Insulated Storage Tank Research Articles

Nanofluids (CuO & TiO2) - water as heat transfer fluid in a thermal energy storage system for applications of solar heating: An experimental study

The present work aims to exploit the thermal performance of a packed bed of combined sensible and latent heat of storage unit with an integrated solar heat source. A cylindrical insulated storage tank in the thermal energy storage (TES) unit is filled with spherical capsules separately which contains PCM as paraffin wax and stearic acid. The PCM usage has the benefits that it can be used as a thermal management tool and it reduces the cost and size of the system as it offers higher isothermal behavior and thermal storage capacity. The thermal conductivity of heat transfer fluid (HTF) can be enhanced by using nanoparticles mixed in water. Nanofluids are the more efficient fluids for the applications of heat-transfer. The water based nanofluids are used to transfer heat between the solar collector and storage tank which is a sensible heat storage material. The HTF materials are varied and experimental trials have been conducted separately. Experimentation was carried out first by considering only water as HTF and is extended by adding water with one of the nanomaterials i.e. The TiO2 and CuO, each in 3 HTF vol.% as 0.2, 0.5, and 0.8. The variable source of heat supply considered is solar flat plate collector. The study was transpired by varying the flow-rates of nanofluids as 2.0, 4.0, and 6.0 Lpm. The novelty of this work is to envisage the enhancement of heat transfer and to study the effects on the melting time of the PCM of these fluids which were carried out. The performance parameters like charging time and system efficiency, instantaneous stored heat, cumulative stored heat were studied for the different HTF and for the PCM-paraffin and stearic acid. The batch wise process experiments for discharging were carried out to recover the heat stored, and the results are presented.

Experimental comparison of solar thermal desalination systems based on energy, exergy and economic (3‐E) analysis

AbstractWith rapid increase in human population, the demand of fresh water has been increased significantly and the world will encounter enormous water crisis by 2040. The sea contains nearly 97% of available water on earth. To fulfill the demand of fresh water, desalination of sea water can be best solution. As desalination process can be performed by using low grade energy, the use of solar energy for desalination is very popular. The most popular solar thermal desalination system is conventional solar still but its productivity is very low. In the present study, a new desalination system based on evacuated tube collectors (ETC) is developed and its performance is compared with conventional solar still experimentally. The present system consists of 15 evacuated tubes, an insulated storage tank, a heat exchanger, a condenser, and a thermic fluid as working medium. The performance of both systems is compared on the basis of daily productivity, energy and exergy efficiency, and economic viability. It is observed that the ETC‐based desalination system performed better as compared to the solar still. The average energy and exergy efficiency, productivity and produced fresh water cost of desalination systems based on ETC and conventional solar still are 43.74%, 9.52%, 4.2 L/m2/day, 0.022 $/L and 19.23%, 1.4%, 1.975 L/m2/day, 0.024 $/L respectively. Further, the pay‐back time for ETC based desalination system is also less (104 days) as compared to solar still (113 days).

Cost-effective Electro-Thermal Energy Storage to balance small scale renewable energy systems

To decarbonise the energy production system, the share of renewable energy must increase. Particularly for small-scale stand-alone renewable energy systems, energy storage has become essential in providing electricity when the demand is high, for example, during the night. Although there are many different storage technologies, only a few are suitable for small-scale stand-alone renewable systems. Those systems must be modular and scalable to be deployed according to the capacity needed. Currently, batteries are among the leading grid storage technologies, but the demand, particularly for Lithium-ion batteries, is also high because of the electrification needs of the transportation sector. Therefore, the question of material availability might become an issue in the future, as Lithium is a scarce and critical element. As an alternative, we introduce a new modular electro-thermal energy storage (ETES) technology that is suitable for various storage needs. This storage unit can utilise various thermal storage materials (thermal oil, molten salt, and sand) at high capacities and improved efficiencies. Our design consists of the embedment of Stirling engines and an electric heater into a thermally insulated storage tank. The source electricity is first converted to heat stored in the storage tank and then converted back to electricity when needed. Among the thermal energy storage materials studied here, sand enabled the storage system's efficiency to reach 85% thanks to its wide range of operating temperatures. The cost is projected to be up to six times lower than that of current Lithium-ion batteries. This new electro-thermal energy storage provides a promising cost-efficient, high capacity alternative for stand-alone energy systems.

