AIRBORNE WIND TURBINES Sean Metcalf Special Thanks: Sam Musa, Joshua Owens, and Greg Hutcheson OBJECTIVE: Determine the feasibility of using Airborne Wind Turbines (AWT) as an alternative way of utilizing wind energy to reduce the use of non-renewable energy sources.

BACKGROUND INFO: Figure 1: Description of how the AWT operates Makani Power, Joby Energy, KiteFarms and KiteGen have developed working prototypes and designs for high altitude AWTs Desired to produce more and consistent energy more cost effective than conventional solar and wind power Developed fixed-wing AWT, operational at altitudes of 250 to 600 meters. Makani Power tested prototype capable of 30 kW production.

RESEARCH & ANALYSIS: Research feasibility of utilizing AWT’s as an alternative source to harvest wind energy in the effort to reduce the use of non- renewable energy sources Conduct thermodynamic analysis and compare maximum power output for 30 kW AWT and a 30 kW conventional wind turbine Figure 2: Makani M30 AWT technical specifications

COMPARISON: AWT offshore wind farm applications AWT’s perform better at low wind speeds than conventional wind turbines Can produce about twice the power of a traditional wind turbine the same size Wind power represents %32 of all new electric capacity additions in the U.S. for 2010 Accounts for $14 billion in new investment U.S. wind power capacity reached 50,000 MW, enough electricity to power 13 million homes annually Figure 3: Wind energy production comparison (wind power information and figure used from www.energy.gov )

SAFETY & IMPACT: Operates below altitude of commercial flights and above the height of migratory birds 90% less material than a conventional turbine Can operate in hurricane conditions with winds in excess of 50 m/s with gusts reaching 80 m/s During extreme weather, it can land autonomously until conditions normalize Figure 4: Comparison of area and height between conventional turbines and the AWT

ANALYSIS: Thermodynamic derivation for rate of work or power output for a wind turbine using assumptions: Assumptions: Reversible process Control volume Heat Transfer and Potential Energy are negligible Steady-State Constant wind velocity Note: Equations uses constant for Betz ‘ Law, which limits the theoretical max. power efficiency for any turbine design to be %59. Observations: It is observed that the energy available in the wind for a turbine is only in the form of kinetic energy. The total power that can be derived from wind using a wind turbine is:

CONCLUSION: AWT system is feasible because it yields more energy more often because it taps into a more consistent and powerful wind at a higher altitude Doesn’t harvest most of the energy available to it, but it harvests what would otherwise remain untouched Promising solution for harvesting offshore and land renewable wind energy with low initial investment Mechanical, electrical, and computer automation systems maintenance for AWT’s would create more jobs Table 1: Using the above Power equation the following table shows the power yield for a 30 kW conventional turbine (model # FD 10-30/12 manufactured by Wind Resource Energy) and a 30kW AWT (model M30 Manufactured by Makani). Type Horizontal Shaft Wind Turbine Airborne Wind Turbine Make/Model WER FD 10-30/12 (30kW) Makani M30 (30kW) Sky Area 78.5m2 (5m radius) 1809m2 (8meter wing span) wind Speed (m/s) Available power (W) Actual output (w) % total Energy 7 9695.4 5300 54.7% 223313.3 15000 0.07% 10 28266.5 1800 6.37% 651059.1 30000 4.6% 13 62101.5 34000 1430376.8 2.1% 16 115779.5 29000 25.0% 2666738 1.1%

References: http://www.makanipower.com/how-does-it-work/ http://news.harvard.edu/gazette/story/2009/03/the-key-to-energy-independence-go- fly-a-kite/ http://online.wsj.com/article/SB10000872396390444230504577617971067036752.html http://www.jobyenergy.com/faq http://web.mit.edu/windenergy/windweek/Presentations/Wind%20Energy%20101.pdf http://energy.gov/articles/energy-report-us-wind-energy-production-and- manufacturing-surges-supporting-jobs-and