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Abstrak :
Temuan dalam penelitian ini menyanggah persamaan matematika dari penelitian yang ada yang telah menentukan sudut kemiringan optimal panel surya dengan perspektif lokasi subtropis. Pengaruh derajat lintang (Y) dan bujur (X) terhadap sudut optimum pemasangan panel surya di wilayah Indonesia direpresentasikan dengan persamaan -0,0093 X + 1,3042 Y. Nilai RMSE yang didapatkan adalah 1,88 dan nilai R2 adalah 0,928. Dalam penelitian ini dibuat persamaan matematis berdasarkan koordinat lokasi untuk menentukan sudut kemiringan optimum pemasangan panel surya di Indonesia serta menganalisis pengaruhnya terhadap aspek teknis dan ekonomis. Potensi keuntungan ekonomis yang didapatkan dari pemasangan panel surya pada sudut optimum di wilayah Indonesia, dengan kapasitas PLTS 1 MW dan diasumsikan memiliki umur produksi 20 tahun mencapai Rp9.260.495.729,26 ......The findings in this study refute mathematical equation from existing research that has been determining the optimum tilt angle of the solar panel with a subtropical location perspective. Influence degrees latitude (Y) and longitude (X) to the optimum angle of solar panel installation in the territory of Indonesia represented by the equation -0,0093 X + 1,3042 Y. RMSE value is 1.88 and R2 value is 0.928. In this study, a mathematical equation based on the coordinates of the location to determine the optimum tilt angle of the installation of solar panels in Indonesia and analyze its impact on the technical and economical aspects. Potential economic benefits gained from the installation of solar panels at the optimum angle in Indonesia, with a capacity of 1 MW solar and assumed to have a production life of 20 years are reach US$ 740.839,66.

Abstrak :
Energi fosil yang ada dibumi merupakan sumber daya alam yang sering digunakan oleh masyarakat hal itu mengakibatkan menipisnya sumber daya alam yang kita miliki hal ini membuat para peneliti melakukan penelitian untuk mendapatkan sumber energi alternatif yang lebih bersih dan aman bagi lingkungan. Salah satu energi terbarukan yang banyak diminati oleh para peneliti ialah energi radiasi matahari. Instrumen yang dapat mengkonversikan energi radiasi matahari menjadi energi panas ialah Solar collector. Maka dari itu peneliti melakukan penelitian dengan memvariasikan tilt angle dari solar collector yang ada di sistem sesuai dengan Standar ASHRAE 93-2003. Solar collector yang digunakan ialah pabrikan Jiangsu sunrain dengan rekomendasi flowrate-nya sebesar 3.6 lpm. Hasil yang didapatkan dari penelitian ini adalah Efisiensi thermal dari solar kolektor pada sudut kemiringan solar collector 15° menghasilkan efisiensi thermal maksimum sebesar 94% dan energi matahari yang dapat dimanfaatkan oleh solar kolektor yang paling besar ialah menggunakan sudut kemiringan solar collector sebesar 15° sebesar 2.36 kW. ......Fossil energy on earth is a natural resource that is often used by the community, this results in the depletion of our natural resources, this makes researchers research to obtain alternative energy sources that are cleaner and safer for the environment. One of the renewable energy that is in great demand by researchers is solar radiation energy. Instruments that can convert solar radiation energy into heat energy are solar collectors. Therefore, the researchers researched by varying the tilt angle of the solar collector in the system following ASHRAE Standard 93-2003. The solar collector used is the Jiangsu sunrain manufacturer with a recommended flowrate of 3.6 lpm. The results obtained from this study are the thermal efficiency of the solar collector at a tilt angle of 15° solar collector produces a maximum thermal efficiency of 94% and the solar energy that can be utilized by the largest solar collector is to use the solar collector tilt angle of 15° at 2.36 kW.

Abstrak :
The findings in this study refute mathematical equation in determining the optimum angle of the solar panel installation provided by Duffie and Beckmann, Heywood, Lunde, Chinnery, Lof & Tybout, and Garg. Existing research has been determining the optimum tilt angle of the solar panel with a subtropical location perspective. Influence degrees latitude (Y) and longitude (X) to the optimum angle of solar panel installation in the territory of Indonesia represented by the equation -0,0093 X + 1,3042 Y. RMSE value is 1,88 and R2 value is 0,928. In this study, a mathematical equation based on the coordinates of the location to determine the optimum tilt angle of the installation of solar panels in Indonesia and analyze its impact on the technical and economical aspects. The maximum potential economic benefits gained from the installation of solar panels at the optimum angle in Indonesia, assumed Feed in Tariff in Indonesia is US$ 0,25, with a capacity of 1 MW solar and assumed to have a production life of 20 years, are US$ 740.839,66.

