Evacuated Tube Research Articles

Energy, exergy and exergoeconomic (3E's) analysis of simmering type cooking using evacuated tube collector

AbstractA solar cooking system is investigated for the simmering type of cooking using slow heating cooking pot (SHCP) and evacuated tube collector (EVTC). The thermic oil used as heat transfer fluid (HTF) is utilized to convey heat from the solar collector to SHCP. Indian cuisine items like Khoa and Kheer are cooked by using simmering method of cooking. The cooking load is varied from 1 to 2.5 L for khoa preparation and 2 to 2.8 L load is varied for kheer preparation. The cooking is done by utilizing the thermal energy of thermic oil flowing inside the SHCP and its average energy and exergy efficiency is evaluated which varies from ~0.20 to around 0.30 and 0.15 to 0.20, respectively. The payback period of the presented solar cooking system is 3.45 years.

An active solar desalination system integrated with collective condenser heat pipe solar evacuated tube collector: a thermoeconomic analysis.

An experimental investigation was executed on the solar evacuated tube collector containing a collective condenser unit of heat pipe arrangement attached to a single slope solar desalination system. The brackish water preheating was done by the unique solar collector before entering the still. Performance analysis of the system was carried out with 0.001, 0.002 and 0.003kg/s brackish water flow rate in the collector and 0.01, 0.02 and 0.03m of brine water depth in a single-slope solar desalination system. The feasibility of the proposed system was evaluated by thermodynamic analysis, embodied energy, CO2 mitigation and economic analysis. Active desalination system with collective condenser heat pipe evacuated tube collector at 0.001kg/s brackish water flow rate and 0.01m water depth produced maximum freshwater yield, average daily thermal and exergy efficiency of 3.085l/m2day, 30.25% and 3.17% respectively. An increase of maximum freshwater yield of 37.11% and average daily thermal efficiency of 43.5% respectively were achieved at a brackish water flow rate of 0.001kg/s and 0.01m of basin water depth in comparison with a traditional single slope solar desalination system. The embodied energy of the system was estimated as 630.77 kWh, and 0.001kg/s and 0.01m of water depth resulted in the highest earned carbon credit of 16,954.48 INR. The minimum payback period of 2.19years was achieved at the lower brackish water flow rate and basin water depth of 0.001kg/s and 0.01m respectively.

Solar Thermal Process Parameters Forecasting for Evacuated Tubes Collector (ETC) Based on RNN-LSTM

Solar Heat for Industrial Process (SHIP) systems are a clean source of alternative and renewable energy for industrial processes. A typical SHIP system consists of a solar panel connected with a thermal storage system along with necessary piping. Predictive maintenance and condition monitoring of these SHIP systems are essential to prevent system downtime and ensure a steady supply of heated water for a particular industrial process. This paper proposes the use of recurrent neural network-based predictive models to forecast solar thermal process parameters. Data of five process parameters namely - Solar Irradiance, Solar Collector Inlet & Outlet Temperature, and Flux Calorimeter Readings at two points were collected throughout a four-month period. Two variants of RNN, including LSTM and Gated Recurrent Units, were explored and the performance for this forecasting task was compared. The results show that Root Mean Square Errors (RMSE) between the actual and predicted values were 0.4346 (Solar Irradiance), 61.51 (Heat Meter 1), 23.85 (Heat Meter 2), Inlet Temperature (0.432) and Outlet Temperature (0.805) respectively. These results open up possibilities for employing a deep learning based forecasting method in the application of SHIP systems. ABSTRAK: Penggunaan sumber bersih seperti Tenaga Solar dalam Proses Industri (SHIP) adalah satu kaedah alternatif untuk menhasilkan tenaga yang boleh diperbaharui bagi mengurangkan kesan gas rumah hijau yang terhasil dari proses industri. Sistem SHIP biasanya mengandungi panel solar dan sistem penyimpanan haba yang berhubung melalui paip yang sesuai. Penyelengaraan secara berkala diperlukan bagi memastikan sistem ini sentiasa membekalkan tenaga solar pada kadar bersesuaian dan bekalan tenaga solar yang terhasil berterusan dan tidak menjejaskan sistem pemanasan air bagi sesuatu proses industri. Kajian ini mencadangkan penggunaan model ramalan rangkaian neural berulang bagi meramal parameter proses pemanasan solar. Kelima-lima parameter proses iaitu – Iradiasi Solar, Suhu Saluran Keluar & Masuk Pengumpul Solar dan Bacaan Kalorimeter Fluks pada dua tempat diambil sepanjang empat bulan (dari Julai 2021 sehingga Oktober 2021). Dapatan menunjukkan dua varian RNN termasuk LSTM dan Unit Berulang dapat dibanding prestasinya bagi tugas ramalan ini. Dapatan kajian menunjukkan Ralat Punca Min Kuasa Dua (RMSE) antara bacaan sebenar dan ramalan adalah masing-masing 0.4346 (Iradiasi Solar), 61.51 (Meter Terma 1), 23.85 (Meter Terma 2), Suhu Salur Masuk (0.432) and Suhu Salur Keluar (0.805). Ini membuka peluang kajian mendalam berdasarkan kaedah ramalan dalam aplikasi sistem SHIP.

