Solar Heat Load Research Articles

Performance Analysis and Design of Liquid Based Solar Heating System

Designing of a solar heating system involves appropriate sizing of different components based on predicted solar insolation and heating load demand. But, it is a complex problem due to unpredictable weather data components. A number of design methods are available for solar heating systems. In this paper, f-chart method has been used due to its simplified design procedure, analysis and low cost in selecting the sizes and type of solar collectors and in estimating the annual thermal performance of solar heating system. Using this method, the design of liquid solar heating system and the estimation of the fraction of total heating load (domestic water and space heating load) that will be supplied by solar energy for a family of six in Riyadh have been conducted. The study includes the effect of different collector areas and storage capacity per square meter of collector area and collector tilt angle on fraction of the load supplied by solar energy. It has been found that increasing the collector area results in an increasing of annual load fraction supplied by solar energy. It has also been seen that increasing the specific storage capacity results in small increase in solar load fraction and the effect is more visible during the summer than during the winter. The result of the study reveals that collector configurations with lower tilt angles are better during the summer and higher values of angles are better during the winter. The optimal annual collector configuration tilt angle which gives the maximum solar load fraction has been found to be 30o

Solar Trigeneration: a Transitory Simulation of HVAC Systems Using Different Typologies of Hybrid Panels

The high energy demand on buildings requires efficient installations and the integration of renewable energy to achieve the goal of reducing energy consumption using traditional energy sources. Usually, solar energy generation and heating loads have different profiles along a day and their maximums take place at different moments. In addition, in months in which solar production is higher, the heating demands are the minimum (hot water is consumed only domestically in summer). Cooling machines (absorption and adsorption) allow using thermal energy to chill a fluid. This heat flow rate could be recovered from solar collectors or any other heat source. The aim of this study is to integrate different typologies of solar hybrid (photovoltaic and thermal) collectors with cooling machines getting solar trigeneration and concluding the optimal combination for building applications. The heat recovered from the photovoltaic module is used to provide energy to these cooling machines getting a double effect: to get a better efficiency on PV modules and to cool the building. In this document the authors analyse these installations, their operating conditions, dimensions and parameters, in order to get the optimal installation in three different European cities. This work suggests that in a family house in Madrid, the optimal combination is to use CPVT with azimuthally tracking and absorption machine. In this case, the solar trigeneration system using 55 m 2 of collector area saves the cooling loads and 79% of the heating load in the house round the year.

Effects of adjustable and stationary fans with misters on core body temperature and lying behavior of lactating dairy cows in a semiarid climate

Cows readily seek shade to reduce solar heat load during periods of high ambient temperature. Typically, auxiliary cooling systems are oriented to maximize cooling for shaded cows. However, when a shade structure is oriented north-south, stationary fan and mister cooling systems are unable to track shade as the sun’s angle shifts throughout the day, and thus can become ineffective. The FlipFan Dairy Cooling System (Schaefer Ventilation Equipment, Sauk Rapids, MN) employs fans and misters that follow shade and compensate for wind speed by rotating on a horizontal axis. Multiparous, lactating Holstein cows (n=144) on a commercial dairy in Arizona were cooled by a fixed system comprised of stationary fans and misters acting as control or the adjustable FlipFan operated for 16.5 h/d (0830 to 0100 h). Core body temperatures (CBT) of 64 cows (4 pens/treatment; 8 cows/pen; 6d) and lying behavior of 144 cows (4 pens/treatment; 18 cows/pen; 5d) were collected by intravaginal and leg data loggers, respectively. Cows were balanced by milk production, blocked by days in milk, and randomly assigned to pen within block. Pen was the experimental unit. In a second experiment, isothermal maps were developed using a fixed system of thermal data loggers arranged in the shaded areas of the pens at different times of day and were analyzed for differences in the temperature-humidity index (THI) achieved by each cooling treatment. Ambient conditions consisted of a mean temperature of 33.0°C, mean relative humidity of 40.3%, and mean THI of 80.2. Mean 24-h CBT for FlipFan was lower than control (38.9 vs. 39.1±0.04°C). A treatment × time interaction was observed in which CBT of FlipFan was 0.4°C lower than control from 0600 to 0800h and 1500 to 1600h. Cows cooled by FlipFan spent more time lying down compared with those cooled by control (9.5 vs. 8.6 h/d). Cows under FlipFan had more frequent lying bouts than did those under control (12.8 vs. 10.7 bouts/d). Lower CBT and decreased standing time are consistent with the findings of other studies when ambient heat load was reduced. In the second experiment, the FlipFan system achieved a lower THI in the morning and evening (5.9 and 1.7%, respectively), and the THI also tended to be 0.8% lower in the afternoon compared with that of control. Results indicate that FlipFan is more effective than a stationary fan and mister system at decreasing CBT, increasing lying time and bouts, and providing a more desirable microenvironment for cows throughout the day in a semiarid environment.

