using the Needle method whose transmittance is higher than 90% against 380 nm-1100 nm band range; (3) Designing the SBS photovoltaic panel structure. The cover glass surface is covered with a SBS thin film. The SBS photovoltaic panel replaces the concentrator lens of LFCs; (4) Taking four typical days as examples, the annual power generation of a SBS linear Fresnel focusing system was predicted. The outcome indicates that the total conversion efficiency of solar thermal power in the system is 23.8%, 23.5%, 23.5%, and 23.6% on the spring equinox, summer solstice, autumn equinox, and winter solstice, respectively. Compared to conventional monocrystalline silicon cells, the photoelectric conversion efficiency has been improved by 14.6%, 12.8%, 12.5%, and 14.1%, respectively.

Performance prediction of a novel solar power tower system based on spectral beam splitting

Photovoltaic technology is currently the most widely used solar generation technology in engineering. The particular spectral response band of PV cells cannot convert all solar radiation into electricity. Meanwhile, some radiation will become heat, leading to an increase in cell temperature and a decrease in the conversion efficiency of photovoltaic cells. Spectral splitting technology is an effective technology to improve electrical generation efficiency and can achieve full spectrum utilization of solar energy. The current work involved (1) proposing a novel solar power tower comprehensive utilization system based on spectral splitting; (2) developing a spectral splitting thin film configuration by using the Needle method whose transmittance is higher than 90% against the band range of 510 nm-1, 020 nm; (3) setting up a spectral splitting PV panel whose cover glass is coated the developed film, and replacing the heliostat of SPT system by using such spectral splitting PV panels; (4) predicting the electrical power generation of the spectral splitting-based tower type concentrating solar power system. The results demonstrate that the power generation efficiency of the proposed system is 5.5% and 3.46% higher than PV power generation and SPT systems respectively.

Advancing performance assessment of a spectral beam splitting hybrid PV/T system with water-based SiO2 nanofluid

Advancing performance assessment of a spectral beam splitting hybrid PV/T system with water-based SiO2 nanofluid

Mathematical model to optimize solar spectrum allocation for a Stirling engine-based concentrated photovoltaic thermal system

Incorporating a Stirling engine into a concentrated photovoltaic thermal system (CPVT) with spectral beam splitting converts wasted photovoltaic panel energy into electricity, boosting efficiency. However, complex Stirling engine development slows system performance estimation, which explains the scarce studies on the Stirling engine-based CPVT spectrum allocation range. Furthermore, the literature shows inconsistent remarks on low or high-energy photon allocation to a thermal system and uncertainty of solar irradiance variation effect on spectrum allocation. A generic methodology is presented for determining optimal spectrum allocation for a Stirling engine-based CPVT system with a dichroic filter. The analysis in this work shows that considering non-absorption and thermalization losses improves performance by 13.2 % compared to solely accounting for non-absorption loss in beam splitting. Additionally, a shift of up to 40 nm in the optimal spectrum allocation range is observed with a daily spectral irradiance source compared to the AM1.5D source. The PV mathematical model is validated with an average error of 8.9 %, and the Stirling engine model with an error of 5.2 %. Through this study, future researchers can determine an optimal spectrum allocation range for Stirling engine-based CPVT that maximizes PV performance based on a specified location with the proposed generalized CPVT model.

Simulated Performance Analysis of a Hybrid Water-Cooled Photovoltaic/Parabolic Dish Concentrator Coupled with Conical Cavity Receiver

The present research discloses a novel hybrid water-cooled Photovoltaic/Parabolic Dish Concentrator coupled with conical cavity receiver and spectral beam splitter (PV/PDC-CCR-BSF). In effect, a compact co-generating solar-concentrating PV system involving a subsequent optical interface has been fully developed and numerically tested. The optical performance of the proposed hybrid solar-concentrating system was modeled and assessed using the RT 3D-4R method while the thermal yield of the system was examined using the Finite Element Method. In addition to that, different configurations of serpentine-shape embedded water-cooling pipes (rectangle, semicircle, semi-ellipse and triangle) have been tested and optimized for maximum heat collection and minimum operating cell temperature. The performance of all the tested serpentine-shape embedded water-cooling pipes was evaluated with respect to conventional serpentine-shape water-cooling pipes. The outcomes indicated that the triangular cross-section outperforms other shapes in terms of heat dissipation capabilities, with about −446 W and maximum useful thermal power in the medium of the heat transfer fluid of 11.834 kW.