Performance analysis of step type solar still and comparison of the performance with evacuated tube collector coupled with single slope step type solar still

This research project aims to address the growing need for freshwater in regions affected by water scarcity, particularly in coastal and desert areas. The focus is on evaluating the effectiveness of a solar-powered desalination system, which utilizes a single slope step type solar still and an Evacuated Tube Collector (ETC) to produce fresh drinkable water. Additionally, Computational Fluid Dynamics (CFD) analysis is conducted to gain insights into the natural convection of heat transfer within a glass tube, which creates a buoyant flow of saline water. The design consists of a solar evacuated tube, which heats up due to the exposure to sun rays and this heat is transferred to the impure/saline water (effluent). The water is then discharged to a single slope step type solar still which absorbs energy from sunlight and increases the evaporation rate in the solar still. Thus, the water evaporates and is then condensed by the inner surface of the glass roof hence purified water is collected. The CFD flow analysis of incompressible fluid under the effect of gravity in the transient condition is carried out for ETC in the ANSYS workbench. Also, fluid flow analysis of single slope step type solar still consisting of ten steps with a water depth of 3 cm in multiphase conditions using the VOF model is carried out to obtain the amount of distillate output per day in fair weather conditions in the location 13.2848⁰ N, 74.7486⁰ E in Katapady, Udupi. The amount of distillate collected as a result of CFD analysis was found to be 5.195 kg/day. The contours obtained from the steady state analysis for solar still showed the distribution of temperature, solar heat flux, and mass flow rate. The transient analysis of the ETC assisted well in obtaining the temperature in the ETC collector tank and the variation in solar radiation throughout the day. The contours of ETC showed the buoyant flow of water under natural convection, velocity distribution, density distribution and solar irradiation distribution on glass walls.

Fluid flow and heat transfer characteristics of artificially roughened evacuated tube collector

An artificially roughened evacuated tube collector with periodic circular ribs was studied for heat transfer and flow characteristics. The current study was conducted in ANSYS Fluent 16.2 to analyze influence of fixed pitch to wire diameter ratio of 12 and wire diameter to hydraulic diameter ratio of 0.0643 on frictional factor and Nusselt number. RNG k-ε with enhanced wall treatment turbulence model was used for Reynolds number range of 2500–8000. For identical flow conditions, performance comparison of evacuated tube collectors having roughened and smooth absorber was undertaken. Reynolds number increase resulted in enhancement of Nusselt number and reduction in frictional factor. In comparison to smooth evacuated tube collector, augmentation of order 2.51 and 1.66 times was achieved in frictional factor and Nusselt number respectively. Across the entire Reynolds number range studied, thermohydraluic performance factor value ranged between 1.16 and 1.23.

