Screening of energy efficient technologies for industrial buildings' retrofit

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

Self-Regulating Active Chilled Beams

By designing comfort cooling systems to operate with higher chilled water temperatures, electricity driven chillers may be replaced by natural sources of free cooling. It also enables the possibility of self-regulation which, due to simplicity and robustness, brings cost-savings both during installation and maintenance of the building. Active chilled beams is one technology especially well suited for this high temperature cooling. The objective of this thesis is to investigate the function of self-regulating active chilled beams in order to improve design and operation of such systems. Based on experience from existing systems, a hypothesis is that current models and knowledge do not fully capture the behavior of self-regulating active chilled beams.The work has been carried out through measurements in an experimental facility, building performance simulations and analysis of operational data from an actual building. The purpose of the measurements was to develop a model of an active chilled beam and also to validate a modified zone model used to simulate the thermal climate in a room equipped with an active chilled beam. The purpose of the simulations was to determine the peak shaving effect of self-regulating active chilled beams and to study the influence of central control of the chilled water temperature. The purpose of the analysis of operational data was to study the performance of an actual self-regulating active chilled beam system with respect to energy use and indoor air temperatures. The results show that a higher chilled water temperature generates more induction of room air in the active chilled beam, which is beneficial for the cooling capacity. Induction of room air also increases the internal convective heat transfer in the room, which reduces the required heat transfer area of the active chilled beam. As a consequence of self-regulation, buildings are precooled prior to the peak cooling load, further reducing the required heat transfer area. By increasing the chilled water temperature outside of the summer season, overcooling is avoided without causing thermal discomfort. The analysis of operational data demonstrates the ability to achieve the desired indoor temperatures with self-regulating active chilled beams without the use of a chiller

Direct Ground Cooling Systems for Office Buildings

The solving of crucial global energy challenges hinges on improving energy efficiency in building energy systems. Accomplishing energy-efficiency targets often entails incorporating sustainable energy sources into the energy supply system. Direct ground cooling systems (DGCSs) are among the most sustainable technologies for comfort cooling in office buildings. With this technology, cooling is provided by the circulation of the working fluid through the ground heat exchangers. This technology is mostly used in cold climates where the underground temperature is low, and the building cooling loads are low enough to be offset by the ground cooling. Using only a modest amount of electricity to drive the circulation pumps, this technology is incredibly energy efficient. However, designing DGCSs presents some unique challenges, and only a handful of studies on this subject are available.This work aims to develop knowledge about comfort cooling for office buildings using DGCSs and expand upon design and operation practices for this technology. The findings presented in this work are based on experimental and simulation results. The experimental results build upon existing knowledge for operating cooling systems and substantiate new operation methods for the DGCSs. The experimental results are also used to develop and validate simulations. The simulation results facilitate investigating the short- and long-term thermal and energy performance of the DGCSs for various design circumstances.The borehole system design is usually performed independently from the building energy system design. In view of this work’s findings, considering the whole system (borehole, control system, terminal units) can enhance the design. A sub-system’s input design requirements can be aligned with the corresponding output of other sub-systems in a comprehensive design approach. This work demonstrates and quantifies that terminal units with slow response, such as thermally active building systems (TABS), can smooth out the daily peak heat rejection loads to the ground, resulting in shorter boreholes. Thus, the ground system can be much smaller than required for fast-response terminal units, such as active chilled beams. This work analyses different operation practices for DGCSs. The results suggest that allowing the room temperature to rise somewhat during the “on-peak” cooling loads can reduce the ground heat rejection loads, for which shorter boreholes can be designed. If combined with precooling the space during the “off-peak” cooling loads, a further reduction in the ground loads is yielded.This work also investigates the design and application of the DGCSs in existing office buildings. A systematic approach is provided to evaluate the influence of common renovation parameters on the design and energy performance of a DGCS. The systematic approach includes a step-by-step methodology to explain how sensitive the subsequent system design might be to the variations in the renovation parameters. Furthermore, the results quantify the potential electricity savings by using the DGCS instead of a chiller

Viking '75 spacecraft design and test summary. Volume 1: Lander design

The Viking Mars program is summarized. The design of the Viking lander spacecraft is described

