Condenser Water Pumps Research Articles

Smart control of air conditioning systems in manufacturing systems facing uncertainty

Enhancing energy use efficiency and reducing energy demand are important issues for industry and academe. Studies on the ventilation, and air conditioning (HVAC) system highlighted the optimization of individual devices, but did not fully consider global optimization. The heating and cooling mechanism of an HVAC system in the present study comprises multiple chillers, chilled water pumps, condenser water pumps, and cooling towers. This study proposes a smart control model of heating, ventilation, and HVAC systems in manufacturing systems to deal with dynamic indoor cooling demands and outdoor temperature changes. A stochastic mixed integer mathematical programming model optimizes the heating and cooling decisions of the HVAC system for energy conservation. This study also investigates a case of the HVAC system in a TFT-LCD manufacturing firm. Experiment results indicate that the proposed model saves up to 3.2% of total energy in the target HVAC system.

Overall chilled water system energy consumption modeling and optimization

The emergence of increasingly affordable variable-speed drive technology has changed the approach used to control chilled water systems equipped with these drives. The purpose of this research was to develop an integrated chilled water modeling technique that can determine the optimal system setpoints and estimate the energy saving potential of chiller system. The chiller system equipped with Variable Frequency Drives (VFDs) on cooling tower fans and condenser water pumps. To accomplish the objective, physical component models of the centrifugal chiller, cooling tower and condenser water pump were established with the goal of incorporating the system’s condenser water flow rate and cooling tower fan speeds as optimization variables. Furthermore, a cooling load prediction algorithm was developed using a multiple non-linear regression model to approximate the building’s cooling load subject to a range of environmental conditions. The inputs and outputs of the individual component models were linked to estimate how adjusting the cooling tower fan and condenser water pump speed would influence the system’s comprehensive performance. The overall system model was then optimized using a generalized reduced gradient optimization algorithm to determine the potential energy savings through speed control with VFDs and to ascertain a control logic strategy for the building automation system to operate the heating and cooling system. A case-study was performed on a single chiller system at a museum and the model was calibrated according to logged data collected over four months. Results showed that for the system analyzed, the energy saving of optimizing the cooling tower fan system was found to be 12–15%, while the energy saving potential of optimizing the condenser water pump with the cooling tower fan was negligible. Additionally, comparing different cooling tower fan control strategies showed that a wet-bulb approach-based cooling tower control strategy was shown to have the highest correlation to the optimized fan speed with an R2 of 0.924.

ANALISIS PENGGUNAAN DDC PADA SISTEM HVAC UNTUK MENINGKATKAN PENGHEMATAN KONSUMSI ENERGI DI HOTEL LANGHAM DISTRICT 8 SCBD JAKARTA

Heating System, Ventilanting and Air Conditioning (HVAC) or air conditioning systemsbecome one of the needs in high rise buildings in order to increase comfort in the room,differences in the level of comfort of each individual makes the HVAC system changes in loadpatterns that can result in wasteful use of electrical energy. This study aims to determine thesavings in the use of electrical energy with the use of DDC in the HVAC system at the Langhamhotel. DDC can regulate HVAC system supporting devices such as cooling towers, condenserwater pumps, chilled water pumps and chillers that aim to reduce the performance of the chillersso that energy savings are obtained. By using 2 work operation methods, the results of thecalculation of energy use obtained at the side of the chiller Langham hotel, with manualoperation without the use of DDC obtained a total consumption cost of IDR 3,409,290 andautomatic work operations using DDC obtained a total consumption cost of IDR 2,601,990 sothat it is obtained saving percentage of 24%.

