|
Abstracts for research articles in the current volume: Volume 24
Volume 24 No 1
Volume 24 No 1: February 2013
Energy cost versus production as a
performance benchmark for analysis of companies
Houshang Taghizadeh and Mir Vahid Pourrabbi
In this paper, the efficiency of
automobile and auto-parts producing companies is evaluated, using
data envelopment analysis. The data envelopment analysis (DEA) is
based on the linear programming model. This model needs a series of
information by which the effectiveness and ineffectiveness of
decision-making units are determined. In the present research, the
inputs and outputs of the DEA model are determined by using the
basic criteria, and the energy efficiency of automobile and
auto-parts producing companies is specified. For this purpose, to
evaluate the energy efficiency of the automotive industry and auto
parts producing companies, deep2 software has been used. Finally,
based on the results of the study, the efficient and inefficient
companies have been identified and classified.
Measurement and verification of load
shifting interventions for a fridge plant system in South Africa
Rupert Gouws
In this paper, the author presents the
measurement and verification methodology used to quantify the
impacts of load shifting measures that are implemented on large
industrial fridge plant systems in South Africa. A summary on the
operation of fridge plant systems and the data typically available
for baseline development is provided. The author discusses issues
surrounding baseline development and service level adjustments for
the following two scenarios: 1) the electrical data is available for
both the baseline and post-implementation periods; and 2) only the
thermal data is available during the baseline period, but both the
thermal and electrical data is available during the
post-implementation period. Typical results are provided with
advantages and disadvantages of both methodologies.
Technologies for recovery of energy
from waste-waters: Applicability and potential in South Africa
William Stafford, Brett Cohen, Simisha Pather-Elias, Harro
von Blottnitz, Robert van Hille, Sue T L Harrison and Stephanie G
Burton
This study explored technologies for
recovering energy from wastewater through production of biomass,
combustion and gasification, generation of biogas, production of
bioethanol, heat recovery and microbial fuel cells. A first order
desktop analysis of the potential for applying these solutions to
wastewaters in South Africa revealed that 3 200 to 9 000 MWth of
energy has potential for recovery, equating to at most 7% of South
Africa’s current electrical power supply. Formal and informal animal
husbandry, fruit and beverage industries and domestic blackwater
were identified as wastewaters with the greatest potential for
energy recovery. Of the reviewed technologies, anaerobic digestion
shows applicability to the widest range of feedstocks. Net energy
generated, reduction in pollution, and water reclamation are
identified as the main benefits, but additional benefits such as
certified emission reductions, fertiliser production and the
production of secondary products may dictate the economic
feasibility.
The significance of relevance trees
in the identi-fication of artificial neural networks input vectors
G Manuel and JHC Pretorius
In the 1980s a renewed interest in
artificial neural networks (ANN) has led to a wide range of
applications which included demand forecasting. ANN demand
forecasting algorithms were found to be preferable over parametric
or also referred to as statistical based techniques. For an ANN
demand forecasting algorithm, the demand may be stochastic or
deterministic, linear or nonlinear. Comparative studies conducted on
the two broad streams of demand forecasting methodologies, namely
artificial intelligence methods and statistical methods has revealed
that AI methods tend to hide the complexities of correlation
analysis. In parametric methods, correlation is found by means of
sometimes difficult and rigorous mathematics. Most statistical
methods extract and correlate various demand elements which are
usually broadly classed into weather and non-weather variables.
Several models account for noise and
random factors and suggest optimization techniques specific to
certain model parameters. However, for an ANN algorithm, the
identification of input and output vectors is critical. Predicting
the future demand is conducted by observing previous demand values
and how underlying factors influence the overall demand. Trend
analyses are conducted on these influential variables and a medium
and long term forecast model is derived. In order to perform an
accurate forecast, the changes in the demand have to be defined in
terms of how these input vectors correlate to the final demand. The
elements of the input vectors have to be identifiable and
quantifiable. This paper proposes a method known as relevance trees
to identify critical elements of the input vector. The case study is
of a rapid railway operator, namely the Gautrain.