Heat pipe collectors with overheating prevention in a cost-optimized system concept: Monitoring of system performance and stagnation loads under real conditions

Heat pipe collectors can significantly reduce stagnation loads in solar thermal systems due to their thermophysical properties. The paper experimentally investigates a novel system concept based on both evacuated tube collectors and flat-plate collectors with overheating prevention. Due to the resulting temperature limitation in the collector, the use of polymeric pipes as well as a significantly downsized expansion volume is possible. We implemented this concept in five demonstration plants and monitored their behavior over more than one year of operation. Both domestic hot water systems and combi-systems with space heating support in residential and office buildings are under consideration. The measured collector performance in all the systems matches the theoretical collector efficiency curve with a maximum deviation of five percentage points. Depending on the individual system configurations, the specific annual yield ranges between 174 kWh/m² and 445 kWh/m². During stagnation, we report a maximum temperature between 105 °C and 127 °C. In comparison to state-of-the-art systems, the maximum temperature in the solar circuit is 80–100 K lower and evaporation does not occur. The approach leads to reductions in investment costs of up to 16% and can significantly decrease the annual maintenance effort. Assuming a system lifetime of 25 years, we estimate a cost reduction of up to 22% in Levelized Cost of Heat (LCoH) compared to common system configurations.

Mathematical modeling and performance analysis of a solar assisted vapour absorption refrigeration system

Climate change is the hottest topic today on earth. Traditional HVAC’s harm the environment and stand out to be a major contributor to global warming. One of the many techniques to mitigate the current climate crisis is by utilizing the abundantly available solar radiation. Solar evacuated tube collectors are used to absorb solar radiation. This solar power is used to provide solar cooling technologies. Unlike the conventional HVAC’s thermally driven absorption cooling is a boon in today’s era. In the following research work, the study aims to provide numerical modeling of a solar assisted air-conditioning unit through the first law of thermodynamics using mass balancing equations for the province of Delhi in July. This research work’s aim is to build and evaluate a Li-Br absorption cooler with a capacity of 1 KW. This paper aims to provide characteristic design features of components and measures the efficiency of the system at operating conditions. PCM based thermal energy storage tank is adopted which helps to supply cold air even at no sunlight hours. As a result of this research study, such solar assisted air conditioners turn out to be a chosen solution for sustainability.

Parametric Study and Long-term Prediction of the Production of a Solar Water Heaters Installation

In order to increase the contribution of solar thermal energy in moderately exposed locations, it is necessary to study solar installations and optimise their design. A parametric analysis was carried out on a solar installation in a European climate, consisting of 16 water-in-glass evacuated tube collectors connected to their storage unit. The purpose of the installation is to prepare large quantities of hot water at 85°C twice a day to prepare feed for a calf rearing farm. The arrangement of half of the collectors in series and half in parallel makes this solar installation suitable for this application. The orientation and the inclination were studied for four different European cities to determine their effects on the energy supplied. The results show that location and orientation have a great impact, especially in the cities with higher solar irradiance. Having solar water heaters facing south with a 45° tilt angle allow the solar installation to maximise its production for three locations. Studying the ratio of the energy supply to the energy demand is an interesting way to show the performance of the solar installation. The developed dynamic numerical model will help design the solar energy production in challenging weather conditions where the reduction of fossil energy consumption can be optimised.

Energy, exergy and economic assessments of novel sustainable solar powered evacuated tube collector integrated active desalination system

Energy, exergy and economic assessments of novel sustainable solar powered evacuated tube collector integrated active desalination system

Investigating the performance of a Novel Deep feeding technique in All-Water Evacuated tube Collectors for Solar Desalination Systems

Investigating the performance of a Novel Deep feeding technique in All-Water Evacuated tube Collectors for Solar Desalination Systems