Feasibility Study of Micro Hydropower Plants in High-Rise Buildings in Indonesia By Utilizing A Working Scheme for AC Condenser Water Pumps (Ventilation & Air Conditioning System)

In Indonesia the number of high-rise buildings above 150 m tends to increase, according to CTBUH (Council on tall building and urban habitat) in 2018 there are 85 buildings and those that are under construction are 26 buildings, Super tall buildings with a height above 300 meters are 4 buildings and proposed mega tall building with a height of more than 600 meters is 1 building. All these buildings have very large electrical loads. The percentage of electricity consumption in the building that is the object of research is 30-50% coming from the Ventilation & Air Condition (VAC) system, 20% - 30% lighting systems, 10% computers and the rest from other utilities. Several papers and journals discussing the simulation or feasibility study of micro-hydropower plants in high-rise buildings have not yet been discussed how to utilized kinetic energy from the working scheme of the water condenser pump in the VAC system. in general, the existing papers discuss how to utilized gravity potential energy through the working scheme of the building’s clean water tank which is on the roof (rooftop) when distributing water which is not optimal because of the flow of water from the clean water system is not continuous or steady-state. Research Object by taking a case study of a high-rise building in Jakarta with a height of 157 meters. The data was taken from the report on utility use for the 2018 period in the building. From the simulation, the potential of water flow rate (Q) is 0.499 m3 / sec and the electrical power that can be generated (P) is 733.83 kW and this is a Micro-hydro Power Generation category. Economic analysis for building energy savings of Rp. 541,765,714.29 / month and finally roughly Return on Investment (ROI) can be achieved in 3 years and 6 months.

Determinants of low energy performance in a multi-chiller system serving an educational premise

Abstract This study analyses an association between operating variables and low energy performance in terms of the coefficient of performance (COP) of a chiller system in daily operation. Year-round operating data were collected at 15-min intervals from a trend logging device for a system with five chillers of two different capacities. Two-step cluster analysis was applied to group operating data with high and low COP ratings. The odds ratio analysis ascertained that the key deficient control was operating extra chillers with one at particularly light loads. The optimal trade-off between the chiller power and condenser water pump power was not achieved due to the surplus operation of condenser water pumps. The low COP rating was also due to an imprecise control in the chilled water supply temperature and the condenser water entering temperature from their fixed set points. The significance of this study is to prioritize COP improvement opportunities by ranking the impact of deficient controls based on the actual configuration and operating practice of any given chiller system.

The optimal operation of cooling tower systems with variable-frequency control

This study investigates the energy performance of chiller and cooling tower systems integrated with variable-frequency control for cooling tower fans and condenser water pumps. With regard to an example chiller system serving an office building, Chiller and cooling towers models were developed to assess how different variable-frequency control methods of cooling towers fans and condenser water pumps influence the trade-off between the chiller power, pump power and fan power under various operating conditions. The matching relationship between the cooling tower fans frequency and condenser water pumps frequency at optimal energy consumption of the system is introduced to achieve optimum system performance.

Real-time optimization of a chilled water plant with parallel chillers based on extremum seeking control

Chilled water plants with multiple chillers are commonly used to provide cooling in large commercial buildings. Optimization offers a significant opportunity for improving the energy efficiency of such plants. Model based approaches used for control and optimization require accurate models, which can be difficult and/or expensive to obtain in practice due to large variations in equipment characteristics and operating conditions. In this paper, a model-free optimization strategy based on multivariate Extremum Seeking Control (ESC) with penalty terms is proposed for maximizing the energy efficiency of a chilled-water plant with parallel chillers. The feedback to ESC is the total power consumption of the plant consisting of chiller compressors, cooling tower fan, and condenser water pumps, in combination with penalty terms for input-saturation. The control inputs include the cooling tower fan airflow, condenser water flows and evaporator leaving chilled-water temperature setpoint. A band-pass filter array, instead of the high-pass filter in the standard ESC, is adopted to reduce the coupling among the input channels. The proposed strategy is evaluated with simulation study using a Modelica based dynamic simulation model of a chilled-water plant with two parallel chillers. Six cases are presented that demonstrate real-time optimization capability of ESC for this application.

Central Plant Control Optimization with a Thermal Chilled Water Energy Storage System: A Case Study in a High-Tech Building

The paper presents the study on the control optimization of the central cooling plant system including thermal chilled water energy storage (TES) tank in a high-tech building consists of office area, clean room and lab space. The optimized control sequences were implemented on the cooling tower staging, cooling tower fan/condenser water pump/primary chilled water pump staging and speed control, chiller staging, TES pump speed and TES modulation valves control, and secondary chilled water loop differential pressure control. The proposed control effectively resolved the problem of fluctuation in the secondary chilled water supply temperature during charging cycle and temperature increase during the discharging cycle. The number of primary chilled water pumps, condenser water pumps and cooling tower fans were also reduced to minimum after the optimization. Implementation of optimized control sequences is predicted to have an annual electricity savings of 856,125 kWh, which is about 20% of the total central plant energy consumption.

