Avloppsslam är en restprodukt som uppstår vid rening av avloppsvatten, det innehåller både energi och näringsämnen. Ett av dessa näringsämnen som är en viktig del i livsmedelsproduktion och riskerar att bli en bristvara i framtiden är fosfor. En utredning på uppdrag av regeringen presenterade nyligen ett förslag för slamhantering med begränsad slamspridning och krav på att minst 60 % av all fosfor i avloppsslam ska återvinnas. Återvinning av fosfor ur förbränningsaska är ett alternativ som uppfyller kraven på återvinning. I denna rapport utreds möjligheterna för en fjärrvärmeanläggning med slamförbränning i Umeå. Detta med utgångspunkt från det slam som produceras vid Vakins avloppsreningsverk på Ön och de lokala förutsättningar som finns i Umeå. Utredningen har genomförts genom litteraturstudier, samtal med kunniga personer och termodynamiska jämviktsberäkningar. Slamproduktionen i Umeå är i dagsläget 10 000 ton/år men bedöms öka till upp mot 15 000 ton/år fram till år 2050. Utifrån mängden slam och dess låga värmevärde anses samförbränning vara ett bättre val för en fjärrvärmeanläggning, monoförbränning kan snarare ses som ett alternativ för kvittblivning av slam. Två bränslen som anses intressanta för samförbränning och därför utvärderas närmre i denna rapport är bark och rörflen. Termodynamiska beräkningar visar att en blandning av bark och slam kan förväntas ha en högre asksmältpunkt än en blandning med rörflen och slam. Jämfört med rörflen anses även tillgång och generella driftegenskaper för bark och andra trädbränslen vara mer fördelaktiga. En viss inblandning av rörflen kan däremot ge ett högre värmevärde samt att det kan förbättra växttillgängligheten för fosfor i askan. Den föreslagna bränslemixen med 15 % ts slam innebär att anläggningen kommer att ha en effekt på 18 MW med kontinuerlig drift under tidsperioden september-maj. Bränslemixen riskerar dock att vara för fuktig för att uppnå de temperaturkrav som krävs vid avfallsförbränning, därmed kan torkning av slam eller bark bli nödvändigt. Den panna som föreslås i denna rapport är en rosterpanna med rörlig rost. Valet baseras delvis på att ett antagande om att en stor del av tungmetallerna hamnar i flygaskan vilket kan ge en bottenaska som kan spridas direkt på skogs- eller åkermark. Ekonomin för en samförbränningsanläggning är väldigt beroende av förutsättningarna för fjärrvärmenätet. Baserat på antaganden i denna studie är det i dagsläget mer ekonomiskt lönsamt med en monoförbränningsanläggning. Vid ett ökat behov av fjärrvärmeproduktion kan en samförbränningsanläggning däremot vara ett bättre alternativ.

Forest industries produce large amounts of carbon rich sludges as by-products in their processes. Presently sludge is treated as a poor quality biofuel for co-incineration, some mills treat it solely as a disposal problem. This thesis provides an introduction to production, composition and disposal issues of sludge. It also includes a presentation of strategies for sludge handling. The main concern with energy recovery from sludge is connected to high content of water (50-80%). Mechanical dewatering is an energy efficient method of decreasing the water content. However, there are limitations to how far sludge can be dewatered mechanically. Thermal dewatering is sometimes required to dewater the sludge beyond these limits, in order to obtain a high quality biofuel for incineration and/or thermal gasification. It is often inefficient, from an energy point of view, to incorporate thermal dewatering in the sludge handling strategy. An interesting alternative to thermal processes is anaerobic digestion, which is a biological process used for energy recovery. Advantages with anaerobic digestion include biogas production, efficient treatment of sludge with high content of water and potential for nutrients recovery. The process and the kinetics of anaerobic digestion are presented. The aim of this thesis is to present a method for evaluating different sludge handling strategies from an energy perspective, and to further develop anaerobic digestion as a process for energy recovery from sludge. The thesis is based on two papers. Paper I presents an inclusive approach with focus on energy use and energy recovery in wastewater management, including wastewater treatment and sludge handling. Paper II explores the possibility to enhance biogas production by anaerobic co-digestion of pulp mill sludge with municipal sewage sludge.

