Solar Heating Unit Research Articles

Twisted integration of high-efficiency photothermal/water-transported yarns for boosting solar-powered fabric evaporator

Positioned as high-efficiency low-cost desalination technology, solar interfacial vapor generation still remains challenging in precisely managing interfacial photothermal behaviors. Here, an integral solar-heating yarn twisted by both carbon nanotube (CNT) fibers and cotton yarns processed via carbon black slurry is developed for architecting high-efficiency fabric evaporators, where modified CNT and cotton serve as the solar-heating unit and water-supply unit, respectively. The unique structure of hybrid yarns features pronounced gradient photothermal difference of 5 °C between CNT and cotton regions in dry state, and meanwhile enables robust Marangoni vapor flows and weak hydration state. As a result, the crafted fabric evaporator has a superior evaporation rate of 2.83 kg m−2 h−1, which is the highest value reported among 2D fabric evaporators. This work introduces an innovative strategy for high-efficiency interfacial solar heating, significantly boosting evaporation performance of flexible and portable evaporators.

Experimental investigation of dynamic wind tower augmented with solar heating unit for improved thermal comfort in buildings during cold conditions

Wind towers have been used in buildings for centuries to harness natural airflow and ventilation. Their usefulness comes from their capacity to absorb wind energy and direct it into interior areas, promoting airflow and exchange. Scientific evidence shows that buildings are a substantial contributor to global warming and energy use. HVAC systems contribute to a significant percentage of this energy demand. In this situation, using wind towers to reduce greenhouse gas emissions is a viable and cost-effective option.In this work, a novel approach of integrating a rotation unit into the wind tower was carried out to enhance the performance. By enabling the wind tower to rotate and align with the direction of maximum wind velocity, the system could optimize the ability to capture the wind lead up to enhanced ACR and improved indoor air quality. This study further incorporates two solar heating units (SHU) to heat the incoming fresh air, which can reduce the thermal load on conventional heating systems.Through comprehensive measurements and analysis, this work studied the performance of the wind tower system under different wind velocities and solar radiation levels. The results showed that the rotation unit (RU) increased the average Air Change Rate by as much as 61%. Due to the incorporation of SHU and RU, the overall average temperature inside the test room increased by 6.09%. Also, the average velocity intake in the wind tower rose by 15–30% due to the RU. The findings discussed in this paper provide valuable insights for architects, engineers, and researchers involved in designing and optimizing ventilation and heating systems, paving the way for more environmentally friendly and comfortable living environments.

Performance investigation of an innovative solar heating unit for a powered self-sustained solar dryer

Drying food is an efficient way to prevent crop decay. However, drying techniques are known to be intensive processes in which the energy required is usually met by fossil fuels, the main sources of greenhouse gas emissions. Thus, the development of a solar-powered sustainable drying system is not only crucial for zero CO2 emissions, but also for improved energy efficiency. This study performs a comparative analysis of four solar collectors used as heating units in an indirect forced convection solar dryer. The collectors evaluated were a flat solar collector, two solar air collectors with latent thermal storage (CaCl26H2O and paraffin), and a novel heating unit combining the latter two collectors. This study conducted a comprehensive 4E analysis, evaluating the performance of the collectors through energetic, exergetic, economic, and environmental assessments. The results showed that the pioneering heating unit caused a 30 °C increase in nocturnal temperature compared to other collectors. It demonstrated an annual energy consumption of 640 kWh/year and an energy payback period of 2.5 years. The environmental analysis revealed a significant CO2 reduction of 39 tons. Overall, the proposed heating unit allows a more sustainable and cost-effective drying process while reducing greenhouse gas emissions and promoting energy conservation.

Experimental and numerical study of wind tower integrated with solar heating unit to meet thermal comfort in buildings during cold and sunny climate conditions