Load-shifting opportunities for
typical cement plants
Raine T Lidbetter and Leon Liebenberg
Investigations into demand side
reductions have been encouraged by the South African electricity
utility, Eskom, in sectors with high electricity consumption, such
as the cement industry. The South African cement industry is
responsible for 5% of the electrical consumption for the mining and
industrial sector. It has also been estimated that by 2020 this
sector will be ranked fifth for energy savings potential. This paper
investigates the potential of a load-shifting (altering energy use
method) scheme to reduce evening peak loads and save electrical
costs on a raw mill at a South African cement plant. A spread
sheet-simulation was performed, which showed that six hours of
load-shifting could be achieved, without adversely affecting
production. This was corroborated by a pilot study where the load
was successfully shifted for six hours over a week-long period. The
specific raw mill would achieve a reduction in yearly electrical
costs of 2% when employing this load-shifting strategy. The results,
however, showed that cost-saving opportunities are highly dependent
on the reliability of the mills and on the change in production
demand. Therefore, load-shifting schemes have to be flexible on a
daily basis to shift load whenever possible.
Conference papers
Optical design of low concentrator
photovoltaic modules
M A Benecke, E E van Dyk and F J Vorster
This paper addresses the necessary
procedures that need to be considered when designing an optical
sub-system of low concentrator photovoltaic (LCPV) module. CPV
systems make use of optical elements and solar tracking to
concentrate solar flux onto a photovoltaic (PV) receiver. The
performance of a concentrator module is highly dependent on the
configuration and alignment of the optical elements in the system.
In this study, various design considerations were taken into account
to construct a LCPV module that was characterised with respect to
optical design and electrical performance.
Thermal modelling of low concentrator
photovoltaic systems
JD Gerber, MA Benecke, FJ Vorster and EE van Dyk
Efficient thermal management of low
concentrator photovoltaic (LCPV) systems will allow maximizing of
the power output and may also substantially prolong operating
lifetime. For this reason, it is necessary to develop a thorough
understanding of the thermal transfer and dissipation mechanisms
associated with an LCPV system. The LCPV system under consideration
uses a 7-facet reflector optical design, providing a geometric
concentration ratio of approximately 4.85. The LCPV system succeeded
in increasing the short circuit current from 1A to 5.6A,
demonstrating an effective concentration ratio of approximately
4.75. LCPV system temperatures in excess of 80°C were recorded
without a thermal management system. A basic thermal model was
developed and assessed under various environmental conditions. The
effectiveness of a heat-sink, which reduced the temperature
difference between the LCPV receiver temperature and the ambient
temperature by 37.5%, was also evaluated. The results discussed in
this paper will assist the future development of techniques aimed at
reducing the high temperatures associated with LCPV systems.
Evaluation of feed-in tariff-schemes
in African countries
M Meyer-Renschhausen
Almost all African countries are
planning to increase their power supply capacities and to diversify
the resource base of the electricity sector. In sharp contrast to
the ambitious objectives, grid connected power plants, based on
renewable energies, are very rare except large scale hydropower in
African countries. The small number of renewable energy (RE)-plants
in Africa shows that a quick diffusion of these technologies cannot
be expected from the dynamic of market forces alone. Political
support is necessary. By now, feed-in tariffs (FIT) is the most
prominent economic instrument promoting renewable energy
technologies in the power sector. They are applied in more than 50
countries, among them several African countries like Algeria, Kenya,
Uganda, Ghana and Tanzania. The objective of the paper is to
investigate the outcome and effectiveness of African FIT-schemes. It
is assumed that most of the FIT-schemes in Africa are poorly working
because of unfavourable institutional design, insufficient level of
FIT rates or obstacles in the process of implementation.
Deficiencies in the design of FIT-schemes and the implementation
process can be explained by conflicting policy targets like
affordable power prices and grid stability but also with an unclear
allocation of property rights that can lead to time-consuming
negotiations of Power Purchase Agreements.
