Winter Solstice Day Research Articles

Theoretical analysis of upward-heating multiple-effect diffusion solar still with parabolic dish concentrator

Upward-heating multiple-effect diffusion solar still (UHMEDS) coupled with a parabolic dish concentrator (PDC) was proposed and analyzed theoretically. UHMEDS has cover glass, several partitions and preheating cover, and wicks are placed on the upper surfaces of partitions and preheating cover. Saline water preheated on the preheating cover flows down the partitions by gravitational force. The lowermost partition of UHMEDS was heated by solar energy collected by PDC. The basic behavior of UHMEDS at Fukuoka, Japan was analyzed theoretically by modeling heat and mass transfer in the still. The theoretical results show that PDC can collect the sunrays to the lowermost partition of UHMEDS effectively, and the overall daily productivity of the still was predicted to be about 18.5, 24.5 and 10.4 kg/m2day on spring equinox, summer and winter solstice days, respectively, which values are almost equivalent to those of other types of multiple-effect diffusion solar still.

Transit of sun through the seasonal nakṣatra cycle in the Vṛddha-Gārgīya Jyotiṣa

Vṛddha-Gārgiya-Jyotiṣa (VGJ) is an important text of Indian astral sciences before the astronomy texts of the Common Era. Only a few of the chapters of this text have been edited and published so far. The present paper reports an important study of two sections of this text which describe the transit of Sun along the 27 asterisms (nakṣatra) during the six seasons beginning with winter. The first section called Ādityacāra describes each season to be covered by Sun travelling 4½ asterisms starting from śraviṣṭhā nakṣatra at the beginning of śiśira ṛtu reckoned as the winter solstice day. The seasons are stated in terms of Sun transiting the beginning, middle and end of nine asterisms some of which are made of more than one star. The second section of the text known as Ṛtusvabhāva starts with the vasanta ṛtu and names twelve asterisms through which Sun transits in the 12 months of the tropical year. It is shown that the solar transit information in the Ādityacāra and the Ṛtusvabhāva chapters of VGJ can be dated, for minimum observational error, to c 1300 BCE and c 500 BCE respectively.

Design methodology of a parabolic trough collector field for maximum annual energy yield

Improving efficiency and yield of a parabolic trough collector (PTC) field is of paramount technological importance. Here, an attempt toward this goal is made through combined optical and thermal simulation. Two major factors that affect the performance of an individual trough are mass flow rate and aperture width, which scales with rim angle. Performance of PTC-field is observed to have a non-linear scale-up rule as opposed to the same for an individual trough. Wider aperture leads to higher heat collection for individual trough; however, the same results in higher inter-trough shading limiting the number of troughs in a field and the effective unshaded hours. It also depends on insolation and latitude. Therefore, there lies a possibility of trade-off where flow rate, rim angle and design hours of operation require careful tuning to maximize annual energy yield. Here, a step by step procedure is demonstrated for Kanpur, India where optimal values of flow rate, rim angle and hours of operation are obtained to be 1.1 kg/s (for Syltherm 800 as the heat transfer fluid), 70° and 4 h around solar noon on winter solstice day, respectively. The methodology is illustrated to be generally applicable to any location or working fluid.

Study and Analysis on the Thermal Environment Test in Guanzhong Farm Residential in Winter

Rural residences in Guanzhong area have suffered from poor indoor thermal environment and backward energy-saving methods for a long time in winter. In order to study the local thermal environment, improve residents’s thermal comfort in winter and reduce building energy consumption. The research team conducted a typical winter solstice day Conduct thermal environment test and field survey on typical residential buildings in Guanzhong area, and quantify the test data to get the results: 1. Local solar energy resources have a certain potential. 2. The indoor thermal environment is severely humid and cold so that thermal comfort is low. 3. The first floor of residential buildings can basically meet thermal comfort requirements. According to the results of energy consumption calculations, Guanzhong’s farm buildings consume too much energy. In response to the national energy conservation and emission reduction policy, some improvement measures are needed to improve the atmospheric environment. Taking into account the local climate adaptability, residents’ living habits and economic conditions, measures are proposed to reduce the area of the north window by a certain percentage, install additional sunshine rooms, and transform the second floor south to a balcony.

