Sunlight Intensity Research Articles

The Moderating Effects of Urban Design on Willingness to Walk in a Tropical City

Walkability and the willingness to walk (WTW) are enhanced with supportive urban design in temperate climate cities. Walking in a tropical city is challenged by the physiological stresses brought on by high air temperature, intense sunlight and humidity but it remains unknown to what extent urban design compensates for these stressors in walking behaviour. In this study, the relative impacts of the walking environment and microclimate on WTW and on walking distance were measured in a field study in Singapore. Participants executed a planned walk and reported assessments of 10 environmental factors, as well as WTW, at assigned locations. Restoration in WTW was observed at certain points on the itinerary across participants, while total voluntary walked distance equalled that of an indoor, air-conditioned walk at the same location. All environmental design variables showed a positive relationship with WTW, but not with objectively measured temperature and humidity. Urban design has a significant impact on willingness to walk in a tropical city.

Machine Learning Approaches for Short-Term Photovoltaic Power Forecasting

A photovoltaic (PV) power forecasting prediction is a crucial stage to utilize the stability, quality, and management of a hybrid power grid due to its dependency on weather conditions. In this paper, a short-term PV forecasting prediction model based on actual operational data collected from the PV experimental prototype installed at the engineering college of Misan University in Iraq is designed using various machine learning techniques. The collected data are initially classified into three diverse groups of atmosphere conditions—sunny, cloudy, and rainy meteorological cases—for various seasons. The data are taken for 3 min intervals to monitor the swift variations in PV power generation caused by atmospheric changes such as cloud movement or sudden changes in sunlight intensity. Then, an artificial neural network (ANN) technique is used based on the gray wolf optimization (GWO) and genetic algorithm (GA) as learning methods to enhance the prediction of PV energy by optimizing the number of hidden layers and neurons of the ANN model. The Python approach is used to design the forecasting prediction models based on four fitness functions: R2, MAE, RMSE, and MSE. The results suggest that the ANN model based on the GA algorithm accommodates the most accurate PV generation pattern in three different climatic condition tests, outperforming the conventional ANN and GWO-ANN forecasting models, as evidenced by the highest Pearson correlation coefficient values of 0.9574, 0.9347, and 0.8965 under sunny, cloudy, and rainy conditions, respectively.

Quantifying the flexural stiffness changes in the concrete beams with externally bonded carbon fiber sheets under elevated environment temperature

Structural strengthening solutions typically employ externally bonded reinforcement (EBR) systems with carbon fiber (CF) sheets because of these materials’ lightweight, corrosion resistance, and electromagnetic immunity. However, elevated ambient temperatures can negatively impact the mechanical performance of EBR, as documented in the literature. Therefore, American bridge design specifications assume a concrete surface temperature of 60 °C (140 °F), which reflects the extreme conditions that bridge structures may experience, particularly in regions with intense sunlight and high ambient temperatures. Therefore, sustainable design solutions require a reliable quantification of the effects of temperature. This study extends a recently developed bending test layout and builds the analytical modeling procedure to quantify the stiffness degradation under repeated temperature and mechanical loads. The explicitly obtained equivalent stresses in the tensile concrete determine the stiffness measure independent of the loading condition and sequence. This test program used 12 laboratory samples. All beam samples faced the mechanical load repetitions and entire unloading. Three selected beams were additionally treated at 60 °C for 10 hours in a heating chamber between the loading repetitions. These tests identified a substantial (three times) decrease in the bonding performance of the CF sheets after eight heating rounds. Scanning electron microscopy (SEM) identified the corresponding microstructure changes.

Bidirectional Energy Flow in the Photosystem II Supercomplex.

The water-splitting capability of Photosystem II (PSII) of plants and green algae requires the system to balance efficient light harvesting along with effective photoprotection against excitation in excess of the photosynthetic capacity, particularly under the naturally fluctuating sunlight intensity. The comparatively flat energy landscape of the multicomponent structure, inferred from the spectra of the individual pigment-protein complexes and the rather narrow and featureless absorption spectrum, is well known. However, how the combination of the required functions emerges from the interactions among the multiple components of the PSII supercomplex (PSII-SC) cannot be inferred from the individual pigment-protein complexes. In this work, we investigate the energy transfer dynamics of the C2S2-type PSII-SC with a combined spectroscopic and modeling approach. Specifically, two-dimensional electronic-vibrational (2DEV) spectroscopy provides enhanced spectral resolution and the ability to map energy evolution in real space, while the quantum dynamical simulation allows complete kinetic modeling of the 210 chromophores. We demonstrate that additional pathways emerge within the supercomplex. In particular, we show that excitation energy can leave the vicinity of the charge separation components, the reaction center (RC), faster than it can transfer to it. This enables activatable quenching centers in the periphery of the PSII-SC to be effective in removing excessive energy in cases of overexcitation. Overall, we provide a quantitative description of how the seemingly contradictory functions of PSII-SC arise from the combination of its individual components. This provides a fundamental understanding that will allow further improvement of artificial solar energy devices and bioengineering processes for increasing crop yield.