Aeronautical Engineering: A continuing bibliography, supplement 120

This bibliography contains abstracts for 297 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1980

Modeling and Control of Passive Chilled Beams with Underfloor Air Distribution of Ventilation in Office Buildings in Humid Climates

This dissertation presents the results of a study to determine the operational control, energy performance and comfort conditions associated with passive chilled beams for office buildings in a humid climate and to develop a method for the modeling of passive chilled beams with a ventilation system and underfloor air distribution (UFAD). For the analysis, a 606,900 ft2 commercial office building in ASHRAE climate zone 3A with passive chilled beams and a ventilation system with UFAD was selected as the case-study building. In the first step, measured data from the building was used to develop a calibrated whole-building energy analysis model in EnergyPlus 8.1. The energy model also implemented methods to model the controls found in a passive chilled beam system with underfloor air distribution. A simplified steady-state energy model was also developed for the validation of the EnergyPlus model and for energy use prediction. In the second step, two methods of optimization for the operational control strategies were tested: a simplified rule-based optimization and a model-based predictive control optimization. The influence of these two approaches to optimization on HVAC energy savings and thermal comfort were found to be within 2% of each other. Finally, summertime stratification measurements were taken in the offices and were combined with a CFD model of a single zone in Star CCM+ 9.04 to establish temperature and airflow profiles in the zones. These comfort studies were conducted for the cooling season only and showed that the thermostat setpoints are not fulfilled in the exterior zones in summer and chilled beam and ventilation system interact with each other and have an adverse effect on the overall system energy efficiency. The results of the research show that if properly controlled, a passive chilled beam system with a parallel ventilation system has the potential for HVAC savings of 14-24% over standard VAV systems in office buildings in humid climates. All of the HVAC energy savings come from fan and reheat energy. Energy savings are affected by latent loads and ventilation requirements in the zones and the potential for the use of an economizer. Indoor humidity levels are also higher with a passive chilled beam system than a standard VAV system. Independent control of the volume of air supplied by the ventilation system and the supply air temperature is necessary to achieve the predicted energy savings. Lastly, the summertime zone comfort studies reveal that the presence of the UFAD ventilation system hinders the natural downward plumes from the chilled beams and the presence of the chilled beam system inhibits stratification in the zones. Because of the lower ventilation flow rates associated with the chilled beams, there is significant increase in the temperatures in the supply plenums

Direct-Ground Cooling Systems for Office Buildings: Design and Control Considerations

Direct-ground cooling systems are defined as systems in which the ground is used as the only source for cooling mainly in commercial buildings. These systems benefit from exchanging heat with the ground, of which its temperature is basically constant below a certain depth year around. Since electricity demand of these systems is only about driving the circulation pumps, the direct-ground cooling systems are among the most environmentally sustainable and energy efficient systems available for cooling buildings.This thesis is undertaken with a two-fold aim: presenting the design parameters of the ground-coupled systems, and evaluating the methods for controlling the cooling capacity of the direct-ground cooling systems. A comprehensive literature review has been performed on three main design parameters for the ground cooling systems, including ground thermal properties, borehole thermal resistance and building thermal load. All these parameters have been investigated regarding their influence on the energy demand of the system. The literature survey has been further extended to the terminal units operating with high-temperature chilled water, as they are suitable indoor heat terminal units for the direct-ground cooling application. The most common high temperature cooling terminal units have been studied regarding their working temperature levels and cooling capacities.Control methods for direct-ground cooling systems is the second major aspect studied in the present work. Two control methods, supply temperature control method and flow rate control method, have been applied to a ground-coupled ceiling cooling panel system and a fan-coil unit in laboratory settings. The experiments have been conducted in an office-scaled test room under different thermal indoor climates and heat gains. The results have shown that the design of the control system shall be done in relation to the flow rate limits in the building and ground loops, and the temperature levels of the ground. A high flow rate in the ground loop or in the building loop will not enhance the cooling capacity of the terminal units, but only caused increase in the energy use of the circulation pump. On the other hand, too low flow rate in the building loop increases the condensation risk on the pipes. This is because the supply water temperature in the building loop became closer to the ground temperature which is below the dew point of the space

