The purpose of this study is to determine the feasibility of replacing diesel with natural gas as a fuel source for modern drilling rigs. More specifically, this thesis (1) establishes a control baseline by examining operational characteristics (response, fuel usage, and cost) of an existing diesel-powered land rig during the drilling of a well in the Haynesville Shale; (2) estimates operational characteristics of a natural gas engine under identical conditions; and (3) draws a comparison between diesel and natural gas engines, determining the advantages and disadvantages of those fuel sources in drilling applications. Results suggest that diesel engines respond to transient loads very effectively because of their inherently higher torque, especially when compared with natural gas engines of a similar power rating. Regarding fuel consumption, the engines running on diesel for this study were more efficient than on natural gas. On a per-Btu basis, the natural gas engines consumed nearly twice as much energy in drilling the same well. However, because of the low price of natural gas, the total cost of fuel to drill the well was lowered by approximately 54%, or 37,000 USD. Based on the results, it is possible to infer that the use of natural gas engines in drilling environments is feasible, and in most cases, an economical and environmental advantage. First, when compared with diesel, natural gas is a cleaner fuel with less negative impact on the environment. Second, fuel cost can be reduced by approximately half with a natural gas engine. On the other hand, natural gas as a fuel becomes less practical because of challenges associated with transporting and storing a gas. In fact, this difficulty is the main obstacle for the use of natural gas in drilling environments. In conclusion, because of its minimal drawback on operations, it is recommended that in situations where natural gas is readily available near current market prices, natural gas engines should be utilized because of the cost savings and reduced environmental impact. In all other cases, particularly where transport and storage costs encroach on the cost benefit, it may still be advantageous to continue powering rigs with diesel because of its ease of use.

When a wind farm is repowered, decommissioned turbines are discarded. This creates a stock of wind turbines that can be acquired for a fraction of the original cost, and refurbished. Taking advantage of the reduced price and the ruggedness of first generation wind turbines, new markets for sale of wind energy can be explored. This thesis first analyses the repowering background of Germany, Denmark, and other European countries, where transition to repowered or “second generation” wind farms is taking place. Then, a number of feasibility studies are reviewed to create a study framework, which will allow in-depth study of suitable energy markets. Using this framework, the suitability of four countries is analysed in detail: Djibouti, Madagascar, Mozambique, and Tanzania. Two countries are selected to perform a total of 6 site studies: Djibouti and Tanzania. Using WindPro 2.9, six model wind farms are simulated. A financial model is built, based on an NREL study, to analyse the economic viability of wind farms. Using the financial model, the levelized cost of energy is obtained, and used to evaluate the competitiveness of the model wind farms. A sensitivity study is carried out to identify the major influences on the LCOE. Using the cost data, the cost competitiveness of the proposed wind farms is discussed, including competitiveness in the target markets, and a cost comparison with commercial wind farms with new turbines is performed. Five out of six proposed wind farms are competitive in price in the target markets, and all achieve an average installation cost per kW of one third of conventional wind farms, while producing energy in the low range of commercial projects, and even lower for sites with excellent wind resources.

In July 2001 in the region of Kastri Platanistou in Evia, Greece a wind power park of 5 MWinstalled capacity, began its commercial power production under the supervision of the companyMELTEMI-KASTRI.During these 6 years of its operation significantly reduced incomes were recorded compared to theinitial study financial analysis. Apparently loss of income occurred due to technical failures;nevertheless more costly might have been a suboptimal primary energy analysis.Herein, the collected data from the nacelle of the wind turbines and a net installed in the site wereanalyzed in order to estimate the site’s wind energy potential and gain knowledge of the parametersthat so far affected the overall production. The analysis was performed through Windrose andWAsP software.Aiming to maximize the exploitation of the site’s wind energy potential, several wind turbinemodels in different installation points were examined. Further analysis of the exported resultsindicated the optimum scenario, finally suggested to the owners of the wind farm.