A review on solar desalination techniques using vacuum technology

The explosion of the population is alarming as the demand increases exponentially for resources. The freshwater resources are being exploited, and innovative and economical methods are analyzed experimentally to extract freshwater from various sources. Desalination performed using solar energy is an economical method to obtain fresh water from seawater and brackish water, which are available prolifically in nature. Since the phenomenon of desalination demands solar irradiation, which is an intermittent source of energy, distillation is not feasible in some places where the solar intensity is low. In the solar desalination, the saturation temperature of the saline water is very less at low saturation pressure thereby requiring large latent heat of evaporation. Hence, vacuum pressure could be the most appropriate choice to extract drinkable water in territories where the intensity of solar irradiation is poor. In order to this, the utilization of evacuated tube collectors and vacuum technology in the solar desalination unit has been considered for discussion as it is the most sought-after subject of interest in the current scenario. Methods for implementing the vacuum technology are also introduced with plenty of experimentations. Vacuum technology implemented in the evaporator of desalination system has been supplemented with nano-fluids and phase change materials to accelerate the evaporation process, increase efficiency, and obtain a greater productivity. In this review, the performance of the solar desalination unit under the vacuum effect were discussed in detail. Furthermore, in economic analysis, the cost effectiveness and cost per liter of distillate (CPL) were discussed to estimate the payback period. Finally, this review also suggests the vision to identify the future scope for additional implementations.

Technical & financial feasibility assessment of heat pipe evacuated tube collector for water heating using Monte Carlo technique for buildings

The main objective of this work is to clear the economic condition of heat pipe based solar water heating technology in India. For this, a techno-economic analysis has been carried out which offers the facts for the investment in this sector. A computation model has been developed by the amalgamation of the Monte Carlo Technique (MCT) and Multi-energy/economic relations that take into consideration the risks and integrated uncertainties of different variables. The results reveal that LCWH and PP are found to be lowest for Zone-V and will require the least collector area. Since the highest solar radiation in Zone-V eventually reduces the ratio of annual energy demand to annual solar radiation. Thus Zone-V is the most favorable place for the installation of the solar water heater. The mean values of LCWH, NPV, and PP are found to be 5.14 INR/kWh, 663788.48 INR, and 5.84 years respectively. However, values of LCWH, NPV, and PP through optimization were found to be lesser by 25–33%, higher by 9–28%, and lower by 37–47% respectively.The MCT is efficient to defeat discrepancies in the results of conventional techniques by taking into consideration the range of states according to their probability to offer more accurate forecasts.

Novel high precision low-cost dual axis sun tracker based on three light sensors

This study aims to test a new type of dual axes solar tracker based on just three Light Dependent Resistors (LDR) as optical sensors in order to achieve a high precision sun tracking that satisfies the requirements of solar concentration systems. This new system is integrated into a solar concentrator that uses a set of Fresnel mirrors and an evacuated tube collector as an absorber so that it can be used as a solar water heater. The 3D-printed support that holds LDRs have three compartments to maintain the three LDRs firmly in their place. One is placed on the left and the other on the right side of the support. These two LDRs are responsible for the azimuthal tracking while the third LDR is placed in the center and its responsibility is elevation tracking. This central LDR is covered under an alveolus hollow tube with a length of 45mm crossed all along its center with a 0.4mm slot that lets sun rays reach the central LDR at the bottom of the alveolus hollow tube. A setup was made to collect data based on a pyranometer and three thermocouples positioned at specific points on the evacuated tube collector to record the temperature variation.

Comparative optical and thermal analysis of compound parabolic solar collector with fixed and variable concentration ratio

Solar thermal collectors such as flat plate and evacuated tube collectors are used for maximum of 60-80 ℃ temperature and parabolic trough collectors are used for 700-900 ℃ temperature ranges. It is needed to develop and analyse solar collector, such as compound parabolic collectors (CPC) which can operate for intermediate temperature range from 50-300 ℃ for industrial and domestic applications. However, optical and thermal performance of CPC is strongly influenced by concentration ratio. The current study presents a comparative optical and thermal analysis of CPC with fixed (4.58) and variable (4.58 to 5.87) concentration ratio by using model-based transient simulation approach. Two profiles of compound parabolic collector are analysed with fixed and variable concentration ratio for the subtropical climate of Taxila, Pakistan. 2D profiles of both collectors are modelled and designed in MATLAB and are then analysed optically by using Monte Carlo ray tracing technique through TracePro. In addition, thermal analysis of both profiles is also performed through ANSYS. The resulted optical efficiency with fixed and variable concentration is 91 % and 96 %, respectively at a given tilt angle. Whereas maximum temperature achieved with both profiles is 5°C and 7°C, respectively. Thus, it is concluded that performance of CPC with variable concentration ratio is much better compared to fixed value.

