No description available.

Vapor compression cooling systems are the primary method used for refrigeration and air conditioning, and as such are a major component of household and commercial building energy consumption. Application of advanced control techniques to these systems is still a relatively unexplored area, and has the potential to significantly improve the energy efficiency of these systems, thereby decreasing their operating costs. This thesis explores a new method of decentralizing the capacity control of a multiple evaporator system in order to meet the separate temperature requirements of two cooling zones. The experimental system used for controller evaluation is a custom built small-scale water chiller with two evaporators; each evaporator services a separate body of water, referred to as a cooling zone. The two evaporators are connected to a single condenser and variable speed compressor, and feature variable water flow and electronic expansion valves. The control problem lies in development of a control architecture that will chill the water in the two tanks (referred to as cooling zones) to a desired temperature setpoint while minimizing the energy consumption of the system. A novel control architecture is developed that relies upon time scale separation of the various dynamics of the system; each evaporator is controlled independently with a model predictive control (MPC) based controller package, while the compressor reacts to system conditions to supply the total cooling required by the system as a whole. MPC’s inherent constraint-handling capability allows the local controllers to directly track an evaporator cooling setpoint while keeping superheat within a tight band, rather than the industrially standard approach of regulating superheat directly. The compressor responds to system conditions to track a pressure setpoint; in this configuration, pressure serves as the signal that informs the compressor of cooling demand changes. Finally, a global controller is developed that has knowledge of the energy consumption characteristics of the system. This global controller calculates the setpoints for the local controllers in pursuit of a global objective; namely, regulating the temperature of a cooling zone to a desired setpoint while minimizing energy usage.

No description available.

Agriculture and Agri-Food Canada (AAFC), the Ontario Greenhouse Vegetable Growers Association (OGVG), and Queen’s University’s Solar Calorimetry Laboratory (SCL) are undertaking a joint project to evaluate the energy and crop-yield benefits of operating commercial greenhouses in isolation from the outdoor environment, i.e., eliminating natural or forced ventilation to the exterior. Implementing such a scheme requires “closing” the greenhouse envelope and the installation of an active air-conditioning system to control temperature and moisture levels that could be harmful to crop growth. To this end, a prototype air-conditioning system, centered around a liquid desiccant dehumidifier, was designed, constructed and instrumented such that its thermal and functional performance could be evaluated over extended periods. The prototype unit was installed in a “research” greenhouse located at the Agriculture Canada, Greenhouse and Processing Crops Research Center (GPCRC) located in Harrow, Ontario. Both the novel air-conditioning and monitoring systems were implemented during the course of the thesis and operated for two preliminary crop trials to characterize system performance and identify aspects needing further refinement. Data obtained over these two initial periods, indicated that, the latent and sensible cooling capacity of the novel desiccant system averaged: 2.25 kW and -0.25 kW, respectively, during the severe summer trial; and 1.25 kW and -0.1 kW, respectively, during the milder spring trial. Values obtained from the preliminary monitored data also indicate that the liquid desiccant unit operated at electrical and thermal coefficients of performance (COPs) between 0.74 and 3.1 and between 0.15 and 0.52, respectively. Finally, using the monitored data, a simple regression-based empirical model was formulated to describe the average performance of the liquid desiccant unit. This was attempted to illustrate how performance results could be generalized to assist in the future design of similar commercial-scale systems. The results of this part of the thesis indicated, however, that further test data is required to confidently characterize the unit’s performance. As well, it was concluded that addition instrumentation (specifically, the addition of a meter to measure the flowrate of the regenerator air-stream) would enhance the potential to develop a practical performance correlation. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2013-11-01 14:12:54.326

This paper covers the simulation and comparison among three different HVAC (heating, ventilation & air conditioning)systems to achieve the goal of finding the most effective HVAC among these three in terms of human comfort, efficiency and cost considering North Texas climate. In the Zero Energy Lab at the University of North Texas, Denton, TX, the HVAC system of the building assembles with geothermal heat source. Here, water to water heat pump with radiant floor and water to air heat pump with air ducts provide heating & cooling of the building. In this paper electricity consumption, comfort, cost & efficiency analysis is done for the existing system using Energy Plus simulation software. Calibration of the simulated data of the existing system is done comparing with the actual data. Actual data is measured using 150 sensors that installed in Zero Energy Lab. After the baseline model calibration, simulation for ground source water to water heat pump, evaporative cooler with baseboard electric heater and water cooled electric chiller with baseboard electric heater (as a conventional system) is shown. Simulation results evaluate the life cycle cost (LCC) for these HVAC systems. The results of the comparison analysis among all the three HVAC systems show the most effective HVAC system among these three systems in North Texas weather. The results will make UNT Zero Energy lab a standard model towards a sustainable green future.

