Cold Water Storage Tanks Research Articles

Reducing Peak Thermo-Electricity Energy Demand in Building: Insights from Sensible and Latent Storage – Applicable in hot and arid regions

In hot and desert regions, buildings have a considerable share in electricity consumption, so supplying electricity in critical hours for building cooling is always challenging for the electricity supply grid. In this numerical study, using sensible and latent-based storage approaches, the goals of peak shaving and load shifting were pursued. The sensible-based approach (first technique) was followed by adding a cold water storage tank which is responsible for cooling the building during critical hours. The tank is charged by the chiller during off-peak hours. The latent-based approach (second technique) was achieved through phase change materials (PCMs) integrated into building envelopes. Owing to using the sensible-based approach, not only was the electricity consumption completely cut during critical hours, but the peak hour was postponed to the early hours of the next day (i.e., load shifting). Based on the results, using the first technique does not necessarily lead to peak shaving. To follow the goal of peak shaving, the use of the second technique is recommended. The simultaneous use of both approaches made the building meet the cooling requirements during critical hours without receiving electricity from the supply grid. Moreover, the building receives up to 54.9% less electricity from the grid (peak shaving), and simultaneously peak hour was postponed by at least 6 hours (load shifting).

DEVELOPMENT AND INSTALLATION OF SOLAR WATER HEATING SYSTEM FOR FEDPODAM HOSTEL

This paper presents the result of the Development, Installation and Performance evaluation of a 500 liter capacity hot water storage tank with an additional 500 liter capacity cold water storage tank that was, developed, installed and tested at Maryam Abatcha female hostel in the Federal Polytechnic Damaturu, Yobe State, Nigeria which is located at latitude 12.290N and Longitude 11.440E using available materials and thermo syphon principle at an average solar radiation of 630W/m2 to investigate the potential of using solar either directly and indirectly for heating water and to compare its cost with electricity. This design utilized a flat plate collector which was chosen because of the simplicity in construction and ease of maintenance. Two collectors of 1m2 each with single glazing were used as a heat exchanger. The surfaces of the collectors were painted with black paint of absorptivity 0.95 and emissivity of 0.09 to improve its absorption capacity. Readings were taken for a period of nine months starting from March, April, May, June, July, August, September, October and November with minimum ambient temperature of 320C. Maximum hot water temperature inside the tank as 82.30C with an average efficiency of 28.06% in June, with clear sunny atmosphere days and November with lower outlet likely due to cold dusty of the period. Test conducted reveal that the system could satisfy the hot /warm water requirements of the hostel. It was also observed that the water temperature is a function of solar radiation while the cloud cover and dust particles were observed to also affect the performance of solar water heating system thereby reducing its efficiency.

An advanced control strategy of hybrid cooling system with cold water storage system in data center

The inefficient operation of cooling equipment is a significant impact factor to the high energy consumption of cooling system in data center. This study proposes an advanced model predictive control (MPC) strategy for a hybrid cooling with water storage system to improve energy efficiency and reduce the accumulation of cold storage losses. Mixed integer linear programming (MILP) in MPC strategy is used to optimize the operating parameters under free cooling, hybrid cooling, and mechanical cooling modes, further solving the problem of precise optimization for different modes. Taking Guangzhou city as an example, the equipment scheduling and the appropriate volume of cold water storage tank for MPC strategy are analyzed. The results indicate that, the emergency cold water storage tank 500 m3 only supports the efficient operation of cooling system under the maximum 60 % IT load rate, meanwhile, the optimal tank volume 1400 m3 could meet the 60–100 % IT load rate. Compared to Baseline strategy, the biggest reduction of annual energy consumption using MPC strategy would be attained by 12.19 % under free cooling mode, by 4.04 % under hybrid cooling mode, and by 22.15 % under mechanical cooling conditions at the 55 % IT load rate. Therefore, the MPC strategy proposed in this paper has important guiding significance for energy conservation and carbon reduction in global data centers.

