School of Engineering (SoE)

Permanent URI for this community

https://dspace.lib.cranfield.ac.uk/handle/1826/16

Browse

Browsing School of Engineering (SoE) by Supervisor "Badr, Ossama"

Now showing 1 - 5 of 5
  • Thumbnail Image
    ItemOpen Access
    Development of a cascaded latent heat storage system for parabolic trough solar thermal power generation
    (Cranfield University, 2014-09) Muhammad, Mubarak Danladi; Badr, Ossama; Yeung, Hoi
    Concentrated solar power (CSP) has the potential of fulfilling the world’s electricity needs. Parabolic-trough system using synthetic oil as the HTF with operating temperature between 300 and 400o C, is the most matured CSP technology. A thermal storage system is required for the stable and cost effective operation of CSP plants. The current storage technology is the indirect two-tank system which is expensive and has high energy consumption due to the need to prevent the storage material from freezing. Latent heat storage (LHS) systems offer higher storage density translating into smaller storage size and higher performance but suitable phase change materials (PCMs) have low thermal conductivity, thus hindering the realization of their potential. The low thermal conductivity can be solved by heat transfer enhancement in the PCM. There is also lack of suitable commercially-available PCMs to cover the operating temperature range. In this study, a hybrid cascaded storage system (HCSS) consisting of a cascaded finned LHS and a high temperature sensible or concrete tube register (CTR) stages was proposed and analysed via modelling and simulation. Fluent CFD code and the Dymola simulation environment were employed. A validated CFD phase change model was used in determining the heat transfer characteristics during charging and discharging of a finned and unfinned LHS shell-and-tube storage element. The effects of various fin configurations were investigated and heat transfer coefficients that can be used for predicting the performance of the system were obtained. A model of the HCSS was then developed in the Dymola simulation environment. Simulations were conducted considering the required boundary conditions of the system to develop the best design of a system having a capacity of 875 MWhth, equivalent to 6 hours of full load operation of a 50 MWe power plant. The cascaded finned LHS section provided ~46% of the entire HCSS capacity. The HCSS and cascaded finned LHS section have volumetric specific capacities 9.3% and 54% greater than that of the two-tank system, respectively. It has been estimated that the capital cost of the system is ~12% greater than that of the two-tank system. Considering that the passive HCSS has lower operational and maintenance costs it will be more cost effective than the twotank system considering the life cycle of the system. There is no requirement of keeping the storage material above its melting temperature always. The HCSS has also the potential of even lower capital cost at higher capacities (>6 hours of full load operation).
  • Thumbnail Image
    ItemOpen Access
    Development of a Hybrid Powerplant for Kuwait: The Simultaneous Production of Power, Fresh Water and Cooling
    (Cranfield University, 2010-03) Hussain, Hussain J.; Badr, Ossama
    The harsh summer months of Kuwait combined with massive urbanisation projects, population growth and generous subsidies resulted in a rapid increase in electricity and freshwater consumption over the past 30 years. This led the government to invest heavily in large and capital intensive cogeneration powerplants that generate electricity via steam turbines and produce desalinated seawater through the utilisation of the multi-stage flash (MSF) desalination process. Air-conditioning (A/C) load accounts for about 70% of electric peak-load during summer. As a result, Kuwait consumes annually millions of barrels of oil and tons of natural gas that can be otherwise exported or saved for the future as a strategic commodity. The main objective of this research is to develop, model and recommend an optimum hybrid powerplant configuration and operation strategy for Kuwait that can simultaneously satisfy the demand for electricity, freshwater and cooling based on minimum fuel consumption. This is achieved by modelling and simulation of steam Rankine cycle, MSF water desalination and absorption refrigeration systems (ARSs) in Matlab to estimate their steam consumption. Reverse osmosis (RO) desalination and vapour-compression A/C are linked to the hybrid simulation program via their electricity consumption. Simulations show that during the hybrid configuration power-RO-AR is the most viable for Kuwait. During the winter months of January, February and December the optimum operation strategy with minimum fuel cost is the power-RO. On the other hand, operating the powerplant in the power-RO-AR hybrid mode during summer results in minimum fuel cost. The total annual fuel cost savings resulting from modifying the Doha West (DW) powerplant configuration and operation strategy are estimated to be about $363 million. This amounts to savings of about 8 million barrels of oil and 114 million m3 of natural gas per year. Furthermore, the payback period of hybridising the DW powerplant by adding RO desalination and AR system is one year with net savings of $127 million in the second year of operation.
  • Thumbnail Image
    ItemOpen Access
    Heat transfer characteristics of heat pipe heat exchangers for low and medium temperature heat recovery
    (1997-07) Kang, Heeyoon; Badr, Ossama
    Heat pipe heat exchangers (HPHEs) offer many advantages over other types of heat exchangers for the recovery of heat from industrial gaseous waste streams in the low and medium temperature ranges. Heat pipes employed in industrial heat exchangers can be made with or without wicks. Although the thermal performances of single heat pipes and HPHEs have been extensively investigated, comparative studies concerning behaviours of HPHE with different types of heat pipes, at the same operating conditions, appear to be very limited. Such studies are useful in evaluating the significance of the parameters pertinent to thermal performance and in selecting the most appropriate HPHE for a particular application. Taking into account previous studies, the present work was focused on comparative studies between heat pipe and thermosyphon, at the same operating conditions, with following the objectives : • Further studying the heat transfer characteristics of heat pipe and thermosyphon to obtain additional information regarding