PhD (Physics) / Department of Physics / The knowledge of solar radiation in this dispensation is crucial. The lack of grid lines in the remote rural areas of South Africa necessitates the use of solar energy as an alternative energy resource. Solar radiation data is one of the primary factors considered for the installation of renewable energy devices and they are very useful for solar technology designers and engineers. In some developing countries, estimation of solar radiation becomes a challenge due to the lack of weather data. This scenario is also applicable to South Africa (SA) wherein there are limited weather stations and hence there is a dire need of estimating the global solar radiation data for all climatic regions. Using a five year global solar radiation (𝐻) and bright sunshine (𝑆) data from the Agricultural Research Council (ARC) and South African Weather Service (SAWS) in SA, linear Angstrom – Prescott solar empirical model was used to determine regression coefficients. MATLAB interface was used whereby the linear regression plots were drawn. Annual empirical coefficients of 22 stations were determined and later the provincial values. The range of the regression coefficients, a and b were 0.216 – 0.301 and 0.381 – 0.512 respectively. The 2006 estimated global solar radiation per station in a province calculated from the modified models were compared with the observed and statistically tested. The root mean square errors were less than 0.600 MJm−2day−1 while the correlation relation ranged from 0.782 – 0.986 MJm−2day−1. The results showed the regression coefficients performed well in terms of prediction accuracy. / NRF

Käppala wastewater treatment plant (WWTP) has, during a few years, observed an increase in organic loading rate (OLR) in the mesophilic anaerobic digester R100, due to an increased load to the WWTP. The digestion of primary sludge at Käppala WWTP is today high loaded, with a high organic loading rate (OLR) and low hydraulic retention time (HRT). This study aims to evaluate the effect of the maximum OLR and the minimum HRT for the anaerobic digestion of sewage sludge and to investigate further actions that can be taken into consideration in case of process problems in the digestion. The study consists of (a) a practical laboratory experiment of 6 pilot-scale reactors to investigate how the process stability is affected when the OLR increases and the HRT decreases. (b) A mass balance calculation based on the energy potential in the feeding sludge and the digested sludge. (c) A study of the filterability of the digested sludge. (d) The construction of a forecasting model in Excel, to predict when digester R100 will reach its maximum OLR and minimum HRT. The result of the study shows that the maximum OLR for Käppala conditions is 4.9 g VS dm-3 d-1, meaning that R100 will reach its maximum organic load around the year 2031. An OLR of 4.5-4.9 and an HRT of 12 days is optimal for R100, according to the present study. Keeping the anaerobic digestion process in balance is vital when it comes to the outcome of energy in the anaerobic digestion process. Pushing the process to produce more gas can become counterproductive since a high OLR can lead to process imbalance, which in turn leads to low biogas production. Imbalance in the digestion process can occur fast; therefore, the margin for overload in the anaerobic digestion process must be significant. The methane concentration in the converted biogas and the pH level in the reactor are the best stability parameters for the conditions at Käppala. Ammonia is the less efficient stability parameter since it did not predict or detect any instability during the experimental process. Furthermore, the OLR and HRT have a significant impact on the needed quantity for dewatering polymer. The higher digestion of organic material in the sludge, the bigger the need for the polymer to take care of the rest material.

Käppala wastewater treatment plant (WWTP) has, during a few years, observed an increase in organic loading rate (OLR) in the mesophilic anaerobic digester R100, due to an increased load to the WWTP. The digestion of primary sludge at Käppala WWTP is today high loaded, with a high organic loading rate (OLR) and low hydraulic retention time (HRT). This study aims to evaluate the effect of the maximum OLR and the minimum HRT for the anaerobic digestion of sewage sludge and to investigate further actions that can be taken into consideration in case of process problems in the digestion. The study consists of (a) a practical laboratory experiment of 6 pilot-scale reactors to investigate how the process stability is affected when the OLR increases and the HRT decreases. (b) A mass balance calculation based on the energy potential in the feeding sludge and the digested sludge. (c) A study of the filterability of the digested sludge. (d) The construction of a forecasting model in Excel, to predict when digester R100 will reach its maximum OLR and minimum HRT. The result of the study shows that the maximum OLR for Käppala conditions is 4.9 g VS dm-3 d-1, meaning that R100 will reach its maximum organic load around the year 2031. An OLR of 4.5-4.9 and an HRT of 12 days is optimal for R100, according to the present study. Keeping the anaerobic digestion process in balance is vital when it comes to the outcome of energy in the anaerobic digestion process. Pushing the process to produce more gas can become counterproductive since a high OLR can lead to process imbalance, which in turn leads to low biogas production. Imbalance in the digestion process can occur fast; therefore, the margin for overload in the anaerobic digestion process must be significant. The methane concentration in the converted biogas and the pH level in the reactor are the best stability parameters for the conditions at Käppala. Ammonia is the less efficient stability parameter since it did not predict or detect any instability during the experimental process. Furthermore, the OLR and HRT have a significant impact on the needed quantity for dewatering polymer. The higher digestion of organic material in the sludge, the bigger the need for the polymer to take care of the rest material.

Introduction: The world is facing an economic crisis that has led to high energy prices in the EU. These high energy prices have been a contributing factor to the challenging economic situation in Sweden, affecting businesses, industries, and households. EU countries have limited access to energy and rely mostly on imports. The key objective is to reduce these costs through the utilization of renewable energy resources. Geothermal ventilation, in particular, is an efficient and promising source. However, this system has not yet been implemented in Sweden. The aim of this study is to investigate and analyze the effectiveness of horizontal ground geothermal ventilation systems in the context of Swedish conditions.Method: This study includes quantitative and qualitative data from a case study. Data collection involved literature study, interviews with various stakeholders, and simulations using Ansys software to analyze air flows and temperature conditions.Results: This section presents the results of a comprehensive study on basic geothermal ventilation in villas, carried out in accordance with Swedish environmental regulations. Interviews with representatives from ventilation companies and Jönköping municipality showed mixed opinions about the system's potential. While some expressed interest and approval due to energy savings and environmental adaptation, others had concerns about profitability and cost-effectiveness. Testing the system's efficiency using thermal exchange simulation software showed lower-than-expectedresults, indicating the need for further improvements. However, despite its lower efficiency, the geothermal ventilation system was still considered an environmentally friendly alternative to conventional methods, helping to reduce the environmental impact of the construction industry.Analysis: Ground geothermal ventilation system meets Swedish environmental standards and contributes to energy savings in new buildings. Although the system meets the standards, further improvements are needed to increase efficiency. Requirements and prerequisites include the right insulation classes and specially manufactured ground pipes. Implementation in villas can be challenging due to costs and heat delivery. Despite this, the system improves indoor air quality and reduces energy consumption, even if the temperature differences may be smaller than expected.Discussion: In this chapter, the results and conclusions from the study are discussed. Despite limited research on the subject, the study shows that shallow geothermal ventilation has potential, but there are challenges and limitations for implementation in Swedish villas. The method choice of literature review and qualitative interviews was appropriate to achieve the purpose, but more participants and research are needed to increase validity and reliability. Recommendations are given for further research in the area.