Cold water storage tank enhancement using response surface methodology leading cooling peak shaving along with load shifting

In hot areas, electricity consumption in the cooling sector holds 66% of the electricity usage by residential buildings. The need for electricity during peak times causes various problems in the electricity supply network. Adding a cold water storage tank can achieve two goals: 1- peak load shifting and 2- peak load shaving. In this study, first, the volume of the storage tank was calculated by energy analysis for the day with the maximum cooling needs. Owing to installing the tank, the electricity consumption not only reaches zero during the peak time (7 a.m.–11 p.m.) but also the total electricity demand decreases by 5.1%. According to the ASHRAE, throughout the 8760 h in one year, the deviation of the interior temperature from the setpoint should not exceed the 300-h threshold (i.e., unmet hours <300 h). Considering the allowable amount of unmet hours as a constraint, optimal points were acquired using Response Surface Methodology (RSM). This method reduces the cold storage tank by 40% and decreases the electricity need by 16.5% compared to the reference case (without a storage tank). Furthermore, the optimal storage tank eliminates the cooling-associated electricity demand to zero during peak periods.

Proposal and 3E (energy, exergy, and exergoeconomic) assessment of a cogeneration system using an organic Rankine cycle and an Absorption Refrigeration System in the Northeast Brazil: Thermodynamic investigation of a facility case study

This paper proposes a cogeneration system to achieve the partial electric and thermal demands of a building in the public University. This proposed system comprises an Internal Combustion Engine (ICE), an organic Rankine cycle (ORC), and equipment that will operate as a sink. For the latter, two types of equipment were selected: a cooling tower and an Absorption Refrigeration System (ARS). The building selected to propose the cogeneration system is the Institute of Sustainable Energies (IES), located at the Federal University of Paraíba (UFPB), in the Northeast of Brazil. The performance of the system based on energetic and exergetic points of view operating under two distinct modes; ORC Simple (ORC-S) and ORC Combined (ORC-C), was compared. Both modes are based on the energy availability of the ICE exhaust gases. The thermodynamic models for both modes were developed based on the first and second laws of thermodynamic considering input parameters, such as inlet temperature, pressure ratio, and outlet temperature of the expander and the cold-water storage tank. For the exergoeconomic technique, the SPECO Method (Specific Exergy Costing) was used and implemented along with the Thermodynamic model. The ORC system studied uses a scroll expander and operates with R-134a as the working fluid and water/ammonia pair for the single-effect ARS. The results showed that the ORC-C mode can meet from 18.9% to 37.5% of the IES electricity demand, while the ORC-S mode can meet from 12.4% to 24.5%. The thermodynamic analysis reported that the ORC-C allowed a 33.6% increase in mechanical power production, an increase from approximately 4.5% to 34.5% in energy efficiency as well as exergy efficiencies around 40% and reduction of the total destroyed exergy. From the exergoeconomic point of view, the specific cost of the chilled water has a slight influence on the total cost of the products, while the specific cost of hot water has a strong influence on the total cost of the products (a variation of approximately 46% for a distinct heat source).

DESIGN OF TANDON AND AUTOMATIC FILLING TOOLS ON DISPENSERS WITH ULTRASONIC SENSORS

Nowdays, The development of water dispensers has hot and cold water technology, but fills water into cold and hot water storage tanks by lifting and putting the gallons on top of the dispenser so that water can flow into hot and cold water storage tanks, this is assessed less efficient. The purpose of making this tool is to make it easier for users to install gallons without having to lift the gallon and put it on top of the reservoir, it can also facilitate the taking of drinking water without having to press or open the faucet first. Because in modern era, the need for tools that work automatically and efficiently are increasing. The results of this study indicate that automatic water and faucet filler devices in dispensers using ultrasonic sensors as a whole work well and are in accordance with the function specified. The function of the ultrasonic sensor is as a reader the maximum limit of water level in the reservoir, so that when the water is in its maximum state, the pump will stop filling the reservoir. And the ultrasonic sensor in front of the dispenser functions to read the glass, the sensor will detect and then be received by the microcontroller and continue to execute the relay and open the selenoid so that the water can come out.

Modelling and predictive control of a solar cooling plant with flexible configuration

This paper focuses on the modelling and predictive control of a real medium temperature solar cooling system made up of a solar collector, an absorption chiller, a gas heater, hot and cold water storage tanks, connecting pipes, pumps, and a number of valves, allowing to modify the plant configuration in order to optimize its performance in terms of electric power and gas consumption. A detailed model of the plant is first obtained as a mix of first principle equations, validated with data collected on the plant, and identification techniques. Then, the model is simplified and used to formulate a hybrid Model Predictive Control (MPC) problem computing the optimal plant configuration over a prediction horizon of six hours, or more, and based on the available forecast of the solar radiation and user demand. The developed MPC algorithm has been used to control the plant; some of the collected results are reported here to witness the potentialities of the proposed approach.

