Judul: Desain Dan Uji Kinerja Tungku Gasifikasi Updraft Dengan Kulit Singkong Sebagai Bahan Bakar
Abstrak: Penerapan konsep gasifikasi merupakan salah satu alternatif pemanfaatan energi biomassa. Pada penelitian ini digunakan tungku gasifikasi updraft dengan sumber udara gasifikasi diperoleh dari kipas. Biomassa yang digunakan sebagai bahan bakar adalah kulit singkong yang telah dikeringkan sebelumnya. Tungku ini dinyalakan dari bagian atas atau lebih dikenal dengan metode toplit karena dinilai paling cocok. Uji kinerja dilakukan untuk mengetahui performa gasifikasi yang dilakukan menggunakan metode water boiling test. Kulit singkong diberi dua perlakuan berbeda yaitu variasi kepadatan dan variasi kadar air. Hasil percobaan menunjukkan bahwa tingkat kepadatan berpengaruh langsung terhadap konsumsi spesifik, laju pembakaran dan laju pergerakan charcoal bed. Sedangkan kadar air berpengaruh langsung terhadap kualitas gasifikasi. Nilai efisiensi tungku ini masih relatif kecil yaitu hanya berkisar antara 5.88 hingga 8.79%.
Keyword: Gasifikasi, Kulit singkong, Updraft

Judul: Pengembangan Tungku Gasifikasi Arang Biomassa Tipe Natural Draft Gasification Berdasarkan Analisis Computational Fluid Dynamics (CFD)
Abstrak: Sebuah tungku biomassa natural draft gasification (NDG) yang berbasis pada gasifikasi dengan efek gaya apung telah dikembangkan dengan pendekatan persamaan berbasis pindah panas dan equilibrium. Namun, metode tersebut belum dapat menjelaskan pengaruh bentuk geometri terhadap kinerja tungku. Oleh karena itu, penelitian ini menganalisis pengaruh bentuk geometri terhadap kinerja tungku dengan metode numerik melalui simulasi computational fluid dynamics (CFD). Tujuan penelitian ini adalah mengembangkan disain geometri yang mencakup diameter lubang udara sekunder dan tinggi cerobong gas mampu bakar dengan menggunakan simulasi CFD dan melakukan uji water boiling test (WBT) beserta komposisi gas pada tungku hasil disain. Prosedur penelitian melalui lima tahap yaitu tahap perancangan, penggambaran model, simulasi model, pabrikasi, dan uji kinerja lapang. Simulasi CFD model tungku NDG dilakukan meliputi dua tahap. Tahap pertama menentukan kecepatan aliran udara akibat adanya efek gaya apung. Kecepatan aliran udara yang dihasilkan digunakan pada simulasi tahap kedua untuk menentukan komposisi gas dan energi yang dihasilkan. Hasil simulasi tahap pertama menghasilkan data kecepatan aliran udara sebesar 0.1 m/detik (lubang primer) dan 0.11 m/detik sampai dengan 0.29 m/detik (lubang udara sekunder). Simulasi tahap kedua menghasilkan data energi tungku antara 1863.9 J/detik sampai dengan 2585.7 J/detik, dan memiliki efisiensi gasifikasi sebesar 67.11 %. Proses pembuatan tungku menggunakan ukuran tinggi cerobong gas bakar sebesar 10 cm, dan diameter lubang udara sekunder sebesar 4 cm. Uji WBT mendapatkan efisiensi tungku sebesar 22% sampai dengan 23 %. Uji komposisi gas mampu bakar menghasilkan gas CO sebesar 9.42% dan gas CH4 sebesar 3.87 %. Hasil uji lapang yang dilakukan ini dapat disimpulkan bahwa rancangan tungku yang dilakukan memiliki efisiensi tungku yang baik jika dibandingkan dengan efisiensi tungku konvensional lainnya.
Keyword: Efisiensi, Energi, Komposisi gas, Tungku

Judul: Exchange Market Pressure and Central Bank Intervention for Three ASEAN Countries
Abstrak: Two of the exchange rate systems which are adopted by many countries are the floating and the fixed exchange rate system. Both the exchange rate systems have different characteristics. Countries that implement fixed exchange rates system tend to set their domestic currency exchange rate at a certain point. On the contrary, countries which implement floating exchange rate system tend to let their domestic currency exchange rate to move flexibly and thus their value will always change according to the demand and supply of the currency in the foreign exchange market. Countries which implement floating exchange rate system are facing the risk of fluctuation in the exchange rate of their domestic currency against foreign currencies. The currency exchange rate fluctuation may be caused by economic problems such as a financial crisis. A country can also be potentially affected by other countries’ earlier financial crisis. This effect could potentially happen if these countries are in the same region, such as ASEAN. The 1997 ASEAN economic crisis was an example of a country’s financial crisis could affect other countries. At that time, some countries such as Indonesia, Malaysia and Thailand had to change their currency exchange rate system from the fixed exchange rate system to the floating exchange rate system due to the high costs which has to be incurred if they were to enforce the fixed exchange rate system. During 2002 until 2012, the domestic exchange rate of Indonesia, Malaysia and Thailand against the U.S. dollar had tended to fluctuate. If the domestic currency exchange rate fluctuated excessively then the central bank would intervene to stabilize the exchange rate in the foreign exchange market. The pressure on domestic currency exchange rate pressures has forced the central bank to intervene. The amount of those pressures can be analyzed by calculating the Exchange Market Pressure (EMP) index. Apart from that, the time when interventions are done by the central bank can be known based on EMP by calculating the Exchange Market Intervention (EMI) index. The purposes of this study were to determine the level of international pressure on the currency exchange market and monetary authorities intervene in three ASEAN countries, as well as to determine the effect of the monetary authorities intervene on the exchange rate of the domestic currency against the U.S. dollar in those three ASEAN countries. Based on the EMP index calculation results which are obtained during 2002 to 2012 period, the exchange rate of Indonesia, Malaysia and Thailand’s domestic currency had always fluctuated and the results of the EMP index indicated that each country were under diverse level of currency exchange rate appreciation and depreciation pressures. Thailand was the country with the highest currency exchange rate pressure compared to Indonesia and Malaysia. The results on the intervention index calculation showed that Indonesia, Malaysia and Thailand have intervention index between zero and one and more than one. We can also see from the intervention index that Indonesia and Thailand implement the controlled floating currency exchange rate instead of the freely floating one. Based on the calculation of the currency exchange rate by comparing
Keyword: exchange rate, exchange market pressure, intervention