As the demand for alternative and renewable sources of energy grows worldwide, it has been argued that small-scale Urban Wind Energy (UWE) could have the potential to provide a significant portion of the electricity demand for urban areas. However there is currently a lack of knowledge surrounding the realisable potential for UWE, especially in the South African context. In order to gain a better understanding of the potential for UWE and the barriers acting against its widespread uptake, it is essential to first quantify the resource potential. This study appraise and evaluate the UWE resource potential at six locations in Cape Town, South Africa in order to gain a solid understanding of the UWE resource potential and thus begin to build the knowledge base around UWE. In order to meet the research objectives, wind data was obtained from the South African Weather Service for six locations in Cape Town at five minute recording intervals for a period of two years. These locations were: The Royal Cape Yacht Club located in the Table Bay harbour, the Astronomical Observatory located in Observatory, and the Kirstenbosch Botanical Gardens located in Kirstenbosch, the Molteno reservoir located in Oranjezicht, the Automatic Weather station located near the Cape Town International Airport as well as the Cape Town Weather Office (WO) station which is also located at the Cape Town International Airport. The data sets are then analysed using a script written in the programming language R in order to quantify the wind energy resource potential of the chosen locations. The wind energy resource potential of each site was combined with four commercially available wind turbines power curves in order to calculate the expected annual energy production values of the various turbines at the each of the locations. Results from this study highlight the significant variability resource potential of the wind regime that occurs between the six locations. The lowest yearly average wind speed was 2.044m/s which was recorded at the Kirstenbosch recording station, while the highest average wind speed was 5.06m/s which was recorded at the WO station. The average of all six stations for the two year period was 3.24m/s. Therefore the WO station had the highest energy potential with a value of 1474 kWh/m²/year and the station with the lowest energy potential was the Kirstenbosch station with a value of 80 kWh/m²/year. Combining these resource potential values with power cures from four commercially available wind turbines yields the Annual Energy Production (AEP) values for the chosen site and wind turbine. These AEP values also varied drastically with the high of 4304 kWh/year being calculated for the SkyStream turbine at the WO station and a low of just 0.66 kWh/year being calculated at the Kirstenbosch station with the Turby turbine. This variability hampers the wide spread uptake of small scale wind power as the results from one area cannot be reliably used to infer the wind resource potential at another nearby site. Out of the six chosen locations in the Cape Town area, three of the locations (Royal Cape Yacht Club, the Automatic Weather Station (AWS), and the Cape Town Weather Office (WO)) showed potential for the installation of a small scale wind turbine, with the Horizontal Axis Wind Turbines (HAWTs) performing better than the Vertical Axis Wind Turbines (VAWTs). This is possibly due to the lower cut in wind speeds of the HAWTs compared to the cut in wind speeds for the VAWTs. The conclusions of this study show that the UWE resource potential in Cape Town is characterised by high resource variability between the various locations. Three of the six locations that were evaluated showed potential for UWE installations. This study has identified the major challenges associated with UWE to be the turbulence, lower hub heights of the wind turbines (this study used 20m as the standard hub height), and variability of the wind regime between locations.

