Browsing by Author "Hibberd, Andrew"

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    Open Access
    An analysis of annual environmental conditions and heat gains, and theoretical assessment of approaches to improve summer thermal comfort, of the Energy Research Centre at the University of Cape Town
    (2017) Cunliffe, Guy Edward; Hibberd, Andrew; Moorlach, Mascha
    The Energy Research Centre (ERC), a research centre located at the University of Cape Town (UCT), is considering retrofitting its offices with measures to improve its occupants' thermal comfort, particularly during Cape Town's summer months. While a simple solution would be to install an active cooling system, first consideration should be given to the deployment of preventative cooling measures and retrofits. By these means, the costs of an active cooling system would be reduced, as well as the building's relative increase in energy consumption and indirect greenhouse gas emissions. This dissertation examines internal thermal conditions of the ERC under current building conditions and predicts levels of thermal discomfort likely to be experienced by occupants, with emphasis on Cape Town's summer season. Heat gain components to the ERC are quantified, and a Base Case cooling scenario is determined; this characterises the peak cooling load and active annual cooling energy required to alleviate summer thermal discomfort, if no other interventions are implemented. Thereafter, the impacts of a selection of preventative cooling measures on the Base Case cooling scenario are assessed, and a theoretical payback period for each progressive measure is evaluated, relative to projected installation and operational costs of an active system designed to meet the Base Case. A model of the ERC offices is developed in DesignBuilder, which characterises thermal properties of the building envelope, thermal loads of lighting, electronic equipment and building occupants, and effects of prevailing weather patterns and solar radiation at the site of the building. Physical energy simulations of the model are run in EnergyPlus, which uses a series of algorithms based on the Heat Balance Method to quantify internal psychrometric conditions and heat gains in half-hourly iterations. An EnergyPlus Ideal Loads Air System component is input into the simulation to quantify the active cooling load required to maintain comfortable design conditions. The results indicate that 7 814.5 hours of thermal discomfort are experienced annually across the ERC (divided into eight thermal zones in the DesignBuilder model), with 37.6% of discomfort hours occurring between December and March, and 12.8% in February alone. Notably, a greater proportion of discomfort hours, 38.9%, were predicted for winter months (June through August). However winter thermal discomfort was not addressed in detail here, as the scope of the dissertation was limited to analysing ERC cooling only. Solar gains through external windows were found to be the largest single source of annual heat gain (20.65 MWhth), followed by heat gains due to lighting heat emissions (19.99 MWhth). Profiles during typical summer conditions showed significant heat gain also arises from conduction through the ceiling, due to existing but sporadic and thin layers of fibreglass ceiling insulation, with gaps that allow thermal bridging between the roof space and ERC thermal zones. The Base Case annual cooling requirements were determined to be 27.64 MWhth, while peak cooling load was found to be 66.87 kWth. Sensible cooling dominated total cooling loads in summer months. East and west facing thermal zones required the greatest cooling energy (normalised per floor area), having been shown to experience the greatest normalised solar and lighting heat gains. Inclusion of a 75 mm polyester fibre insulation layer above the ceiling boards would result in a 13.6% decrease in annual discomfort hours, relative to the current building condition, and reduced peak cooling load by 19% relative to the Base Case. Increasing thickness above 75 mm resulted in increased ceiling thermal resistance and further reduced annual discomfort hours. However, the marginal improvements in thermal comfort were found to decrease with increased insulation thickness. A 75 mm thickness of polyester fibre insulation was therefore selected as the first preventative measure to be considered for the ERC, and was included in all further assessment of additional preventative options. Lighting retrofits were also considered, by means of two progressive measures: Delamping – the removal of fluorescent luminaires from overly lit thermal zones – and Relamping – replacement of remaining fluorescents and light fixtures with more energy efficient technology (as well as the Delamping and Insulation measures). Delamping was found, from simulation analysis, to reduce lighting heat gains by 31%, relative to the Base Case and annual cooling requirements by 24%, with total projected costs after 10 years reduced by 15.6% relative to the Base Case. Relamping had a less pronounced impact on cooling requirements, but resulted in 15 % lower lighting energy use compared to Delamping only. The final measure considered was a Shading measure, whereby the replacement of the existing solar window film, currently fitted to each of the ERC's external windows, with internal adjustable shading. The Shading retrofit (in addition to all previous preventative measures) was found to cause a 35% reduction in annual cooling energy relative to the Base Case, as well as a 7% relative to the Relamping scenario. However, cost evaluation showed that costs of implementing the Shading retrofit significantly outweighed net incremental annual savings achieved under the measure, and was thus not recommended as a preventative option for the ERC. Alternative shading options, such as fixed external shading, may prove more cost effective in mitigating the ERC's solar heat gains, and should be considered in further research. From these results, it was concluded that a combination of insulation and lighting upgrades would provide the greatest benefit, in terms of thermal comfort, to the ERC, and would result in a more cost effective active cooling system, should one be proposed. The dissertation ended with recommendations for further work, including further analysis of ERC heating requirements in winter, and investigation into additional and alternative cooling methods, such as passive or solar cooling.
