Abstract-The power system using the clean decentralized renewable horizontal axis river current turbine can be an alternative option in delivering locally and sustainably the energies for the communities inaccessible to the electricity connection. One of the important aspects in the technology design is the selection of the blade number. This aspects can raise several consequences including the performance, the manufacturing cost and the construction constrain. The performance must be on the top of the priority in the technology design as the river velocity is typically low which effortlessly brings the technology uneconomically attractive. This study deals with the investigation of effect of the blade number on the performance of the horizontal axis river turbine for low speed condition. The investigation is conducted by a parametric study with the mathematical model of the Blade Element Momentum. The results indicate that turbines with high blade number deliver a better performance than those with the lower blade number. However, the consequences will be the low rotation for the high bladed turbines thus requiring a high gearing ratio for the mechanical transmission. This study also discusses the reason for the results of the investigation and presents a recommendation for designing of the river turbine for such low speed condition in relation to the decision of the blade number.

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The unbalance on the supply and demand on the energy has an impact on the escalating energy price and potentially impedes the development. One of the power demands comes from the energy utilization in the building sector, in which the cooling system is among them. The application of the air conditioning based on the refrigerator system is obviously consuming much energy in the building. Thus reducing the role of this power consumed cooling system is so imperative. To apply the circulating fan or to employ the natural ventilation are among the alternative approaches to make a building cooler, without much consuming energy. The aim of this study is to investigate the effect the circulating fan and the natural ventilation, on the temperature and the humidity in a building in Southeast Sulawesi, a region with its high daily solar radiation. It conducts an experiment on a building model incorporated with the ventilation and the circulating fan. The result shows that by incorporating these alternative cooling devices, the temperatures in the building can be lower than that of a closed building (no fan and no ventilation). The magnitude in the decreasing on the temperature for the building with circulating fan is higher than that of the ventilation. Another result on the investigation shows that the relative humidity in the building with the circulating fan or the ventilation is relatively higher than that of the closed building.

Tujuan dari penelitian ini adalah untuk mengoptimalkan teknologi PV surya dengan menggunakan metode penyesuaian posisi panel bulanan di Sulawesi Tenggara. Studi ini mensimulasikan jumlah energi tahunan dari  metode yang diusulkan dengan menggunakan model matematika radiasi matahari yang jatuh pada permukaan miring, yang dikombinasikan dengan data radiasi global matahari, yang diperoleh dari NASA Langley Research Center Atmospheric Science Data Center Surface Meteorological and Solar Energy (SSE) web portal supported by the NASA LaRC POWER Project dengan menggunakan data pada bulan  Juliy 1983 sampai Juni 2005. Hasil penelitian ini menunjukkan bahwa pada bulan Januari, arah panel optimal adalah di  selatan dengan sudut kemiringan 25 °. Pada bulan Februari, sudut optimal bergeser ke 15 °, pada arah yang sama dengan sebelumnya, dan pada bulan Maret, sudut optimal adalah sejajar dengan permukaan bumi. Pada bulan April sampai September, sudut optimal berkisar dari 15° sampai 35 ° ke arah utara, sedangkan pada bulan Oktober sampai Desember, sudut optimal berkisar dari 10° sampai 25° ke arah selatan. Konfigurasi teknologi surya dengan penyesuaian sudut panel optimal bulanan dapat meningkatkan energi tahunan yang dihasilkan sebesar 10 persen, dibandingkan dengan metode sudut panel tetap.

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