Cogeneration system driven by solar dish concentrators

AbstractThe objective of this study is the investigation of a cogeneration system for heating and electricity production, which is driven by solar dish concentrators. There is an organic Rankine cycle (ORC) driven by the solar field and produces electricity with its turbine and heating from its condenser. The solar field includes 100 m2 of solar dish concentrators with spiral absorber and an insulated storage tank of 4 m3 storage volume. The system is examined parametrically for different pressure levels in the turbine inlet and superheating degree. The system exergy efficiency is maximized for a superheating of 30 K and a maximum pressure equal to 70% of the toluene critical pressure. In this case, the system produces 12.41 kW electricity, 28.55 kW heating, while the energy efficiency is 51.20%, and the exergy efficiency is 20.69%. Moreover, the system is examined for a typical sunny day, and it is found that the electricity production is 125.6 kWh, the heating production 288.86 kWh, the energy efficiency 48.96%, and the exergy efficiency 19.77%. In the end, the simple payback period of the examined system is found at 6.28 years, which is a good value.

Study of a solar air heater with a heat exchanger – accumulator

The authors of the work presented a solar air heater for maintaining a constant temperature of heated air in drying plants and in air heating systems. The article discusses an experimental installation of a solar air heater was made and an insulated storage tank with a spiral-type heat exchanger for accumulating heated air was installed, additionally equipped with a hinged reflector parallel to the solar air heater, which is also an additional source of thermal energy of solar radiation, the results of an experimental study of the operating modes of the installation in natural and climatic conditions of Karshi. As a result of experimental studies, a high energy efficiency of a solar air heater was determined in the heating mode of heat carriers (air up to + 65 °C and waste oil up to + 75 °C) in June. The analysis of the heat balance of the developed installation is carried out. The influence of the main heat engineering parameters on the thermal power of the installation is analyzed.

Experimental analysis of a solar assisted desiccant-based space heating and humidification system for cold and dry climates

In the current work, an experimental analysis of a solar-assisted desiccant based heating and humidification system is performed for winter season under actual cold and dry conditions of Taxila, Pakistan. The installed setup consists of a silica-gel based desiccant wheel, a heat wheel, dual collector field of flat plate and evacuated tube collectors, and insulated storage tank. The day long measurements and assessments are reported during the months of December to February. The selected months represent wide range of cold and dry weather conditions which are applicable to different climate zones. The experimental results revealed that on average the system heating capacity, COPth, COPe, and auxiliary thermal power requirements for heating are around 5.9 kW, 1.48, 2.14 and 2.75 kW, respectively. Moreover, the solar fraction and the thermal efficiency of collector arrays are observed to be 64.75% and 40%, respectively. The uncertainties associated with humidification effectiveness, heating capacity and COPth are ±2.1%, ±5.5%, and ±7%, respectively. Finally, heating seasonal performance factor of 5 Btu/Wh is achieved. Based on the assessments, it is noted that the solar-assisted heating and humidification system is a viable solution for operation in cold and dry conditions.

A novel storage system for cooling stand-alone photovoltaic installations

Stand-alone photovoltaic systems usually use batteries to adjust energy yield to energy demand. An alternative energy storage system for stand-alone photovoltaic installations is proposed for three cooling applications: air conditioning, food preservation and freezing. A thermally insulated storage tank with ammonia in saturated mixture phase is integrated into the vapour-compression cooling cycle. A thermodynamic model and an economic assessment based on typical costs and cost sensitivity are included to assess the proposed system performance in comparison with a conventional stand-alone photovoltaic system with a vapour-compression cycle. Results show that the proposed storage strategy is an affordable option, especially in hot climates and for food preservation and freezing applications.