Access to clean, modern energy services is a necessity for sustainable development. The UN Sustainable Development Goals and SE4ALL program commit to the provision of universal access to modern energy services by 2030. However, the latest available figures estimate that 1.1 billion people are living without access to electricity, with over 55% living in Sub-Saharan Africa. Furthermore, 85% live in rural areas, often with challenging terrain, low income and population density; or in countries with severe underinvestment in electricity infrastructure making grid extension unrealistic. Recently, improvements in technology, cost efficiency and new business models have made mini-grids which combine multiple energy technologies in hybrid systems one of the most promising alternatives for electrification off the grid. The International Energy Agency has estimated that up to 350,000 new mini-grids will be required to reach universal access goals by 2030. Given the intermittent and location-dependent nature of renewable energy sources, the evolving costs and performance characteristics of individual technologies, and the characteristics of interacting technologies, detailed system simulation and demand modelling is required to determine the cost optimal combinations of technologies for each-and-every potential mini-grid site. Adding to this are the practical details on the ground such as community electricity demand profiles and distances to the grid or fuel sources, as well asthe social and political contexts,such as unknown energy demand uptake or technology acceptance, national electricity system expansion plans and subsidies or taxes, among others. These can all have significant impacts in deciding the applicability of a mini-grid within that context. The scope of the research and modelling framework presented focuses primarily on meeting the specific energy needs in the sub-Saharan African context. Thus, in being transparent, utilizing freely available software and data as well as aiming to be reproducible, scalable and customizable; the model aims to be fully flexible, staying relevant to other unique contexts and useful in answering unknown future research questions. The techno-economic model implementation presented in this paper simulates hourly mini-grid operation using meteorological data, demand profiles, technology capabilities, and costing data to determine the optimal component sizing of hybrid mini-grids appropriate for rural electrification. The results demonstrate the location, renewable resource, technology cost and performance dependencies on system sizing. The model is applied for the investigation of 15 hypothetical mini-grids sites in different regions of South Africa to validate and demonstrate the model’s capabilities. The effect of technology hybridization and future technology cost reductions on the expected cost of energy and the optimal technology configurations are demonstrated. The modelling results also showed that the combination of hydrogen fuel cell and electrolysers was not an economical energy storage with present day technology costs and performance. Thereafter, the model was used to determine an approximate fuel cell and electrolyser cost target curve up to the year 2030. Ultimately, any research efforts through the application of the model, building on the presented framework, are intended to bridge the science-policy boundary and give credible insight for energy and electrification policies, as well as identifying high impact focus areas for ongoing further research.

Desalination technologies are being used to augment access to safe drinking water around the world. Nonetheless, most of these technologies are energy-intensive and driven by fossil fuels which emit greenhouse gases into the atmosphere, thereby contributing to climate change. Additionally, fossil fuels are non-renewable sources of energy and the exhaustion of such reserves can cause a threat to energy security. Consequently, exploitation of sustainable sources of energy for the desalination process has attracted a lot of attention. One such strategy is the use of a solar still which utilises solar energy to produce fresh water from saline or brackish water. However, the major drawback of a solar still lies in its low productivity. Many studies have investigated means of increasing the productivity of a solar still. One such technique which has recently been studied is to disperse nanoparticles into the impure water inside the basin of a solar still in order to obtain a nanofluid with enhanced optical and heat transfer characteristics. Since this is a relatively new topic, very few numerical studies on solar stills with nanofluids are available. Moreover, based on a literature review, no study examining the effect of nanoparticle size on the productivity of solar stills, and on the economic and environmental performance of solar stills was found. Additionally, the few available numerical studies on solar stills with nanofluids have not taken into account the view factor in the computation of the internal radiative heat transfer coefficient. Therefore, the aim of this study was to investigate both numerically and experimentally the effect of nanoparticle size on the performance of solar stills. Mathematical models with the view factor (Model 1) and without the view factor (Model 2) were developed for single slope solar stills, and a code was written in MATLAB software