Abstrak :
Salah satu faktor penentu diperolehnya jumlah energi surya yang maksimal dengan menggunakan panel surya adalah dengan menentukan sudut arah pemasangannya (tilt Angle). Beberapa rekomendasi pemasangan sudut panel surya dengan elevasi tinggi dipandang kurang relevan terhadap kondisi area tropis yang seakan tegak lurus dengan matahari. Sudut pemasangan panel surya yang optimum di daerah tropis dipandang perlu dilakukan karena daerah tropis memiliki kharakteristik kondisi lingkungan yang berbeda dibanding dengan belahan bumi yang lain. Besar sudut optimum panel surya direpresentasikan dengan persamaan 1.15875 X + 0.001075718 Y(X merupakan lintang dan Y merupakan bujur bumi), dengan nilai RMSE 2.398 dan R square 0.979. Dari hasil perbandingan jenis panel surya, thin film terlihat lebih efektif dibanding dengan monocrystalin dan polycristalin dalam pertimbangan terhadap rata-rata suhu lingkungan di daerah tropis. ......One of determinant factor in gaining maximum solar energy collected by Photo Voltaic Panel depended on the tilt angle of the panel. Some recommendation of high elevation tilt angle was not too relevant in tropical area as upright with sun. Optimum tilt angle on tropical area need to do, because tropical area has a special environtment characteristic than other earth hemisphere. The Optimum tilt angle on tropic area represented by the equation 1.15875 X + 0.001075718 Y (X for latitude and Y for longitude), which the RMSE 2.398 and R square 0.979. The comparison result of different type solar panel is thin film was greater than monocrystalin and polycrystalin based on tropic ambient temperature average.

Abstrak :
Heat source merupakan parameter yang penting dalam sistem panas bumi. Heat source akan memanaskan fluida atau meteoric water yang terkandung di dalam bumi. Fluida yang terpanaskan ini kemudian akan menghasilkan hot spring dan fumarol di permukaan. Munculnya manifestasi di permukaan dikarenakan adanya patahan yang menghubungkan reservoir dengan permukaan bumi. Maka dari itu, penting untuk mengetahui dimana letak reservoir dan patahan serta strukturnya saat eksplorasi. Selama ini analisis data gravitasi hanya fokus pada reservoir tidak sampai menentukan heat source. Tilt angle atau tilt derivative adalah metode derivative yang dapat digunakan untuk mengetahui kedalaman hot rock. Tilt angle memanfaatkan perbanding antara vertical derivative dengan horizontal derivative. Diharapkan dari penelitian ini kita dapat mengetahui kedalaman hot rock dari sistem geothermal yang berada di gunung lawu dengan menggunakan tilt derivative. Tidak hanya hot rock namun diharapkan juga dari penelitian ini kita dapat mengetahui letak struktur patahan yang kemudian akan digunakan untuk membuat model konseptual geothermal pada sistem geothermal di Gunung Lawu.Heat source merupakan parameter yang penting dalam sistem panas bumi. Heat source akan memanaskan fluida atau meteoric water yang terkandung di dalam bumi. Fluida yang terpanaskan ini kemudian akan menghasilkan hot spring dan fumarol di permukaan. Munculnya manifestasi di permukaan dikarenakan adanya patahan yang menghubungkan reservoir dengan permukaan bumi. Maka dari itu, penting untuk mengetahui dimana letak reservoir dan patahan serta strukturnya saat eksplorasi. Selama ini analisis data gravitasi hanya fokus pada reservoir tidak sampai menentukan heat source. Tilt angle atau tilt derivative adalah metode derivative yang dapat digunakan untuk mengetahui kedalaman hot rock. Tilt angle memanfaatkan perbanding antara vertical derivative dengan horizontal derivative. Diharapkan dari penelitian ini kita dapat mengetahui kedalaman hot rock dari sistem geothermal yang berada di gunung lawu dengan menggunakan tilt derivative. Tidak hanya hot rock namun diharapkan juga dari penelitian ini kita dapat mengetahui letak struktur patahan yang kemudian akan digunakan untuk membuat model konseptual geothermal pada sistem geothermal di Gunung Lawu. ...... Heat source is the important parameter in geothermal system which is will heats fluid or meteoric water that is contained in the earth. Basically, geothermal system formed as a result of heat transfer from heat source to the surrounding by conduction and convection. Geothermal manifestation occurs because of the propagation of heat from below the surface. The emergence of manifestations at the surface due to the fault that connects the reservoir to the earth rsquo s surface. Therefore, it is important to know where the location of the reservoir, the location of the fault, and the structure of the fault when exploration used gravity method. In general, analysis of gravity data only focus to determine the reservoir . Tilt angle or tilt derivative is a dervative method that can be used to determine the depth of the hot rock. Tilt angle utilizing comparison between vertical derivative with horizontal derivative. The zero contours of the tilt angle correspond to the boundaries of geologic discontinuities and are used to detect the linear features in gravity data. The half distance between 4 and 4 radians is equal to the depth of top of heat source. This research is expected that can we know the depth of top of heat source of geothermal system at Mt. Lawu using tilt derivative.