Experimental investigation on parameter optimization of liquid spectral beam splitter for continuous photocatalytic hydrogen production accompanied with photovoltaic power generation under solar full spectrum

Effective utilization of solar energy is of great significance for a sustainable future. Herein, we report a cascade system for hydrogen-electricity co-production (PH-PV) utilizing solar full spectrum. The output performance of the system can be precisely adjusted by controlling certain parameters of liquid spectral beam splitter (LSBS) which contains TiO2 nanoparticle suspension simultaneously generating hydrogen via a photocatalytic reaction process. Typically, the thickness of LSBS, the loading amount of TiO2, the flowrate of suspension and the light intensity have been investigated in detail. It is found that LSBS is necessary in our system as it could ensure the safe operation of PV while the light intensities larger than 8 suns. With the decrease of the thickness or loading amount of photocatalyst, more electricity could be produced by PV module but less hydrogen from PH module. Further increase of above two parameters simultaneously could lead to aggregation and settlement of particle suspension in LSBS, which is detrimental to the optical absorbance of the system. Besides, changing the flowrate will diversify the surface features of particles by shear-induced effect. At optimal flowrate, the particles in LSBS could exhibit oscillation characteristics under synergistic effect of shear force and gravity, which would lead to excellent light absorption and transmittance. Furthermore, an obvious gain for both hydrogen and electricity output and system efficiency could be obtained through increasing light intensity appropriately. Finally, the improved merit function (MF) was employed to evaluate the performance of hybrid system and more obvious effect of flowrate on MF value than other parameters was found. The optimal MF value of 3.07 was reached when flowrate was 60 mL/min. Our work is expected to provide important guidance for the optimization of PH-PV cascade system driven by outdoor direct solar energy.

Selective transmission and absorption in oxide-based nanofluid optical filters for PVT collectors

The division of the solar spectrum in a photovoltaic thermal (PVT) collector serves a dual purpose for separate heat and electricity applications. One part of the spectrum is used for generating electricity, which prevents the excessive temperature increase of the photovoltaic cells, while the other part facilitates a thermal gain. This concept is termed as spectral beam splitting (SBS). In this work, the implementation of SBS in a PVT collector using a nanofluid-based optical filter is investigated. An optical model, based on Rayleigh scattering, is developed to analyze various oxide-based nanofluids for SBS. The purpose of the model is to determine the transmittance and absorbance of ZnO, Fe3O4, and SiO2-based nanofluids across the solar spectrum range of 300 nm to 2500nm. The model takes into account the complex refractive indices of the particles and base fluids to determine the scattering, extinction, and absorption efficiencies of the nanofluids being studied. The oxide-based nanofluids outperformed the polypyrrole and Cu9S5-based nanofluids in terms of spectral transmission and absorption of sunlight. Water, de-ionized water, and ethylene glycol are used as base fluids. The nanoparticle-base fluid duos determine the agglomeration and size of the particles in the nanofluid and hence affect their optical properties. Therefore, ZnO-based nanofluids are synthesized in-house to correlate the effects of agglomeration and particle size on the optical properties of the nanofluids derived from the developed theoretical model. Using ethylene glycol as a base fluid has a significant impact on reducing agglomeration, resulting in smaller and more stable nanoparticles, in comparison to using de-ionized water. Furthermore, the influence of particle size, dispersion in the base fluid, and optical length on the optical properties of the nanofluid are examined. It is concluded that adjusting the size (dispersion), concentration, and optical length of the particles can allow for the efficient use of the solar spectrum to generate both electrical and thermal energy.

Tunable optical properties of ATO-CuO hybrid nanofluids and the application as spectral beam splitters

Nanofluids containing metal nanoparticles have promising application prospects in the spectral beam splitters (SBSs) of photovoltaic/thermal (PV/T) setups on the merits of the tunable spectral absorption characteristic and relatively low price. While the existing nanofluid-based SBSs show some difficulties in large-scale industrial applications, such as their poor stability, sophisticated manufacturing process, etc. In this paper, a cheap and stable hybrid nanofluid containing antimony tin oxide (ATO) and cupric oxide (CuO) nanoparticles has proven to be a good candidate for SBSs. ATO has high absorption in the infrared region while CuO shows strong absorption for ultraviolet and visible light, so ATO and CuO nanoparticles have complementary optical properties and the spectral absorption of ATO-CuO hybrid nanofluids is expected to be effectively regulated by adjusting nanoparticles’ composition. Meanwhile, the increase in nanoparticle concentration can enhance the light absorption ability of hybrid nanofluids in the full spectrum. The hybrid nanofluid SBS with a 5:5 ATO:CuO mass ratio and 200 ppm concentration proves to perform best and the merit function is as high as 1.679 (worth factor is 3), which is highly competitive among the metal-based nanofluid SBSs from literature.