A Comparative Study on Daylight Performance Assessment of Light Shelves Based on Inclination

Energy consumption of lighting can be reduced by using different daylight control strategies. The rise in environmental distresses requires the necessity of natural light control systems. Light shelf is considered as excellent lighting control scheme that provides great lighting production and inexpensive prospect via entering the daylight inside the space. The aims of this study shows that the daylight efficiency and visual productivity are affected by the design parameters of light shelf such as its angle, location and height. In this research, Autodesk Ecotect 2011 is used for the daylight simulation of summer solstice and winter solstice days under overcast sky conditions on a nominated theoretical study space of an institutional building. Daylight simulation is carried out to evaluate the illuminance requirement within the selected space and analysis is also executed on the model with selected categories of light shelves including different positions, heights and angles. The acquired data is then exported on Radiance software intended for complete day-light investigation. The results of this research shows that external light shelf at a height of 7' and an angle of 20˚ is the most appropriate choice in prevailing the glare and it also enhanced the illuminance level to11.5% in 21st June and 10.6% in 21st December as compared to without light shelves. Furthermore, the shaded range is decreased by the rise in the angle of Light shelf which has a tendency to increase the inside average lighting. Hence, significant consideration should be given to the height and position of light shelves, since it has a superior effect on light shelf performance.

Методика оценивания эффективности применения орбитальных систем малых космических аппаратов оптико-электронного наблюдения

The paper presents the results of analysing existing approaches to estimating how efficient small orbital spacecraft systems are for the purpose of optoelectronic surveillance, including determining their shortcomings. We simulated employing an orbital system required to ensure surveying the earth surface at various latitudes, accounting for sunrise and sunset time on the winter and summer solstice days, and discovered that the following parameters show low sensitivity: average daily object sighting number at a preset latitude and maximum time delay between object sightings at a preset latitude. We propose a new efficiency factor reflecting a confidence interval regarding the object sighting time delay. We developed a procedure utilising the factor proposed, expanding the scientific methodology in terms of estimating how efficient small orbital spacecraft systems are for optoelectronic surveillance. We obtained object sighting time delays at a preset latitude as functions of the probability of these delays occurring. We recommend using this procedure to estimate the efficiency of jointly employing several small orbital spacecraft systems and incomplete composition systems, as well as to state and solve the problem of synthesising the ballistic structure of an orbital system intended to improve the efficiency of earth surveillance.

Analysis of thermal energy storage system for energy saving reconstruction of building in region with heating provision and high sunshine

This research aims to analyze the effect of phase change energy storage wall on the internal thermal environment in high-sunshine passive solar residential buildings. The residential buildings in Lhasa are taken as research objects, and the differences in indoor and outdoor thermal environments of the residential buildings in winter are first evaluated. Then, the energy storage wall model based on phase change material is constructed, the meteorological data of the winter solstice day is used to simulate, and the changes of the thermal environment in the room are detected. The results showed that the average solar radiation intensity of the dwellings in Lhasa is 441.8 W/m2, and the average scattering intensity is 156.3 W/m2. The average humidity and temperature of outdoor air are 24.4% and 1.54?C, respectively. The temperature difference of the indoor south and north bedrooms is 3.3?C, the internal temperatures of the indoor south and north walls are 13.4?C and 7.9?C, respectively, and the temperature difference is 5.5?C. After the adoption of phase change energy storage materials, the indoor temperatures of the south and north walls on the winter solstice day are 16.75?C and 16.52?C, respectively, with a temperature difference of 0.23?C. The inner surface temperatures of the south wall and the north wall increase by 25.0% and 109.1%, respectively, after adopting the phase change energy storage wall, indicating that applying the phase change energy storage wall to the passive solar residential buildings in Lhasa can effectively improve the indoor thermal environment.

Estimation of Energy Saving in Educational Building from Day lighting to Improve the Visual Comfort

