Ground stations for Airborne Wind Energy
We industrialize ground stations for pumping kites. The ground stations are designed to contribute to low cost of energy and we have identified significant scaling- and volume advantages with our technologies, securing a future proof solution with excellent economy of scale. We design and manufacture the ground stations in close cooperation with our partner Imenco AS.
Digital hydraulic pump-motors control the winch directly. They have very high efficiency, also at part load, negligible inertia, precise torque control and significantly lower cost than all-electric systems. Winch diameters are from 1.25m and upwards, supporting a long tether life.
Energy storage in compressed nitrogen is used to smoothen the oscillating winch power and so increase the value of the electrical power output.
Electricity production starts with a controllable, high-efficient hydraulic motor driving an electrical generator. The choice of generator type is flexible, yet preferred is a synchronous machine, which offers a robust, energy-efficient and cost-effective solution. Absence of power electronics enables output voltages up to 15 kV. High voltage is especially valuable at utility scale, where it significantly reduces the need for step-up transformation (a challenge that is often forgotten in the evaluation of ground station technology).
Summary of benefits
Significant LCoE reduction
Energy storage with no degradation and "infinite" lifetime
Direct drive of large diameter winches
Proven off-shore components
The choices of technology dictate the material options. Not only weight has an impact; re-use, recycling and how sparse materials are from nature may be even more important. A ground station based on hydraulics contains very limited sparse materials and a high degree of easy-to-acces materials, mostly iron (Fe).
Energy storage in pressurized Nitrogen
No power electronics*
No permanent magnets**
Accumulator cylinders and Nitrogen bottles have ”infinite” life with minimum maintenance
Digital winch drive motors and generator drive motors can be refurbished with new wear parts
All parts except for control electronics, solenoid valves, UPS and generators are made of cast iron and steel, i.e. there is low risk of material shortage due to political or environmental restrictions and both re-use of components and recycling of materials are easy
* Compared to electrical ground stations. Small amounts of power electronics is used to control the synchronous generator and operate valves and auxiliary systems
** Compared to electrical ground stations. Small amounts of permanent magnets are used in sensors and auxiliary system
Airborne wind energy
Airborne wind is a great complementary to conventional wind turbines
An AWE system weighs only 10-20% of a conventional wind turbine.
Even small units can reach the stronger and steadier winds at high altitudes, it just takes a long tether. And when wind speed increases by just 25%, there is double the amount of energy to harvest.
AWE is easy to transport and install. All installations are at ground level, and foundation is at a minimum.
Easy transport and high reach allows for deployment in forests and hilly areas where conventional wind turbines are not practical, i.e. the global wind power potential is dramatically increased.
At 1MW, a stiff drone with approximately 30m wingspan is sufficient, and the ground station can be built into two 20ft containers. Alternative to the stiff drone is a soft and foldable parascute-like drone, yet using a similar ground station. Such compact solutions make AWE attractive, even for temporary installations.