305 人工日陰や屋上緑化を利用した建物日射負荷軽減に関する研究(技術と社会、環境工学)

305 人工日陰や屋上緑化を利用した建物日射負荷軽減に関する研究(技術と社会、環境工学)

Disproportionate thermophysiological strain between intensively- and extensively-managed goats during summer

Goat keeping is feasible for smallholder farmers in many world regions especially those best suited for extensive management. However, summertime grazing in arid zones entails major challenges to animal thermoregulation and well-being. An experiment was conducted to evaluate the thermoregulatory performance and selected hemogramic parameters in intensively (INT) or extensively (EXT) managed goat kids (N=14). We applied a previously established technique to evaluate body thermal state of freely ranging animals, in which contemporaneous temperatures of the core (Tc) and periphery (Tp) are chronically recorded. Animals were initially kept for 12 days under INT management. Subsequently, seven animals were transferred to a grazing pasture and gradually transitioned over a four-day acclimatization period, then kept for the last 22 days under EXT conditions. Water drinking was limited to twice daily in both groups. Excessive solar radiation-induced heat load – with daytime black globe temperatures (Tbg) often exceeding 40°C – under EXT was primarily responsible (r2=0.49; P<0.05) for 0.57 and 1.72°C rises in Tc and Tp, respectively, over INT kids. Unlike the typically biphasic pattern noticed for daily temperatures of both body sites in INT goats, that of EXT counterparts became rather polyphasic, whereby water drinking had drastic and prolonged thermolytic effect, inducing 0.40–0.41 and 0.79–1.45°C declines in Tc and Tp, on midday and afternoon watering bouts, respectively. Despite indication for added daytime heat load, EXT goats displayed lower early morning Tc than INT. All animals exhibited hypohydration, as reflected by rises in hematocrit, serum osmolality, albumin, potassium, and sodium, being more pronounced in EXT conditions. Results emphasize the excessive thermophysiological strain facing grazing animals in arid zones during the summer.

A Case Study to Assess the near-Glazed Workplace Thermal Performance

Passive solar control solutions have been widely used in buildings in tropic countries like Malaysia. It is assumed that these solutions may notably control the heat-gain of buildings. However, there is a lack of empirical studies that assess the extent of green-glazed techniques to sufficiently control solar heat-gain. The current study uses a case study approach to examine the thermal indoor performance, particularly the near-glazed workplace area. The performance of the ST Diamond Building (in Putra Jaya, Malaysia) has been examined in terms of: outdoor/indoor dry bulb temperature; glass surface temperature; heat flux through glazing; outdoor/indoor air movement; lux and; solar radiation. The results of the field analysis indicated that ST Diamond Building’s green-glazed solutions are efficient to control solar heat gain, which in turn will lead to reduce energy consumption for controlling solar heat loads.