With the great possibility of offshore wind power that can be installed in the world seas, offshore wind power is starting to get and important source of energy. The growing sizes of wind turbines and a growing distance to land, makes the choice of transmission alternative to a more important factor. The profitability of the transmission solution is affected by many parameters, like investment cost and power losses, but also by parameters like operation & maintenance and lead time of the system. The study is based on a planned wind farm with a rated power of 1 200 MW and at a distance of 125 km to the connection point. Four models have been made for the transmission network with the technology of HVAC, HVDC and a hybrid of both. The simulation program used is EeFarm II, which has an interface in Matlab and Simulink. The four solutions have been compared technically, with difficulties and advantages pointed out and also economically, with the help of LCOE, NPV and IRR. Costs, power losses and availability of the wind turbines and intra array network are not included in the study. The result of the simulations implies that the HVAC solution is the most profitable with the lowest Levelized Cost of Energy and highest Net Price Value and Internal Rate of Return. The values are 25.11 €/MWh, 387.60 M€ and 15.32 % respectively. A HVDC model with just one offshore converter station, has a LCOE close to the HVAC solution, but with a more noticeable difference in NPV and IRR (25.71 €/MWh, 300.76 M€ and 14.84 % respectively). A sensitivity analysis has been done, where seven different parameters have been changed for analysing their impact on the economic result. The largest impact made was by a change in investment cost and lead times. The results imply that with a structure of the transmission network as for the models, and with similar input data, the break point where a HVDC solution is more profitable than a HVAC solution is not yet passed at a distance of 125 km from the connection point. With an evolving technology in the field of HVDC, a shorter lead time and lower investment cost could mean that a HVDC solution would be more profitable at this distance. Difficulties for a HVAC solution with more cable required, like bigger land usage and cable manufacturing as a bottle neck, could make an important factor tough while making a decision. / Med den stora potentialen hos världens hav, börjar havsbaserad vindkraft bli en betydande energikälla. Den ökande storleken på vindkraftsturbinerna tillsammans med de ökade avstånden mellan vindkraftsparkerna och land, gör att transmissionslösningen blir en mer betydelsefull komponent. Flera olika parametrar kan vara avgörande för transmissionslösningens lönsamhet, som investeringskostnad och effektförluster, men också saker som drift & underhåll och projektets ledtid. Studien är baserad på en planerad vindkraftspark med en märkeffekt på 1 200 MW och på ett avstånd på 125 km till anslutningspunkten. Fyra modeller av transmissionssnätet har gjorts, där tekniken har bestått av HVAC, HVDC samt en blandning av dessa. Simuleringarna har gjort i EeFarm II, ett program baserat på Matlab och Simulink. De fyra modellerna har jämförts tekniskt, med för- och nackdelar poängterade, och även ekonomiskt med hjälp av LCOE, NPV och IRR. Kostnader, effektförluster och tillgängligheten för vindkraftsturbinerna och internnätet i vindkraftsparken är inte inkluderade i studien. Resultaten av simuleringarna visar på att HVAC-lösningen är den mest lönsamma, med lägst Levelized Cost of Energy och högst Net Price Value och Internal Rate of Return. Värdena för dessa är 25,11 €/MWh, 387,60 M€ respektive 15,32 %. En HVDC-lösning med enbart en DC-plattform och likriktarstation för hela märkeffekten, har en LCOE inte långt ifrån HVAC-lösningen, men med en lite större skillnad i NPV och IRR (25,71 €/MWh, 300,76 M€ respektive 14,84 %). För att analysera påverkan av olika parametrar på de ekonomiska mätvärdena, har en osäkerhetsanalys gjort. Den största påverkan på resultatet syntes av förändringar av investeringskostnader och ledtider. Ovanstående resultat tyder på, med transmissionslösningar enligt modellerna i detta arbete, att brytpunkten där en HVDC-lösning är mer lönsam än en HVAC-lösning inte än är passerad vid ett avstånd på 125 km till anslutningspunkten. Med en fortfarande väldigt ung teknik för HVDC, kan den ständigt utvecklande tekniken i framtiden betyda kortare ledtider och en lägre investeringskostnad för en HVDC-lösning och möjligheten att vara en mer lönsam lösning. Komplikationer med en HVAC-lösning pga den extra landkabeln, som större landanvändning och med kabeltillverkningen som en flaskhals, kan ändå göra en HVDC-lösning mer praktisk.