Solar thermal dehydrating plant for agricultural products installed in Zacatecas, México

This paper presents a hybrid thermo-solar plant for the dehydration of foods, built in Zacatecas, Mexico. The plant is integrated by a semi-continuous drying chamber with a capacity of up to 2 700 kg of fresh product. The thermal energy required for the drying process is provided by two solar powered thermal systems: an air heating system with 48 collectors (111.1 m2) and a water heating system with 40 solar water heaters (92.4 m2), a thermal insulated storage tank, and a fin and tube heat exchanger. The plant also has a fossil energy backup system (LPG) to heat air. The monitoring system measures and records 55 process variables (temperature, relative humidity, water pressure, solar irradiance, air velocity, volumetric and mass flow rates). Experimental results obtained with the solar air heaters and water collectors are reported. The average efficiency of the solar air heaters field was ˜45% with a maximum increase of the air temperature of 40.8 °C and for the water solar collectors field the average efficiency was ˜50% and the water in the storage tank reaches 89.6 °C in two days of operation. A batch test was carried out on September 26 with the thermos-solar systems for the dehydration of 282 kg of Nopal (Opuntia ficus-indica) with an initial moisture content of 85.28 % (wet basis), reaching a final moisture content of 9.13 % (wet basis) in 9.7 hours. Both thermo-solar systems are able to deliver the temperature required in the food drying process (temperatures above 50 °C). According to the results obtained, different kind of food products can be dried on the thermo-solar plant designed, resulting in substantial fuel savings and environmental benefits. The development and implementation of solar drying systems technology, initially at demonstration scale, in the Mexican industrial sector could allow a technical and economic maturation of the technology, and the benefits could be presented in the short term.

EXPERIMENTAL EVALUATION OF TWO SERPENTINE FLAT PLATE SOLAR WATER HEATING SYSTEMS

The objective of this research work is to investigate the effect of changing working fluid mass flow rates and flow passage diameters on the thermal efficiency in the flat plate solar collector. Two identical flat plate solar collectors were designed, built and installed on the roof of the Agricultural Engineering Department, Faculty of Agriculture, Suez Canal University, Ismailia, Egypt (latitude of 30.62o, longitude 32.27o and 5m above sea level). The collector is rectangular in shape with surface area 1.5 m2. Aluminum sheet is used as an absorbing plate of 1 mm thickness. The diameter of serpentine copper tube was 6 mm (SC1) and 8 mm (SC2). A clear glass cover of 3 mm thick was placed to cover the solar collector. Insulated storage tank with 120 L was used to store the water after passed through the solar collector. The experiments were carried out at different mass water flow rates of 0.45, 1.0 and 1.75 kg min-1. The obtained results showed the SC2 increased the thermal efficiency by 19.3, 15.3 and 15.1 % above that for the SC1 with flow rate 0.45, 1.0 and 1.7 kg min-1, respectively.

Increasing Solar Energy Usage for Dwelling Heating, Using Solar Collectors and Medium Sized Vacuum Insulated Storage Tank

This article describes a method for increasing the solar heat energy share in the heating of a dwelling. Solar irradiation is high in summer, in early autumn, and in spring, but during that same time, the heat demand of dwellings is low. This article describes a solution for storing solar heat energy in summertime as well as the calculations of the heat energy balance of such a storage system. The solar heat energy is stored in a thermally insulated water tank and used in the heating period. The heat is also stored in the ground if necessary, using the ground loop of the heat pump if the water tank’s temperature rises above a certain threshold. The stored heat energy is used directly for heating if the heat carrier temperature inside the tank is sufficient. If the temperature is too low for direct heating, then the heat pump can be used to extract the stored energy. The calculations are based on the solar irradiation measurements and heating demand data of a sample dwelling. The seasonal storing of solar heat energy can increase the solar heat energy usage and decrease the heat pump working time. The long-term storage tank capacity of 15 m3 can increase the direct heating from solar by 41%. The direct heating system efficiency is 51%.