Synthesis, structure, and optical properties of Au–TiO 2 composite thin films

Titanium dioxide (TiO 2) films with varying concentrations of gold particles were synthesized using pulsed DC magnetron sputtering, with the intent to develop infrared reflecting films for use on cars and planes to reduce solar heat load. Under our deposition conditions, the films are smooth (RMS roughness on the order of 1.0–2.0 nm) and consist of rutile TiO 2 with embedded gold. The average gold particle diameter on the sample surface was found to change from 60 to 200 nm as the volume fraction of gold in the films increased from 1.9 to 4.3% (3.5 to 7.9 mol% Au). The maximum reflectance of these films in the infrared region (800–2500 nm) is > 50%, compared with 30% for pure TiO 2. The Maxwell–Garnett equation does not model the reflectance data very well, due to the relatively large gold particle size. Instead, by assuming that the contribution of gold particles to the reflectance response is proportional to their projected areal fraction in an effective medium approximation, we were able to fit the observed reflectance data quite well.

Internal surfaces including phase change materials for passive optimal shift of solar heat gain

The thermal inertia of building internal components may be used to shift the irradiation (solar) heat load, which could result in substantial energy saving. In this paper, a numerical model was implemented to determine the thermal performance of internal surfaces including Phase Change Materials (PCM). The model was exploited to compare a typical concrete floor with a floor with PCM. Thermal performance was defined by three different objective functions, each pinpointing different thermal characteristics of the heat load. First, parametric studies were performed to understand the influence of the thickness of a typical concrete floor. Then, the optimization of the melting temperature, thickness and position of a PCM layer included in a floor was performed. These analyses used either simplified or real weather conditions (for Québec City). Results showed that the thickness of the concrete floor could be optimized based on the three criteria retained. Also, the floor performance may be enhanced by the inclusion of a PCM layer. It was shown that the gain of performance brought by the internal surfaces thermal mass strongly depends on the weather conditions considered. This paper provides a fundamental understanding of PCM influence on internal surfaces.

Temperature stratification from thermal diodes in solar hot water storage tank

In this brief note, we have experimentally measured the temperature stratification in a solar hot water storage tank resulting from a simulated solar heating load. Various modifications using a double chimney device that acts as a thermal diode were examined with the intent of maximizing temperature stratification. The greatest stratification was seen with a unique thermal diode arrangement named the express-elevator design, so-called for the direct hot water path from the bottom third of the tank to the top third.

A STUDY ON THERMAL LOAD REDUCTION METHOD FOR DOUBLE SKIN IN COLD REGIONS

In cold regions, it is necessary to correspond to solar heat gain and heating load in winter in addition to solar radiation shading and cooling load in summer. Therefore, it becomes important to do the plan and design that should correspond to both high insulation of building and overuse of glasses. Double skin (DS) has attracted attention as architectural methods corresponding to these. The aims of this study are to show the influencing factor of shape, specification and control technique that are directly linked to thermal load reduction method of DS and to reveal the optimum design condition and the energy saving effect after we verified heat characteristic for DS in cold regions.

Body temperature, thermoregulatory behaviour and pelt characteristics of three colour morphs of springbok ( Antidorcas marsupialis)

Using intra-abdominal miniature data loggers, we measured core body temperature in female springbok ( Antidorcas marsupialis) of three colour morphs (black, normal and white), free-living in the Karoo, South Africa, for one year. During winter, white springbok displayed lower daily minimum body temperatures (37.4 ± 0.5 °C), than both black (38.1 ± 0.3 °C) and normal (38.0 ± 0.6 °C) springbok. During spring, black springbok displayed higher daily maximum body temperatures (40.7 ± 0.1 °C) than both white (40.2 ± 0.2 °C) and normal (40.2 ± 0.2 °C) springbok. These high maximum body temperatures were associated with larger daily amplitudes of nychthemeral rhythm of body temperature (2.0 ± 0.2 °C), than that of white (1.6 ± 0.1 °C) and normal (1.7 ± 0.2 °C) springbok. Biophysical properties of sample springbok pelts were consistent with these patterns, as the black springbok pelt showed lower reflectance in the visible spectral range, and higher heat load from simulated solar radiation, than did the pelts of the other two springbok. Black springbok had lower diurnal activity in winter, consistent with them having to forage less because their metabolic cost of homeothermy was lower, but were disadvantaged in hot periods. White springbok, by contrast, were more protected from solar heat load, but potentially less able to meet the energy cost of homeothermy in winter. Thus energy considerations may underlie the rarity of the springbok colour morphs.