Natural ventilation techniques are increasingly being adopted in recent times due to the need to cut down on greenhouse gases emission and energy cost. A classic natural ventilation technique, the wind tower, may be utilised to minimize the load on typical HVAC systems. One of the major disadvantage limiting the deployment of wind tower is the additional heating load it demands on the HVAC system during the winter months. The work focusses on improving the year-round capability of a wind tower by attaching a solar heating unit (SHU) that would heat the incoming ambient air through a conjugate heat transfer system before being circulated into the space to be ventilated. For performance validation, the numerical technique was utilised initially, then an experimental setup was created based on the numerical results to validate for practical situations. Using the CFD simulation, ventilation performance of this tower system was evaluated in terms of mean age of air (MAA) and air change effectiveness (ACE). The commercial ANSYS Fluent was used to solve the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) turbulence model. The results showed that SHU has been able to heat up the incoming air of 18 °C by 5 °C–23 °C which is generally considered as a comfortable temperature range. According to the analyses of airflow rate at different incident angles through the four quadrants of tower, the maximum flow rate (0.45 m3/s) of air steam was observed at 45° incident angle. The ACE values in the inhabited space were typically near to 1.0, indicating that the ventilation air mixed up well in the ventilated zone. The wind tower performance was experimentaly investigated in terms of solar radiation variations, wind velocity variations, temperature variation in SHU and inside wind tower, and air change rate (ACR) on the experimental setup. Experimental study shows a variation of 2–4 °C in the indoor temperature and thereby ensuring optimal thermal comfort. The recommended wind speed for an effective mass flow rate is in the range of 3 m/s, and an average ACR of 25 per hour indicates that the air is being ventilated properly.

Simulation of nanofluid convective flow inside a complex solar thermal system

Today’s world witnesses an unprecedented augmentation in energy consumption which has tipped the balance of attention toward the renewable energies, especially solar energy as the most promising type. With recent developments in the field of solar heating units, evacuated tube solar units have played a prominent role in solar energy absorption process in recent years due to the existence of a vacuum envelope in the structure of the tubes. Following this, a three-dimensional transient numerical study has been carried out by employing computational fluid dynamics aimed to appraise the water flow, natural circulation process and convective rate inside the evacuated tube along with a storage tank. A comparison has been made using water and CuO/H2O nanomaterial as the operate fluid for the purpose of evaluating the efficacy of nanofluid on the functionality of the system. The results in the form of velocity distribution, temperature and velocity contours served as an array of reasons on serviceability of CuO nanoparticles in the given application. This is evidenced by the natural circulation rate and heat transfer sustaining more desirable magnitudes, while observing an increase in the average temperatures of the tube and tank, respectively. Implementation of CuO/water over plain water has been reasserted categorically and thus justified.

Design and prediction method of dual working medium solar energy drying system

The design method of dual working medium solar energy drying system is proposed in this study. The operation control strategy of system is given. In order to obtain the drying chambers suitable air temperature controlling method and the expected operating environment of the system, the flat plate solar collector with dual-function hybrid dryer is regarded as a case. The influence of operation environment parameters on the performance of solar heating unit is analyzed by traditional thermodynamics, and five machine learning methods with python software are carried out to predict the thermal performance of solar heating unit. The effects of ambient temperature, solar radiation intensity and supply air flow of solar heating unit on the outlet air temperature and collecting efficiency are obtained. In addition, ambient relative humidity is found to be the most important effect factors for the outlet temperature of solar heating unit. Gradient Boosting Regression can be regarded as the best prediction performance with R2 of 0.98 and 0.94 on training data and testing data, respectively. This study also pointed out the direction for the application and development of the traditional thermodynamics and machine learning.

The efficiency of using a combined solar plant for the heat and humidity treatment of air

The authors of this work have proposed a combined solar heating unit for the heat and humidity treatment of greenhouse air supplies. The object of research is a combined solar collector for the simultaneous heating of water and air. The heat and humidity treatment of supply air is an energy-intensive technological process that requires a very large consumption of thermal energy and water resources. For the operation of such a system, electric heating installations are often used; however, these systems are not always available and economical. In this paper, to reduce the consumption of traditional energy for the heat treatment of the air supply, a combined solar collector is proposed, and the results of an experimental study of the operating modes of the installation in the conditions of the city of Karshi are presented. It has been developed combined solar collector, the temperature of the heat carriers at the outlet in the heating mode “water + air” reached up to 48 °C (air) and up to 60 °C (water), which are acceptable for air treatment systems of heat and humidity in greenhouses. As a result of the experimental studies, the high energy efficiency of the combined solar collector in the “water + air” heating mode is shown. It has been established that the efficiency of the installation is in the range of 0.45 - 0.69.

