JESA Volume 15 (abstracts only)
JESA Volume 15 (abstracts only)
Vol. 15 No. 1: February 2004
• The potential impact of an electricity basic services tariff in non-grid electricity M. Wentzel and M. Pickering
• The impact of solar electric services on lifestyles – experiences from Zambia M. Gustavsson
In 1998 the Government of Zambia launched a solar dissemination project, aimed at supporting the creation of three Energy Service Companies (ESCO). The project was funded by SIDA (Sweden). Today these companies are operating a total of 400 solar home systems. The companies have received loans from the Government for the solar systems, which are put in the houses of their clients. A survey was carried out covering all 400 clients. In addition, neighbours of the clients were targeted. Results from the survey show that the integration of a solar home system will have an impact on the user’s livelihood. Light will be stronger and become more abundant. But hours of light are not differing between clients and neighbours. It is kept for about 3.4 hours and 3.2 hours respectively. The improved light opens possibilities to read and extend working hours. Children are reported to be the main beneficiaries of solar power. Radio cassette recorders, followed by television sets are the most common appliances found. Appliances are used for 2-3 hours per day. Clients describe that they feel that their lives have become more urban and modern. One third have experienced problems with their system. In the majority of the client households (87%), there are one or more members with a conventional salary. A service fee is paid monthly, and this fee is normally found ‘reasonable’. In most cases, clients want to own the systems instead of keeping a service contract. Clients spend about ZMK 51 900 (USD 11.8) per month on energy services compared to neighbours spending about ZMK 33 800 (USD 7.7). The distribution between expenses on electric services, and for cooking fuel is similar for neighbours and clients, 1/3 on cooking fuel and 2/3 on electric services. The results from this case study indicate that solar power has a positive impact but has not been accessible for the low-income groups in the setting.
• ThermaL management of SUNSAT using TAS R. T. Dobson, P. A. van Wyk and K. van der Westhuizen
South Africa's first microsatellite SUNSAT was launched from Vandenburg Air Force base in February 1999. SUNSAT was subjected to an orbital drift that altered its polar orbit with an eclipse period of 36 minutes in July 1999, to one of an eclipse period equal to zero minutes in June 2000. The temperature sensors indicated that the batteries heated from 20°C to 37°C over this period. SUNSAT ultimately failed in February 2001. This paper shows how the battery temperature was simulated using Harvard’s thermal modelling software TAS (Thermal Analysis Systems). TAS is checked against a lumped parameter model and the results compared to within 2°C. TAS was then used to model SUNSAT and the battery and solar panel temperatures compared favourably with telemetry data. General thermal management considerations and improvements and recommendations for future microsatellites are discussed.
• A framework for energy management in cryogenic air separation plants T.J. Kruger and J.E. Calmeyer
Steel, petrochemicals, metallurgy, explosives, food and many other industries require large amounts of air products such as oxygen and nitrogen. Cryogenic air separation technology, unlike other air separation technologies, is in a mature stage of its life cycle and currently the only practical means available for mass-production of these air products. Inherent to its operation, cryogenic air separation plants are generally energy intensive and power input is considered the main factor on which the ultimate production cost will depend. Experience has shown that relatively small improvements in energy efficiency on these plants generally result in a significant reduction of production costs.
This paper discusses the means for effective energy management at these plants, aimed at ultimately reducing the electrical cost per quantity of air product produced. It introduces a model, aimed at the manager responsible for energy management at cryogenic air separation plants.
Vol. 15 No. 2: May 2004
• Gender and income generation: a case of the Malamangwa community, Limpopo Province, South Africa K G Banda and E M Tinto
The Integrated National Electrification Programme plays an important role in the socio-economic development of South African society by providing modern energy. In this socio-economic development project, government has put in place issues of Black Economic empowerment and small, medium and macro-enterprises as the goal towards local economic development and self-reliance, which are boldly highlighted virtually in all the policy documents of South Africa. Rural Electrification should address these challenges as they are integral of rural development or else, integrated electrification should be equal or translated into local economic development. This paper reports part of the findings of a research project carried out by the AFREPREN on renewable energy. It involved a case study of the Malamangwa community in rural Limpopo Province of South Africa. Women in this community, like all rural areas, are overburdened in their day-to-day reproductive and productive work and depend on natural resources for survival. The community is further characterised by differences in gendered income levels, unemployment levels and limited modern energy services that perpetuate the already oppressive living conditions of both men and women. It is strongly argued in this paper that electrification, particularly through renewable energy, could undoubtedly help in poverty eradication and sustainable development of historically deprived communities.
