With increasing popularity of indoor farming, more and more home growers are faced with sub-optimal lighting conditions in northern countries or poorly lit windows. We have designed and built a proof-of-concept system capable of reducing electricity cost and CO2 footprint of the electricity used for consumer grade grow lights without adversely impacting the grow cycle of the plant. Our system provides optimal grow light conditions for a given plant while using forecasts and live grid data from the ENTSO-E transparency platform to automatically use or store electricity during low-cost hours and avoid using grid electricity during high-cost hours, but can also be configured to prioritize electricity use when the available grid power’s carbon intensity is low. The system, consisting of a server and an embedded control unit, was designed and implemented according to Nunamaker and Chen’s five-step iterative systems development research method and later evaluated by simulating the system for 14 days using real world sunlight and grid data. The results of the simulation show a significant reduction in both spending and carbon emissions related to electricity use, with figures of 73% and 28%, respectively. However, when accounting for life-cycle cost and emissions from the battery, the prototype in its current configuration is neither profitable nor a net positive for the environment. With changes to battery type and taking advantage of economies of scale, a future version could be economically viable, but to be environmentally sustainable, further advances in eco-friendly battery production are needed.

Background: Electricity tariffs charged by Eskom have sharply increased over the past three years, with a 25% annual increase approved by Nersa until April 2012. There is no indication on what to expect in the future with regard to electricity tariffs. Many South Africans are searching for ways to save on their monthly electricity bills by seeking out alternative water heating systems. Solar geysers became a popular investment option, but this might not be the best options available on the market. Purpose: The purpose of this study is to determine the most financially viable investment option in order to reduce electricity cost when it comes to water heating systems for use in households. This is done by comparing the capital expenditure and operational cost needed with the financial benefits generated by the investment, taking into consideration the size of the household. Design and method: A literature study was done on the different alternative water heating systems in order to obtain a better understanding of how these systems operate and what savings they can generate. Different investment appraisals were identified and a literature review was performed in order to identify the most appropriate investment appraisals for the purpose of this study. It was found that the net present value, equivalent annual annuity, internal rate of return, modified internal rate of return, accounting rate of return, discounted payback period and the economic value added were the best investment appraisal methods to use for the purpose of this study. Findings and conclusion: It was found that the five investment options identified in the literature review would all, to some extent, be financially viable to implement within households with high as well as low volume hot water consumption. All the investment appraisals gave positive outcomes. The conclusion was made that a saving will be generated on the monthly electricity bill no matter what alternative water heating system were to be installed in the place of a conventional geyser. Recommendations: It is recommended that a household with low volume hot water consumption should install a time switch as this investment option renders the highest IRR, MIRR, ARR and discounted payback period. The second best investment option for a household with low volume hot water consumption is a heat pump and the third best option is a gas geyser. For a household with high volume hot water consumption, the best investment options is again a time switch, as this renders the best IRR, MIRR, ARR and discounted payback period. The second best investment option is a heat pump, with a gas geyser as the third best investment option. Value of the research: This study focuses on five alternative water heating systems for a household within South Africa in times where electricity charges sharply increase. The financial viability of each of the alternatives is determined through various investment appraisals and the best option can be identified by comparing the outcomes of the alternatives. Furthermore, each individual is able to determine the viability of the alternatives by using the Excel model attached to this study and by inputting his/her own variables, where applicable. Research limitation: Limited literature was available on the different alternative water heating systems. No indication could be found of the maintenance cost of the different water heating systems. Assumptions had to be made with regard to households, although no two households are the same. Areas for further research: The same study could be performed, but with the focus on small businesses and large organisations. Furthermore, a study could be performed to determine the appropriate discount rate for individuals as well as the maintenance cost for water heating systems. / Thesis (MCom (Management Accountancy))--North-West University, Potchefstroom Campus, 2012