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    Barriers to energy-efficiency implementation: a study of the uptake of energy-efficiency initiatives offered through incentive schemes in South Africa
    (2016) Parker, Victoria Daniela; Hibberd, Andrew
    Energy efficiency has been widely recognised as a powerful tool for improving the energy situation across the globe. Whether by increasing energy security, reducing carbon emissions or alleviating grid strain, proven methods of energyefficiency management can bring about significant savings at a multitude of levels. Although energy-efficiency practices are gaining traction globally, their uptake is still less than optimal, and this is especially true of South Africa. The country is currently facing an energy crisis that brings with it a variety of complex challenges, all which can be assuaged through energy efficiency, if applied to the energy-intensive economy. It is important to understand the South Africa-specific barriers that hinder implementation of energy efficiency. While government has made strong commitments to supporting the uptake of energy-efficiency initiatives, there have been several interruptions and a lack of execution. An abundant amount of topdown research has been conducted to identify the various barriers to implementation; far less research, however, identifies barriers from within these energy-intensive economies. If these barriers could be identified from a more qualitative and participant-centred perspective, the key role-players in the sector might be able to better address energy-efficiency implementation, leading to more widespread benefits and results. To this end, the researcher performed an explanatory investigation, analysing seven energy-intensive companies that had recently participated in a fully funded local incentive scheme called the Private Sector Energy Efficiency Programme (PSEE). The PSEE performed an energy audit on each company, followed up by a report on its findings. The report clearly outlined the company's key energy-savings opportunities, in kilowatt-hours (kWh), Rand and CO2 emissions. It also estimated the costs and payback periods of the projects. Despite these reports indicating significant savings potentials and reasonable payback periods, a lack of uptake still remained. The researcher extracted and analysed the relevant quantitative data from the PSEE reports and conducted one-on-one, semi-structured interviews with the participants to identify and understand the participant-specific barriers to the recommended energy-efficient measures. The researcher also interviewed three coordinators of the PSEE programme, in the hope of identifying any PSEEspecific barriers. The other main party involved in this research was PSEE energy-efficiency ESCO which has been given an alias name ESCO E, who delivered the reports to the participants. The research found that the barriers in place in South Africa resemble those that have been identified at the global level. However, the mixed-methods approach and data sample employed in this study create a very interesting picture about the barriers that exist at the company level. The research found that there were significant saving opportunities available to companies but that, mainly due to a lack of financial support, human-resource capacity and time, there has been little to no implementation of the recommended projects. The available literature and provided global experience, coupled with participants' responses and suggestions, allow the researcher to make relevant recommendations that pertain to the study: • Lower payback periods through further incentives • Accessible funding and subsidies • Ensured continuation, longevity and growth of incentive programmes • Client-specific cost alternatives • Extensive and supported detail around each recommendation • Human resource capacity support to ensure energy management • Required energy seminars and skills training to programme participants • Increased government support and energy efficiency resources; namely an Energy Hub, which will provide a stable platform for energy efficiency • Participant-specific report alignment to encourage uptake and increased trust between incentive host and participant • More stringent government regulated technological standards.
