Although soybean-, sunflower-, palm-based biodiesel options have been recognized as DEA efficient, due to the debate of ��biodiesel versus food,�� if soybean selleck chem Perifosine and sunflower are used to produce biodiesel, it may cause food crisis. From this point of view, palm is the most suitable to be chosen as the sustainability efficient option.The authors calculate the emergy indices in an accurate and objective way, but there are also some drawbacks.The consistency of the data: the data about the energy consumption in each item and the transformity are cited from different published work, and some of the data has been adjusted.The temporal and spatial consistency: the data used in emergy indices calculation are not obtained in the same time, and the cases studied have been assumed to locate in the same region.
The future work is to obtain high quality data and develop related method to verify the accuracy of the data.5. ConclusionAlthough biodiesel has been a hot spot since several decades ago and different scales of biodiesel plants have been operated around the world, the sustainability is not optimistic in the current situations. None of the options for biodiesel production is sustainable in a long term. In order to achieve high sustainability of biodiesel production, new plantation technologies to reduce the use of fertilizers and pesticide and to increase the yield of crops and novel methods to produce biodiesel with vegetables oil are prerequisite.
Effective utilization of solar energy is an important research subject of photovoltaic (PV) system at present, and using the electric energy generated by solar cell is the key.
The electric energy generated by solar cell is very likely to be influenced by environmental factors, such as irradiance conditions, solar angle, temperature variation, and instability of output power or shadow, which would result in power loss of solar cell [1]. Therefore, there must be an electric energy controller with good robustness and stability to ensure the effective utilization of solar energy, in order for the overall solar power supply system to generate maximum electric energy efficiently and maintain the balanced and stable control of system [2]. Recharging of secondary battery efficiently is very important. The chargers only charged batteries in the past, and the charging method and efficiency were not designed well, so that the excessive charging time or frequency often damaged batteries and reduced the lifetime.
In order to improve the life or charging effect of secondary battery, there must be a good charge control design for battery, so that the battery life can be prolonged and the charge efficiency can be increased [3�C5]. Many studies of the charger of PV system use single-buck converter Brefeldin_A to discuss the overall MPPT and charge control system [6].