Design of Solar Water Heater Using Collector Cylindric Parabolic and Coil Heater as Absorber at Focus Point

Solar thermal water heating systems have been developed to replace conventional heating. Therefore, the design of a parabolic cylinder collector-type solar heating unit with a coil-shaped heater (absorber) has been carried out. The cylindrical collector is made of an aluminum plate covered with a reflective sticker and the base is insulated, having a diameter, height, length, and position of the focal point 150, 60, 200, and 22.4 cm, respectively. The coil water heater of 3/8-inch diameter copper pipe having a diameter, pitch, and length of 20, 3, and 200 cm, respectively. The concentration ratio between collector area and heating pipe area (absorber) is 3.6. The results of heating trials conducted from 10:00 to 16:00 WIT, in Duplo to 100 liters of water circulated through the heating pipe at a speed of 0.017 kg/sec, indicate that heating is affected by fluctuations in radiation intensity. Thermal efficiency is inversely proportional to heating time. the lower the time when the difference between the temperature of the incoming and outgoing water gets smaller, or in other words in the evening the water temperature approaches a steady state. The achieved maximum water-heating temperature is 53C in the average radiation range during the test is 687-693 W/m2.

Utilization of solar energy and climate control systems for enhancing poultry houses productivity

Poultry housing is chosen for the development because it has the highest portion of energy consumption. Solar energy and climate control systems are utilized for producing the highest productivity and conversion rate poultry housing comparing with the conventional methods. Thermal analysis of solar heating unit and photovoltaic is conducted to find out their thermal efficiencies. Experiments are conducted under the following conditions using three power operating systems [flat-plate solar collector + electricity (power operating), flat plate solar collector + photovoltaic and conventional system (depending on only electricity)] and fan stopping periods (2, 5 and 8 min). The poultry house performance was evaluated in terms of relative humidity, ammonia concentration, poultry production, feed conversion rate, required power and production cost. Based on the theoretical analysis, the efficiency of the solar heating system and photovoltaic cells was about 71.6% and 12.5%, respectively. Experimental results reveal that the optimum conditions for enhancing the poultry production (2.29 kg) with conversion rate (1.45 kg feed per kg gain), ammonia concentration at the fifth week (13.65 ppm), production cost (1.12 US $/kg) are achieved by using power operating system of flat-plate solar collector integrated with photovoltaic under 2 min fan stopping periods.

Thermodynamic assessments of the novel cascade air cooling system including solar heating and desiccant cooling units

In this study, the novel cascade system, including solar heating and solid desiccant cooling units, is developed for air cooling process and assessed through energy, exergy and sustainability approaches. The analyses are done at 10:30:00 (morning time), 11:27:54 (late morning time), 12:25:57 (noon time), 14:51:00 (afternoon time), 17:17:06 (evening time). The cooling capacity of the cascade system reaches to maximum (9.29 kW) at the noon time. Also, the maximum thermal COP of the cascade system is 1.7 at the evening time, maximum electrically driven COP is 6.665 at the noon time, and maximum general COP is 1.343 at the evening time. Furthermore, the maximum efficiency of the solar heating unit is determined at the late morning and noon time as 49.807% and 49.732%, respectively. According to the exergy analysis; the maximum exergetic cooling capacity (0.529 kW), electrically driven exergetic COP (0.369) and general exergetic COP (0.2203) rates of the cascade system are obtained at the afternoon time; while the maximum exergetic thermal COP is calculated at the evening time as 0.846. The COPs shows that the cascade system has more performance at the noon and afternoon conditions comparing the other stages.

Performance study of a solar-assisted hollow-fiber-membrane-based air humidification-dehumidification desalination system: Effects of membrane properties

Hollow-fiber membrane humidifiers were used in solar-assisted and membrane-based air humidification-dehumidification desalination systems (SMHDD) because of their greater packing density and thus better transfer efficiency. A dynamic mathematical model containing the major components of this system was established, including the membrane humidifier, dehumidifier and solar heating unit. The model was validated with test data from an experimental platform where three kinds of membranes with different membrane thickness, heat conductivity, etc., were tested. To understand the role of membrane characteristics in the proposed desalination system, the effects of the membrane moisture diffusivity (Dm), heat conductivity (λm), membrane thickness (δm) and membrane area (Atot) on the system performance were analyzed numerically. Of the three factors, Dm and Atot show the most significant effect on the accumulated freshwater production (AP) and coefficient of performance (COP), and the effects of λm on the system performance are far less pronounced than that of Dm and δm. In summary, membranes with higher moisture diffusivity and smaller thickness can improve system performance without much attention to the heat conductivity. However, further raising Dm above 3.0 × 10−6 m2/s has a slight benefit to the performance improvement. Findings in this paper are useful in guiding the preparation of membranes used for application-scale membrane-based desalination systems operating in real-world environmental conditions.