In warm and humid climates, a primary source of building energy consumption is dehumidification of conditioned air supplied to the building spaces. The proposed system utilizes a selective membrane to remove water vapor from ambient air as opposed to a vapor compression cycle or a desiccant. This work provides an analysis of the membrane dehumidification system with a focus on the energy performance of the system. A system performance goal was set at the beginning for a given inlet and outlet ambient air condition and a total cooling load of one ton. The target COP of the combined sensible and latent cooling is 3.58 with a target value for only the latent system of 3.34. Two different simulations were developed including an initial simulation which uses a basic mass transfer model and a simpler condenser model. The initial model was used to develop the system, analyze operating parameters and provide initial performance results. The initial simulations indicate that the system requires two optimizations to meet the target performance: condenser pressure optimization and the use of multiple membrane segments operating at different pressures. The latent only COP including the optimizations was a maximum of 4.23. A second model was then developed which uses a more detailed mass transfer model and a more detailed condenser model based on the operating conditions. This simulation yielded a maximum latent only COP of 4.37 including the optimizations. The work also analyzes two different combined systems capable of providing both sensible and latent cooling. The first utilizes a conventional vapor compression cycle for sensible cooling and has a maximum COP of 3.93. The second uses multiple evaporative coolers in between multiple membrane dehumidification steps and was found to have a maximum COP of 3.73. Second law analysis of the systems was also conducted and found that the greatest reduction in latent system exergy loss can be obtained by improving the selectivity of the membrane. Apart from improving the membrane selectivity, the results show the greatest improvement can be found in improving the operation of the gas compression devices.

This thesis introduces a quasi-dynamic building simulation methodology which complements existing building simulators by allowing transient models of HVAC (heating, ventilating and air-conditioning) systems to be created in an analogous way to their design and simulated in a computationally efficient manner. The methodology represents a system as interconnected, object-oriented sub-models known as components. Fluids and their local properties are modeled using discrete, incompressible objects known as packets. System wide pressure and flow rates are modeled similar to electrical circuit models. Transferring packets between components emulates fluid flow, while the system wide fluid circuit formed by the components' interconnections determines system wide pressures and flow rates. A tool named PAQS, after the PAacketized Quasi-dynamic Simulation methodology, was built to demonstrate the described methodology. Validation tests of PAQS found that its steady state energy use predictions differed less than 3% from a comparable steady state model. PAQS was also able to correctly model the transient behavior of a dynamic linear analytical system.

The electrical power has been applied in many applications extensively since the industrial revolution and becomes the main energy source in the 21th century. Because of the fast economic growth, the electrical power demands have increased extensively in the past 30 years. In recent years, number of semiconductor factories have been built in Taiwan and bring the electrical power not enough in the summer. Because the climate is hot and humid in Taiwan, energy consumption of air conditioning is half of total consumption of the building, and the energy consumption of chiller plant is more than 30% of total consumption of HVAC system. Based on field measurement data, the air-conditioning system consumes more than 40% of the building total energy use, followed by 30% of lighting, and 30% of miscellaneous pumping systems.. Among them, 60% power was consumed by chiller plants, while the chilled water pumping and air side equipment each accounts for another 20%. It is no doubt, that the energy efficiency improvement of chillers is one of the most important items in building energy conservation. The capacity of HVAC system in many Taiwan¡¦s big buildings has the situation that the designed capacity is much larger than the actual required, and this Oversize Design of HVAC system caused waste of extra equipment and cost. In this content, we offer improvement methods that are predicated on the HVAC system waste situation, and provide the prediction of efficient. As most of HVAC system in existing building have Oversize Design problem, it caused HVAC engines are with low efficiency and loading, and energy wasting is getting worse and worse. Besides, some existing engines may keep running over 10 years; the performance is far behind the new type engine. According to the existingsystem¡¦s running status, we can have the precise HVAC¡¦s loading, and redesign the conformable HVAC¡¦s engine type to make it is under efficient operation; furthermore, in order to be energy-saving, we design the best proper sets based on loading capacity, and change to new type HVAC engine with high performance, also, we improve the design of water system.

It is the goal of this project to investigate the energy conservation measures which can be adapted in an electronic manufacturing plant HVAC system. Computer simulation has been proceeded using Power DOE as a tool in evaluating the power consumption of HVAC, lighting and auxiliary systems, validated by full-scale experimental field measurements so that optimal operation strategies can be established for energy savings. Experimental result indicated that the HAVC system consumes 34% of that of the whole plant with 19% consumed by chillers. Comparatively, the simulation result indicated that HVAC system consumes 36% of the total which confirms the potential for energy savings. It is concluded and recommended that the DHC , or District Heating and Cooling system can be adapted in this situation which coupled with the multiple-chiller controls with variable water volume (VWV) pumping for optimal operation through the direct digital controls.