thermal performance, at the same operating conditions. • Providing some guide-lines for HPHEs design which relate to the thermal performance of heat pipe and thermosyphon. To achieve these objectives, two computer models, a ‘Heat Pipe and Thermosyphon Thermal Performance Model’ and a ‘Heat Pipe Heat Exchangers Design Model’, were developed. The former model facilitates the prediction of the axial temperature distributions of the working fluid and the tube wall ; heat transport limitations; and the thermal performances of thermosyphons and heat pipes with different type of wicks. An experimental investigation of the steady-state behaviour of the thermosyphon was carried out to validate this computer model and the results were compared with the corresponding predictions of the computer model developed. According to the experimental results, Nusselt’s film theory for continuous liquid film could not be employed for predicting thermal performances in the condenser and evaporator film region of inclined thermosyphons. Liquid film could only be maintained circumferentially in vertical thermosyphon tubes, even though might not the smooth continuous film. In the evaporator pool region, the change in saturation temperature due to the hydrostatic height of the pool should be considered for predicting the axial temperature distributions. The results of the behaviours of heat pipes and thermosyphons were utilised to develop a ‘Heat Pipe Heat Exchangers Design Model’ to facilitate both the design and the prediction of performances of HPHEs. These models enable the designers of waste-heat recovery systems to choose the most appropriate type of heat-transfer elements and optimise the design parameters of a HPHE for a given application.
  • Thumbnail Image
    ItemOpen Access
    A Model for sustainable biomass electricity generation in Bangladesh
    (Cranfield University, 2005-09) Hossain, A. K. M. S.; Badr, Ossama
    Bangladesh, where only 20% of the total population are connected to grid electricity, has a promising scope to utilise biomass for decentralised electricity generation. In this study, sustainable biomass electricity generation model was developed for the country, by combining tech no-econometric and optimisation modelling techniques. The developed model addresses the biomass generation and availability, feasible technologies, cost and efficiency correlations, economic plant size, plant economics and sensitivity, and environmental and social impacts. In 2003, the national total annual available biomass energy potential in Bangladesh varies from 183.848 to 223.776 TWh. The feasible technologies are: gasification based ICE-generator, anaerobic digestion based ICE-generator and direct combustion based steam turbine or Stirling engine-generator. Correlations of capital investment costs and overall conversion efficiencies with the plant electricity generating capacity have been developed. Direct combustion technology shows the highest electricity generation potential of 20.21 TWh/year; followed by gasification, of 14.30 TWh/year. Economic radius of biomass collection and size of the plants has been determined for maximum profitability. The biomass electricity plants economics have been estimated and compared with the diesel and dual-fuelled plants. Analysis shows that, anaerobic digestion and gasification-based electricity generation plants are economically feasible. Biomass electricity plant is highly sensitive to changes in biomass price, selling price of electricity, investment cost, plant lifetime, conversion efficiency and operating hours. The employment of the biomass electricity instead of diesel generator saves significant amount of the greenhouse gas emissions. It creates more employment than conventional and presents other socio-economic benefits as well. Due to the combination of electricity generation potential, promising economics and low greenhouse gas emissions; gasification-based biomass electricity plant is recommended for the country. Biomass availability and plant economics vary between districts to districts. Computer programmes have been developed for district wise biomass electricity plant analysis.
  • Thumbnail Image
    ItemOpen Access
    A national energy policy proposal for Trinidad and Tobago: natural-gas cogeneration
    (2002-01) Hosein, Sharaaz; Badr, Ossama
    This thesis looks at energy policy in Trinidad and Tobago (T&T) by focusing on a single policy measure, natural-gas cogeneration, to learn about energy policy in general. It investigates natural gas as it is in the ascendancy, both locally and globally, and because oil is on the decline in T&T. The research further focuses on cogeneration in the industrial sector. It then approximately extrapolates results from the industrial sector to the entire country. The aim can thus be described as assessing natural-gas cogeneration's potential as a policy measure, using the industrial sector as an example. LNG, another major natural-gas use, provides a reference point for locating natural-gas cogeneration in the overall energy policy framework. The industry-wide cogeneration evaluation groups the 1,967 industrial electricity customers in 1998 according to similarity in electricity-use characteristics into 15 subgroups. This allows a study of one or more representatives from each subgroup to apply to the whole subgroup, and thus covers the whole spectrum of industrial electricity customers. This is a fundamental assumption of the research. The research thus essentially becomes a series of cogeneration feasibility studies at individual sites, needing data gathered from extensive fieldwork, and an analysis model constructed in MS Excel, which applies a standard business project-appraisal procedure. The analysis determines that industrial cogeneration in 1998 delivers conservative natural-gas savings of 2.2 billion kWh, or 13.5% of the natural gas used to generate the entire country's electricity in that year. The dollar value of these savings over 20 years is US$0.2 billion, using LNG's natural-gas resource valuation. Considering that a single LNG train uses 48.1 billion kWh natural gas per annum and delivers US$6 billion in revenues over 20 years, cogeneration is a minor policy measure compared to the petrochemical industry, and similarly in an overall natural-gas policy. However, cogeneration's significance to the electricity sector, and its importance in promoting a nationwide natural-gas infrastructure for the future, where the population directly benefits from the resource, renders it an important energy-policy measure.