Daylight is the occupied-range of light that is appropriate to the human visual response. Thus, it can contribute to human health, performance and productivity. Energy consumption can be reduced by improving in energy efficiency. The study emphaseson the design of lighting system that will be energy efficient. The basic purpose of this paper describes how to reduce the mounted lighting load and improve the illumination level as per international standards. A good lighting scheme should be based on more energy efficient & longer life and maintenance free equipment. In this research paper,a hypothetical study space is selected for the daylight analysis on the Ecotect and the Radiance software on summer solstice and winter solstice days under over cast sky condition. Ecotect software is used to determine lighting demand inside the selected study space and the obtained data is exported on Radiance for detailed and more accurate daylight analysis. It is pragmatic that illuminance level is varied with respect to date and time that are clearly expressed by the daily sun path and shadow range. It is also perceived that the installed artificial luminaries does not provide the required illuminance on the working plane and consume more energy. The major aim of this research is to reduce the lighting load by introducing energy efficient artificial luminaries into the room that provide the required illuminance level on the working plane. Lumen method is used to explain the energy saving which is carried out according to existing energy consumption compared with the proposed one. At the end cost comparison of energy consumption and payback period is also calculated. This study shows that overall cost saving in energy consumption is approximately 34.37% and the calculated payback period for the newly installed lights is comprising of approximately 11 months.

Transactive control of a residential community with solar photovoltaic and battery storage systems

Transactive energy is a two-way exchange of energy between the electric power grid and a community’s distributed energy resources, offering opportunities for efficiency improvements through market-based economic and control techniques. A community’s distributed energy resources include electricity-producing resources and controllable loads. Increased usage of unsynchronized generation of non-dispatchable solar photovoltaic energy and household demand at the community level can adversely affect the power quality, reliability and network balancing of the electricity grid. A solution was developed in this paper in the form of energy storage and demand side management on a solar residential community. An agent-based transactive energy management system was developed and simulated using multiple prosumer houses with roof-top PV systems and local energy storage. Experimental work conducted on an archetype house, near Toronto, Ontario, Canada, was used to model an all-electric residential house and clusters were created with varying orientations and building properties to mimic different efficiency levels of the houses within the virtual community. A machine learning algorithm using historical data and weather forecasts from Natural Resources Canada (NRCan) was used to forecast the community’s energy generation as well as building’s thermal loads. In this community, consumers can curtail their loads based on price signals sent to smart devices in homes. Open-loop mixed integer linear programming technique (MILP) and model predicted control (MPC) were compared and evaluated. The simulation shows promising results with a 9% energy savings during the summer solstice day and 5% during the winter solstice day when compared to the normal operation of houses’ mechanical equipment.

Determination of optimal inclination function for external reflector of basin type still for maximum distillate productivity

Abstract A basin type solar still design problem is examined in the present work and the Levenberg-Marquardt Method is utilized to estimate the optimal inclination function for external reflector to obtain maximum daily distillate productivity. The design algorithm is to estimate the optimal design variables of inclination function for external reflector. Four different designs for time-dependent inclined angle of external reflector from vertical will be considered in the present study, and the resultant daily amount of distillate of the solar still for each design will be examined. Results indicate that using case 1 design the daily amount of distillate of the still would be about 27.8% greater than that with the vertical external reflector, and about 2.38 times as large as that of the still without the reflectors on a winter solstice day. The daily amount of distillate with case 2 design would be about 1.72% greater than that with case 1 design on a winter solstice day and the productivity of distillate is almost the same for case 2, case 3 and case 4 designs. The fact indicates that case 2 design should be recommended for use to produce the distillate of the solar still.

STELA D: A SUNDIAL AT COPAN, HONDURAS

AbstractThe Maya of Copan, Honduras used Stela D, its altar, and the surrounding structures as a sundial to record time. Archaeological investigations show that wooden posts and stelae could have been used to measure time and to perform associated rites in the northern sector of the Main Plaza of the Copan Archaeological Park. We constructed a digital model of Stela D to study the shadows cast at different times of day and on different dates of the year, such as solstices, equinoxes, and solar zenith passages. The size and orientation of the shadows may have served as a time marker that ancient residents of Copan used to accurately track the tropical year. We also found evidence that supports the iconographic interpretation of an analogy between serpents’ bodies that adorn the figure of the ruler on Stela D and shadows and sun positions on dates of major solar events that form a solar calendar that counts years from winter solstice day.

Effects of Aspect Ratio on Average Daily Shading Factor of Flat-Plate Solar Collector Array in Winter Months

A model to calculate daily shading factor of flat-plate solar collector array installed on the limited horizontal roofs has been developed. The relations between the latitude, the average daily shading factor, the floor area, and the aspect ratio of the collector array have been deeply studied. The results show that the average daily shading factor on winter solstice day increases with the increase of the latitude and aspect ratio. For a given latitude, the average daily shading factor of a collector array (floor area ≥ 500 m 2) increases linearly with the increase in the aspect ratio within a range of [1/10, 3/1] and increases smoothly with the aspect ratio ranging from 3/1 to 10/1. The average daily shading factors do not exceed 0.085 for the low latitude regions (lat. ≤ 30o N), whereas the maximum average daily shading factors for a 1000m 2 collector array can reach 0.140 when the latitude is close to 40o N.