A concentrating solar power value
proposition for South Africa
Paul Gauché, Theodor W von Backström and Alan C Brent
Concentrating solar power (CSP) offers
the potential for a high degree of localization and an alternative
strategy to meet electricity demand for South Africa in a future of
uncertain conventional resources. The integrated resource plan (IRP)
makes strides to introduce renewables to the electricity generation
system by 2030, but we argue that the proposed energy mix is too
reliant on resources that are not only unsustainable but also at
risk in the short to medium term. Coal and other conventional
resources may be more limited than originally anticipated, which if
true, requires action to be taken soon. CSP is currently the only
sustainable and dispatchable energy technology that could
domestically supply a significant portion of South Africa’s
electricity needs. A balanced mix of PV, wind and CSP can provide
the energy supply needed in South Africa, but steps are required
soon to take advantage of the localization potential and excellent
sustainable energy resources.
Efficiency and costs of different
concentrated solar power plant configurations for sites in Gauteng
and the Northern Cape, South Africa
Thomas Telsnig, Ludger Eltrop, Hartmut Winkler and Ulrich Fahl
Concentrated solar power (CSP) plants
can play a major role in the future South African electricity mix.
Today the Independent Power Producer (IPP) Procurement Programme
aims to facilitate renewable energy projects to access the South
African energy market. In spite of this incentive programme, the
future role of CSP plants in South Africa has yet to be defined.
Using hourly irradiance data, we present a new method to calculate
the expected yield of different parabolic trough plant
configurations at a site in each of Gauteng and the Northern Cape,
South Africa. We also provide cost estimates of the main plant
components and an economic assessment that can be used to
demonstrate the feasibility of solar thermal power projects at
different sites. We show that the technical configurations, as well
as the resulting cost of electricity, are heavily dependent on the
location of the plant and how the electricity so generated satisfies
demand. Today, levelised electricity costs for a CSP plant without
storage were found to be between 101 and 1.52 ZAR2010/kWhel,
assuming a flexible electricity demand structure. A CSP
configuration with Limited Storage produces electricity at costs
between 1.39 and 1.90 ZAR2010/kWhel, whereas that with Extended
Storage costs between 1.86 and 2.27 ZAR2010/kWhel. We found that
until 2040 a decrease in investment costs results in generating
costs between 0.73 ZAR2010/kWhel for a CSP plant without storage in
Upington and 1.16 ZAR2010/ kWhel for a configuration with Extended
Storage in Pretoria. These costs cannot compete, however, with the
actual costs of the traditional South African electricity mix.
Nevertheless, a more sustainable energy system will require
dispatchable power which can be offered by CSP including storage.
Our results show that the choice of plant configuration and the
electricity demand structure have a significant effect on costs.
These results can help policymakers and utilities to benchmark plant
performance as a basis for planning.
Potential and future of concentrating
solar power in Namibia
Y Le Fol and K Ndhlukula
The Namibian
electricity sector has mainly relied on electricity imports from the
Southern African Power Pool (SAPP) over the last decade. However, a
growth in electricity demand and scarce import options could cause
energy shortages. Therefore, new power plants ought to be
commissioned in the near future to avoid the forecasted energy
crisis. In this context, Concentrating Solar Power (CSP) generation
is regarded as an appropriate alternative to conventional energy
technologies, particularly for the excellent solar regime available
in Namibia. The study presents a GIS analysis that identifies
suitable areas for CSP establishment. A broad range of geographical
parameters such as solar radiation, topography, hydrology or land
use are examined. The calculations show that the CSP ceiling
generation in Namibia is equivalent to 70% of the worldwide
electricity production. Moreover, the study offers a scenario
analysis where concrete CSP alternatives are compared to coal-fired
plant projects developed by the national power utility. Meteonorm
and System Advisor Model (SAM) are used to design CSP alternatives
located in the area offering the best combination between high solar
irradiation and short distances to the infrastructures. Despite the
affordability concern which has to be addressed with sound financial
instruments, CSP represents a seminal opportunity for the energy
sector in Namibia.
|
