3 research outputs found
Improving the performance of hybrid wind-diesel-battery systems
Off-grid hybrid renewable energy systems are known as an attractive and sustainable
solution for supplying clean electricity to autonomous consumers. Typically, this
applies to the communities that are located in remote or islanded areas where it is not
cost-effective to extend the grid facilities to these regions. In addition, the use of
diesel generators for electricity supply in these remote locations are proven to be
uneconomical due to the difficult terrain which translates into high fuel
transportation costs. The use of renewable energy sources, coupling with the diesel
generator allows for the diesel fuel to be offset. However, to date, a common design
standard for the off-grid system has yet to be found and some challenges still exist
while attempting to design a reliable system. These include the sizing of hybrid
systems, coordination between the operation of dissimilar power generators and the
fluctuating load demands, optimal utilisation of the renewable energy resources and
identifying the underlying principles which reduce the reliability of the off-grid
systems.
In order to address these challenges, this research has first endeavoured into
developing a sizing algorithm which particularly seeks the optimal size of the
batteries and the diesel generator usage. The batteries and diesel generator function
in filling the gap between the power generated from the renewable energy resources
and the load demand. Thus, the load requirement is also an important factor in
determining the cost-effectiveness of the overall system in the long run. A sensitivity
analysis is carried out to provide a better understanding of the relationship between
the assessed renewable energy resources, the load demand, the storage capacity and
the diesel generator fuel usage.
The thesis also presents the modelling, simulation and experimental work on the
proposed hybrid wind-diesel-battery system. These are being implemented with a
full-scale system and they are based on the off-the-shelf components. A novel
algorithm to optimise the operation of a diesel generator is also proposed. The
steady-state and dynamic analysis of the proposed system are presented, from both
simulation and an experimental perspective. Three single-phase grid-forming
inverters and a fixed speed wind turbine are used as a platform for case studies. The
grid-forming inverters adopt droop control method which allows parallel operation of
several grid-forming sources. Droop control-based inverters are known as
independent and autonomous due to the elimination of intercommunication links
among distributed converters. Moreover, the adopted fixed speed wind turbine
employs a squirrel cage induction generator which is well known for its robustness,
high reliability, simple operation and low maintenance. The results show a good
correlation between the modelling, the experimental measurements, and the field
tested results.
The final stage of this research explores the effect of tower shadow on off-grid
systems. Common tower designs for small wind turbine applications, which are the
tubular and the lattice configurations, are considered in this work. They generate
dissimilar tower shadow profiles due to the difference in structure. In this research,
they are analytically modelled for a wind turbine which is being constructed as a
downwind configuration. It is proven that tower shadow indeed brings negative
consequence to the system, particularly its influence on battery lifetime within an
off-grid system. This detrimental effect occurs when power generation closely
matches the load demand. In this situation, small frequent charging and discharging
cycles or the so called microcycles, take place. The battery lifetime reduction due to
these microcycles has been quantified and it is proven that they are not negligible
and should be taken into consideration while designing an off-grid hybrid system
African Handbook of Climate Change Adaptation
This open access book discusses current thinking and presents the main issues and challenges associated with climate change in Africa. It introduces evidences from studies and projects which show how climate change adaptation is being - and may continue to be successfully implemented in African countries. Thanks to its scope and wide range of themes surrounding climate change, the ambition is that this book will be a lead publication on the topic, which may be regularly updated and hence capture further works. Climate change is a major global challenge. However, some geographical regions are more severly affected than others. One of these regions is the African continent. Due to a combination of unfavourable socio-economic and meteorological conditions, African countries are particularly vulnerable to climate change and its impacts. The recently released IPCC special report "Global Warming of 1.5º C" outlines the fact that keeping global warming by the level of 1.5º C is possible, but also suggested that an increase by 2º C could lead to crises with crops (agriculture fed by rain could drop by 50% in some African countries by 2020) and livestock production, could damage water supplies and pose an additonal threat to coastal areas. The 5th Assessment Report produced by IPCC predicts that wheat may disappear from Africa by 2080, and that maize— a staple—will fall significantly in southern Africa. Also, arid and semi-arid lands are likely to increase by up to 8%, with severe ramifications for livelihoods, poverty eradication and meeting the SDGs. Pursuing appropriate adaptation strategies is thus vital, in order to address the current and future challenges posed by a changing climate. It is against this background that the "African Handbook of Climate Change Adaptation" is being published. It contains papers prepared by scholars, representatives from social movements, practitioners and members of governmental agencies, undertaking research and/or executing climate change projects in Africa, and working with communities across the African continent. Encompassing over 100 contribtions from across Africa, it is the most comprehensive publication on climate change adaptation in Africa ever produced