This study proposes a two-tower type fluidized receiver for receiving concentrated solar light at high temperatures is proposed. This fluidized receiver is coupled with the Miyazaki beam-down reflector system. The visualization and the numerical simulation was made for the laboratory model to show the fluid-dynamics and the heat transport as well as to elaborate the existing demonstration model. The experimental visualization of the cold model demonstrated that in each tower, the particles are moved by the aerated organized flow. The numerical simulation was made using the thermal input cited from the 5.0kWth sun simulator. The numerical simulation demonstrated that the inner particles are heated above 950°C after 3.0 minutes of the aeration start time. The increase in temperature is caused by the intrusion of the heated particles from the high-pressure side tower to the low-pressure side tower. It is thus suggested that collective circulation occurs between high- and low-pressure side towers and this can be utilized for a direct thermal storage system.
This paper proposes an estimation method for solar radiation intensity, using pictures taken by a web camera. This approach makes use of the relationship between solar radiation intensity and the color properties of pictures. A clear day model and a cloudy day model are introduced as fourth-order polynomial expressions consisting of the brightness value and saturation as color properties. Furthermore, a hybrid model that can be switched to either the clear day model or the cloudy day model, according to the weather as determined by Japan Meteorological Agency, is developed. The validity of the proposed method is examined using the mean absolute error. Based on the study results, the proposed method can effectively measure solar radiation intensity.
The concept in which renewable energy is imported from foreign countries or other regions using energy carriers should be strongly promoted from the viewpoint of energy security and climate change in addition to development of other energy technologies. The apparent economic comparison among electricity and these chemicals as energy carriers was done in our earlier studies. However the costs in our earlier studies were relatively high compared with the present electricity prices. In this paper, cost reduction of these systems is described. By setting parameters properly, the re-electrification cost in Japan is reduced to the range of the present electricity price in Japan. Therefore, large scale demonstration and deployment projects and/or financial incentives for these systems are necessary to commercialize these systems.
Recently, much attention has been paid to ionic liquid as solvents for woody biomass. Previously we reported that cellulose is partially dissolved and depolymerized into various low molecular weight compounds such as cellobiose, cellobiosan, glucose, levoglucosan, fructose and 5-hydroxymethylfurfural (5-HMF) in 1-ethylpyridinium bromide ([EtPy][Br]) at 120ºC. Among these compounds, levoglucosan can be produced with high yield. In this study, therefore, we investigated the methods to enhance the yield of levoglucosan from cellulose as treated with [EtPy][Br] at 120ºC. Pretreatment was studied to make cellulose amorphous by some ionic liquids, 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) and 1-ethylpyridinium chloride([EtPy][Cl]). As the result, the yields of levoglucosan from cellulose were improved greatly by the pretreatment with all ionic liquids used. As another trial, we investigated the heating with microwave for [EtPy][Br] treatment. The yields of levoglucosan were higher in a shorter reaction time by microwave heating than by ordinal oil bath heating. These two methods were efficient to attain higher yield of levoglucosan from cellulose by treatment with [EtPy][Br].
Since wood pellet is a good medium for storage and transportation of woody biomass, it could be a promising raw material for biorefinery. However, wood pellet may change the chemical reactivity because wood suffer from physical pressure and heat during pelletization. In this study, delignification rate during soda cooking, a promising pretreatment method for softwood was compared between softwood whole wood pellet and the raw wood chip just before pelletization. The wood chips were further milled to smaller wood particles during pelletization to form wood pellets. Although wood pellet is easily disintegrated to the small wood particles in the beginning, delignification of wood pellet was slower than the raw chip. Longer cooking time and particle size reduction give very similar pulp yield between wood pellet and chip, indicating that the delignification rate was determined by the delayed diffusion of sodium hydroxide due to compression of the wood cell lumen by physical densification. Wood pellet could be digested in the same way as the raw wood only by longer impregnation in the reagent or particle size reduction, meaning that wood pellet could be used well enough as a raw material for saccharification.
Based on the previous experiment, an updraft gasifier has been modified by adding a gas outlet for producer gas at the reduction zone. The gasifier is operated under a variety of conditions that enable investigation on the effect of gas outlet modification on the amount of tar produced. The producer gas is tapped at a gas outlet at the top of the gasifier (conventional mode), a gas outlet in the reduction zone (reduction mode), and combination of the tapping of the gas outlets at the top of the gasifier and in the reduction zone (combination mode). The experimental results show that the tar content from the gas outlet at reduction mode is less than that at the conventional mode, i.e. 81 g (m3-N)-1 and 111 g (m3-N)-1, respectively. Meanwhile, the tar content from the combination mode is about 55 g (m3-N)-1 at the reduction zone and 102 g (m3-N)-1 at the top. Nevertheless, the lower heating values for each mode are similar, that is in the range of 4.6 - 4.9 MJ (m3-N)-1. The hot gas efficiency reaches a maximum of 82% on gas outlet reduction mode.