Chitosan-azo dye bioplastics that are reversibly resoluble and recoverable under visible light irradiation.

Biopolymer composite materials were prepared by combining bio-sourced cationic water-soluble chitosan with bi-functional water-soluble anionic azo food dyes amaranth (AMA) or allura red (ALR) as ionic cross-linkers, mixing well in water, and then slow-drying in air. The electrostatically-assembled ionically-paired films showed good long-term stability to dissolution, with no re-solubility in water, and competitive mechanical properties as plastic materials. However, upon exposure of the bioplastics to low power light at sunlight wavelengths and intensities stirring in water, the stable materials photo-disassembled back to their water-soluble and low-toxicity (edible) constituent components, via structural photo-isomerization of the azo ionic crosslinkers. XRD, UV-vis, and IR spectroscopy confirmed that these assemblies are reversibly recoverable and so can in principle represent fully recyclable, environmentally degradable materials triggered by exposure to sunlight and water after use, with full recovery of starting components ready for re-use. A density functional theory treatment of the amaranth azo dye identified a tautomeric equilibrium favouring the hydrazone form and rationalized geometrical isomerization as a mechanism for photo-disassembly. The proof-of-principle suitability of films of these biomaterial composites as food industry packaging was assessed via measurement of mechanical, water and vapour barrier properties, and stability to solvent tests. Tensile strength of the composite materials was found to be 25-30 MPa, with elongation at break 3-5%, in a range acceptable as competitive for some applications to replace oil-based permanently insoluble non-recyclable artificial plastics, as fully recyclable, recoverable, and reusable low-toxicity green biomaterials in natural environmental conditions.

Polypyrrole-mediated construction of superhydrophobic photo/electro thermal composite fabric for efficient crude oil dehydration and recovery

During crude oil extraction, transportation, and oil spill recovery, rapid and effective removal of water from crude oil is a great challenge. Super-hydrophobic functional membranes with electrothermal/photothermal effects are considered to be an effective method. However, simply polymerizing photothermal/electrothermal nanomaterials on the membrane surface will lead to unstable thermal effects and easy shedding. Therefore, in this study we propose the synthesis of a novel superhydrophobic electrothermal/photothermal Nylon fabric (PSPPNF) by an innovative in situ polymerization method of Pyrrole (Py), to realize efficient viscosity reduction and dehydration of crude oil. In particular, by controlling FeCl3 solution from solid (−18 °C) to liquid state (0 °C), Py was polymerized on the fabric surface by slow oxidative process, which can effectively solve the problem of pore blocks to obtain a stable-conductive layer on the NF surface. The PSPPNF surface temperature can reach 80 °C under 1 kW m−2 sunlight intensity or by inputting 30 V, which brings a separation efficiency of 97 % for high-viscous crude oil/water mixture. We systematically analyzed the effects of PSPPNF with different pore sizes and oils with different viscosities on the separation flux, as well as the effects of the thermal properties of the membranes under different illumination conditions and voltages on crude oil permeation. Additionally, the PSPPNF combined with the roller can realize all-weather available crude oil spill recovery under solar and electrical energy. This work provides new insights into membrane materials that can realize the efficient dehydration and recovery of crude oil for day-night alternation and complex environments.

Growth and Yield of Two Mustard Varieties (Brassica Juncea L.) at Various Shading Levels

Mustard greens are one of the vegetable commodities plants. The part used is the young leaves, which can be processed into traditional medicinal and vegetable ingredients that benefit human health. This research aims to determine the level of shade tolerance on the growth and yield of mustard plants and determine mustard varieties that are tolerant of minimum sunlight conditions. This research was carried out in experimental fields using artificial fields in June – July 2023. This research used a split-plot design with 2 factors. Tafif shade as the main plot consists of no shade 0%, 55%, 70%, and 95%. The sub-plot varieties consist of the Tosakan variety and the Kumala variety. The results of the research indicate that sunlight intensity reduction negatively impacted the growth and yield of mustard plants. However, under 55% shade conditions, there was no significant difference observed in the growth and yield of mustard plants compared to those grown without shade. The Tosakan and Kumala varieties did not show any differences in the growth or yield of mustard plants.