Background: Electricity tariffs charged by Eskom have sharply increased over the past three years, with a 25% annual increase approved by Nersa until April 2012. There is no indication on what to expect in the future with regard to electricity tariffs. Many South Africans are searching for ways to save on their monthly electricity bills by seeking out alternative water heating systems. Solar geysers became a popular investment option, but this might not be the best options available on the market. Purpose: The purpose of this study is to determine the most financially viable investment option in order to reduce electricity cost when it comes to water heating systems for use in households. This is done by comparing the capital expenditure and operational cost needed with the financial benefits generated by the investment, taking into consideration the size of the household. Design and method: A literature study was done on the different alternative water heating systems in order to obtain a better understanding of how these systems operate and what savings they can generate. Different investment appraisals were identified and a literature review was performed in order to identify the most appropriate investment appraisals for the purpose of this study. It was found that the net present value, equivalent annual annuity, internal rate of return, modified internal rate of return, accounting rate of return, discounted payback period and the economic value added were the best investment appraisal methods to use for the purpose of this study. Findings and conclusion: It was found that the five investment options identified in the literature review would all, to some extent, be financially viable to implement within households with high as well as low volume hot water consumption. All the investment appraisals gave positive outcomes. The conclusion was made that a saving will be generated on the monthly electricity bill no matter what alternative water heating system were to be installed in the place of a conventional geyser. Recommendations: It is recommended that a household with low volume hot water consumption should install a time switch as this investment option renders the highest IRR, MIRR, ARR and discounted payback period. The second best investment option for a household with low volume hot water consumption is a heat pump and the third best option is a gas geyser. For a household with high volume hot water consumption, the best investment options is again a time switch, as this renders the best IRR, MIRR, ARR and discounted payback period. The second best investment option is a heat pump, with a gas geyser as the third best investment option. Value of the research: This study focuses on five alternative water heating systems for a household within South Africa in times where electricity charges sharply increase. The financial viability of each of the alternatives is determined through various investment appraisals and the best option can be identified by comparing the outcomes of the alternatives. Furthermore, each individual is able to determine the viability of the alternatives by using the Excel model attached to this study and by inputting his/her own variables, where applicable. Research limitation: Limited literature was available on the different alternative water heating systems. No indication could be found of the maintenance cost of the different water heating systems. Assumptions had to be made with regard to households, although no two households are the same. Areas for further research: The same study could be performed, but with the focus on small businesses and large organisations. Furthermore, a study could be performed to determine the appropriate discount rate for individuals as well as the maintenance cost for water heating systems. / Thesis (MCom (Management Accountancy))--North-West University, Potchefstroom Campus, 2012

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Central receiver power plants generate renewable electricity by exploiting the energy provided by the sun. The conditions experienced in the Northern Cape region of South Africa provide the ideal conditions for the development of these plants. Without a storage medium these plants have capacity factors in the range of 25-30%. The inclusion of a thermal energy storage medium provides the ability to increase the capacity factors of these plants. Although storage increases the costs, it results in better utilisation of the power block and a decrease in the levelised electricity cost (LEC). Eskom intends building a 100MWe central receiver dry cooled power plant in the Upington region. This research identifies the appropriate storage medium and ideal storage capacity to achieve the lowest LEC. A literature survey was performed to identify the different methods of storage that are available. The different storage methods were evaluated and the best storage medium for a central receiver power plant based on the developments of the various storage technologies was identified. To determine the costs associated with a central receiver power plant, data published by NREL was