Investigation on variable flow control in existing water-cooled chiller plant of high-rise commercial building in subtropical climate

An all-variable-speed chiller plant has been advocated so that the chillers and their associated pumps can work at reduced speed during part-load conditions for energy saving purposes. In this new building project, the savings merit is certainly attractive. However, an existing chiller plant or retrofit project, which is constrained by the performance of installed equipment and the configuration of a hydronic circuit, may not benefit from the an ideal extent of savings. As such, an existing chiller plant serving a typical commercial building was used to evaluate this. Through year-round dynamic simulation, it is found that there were about 5%, 6%, and 8% energy savings of the whole chiller plant when applying variable flow control on secondary chilled water pumps only, both primary and secondary chilled water pumps, and all chilled and condenser water pumps, respectively. If constant-speed centrifugal chillers were substituted by the variable-speed ones, an additional 4% savings could be achieved, which was, however, less than that incurred from the associated pumps. The payback periods of different variable flow control strategies were well below 1 year, indicating the techno-economical feasibility for wider application in existing chiller plants in subtropical climates.

Using cluster and multivariate analyses to appraise the operating performance of a chiller system serving an institutional building

This study explains how to appraise the operating performance of a chiller system using cluster and multivariate analyses. Cluster analysis is a statistical tool used to identify groups of individuals similar to each other but different from individuals in other groups. This serves the purpose of classifying what operating condition constitutes a high or low system coefficient of performance (COP). A case study has been carried out on a system with five sets of chillers, pumps and cooling towers. Each operating condition to be clustered involves the following variables: the load of each operating chiller, the total system load, the number of primary chilled water pumps running, the number of condenser water pumps running and the number of cooling towers operating. The two-step cluster analysis was applied to group around 6800 sets of operating conditions into three clusters with distinct operating characteristics. For each clustered data, a multivariate analysis was made to examine the degree of correlation between the system coefficient of performance (COP), the operating variables and typical weather parameters. The significance of this study is to demonstrate a systematic method to ascertain if a chiller system operates under optimal control with maximum COP and to estimate COP improvements if operating problems are rectified.

Optimal supervisory control of a central chilled water plant with heuristic search sequential quadratic programming

A new methodology for adapting rigorous simulation programs to optimal supervisory control of a central chilled water plant is proposed in this article, which solves plant operation mode optimization and set points optimization by combining heuristic search with sequential quadratic programming. The mathematical basis of this algorithm is developed. A new derivative calculation strategy is introduced in set points optimization. This approach is applied to a central chilled water plant which consists of three chillers, two 3-cell cooling towers, three chilled water pumps and three condenser water pumps. Model verification study is performed. The optimal sequence of operation, set points of the decision variables at given load demand and weather condition are calculated. The plant performance and optimal control results are discussed.

ENTROPY METHOD AS CRITERIA FOR ANALYSIS A STEAM POWER PLANT

In this paper a theoretical analysis of South Baghdad and Dura power plant is carried out according to second law of thermodynamic depending on entropy (irreversibility coefficient or lost work) method instead of exergy (availability) method. In the used entropy method. The power plant is divided into main blocks ( boiler, turbine, condenser, and feed water heater and pumps ). The irreversibility losses and coefficient for each block are calculated and then the overall irreversibility and thermal efficiency of the plant are calculated. The results of this work are compared with previous results, that depending on exergy method. The comparison of results show that both methods give approximately the same results since both of them rely the 2nd law of thermodynamic. Entropy method is simple and intellectually and intuitively satisfying and giving direct relationship between components losses of power plant and its overall efficiency.