CWO/SiO2 spectral beam splitter coating for photothermal synergetic catalysis: Design and development

Solar-energy-driven hydrogen production from biomass is a key technology for green hydrogen production. Photothermal synergistic catalysis is an effective means to enhance biological hydrogen production. In this study, a spectral beam splitter coating (SBSC) adapted for photothermal synergetic catalysis is designed and developed based on cesium tungsten bronze (CWO) and silicon dioxide (SiO2) in a sol–gel system. The CWO/SiO2 SBSC exhibits short-wavelength transmittance up to 85.7 % and absorption of near-infrared (NIR) light up to 91.3 % by adjusting the lifting speed, filling factor, and curing temperature. Evaluation model calculations reveal that the CWO/SiO2 SBSC can significantly improve the hydrogen production rate when the reaction solution temperature is 80 °C and that the integrated solar energy conversion efficiency is 3.7 times that without the SBSC. The results demonstrate the high durability of the CWO/SiO2 SBSC as well as its promising application scope in the photothermal synergetic catalysis of biomass hydrogen.

Experimental study of a concentrating solar spectrum splitting system for hybrid solar energy conversion

Spectral beam-splitting represents a potential approach to enhance energy conversion in solar concentrating systems. This study introduces a novel hybrid solar concentrator system, comprising a dish reflector with a two-axis tracking system and an affordable optical linear system that divides the concentrated solar beam into distinct visible spectral bands. Experimental investigations were conducted, encompassing an optical analysis of the splitter system and an assessment of photovoltaic and thermal power generation from the prototype throughout a day with solar tracking. Results indicate that the splitter system achieved a transmissivity of 76 % within the 400–800 nm range with clear separation between spectral bands, demonstrating system reliability. Spectral band dimensions remained relatively constant throughout the day, with widths of 0.460 cm, 0.550 cm, and 0.700 cm for red, blue, and yellow bands, respectively. The photovoltaic cell exposed to the yellow band exhibited the highest power and current intensities, with power densities of 15 mW/cm2 at noon, compared to 12 mW/cm2 for the blue and 5 mW/cm2 for the red bands. The system also recovered thermal power, reaching a maximum of 190 W around noon. The paper discusses suitable photovoltaic cell types for each band color and explores opportunities for improved efficiency and large-scale implementation.

Performance analysis of a nanofluid spectral splitting concentrating PV/T system with triangular receiver based on MCRT-FVM coupled method

Optimizing system structure is one promising way to enhance the spectral beam splitting concentrating photovoltaic/thermal (SBS CPV/T) system performance. In this study, a linear Fresnel CPV/T system incorporated with triangular cooling duct and Ag@SiO2/ethylene glycol (EG) nanofluid filter is designed to enhance the overall performance of the system. To quantitatively reflect the heat generation of Ag@SiO2/EG nanofluid filter and silicon PV modules under inhomogeneous solar flux distributions, a coupled method combining Monte Carlo ray tracing (MCRT) method with Finite Volume Method (FVM) is employed. After validating the coupled method, the performance of the system with triangular receiver is discussed under various operating conditions. The results demonstrate that the nanofluid outlet temperature and PV module temperature present 316.3 K and 306.8 K at nanofluid inlet temperature of 298 K, respectively. The high mass flow rate and low inlet temperature allow high thermal and total efficiencies, while they present slight effect on electrical efficiency. To quantify the achievable enhancements with the triangular receiver, a SBS CPV/T system with flat-plate receiver is also discussed. It is found that the total efficiency of the triangular receiver is higher than that of the flat-plate receiver, with a maximum enhancement of 7.9%.

Optimisation and analysis of an integrated energy system with hydrogen supply using solar spectral beam splitting pre-processing

The application of integrated energy systems (IES) in urban areas is gradually increasing, yet the constraint of limited building space poses a significant challenge to effective system planning. In this paper, to address the issue of area limitation from the perspective of improving solar energy utilization. A novel IES utilizing solar spectral beam splitting (SBS) for hydrogen production is proposed, which introduces SBS technology to make full use of the sun’s full-spectrum energy. Furthermore, the incorporation of photocatalytic hydrogen production introduces an innovative approach to meet the hydrogen needs of hydrogen refuelling stations, facilitating highly efficient co-generation of cooling, heating, electricity, and hydrogen supply. To determine the optimal system configuration, a comparison is made with a stand-alone solar system using a honey badger-simulated annealing optimization algorithm. The results show that the SBS-IES achieves a solar energy utilization rate of 37.72% and reduces equipment footprint by 20.48%. Furthermore, a sensitivity analysis is performed to analyse the impact of changes in floor space on the system. This innovative system is suitable for small-scale IES and serves as an efficient solution for urban energy systems.