LNG 벙커링용 고효율 LNG 저장탱크 열해석

In 2016, the IMO's new rules for an 80% reduction in NOx emissions in newly built ships will necessitate the use of LNG as a clean fuel. So far, the developed European countries have led the development of LNG bunkering ships and related facilities. An LNG bunkering system stores LNG in a horizontal or vertical IMO C-Type tank insulated with perlite powder, and a vacuum in the annular space between the double walls, like the cryogenic liquid nitrogen tank. Current storage tanks have high heat leakage, evaporating over 2.0% daily, and are difficult to build with the required vacuum. A more efficiently insulated storage tank could reduce the evaporation rate. This research carried out thermal analysis on a new effective insulation method that separates high vacuum in the annular space between two tanks with a solid insulation material, such as urethane foam, lining the outer vessel. This highly efficient insulation system obtained an evaporation rate of 0.03% per day under a vacuum, and an evaporation rate of 0.11% at . Even if the space loses its vacuum, the new insulation system showed a lower evaporation rate of 4.12% than the present perlite system of 4.9%. This newly developed tank can increase the efficiency of LNG storage tank and may help keep LNG bunkering systems safe.

Performance Evaluation of a low cost integrated collector storage solar water heater with independent plane reflectors

High initial cost is one of the reasons why consumers think twice before investing on the conventional solar water heating systems, especially in low income countries. Integrated collector storage systems are available at a lesser cost, but with a penalty of decreased efficiency. In this paper, yet another attempt to reduce cost of solar water heating system has been made by using independent plane reflectors along with an insulated storage tank provided with a heat absorbing aperture. With no tracking arrangement, this system uses only the intense beam radiation available from 9:00 AM to 3:00 PM with a concentration factor of 10. A theoretical study was conducted using commercial computational fluid dynamics software which was followed by an experimental validation of the results. The theoretical results were in agreement with the experimental results. The efficiency of this system was less than collector storage systems reported in the literature by about 10-15%. Maximum average tank temperature of 350 K and efficiency of 0.61 was obtained. Overall loss coefficient was identical with that of existing integrated collector storage systems. DOI: http://dx.doi.org/10.3329/bjsir.v49i3.22128 Bangladesh J. Sci. Ind. Res. 49(3), 147-154, 2014

An Experimental Study of PCM-Incorporated Thermosyphon Solar Water Heating System

In the contemporary era, phase change material (PCM) is used in solar water heaters to store the extra amount of heat energy available during the full sunshine hours. The primary purpose of this study is to examine the performance of PCM-incorporated thermosyphon solar water heating system using flat plate collector as a heat source. In this study, a cylindrical aluminium PCM tank acts as a thermal energy storage unit. It is employed in the top portion of the insulated storage tank containing water. Paraffin wax is used as a PCM. Water is used as heat transfer fluid (HTF) to transfer heat from flat plate collector to storage tank. The charging and discharging experiments are carried out on clear days with and without PCM under actual operating conditions. The significance of time wide variation of HTF and PCM temperatures during experiments are discussed in detail and the performance parameters, such as charging energy efficiency, stratification number, and thermal efficiency, were also studied. The simulation of the discharging experiments is done in Computational Fluid Dynamic for validation purpose. It is shown from the experiments that the PCM improves the performance of the system by bettering stratification number, charging energy efficiency, and thermal efficiency of storage tank.

Using TRNSYS Simulation to Optimize the Design of a Solar Water Distillation System