Present-day monitoring underestimates the risk of exposure to pathogenic bacteria from cold water storage tanks.

Water-borne bacteria, found in cold water storage tanks, are causative agents for various human infections and diseases including Legionnaires’ disease. Consequently, regular microbiological monitoring of tank water is undertaken as part of the regulatory framework used to control pathogenic bacteria. A key assumption is that a small volume of water taken from under the ball valve (where there is easy access to the stored water) will be representative of the entire tank. To test the reliability of this measure, domestic water samples taken from different locations of selected tanks in London properties between November 2015 and July 2016 were analysed for TVCs, Pseudomonas and Legionella at an accredited laboratory, according to regulatory requirements. Out of ~6000 tanks surveyed, only 15 were selected based on the ability to take a water sample from the normal sampling hatch (located above the ball valve) and from the far end of the tank (usually requiring disassembly of the tank lid with risk of structural damage), and permission being granted by the site manager to undertake the additional investigation and sampling. Despite seasonal differences in water temperature, we found 100% compliance at the ball valve end. In contrast, 40% of the tanks exceeded the regulatory threshold for temperature at the far end of the tank in the summer months. Consequently, 20% of the tanks surveyed failed to trigger appropriate regulatory action based on microbiological analyses of the water sample taken under the ball valve compared to the far end sample using present-day standards. These data show that typical water samples collected for routine monitoring may often underestimate the microbiological status of the water entering the building, thereby increasing the risk of exposure to water bourne pathogens with potential public health implications. We propose that water storage tanks should be redesigned to allow access to the far end of tanks for routine monitoring purposes, and that water samples used to ascertain the regulatory compliance of stored water in tanks should be taken at the point at which water is abstracted for use in the building.

Modelling and testing a passive night-sky radiation system

The as-built and tested passive night-sky radiation cooling/heating system considered in this investigation consists of a radiation panel, a cold water storage tank, a hot water storage tank, a room and the interconnecting pipework. The stored cold water can be used to cool a room during the day, particularly in summer. A theoretical time-dependent thermal performance model was also developed and compared with the experimental results and it is shown that the theoretical simulation model captures the experimental system performance to within a reasonable degree of accuracy. A natural circulation experimental set-up was constructed and subsequently used to show that under local (Stellenbosch, South Africa) conditions the typical heat-removal rate from the water in the tank is 55 W/m2 of radiating panel during the night; during the day the water in the hot water-storage tank was heated from 24 °C to 62 °C at a rate of 96 W/m2. The system was also able to cool the room at a rate of 120 W/m3. The results thus confirmed that it is entirely plausible to design an entirely passive system, that is, without the use of any moving mechanical equipment such as pumps and active controls, for both room-cooling and water-heating. It is thus concluded that a passive night-sky radiation cooling/heating system is a viable energy-saving option and that the theoretical simulation, as presented, can be used with confidence as an energy-saving system design and evaluation tool. Keywords: passive cooling and heating, buoyancy-driven fluid flow, theoretical simulation, experimental verification Highlights:Passively driven renewable energy heating and cooling systems are considered.Time-dependent mathematical simulation model is presented.Experimental buoyancy-driven heating and cooling system built and tested.Experimental results demonstrate the applicability of the theoretical simulation model.Saving and evaluation design tool.

The role of the saver in a HPLCs heat transfer process: a transient analysis

This work describes the experimental validation of a mathematical model implemented in Matlab/Simulink®, which is used to investigate energy consumption in the production process of high-pressure laminate composites (HPLCs). First, experimental onsite temperature measurements are used to determine parameters for the core component, i.e. the package, consisting of several layers of different materials. These otherwise hard to assess quantities are the generated power due to exothermal reactions in the cross-linking phase, and the piecewise approximation for the variable heat capacity of the impregnated paper over the heating phase of the process. The capability of the whole model (including the hot and cold water storage tanks) to replicate the behaviour of the actual production process has been verified. The validated model has been employed to investigate the influence of a saver tank for the spent hot water to be employed in the early stage of the heating phase of the process, with the load and discharge phases lasting three or five minutes each. Computations demonstrate that significant savings in energy (up to 34) can be obtained.