Multi-objective optimization of the refrigerant-direct convective-radiant cooling system considering the thermal and economic performances

The refrigerant-direct convective-radiant cooling (RCC) system is attracting widespread concern due to its advantages of good thermal comfort, high energy efficiency and simple structure. However, researches on thermal and economic optimization of this system are rare. In this study, a novel heuristic approach is proposed to optimize the aluminum column-wing type refrigerant-direct convective-radiant cooling (ACT-RCC) system, which adopts artificial neural network (ANN) integrated with multi-objective genetic algorithm (MOGA). The numerical and economic models of the ACT-RCC terminal are developed and the numerical model is validated by the experimental data. Besides, the ANN model is adopted to accelerate the prediction of the thermal and economic performances of this system. Results show that the training values of the ANN model are fitted well with simulated results and the ANN model can greatly improve the runtime in comparison with original numerical and economic models. Based on the heuristic optimization approach, the optimal structure of the ACT-RCC terminal is the copper pipe diameter with 8.7 mm, copper pipe spacing with 25.5 mm and rib height with 30.3 mm. Compared with original structure, the cooling capacity of the improved ACT-RCC system is enhanced by 16.0% and the initial cost is reduced by 10.0%. The appearance area equals to the direct product of the length and width, and results show that the appearance area of the improved ACT-RCC terminal is decreased from 1.04 m2 to 0.78 m2. Therefore, the proposed heuristic approach provides guidance for improving the thermal and economic performances of the RCC systems

Closed cycle electric discharge laser design investigation

Closed cycle CO2 and CO electric discharge lasers were studied. An analytical investigation assessed scale-up parameters and design features for CO2, closed cycle, continuous wave, unstable resonator, electric discharge lasing systems operating in space and airborne environments. A space based CO system was also examined. The program objectives were the conceptual designs of six CO2 systems and one CO system. Three airborne CO2 designs, with one, five, and ten megawatt outputs, were produced. These designs were based upon five minute run times. Three space based CO2 designs, with the same output levels, were also produced, but based upon one year run times. In addition, a conceptual design for a one megawatt space based CO laser system was also produced. These designs include the flow loop, compressor, and heat exchanger, as well as the laser cavity itself. The designs resulted in a laser loop weight for the space based five megawatt system that is within the space shuttle capacity. For the one megawatt systems, the estimated weight of the entire system including laser loop, solar power generator, and heat radiator is less than the shuttle capacity

Gothenburg District Cooling System - An evaluation of the system performance based on operational data

The global energy demand for providing cooling in buildings is expected to increase the next decades, along with a rapid growth in the number of air conditioners and chillers. A more energy efficient, economical and environmentally viable solution to this increased cooling demand, is district cooling. In Sweden, this technology has been developed since the mid-1990’s and currently delivers about 1 TWh of cooling annually, to 40 cities.Common issues with district cooling are mainly related to the temperatures. First, a low temperature difference between the supply and return water, called low delta-T, persist despite extensive efforts by previous research to provide solutions. Second, low conventional supply and return temperatures remain, potentially as a result of limited knowledge about the temperatures used in the connected buildings. Previous research on the low delta-T has primarily focused on district cooling systems without heat exchangers separating the connected buildings from the distribution system.The purpose of this thesis is therefore to investigate issues with low delta-T in a district cooling system with heat exchanger separation and exploring the potentials of using higher temperatures, by increasing the knowledge about the connected buildings. The investigation is based on analyses of operational data from both primary and secondary sides of the heat exchangers in 37 of the connected buildings in Gothenburg district cooling system. This system is designed for a delta-T of 10 \ub0C and chilled water supply temperatures of 8 \ub0C in the connected buildings.The delta-T in Gothenburg district cooling system varies between 6-8 \ub0C and the results showed that the main causes to this low delta-T are the following: a low temperature approach between the supply streams of the heat exchanger; operation in the saturation zone on the primary side of the heat exchanger; and low return temperatures from cooling coils and fan coil units in connected building chilled water systems. The results also demonstrated that 75% of the recorded chilled water supply temperatures are higher than 8 \ub0C, when the outdoor temperature was 28 \ub0C. If high temperature district cooling was used, more than 50% of the annual district cooling generation would be supplied by free cooling from the river