45 research outputs found
Techno-economic analysis of multiple paralleled diesel generators for micro isolated applications
Conference ProceedingsThis paper analyses the key benefits of a multiple
paralleled diesel generator system over a "Single" diesel generator
system for supplying small remote and isolated loads. Even though
having several small diesel generators in parallel instead of one larger
one will certainly induce higher capital cost of the generating unit, the
resulting cost of kWh generated as well as the system is life cycle cost
can be significantly decreased . In this study, HOMER Pro software
is used to compare the technical, economic and environmental
performance of the two configurations. For the selected case study,
the simulation results reveal that multiple connected small diesel
generators instead on a single large one can be considered for rural
and isolated electricity generation
Optimized scheduling of diesel - renewable systems with pumped hydro storage
Published Conference ProceedingsThe present paper develops a model to optimize the
daily operation of a hybrid energy system consisting of a
photovoltaic unit, a wind unit, a pumped hydro storage system and
a diesel generator. The main purpose of the developed model is to
minimize the hybrid system’s operation cost while optimizing the
system’s power flow considering the different component’s
operational constraints. The simulations have been performed
using “fmincon” implemented in Matlab. The model has been
applied to two test examples; the simulation results are analyzed
and compared to the case where the diesel generator is used alone
to supply the given load demand. The results show that using the
developed control model, fuel saving can be achieved compared to
the case where the diesel is used alone to supply the same load
patters
A SURVEY OF DOMESTIC WATER HEATING TECHNOLOGIES
ProceedingsConference: ProceedingsIn South Africa, heating water for domestic use is one of the most energy consuming processes in residential
buildings. This process represents up to 60% of the total energy in the residential sector. Using more efficient and improved
technologies to heat domestic water can make a positive contribution to the fight against the country’s current energy crisis
which has a direct implication on the yearly increase in electricity prices. The purpose of this paper is to conduct a survey,
summarize and critically analyze the different technologies used to heat water for domestic purposes. The results of this
survey aim to identify gaps in the existing research, especially in the case of South Africa. Several research papers and other
academic studies are reviewed and classified based on their focus, contribution and the type of technology to achieve a
comfortable thermal level of water for domestic use. The key findings indicate importance of implementing hybrid systems
for increased reliability and hot water availability while minimizing operating costs
COOLING PHOTOVOLTAIC SYSTEMS: A SURVEY OF AVAILABLE TECHNOLOGIES
ArticleCooling is a key operation factor to take into consideration to achieve higher efficiency when operating solar photovoltaic systems. Proper cooling can improve the electrical efficiency, and the heat removed by the cooling system can be used in other domestic, commercial or industrial applications.
This paper is a survey of various methods that can be used to minimize the negative impacts of the increased temperature while making an attempt to enhance the efficiency of photovoltaic solar panels operating beyond the recommended temperature from the Standard Test Conditions (STC). These technologies are discussed based on their operation principles, technical advantages, and disadvantages. The results of this study highlight that any technology selected to cool a photovoltaic panel should be used to keep the operating surface temperature low and steady, be simple and reliable and, if possible, enable the use of extracted thermal heat to enhance efficiency of the overall conversion system
IMPACT OF DIFFERENT LOAD PROFILES ON SIZING AND PERFORMANCE OF A MICRO-HYDROKINETIC-BATTERY BASED HYBRID SYSTEM
Conference ProceedingsHydrokinetic hybrid systems are gaining more interest since hydrokinetic technology has proved to offer a cost-effective electrification solution. Very few research studies on sizing and optimization of micro-hydrokinetic-battery (MHK-B) based hybrid systems have been done. However, the authors did not explore the impact of different load profiles on optimal sizing and performance of the MHK-B hybrid system. In this study, the impact brought by different load profiles such as residential, commercial and industrial sectors on sizing and operation of a river based MHK-B hybrid system is investigated using Hybrid Optimization Model for Electric Renewable (HOMER) software. HOMER Pro version 3.6.1 has been selected since it is equipped with hydrokinetic turbine module. The flowing water resource data obtained from a typical river of South Africa has been used as an input. Sample of load profile curves for residential, commercial, industrial have been used to estimate the daily load demands. The optimum configuration results indicated that for the same daily energy consumption, the type of a load profile affects the battery storage capacity, hydrokinetic turbine size, inverter and rectifier operational hours as well as the annual excess energy for the MHK-B hybrid system
Grid-interactive micro-hydrokinetic with pumped-hydro storage: The case study of three South African demand sectors
Conference ProceedingsThis paper investigates the operation of different demand
sector such as residential, commercial and industrial load profiles
when supplied with a grid tied micro-hydrokinetic pumped-hydro
storage (MHK-PHS) hybrid system. The aim is to explore the demand
sector which is more favorable to the proposed grid-tied MHK-PHS
hybrid system under the time-of-use (TOU) tariff scheme. Hence, the
optimum configuration of the proposed MHK-PHS hybrid system is
determined in order to investigate the effect of each demand sector on
sizing and operation of the hybrid system. HOMER Pro Version 3.6.1
has been used to perform the optimization under TOU tariff scheme.