A Solar Heating and Cooling System in a Nearly Zero-Energy Building: A Case Study in China

The building sector accounts for more than 40% of the global energy consumption. This consumption may be lowered by reducing building energy requirements and using renewable energy in building energy supply systems. Therefore, a nearly zero-energy building, incorporating a solar heating and cooling system, was designed and built in Beijing, China. The system included a 35.17 kW cooling (10-RT) absorption chiller, an evacuated tube solar collector with an aperture area of 320.6 m2, two hot-water storage tanks (with capacities of 10 m3 and 30 m3, respectively), two cold-water storage tanks (both with a capacity of 10 m3), and a 281 kW cooling tower. Heat pump systems were used as a backup. At a value of 25.2%, the obtained solar fraction associated with the cooling load was close to the design target of 30%. In addition, the daily solar collector efficiency and the chiller coefficient of performance (COP) varied from 0.327 to 0.507 and 0.49 to 0.70, respectively.

Design optimization of a residential scale solar driven adsorption cooling system in upper Egypt based

This study provides a decision support approach for selecting the best size of the main components of a small scale solar assisted, silica gel-water, adsorption cooling system in arid areas located in Assiut, Egypt. To achieve the objective of this work, an optimization based on a computer simulation has been performed on the design variables, which are: solar collector area, the volume of the hot storage tank, the volume of the cold storage tank, and thermostat set point of the auxiliary heating element. Economic and environmental evaluations of the proposed systems have been performed as well. A validation of the model results is performed with the experimental results of solar driven silica gel-water adsorption cooling system at Assiut University Campus which has worked since 2012. The results show that the tilt angle of 5° for the surface of the solar collectors achieved the best absorbed solar radiation by the collector filed. For all proposed systems, the solar fraction did not affect the volume of the cold water storage tank while it has a significant effect on the area of the solar collector field and as well as the volume of the hot water storage tank. The initial cost of the proposed systems ranges from 2897€/kWc to 4808€/kWc and this can be considered as a hindrance to spreading at the commercial level. Meanwhile, the running cost over a year achieves low values, and it ranges from 13.9€/kWc to 99.11€/kWc.The proposed systems of lower solar fraction give lower carbon dioxide emissions. The carbon dioxide emissions range from193kg of CO2eq./kWc per year for the fully solar driven cooling system to 1062kg of CO2eq./kWc per year for the cooling system fully driven by natural gas. Based on the solar saving approach the proposed system of 24m2 solar collector area, 0.6m3 hot storage tank, and 1m3 cold storage tank with 94°C auxiliary heater set-point temperature can be considered as the most economically feasible solution.

Central air conditioning based on adsorption and solar energy

Abstract This paper presents the characterization and the pre-dimensioning of an adsorption chiller as part of a 20 kW air conditioning central unit for cooling a set of rooms that comprises an area of 110 m2. The system is basically made up of a cold water storage tank supplied by an activated carbon–methanol adsorption chiller, a hot water storage tank, fed by solar energy and natural gas, and a fan-coil. During an acclimatization of 8 h (9–17 h), the following parameters were obtained for dimensioning the cooling system: 504 kg of activated carbon, 180 L of methanol, 7000 L of hot water, 10,300 L of cold water with its temperature varying in the fan-coil from 1 °C to 14 °C. Considering the mean value of the total daily irradiation in Joao Pessoa (7°8′S, 34°50′WG), and a cover of regenerating heat supplied by solar energy equivalent to 70%, the adsorption chiller’s expected coefficient of performance (COP) was found to be around 0.6.

Natural occurrence of aflatoxins and Aspergillus flavus (Link) in water.

Aflatoxins were detected and Aspergillus flavus was identified from water from a cold water storage tank. This is the first published report of such data from water.

Isolation of Legionella pneumophila from the cold water of hospital ice machines: implications for origin and transmission of the organism.

Although the mode of transmission of L. pneumophila is as yet unclear, the hot water distribution system has been shown to be the reservoir for Legionella within the hospital environment. In this report we identify a previously unrecognized reservoir for L. pneumophila within the hospital environment, ie, the cold water dispensers of hospital ice machines. The cold water dispensers of 14 ice machines were cultured monthly over a 1-year period. Positive cultures were obtained from 8 of 14 dispensers, yielding from 1 to 300 CFU/plate. We were able to link the positivity of these cold water sites to the incoming cold water supply by recovering L. pneumophila from the cold water storage tank, which is directly supplied by the incoming municipal water line. This was accomplished by a novel enrichment experiment designed to duplicate the conditions (temperature, sediment, stagnation, and continuous seeding) of the hot water system. Our data indicate that significant contamination of cold water outlets with L. pneumophila can occur. Although no epidemiologic link to disease was made, the fact that the primary source of a patient's drinking water is from the ice machines warrants further investigation of these water sources as possible reservoirs.