We present the modeling, TRNSYS simulation, and parametric analysis of a solar water distillation system based on a humidification-dehumidification cycle. The thermal processes that constitute the cycle are carried out in devices designed for maximum individual efficiency. In order to achieve this, it is necessary for the evaporative process (in which an air current is humidified) to happen at the highest temperature attainable without boiling. This maximizes the amount of vapor that can be carried by the air current. This process is performed in a vertical packed column, where a stream of hot water falls as a current of hot air ascends in countercurrent and directly contacts the water. The air at the exit of the tower is saturated with vapor at the same temperature as the entering water, thus maximizing the amount of moisture carried. The hot and humid air then passes through a condenser that releases heat to the atmosphere, bringing air to nearly ambient temperature and maximizing distillate condensation. In order to achieve the previous, it is necessary for the thermal capture and storage system to work with thermal oil, an insulated storage tank, and evacuated-tube solar collectors. The system must maintain a steady oil temperature of 110°C. We propose a condenser based on heat pipes and with excess heat transfer area for dumping heat to the atmosphere, in order for the condensation temperature to be as close as possible to atmospheric. The efficiency of the distiller is substantially increased by forcing the process to occur between the described temperature limits, not unlike what happens in the power cycles of heat engines. The thermal oil transfers energy to the air and water currents through two heat exchangers, and the insulated storage tank makes it possible to operate the system at night for as long as sufficiently hot oil is still available. A flow control system regulates the temperature reached by the water that flows to the evaporation tower.We used the simulation platform TRNSYS to model this system, including the evaporation tower and condenser. Using the climatic conditions of the city of Chihuahua, Mexico, we performed a parametric study of the system and determined the effect of varying the number of solar collectors, volume of the thermal tank, and flow rate of water. We simulated the behavior of the system over a year of continued operation, measuring the amount of condensate produced during that period. The objective of this analysis was to determine the variation of distillate production, in kilograms of water distilled per year per square meter of solar collector, and per cubic meter of thermal tank. This was used to determine the optimal characteristics of the proposed distillation system.

Base-load Thermoelectric Power Generation Using Evacuated Tube Solar Collector and Water Storage Tank

The concept of using low temperature solar heated water to produce electricity is not new but so far very few attempts have been made to produce continuous power (24hours - 7days) from low grade solar thermal systems. In this study we are looking at continuous electricity production during not only sunny days but also night times and or cloudy days.Thermoelectric technology has a good potential for reliable electricity generation form low temperature heat source like solar heated hot water.A series of “electricity generation apparatus inside thermoelectric” abbreviated as ELEGANT have been designed and fabricated and the latest, ELEGANT-24 which produces almost 22 W(e) and comprises 24 market-available Peltier module, operating as generator, successfully operated for two months.Eight evacuated tube solar collectors are used to heat the water up and then store into an insulated storage tank during day time. In this period ELEGANT-24 uses outlet hot water of solar collectors, as a source of heat. Cold water from a non-insulated storage tank passes ELEGANT-24 in as coolant and gets preheated and then enters the solar collectors thru same non-insulated tank. This pre-heated water entered into the collector helps to improve the overall energy conversion efficiency of the whole system. Through this process heat is converted to electricity with minimum heat loss.This process can be continued during night time while hot water is supplied through circulating of insulated storage tank.As well as addressing base load power production, above configuration dramatically increases the efficiency of heat to electricity conversion via thermoelectric technology. This is due to that dissipated heat from cold side of TEGs would not be wasted and goes back to the heating circle. It means that except very small heat loss through walls of ELEGANT-24 and piping, there is no other heat loss.

Energy Labeling and Advanced Insulation for Thermal Energy Storages in Solar Applications

In order to reduce CO2 emissions related to heating purposes within the European Union, the EU-Commission is currently preparing ecodesign and energy-labeling requirements for water heaters, storage tanks, and space and combination heaters. Especially this also applies for solar assisted space heating and hot water preparation systems. In particular, there will be a new energy efficiency classification for solar hot water storage tanks, which will be rated (A+, A, B, C, …, G) according to their standing losses. We present a test set-up and procedure that is capable of determining the standing losses conform to the EU-directive and show various measurements of some state-of-the-art storage configurations. The results reveal the need for better insulation in order to achieve an A+/A-rating for state-of-the-art storage tanks. We compare the effects of employing an better insulated storage tank compared to state-of-the-art technology for a solar thermal systems by performing annual system simulations via TRNSYS. The system comprises of a 100% renewable space heating and domestic hot water pellet-solar combi-system suitable for residential buildings.