• An energy management tool for cryogenic air separation plants J Calmeyer and J Kruger
Steel, petrochemicals, metallurgy, explosives, food and many other industries require large amounts of air products such as oxygen and nitrogen. Cryogenic air separation technology is, unlike other air separation technologies, in a mature stage of its life cycle and currently the only practical means available for mass-production of these air products. Inherent to its operation, cryogenic air separation plants are generally energy intensive and power input is considered the main factor on which the ultimate production cost will depend. Experience has shown that relatively small improvements in energy efficiency on these plants generally result in a significant reduction of production cost. This paper discusses an energy management tool that may improve the energy efficiency of the plant and could serve as a supplement to existing energy management efforts. The tool takes the form of several mathematical models and could be of great value in reducing product cost.
• Energy management at a tertiary institution J F van Rensburg, C P Bodenstein and E H Matthews
Energy Management is an increasingly important issue for all tertiary institutions in South Africa because of budget cuts and increased financial strain. This paper describes the history and initiatives taken at the Potchefstroom University for Christian Higher Education (PU for CHE). The research focussed on the success of the existing energy management system that used load shedding of hostel heating loads to lower the maximum demand on campus. The research also includes a detail site audit of all the electrical loads on campus. It involved the installation of a campus wide sub-metering network to disaggregate the campus electricity load down to building level. The results indicate the effect of the remaining building load on the campus load profile and the possibilities to further lower the campus demand profile by energy management on the commercial campus buildings. Suggestions are made to techniques that can be used to further reduce the cost of electrical energy on campus.
• Methods for calculating the effect on radiation income of inter-row shading in solar energy collector arrays T Hove
Two methods for analysing the effects on solar radiation income, of inter-row shading, in a multi-row solar energy collector array, are presented and compared. The first method is simple to handle with hand or spreadsheet calculations but neglects the end-effects. It is recommended for handling shading calculations only when the collector row length is very long relative to other system dimensions (in the present case, W/L >5). The second method is rather lengthy but can handle shading calculations on collector rows of any relative lateral dimensions. It is also recommended for short rows or when analysing the electric energy output of photovoltaic modules, since they are extremely sensitive to partial shading. When used to estimate available solar energy on a short-row collector array, the first method over-estimated the shading effect on radiation income by 8% in mid-winter at latitude 19.7oS (Gweru, Zimbabwe), when the second method is taken as datum. Although the two methods are in agreement in the general way radiation income on the shaded array varies with collector tilt angle, they prescribe significantly different optimal tilt angles. This underlines the importance of selecting a fairly accurate method of shading analysis in order to correctly specify one of the important design parameters in collector deployment in an array- the collector tilt angle. The complete specification of collector deployment in an array, however, not only involves the specification of the tilt angle, but also the optimal combination of tilt angle and row-spacing-to-collector-length ratio that results in maximum cost-effectiveness.
Volume 15 No 3: August 2004
• The energy profile of a rural community PJ Lloyd, A Dick and M Howells
We present the results of a survey on domestic energy use in the community of Nkweletshini in south-western Kwa-Zulu Natal during 2002. The community has a low housing density, below the 50 households per km2 measure used by Eskom as the limit for future electrification. Houses were modest, with a median number of 3 rooms, and built of either clay or cement blocks, and generally thatched although some had corrugated iron roofs. Many in the community are employed, but it is relatively low-level employment, with a median income of about R660/month/household. 96% of all households cook on wood collected free of charge in the vicinity. 3% cook on paraffin and 1% on LP gas. The primary appliance is a wood stove; 4% of the households use an open brazier (“imbaula”). 78% of households reported problems with the fuel they used because it made them cough (43%); it smelled (30%); or it smoked and hurt the eyes (24%). 65% of the households reported a second choice of fuel, which was generally paraffin. The cost of paraffin relative to wood was cited as its major disadvantage. Cleaner fuels were preferred on social occasions, when the household had guests. Cooking took place once or twice a day, rarely in the evening, food cooked earlier in the day being heated for an evening meal. The profiles for space heating and water heating were very similar to that for cooking, with a significant quantity of wood being burned for these purposes even in summer. Space heating took place throughout the day, with a morning peak between 06h00 and 08h00, starting somewhat earlier in winter. There was little water heating during the day.