Applications of a Heat Pump System to Greenhouse Environmental Control

The operating characteristics of a heat pump system for greenhouse cooling in summer nights were tested. The system consists of a water-to-water heat pump, two cold water storage tanks, and two water-to-air heat exchangers (Fig. 1). The water tanks were of temperature stratification type, in which the temperature gradient was clearly made.The system was installed in a plastic greenhouse in which the seedlings of a tomato crop had been growing. The ground water was used as the heat source for the heat pump.When the water temperature at the upper part of the water storage tank was above 15°C, the heat pump was operated and the ground water was pumped into the evaporator of the heat pump. The chilled water was then stored in the water storage tanks even in a daytime.When the air temperature inside the greenhouse was above the setpoint for cooling at night, the air-to-water heat exchangers were operated and the chilled water in the water storage tanks was pumped into the heat exchangers for cooling. The water flowed out from the heat exchangers was returned back to the upper part of the water storage tank and the returned water was used as the cooling water of the condenser of the heat pump.The measurements were carried out from August 21st to 27th 1984. The results can be summarized as follows:(1) Coefficient of performance of the heat pump for the cooling operation, COPr defined in eqs. (1) and (2), decreased from 3.5 to 2.6 with increasing temperature difference between the water in the condenser and in the evaporator (Fig. 2). In order to increase the COPr, firstly, the ground water should be used as the cooling water of the condenser. Because, the ground water temperature is always lower than that of the water flowed from the upper part of the water storage tank. Secondly, the water flow rates at the condenser and at the evaporator should be increased. Thirdly, the water temperature at the evaporator should be controlled at higher temperatures, as far as the air temperature inside the greenhouse can be maintained at the set point temperature for cooling with the higher water temperatures.(2) Coefficient of performance of the system, COPrs defined in eqs. (3), (4), and (5), ranged from 1.4 to 2.0 (Table 3). The value will increase with increasing the COPr. Because, the COPrs is strongly dependent upon the COPr.(3) The heat pump cooling system with the water storage tanks has smaller capacity of heat pump than the system without the tanks. However, for the system with the tanks, it would be important to minimize the heat loss from the water storage tanks.(4) The latent heat cooling load ranged from 13% to 45% of the total cooling load (Table 4). Furthermore, the latent heat cooling load due to air infiltration ranged from 38% to a maximum of 90% of the total latent heat cooling load. Therefore, in order to minimize the cooling load of the greenhouse, the greenhouse should be made air-tight.(5) Amount of condensed water at water-to-air heat exchanger decreased with decreasing the temperature difference between the dew point of the inside air and the water flowed in the water-to-air heat exchanger (Fig. 3). Therefore, by raising the temperature of the water pumped into the water-to-air heat exchanger, latent heat cooling load and hence total cooling load can be decreased. In addition, by raising the temperature of the water pumped into the water-to-air heat exchanger, COPrs can also be increased.(6) The relative humidity in the cooled greenhouse was close to that in the control (uncooled) greenhouse (Fig. 4).(7) With this system, the air temperature distribution in the greenhouse was fairly uniform, mainly because the cooled air was circulated in the greenhouse by the fan of the water-to-air heat exchanger.

WATER-BORNE OUTBREAK OF CAMPYLOBACTER GASTROENTERITIS

An outbreak of gastroenteritis affecting 234 pupils and 23 staff at a boarding school occurred over a period of 8 weeks. Campylobacter spp. were isolated from pupils and staff, and from two samples of cold water taken from an open-topped storage tank which supplied predominantly unchlorinated water to the main school building. The two isolates from water were of the same serotype. This serotype was the commonest of the three serotypes of Campylobacter jejuni detected in isolates from pupils and staff. There was a highly significant association between consumption of water from the cold water storage tank and reported illness in staff. Attack rates in pupils corresponded closely with the extent of distribution of this water-supply to the main residential houses. Contamination of water by faecal material from birds or bats was the most likely source of infection.