used. Different plant parameters were required to evaluate the costs. A power plant model based on efficiencies and energy balances was created to determine the required plant parameters. It provided the ability to determine the effect of changing different plant parameters on the LEC and estimate the plant output. The power block parameters were initially varied to determine the most efficient power block configuration. Once the most efficient power block configuration was identified the solar field and storage parameters were varied to determine the plant configuration which resulted in the lowest LEC. The most efficient power block configuration of 0.4206 was found for a system comprising of six feedwater heaters with the feedwater temperature of 230°C, main steam pressure 140 bar and an exit steam generator salt temperature of 290°C. A solar multiple of 3.0 with 16 hours of storage resulted in a LEC of R1.41/kWh with no system constraints. A capacity factor constraint of 60% resulted in a solar multiple of 1.8 with 8 hours of storage and a LEC of R1.78/kWh. / AFRIKAANSE OPSOMMING: Sonkragaanlegte met sentrale ontvangers wek hernubare elektrisiteit op deur sonenergie te ontgin. Die klimaat in die Noord Kaap-streek van Suid-Afrika is ideaal vir die oprigting van hierdie aanlegte. Sonder ’n bergingsmedium is die kapasiteitsfaktore van sulke aanlegte ongeveer 25-30%. Met die insluiting van ’n bergingsmedium vir termiese energie kan die kapasiteitsfaktore egter verhoog word. Hoewel berging aanlegkoste verhoog, lei dit terselfdertyd tot beter aanwending van die kragblok en ’n afname in die konstante eenheidskoste van elektrisiteit (LEC). Eskom beplan om ’n droogverkoelde kragaanleg van 100 MW met ’n sentrale ontvanger in die Upington-streek op te rig. Hierdie navorsing was dus daarop toegespits om die mees geskikte bergingsmedium en ideale bergingskapasiteit te bepaal om die laagste moontlike LEC uit die aanleg te verkry. ’n Literatuurstudie is onderneem om die verskeie beskikbare bergingsmetodes te bestudeer. Die verskillende metodes is beoordeel, waarna die beste bergingsmedium vir ’n kragaanleg met ’n sentrale ontvanger op grond van die ontwikkelings in die verskillende bergingstegnologieë bepaal is. Om die koste van ’n kragaanleg met ’n sentrale ontvanger te bepaal, is gepubliseerde data van die Amerikaanse Nasionale Laboratorium vir Hernubare Energie (NREL) gebruik. Verskillende aanlegparameters was egter nodig om die koste te beoordeel. Dié parameters is gevolglik bepaal deur ’n kragaanlegmodel op grond van doeltreffendheidsfaktore en energiebalanse te skep. Sodoende kon vasgestel word watter uitwerking veranderinge in die verskillende parameters op die LEC sou hê, en kon die aanleguitset geraam word. Die kragblokparameters is aanvanklik afgewissel om die doeltreffendste kragbloksamestel te bepaal. Nadat dít bepaal is, is die sonenergieveld en bergingsparameters weer afgewissel om vas te stel watter aanlegsamestel die laagste LEC tot gevolg sou hê. Die beste termiese benuttingsgraad is behaal vir ʼn stoom siklus met ses water verhitters en ʼn water temperatuur van 230 °C by die ketel se inlaat, ʼn stoom druk van 140 bar, en sout uitlaat temperatuur van 290 °C. ʼn Vermenigvuldigingsfaktor van drie vir die heliostaat veld, en 16 uur termiese energie storing gee ʼn opwekkingskoste van R 1.41/kW/h indien daar geen beperkings op die grootte of koste van die stelsel geplaas word nie. Indien die kapitaal uitgawe ʼn perk van 60 % op die kapasitiet van die stelsel plaas, verander die optimale ontwerpspunt na ʼn vermenigvuldigingsfaktor van 1.8, en die termiese stoorkapasitiet verlaag na 8 uur. In hierdie geval is die opwekkingskoste R 1.78/kWh.

The electricity cost is one of the largest components of operating costs on a belt conveyor system. This dissertation introduces a unique Conveyor Electricity Cost Efficiency Audit Methodology (CECEAM). In the CECEAM the conveyor system is evaluated from a high to detail level in order to identify opportunities to improve electricity costs. The CECEAM includes methodologies and tools developed to analyze not only the conveyor belt alone, but also the materials handling system as a whole. The outline of the dissertation is structured as follows: Chapter 1 includes the background and problem identification by means of a literature study. The main objective, as well as specific objectives, is defined in this chapter. In chapter 2, the CECEAM is introduced and an overview of the total methodology is discussed. The data acquisition part of the CECEAM; documentation, personnel, walk, technical audit as well as the conveyor database is discussed in chapter 3. Chapter 4 concentrates on the Conveyor Energy Conversion Model (CECM) and the verification thereof. The Integrated Conveyor Energy Model (ICEM) methodology is introduced (in chapter 5) and the economic evaluation concepts and energy management basics needed in the CECEAM are covered. Chapter 6 covers a CECEAM case study where the practical application of the CECEAM is illustrated with ICEM simulations, opportunity identification and recommendations. The conclusion and recommendations for further studies is proposed in chapter 7. / Dissertation (MSc (Electrical Engineering))--University of Pretoria, 2007. / Electrical, Electronic and Computer Engineering / unrestricted