An improved understanding of lignocellulosic biomass availability is needed to support proposed expansion in biofuel production. Fifteen studies that estimate availability of lignocellulosic biomass quantities in in the U.S. and/or Canada are reviewed. Sources of differences in study methods and assumptions and resulting biomass quantities are elucidated. We differentiate between inventory studies, in which quantities of biomass potentially available are estimated without rigorous consideration of the costs of supply, versus economic studies, which take into consideration various opportunity costs and competition. The U.S. economic studies, which included reasonably comprehensive sets of biomass categories, estimate annual biomass availability to range from 6 million to 577 million dry metric tonnes (dry t), depending on offered price, while estimates from inventory studies range from 190 million to 3849 million dry t. The Canadian inventory studies, which included reasonably comprehensive sets of biomass categories, estimate availability to range from 64 million green t to 561 million dry t. The largest biomass categories for the U.S. are energy crops and agricultural residues, while for Canada they are expected to be energy crops and logging residues. The significant differences in study estimates are due in large part to the number of biomass categories included, whether economic considerations are incorporated, assumptions about energy crop yields and land areas, and level of optimism of assumptions of the study.

Technology of photovoltaic cells and lithium batteries is developing rapidly. As a result, more and more attempts are made to build solar high altitude long endurance airplanes. Unfortunately, data on altitude impact on photovoltaic cells and batteries performance are not easily available. Moreover, acquisition cost of cells is still high. As a result, high altitude long endurance airplanes design is expensive and risky. Therefore, a tool for inexpensive testing of cells is needed. A small and very light unmanned aerial vehicle can be used for this purpose. It could fly as high as the envisaged high altitude long endurance airplane with a small number of cells and batteries, providing valuable information on them. The weight of such an experimental unmanned aerial vehicle could be minimized because long endurance would not be required, so heavy load of lithium batteries could be minimized, reducing also weights of other components. Wings of this unmanned aerial vehicle should enable installation of various types of photovoltaic cells including rigid ones. Therefore, it would be advantageous to apply an airfoil with a flat-upper-surface as large as possible. Unfortunately, flat-upper-surface airfoils are not popular in airfoils catalogs. Therefore, an attempt was undertaken to design an airfoil with 75% flat upper surface. The research focused on maximization of the lift-to-drag ratio and power factor assuming low Reynolds numbers conditions since it was designed for a small unmanned aerial vehicle for photovoltaic cells testing. This paper contains description of design methodology, design assumptions, and the obtained results. Moreover, the authors describe the experiment undertaken to verify the design. The wind tunnel and a semi-span model used for this experiment are presented together with the obtained results. The model has a similar structure to the envisaged structure of unmanned aerial vehicle, so flexibility of the wing is taken into account.

Attempts to build solar High Altitude Long Endurance (HALE) airplanes are more and more frequent. In the future such airplanes may appear very useful for the economy because they may replace geostationary satellites in several applications for a fraction of cost. Unfortunately, necessary data on altitude effect on photovoltaic cells and batteries performance are not easily available. Therefore, flying testbed for their inexpensive testing is needed. Flat–upper surface airfoil was designed for application in small UAV dedicated for photovoltaic cells investigation at various altitudes. It should enable installation of rigid cells on the top of the wing without significant reduction of aerodynamic performance. It should also decrease a risk of damage of flexible cells due to the significant bending of long aspect ratio, elastic wings. This paper contains description of the design methodology, design assumptions and obtained results. Moreover experiment undertaken to evaluate the design is described as well. The wind tunnel and a semi–span model used for this experiment are presented together with obtained results. The model has exactly the same structure as envisaged structure of UAV, so flexibility of the wing is taken into account.