“Wind” movement of air caused by differences in temperatures in the earth’s atmosphere. Wind which is everywhere around us in abundance has been harnessed for centuries. We at Connect-Green keep an eye out for the latest developments on the evolving trends in the alternative energy sector as we believe that is where the future is.
Joby Energy a wind energy company based in Santacruz California is one such innovator. They have been developing airborne wind turbines which harness the winds at higher altitudes. Going higher means an increase in the velocity of the wind. Higher speeds at greater altitudes should produce a higher energy output. The idea for harnessing the high altitude wind has been around since 1970’s but was deemed non-viable.
Their multi-wing structure supports an array of turbines. The turbines connect to motor-generators which produce thrust during takeoff and generate power during crosswind flight. Orientation in flight is maintained by an advanced computer system that drives aerodynamic surfaces on the wings and differentially controls rotor speeds. A reinforced composite tether transmits electricity and moors the system to the ground. The tether that moors the turbine to the ground has electrical conductors inside, which transmit generated electricity from the vehicle to substations.
After testing more than 20 different prototypes, the company has settled on a 30kW system, which it is using to evaluate the efficiency of the design. If successful, it intends to pilot test a 100kW prototype within the next year.
The firm’s goal is to create an initial line of systems with a power capacity of 300kW which would be capable of generating enough energy to power around 150 homes. Larger systems of 3MW or more could potentially power 1500 homes.
What makes their system better than the surface-based systems? According to Joby Energy these are the significant features:
- Produce energy more consistently. Because they are operated at higher altitudes, the system produces twice the energy for the same rated power. Consistent winds at higher altitudes allow their system to achieve a net capacity factor of approximately 70% versus 35% for surface-based systems.
- Require lower capital costs. Building their system requires significantly less materials than a surface-based turbine (approximately 1/20), resulting in low capital costs for the given rated power.
- Deliver the most cost-effective renewable energy. Consistent energy production and low capital costs result in energy production cost per kWh lower than all other renewable sources.
Joby energy website says “High-altitude wind has between 2 and 30 times more power density than surface wind. This is because of two factors: First, the power in the wind decreases linearly with decreasing air density, so air that is one-third as dense contains one-third the power. Second, the power contained in the wind increases as the cube of speed, so five times the wind speed yields 125 times the power. Equally, if not more important is that high-altitude wind is significantly more consistent than surface winds. Even during times of low wind, our system can tack across the sky on the tether, thus maintaining consistent output.”
Many other companies like the Ottawa based Magenn Power, Sky Windpower and the Italian firm Kitegen Research are also researching the options to capture the high altitude winds for a greener energy future.
“It’s not like the more you use it, the more you run out… It doesn’t matter how much you use it. It’s still there every day. It’s free energy, continuously guaranteed as long as the Earth is what it is. –Cristina Archer, Assistant Professor, Department of Geological and Environmental Sciences, California State University – Chico“
Let’s hope sometime soon we will have a solution to harness high altitude wind for a Greener and more wallet friendly solution to replace our dependence on non-renewable energy sources. Live Green!