A second generation climate index for tourism (CIT): specification and verification

Climate is a key resource for many types of tourism and as such can be measured and evaluated. An index approach is required for this task because of the multifaceted nature of weather and the complex ways that weather variables come together to give meaning to climate for tourism. Here we address the deficiencies of past indices by devising a theoretically sound and empirically tested method that integrates the various facets of climate and weather into a single index called the Climate Index for Tourism (CIT). CIT rates the climate resource for activities that are highly climate/weather sensitive, specifically, beach "sun, sea and sand" (3S) holidays. CIT integrates thermal (T), aesthetic (A) and physical (P) facets of weather, which are combined in a weather typology matrix to determine a climate satisfaction rating that ranges from very poor (1=unacceptable) to very good (7=optimal). Parameter A refers to sky condition and P to rain or high wind. T is the body-atmosphere energy balance that integrates the environmental and physiological thermal variables, such as solar heat load, heat loss by convection (wind) and by evaporation (sweating), longwave radiation exchange and metabolic heat (activity level). Rather than use T as a net energy (calorific) value, CIT requires that it be expressed as thermal sensation using the standard nine-point ASHRAE scale ("very hot" to "very cold"). In this way, any of the several body-atmosphere energy balance schemes available may be used, maximizing the flexibility of the index. A survey (N=331) was used to validate the initial CIT. Respondents were asked to rate nine thermal states (T) with different sky conditions (A). They were also asked to assess the impact of high winds or prolonged rain on the perceived quality of the overall weather condition. The data was analysed statistically to complete the weather typology matrix, which covered every possible combination of T, A and P. Conditions considered to be optimal (CIT class 6-7) for 3S tourism were those that were "slightly warm" with clear skies or scattered cloud (<or=25% cloud). Acceptable conditions (CIT=4-5) fell within the thermal range "indifferent" to "hot" even when the sky was overcast. Wind equal to or in excess of 6 m/s (22 km/h) or rain resulted in the CIT rating dropping to 1 or 2 (unacceptable) and was thus an override of pleasant thermal conditions. Further cross-cultural research is underway to examine whether climate preferences vary with different social and cultural tourist segments internationally.

Effect of anti-solar glass film on heat transfer and mean radiant temperature inside cabin of air-conditioned vehicle

SYNOPSIS This paper addresses solar heat load entering an air-conditioned pickup-car cabin and behaviour of the mean radiant temperature, MRT, in the cabin including the fuel consumption due to the air conditioner. The experiments have been carried out under the climate of Bangkok, Thailand when all the windows except the windscreen are coated with 40% cutoff anti-solar film. A set of mathematical models to evaluate the surface temperatures of the windows and the cabin walls has been presented and the results agree quite well with those of the experimental data. With the temperatures inside the car cabin, the MRT could be calculated. It was found that with the film coating on the windows, the MRT inside the cabin comes closer to the inside air temperature than without the film. For films of 40, 60 and 80% radiation cutoff, when the outside air temperature is lower than 25°C, the lighter film gives similar performance to the darker film. When the outside temperature is higher than 25°C, the darker film shows an advantage in reducing the MRT. In a car with 40, 60 and 80% cutoff anti-solar film the cooling load could be reduced by about 14, 18 and 20%, respectively, compared with that without the film. Fuel savings could be about 11.7, 14.4 and 18%, respectively.

Fur versus feathers: the different roles of red kangaroo fur and emu feathers in thermoregulation in the Australian arid zone.

