Journal of Sustainable Energy

5

Authors: OHAJIANYA A. C., ABUMERE O. E., OSAROLUBE E., MBAMALA E. C.

Flooding, which is now a yearly occurrence in most parts of the World, can be minimized if reservoirs are constructed at suitable locations to store rain accumulated water for the purpose of irrigation or electric power generation. In that light, we have estimated the amount of electric energy that can be generated using rain accumulated water from Aboh and Ahiazu Mbaise in Imo State, Nigeria to drive a hydro turbine in the Federal University of Technology, Owerri, Nigeria. This was done using the rainfall data of Mbaise, accessed from www.worldweatheronline.com; the land area of Aboh and Ahiazu Mbaise, measured with the help of Google map; and the average altitude difference of FUTO and the reservoir site at Aboh Mbaise, determined with the help of Google topographic map. It was estimated that a total of 9.7 GWh of electricity can be generated per year if 100% of rainwater from Aboh and Ahiazu Mbaise is accumulated and used to drive a hydro turbine in FUTO. This is equivalent to 406 days of 10 MW of electric power. If 30% of the rainwater is accumulated instead, a total of 2.9 GWh of electricity can be generated per year, which is equivalent to 122 days of 10 MW of electric power

7

Authors: MIRCEA I., ALBULESCU E.F., BUZATU G.C., BRATU C.

The paper presents general aspects regarding the nature of loads that are generated and circulate in low voltage networks, the influence on the null conductor and the calculation of the actual value of the current on the null. The paper considers the measured values of null current in networks with deforming and unbalanced loads related to transformer stations. The calculation of power and energy losses in symmetrical and non-symmetrical balanced three-phase networks allows the determination of the CPT growth rate (own technological consumption) and its comparison with that determined from the graphs given by the standards. Balancing measures of phase loading and reduction of deforming regime are analyzed

7

Authors: DAMASEN IKWABA PAUL

The current and voltage of a solar cell can be measured by optimal load method. However, this method does not automatically adjust the load to ensure maximum power output as solar irradiance varies, hence power output losses. This study investigated the losses in power output that occur in solar cell when characterised by optimal load method. This was done by exposing the solar cell at different illumination intensities (between 300 and 1,000 W/m2 in the interval of 100 W/m2 ) and measuring current and voltage using Keithley Source-meter as well as optimal load (102 mΩ) method. From current and voltage, maximum power output of the solar cell for both methods were calculated and compared. It was found that the power output calculated from optimal load method (102 mΩ) were in good agreement with those from Keithley 2340 Source-meter only between 500 to 700 W/m2 . As a result, the solar cell lost between 1.3 to 33.4% of its maximum power when illumination intensities were outside the operating range of the optimal resistive load. Conversely, when a resistive load of 45 mΩ (which is not optimal) was used, the solar cell lost between 0.8 to 81.4% of its maximum power at various illumination intensities

11

Authors: FELEA I., CRENCI E., SZABO E.

Knowledge of energy performance indicators is essential to substantiate investment decisions in energy facilities. Energy audit is the procedure by which energy performance indicators can be assessed and identified measures to improve them. Considering the share and the potential to improve the efficiency of cogeneration sources for the production of thermal and electrical energy, the determination of their performance indicators based on energy audits is essential for achieving the goals of reducing energy consumption. This paper is a synthesis of the results obtained in performing the energy audit of a cogeneration source serving an industrial consumer. After describing the general framework, the justification of the concern and the presentation of the defining elements of characterization of the analyzed installation, the second part of the paper refers to the specificities of the applied complex energy balance model. Next, reference is made to the methodology for obtaining input quantities in energy balance models and mass balance sheets. The final part of the paper presents the results obtained, the values of the performance indicators, the measures for improving the energy efficiency and the general conclusions of the analysis.