The results have shown that the industrial load sector incur the lowest
cost of energy at the highest capital cost as opposed to the residential
and commercial load sectors. However, from economic perspective,
the residential demand sector proved to be more favorable to the
proposed hybrid system due to the lowest net present cost (NPV). For
each load demand sector, HOMER led to oversizing constraint of the
hybrid system by not recharging the storage system after use
Modelling and simulation of a power converter for variable speed hydrokinetic systems
Conference ProceedingsThis study presents the control scheme model of a
micro-hydrokinetic turbine system equipped with a permanent
magnet synchronous generator (PMSG). A power conversion
system model is developed to allow a variable speed hydrokinetic
turbine system to generate constant voltage and frequency at
variable water speeds. A DC-DC boosting chopper is used to
maintain constant DC link voltage. The DC current is regulated to
follow the optimized reference current for maximum power point
tracking (MPPT) operation of the turbine system. The DC link
voltage is controlled to feed the current into the load through the
line-side pulse width modulation (PWM) inverter. The proposed
scheme is modelled and simulated using MATLAB/Simulink. The
results show a high quality power conversion solution for a variable
speed hydrokinetic river system
Hydro aeropower, an option for electricity cost reduction in farming applications
Conference ProceedingsThis paper develops a model which can be used to
minimize the electricity cost of South African farms through the
usage of a wind pump with pico hydro generator and a borehole in
pumped hydro storage configuration referred to as “hydro
aeropower”. This model will optimally schedule the generation
power flow from the pico turbine given the demand, the state of
water level in the reservoir as well as the electricity pricing period.
This model can be implemented to control the power flow in small
farming activities where boreholes and windmill are available.
Therefore, the wind and groundwater resources can be effectively
used to locally produce electricity which can contribute to the
decrease of the systems’ total operation costs
A survey of differential flatness-based control applied to renewable energy sources
Conference ProceedingsThis paper presents an overview of various methods used
to minimize the fluctuating impacts of power generated from
renewable energy sources. Several sources are considered in the
study (biomass, wind, solar, hydro and geothermal). Different
control methods applied to their control are cited, alongside some
previous applications. Hence, it further elaborates on the adoptive
control principles, of which includes; Load ballast control, dummy
load control, proportional integral and derivative (PID) control,
proportional integral (PI) control, pulse-width modulation (PWM)
control, buck converter control, boost converter control, pitch
angle control, valve control, the rate of river flow at turbine,
bidirectional diffuser-augmented control and differential flatnessbased
controller. These control operations in renewable energy
power generation are mainly based on a steady-state linear control
approach. However, the flatness based control principle has the
ability to resolve the complex control problem of renewable energy
systems while exploiting their linear properties. Using their
flatness properties, feedback control is easily achieved which
allows for optimal/steady output of the system components. This
review paper highlights the benefits that range from better control
techniques for renewable energy systems to established robust grid
(or standalone generations) connections that can bring immense
benefits to their operation and maintenance costs
A review of solar photovoltaic systems cooling technologies
Published ArticleCooling the operating surface is a key operational factor to take into consideration to achieve higher efficiency
when operating solar photovoltaic systems. Proper cooling can improve the electrical efficiency, and decrease
the rate of cell degradation with time, resulting in maximisation of the life span of photovoltaic modules. The
excessive heat removed by the cooling system can be used in domestic, commercial or industrial applications.
This paper presents a review of various methods that can be used to minimize the negative impacts of the
increased temperature while making an attempt to enhance the efficiency of photovoltaic solar panels operating
beyond the recommended temperature of the Standard Test Conditions (STC). Different cooling technologies
are reviewed, namely Floating tracking concentrating cooling system (FTCC); Hybrid solar Photovoltaic/
Thermal system cooled by water spraying; Hybrid solar Photovoltaic/ Thermoelectric PV/TE system cooled by
heat sink; Hybrid solar Photovoltaic/Thermal (PV/T) cooled by forced water circulation; Improving the
performance of solar panels through the use of phase-change materials; Solar panel with water immersion
cooling technique; Solar PV panel cooled by transparent coating (photonic crystal cooling); Hybrid solar
Photovoltaic/Thermal system cooled by forced air circulation, and Solar panel with Thermoelectric cooling.
Several research papers are reviewed and classified based on their focus, contribution and the type of
technology used to achieve the cooling of photovoltaic panels. The discussion of the results has been done based
on the advantages, disadvantages, area of application as well as techno-economic character of each technology
reviewed.
The purpose of this review is to provide an understanding for each of the above-mentioned technologies to
reduce the surface temperature of the PV module. The study will focus on the surface temperature reduction
array bound by each of the cooling technologies. The performance of each cooling technology will also be
highlighted. In addition to this study, this review will include a discussion comparing the performance of each
cooling technology. The outcomes of this study are detailed in the conclusion section.
This paper has revealed that any adequate technology selected to cool photovoltaic panels should be used to
keep the operating surface temperature low and stable, be simple and reliable and, if possible, enable the use of
extracted thermal heat to enhance the overall conversion efficiency. The presented detailed review can be used
by engineers working on theory, design and/or application of photovoltaic systems