There were two sources of lighting in the community, candles (70%) and paraffin lamps (30%). 59% of the candle users did not like the source of light, while 62% of the paraffin users did not like lamps. The average household bought 3 packets (each containing 6 candles) per month. The primary appliances in Nkweletshini were radios (91%, battery powered); kettles (86% of households, non-electrical); television (34%, battery powered), and cell phones (17%, battery powered). Average radio use was close to 24 h/day. The average household consumed 12.1bundles of wood per month, or somewhere between 300 and 400 kg of wood. Most households collected wood themselves – only two relied on neighbours or relatives. Wood collection was clearly a major effort. Most wood was collected first thing in the morning, somewhat earlier in summer than in winter, but even in winter 25% of the households were collecting wood between 04h00 and 06h00. It was only between the hours of midnight and 04h00 that collection ceased. 94% of the householders purchased paraffin. Monthly volumes averaged 12.6 litres per household that bought paraffin. The calculated average price was R3.00 per litre, which is very close to the known cost of paraffin in the area. Over 20% of households made use of car batteries, primarily for television, and recharged them twice a month on average. 67% of the households purchased the 9V PM9 batteries, primarily for radio, using 2 per month on average. Less than 10% of the households made much use of torches, buying about 4 batteries per month. These results are discussed in terms of the total energy demand of the households (4 000 to 5 500 MJ/month) and the time-of-day requirements that peak in the early morning rather than in the evening as is the case in urban and semi-urban environments. The potential impact of the electricity basic services support tariff on indoor air pollution and health in South Africa
• D A Sparks
An electricity basic services support tariff is being introduced in South Africa to alleviate the worst impacts of poverty by providing a free portion of electricity to customers. Linked to this are obvious social and economic benefits and impacts, but also the potential to realise environmental and health benefits. One of the main benefits in this regard is the potential for increased electricity use to reduce indoor air pollution and hence the associated health impacts such as acute respiratory infections in children and chronic obstructive pulmonary disease in adults. This would require a primary shift in fuel use away from using wood, coal and paraffin for heating and cooking purposes towards using electricity to meet these energy needs.
• Economically optimal deployment of collector rows in a multi-row solar energy array T Hove
A procedure for determining the design variables, row spacing and collector tilt angle, for collector deployment in a multi-row solar energy array, where shading of collector rows by neighbouring ones is inevitable, is described in this paper. Optimal spacing and tilt were determined by means of a techno-economic analysis, taking into account the trade-off between the need for maximal energy collection performance, on one hand, and the corresponding collector and field costs, on the other. The average cost of input solar energy, defined as the sum of collector and fields cost per unit of solar energy income onto the array, was identified as a suitable economic indicator, and used to compare the suitability of different magnitudes of row spacing. The study first determines a functional relationship, for maximum radiation income, between the collector tilt angle, β, and the row spacing (characterised by the dimensionless quantity, S/L). This is then used to calculate the annual average solar radiation income on the shaded collector, which is a variable in the equation for average energy cost, together with collector and field cost parameters. A design chart that enables a direct determination of both the spacing and tilt, with the ratio of field to collector unit area cost, Cf/Cc., as input, is presented. It is observed that a single value of S/L, located at the elbow of the locus of minimum average costs, can adequately represent the design S/L for all values of Cf/Cc. The design β values obtained from the study, for two different locations, are considerably lower than those that would have been prescribed for the same collectors using the rule of thumb ‘collector tilt angle equal latitude of location’. This underlines the importance of a detailed analysis, as carried out in this study, in determining this design variable, as the value of β can also have implications on structural costs for collector stands.
• An energy management decision tool for induction motor replacement/renewal J E Calmeyer and T J Kruger
In an energy intensive plant, large induction motors are usually utilized as drivers for non-linear loads such as compressors, fans, pumps or blowers. These motors are usually required to operate on a continuous basis meaning that, over time, even a relatively small degradation in electromechanical efficiency may lead to a significant loss in energy costs. High-efficiency motors are usually considered the obvious solution to upgrade plant energy efficiency, but as described in this paper, they may not always deliver the expected results, especially when dealing with non-linear loads. Maintenance on induction motors calls for constant refurbishment and, ultimately, replacement; both these actions have a direct impact on the overall plant energy efficiency. What is needed is a means for quantifying actual power savings when attempting to upgrade induction motor electromechanical efficiency and also to have some means available for aiding the decision-making between replacement and renewal. With regard to induction motors applied to (the previously mentioned) non-linear loads, this paper describes a tool that can be used to quantify actual power savings when altering electromechanical efficiency and also to assist the replacement/renewal decision from an energy management perspective.
