Energy and Exergy Analysis of Data Center Economizer Systems

Electrical consumption for data centers is on the rise as more and more of them are being built. Data center owners and operators are looking for methods to reduce energy consumption and electrical costs. One method of reducing facility costs for a chilled water plant is by adding an economizer. Most studies concerning economizer systems are conducted largely by looking at energy alone since the primary focus is reducing electrical costs. Understanding how much exergy is destroyed, where it is destroyed, and why it is destroyed provides a more complete view on how environmental impacts can be minimized while reducing energy usage. The purpose of this study is to develop energy and exergy-based models of the most common economizer systems. A normal chiller plant without an economizer and a chiller plant with an indirect wet-side economizer (the most common type of economizer system) are compared. Results show outdoor conditions influence facility energy consumption and exergy destruction. For a chiller plant operating with an economizer, the CRAH is found to be the largest source for exergy destruction. For a chiller plant without an economizer, the chiller is the largest source for exergy destruction

Dynamic simulation of polygeneration systems for buildings

This thesis aims at investigating the polygeneration systems for buildings by dynamic simulation models. In particular, different polygeneration systems, supplied both by the solar renewable energy source and natural gas, were examined from the energy, exergy, economic and environmental point of view

PERFORMANCE EVALUATION OF LOW EXERGY SYSTEMS DEPICTING DECENTRALIZED DEDICATED OUTDOOR AIR SYSTEM COUPLED WITH RADIANT COOLING IN THE TROPICS

Ph.DDOCTOR OF PHILOSOPH

Process Efficiency Optimisation of Cascade LNG Process

The aimed of this thesis is to optimise the Cascade LNG process efficiency of 5 MTPA production capacity. The cascade process was modelled and simulated in Aspen HYSYS version 7.2 using Peng Robinson equation of state. The optimisation of cascade process was carried out from operation and design perspectives. It focused on two main cycles which are propane and ethylene refrigeration cycles as they are the main energy consumers of this process

Screening of energy efficient technologies for industrial buildings' retrofit

This chapter discusses screening of energy efficient technologies for industrial buildings' retrofit

Development and analysis of micro polygeneration systems and adsorption chillers

About a fifth of all primary energy in the US is consumed by residential buildings, mostly for cooling, heating and to provide electricity. Furthermore, retrofits are essential to reducing this consumption, since the buildings that exist today will comprise over half of those in use in 2050. Residential combined heat and power (or micro CHP, defined by <5 kW electrical generation capacity) has been identified as a retrofit technology which can reduce energy consumption in existing homes during the heating season by 5-30%. This thesis investigates the addition of a thermally-driven chiller/heat pump to a CHP system (to form a trigeneration system) to additionally provide savings during the cooling season, and enhance heating season savings. Scenarios are identified in which adding thermally-driven equipment to a micro CHP system reduces primary energy consumption, through analytical and experimental investigations. The experimental focus is on adsorption heat pump systems, which are capable of being used with the CHP engines (prime movers) that are already widely deployed. The analytical analysis identifies energy saving potential off-grid for today's prime movers, with potential on-grid for various fuel cell technologies. A novel dynamic test facility was developed to measure real-world residential trigeneration system performance using a prototype adsorption chiller. The chiller was designed and constructed for this thesis and was driven by waste heat from a commercially available natural gas-fueled 4 kW (electric) CHP engine. A control strategy for the chiller was developed, enabling a 5-day experiment to be run using a thermal load profile based on moderate Maryland summer air conditioning loads and typical single-family domestic hot water demand, with experimental results in agreement with models. In this summer mode, depending on electrical loads, the trigeneration system used up to 36% less fuel than off-grid separate generation and up to 29% less fuel than off-grid CHP without thermally driven cooling. However, compared to on-grid separate generation, the experimental facility used 16% more primary energy. Despite high chiller performance relative to its thermodynamic limit, this result is primarily due to the electrical efficiency of the prime mover being lower than the grid. A residential trigeneration system utilizing a high temperature fuel cell is predicted to save up to 42% primary energy relative to the grid

Energy analysis of a Micro-CHP demonstration facility

Cooling, Heating, and Power (CHP) systems have been around for decades, but systems that utilize 20 kW or less, designated as Micro-CHP, are relatively new. Micro-CHP systems show the most promise for a distributed generation scheme to decentralize the national energy grid. A demonstration site has been constructed at Mississippi State University to show the advantages of these systems. This study is designed to evaluate the performance of a Micro-CHP system and a conventional high-efficiency system. Performance and cost factors can be evaluated for the demonstration site operating under either the CHP system or the conventional system. These results are computed from an energy analysis on collected data. This dissertation introduces a new comparison factor to examine different CHP systems. This new factor is called the System Energy Transfer Ratio (SETR). Other considerations in this study include an extensive literature survey that reviews CHP systems, their components, modeling, and other topics concerning CHP systems operation. In addition, the demonstration facility will be discussed in detail presenting the various components and instrumentation. Furthermore, the energy analysis will be presented, examining the equations used to evaluate the raw data from the demonstration site. An uncertainty analysis will be presented for the experimental results. Raw data was collected for 7 months to present the following results. The combined cycle efficiency from the demonstration site was averaged at 29%. Maximum combined cycle efficiency was evaluated at 58%. The average combined boiler and engine cost, per hour of operation, is shown as $1.8 for heating and$3.9 for cooling. The cooling technology used, an absorption chiller, has been shown to exhibit an average COP of 0.27. The proposed SETR for the demonstration site is 22% and 15%, for heating and cooling, respectively. The conventional high-efficiency system, during cooling mode, was shown to have a COP of 4.7 with a combined cooling and building cost of $0.2/hour of operation. During heating mode, the conventional system had an efficiency of 47$0.28/hour of operation

Energy analysis of a Micro-CHP demonstration facility

Cooling, Heating, and Power (CHP) systems have been around for decades, but systems that utilize 20 kW or less, designated as Micro-CHP, are relatively new. Micro-CHP systems show the most promise for a distributed generation scheme to decentralize the national energy grid. A demonstration site has been constructed at Mississippi State University to show the advantages of these systems. This study is designed to evaluate the performance of a Micro-CHP system and a conventional high-efficiency system. Performance and cost factors can be evaluated for the demonstration site operating under either the CHP system or the conventional system. These results are computed from an energy analysis on collected data. This dissertation introduces a new comparison factor to examine different CHP systems. This new factor is called the System Energy Transfer Ratio (SETR). Other considerations in this study include an extensive literature survey that reviews CHP systems, their components, modeling, and other topics concerning CHP systems operation. In addition, the demonstration facility will be discussed in detail presenting the various components and instrumentation. Furthermore, the energy analysis will be presented, examining the equations used to evaluate the raw data from the demonstration site. An uncertainty analysis will be presented for the experimental results. Raw data was collected for 7 months to present the following results. The combined cycle efficiency from the demonstration site was averaged at 29%. Maximum combined cycle efficiency was evaluated at 58%. The average combined boiler and engine cost, per hour of operation, is shown as $1.8 for heating and$3.9 for cooling. The cooling technology used, an absorption chiller, has been shown to exhibit an average COP of 0.27. The proposed SETR for the demonstration site is 22% and 15%, for heating and cooling, respectively. The conventional high-efficiency system, during cooling mode, was shown to have a COP of 4.7 with a combined cooling and building cost of $0.2/hour of operation. During heating mode, the conventional system had an efficiency of 47$0.28/hour of operation