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    Reducing industrial energy costs through energy efficiency measures in the South African foundry industry - evaluation and opportunities of a South African foundry
    (2016) Thiel, Dennis; Hibberd, Andrew
    Due to lack of generation capacity and high energy intensities South Africa's electricity supplier is forced to shut down high energy users frequently. Power cuts as well as escalating electricity prices threaten the country's steel industry. The objective of this study was to identify cost-effective energy efficiency improvements for the South African foundry industry. A lack of research in South African foundries was identified as existing literature on the topic was analysed. A large foundry operating an induction furnace in the Western Cape served as subjects to investigate the topic specifically in South Africa. The aim was to identify the energy intensity, evaluate already implemented energy efficiency measures and identify further opportunities to reduce energy cost of the foundry. The method followed for the data collection was much orientated on an industry energy audit. Types of energy, amounts and cost of energy usage were determined. The energy consumption and energy intensity of the foundry were analysed, based on meter readings, electricity bills and where necessarily a "bottom-up" approach for estimation was used. Results of the energy audit have shown that the foundry under review consumes about 127,000 MWh annually with a maximum demand of 26,500 kVA. The already implemented energy saving measures decreased the company's energy usage by 5% resulting in a current energy intensity of 1,493ZAR/ton. Further proposed energy efficiency measures included the compressed air system, preheating of the charge material and the reduction of the holding furnaces were analysed. The results of all evaluated measures, namely lighting, load-shifting and maximum demand management were cost effective solutions. Furthermore the recommended energy efficiency measures, namely reduction of compressed air leaks, reduction of holding furnaces as well as preheating of charge material, showed in theoretical calculations a reduction of carbon emissions as well as cost savings. This study offers an insightful view on energy intensity and energy efficiency opportunities in South African foundries, especially the ones operating an induction furnace.
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    Study into the feasibility and design of a renewable energy portfolio for the Klein Constantia Wine
    (2012) Leisegang, Derek Andrew Cecil; Hibberd, Andrew; Bennett, Kevin
    The South African wine industry has seen a growing interest in the field of renewable energy in recent years. This has been due, in part, to rising energy costs a long with increased public and consumer awareness around the issues of global warming and sustainability. This project was conceived in the light of these developments, and centres on an investigation into the feasibility and design of a renewable - energy portfolio for the Klein Constantia Wine Estate, located in the Western Cape. A literature survey was undertaken, shedding light on the common uses of energy on wine farms, renewable energy initiatives within the industry and the technologies available. A case study was then conducted using Klein Constanta Wine Estate as the subject. Physical measurements were taken where possible and, along with a combination of topographical, satellite and local climate data , were used to develop estimates f or the energy - generation potential of the farm's renewable resources and the cost implications thereof. Following this, a qualitative and quantitative analysis was conducted to determine the most favourable technologies from a portfolio design perspective. From these findings, three potential portfolio designs were developed, each covering varying degrees of the farm's energy consumption. Based on the se final designs, it was concluded that there was indeed significant potential for investment in renewable energy at Klein Constantia; and that the farm could more than cover its energy requirements. While the financial returns would be minimal, with relatively long payback - periods, the secondary benefits to the farm were considered to be sufficient to justify the investments. The final decision, however, would likely rest on the weight given to the secondary benefits by the farm owners. It was also determined that, in the case of Klein Constantia, the larger the investment the less secure it would be. This was primarily due to the need for higher - risk and more expensive technology options being required when the energy target was raised. With this in mind a renewable energy portfolio, covering only the farm's electricity use, was found to be the most favourable option available to the farm.