Refractoriness to short and long days determines the end and onset of the breeding season in subtropical goats

The objective was to determine whether refractoriness to short and long days were involved in the end and onset of the breeding season, respectively, in goats adapted to subtropical latitudes. Ovariectomized does given a subcutaneous implant constantly releasing estradiol-l7 β (OVX+E) were used in two experiments. Plasma LH concentrations were determined twice weekly. In Experiment 1, the control group remained in an open-shed pen (natural day length and ambient temperature). Two experimental groups were placed in light-proof buildings (with natural temperature variations). One group was exposed to natural simulated increasing days (winter to spring), whereas the other was exposed to a winter solstice photoperiod (10 h of light) from December 21 to April 28. In Experiment 2, the control group remained under natural day length and ambient temperature. One experimental group was exposed to natural simulated decreasing days (summer to autumn), whereas the other group was exposed to a summer solstice photoperiod (14 h of light) from June 21 to October 20. In Experiment 1, the breeding season was not prolonged in does maintained in the winter solstice day length. Mean dates of decrease in LH secretion (end of the breeding season) did not differ significantly between does exposed to natural (February 3 ± 5 d) or natural simulated photoperiod (January 26 ± 14 d) and those exposed to constant short days of winter solstice (February 4 ± 10 d). In Experiment 2, the onset of the breeding season was not delayed in does maintained in the summer solstice day length. Mean dates of increase in LH secretion (onset of the breeding season) did not differ significantly between does exposed to natural (September 7 ± 8 d) or natural simulated photoperiod (September 18 ± 10 d) and those exposed to constant long days photoperiod of summer solstice (September 24 ± 4 d). In goats adapted to a subtropical environment, we concluded that: 1) the end of breeding season was due to refractoriness to short days, and not the inhibitory effect of increasing day length; and 2) the onset of the breeding season was due to refractoriness to long days, and not a stimulatory effect of decreasing day length.

Increase in distillate productivity by inclining the flat plate external reflector of a tilted-wick solar still in winter

This paper presents a theoretical analysis of a tilted-wick solar still with an inclined flat plate external reflector on a winter solstice day at 30°N latitude. The daily amount of distillate of a still with an inclined reflector would be about 15% or 27% greater than that with a vertical reflector when the reflector’s length is a half of or the same as the still’s length.

One step azimuth tracking tilted-wick solar still with a vertical flat plate reflector

This paper presents a theoretical analysis of a one step azimuth tracking tilted-wick solar still with a vertical flat plate reflector. The still is assumed to be rotated manually just once a day at southing of the sun. We performed numerical analysis of heat and mass transfer in the still to determine the distillate productivity of the still on four typical days: the spring and autumn equinox and summer and winter solstice days at 30°N latitude. We theoretically determined the optimum tilt angle of the still and the optimum orientation of the still on these four days. We also found that the increase in the daily amount of distillate of a tilted-wick still would average about 41% for four days, and can be achieved by the simple modification of using a flat plate reflector, setting the still at proper tilt angle according to seasons and rotating the still just once a day.

Improvement of the tilted wick solar still by using a flat plate reflector

This paper presents a numerical analysis to investigate the effect of the vertical flat plate external reflector on the distillate productivity of the tilted wick solar still. We propose a geometrical method to calculate the solar radiation reflected by the external reflector and absorbed on the evaporating wick, and also performed numerical analysis of heat and mass transfer in the still to predict the distillate productivity on four days (spring and autumn equinox and summer and winter solstice days) at 30°N latitude. We found that the external reflector can increase the distillate productivity in all but the summer seasons, and the increase in the daily amount of distillate averaged over the four days is predicted to be about 9%.