Design and Experimental Validation of Enhancing the Performance of PV Panel Integrated with Solar Water Heating System

The maximum electricity conversion efficiency of the Solar Photovoltaic panel is 8-18% under the Standard Test Condition (STC) temperature of 25˚C. The atmospheric temperature of Indian climatic condition is mostly above 30˚C - 45˚C, it incites 30˚C-80˚C heat over the panel since black body of the PV panel observe more heat, and this temperature majorly affect the electrical efficiency of the panel. The newly designed Glass to Glass Photovoltaic Thermal System (G2G-PVTS) is a combined Photovoltaic (PV) and Flat Plate Solar Water Heating System (FPSWHS). In this technology, the water act as a coolant inside the Copper fins and it absorb the heat of the PV panel and stored in the insulated storage tank by way of natural flow of water. The test result shows that the G2G-PVTS electrical efficiency was 0.7% higher than conventional G2T- PV panel, and in addition that 44.37% of thermal efficiency was also stored. The simultaneous conversion of electrical and thermal energy was obtained by this system with effective space utilization. The overall efficiency of the G2G-PVTS panel was improved

ENGINEERING FACTORS AFFECTING THE OUTLET WATER TEMPERATURE OF SOLAR WATER HEATER

The application of solar energy as a clean renewable source of energy in agricultural purposes has the major interest worldwide especially in countries with a high solar insolation. The aim of this study was to investigate the effect of some factors ; solar radiation incident, water flow rate, water inlet temperature, ambient air temperature and absorber plate temperature on outlet temperatur of the operating fluid. A solar heating system icludes a solar collector has an area of 2 m2, an insulated storage tank, a heat exchanger, a fluid distribution system and a control system was constructed and installed in Densosher village, El-Mehalla ElKobra, Gharbia Governorate at a latitude angle of 30.9 No. The collected data for this research restricted between 15 August and 25 September 2010. The statistical analysis, forward stepwise regression, revealed that the water inlet and the absorber plate temperatures had the major effect on the water outlet temperature as compared with the other parameters.

Energetic and exergetic performances of an economical and available integrated solar storage collector based on concrete matrix

This paper deals with an experimental study of an inexpensive integrated solar storage collector (ISSC) of total aperture area of 2 m 2, used for the providing of domestic hot water. The ISSC is characterised by an absorber matrix made up of a thin cement concrete slab which performs the function of both absorbing and storing of the solar thermal energy. Inside the concrete absorber was embedded a cooper pipe network. Outdoor experiments were carried out under varied environmental conditions for several days during three consecutive months (from November 2007 to February 2008). The experiments were carried out by measuring the climatic variables, temperatures in different parts of the collectors, and mass flow rates of water, during the test days. Based on these measurements, the behavior of the systems was analyzed by comparing exit temperatures, heat losses, and delivered useful energy. A detailed energy and exergy analysis was carried out for evaluating the thermal and optical performance, exergy losses as well as exergetic efficiency for ISSC under given operating conditions. Results shows that the integrated solar storage collector, having energetic and exergetic efficiencies of 32% and 23.5% respectively, provides acceptable stored thermal heat rate by supplying approximately 80% in domestic hot water requirements for a family composed of 5–6 persons. An economic evaluation was made considering the investment time recovery through the system. The results obtained from the ISSC system were compared with the results obtained from a high quality thermosyphon solar system composed of a flat-plate collector (with a total aperture area of 2 m 2) and its corresponding insulated storage tank (200 l), tested at the same time.

ICS solar systems with horizontal cylindrical storage tank and reflector of CPC or involute geometry

The use of a horizontal cylindrical water storage tank contributes to pressure resistant, low height and efficient ICS solar systems. These systems can satisfactorily achieve water heating when the cylindrical storage tank is combined with stationary CPC or involute type curved reflectors. The diameter of the cylindrical storage tank determines the length of the reflectors, the system depth and the ratio of the stored water per aperture area. In these solar systems the storage tank can be partially thermally insulated to suppress thermal losses from it to the ambience. We constructed four experimental models with truncated symmetric CPC reflectors, two with 90° and other two with 60° of acceptance angle, half of them without and half with a 1/4 thermally insulated storage tank cylindrical surface. In addition, we constructed two ICS systems with involute reflectors, with acceptance angle 180°, one without and the other one with a 1/4 thermally insulated storage tank. The six ICS systems were tested under the same weather conditions and without water drain, to determine their stored water temperature variation, mean daily efficiency and thermal losses during night. The results showed that CPC reflectors contribute to efficient operation of systems day and night, while involute reflectors mainly to the water heat preservation during night.