Growth and Yield of Two Mustard Varieties (Brassica Juncea L.) at Various Shading Levels

Mustard greens are one of the vegetable commodities plants. The part used is the young leaves, which can be processed into traditional medicinal and vegetable ingredients that benefit human health. This research aims to determine the level of shade tolerance on the growth and yield of mustard plants and determine mustard varieties that are tolerant of minimum sunlight conditions. This research was carried out in experimental fields using artificial fields in June – July 2023. This research used a split-plot design with 2 factors. Tafif shade as the main plot consists of no shade 0%, 55%, 70%, and 95%. The sub-plot varieties consist of the Tosakan variety and the Kumala variety. The results of the research indicate that sunlight intensity reduction negatively impacted the growth and yield of mustard plants. However, under 55% shade conditions, there was no significant difference observed in the growth and yield of mustard plants compared to those grown without shade. The Tosakan and Kumala varieties did not show any differences in the growth or yield of mustard plants.

Tuning effect and switching behavior of sunlight field on lateral photovoltaic effect of Zn0.95Cu0.05O/p-Si heterojunction

In this paper, the Zn0.95Cu0.05O/p-Si heterojunction with lateral photovoltaic effect (LPE) is prepared that has the tuning effect and switching behavior of sunlight field. The dependence of the lateral photovoltage (LPV) on the laser position shows high sensitivity (20 mV mm−1) and strict linearity. Interestingly, the LPV eventually decreased to 0 mV as the sunlight intensity increased to 48 mW, under the constant laser intensity and position, indicating the application potential of a photo-switch. This light field effect results from the irradiation of sunlight, which changes the position of quasi-Fermi level, reduces the drive power for carriers by the space charge region in the heterojunction, and increases the concentration of carriers resulting in increased the scattering between carriers to decrease the lifetime of carriers produced by the laser. This work can expand the application of LPE in the field of multifunctional devices such as photo-switches, position sensors and self-powered devices.

Smartwatch Measures of Outdoor Exposure and Myopia in Children

Time spent outdoors has been proven effective in preventing myopia, but little is known about the association of outdoor exposure patterns with myopia. To examine the association of outdoor exposure patterns with myopic shift in children. This 1-year prospective cohort study from December 2017 to December 2018 was a secondary analysis of a cluster-randomized trial (Shanghai Time Outside to Reduce Myopia [STORM]). STORM was a school-based intervention study, recruiting 16 schools from 8 districts in Shanghai, from October 2016 to December 2018. Children without myopia at baseline who consistently wore a smartwatch for a minimum of 6 hours daily, sustained for at least 90 days, and who had complete information were included. Data analysis was performed from December 2017 to December 2018. The outdoor exposure pattern was defined as the episode of time outdoors and instant sunlight intensity over a continuous period. Myopic shift was defined as the absolute change in refraction between the initial spherical equivalence and the follow-up spherical equivalence. This study included 2976 students (mean [SD] age, 7.2 [0.6] years; 1525 girls [51.2%]). The mean (SD) daily time outdoors was 90 (28) minutes, and the mean (SD) sunlight intensity was 2345 (486) lux. Of the 12 outdoor exposure patterns, the major outdoor exposure patterns were time outdoors with at least 15 minutes, accounting for 74.9% of minutes (33 677 584 of 45 016 800 minutes). Only patterns with at least 15 minutes accompanied with no less than 2000 lux were associated with less myopic shift in refraction (for ≥15 minutes and 2000 to 3999 lux, -0.007 diopter [D] [95% CI, -0.011 to -0.002 D]; for ≥15 minutes and ≥4000 lux, -0.006 D [95% CI, -0.010 to -0.002 D]). The isotemporal substitution of patterns with at least 15 minutes and 2000 lux for other outdoor exposure patterns was positively associated with less myopic shift. In this 1-year prospective cohort study of children with smartwatches, continuous outdoor exposure with at least 15 minutes accompanied with no less than 2000 lux sunlight intensity was associated with less myopic shift. These findings suggest that future outdoor interventions should focus not only on the overall time outdoors but also on the effective outdoor exposure patterns, as a means to effectively prevent myopia in children.

