Investigation of time diversity gain for earth to satellite link using rain rate gain

The utilization of satellites for communication systems has expanded considerably in recent years. C and Ku-bands of frequencies are already congested because of high demand. Future directions of satellite communications are moving towards Ka and V-bands. Earth to satellite communications are moving towards higher frequency bands in future which are more sensitive to environment. Rain causes severe degradation in performances at higher frequency bands specially in tropical regions. Several mitigation techniques are proposed to design reliable system. Time diversity is one of the potential candidate for it. However, time diversity analysis requires measured rain attenuation data. For future high frequency link design those data are not available at most of the places. This thesis proposes a method to utilize 1-minute rain rate to analyze time diversity technique at any desired frequency. This paper proposes a method to utilize 1-minute rain rate to analyse time diversity rain rate gain. In proposed method, it is assumed that rain rate gain with delay can represent rain attenuation gain with delay for same period of time at same location. The characteristics of rain rate and rain attenuation almost same because the attenuation causes due to rain. One year measured rain rate in Malaysia is used to predict rain rate gain. The measured gain at 12.225 GHz signal is compared with that predicted by ITU-R based on rain rate measurement and is found good agreement. Hence it is recommended that the time diversity gain can be predicted using measured rain rate for any desired frequencies

Renewable energy resources and technologies practice in Bangladesh

Bangladesh has very limited nonrenewable energy resources of its own. She is facing energy crisis and serious desertification problem in rural areas. These issues could be removed if renewable energy is used as a primary source of energy in rural areas. It is essential for scientists and researchers to find out the renewable energy resources and effective technologies. Bangladesh is endowed with vast renewable energy resources such as biomass and solar insolation. Besides, hydro and wind power can be considered as potential renewable energy resources. Harnessing these resources appears to be a promising solution for improving the quality of life of rural villagers. The government and many non-governmental organizations (NGOs) have tried to comprehend and have strived to address the problem of energy. This paper reviews the renewable energy resources and renewable energy technologies (RETs) practicing in Bangladesh in terms of its implementation, research and development activities. The development and trial of systems are mostly funded so far by donor agencies in collaboration with government and NGOs. Biomass energy sources are traditionally used for domestic cooking and in small rural industries. Approximately 60% of total energy demand of the country is supplied by indigenous biomass based fuels. Activities on the development and promotion of biomass technologies have been going on for one decade. Some national and international funds have been available for biogas technology, improved biomass cookers and production of biomass briquettes. At the time, around 25,000 biogas plants exist all over the country in rural areas and educational institutes, etc. More than 0.20 million improve stoves have been installed to save biomass fuel. Over 900 briquetting machines have been operating in the country on commercial basis. The annual solar radiation availability in Bangladesh is as high as 1700 kWh/m2. Research and demonstration activities carried out for one decade have led to a start of large-scale utilization of PV (solar photovoltaic) by various organizations and by NGOs. More than 61,500 solar PV systems of a total capacity around 3 MW and 260 hot box cookers have been installed all over the country mainly in off-grid rural, hill tracks and coastal Bangladesh. Kaptai hydroelectric power plant is the only one renewable energy power generation plant of the country that is generating 3.28% of total 3651.20 MW. The first micro hydropower unit of 10 kW has been installed in a village of Bandarban through private initiatives. The project is providing electricity to 140 families in the village and to a Buddhist Temple. The annual wind speed at a height of 25 m at some coastal locations is above 4 m/s and much higher in the pre-monsoon and monsoon periods. The sites are suitable for power generation, particularly using PV or diesel hybrid technique for winter months.Renewable energy resources RETs practice Quality of life Rural, hill tracks and coastal Bangladesh

Production of liquid fuel and activated carbon from mahogany seed by using pyrolysis technology

The renovation of biomass waste in the form of Mahogany seed waste into bio-fuel as well as activated carbon by fixed bed pyrolysis reactor has been taken into consideration in this study. The mahogany seed in particle form is pyrolyzed in an enormously heated fixed bed reactor with nitrogen as the carrier gas. The reactor is heated from 4000C to 6000C using a external heater in which rice husk and charcoal are used as the heater biomass fuel. Reactor bed temperature, running time and feed particle size have been varied to get the optimum operating conditions of the system. The parameters are found to influence the product yields to a large extent. A maximum liquid and char yield are 49 wt. % and 35 wt. % respectively obtained at a reactor bed temperature 5000C when the running time is 90 minutes. Acquired pyrolyzed oil at these optimal process conditions were analyzed for some of their properties as an alternative fuel. The oil possesses comparable flame temperature, favorable flash point and reasonable viscosity along with somewhat higher density. The kinematic viscosity of the derived fuel is 3.8 cSt and density is 1525 kg/m3. The higher calorific value is found 32.4 MJ/kg which is significantly higher than other biomass derived fuel. Moderate adsorption capacity of the prepared activated carbon in case of methyl blue & tea water was also revealed