Scheduling of Multiple Chillers in Trigeneration Plants

The scheduling of both absorption cycle and vapour compression cycle chillers in trigeneration plants is investigated in this work. Many trigeneration plants use absorption cycle chillers only but there are potential performance advantages to be gained by using a combination of absorption and compression chillers especially in situations where the building electrical demand to be met by the combined heat and power (CHP) plant is variable. Simulation models of both types of chillers are developed together with a simple model of a variable-capacity CHP engine developed by curve-fitting to supplier’s data. The models are linked to form an optimisation problem in which the contribution of both chiller types is determined at a maximum value of operating cost (or carbon emission) saving. Results show that an optimum operating condition arises at moderately high air conditioning demands and moderately low power demand when the air conditioning demand is shared between both chillers, all recovered heat is utilised, and the contribution arising from the compression chiller results in an increase in CHP power generation and, hence, engine efficiency

Construction of prototype system for directional solvent extraction desalination

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 37-38).Directional solvent extraction has been demonstrated as a low temperature, membrane free desalination process. This method dissolves the water into an inexpensive, benign directional solvent, rejects the contaminants, then recovers pure water, and re-uses the solvent. In order to bring this technology closer to real world application, a continuous process prototype for a directional solvent extraction system was developed and tested. Octanoic acid was used as the solvent of choice, and a system capable of producing up to 7 gallons per day of fresh water was constructed. The system was tested to effectively desalinate the feed water, and the total system power was less than 7 kW. The system was constructed and first tested to run fresh water and solvent through it. Fresh water was dissolved in and separated, as expected, from the solvent at a rate of about 2 gpd. Saline water containing 3.5% sodium chloride was then used as feedwater and the desalinated water was recovered at a rate of about 1 gpd with an average salinity of 0.175%. Effective continuous operation of the directional solvent extraction prototype was demonstrated. Certain design improvements to increase efficiency, optimize component sizes, and decrease energy consumption are suggested. The demonstrated system has a wide range of applications, including production of fresh water from the sea, as well as, treatment of produced and flowback water from shale gas and oil extraction.by Michael James Fowler.S.B

Assessing site performance of large mine water chilling machines using refrigerant-circuit measurements and machine modelling

A thesis submitted to the Faculty of Engineering, University of the Witwatersrand, Johat.nesburq, in fulfilment of the requirements for the degree of Doctor of Philosophy Johannesburg, 1998This thesis contributes to accurate, practicable techniques of ascertaining and assessing site performance of large refrigerating machines chilling water 'for cooling deep South African mines. It applies to all vapourcompression machines cooling fluids in steady, continuous processes. To assess whether a water chilling machine is performing satisfactorily, both its actual performance, and the corresponding normal or optimal performance of which it is capable, must be ascertained. Both requirements r esent difficulties on site. in particular, the traditional "heat balance" method of verifying the apparent performance obtained from measurements in the water circuits does not prove that such performance is accurate. The calibration of typical site instrumentation is not assured, so an "acceptable" heat imbalance may conceal large but similar errors - which thus also balance out - in the apparent constituents of the heat balance. Three methods of independently ascertaining actual performance, so verifying apparent performance, are presented, The first is an enhanced method, applicable to custom-built machines as well as conventional ones, of ascertaining the efficiency of the actual refrigerating process from measurements in the refrigerant circuit. This detects errors concealed in an "acceptable" heat balance. Where some refrigerant-circuit measurements are unavailable, an inexact version of this method still indicates the relative likelihood of the apparent performance being acceptably accurate. The third method, where these two are inadequate, is ascertaining actual performance using available measurements and fundamental machine modelling. Such modelling is also the most versatile method of predicting corresponding normal or optimal performance. A computer program simulating complete mine water chilling installations is used here. Actual performance can then be meaningfully assessed and appropriate remedial action justified, as shown in seven case studies. An outcorr.e for conventional water chillinq machines with a centrifugal compressor is that keeping heat exchangers clean may prejudice efficiency under part-duties lf a machine has been designed for optimum efficiency at full duty. An alternative control philosophy of maximising the machine load may then yield better performance. If these techniques are included ill an automated system of fault diagnosis, they will be of most use to burdened mine staff, who are generally not refrigeration experts