Volume 15 No 4: November 2004
• The influence of temperature and total solid concentration on the gas production rate of a biogas digester P Mahanta, UK Saha, A Dewan and P Kalita
In the present investigation, laboratory level experiments were carried out to investigate the effect of temperature and total solid concentration on the performance of biogas digesters. The gas production rate with batch model type of digesters was studied under controlled as well as uncontrolled temperature conditions. In each case, cattle dung-water mixture with total solid (TS) concentration of 2.5 %, 8 % and 12.5 % were considered. In the case of biogas production, digesters were maintained at constant temperatures of 30 0C, 35 0C, 40 0C and 45 0C. The weekly pH value in each case has also been monitored. The present investigation shows an increase of gas production under a controlled temperature of 350C and with 8% TS concentration.
• National policies and the CDM: Avoiding perverse incentives H Winkler
The CDM is a project-based mechanism to promote flexibility in mitigation climate change, by promoting investment in mitigation projects in developing countries. There has been concern about potential perverse incentives for developing countries like South Africa not to adopt progressive national policies, fearing that CDM projects implementing such policy would no longer be additional. The CDM rules on additionality require that emissions are reduced “below those that would have occurred in the absence of the registered CDM project activity”. The paper shows that recent decisions by the CDM Executive Board make it clear that such perverse incentives will not be created. The paper suggests concrete interpretations of this guidance for two possible project types. Projects implementing national policies that promote zero- or low-carbon emission technologies (e.g. South Africa’s renewable energy target) can still go through the CDM process. Where there are local regulations, as for landfill gas, projects would not be ruled out entirely, but would receive credit for the difference between actual methane capture and that needed to meet local safety, health and environmental standards. The author concludes that projects implementing progressive energy policies are still eligible for CDM investment.
• Domestic use versus income generating activities in delivering modern energy to rural Botswana JE Mbaiwa and OD Gontse
This paper provides a descriptive analysis of the provision of modern energy in the rural areas using Botswana as a case study. The study emanates from a broader government objective of providing essential services such as energy to the rural population. The paper reviews the current strategies used by government to provide modern energy to rural areas and, in the process, assesses its efficiency and shortcomings. The paper relied more on secondary data sources and review of previous studies on rural energy development in Botswana. Results indicate that previous government attempts aimed at providing modern energy to rural areas targeted household or domestic use without much consideration for income generating activities. This approach resulted in the low dissemination of modern energy to rural areas. However, this paper argues that income-generating activities may accelerate the process of providing modern energy to rural areas. Income generating activities can provide both the rural population with the necessary income to purchase modern energy as well as creating demand for modern energy utilisation; hence, making provision of energy in rural areas a viable option. The distribution of modern energy to rural areas is perceived to be necessary, as it has the potential to eradicate poverty and contribute to sustainable rural livelihoods particularly if energy is used for income generating activities.
• The findings on the pilot study application of the South African Energy and Demand Efficiency Standard CA van der Merwe and LJ Grobler
The South African Energy and Demand Efficiency Standard (SAEDES) is an energy- efficiency guideline initiated by the Department of Minerals and Energy (DME) and the Council for Scientific and Industrial Research (CSIR). The DME sponsored a pilot study to test SAEDES for its applicability, viability and practicality in the South African commercial building sector over the past three years. The best method to evaluate a guideline is to implement it and determine where the guideline either lacks or is too excessive in providing minimum requirements. The SAEDES was imposed on three new and three existing buildings. In every study, SAEDES was able to identify energy-efficiency opportunities and provide financially viable recommendations for most of these opportunities in order to get the building to comply 100% with SAEDES. Savings of up to 16% on the total annual energy bill was achieved on two of the six pilot buildings. This study clearly showed that SAEDES is able to provide cost-effective recommendations for the reduction of energy consumption and is well suited for the South African commercial building sector. This study also shows that SAEDES is not only applicable to building owners, but also to building managers, contractors and designers.