Airborne wind energy systems present great promise for inexpensive, clean energy at remote locations, but have only been demonstrated through short-duration flights in very limited wind conditions. Because of the time and money that is required to implement full-scale airborne wind energy prototypes, convergence toward designs that achieve longer-duration flight in adverse weather has been slow. This paper presents an inexpensive rapid prototyping approach for improving the flight dynamics and control of airborne wind energy systems, which has been implemented and validated on Altaeros Energies most recent full-scale flight prototype. The approach involves the 3d printing of lab-scale water channel models of airborne wind energy lifting bodies, which enable prediction of dynamic flight characteristics, rapid iteration between the designs, identification of unknown or poorly known parameters, and improved control design. By applying this approach to its last prototype design cycle, Altaeros demonstrated robust operation in double the wind speeds sustained by its previous prototype (reaching a maximum of 21.2 m/s, with sustained 10–15 m/s winds), with demonstrably improved flight characteristics.

Aerostat development and testing costs often suffer from a lack of scalability. In particular, it very difficult to fabricate an inexpensive lighter-than-air system that can be evaluated in a lab environment, since the maximum allowable mass of the aerostat becomes prohibitively low for small length scales. This paper presents an evaluation of a novel water channel-based platform for assessing the flight dynamics of aerostats at a very small scale, in a lab environment, for a very low cost. Altaeros Energies' buoyant airborne turbine (BAT) is used as a case study to demonstrate the effectiveness of the proposed approach. Specifically, we identify important dynamic scaling properties and show how the water channel experiments are run to match these properties closely in the water channel vs. full-scale settings. We then show how the water channel results can be used in concert with a simulation model to predict the performance of the full-scale system. The ultimate result is a design which, after an inexpensive evaluation process, can proceed to a larger-scale prototype stage with a high degree of confidence in its success.

Several wind energy concepts utiliz e airborne systems that contain lighterthan-air gas, which supplements aerodynamic lift and expands these systems' available operating regimes. While lighter-than-air systems can incorporate the traction and crosswind fl ight motions of their heavier-than-air counterparts, several lighterthan-air concepts have also been designed to deliver large amounts of power under completely stationary operation and remain aloft during periods of intermittent wind. This chapter provides an overview of the history of LTA airborne wind energy concepts, including the design drivers and principal design constraints. The focus then turns to the structural and aerodynamic design principles behind lighter than air systems, along with fundamental fl ight dynamic principles that must be addressed. A prototype design developed by Altaeros Energies is examined as an example of the application of these principles. The chapter closes with suggestions for future research to enable commercially-viable LTA systems. Why Lighter-Than-Air?Lighter-than-air (LTA) technology refers to airborne systems that use helium, hydrogen, or other sources of buoyancy to provide lift. LTA systems include freefl ying blimps, airships, dirigibles, and z eppelins; as well as stationary, tethered systems such as moored balloons or aerostats. For decades, hundreds of large tethered aerostats have been deployed to lift heavy pieces of equipment into the air for long periods of time. Aerostats are the only tethered aeronautical platforms that have consistently demonstrated continuous airborne deployments for over a month at a time without returning to the ground.The concept of using LTA technology for energy generation is almost as old as LTA technology itself, and can be separated into three phases. The fi rst phase was Chris Vermillion ( ) · Ben Glass · Adam Rein Altaeros Energies