Browsing by Author "Twaha, Ssennoga"

Now showing 1 - 6 of 6
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    Analysis of renewable energy feed-in tariffs in selected regions of the globe: Lessons for Saudi Arabia
    (Renewable and sustainable energy reviews, 2015) Ramli, Makbul A.M.; Twaha, Ssennoga
    In this paper,an analysis of renewable energy feed-in tariffs (REFIT) for the selected regions of the globe is done with the aim of drawing lesson for Saudi Arabia .A brief background and status of renewable energy sources(RES) utilization in Saudi Arabia is given at the beginning of this paper, followed by a review of the feed-in tariff(FIT) design models reported in literature. The application of the policy in Europe, the United States, Australia, Asia and Africa is then reviewed. Some observations from the analysis oft he FIT application in different countries have been discussed and finally,lessons have been drawn from the study. Some policy recommendations have been given for Saudi Arabia. The analysis of the lessons identified shows that the application of FIT scheme in Saudi Arabia is likely to speed up the development of renewable energy resources within the area.
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    Analysis of the cost of reliable electricity: A new method for analyzing grid connected solar, diesel and hybrid distributed electricity systems considering an unreliable electric grid, with examples in Uganda
    (Energy, 2014) Murphy, Patrick Mark; Twaha, Ssennoga; Murphy, Inês S.
    More than 1.3 billion people lack access to grid electricity. Uganda provides a typical example of an under-electrified country, with less than 12% of Ugandans having access. To address the lack of electricity access, there has been much analysis devoted to grid-connected distributed generation. What these analyses lack is a consideration that even where grid electricity reaches people, it is not always reliable; customers often experience hundreds of outage hours per month. This paper addresses this analytical shortfall to provide new methods to analyze reliable electricity and identify optimal systems to provide more reliable electricity. We adapt the HOMER (Hybrid Optimization Model for Electric Renewables) in this work to address unreliable electricity from the grid, and develop a method for determining optimal system configurations and predicting electricity costs for reliable power generation in regions with unreliable grid electricity. We demonstrate the method for a village in Uganda, but the method holds universally. Results indicate that diesel is the most economical choice, but slight increases in diesel and decreases in PV (photovoltaics) prices make solar/diesel hybrid systems competitive. Improved reliability increases cost, but the increase of can be justified for users needing more reliability.
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    A Comprehensive Review on 2D and 3D Models of Vertical Ground Heat Exchangers
    (Renewable and sustainable energy reviews, 2018) Cui, Yuanlong; Zhu, Jie; Twaha, Ssennoga; Riffat, Saffa
    The ground source heat pumps (GSHPs) have been extensively applied to commercial and residential buildings owing to their high-energy efficiencies and low running costs. The key component of the GSHP is a ground heat exchanger (GHE). The state-of-the-art two-dimensional (2D) and three-dimensional (3D) heat transfer models for borehole heat exchanger (BHE) and energy pile (EP) systems are reviewed in this paper. The physical procedures of heat transfer and the derivation of energy conservation within different channels of BHE (e.g., U-, W-, helical-shaped or coaxial-shaped) are summarized, in addition to the primary merits and demerits of each model. The main influencing factors on 2D and 3D model solutions including axial heat transfer, friction heat, spacing shack, thermal resistance, thermal short-circuiting between the inlet-pipe and outlet-pipe, are analysed and compared. Furthermore, various applications of these 2D and 3D models are elaborated. Finally, the recommendations, standpoints and potential future research on BHE heat transfer model are highlighted. It is believed that the work presented will contribute to the record of information and experiences necessary to develop BHEs for GSHP systems.
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    Comprehensive Study on a Novel Concentric Cylindrical Thermoelectric Power Generation System
    (Applied Thermal Engineering, 2017) Huang, Kuo; Li, Bo; Yan, Yuying; Li, Yong; Twaha, Ssennoga; Zhu, Jie
    This paper presents the novel designs of a concentric cylindrical thermoelectric generator (CCTEG) and an annular thermoelectric module (ATEM). The simulations are carried out to compare the performance of ATEM and the conventional square-shaped thermoelectric module (STEM). The heat pipe technology is introduced into the heat sink system in order to enhance the heat transfer in the radial direction of exhaust gas flow. A new index termed as the heat transfer filling factor 𝑓 has been introduced which quantities the level of space utilisation for thermoelectric modules (TEMs). The correlation between the coolant flow rate and TEM performance is also carried out. Experimental work is also carried out to demonstrate the viability of using the heat pipes for heat transfer enhancement as well proving the viability of the design. The simulations indicate that the open circuit electric potential of the ATEM is 17% more than that of the STEM. The experimental results show that the CCTEG system performs well under various conditions. This results also demonstrate that the concept of adding heat pipes to the heat sink system is a practical solution to achieve higher thermoelectric generator (TEG) performance while maintaining the compactness of the TEG system. A heat transfer filling factor of 0.655 is achieved for the CCTEG system which is higher compared to the existing TEG systems. Moreover, a higher coolant flow rate contributes to obtaining a better performance of the TEG system. It is important to note that the introduced index can give guidance for further optimisation design of TEG systems.
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    Power conditioning of thermoelectric generated power using dc-dc converters: A case study of a boost converter
    (University of Nottingham, 1930) Twaha, Ssennoga; Zhu, Jie; Yan, Yuying
    The near exhaustion of non renewable energy resources such as fossil fuels followed by disastrous climatic changes have alerted the world to invest in alternative energy sources. Thermoelectric (TE) technology is responsible for innovating TE devices such as thermoelectric generators (TEGs) which are used to generate electrical energy from heat in an environmentally friendly manner. One of the challenges behind TEG is that they have low efficiency due to low figure of merit. Moreover the power generated is unstable and therefore needs proper power conditioning mechanism before it is connected to the load. The objective of this work is to analyze the performance of a boost dc dc converter connected on TEG system. The simplified models have been used as the basis of TEG design. Results indicate that the converter is able to stabilize and boost the voltage and higher converter efficiencies are achieved at different hot side temperatures.
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    A review on maximum power point tracking for photovoltaic systems with and without shading conditions
    (Renewable and Sustainable Energy Reviews, 2017) Ramli, Makbul A.M.; Twaha, Ssennoga; Ishaque, Kashif; Al-Turki, YusufA.
    This paper discusses maximum power point tracking(MPPT) methods of PV system for normal and partial shading conditions(PSC).The selected MPPT methods were classified as artificial intelligent, hybrid, and other MPPT methods.The comparison of researches on MPPT methods under normal condition and PSC reveals that researchers have concentrated more on shading conditions since the last few years mainly due to the need of power out put and efficiency improvements. It is believed that the information contained in this piece of work will be of great use for the researchers in the field under consideration.