EFFECT OF ADAPTIVE COOLING TECHNIQUE ON ENERGY USAGE PATTERNS OF A CENTRALIZED HVAC SYSTEM

Nowadays, due to world energy crisis and global warming, efforts to reduce energy consumption become doubled. One of the efforts is to find strategies for lower energy consumption by the centralized HVAC system since the system is a major energy consumer in many building. Field studies conducted by many researchers in many countries have found that adaptive comfort temperature (ACT) for naturally ventilated and air-conditioned building are higher than the recommended value. Previous works on this topic showed that using the ACT, around 20% of energy consumed by HVAC system could be saved without sacrificing people’s comfort. However, mechanical limitation of HVAC system, the effects of application of the indoor comfort temperatures on the HVAC system and its applicability for academic building has not been discussed in detail on previous research. Therefore, this work aims to develop adaptive cooling technique using ACT to reduce energy consumption of a centralized HVAC system in an academic building by taking into account design limitation, and effect of application of ACT on the HVAC system. The building model and its HVAC system were first built using a building simulation program (BPS), TRNSYS and validated by comparing the simulation results with experimental results. Adaptive cooling technique coupled with dual fan dual duct system was built as proposed technique for effective, efficient, and economical solution to reduce the energy consumption. The validated model was then used to analyze the performance of the HVAC system using current strategies and proposed technique. In case of academic bloc 16 in Universiti Teknologi PETRONAS, the results showed that the indoor comfort temperatures ranges during occupied and unoccupied periods were 24.29oC – 24.51oC and 28.04oC – 28.76oC, respectively, while the relative humidity was constant at 70%. The proposed technique is able to reduce the cooling load up to 28.54% and has payback period less than 5 years

Short-term advancements and long-term visions for sustainability at the Radisson-Slavyanskaya Hotel

The global hotel industry has become increasingly aware of its environmental impact. This report examines the practices of the Radisson-Slavyanskaya Hotel in Moscow, Russia with respect to environmental sustainability. Energy audit data, guest input, discussions with hotel management, renovation challenges, and financial calculations led us to three specific short-term recommendations and multiple long-term suggestions aimed at reducing the energy use of the hotel. The technical and financial feasibility of potential upgrades was gauged in order to provide the most practical solutions for the hotel. We focused on the central AC system, window films, and room occupancy sensors, each of which result in significant water, electricity, and steam savings for the Radisson-Slavyanskaya Hotel

Optimizing operation of a campus energy system for economic and environmental considerations

The objective of this thesis is to determine effective costs of campus utilities, optimal operation of energy conversion and production subsystems through minimization of economic and environmental costs, and to evaluate how changing electrical grid costs and sources will affect future optimal operations at a campus. Characteristic days were developed to typify campus activities and their impact on energy consumption. At current grid electricity and natural gas prices, utilization of a cogeneration unit, a form of combined heat and power plant, is less expensive than purchasing equivalent amounts of electric and gas to produce steam, as long as there is sufficient campus demand for the electricity and steam produced. Carbon dioxide emissions during cogeneration unit operation was nearly the same as purchasing equivalent amounts of electric and gas to produce steam. Simulation of economic and environmental performance of the cogeneration plant, found minor differences between least expensive and greenest operations. Analyses suggested that grid emissions will not become clean enough to merit decommissioning of cogeneration plant early. Operation of the cogeneration plant is favorable for economical and environmental considerations

Cellular Agriculture

Cellular agriculture is a field of biotechnology focused on the production of animal products using cells grown in vitro . Traditional meat production consumes vast amounts of water, arable land, and feed crops, as well as driving deforestation, emitting large amounts of greenhouse gases, and creating large potential reservoirs for zoonotic diseases. As the global demand for meat increases, continuing to scale up the industry for slaughtered meat could have disastrous consequences for the environment. Growing cells in bioreactors creates the potential to drastically decrease land requirements, feed requirements, and other environmental impacts. For example, hindgut fermentation of feed, the main source of methane emissions from cattle farming, can be eliminated entirely by supplying the cells with pure glucose. This report proposes a process to produce 35 million pounds per year of a cultured ground beef product. The process starts with a starter colony of bovine muscle satellite cells, which are proliferated, differentiated to bovine muscle fiber, and then dewetted, mixed with plant-based fat, and extruded to the final product. Bubble column bioreactors are used for the seed train, final proliferation, and differentiation steps in order to adequately oxygenate large process volumes without threatening cell viability. The process shows profitability at a price of $100 per pound of product. The plant has a return on investment of 217$2 billion over the plant’s lifespan

Screening of energy efficient technologies for industrial buildings' retrofit

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