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Geothermal energy is a renewable resource and is attracting increasing attention for heating but also for cooling of domestic and commercial buildings in warm climates. Successful utilization of geothermal energy requires knowledge of the geothermal properties of the ground. In Cyprus only very limited research has been carried out to-date on the use of ground source heat pumps, and information is needed to enable engineers to size correctly Ground Heat Exchangers (GHE) for Ground Source Heat Pump applications. To address this, the main objective of the research presented in this thesis was to investigate the thermal properties of the ground at a number of locations in Cyprus and use the results to develop data and easy to use tools to enable engineers and researchers to evaluate the potential and design Ground Heat Exchangers (GHEs) for specific locations and thermal loads. The research involved an extended geological sampling on the island and measurements of the thermal properties of 148 ground samples in the laboratory in their dry and water saturated states. Thermal conductivity values for dry samples were found to be in the range between 0.4 and 4.2 W m-1 K-1, thermal diffusivity values between 0.3 and 1.910-6 m2 s-1 and specific heat capacity between 0.5 and 1.5 J K-1 kg-1. Results also showed thermal conductivity and thermal diffusivity to increase with water content for most of the ground samples investigated. To understand and visualize all measured data, Geographic Information System (GIS) software was used to generate maps of ground density, thermal conductivity, and thermal diffusivity. From the maps, the Troodos Ophiolite terrane which dominates the central part of Cyprus, was found to offer the best thermal properties for the utilization of geothermal energy on the Island. Geothermal modeling was carried out to investigate the effect of (a) summer and winter mode of operation, (b) ground temperature variation with depth to consider the effects of daily and seasonal ambient temperature variations on ground temperature, (c) borehole radius, (d) borehole grout properties, (e) U-tube diameter, (f) U-tube leg and distance from the centre of the borehole, and (g) ground water level and flow velocity, on the performance of GHEs. For the prediction of the heat injection rate of a GHE, a tool was developed with the use of FlexPDE software (PDE Solutions Inc). The tool considers GHE characteristics, the installation area and ground properties and groundwater flow. Twenty-two boreholes located in Nicosia were simulated to determine their geothermal performance. GIS software was employed to develop, for the first time, maps that provide information on the geothermal properties of the ground in Cyprus per meter depth to enable easy evaluation of the suitability of the ground for the installation of GHEs. All geothermal maps compiled in the framework of this research, are now available online, in a web application at https://amccy.maps.arcgis.com/apps/ImageryViewer/index.html?appid=d81a63acc03c4c35a80c65e8c1689c77 to facilitate easy accessibility by engineers working in the GHE design and installation field, for the use of engineers and designers of GHEs and ground source heat pump systems.

Since the ancient years, human beings were using holes and caves to protect themselves from weather conditions making it the first known form of exploiting ground’s heat, known as Geothermal Energy. Nowadays, geothermal energy is mainly used for electricity production, space heating and cooling, Ground Coupled Heat Pump (GCHP) applications, and many other purposes depending on the morphology of the ground and its temperature. This study presents results of investigations into the evaluation of the thermal properties of the ground in Cyprus. The main objectives were i) to determine the thermal characteristics of the ground in Cyprus, ii) investigate how they affect the sizing and positioning of Ground Heat Exchangers (GHE) and iii) present the results for various ground depths, including a temperature map of the island, as a guide for engineers and specifiers of GCHPs. It was concluded that there is a potential for the efficient exploitation of the thermal properties of the ground in Cyprus for geothermal applications leading to significant savings in power and money as well. Six new boreholes were drilled and two existing ones were used for the investigation and determination of i) the temperature of the ground at various depths, ii) its thermal conductivity, iii) its specific heat and iv) its density. The thermal conductivity was determined by carrying out experiments using the line source method and was found to vary in the range between 1.35 and 2.1 W/mK. It was also observed that the thermal conductivity is strongly affected by the degree of saturation of the ground. The temperature of the undisturbed ground in the 8 borehole locations was recorded monthly for a period of 1 year. The investigations showed that the surface zone reaches a depth of 0.25 m and the shallow zone 7 to 8 m. The undisturbed ground temperature in the deep zone was measured to be in the range of 18.3 °C to 23.6 °C and is strongly dependent on the soil type. Since the ground temperature is a vital parameter in ground thermal applications, the temperature of the ground in locations that no information is available was predicted using Artificial Neural Networks and the temperature map of the island at depths of 20 m, 50 m and 100 m was generated. Data obtained at the location of each borehole were used for the training of the network. Data for the sizing of GHEs based on the ground properties of Cyprus were presented in an easily accessible form so that they can be used as a guide for preliminary system sizing calculations. With the aid of Computational Fluid Dynamics (CFD) software the capacity of the GHEs in each location and the optimum distance between them was estimated. Additionally, the long term temperature variation of the ground was investigated. For the first time since a limited study in the 1970’s, a research focusing on the determination and presentation of the thermal properties of the ground in Cyprus has been carried out. Additionally, the use of Artificial Neural Networks (ANNs) is an innovative approach for the prediction of data at locations where no information is available. The publication of this information not only contributes to knowledge locally but also internationally as it enables comparison with other countries with similar climatic conditions to be carried out.

Biodegradable wastes cause high emissions of greenhouse gases (GHG) if not properly treated. The emissions can be reduced by the development of an effective waste management strategy. Waste-to-energy technologies, such as anaerobic digestion (AD) can be utilised for this purpose. Biomass energy from wastes is of particular interest to Cyprus that has to meet legal commitments for reducing its GHG emissions by 5% compared to 2005 levels and increase the contribution of renewable energy sources to 13% by 2020. This research project is making a significant contribution to this effort. The research considered the quantities and distribution of biodegradable waste in Cyprus and developed the necessary methodologies and tools for their estimation and determination of the potential for energy production through AD. The study identified that the predominant biodegradable wastes in Cyprus are the biodegradable fraction of municipal solid waste (MSW), sewage sludge, solid and liquid agricultural residues and solid and liquid wastes from the food and drinks industries. According to the estimated amount of solid and liquid biomass from these waste streams, at least 4,200 TJ of energy can be produced through AD, which represents 4% of the national energy demand. Livestock production is a very important source of waste due to the high potential of biogas production with the aid of AD. The produced energy can satisfy the needs of a farm, reduce the consumption of fuel and provide renewable energy to the national grid. Simple methodologies were developed and implemented for the estimation of energy consumption of the farm and the respective GHG emissions. It was found that in Cyprus the annual energy consumption per animal is lower than most other countries, due to favourable weather conditions which reduce the energy needs for heating. The emissions from energy use in livestock production contribute 16% to the total agricultural energy emissions. Literature review on AD, confirmed the complexity of the process, due to the many microorganisms involved. To estimate the potential of biogas production from animal waste through AD, three methods were developed based on the accepted relations that exist between Chemical Oxygen Demand (COD), volatile solids (VS), waste digested and biogas production. The results show that livestock production could cover the complete agricultural energy demand and make a considerable contribution to the renewable energy targets of Cyprus. Due to the identified importance that AD could have for Cyprus and to overcome deficiencies of existing models, the software FARMS was developed. The tool can be used by any farmer, consultant or policy maker for the estimation of the potential of biogas production, associated costs, reduction in GHG emissions and comparison of scenarios for waste management. Furthermore, the validation of the tool is presented. This was done through comparison against data collected from existing AD plants and through testing by potential users.