Edinburgh Napier University

  This thesis investigates the application of large scale concentrated solar (CSP) and photovoltaic power plants in Libya.

Direct Steam Generation (DSG) offers a cheaper and less risky method of generating electricity using concentrated solar energy than Heat Transfer Fluid (HTF) plant. However, it is argued that the location of a DSG plant can be critical in realising these benefits, and that the South-East part of Libya is ideal in this respect. The models and calculations presented here are the result of an implementation of the 2007 revision of the IAPWS equations in a general application based on Microsoft Excel and VBA. The hypothetical design for 50MW DSG power plant discussed in this thesis is shown to yield an 76% reduction in greenhouse gas emissions compared to an equivalent gas-only plant over the ten-hour daily period of operation. Land requirement is modest at 0.7km2.

A new method for improving the distribution of heat within the absorber tube wall was developed. Internal helical fins within the absorber tube have been proposed to provide a regularly pitched and orderly distribution of flow from the ‘hot’ to the ‘cold’ side of the absorber tube. Note that the irradiance profile on the absorber tube is highly asymmetric. A CFD simulation using FLUENT software was carried out for three types of pipes with different internal helical-fin pitch, and an aluminium pipe without fins. The results show that the thermal gradient between the upper and lower temperature for the pipe without a helical fin is considerably higher compared with the pipes with helical fins. Also, the thermal gradient between the two halves for the aluminium pipe (without a helical fin) is much lower when compared to the result for the traditional steel pipe (without a helical fin).

A 50MW PV-grid connected (stationary and tracking) power plant design in Al-Kufra, Libya has been carried out presently. A hetero-junction with intrinsic thin layer (HIT) type PV module has been selected and modelled. The effectiveness of the use of a cooling jacket on the modules has been evaluated. A Microsoft Excel-VBA program has been constructed to compute slope radiation, dew-point, sky temperature, and then cell temperature, maximum power output and module efficiency for this system, with and without water cooling for stationary system and for tracking system without water cooling. The results for energy production show that the total energy output is 114GWh/year without a water cooling system, 119GWh/year with a water cooling system for stationary system and 148GWh/year for tracking system. The average module efficiency with and without a cooling system for the stationary system is 17.2% and 16.6% respectively and 16.2% for the tracking system. The electricity generation capacity factor (CF) and solar capacity factor (SCF) for stationary system were found to be 26% and 62.5% respectively and 34% and 82% for tracking system. The payback time for the proposed LS-PV power plant was found to be 2.75 years for the stationary system and 3.58 years for the tracking system.

The modelling that was carried was based on the measurements conducted on the experimental system set in a city in the southern part of Turkey. Those measurements are recorded by a Turkish team at Iskanderun. As well as the current, voltage and cell temperature of the photovoltaic module, the environmental variables such as ambient temperature and solar irradiance were measured. These data were used for validation purposes. The correlation for the conversion of solar irradiation from horizontal to sloped surface indicated that the presently used model is highly successful reflected by the goodness of fit parameters: the coefficient of determination is 0.97, and the mean bias error -2.2W/m2. Similarly, the cell temperature model used in the present thesis is validated by the following correlation parameters R2 = 0.97 oC, while MBE is 0.7 and RMSE = 2.1 oC.