Fur or feathers provide protection against heat loads from solar radiation for birds and mammals. The red kangaroo (Macropus rufus) and the emu (Dromaius novaehollandiae) are conspicuous in arid environments of Australia where there is potential for high solar loads. The diurnal D. novaehollandiae feeds in the open yet it has a dark coat with a high absorptivity (83%), which contrasts with that of M. rufus (61%), but M. rufus generally shelters in shade during the day. We examined the effect of coat characteristics on the heat load from solar radiation at skin level. Coat depth and density (thermal conductance or insulation) and the level of penetration of solar radiation into the coat were important determinants of solar heat load. For M. rufus less than 25% of incident radiation reached the body at low wind speeds and this diminished to below 15% at moderate wind speeds. In the modest shade M. rufus seeks on summer days, their heat load from solar radiation appears minimal. Colour differences among M. rufus did not affect thermal load. D. novaehollandiae on the other hand is exposed to the full incident solar load in the open but its plumage provides almost complete protection from solar radiation. Solar radiation is absorbed at the feather surface and the insulation provided by the deep coat prevents heat transmission to the skin.

Performance evaluation of a monomethylamine–water solar absorption refrigeration system for milk cooling purposes

This study reports the applicability and the theoretical thermodynamic simulation of a solar driven monomethylamine–water single-stage absorption refrigeration cycle for milk cooling purposes in the rural regions of Mexico. A solar heating system using evacuated tube collectors coupled with a conventional auxiliary heating system is proposed. The simulation of the yearly dynamic behaviour of the solar system is carried out with the solar radiation and climate data of typical Mexican dairy farms in the semi-tropical regions. The theoretical coefficients of performance present moderate values at relative low generator and high evaporator temperatures and low absorption and condenser temperature values. The use of the solution heat exchanger and the milk precooler improve the thermodynamic efficiency and reduces the solar heating load fraction FSOL.

SE—Structures and Environment: Solar Heat Load in Uninsulated Livestock Buildings

High environmental temperatures affect animal productivity. Even in northern Europe, especially uninsulated livestock buildings may reach high air temperature levels during warm and sunny days in the summer due to the heat gain by solar irradiation. The objective of this research was to determine the solar heat load, the ratio of solar heat utilization, the absorptance factor, the transmittance–absorptance factor and the overall heat transfer coefficient per m2of floor area for an uninsulated building. Two studies were made in the same building but with different roof claddings. In the first study, both the wall cladding and the roof cladding were transparent polycarbonate double web sheets (U -value of 3·0 Wm−2K−1). In the second study, 85% of the roof cladding was changed to non-transparent black fibre cement sheets. The outside and inside air temperatures, the temperature in the exhaust airflow and the solar irradiation against a horizontal surface were measured continuously. The specific airflow was changed in steps between 0·0017 and 0·027 m3m−2s−1.The temperature difference had a maximum about 1–2 h later than the maximum solar irradiation. The ratio of solar heat utilization, defined as the fraction of solar irradiation against the building envelope that is transferred to sensible heat in the air volume, varies due to the ventilated airflow through the building. A higher airflow results in a higher utilization. The transmittance–absorptance factor for the building with transparent polycarbonate roof was 0·36 and the absorptance factor for the building with non-transparent fibre cement roof was 0·20. The overall heat transfer coefficients per m2of floor area for the same buildings were 11·0 and 12·5 Wm−2K−1, respectively.

The Role of the Plumage in Heat Transfer Processes of Birds1

The plumage of birds provides a critical thermal buffer between the animal and its environment. Rates of energy expenditure are strongly influenced by the thermal properties of the environment or the microclimates the animal occupies. Current data suggest that the addition of solar radiation is equivalent to three to four-fold changes in wind speed and that solar heat gain can be extremely sensitive to changes in wind speed.Dry heat transfer through the plumage occurs by three avenues 1) conduction and free convection through air 2) conduction along the solid elements of the plumage and 3) radiation. Overall, about 95% of the total heat flow is evenly divided between the first two avenues. Radiative heat transfer accounts for only about 5% of total heat flow. Plumage color, as well as the microstructure and micro-optical properties of plumage elements, when combined with environmental properties (e.g., wind speed), determine the radiative heat loads that birds acquire from solar radiation. Although plumage color or reflectivity determines the fraction of incident solar radiation that is absorbed by the plumage and generates heat, the fraction of this heat that contributes to the thermal load on the animal can vary greatly. In a fibrous coat such as a plumage, there is some variable penetration into the coat, with absorption over a range of coat depths. Factors such as feather micro-optics and structure are critical determinants of radiation penetration into avian coats. Significant differences in solar heat loads can also result from behavioral adjustments in plumage thickness.