to solve a system of equations iteratively. Calculations were performed using climatic data from Stellenbosch (latitude 33.93°S, longitude 18.86°E) and University of Cape Town (latitude 33.96°S, longitude 18.46°E), South Africa, in order to evaluate the performance of solar stills with varying nanoparticle sizes. For the experimental phase, four identical solar stills were designed and built, and they were first tested with water only (base fluid) in all of them to test their performance and for calibration purposes. An Analysis of Variance (ANOVA) test was conducted on the experimental data collected from this first test. Subsequently, nanofluids containing aluminium oxide (Al2O3) nanoparticles of size 10 nm, 50 nm and 100 nm were used in three of the solar stills, with the other solar still containing the base fluid only. All the experiments were conducted at the University of Cape Town. The mathematical models were then validated using experimental data. Simulations in MATLAB based on Stellenbosch climatic data showed that for the month of January, which is a summer month in South Africa, the productivity of the solar still with the 10 nm, 50 nm and 100 nm Al2O3 nanoparticles was 9.01%, 8.94% and 8.89%, respectively higher than the productivity of the solar still with the base fluid only. On the other hand, for the month of July, which is a winter month in South Africa, the average productivity of the solar still with the 10 nm, 50 nm and 100 nm Al2O3 nanoparticles was 1.31%, 1.23% and 1.19%, respectively higher than the productivity of the solar still with base fluid only. In terms of the economic analysis, the simulations in MATLAB based on annual climatic data from Stellenbosch revealed that the cost of distilled water obtained from the solar still with the 10 nm, 50 nm and 100 nm Al2O3 nanoparticles was 10.42%, 6.21% and 3.51%, respectively higher than the cost of water obtained from the solar still with the base fluid only. Additionally, the payback period for the solar still with the 10 nm, 50 nm and 100 nm Al2O3 nanoparticles was 13.32%, 7.86% and 4.37%, respectively higher than the payback period for the solar still with the base fluid only. In terms of the environmental performance, the amount of carbon dioxide equivalent (CO2 equivalent) mitigated by the solar still with the 10 nm, 50 nm and 100 nm Al2O3 nanoparticles was 6.18%, 6.11% and 6.06%, respectively higher than the amount of CO2 equivalent mitigated by the solar still with the base fluid only. For the experimental phase, the ANOVA test based on the first set of experimental data (with base fluid only in all four solar stills) gave a probability-value (P-value) of 1.00. Moreover, experimental data collected from solar stills with base fluid and nanofluids revealed that the productivity of the solar still with nanoparticles of size 10 nm and 50 nm was 26.46% and 1.46%, respectively higher than the productivity of the solar still with base fluid only. On the other hand, the productivity of the solar still with nanoparticles of size 100 nm was 9.38% lower than that of the solar still with base fluid only. Furthermore, the root mean square error (RMSE) for the solar stills with nanofluids for Model 1 and Model 2 was 22.02% and 36.03%, respectively. It was confirmed that the performance of the calibrated solar stills was not significantly different. Moreover, the enhancement in the productivity of a solar still with nanofluids is much more distinct in summer than in winter. It was also demonstrated that the productivity of a solar still decreases with increasing nanoparticle size. Additionally, it was established that the cost of distilled water, the payback period and the amount of mitigated CO2 equivalent decrease with increasing nanoparticle size. Theoretically, the distillate yield and environmental performance of a solar still with nanofluids were marginally sensitive to the nanoparticle size while the cost of distilled water and payback period were significantly affected by the nanoparticle size. The effect of nanoparticle size on distillate yield was experimentally significant. Finally, it was demonstrated that the inclusion of the view factor improves the accuracy of modelling of solar stills with nanofluids.

This paper investigates, in the context of Cape Town the emission reduction potential (ERP) of energy from biogas and related cost. Two project-scale models and a city-scale model were developed. Substrates for project model 1 were organic fraction of municipal solid waste (OFMSW) and primary sludge (PS) from sewage works. Project model 2 considered waste paper sludge (WPS) and PS. For the city-scale model, substrates for project model 1 were extended to include total amounts of OFMSW and PS generated in Cape Town. Financial results show that at the REFIT tariff model 1 would have a higher internal rate of return (20.5%) than model 2 (5.6%). The landfill ERP of the project-scale models is 98 600 CO2 equivalent tons per year, corresponding to a weighted average capital investment of R372 per CO2 equivalent ton saved in year 1. The results for the city-scale model indicate that a landfill ERP of 458 000 CO2 equivalent tons per year can be expected at an investment cost of R287 per CO2 equivalent ton saved in year 1. Energy emissions from fossil fuels at city-scale are most effectively mitigated if coal rather than other fossil fuel based power and heat generation are replaced.