Investigation of a Solar Space Heating System Based on an Evacuated Tube Collector for Baghdad Climatic Conditions

The current work aims at evaluating the overall experimental performance of the solar space heating system regarding the local meteorological conditions of Baghdad. Two types of systems have been considered, namely, the thermal radiator with and without a fan. Indeed, a thermal radiator is connected to evacuate the tube solar collector through a circulating pump to distribute the heat into a room with dimensions of (3×3 m2). The experimental measurements for the current research were carried out during a period of six days in February and March, i.e., under mild conditions where the weather ranged between sunny and cloudy during the day. In order to find out the system performance, the solar radiation intensity, wind speed, inlet and outlet temperatures from solar collectors, inlet and outlet temperatures from thermal radiators, room temperature, and ambient temperature have been measured using specific instruments. The results revealed that, under sunny conditions, the room temperature of the system without a fan changes from 16.2 oC to 23.9 oC with a temperature difference of 7.7 oC. However, when a fan is used, the temperature difference reaches 10 oC. Such an improvement in the performance of the solar heating system that characterized the current work in comparison with its counterpart research is a direct result of the adoption of two main ideas. The first of them is the use of a modern metal heat exchanger that contains vertical and horizontal tubes. In addition to that, it is equipped with a fan that helps to increase the heat exchange between the heat radiator and the room space due to forced convection. Furthermore, the fan works to distribute the heat homogeneously inside the room, thus increasing the efficiency of the system. The second idea, however, is the use of a modern system represented by software that analyzes the results and evaluates the values of solar radiation and wind speed.

Cost-effective and environmentally friendly solar collector for thermally driven cooling systems

Solar collectors are key components that allow the exploitation of solar radiation in sustainable applications such as solar cooling systems. However, the selection criteria of the suitable technology of solar collector are still ambiguous. This paper presents a comprehensive investigation of absorption and adsorption cooling systems powered by different solar collectors, namely flat plate collector, evacuated-tube collector, compound parabolic collector, parabolic trough collector, photovoltaic thermal collector and a new configuration of concentrating photovoltaic thermal collector, for air-conditioning application in a residential building. Thus, the impact of each solar collector on thermal, economic and environmental performances of the solar cooling systems is quantified to identify the most cost-effective and eco-friendly system, under three different climate conditions. The performance results showed that the proposed concentrating photovoltaic thermal collector performed the best for absorption cooling system with a solar coefficient of performance of 0.449, 0.428 and 0.414 in Marrakesh, Barcelona and Oslo cities, characterized by hot arid, warm temperate and boreal climates, respectively, and for the adsorption cooling system as well in Oslo city with a solar coefficient of performance of 0.351, while photovoltaic thermal collector exhibited the best performance for adsorption cooling system in Marrakesh and Barcelona cities with a solar coefficient of performance of 0.397 and 0.386, respectively. Furthermore, the economic findings revealed that the photovoltaic thermal collector is the most cost-effective one for absorption/adsorption systems, with levelized cost of cooling in the order of €0.106/0.111, €0.137/0.142 and €0.287/0.313 per kWh, and discounted payback period of 11.25/11.43, 15.23/14.94 and 24/25.63 years in Marrakesh, Barcelona and Oslo cities, respectively. Besides, evacuated-tube collector is found to be the most environmentally-friendly collector, since it allows reducing greenhouse gases emissions especially in boreal climate with a life cycle climate performance of 5.86/5.99 tCO2 for absorption/adsorption systems.