Internet of things-based rice field irrigation evaporation monitoring system

The urgency for efficient irrigation in Indonesia’s agriculture sector, particularly in paddy fields, is evident. However, existing methods for monitoring water levels are antiquated, often requiring manual measurements with a ruler. This research introduces a comprehensive “monitoring system for light intensity and water temperature as an analysis of evaporation for rice irrigation based on the internet of things”. The system integrates various sensors an anemometer for wind speed, an ultrasonic sensor for water level, a DS18B20 waterproof sensor for water temperature, and a GY-8511 sensor for sunlight intensity. All data are collected by an Arduino Mega controller, connected to an ESP32 for transmitting the readings to the Blynk app and an I2C 20×4 liquid crystal display (LCD) screen. The control mechanism employs a closed-loop system with a direct current (DC) motor actuator to operate the water gate, which can also be manually controlled via a cellphone. The system effectively meets daily evapotranspiration requirements of 1.44 mm, with optimal conditions yielding water levels of 3 cm, water temperatures of 38.53 °C, sunlight intensity of 4.59 mW/cm², and wind speed of 0.21 m/s.

The Orange Carotenoid Protein Triggers Cyanobacterial Photoprotection by Quenching Bilins via a Structural Switch of Its Carotenoid.

Cyanobacteria were the first microorganisms that released oxygen into the atmosphere billions of years ago. To do it safely under intense sunlight, they developed strategies that prevent photooxidation in the photosynthetic membrane, by regulating the light-harvesting activity of their antenna complexes-the phycobilisomes-via the orange-carotenoid protein (OCP). This water-soluble protein interacts with the phycobilisomes and triggers nonphotochemical quenching (NPQ), a mechanism that safely dissipates overexcitation in the membrane. To date, the mechanism of action of OCP in performing NPQ is unknown. In this work, we performed ultrafast spectroscopy on a minimal NPQ system composed of the active domain of OCP bound to the phycobilisome core. The use of this system allowed us to disentangle the signal of the carotenoid from that of the bilins. Our results demonstrate that the binding to the phycobilisomes modifies the structure of the ketocarotenoid associated with OCP. We show that this molecular switch activates NPQ, by enabling excitation-energy transfer from the antenna pigments to the ketocarotenoid.

Hourly impact of urban features on the spatial distribution of land surface temperature: A study across 30 cities

Global warming and the urban heat island effect exacerbate excessive heat in urban environments, adversely impacting human health. Effective urban planning can mitigate these effects by influencing land surface temperature (LST). While previous studies have examined the influence of urban features on LST across seasons and between day and night, detailed hour-by-hour comparisons remain unexplored. This study addresses this gap by analyzing the hourly impacts of various urban features on LST in 30 U.S. cities using geostationary weather satellite data. We employed cloud-based analytics and machine learning techniques to aggregate data from thousands of images, identifying the relative importance and correlation curve of each urban feature on LST at each hour. Our findings revealed two distinct correlation patterns: dynamic daytime patterns with significant hourly variability and stable nocturnal patterns with minimal hourly differences. These results demonstrate that sunlight intensity greatly affects the correlation between urban features and LST. Urban planners should therefore consider broader patterns rather than focusing on specific hours. These insights provide valuable guidance for landscape and urban planners in developing strategies for climate adaptation and heatwave mitigation, contributing to the growing body of literature on sustainable cities.

Ultra-high solar steam generation based on regulated water management strategy in 3D biomass hydrogels inspired by the “binding effect” of cell walls

Facing the global challenge of water scarcity, solar-driven seawater desalination has been emerged as a green, non-polluting and sustainable technology, but the practical application of existing solar evaporators was hindered by their low evaporation efficiency and poor mechanical property. Inspired by the binding effect of cell walls, a novel and high-efficiency three-dimensional (3D) evaporator (CDs/CF/CS-LF) was constructed, in which loofah (LF) served as a natural 3D skeleton to support the hydrogel evaporator, resisted deformation, and created an efficient dual water supply mode with the chitosan (CS) hydrogel ensuring that the evaporator maintains high evaporation rate even under high salt environment. Additionally, the cellulose nanofibers (CF) filler enhanced the mechanical property of the hydrogel, ensuring shape stability under pressure impact, and carbon dots (CDs) facilitated the aggregation and cross-linking of chitosan chains through hydrogen bonds, further improving the mechanical property of the evaporator, while also enhancing the photothermal conversion capability of the 3D-CDs/CF/CS-LF evaporator as a photothermal material. The experimental results indicated that the 3D-CDs/CF/CS-LF evaporator could achieve an ultra-high solar vapor production rate of 8.08 kg m−2 h−1 under 1 sunlight intensity in 3.5 wt% NaCl solution. Outdoor seawater desalination experiments demonstrated the utility of 3D-CDs/CF/CS-LF evaporator for practical applications. This work provided a new approach for the improvement of CS-based evaporators and demonstrated their potential application in seawater desalination and purification.