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    The Measurement & Verification of Energy Conservation Measures at a Coal-fired Power Plant
    (2018) Larmour, Richard; Moorlach, Mascha; Bennett, Kevin; Hibberd, Andrew
    The aim of this dissertation was to use Measurement & Verification (M&V) to determine the improvements in net heat rate at a South African coal-fired power plant (CFPP) following an extensive refurbishment programme. The CFPP consisted of multiple subcritical pulverised fuel generating units and the refurbishment programme aimed to improve the overall net heat rate by 1%. The purpose of using M&V is isolate the performance changes attributable to specific energy conservation measures from those changes brought about by other factors, or that would have occurred anyway for other reasons. An extensive literature review was undertaken, firstly into M&V and secondly into CFPP design and performance. The conventionally accepted methods for determining plant performance are the ‘direct method’ in which a measurement boundary is drawn around the entire plant, and the ‘components method’ which evaluates the boiler, the turbine-condenser cycle and the auxiliary loads separately. Caution is drawn to the fact that plant performance may be expressed in many ways depending on how HR is defined and on which coal measurement base is used. The physical factors affecting plant performance were classified as either fixed or variable. Fixed factors included vintage and design, size, condition of the major components (boiler, turbine and condenser), cooling water system type and pollutant controls. Variable factors included ambient conditions, flexibility of operations (such as running at part-load and load cycling) and the characteristics of the coal used including heating value, total moisture, hydrogen, ash, volatile matter, sulphur, hardness & abrasiveness. It is clear from the literature that the language used to describe flexible operations is inadequate and poorly defined. Other factors that may affect the calculated heat rate of a plant include coal weighing, stockpile surveys, length of assessment periods, changes to static stockpiles, measurement boundary selection and other assumptions. The literature review was used as a basis to develop an M&V methodology for the specific CFPP involved in the case study. The energy conservation measures were described in detail as well as constraints regarding availability and resolution of plant data. Although all measurement boundary options were considered, the whole facility approach was chosen (Option C). This approach was mainly motivated by the lack of data available and a high potential for interactive effects. Another reason is the fact that assessments need to capture the overall performance which could include deterioration in one part of the plant and simultaneous upgrades in other parts. The primary data required to find heat rate is the electrical energy use (exported, imported and auxiliary), the mass of coal consumed and the coal higher heating value. The M&V methodology included the development of a baseline adjustment model to adjust for changes in plant load, coal moisture and coal ash content. Ideally the model should have included changes in ambient conditions (temperature and relative humidity) but this was not possible as no ambient data was available and the assessment was done retrospectively. The absence of ambient data was mitigated by stipulating that assessment periods need to consist of a minimum of twelve consecutive months to account for changes in performance due to seasonal effects. The methodology also included a Monte Carlo analysis to quantify the combined uncertainties associated with electrical energy use, coal energy use, coal heating value and the adjustment model itself. The methodology was used to assess the change in net heat rate of the plant used in the case study for two separate twelve month reporting periods. The calculated impacts of the energy conservation measures were not as favourable as originally anticipated. A brief analysis of the results is provided with a discussion of potential reasons for the underperformance. A whole facility approach does not allow the reasons for performance changes to be pinpointed. One possibility is simply that the energy conservation measures had not been implemented as originally planned. An important finding was that the performance changes could not be solely attributed to the exclusion of any independent variables from the baseline adjustment model (e.g. ambient conditions). A more general discussion of the merits, shortcomings and limitations of the methodology is provided as well as some comments on the general interpretation of results. The baseline adjustment model is only applicable to the plant in the case study and is only valid for small changes in the independent variables. When calculating part-load operation, special attention must be given to generating units that have been derated. The application of a single part-load adjustment model to a multi-unit plant is discussed and found to result in conservative reporting. Factors which contribute to uncertainty, but which are unknown include staithe coal level changes, unknown stockpile dynamics, uncalibrated instruments, unrecorded coal movements and inaccuracy of aerial stockpile surveys. The dissertation concludes that the original hypothesis is supported: that a credible M&V methodology may be developed and applied to determine the heat rate improvements resulting from the refurbishment programme at a coal-fired power plant. Recommendations include an upfront agreement on which measurement reporting bases to use (both for heat rate and for coal), selection of a whole facility measurement boundary, a minimum assessment period of twelve months, installation of at least one accurate instrument to measure actual coal consumption (as opposed to coal delivered to the plant and then moved within the plant), sampling of coal, determination of heating value and collection of accurate ambient condition data from the start of the baseline period. Further recommendations are made to reduce uncertainty, determine static factors and to better interpret reported impacts.