Life Cycle Assessment for a solar cooling plant

This work aims to evaluate the environmental loads of a hypothetical solar cooling plant making a Life Cycle Assessment (LCA) analysis. In this study, an LCA of a solar cooling plant for a cold room installed in a fruit and vegetable company is performed. The plant is equipped with an absorption chiller of 150 kW and an auxiliary boiler of 50 kW. The hot water storage tank is 5000 l as the cold water one. The solar thermal field is 250 m2 using evacuated tube collectors. The functional unit of the study is the entire plant. The entire life cycle is evaluated assuming that the lifetime is equal to 20 years. The Ecoinvent v3.8 database is used to collect data and SimaPro v.9 software is used to perform the analysis. IPCC 2013 and ReCiPe 2016 are chosen as impact assessment methods and their results are evaluated. The results show that the total CO2 equivalent emissions that are given by the Global Warming Potential evaluation using IPCC 2013 method increase when solar fraction decrease. Therefore, reducing gas consumption and, also, improving plant solar fraction is the most important way to reduce the total emission. However, the solar plant emissions are related to the installation, maintenance and use phases.

In-situ assessment of a solar vacuum tube collectors installation dedicated to hot water production

In order to improve the contribution of solar thermal energy in moderately insolated regions, solar installations have to be optimized and their heating capacity has to be proven. In this aim, an in-situ thermal performance investigation was carried out on a solar installation of 24 “Water-in-Glass” evacuated tube collectors coupled to their storage unit in a northwest European climate. The aim of the installation is to provide a calf-breeding farm with an intermittent supply of water at 80 °C. The particularity of this solar installation is the specific arrangement of this kind of solar water heater in series and in parallel. Instrumentation was implemented to understand and establish energy balances. An analysis was carried out on four sequences representative of each season. The results show that despite mostly unfavorable sky conditions, the solar installation was capable of providing from 12 to 67% of energy needs for these four sequences.

Technical assessment, economic viability, and environmental impact of a solar-driven integrated space and water heating system in various configurations

The use of solar heaters for space and water heating applications in energy efficient buildings is one of the most promising applications of solar energy, particularly in heating-dominated areas. In this paper, six different cases have been compared for an integrated solar space and water heating system, according to results based on the variation in terms of predicted solar fraction and collector efficiency. These models are developed from the combination of two simulation models (configuration 1 and configuration 2) based on different operational strategies and control schemes within the load-side loop and six methods of implementing the properties of different solar collectors, varying thermal energy storage systems (sensible and latent), and selecting optimum PCMs within latent thermal energy storage (LTES). A system operating under configuration 2 (C-2) energized with an evacuated tube collector (ETC) can offer more than 12 % higher solar fraction than a system operating under configuration 1 (C-1) energized with a flat plate collector (FPC). Furthermore, it is anticipated that incorporating optimum PCMs can significantly enhance the thermal energy storage capacity and significantly further enhance the solar fraction depending upon the working schedules and heating requirements. The detailed financial feasibility analysis concludes that the payback period of such a system is up to 5.9 years without considering financial incentives. Moreover, a 60 % reduction in greenhouse gas (GHG) emissions is achieved compared to a base system powered by electricity.

Design, optimization and implementation of a solar cell for wood phytosanitary treatment

ABSTRACT A research program was undertaken with the goal of developing dehumidifier solar wood dryers and wood thermal phytosanitary treatment cells. The first step of the program, was dedicated to the development of the numerical tools that would assist in the design and optimization of the dryers. These were based on an approach that combines micro (at the level of the wood board) and macro (at the level of the entire dryer and its solar heating system) modellings, and that uses typical year weather data, to perform the simulations. A finite difference numerical code was employed to predict the time evolution of the wood and air properties during the thermal phytosanitary treatment of wood. These predictions are employed as input to the TRNSYS© software to model the retained solar phytosanitary treatment installation configuration. In this system, the air leaving the treatment cell is recycled. But prior to injecting it back, it is mixed, in the right proportions, with outside air in order to adjust its humidity. The recycled air temperature is then risen to the operating value in an air-water heat exchanger fed from the storage tank of the solar water loop. The latter includes solar evacuated collectors, two pumps, a storage tank and a heat exchanger. The concept technical feasibility was prooved. The sytem optimization showed that, for a cell to be installed in Tunis, a 22 m2 evacuated tube collector and a 1.5 m3 water reservoir are needed for the treatment of 1 m3 wood stack i.e. 0.7 m3 of wood (reduced to 0.42 m3 in the winter season). A prototype of the optimized system was constructed and preliminary experimental tests are presented.