Integration of photo/magnetic responsive composite phase change materials with polyurethane sponge for sustainable and efficient cleanup of crude oil spills

The efficient remediation of viscous oil spills is still a global challenge in practice due to the poor fluidity caused by their high viscosity. The adsorbents with in situ heating characteristics are regard as potential candidate for rapid and efficient crude oil spills cleanup. Although solar-assisted heating is the cleanest and most energy-efficient way, the great variation of sunlight intensity with the season and location is an obstacle to its practical application. To promote oil adsorption and enhance energy utilization efficiency, we constructed a novel adsorbent with simultaneous photo/magnetic-thermal response, and importantly phase change materials (PCMs) as thermal energy storage unit were introduced into the adsorbents. The Co/CNTs with high graphitization as efficient sunlight absorbers can significantly improve the photothermal conversion capacity of the adsorbent, resulting in rapid oil adsorption under solar illumination. Besides, benefiting from the superior magnetic response of Co particles encapsulated in the carbon skeleton, the adsorbent also enables efficient oil adsorption under alternating magnetic field. Most importantly, thanks to the cross-connected network structure of CNTs derived from the carbonization of ZIF-67, the PEG was well anchored in the Co/CNTs particles, which allows the adsorbent to store thermal energy and release heat for sustained cleanup of the oil spills when the energy input is insufficient. The adsorbent integrates with superior photo/magnetic-thermal conversion and thermal storage functions provides an innovative solution for efficient and energy-saving remediation of crude oil spills and breaks new grounds of PCMs applications.

Visible‐Light Responsive Ionic Columnar Self‐Assemblies Exhibiting Fast Photothermal Energy Conversion at Room‐Temperature

AbstractA visible‐light responsive ionic liquid crystalline (LC) system based on gallic ester and tetra‐ortho‐substituted azobenzene is designed and synthesized. All the prepared derivatives exhibit columnar hexagonal mesophases at room temperature either in their pristine form or on cooling from isotropic states. The strategic design of these molecules allows for rapid photoisomerization, which is further aided by the dynamic LC phase. These systems attains photostationary states (PSSs) within 5 min of charging and discharging. The maximum Z conversion on charging in the solid‐state at room‐temperature is ≈80% with a highest temperature rise of 9.1 °C on discharging. This new molecular design enables the efficient working of solar thermal fuels (STFs) even in low sunlight intensity conditions, potentially promoting widespread adoption for mitigating global energy demands.

Shining light on diurnal variation of non‐photochemical quenching: Impact of gradual light intensity patterns on short‐term NPQ over a day

AbstractMaximal sunlight intensity varies diurnally due to the earth's rotation. Whether this slow diurnal pattern influences the photoprotective capacity of plants throughout the day is unknown. We investigated diurnal variation in NPQ, along with NPQ capacity, induction, and relaxation kinetics after transitions to high light, in tomato plants grown under diurnal parabolic (DP) or constant (DC) light intensity regimes. DP light intensity peaked at midday (470 μmol m‐2 s‐1) while DC stayed constant at 300 μmol m‐2 s‐1 at a similar 12‐hour photoperiod and daily light integral. NPQs were higher in the morning and afternoon at lower light intensities in DP compared to DC, except shortly after dawn. NPQ capacity increased from midday to the end of the day, with higher values in DP than in DC. At high light ΦPSII did not vary throughout the day, while ΦNPQ varied consistently with NPQ capacity. Reduced ΦNO suggested less susceptibility to photodamage at the end of the day. NPQ induction was faster at midday than at the start of the day and in DC than in DP, with overshoot occurring in the morning and midday but not at the end of the day. NPQ relaxation was faster in DP than in DC. The xanthophyll de‐epoxidation state and reduced demand for photochemistry could not explain the observed diurnal variations in photoprotective capacity. In conclusion, this study showed diurnal variation in regulated photoprotective capacity at moderate growth light intensity, which was not explained by instantaneous light intensity or increasing photoinhibition over the day and was influenced by acclimation to constant light intensity.