Optical and electrical performance of an agrivoltaic field with spectral beam splitting

Solar photovoltaic power generation is a mature and competitive technology, but its high land area requirements conflict with other uses of available land. Agrivoltaics (APV) allows dual use of land, with photovoltaic panels installed over agricultural crops. However, the panels block a significant portion of the solar radiation, leading in many cases to a severe reduction in growth and productivity of the agricultural crop. Here, we present a novel type of collector to resolve this competition between electricity and crop yields by spectral splitting of the incident direct radiation using simple planar components. Photosynthetically active radiation (PAR) is transmitted to the crop while near-infrared radiation (NIR) is directed to the PV panels. The annual optical and electrical performance of a large-scale agrivoltaic field with these spectrum-splitting collectors is investigated in detail. The study is conducted using a computational model that includes optics, heat transfer, and electrical conversion. The reliability of the model was validated using experimental data obtained from a small-scale experimental setup. Results show that the electricity production per unit land area of the spectrum-splitting collectors can be similar to that of conventional APV fields and may reach even higher value by about 20% with optimized spectral splitters. According to the simulations, the loss of PAR on the ground due to the collectors may be significantly reduced, reaching only 10% compared to 21% in a conventional APV field.

The Role of Solar Spectral Beam Splitters in Enhancing the Solar-Energy Conversion of Existing PV and PVT Technologies

The use of photovoltaics (PVs) and/or photo-thermal (PTs) as primary solar-energy solutions is limited by the low solar conversion of PVs due to the spectral mismatch between the incident radiation and/or the PV material. The PTs are curtailed by the limited absorbance and the low thermal conductivity of the working fluid. A possible solution is the use of luminophores able to perform luminescent down-shifting (LDS) conversion and to incorporate them in liquid or solid layers, which act as spectral beam splitters (SBSs). Dispersed in solid polymer layers, luminophores lead to luminescent solar concentrators (LSC). When dispersed in liquid and placed in front of PVs, luminophores act as working fluids and as SBS, leading to hybrid photovoltaic–photo-thermal (PVT) systems. Here, the SBS filters for PV and PVT systems are reviewed. The contribution of luminophores to electrical and thermal energy production is discussed from theoretical, experimental, and economical perspectives. Recent SBS architectural concepts which combine different optical elements are also considered. These architectures can harness the advantageous properties of LSCs, spectral modulators, and hybridisation in a single structure. By combining these different light-management strategies inside of a single structure, an improvement in the electrical and/or thermal energy production can be achieved.

Thermal modulation of radiation fields enhancing the adaptability of CPV-Hydrogen systems to hot outdoor conditions

Photovoltaic (PV) coupled with water electrolysis (EC) provides a clean and reliable hydrogen supply. However, commercial PV often undergo severe performance degradation under high temperature outdoor conditions. In this work, we report a novel thermally integrated concentrated PV-EC system using a pipeline-based liquid spectral beam splitting (SBS) filter as the electrolyte preheater. Unlike previous designs where heat is collected on the backside of the PV, the liquid-filled tubular SBS filter effectively modulates solar irradiation both spatially and spectrally prior to reaching the PV surface. The infrared wavelengths are absorbed by the electrolyte prior to their conversion into thermochemical losses in the PV, thereby augmenting the temperature and efficiency of electrolysis. Efficient allocation of thermal energy can simultaneously satisfy the lower temperature requirement for PV and the higher temperature demand for EC. The PV surface temperature can be decreased by as high as 23.5 K owing to this thermally integrated mode. The optimized allocation of thermal energy resulted in a notable increase in the average efficiency of photovoltaics, electrolysis, and solar hydrogen production by 7.5%, 8.1%, and 5.2% respectively. As a result, out design can significantly suppress the decreasing trend of efficiency in outdoor experiments during summer midday. The proposed system design, characterized by its simplistic structure and utilization of cost-effective materials, presents a feasible alternative for large-scale solar hydrogen production in hot outdoor environments.