Economic benefits of optimal control for water-cooled chiller systems serving hotels in a subtropical climate

A water-cooled chiller system in an air-conditioned hotel can take up about one-quarter of the total electricity consumption and considerable amounts of water in the heat rejection process. This paper evaluates operating cost savings of a chiller system integrated with optimal control of cooling towers and condenser water pumps. A sophisticated chiller system model was used to ascertain how different control methods influence the annual electricity and water consumption of chillers operating for the cooling load profile of a reference hotel. It is estimated that applying load-based speed control to the cooling tower fans and condenser water pumps could reduce the annual system electricity use by 8.6% and operating cost by 9.9% relative to the equivalent system using constant speed fans and pumps with a fixed set point of 29.4 °C for cooling water temperature control. The ways to implement this advanced control for system optimization are discussed.

Optimization of water-cooled chiller system with load-based speed control

This study investigates the energy performance of chiller and cooling tower systems integrated with variable condenser water flow and optimal speed control for tower fans and condenser water pumps. Thermodynamic-behaviour chiller and cooling tower models were developed to assess how different control methods of cooling towers and condenser water pumps influence the trade-off between the chiller power, pump power, fan power and water consumption under various operating conditions. Load-based speed control is introduced for the tower fans and condenser water pumps to achieve optimum system performance. With regard to an example chiller system serving an office building, the optimal control coupled with variable condenser water flow could reduce the annual system electricity use by 5.3% and operating cost by 4.9% relative to the equivalent system using constant speed fans and pumps with a fixed set point for cooling water temperature control.

Turning Capital Projects Into Energy Projects

Many commercial and institutional facilities have ongoing capital projects for replacing old equipment, ongoing maintenance, and expansion. Many of these projects are carried out with a focus on first cost, simplicity, and expediency, at the expense of and operational improvement. This article will describe how a typical capital project for New York Presbyterian Hospital (NYPH) was re-focused to become an savings project by broadening the scope beyond the mechanical room, shifting capital to savings measures, and taking advantage of incentives to offset costs. Key to the effort was the hospital's aggressive program to reduce its costs through conservation. These efforts have earned the hospital the Energy Star Partner of the Year award for 2004 and 2005. The original project scope was the replacement of air conditioning units with higher tonnage units, duct cleaning, and other maintenance efforts. An energy focused analysis of the building, including an model for the occupied space, recommended high efficiency, smaller air conditioners, retro-commissioning of the air distribution system, variable frequency drives on condenser water pumps, and an management system in lieu of duct cleaning. The recommendations added little cost to the project and identified the potential to save over 1,500,000 kWh a year in electrical energy. In addition, approximately $200,000 in incentives were identified for the project under the New York State Energy Research and Development Authority's (NYSERDA's) Commercial and Industrial Performance Program (CIPP) and Peak Load Reduction Program (PLRP). This article will compare the project scope and cost before the analysis and after the analysis. The conservation measures identified for the project and the M&V strategies used to confirm the savings will be discussed, along with some of the pre- and post-installation data.

ENTROPY METHOD AS CRITERIA FOR ANALYSIS OF A STEAM POWER PLANT

ENTROPY METHOD AS CRITERIA FOR ANALYSIS OF A STEAM POWER PLANT

Thermoeconomics applied to an air conditioning system with cogeneration

This paper indicates the method for applying a thermoeconomic analysis to a theoretical building services study, consisting of an air conditioning system using a single-stage absorption chiller driven by a cogeneration engine. The gas engine supplies heat to the absorption chiller and electricity to other HVAC plant, such as dry cooler fans, hot water, condenser and chilled water pumps, air handling units and fan-powered terminal units. The thermoeconomic model is used to optimise the specific cost of indoor environment cooling in terms of the absorption chiller variables, chilled water and condenser water temperatures. An improved design is obtained in two steps. First the design conditions are optimised, providing detailed exergy costing related to the plant investment and operating costs. Secondly, by analysing these, the most appropriate design modification of substituting dry coolers with a cooling tower is identified, and the system is again optimised, achieving 6% more cooling capacity while reducing the final specific cooling energy cost by 35%. This results in an improved thermal and economic design for the owner.

Absorption chillers applied to CHP systems

The parameters that should be considered at the design stage of a combined heat and power (CHP) project have been determined for situations when absorption refrigeration is to be used. Single and double stage chillers are considered together with system features such as hot water, steam or heat recovery driven, in terms of the hot temperature heat source from the CHP plant. Finally the chiller efficiency, plant size and the electric consumption of cooling towers and condenser water pumps are analysed to achieve an energy efficient system design.