EXPLORING THE POTENTIAL OF VEGETATION STRUCTURES (VS) AND LANDSCAPE ORIENTATION IN MINIMIZING THERMAL PERFORMANCE IN A TROPICAL CLIMATE: A FIELDWORK STUDY

The study investigates the impact of vegetation structure within two landscape orientations on thermal performance, a critical consideration in urban planning and environmental management. Given the increasing concerns about Urban Heat Islands and global warming, understanding how vegetation influences thermal regulation is essential. This research employed a quantitative method through field measurement studies, focusing on two single-storey semi-detached houses namely East Landscape Orientation (ELO) and West Landscape Orientation (WLO) located at Seri Iskandar, Perak Malaysia. The snowball technique was utilized to select the case study houses, ensuring a targeted approach to understanding the effects. Thermal Microclimate Data Logger and Indoor Air Quality Monitor Data Logger were used to measure environmental parameters for thermal conditions, ensuring consistent, reliable, and comprehensive data for analyzing thermal performance in both outdoor and indoor environments. The research findings reveal that the orientation of a house relative to the sun's path significantly impacts its thermal dynamics, with vegetation playing a crucial role in moderating these effects. ELO houses benefit from milder morning sunlight and effective afternoon cooling, while WLO houses experience higher outdoor and indoor temperatures due to intense sunlight and less efficient transpiration by vegetation. Vegetation on the west side provides shade and reduces heat absorption, improving comfort and energy efficiency. Understanding these dynamics can help homeowners and architects make informed decisions about landscape design, enhancing thermal comfort and energy efficiency in homes. This research also contributes to the expanding knowledge base on sustainable urban design by exploring the use of vegetation to enhance thermal performance.

Eco-Friendly packaging film with integrated functions of High-Efficiency radiation cooling and Sustained-Release antimicrobial activity

The storage temperature and microbial contamination typically have significant impact on the deterioration rate and postharvest lifespan of fresh food. To meet the critical requirements of fresh food packaging, a hybrid functional packaging coating is developed by combing tannic acid (TA) as a binder, chitin nanofibers (CNF) as a crosslinker, and acidified halloysite nanotubes containing Apigenin (CA@e-HNTs) as an antimicrobial/cooling agent. The functional coating was sprayed on a poly(butylene adipate-co-terephthalate) (PBAT) substrate, integrating both radiative cooling capabilities and sustained antimicrobial properties. The hybrid film achieved subambient cooling through a high solar reflectance (90.5 %) and high mid-infrared emittance (94.0 %), resulting in a temperature of 6.2 ℃ below ambient under intense sunlight. When used for fresh food packaging, the hybrid functional film outperformed other commercially available food packaging materials in maintaining the quality of Agaricus bisporus and extending the storage time of fresh strawberries to 9 days. Moreover, the film exhibited excellent antibacterial and antioxidant properties. This zero-energy cooling technology with sustained antimicrobial characteristics has enormous potential for application in the preservation of fresh food, offering a more sustainable way to extend the shelf life of fresh produce and reduce food waste.

Automatic Control of a Sunlight Reflector Board for Achieving the Sunlight Intensity Set by the Greenhouse Operator

This article proposes an autonomous greenhouse system which has a sunlight Reflector Board (RB). In general, a greenhouse, which grows leafy vegetables, utilizes artificial light, such as LED light, as a supplementary source of light. However, artificial light cannot be used as the main source of light for photosynthesis for various kinds of plants. Our article utilizes natural sunlight, instead of artificial light, for growing plants inside a greenhouse. We develop an autonomous system to control the amount of sunlight inside the greenhouse by controlling the angle of the RB, which is located in front of the greenhouse. Since the proposed greenhouse uses natural sunlight, one can grow various kinds of plants which cannot grow under artificial light. Suppose that we accumulate the RB angle data for one year. Since solar motion repeats every year, we can control the RB according to this accumulated angle data. In this way, we can reduce unnecessary RB controls, after running the system for more than a year. As far as we know, the proposed greenhouse system based on autonomous RB controls is novel, since we control RBs for providing optimal sunlight for plants inside the greenhouse. We perform experiments to demonstrate the performance of the proposed greenhouse system.