Includes bibliographical references. / South Africa has its fair share in the global greenhouse gas (GHG) emissions, with recorded 2010 emissions per capita of 10tons/year. This is caused by the energy supply of the country which relies heavily on fossil fuels to drive its energy intensive economy. If this continues under “business as usual”, consequences like water and food shortage may be exacerbated. The waste sector has a share of 3 in national GHG emissions. These are caused by methane from biogas produced through anaerobic digestion of organic waste. The objective of this study was to assess the potential contribution that can be achieved in reducing the national GHG emissions by converting waste emissions into useful energy or capturing and destroying them. Three waste resources were investigated because of their abundance in the country: municipal solid waste, municipal wastewater and livestock manure. The national picture of municipal waste was extrapolated from the waste data available in 7 metros in the country (City of Cape Town, Johannesburg, Tshwane, Ekurhuleni, EThekwini, Nelson Mandela Bay, and Buffalo City municipalities). Projected GDP and population growths were used as indicators for extrapolating the national data. The total national organic waste derived from these waste categories was used to estimate their emission share in national GHG emissions and biogas generation in terms of methane production from each waste type. This was forecasted from 2010 to 2025. The methane gas production was optimised by assuming different waste combinations like: municipal solid waste and wastewater, wastewater and livestock manure, and remaining wastewater. In addition, the possible amount of electricity or heat produced from this biogas was estimated. This useful energy was used to evaluate the emission reduction potential (ERP) in the national GHG emissions of the country under “growth without constraints”. All these computations were performed by using MS Excel software. It was found that the total organic waste predicted during this period varied from 12 to 17Mton, with the waste emissions share being about 2 of the national GHG emission. Methane generated from this waste was about 644-1075Mm3 while the total optimal methane generated from these waste combinations was estimated to be 1770- 2650Mm3. In addition, 673-1123GWh of electricity and 1255-2150GWh of heat could be produced (without optimization) from methane over the same period of the forecast. For optimal methane production, the possible useful energy was estimated to be 1362-2037GWh of electricity and 2894- 4362GWh of heat. The ERP of methane capture and conversion to useful energy was about 2.1- 2.5. It is concluded that a) capturing and utilisation of methane gas from waste contributes to the reduction of the GHG emissions, b) optimisation of biogas production from waste increase methane yield and therefore useful energy, and c) the best contribution of biogas in climate change mitigation in South Africa would come from the optimal production of methane from waste.

Includes bibliographical references. / 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.

Geoenergi är ett alternativ som allt fler aktörer på marknaden väljer när det kommer till att kyla eller värma fastigheter men än så länge är de flesta anläggningar som finns i Sverige småskaliga. Gällivare sjukhus använder sig i dag av fjärrvärme och det här examensarbetet gör en förstudie för att konvertera helt eller delvis till bergvärme. Fjärrvärmekostnaden i Gällivare kommun är en av de högsta i Norrbotten och har varken ökat eller minskat de senaste åren. Medeltemperaturen i Gällivare är låg vilket betyder att sjukhuset har ett högt värmebehov men med ett lägre kylbehov. Denna studie analyserar tre tänkbara scenarier för konverteringen där anläggningen ska täcka värme och kylbehovet för sjukhuset. För att kon_gurera bergvärmeanläggningen efter behovet används Earth Energy Designer 4.1 och Microsoft Excel. De tre scenarier som studerats täcker 100% av kylbehovet och 100% av värmebehovet för Scenarie 1, 50% av värmebehovet för Scenarie 2a och 40% av värmebehovet för Scenarie 2b. För att beräkna kylbehovet analyserades bland annat utomhustemperaturen i Gällivare med data från SMHI. Det gjordes även en simulering av sjukhuset i IDA-ICE för att uppskatta kylbehovet för ventilation och människors värmestrålning. En jämförelse mellan de olika scenarierna gjordes tillsammans med en livscykelkostnad för anläggningarna. Livscykelkostnadsanalysen beräknades utifrån en livslängd på 20 år. Utöver detta beräknades miljöpåverkan i form av koldioxidutsläpp för konverteringen mellan de olika scenarierna under den beräknade livslängden. Storlekarna på anläggningarna varierade både