The Role of the Plumage in Heat Transfer Processes of Birds

The plumage of birds provides a critical thermal buffer between the animal and its environment. Rates of energy expenditure are strongly influenced by the thermal properties of the environment or the microclimates the animal occupies. Current data suggest that the addition of solar radiation is equivalent to three to four-fold changes in wind speed and that solar heat gain can be extremely sensitive to changes in wind speed. Dry heat transfer through the plumage occurs by three avenues 1) conduction and free convection through air 2) conduction along the solid elements of the plumage and 3) radiation. Overall, about 95% of the total heat flow is evenly divided between the first two avenues. Radiative heat transfer accounts for only about 5% of total heat flow. Plumage color, as well as the microstructure and micro-optical properties of plumage elements, when combined with environmental properties (e.g., wind speed), determine the radiative heat loads that birds acquire from solar radiation. Although plumage color or reflectivity determines the fraction of incident solar radiation that is absorbed by the plumage and generates heat, the fraction of this heat that contributes to the thermal load on the animal can vary greatly. In a fibrous coat such as a plumage, there is some variable penetration into the coat, with absorption over a range of coat depths. Factors such as feather micro-optics and structure are critical determinants of radiation penetration into avian coats. Significant differences in solar heat loads can also result from behavioral adjustments in plumage thickness.

Thermal performance of a solar-aided latent heat store used for space heating by heat pump

In this study, the cylindrical phase change storage tank linked to a solar powered heat pump system is investigated experimentally and theoretically. A simulation model defining the transient behaviour of the phase change unit was used. In the tank, the phase change material (PCM) is inside cylindrical tubes and the heat transfer fluid (HTF) flows parallel to it. The heat transfer problem of the model (treated as two-dimensional) was solved numerically by an enthalpy-based finite differences method and validated against experimental data. The experiments were performed from November to May in the heating seasons of 1992–1993 and 1993–1994 to measure both the mean temperature of water within the tank and the inlet and outlet water temperature of the tank. The experimentally obtained inlet water temperatures are also taken as inlet water temperature of the simulated model. Thus, theoretical temperature and stored heat energy distribution within the tank have been determined. Solar radiation and space heating loads for the heating seasons mentioned above are also presented.

Heat treatment and bending of low-E glass

Automotive companies continue to pressure their suppliers to control cost, and the glass industry, in particular, has had a difficult time penetrating the automotive market with new, innovative, added value products. An exception where both the customer's needs and the supplier's ability to meet these needs have been satisfied is the application of coatings for automotive glazing to efficiently reduce solar heat load in vehicles. Automotive designers are pushing the limits on steep installation angles and increasing glazing areas in vehicles, while the demand for fuel efficiency and environmental concerns are driving the downsizing and efficiency of air conditioning units. Under these conditions the use of tinted glass, which absorbs solar energy, is limited in adequately providing driver comfort. The use of low-E coatings, which reflect the solar energy, is a more efficient way of reducing the solar heat buildup. The widespread use of coated low-E for solar glazing in vehicles owes its existence to a cost effective manufacturing process which requires that the glass is first coated flat, rather than bent. The flat coated glass is then subsequently bent and laminated, or tempered. Heat treatable multilayer coatings have been developed containing two layers of silver that are finding wide use today in both the automotive and building industries. In addition, since the coating is conductive, a windshield, e.g. can serve a range of functions such as antenna, or defroster and deicer.