Energy consumption minimization in an innovative hybrid power production station by employing PV and evacuated tube collector solar thermal systems

Combination of a grid connected photovoltaic (PV) plant with a compressed air energy storage system (CAES) and a city gate station (CGS) has been proposed and investigated recently, leading to satisfactory performance results. The only deficiency of this system is the huge amount of fuel required to provide its heating demand. In this work, feasibility of employing evacuated tube solar thermal systems to supply the heating demand of the hybrid power plant is studied. After presenting detailed mathematical modeling, the solar heating units and other components of the power plant are properly sized. The results of simulations demonstrate that a total of 7000 evacuated tube collectors are required in the system, leading to elimination of the air heater from the CAES system completely and 17.2% fuel saving at the CGS. The total annual solar heat of 17.5 GWh is supplied for the system, 214 GWh power could directly be sold to the grid, 9.7 GWh power slumps is recovered and 53.5 GWh power is produced at nights. In the end, internal rate of return (IRR) method is used to compare economically the proposed system with similar systems proposed previously, outperforming all of the other candidates with an IRR of 11.1%.

The first and second law analysis of a grid connected photovoltaic plant equipped with a compressed air energy storage unit

PV (Photovoltaic) plants are widely used to produce power in either large or small scales all around the world. In addition, CAES (compressed air energy storage) system has attracted considerable attention as one of the most efficient candidates for large scales energy storage applications in the recent years. In this work, detailed energy and exergy analysis of a 100 MWp (megawatt peak) grid connected PV plant equipped with a CAES system is carried out. The PV plant is assumed to be located in Brazil. The formulations related to the first and the second laws of thermodynamic for all components as well as detailed solar engineering formulations for both the PV farm and the solar heating unit are presented. The performance of the power plant is comprehensively investigated for one entire year in real circumstances. The results revealed that the energy and exergy efficiencies of the CAES system are very close and vary from 35% up to 65% during the year. Also, the annual average exergy and energy efficiencies of the power plant are calculated to be 17.9% and 16.2%, respectively.

Numerical Simulation & Experimental Research of Heat Charging Process of Cylindrical Units with PCM of Al-Si Alloy

Phase change thermal storage used metal as phase change material (PCM) is an important mode of solar thermal energy storage. In this paper, the heat charging processes of solar heating units were simulated under three kinds of heating flux 100,150 and 200kW/m2 at the bottom face respectively, while the thickness of heat receiving layer at the bottom was in 5, 10 and 15mm. Al-Si alloy was selected as PCM used in the cylindrical body of the units which were in the size of φ1000×1000mm. The change of temperature and solid-liquid phase change interface of Al-Si alloy were analyzed to find out the suitable absorber thickness of thermal energy storage units which can run safety under the condition of temperature 700~900K and heat flux 100~200kW/m2, such as the application of solar thermal energy storage unit in high temperature solar thermal power stations. In the last a test system was built up and the experimental result was close to the simulation value of a unit in the size of φ300×1000×10mm.

Experimental study of a solar space heating model using Jordanian rocks for storage

A compact solar air heating unit for space heating is developed and tested using four types of Jordanian rocks in their natural forms as the heat storage medium. The collector efficiency equation, hence the system design parameters, and the heat capacities of the rocks in the storage space environment are determined. The results are used in an application: heating a 220 m 2 floor area house in the Amman area. It is found that, by using a collector area of 50 m 2, the annual heating load supplied by solar energy amounts to about 52% of the total load; if the collector area increases to 100 m 2, the percentage of the load supplied by the solar source increases to 81%. The storage volume required for 50 m 2 of collector area, if tarsand is used as the storage medium, is about 8.9 m 3, if zeolite is used for storage instead, the storage volume drops to about 3.5 m 3. The results reported in this paper adequately support the tested solar heating unit as an alternative to the classical packed bed systems.

Financial Analysis of Solar Energy Applications with Endogenous System Sizing

AbstractThis paper is concerned with analysis of economic feasibility of solar energy systems. Methodology for estimating energy output from different sized systems is briefly presented, and this is used to determine technical coefficients for a mixed integer model which optimizes the size of the solar heating unit for a particular use. An empirical example of hot water heating on a Georgia dairy is presented. Cost curves are provided for the dairy example to illustrate the effect of sizing on the economic feasibility of solar heating and to elucidate the structure of the optimal sizing decision.