på djup och i antal borrhål vilket avspeglade sig i resultatet. Investeringskostnaderna för anläggningarna varierade mellan 18 071 tkr för Scenarie 2b som täcker 40% av värmebehovet och 53 272 tkr för Scenarie 1 som täcker 100%. Scenarie 2b visar sig vara mest lönsam med en återbetalningstid på 15 år medan Scenarie 1 och 2a har en återbetalningstid på över 20 år. Resultatet från koldioxidberäkningarna visar däremot att Scenarie 1 är det bästa alternativet ur en miljöaspekt med ett minskat koldioxidutsläpp på 42 739 ton under den tekniska livslängden. / Geothermal energy is an alternative that more and more companies choose when it comes to cooling and heating properties, but so far most of the geothermal facilities in Sweden are small-scale. The hospital in Gällivare use district heating and this master thesis is a pilot study to convert from district heating to geothermal energy. The cost for the district heating in Gällivare is one of the highest in Norrbotten and has not increased or decreased the past few years. The mean temperature in Gällivare is low which means that the hospital has a high heat demand but a low cooling requirement. This pilot study analyses three scenarios to convert to geothermal heating system with the possibility to cover the cooling requirement as well. These scenarios are configured to cover 100% of the cooling requirement but different heating demands of 100% for Scenario 1, 50% for Scenario 2a and 40% for Scenario 2b. To cover this demand, Earth Energy Designer 4.1 and Microsoft Excel are used to configure the heating system and to do the comparison between the scenarios. The cooling requirement is calculated based on the outside temperature in Gällivare and the equipment used in the hospital. A simulation was made in IDA-ICE to analyze the cooling requirement for the ventilation and for the people inside the hospital. A comparison between the scenarios was made using the LCC (Life Cycle Cost) method. The LCC was made with a 20 years lifetime on the heating system. In addition, the environmental impact in the form of carbon dioxide emissions is calculated for the different scenarios during the estimated lifespan. The sizes on the heating systems in the different scenarios varies in both the number of boreholes and the depth on the boreholes, which was reflected in the result. Investment cost for the heating system varies between 18 071 tkr for Scenario 2b which covers 40% of the demand and 53 272 tkr for Scenario 1 which covers 100 %. Scenario 2b proves to be the most profitable solution with a payback time of 15 years while Scenario 1 and 2a got a payback time of over 20 years. From an environmental aspect Scenario 1 is the best option with a decreased usage of carbon dioxide of 42 739 tons over 20 years.

This is a study on how the profitability of a photovoltaic systems owned by small house residents could be affected by the introduction of power-based tariffs in the regions around Mälaren, Sweden. This tariff is based on the customers highest power usage per month. During the time of this study, the most common type of tariff that distribution system operators use is based on a summation of the amount of electricity used by that specific customer. More recently, companies have started to battle the shortage of net capacity and lack power in the Swedish grid. One of the methods used to fight this problem is to introduce another type of tariff with the intent to make customers more aware of their behavior related to electricity usage. By calculating the contribution, the photovoltaic system has in lowering power peaks, as well as using a LCOE-method and payback period, the overall profitability can be evaluated. An interview is conducted, to further develop an understanding on how the industry believes the profitability of a photovoltaic system might be affected with the introduction of power-based tariffs. The results show that the profitability of the photovoltaic system owned by the small house residents included in this study, is negatively affected by the introduction of power- based tariffs. The photovoltaic system can sometime help in reducing power peaks; however, the overall reduction is not sufficient to improve the profitability of the photovoltaic system. The value of self-consumption decreases with a power-based tariff compared to a tariff based on energy. A response from the industry states that power-based tariffs can be a solution to complications regarding todays power grid. The industry also states that the introduction of power-based tariffs could lead to a more just charge of power grid usage by the customer. Energy storage could assist the photovoltaic system to further decrease power peaks and therefore make a good complement to the system.