Abstrak :
Reflector is used to increase the amount of solar radiation that the solar panels are exposed with, thus increasing the production of electric power. Parameters and I-V characteristic curve of a solar panel is strongly influenced by the amount of solar radiation received by the solar panels. This paper will discuss the effects of flat reflectors on the parameters and I-V characteristic curve of the solar panels. The parameters are solar radiation and temperature at solar panel, maximum power output (PMPP), voltage when PMPP is reached (VMPP), current when PMPP is reached (IMPP), short circuit current (ISC), open circuit voltage (VOC), and Fill Factor (FF). In this study, the types of reflector material are stainless steel mirror and aluminum foil. Reflector is placed beside solar panels. Reflector tilt angle was varied at 30, 45, 60, and 75 degrees. The measurement results show that the greatest increases in solar panel producing electric power are achieved at 75 degrees tilt angle. Aluminum foil reflector and stainless steel mirror can increase power output of solar panels until around 31.5 % and 21.5% respectively. In this tilt angle, for these two types of material reflector, VOC and VMPP tend not to change, ISC, IMPP, solar radiation and temperature on solar panel are increasing, whereas FF is decreasing around 4%. Changes in these parameters refer to the condition without a reflector.

Abstrak :
As a tropical country, Indonesia has great solar energy potential, with an average solar radiation intensity of 4.8 kWh/m2/d. Consequently, the optimization of solar power plants in Indonesia is necessary. The objective of this paper is to investigate solar panel optimization in Indonesia using system advisor model (SAM) software. Optimization focuses on two main concerns, choice of photovoltaic (PV) type and optimum PV tilt angle. Research is conducted in three different cities in Indonesia. The annual energy production simulation is conducted on 5 kWDC PV on-grid systems with different PV types and slope angles. According to simulation results, Indonesia has a relatively low proper PV tilt angle, with a value of 11o, 11o and 6o for Jakarta, Makassar and Jayapura, respectively. It can also be derived that when compared to crystalline PV modules, thin film PV modules have better performance, with the highest annual energy production due to its temperature coefficient characteristics.

Abstrak :
The purpose of this study was to compare the lumbar lordotic angle (LL) and pelvic tilt angle (PT) in the simple modified Thomas test (SMTT) position with LL and PT in the Thomas test (TT) position. Participants (n = 20) were between the ages of 23 and 39 and had no history of trauma. LL and PT were measured by X-ray radiographs under three conditions: the SMTT position, TT position, and supine position. At the same time, the distance between the examination table and the popliteal fossa was measured with a ruler. These measurements were compared by one-way analysis of variance. LL (14.6 ± 6.7 degrees [°]) in the SMTT posi¬tion was significantly lower than in the TT position (18.6 ± 6.6 °) (p < 0.01). PT (33.5 ± 7.6 °) in the SMTT position was significantly higher than in the TT position (31.3 ± 6.9 °) (p < 0.05). The distance between the examination table and the popliteal fossa in the SMTT position (100 ± 37.7 mm) was significantly higher than in the TT position (73.5 ± 21A mm) (p < 0.01). These results suggest that LL and PT in the SMTT position are easier to assess than those in the TT position.