Effect of inclination of external flat plate reflector of basin type still in winter

This paper presents a theoretical analysis of a basin type solar still with an internal reflector (two sides and back walls) and an inclined flat plate external reflector on a winter solstice day at 30° N latitude. We are proposing a new geometrical method for calculating the solar radiation reflected by the inclined external reflector and then absorbed on the basin liner. Using this method, we performed a numerical analysis of heat and mass transfer in the still in order to determine the effectiveness of the inclination of the external reflector. We found that the benefit of a vertical external reflector would be smaller or even negligible for a still with a larger value for the glass cover angle, while an inclined external reflector can increase the distillate productivity of the still at any glass cover angle, and the external reflector angle should be set at about 15° from vertical on a winter solstice day. The daily amount of distillate of the still with the inclined external reflector would be about 16% greater than that with the vertical external reflector, and about 2.3 times as large as that of the still with neither the internal nor the external reflector on a winter solstice day.

A simple and highly productive solar still: a vertical multiple-effect diffusion-type solar still coupled with a flat-plate mirror

This paper presents a newly designed simple solar still: a vertical multiple-effect diffusion-type solar still consisting of a flat-plate mirror, a number of vertical parallel partitions in contact with saline-soaked wicks with narrow air gaps between partitions, and casters for azimuth tracking by human power. The proposed still is designed so that non-skilled persons can construct it with common materials in developing countries. We theoretically analyzed the dependence of the solar absorption on the first (or heated) partition on the angle of the flat-plate mirror and the azimuth angle of the still, and found that the solar absorption on the first partition can be significantly increased by rotating the still at southing of the sun just once a day, and the daily solar absorption would be about 85% or 99% of the daily solar radiation on a horizontal surface on the spring equinox or winter solstice, respectively. We also theoretically analyzed the heat and mass transfer in the proposed still, and found that a proposed still of 10 partitions with 10 mm diffusion gaps between partitions was predicted to produce 29.2 34.5 kg/m 2d on sunny spring equinox and winter solstice days respectively at the equator.

Parametric study on a vertical multiple-effect diffusion-typesolar still coupled with a heat-pipe solar collector

A parametric investigation was theoretically performed for the vertical multiple-effect diffusion-type solar still, which consists of a number of vertical partitions in contact with saline-soaked wicks with narrow gaps between the partitions, coupled with a heat-pipe solar collector. The proposed still has some advantages: the still's size is compact, the still can produce distilled water without electricity, and the productivity is greater than that of conventional multiple-effect diffusion-type solar stills. We theoretically predicted the optimum angle of the solar collector on the spring and autumn equinox and the summer and winter solstice days, and also performed parametric investigations of the design and operation conditions; it was found that productivity increased with an increase in the number of partitions and the temperature of the saline water fed to the wicks, and with a decrease in the ratio of the solar collector area to each partition area, the thickness of the diffusion gaps between partitions, and the feeding rate of saline water to the wicks.

Termination of the breeding season in the Suffolk ewe: involvement of an endogenous rhythm of reproduction.

Two studies were performed to determine if the transition into anestrus in the Suffolk ewe results from the lack of a decrease in photoperiod, a signal suggested to be important in maintaining the breeding season, or from an obligatory turn-off that reflects the expression of an endogenous rhythm of reproduction. Shortly after the autumnal equinox, three groups of ovariectomized ewes bearing s.c. Silastic implants of estradiol were placed in different lighting environments. A control group was exposed to normal variations in day length until the winter solstice and held on that day length thereafter. The two experimental groups experienced either a continuously decreasing day length or a continuously increasing duration of elevated melatonin levels during each 24-h period until mid-March. Reproductive activity, assessed by circulating levels of luteinizing hormone (LH), was marginally extended (2-3 wk) in the experimental groups. In a second experiment, two groups of ovary-intact ewes were exposed to photoperiodic treatments shortly after the winter solstice. A control group was held on the winter solstice day length (10L:14D) until the end of the study in mid-March. The experimental group experienced a 3-h photoperiodic reduction to 7L:17D. It remained to determine if that abrupt decrease could maintain reproductive induction. Again, the cessation of reproductive induction was marginally delayed in the experimental group (2-3 wk). This marginal delay in the arrest of reproductive activity seen in both experiments indicates that the lack of decrease in day length around and after the winter solstice may play some role in timing the end of the breeding season. However, our inability to prevent or markedly delay the termination of reproductive activity leads to the conclusion that the primary reason for the transition into anestrus is an obligatory turn-off. This obligatory process may be the expression of an underlying endogenous rhythm of reproduction.