- What is AWE?
Vestas HAWT 9MW first test, set a world record for 24 hours generation at ‘rated power’ output (216MWh), see http://www.mhivestasoffshore.com/new-24-hour-record/
Makani M600 Offshore first test -> no power generation results
What could the Makani AWE world record have been for 24 hours maximum power output?
- “Base Load Capable Renewable Energy” (Enerkite website quote)
Wind is an intermittent power source. AWE YoYo and FlyGen are erratic power generators, even when the wind is blowing.
- “save 95% of the material at the same power rating.” (Enerkite website quote)
The Enerkite schematic shows AWE CAPEX > 4000 €/kW - more expensive than HAWT. So to put it another way, AWE uses only 5% of the materials but costs more (see 4).
An idea that is along the same lines as :
“The concept of swept area is the key to extracting energy from the wind. The larger the swept area, the greater the amount of energy that is available to the system. Our system sweeps through a large amount of area – as much as eight times that of a relatively-sized surface-based turbine” (Joby Energy quote from the distant past).
Performance (ref A) : Cosine losses of 35 -> 55%, and erratic power output, averaging 30 -> 40%, together, put AWE at ~20% of HAWT. Doubling (unrealistic) the Capacity Factor (CF) gives only ~40%. To get the same ‘rated power’ output, wings need to be bigger, generators need to be bigger … and it costs more.
Power Curves (predicted)
Enerkite : rated wind speed = 8m/s, CF = ~70% (Onshore) (Enerkite website)
Makani : rated wind speed = 11.5m/s, CF = ~60% (Offshore) (Patent 20190154003)
Ampyx : rated wind speed = 15m/s, CF = ~40% (Offshore) (The Sea-Air-Farm Project)
Pick the winner(s)?
Note : at higher altitudes there are generally stronger and more consistent winds.
Note : the higher the rated wind speed, the lower the CF (and vice versa).
- Onshore or Offshore
There is no wind advantage for AWE Offshore (wrt HAWT), the wind shear is small, so CF is roughly the same (ref A). Makani M600 with a ‘rated power’ output of ~250kW, would need 48 units to match one 12MW HAWT.
Installation : 48 sets of cables (extra long due to spacing), 48 boat trips with crew (weather permitting). Maintenance (OPEX) : 48 …
So ‘Scale Up’ to MW, but the FlyGen & YoYo designs don’t scale (see M30 -> M600).
- Is it safe?
Safety is the top priority. Making a System safe can be expensive.
Tether breaks will occur occasionally. Single tether systems will incur high costs to demonstrate detached Safe landing in a farm, under adverse weather conditions.
Automated Launch & Landing will not always be successful during a unit’s 25 year service life. Kite crashes (and unparked kites) will have to stay within the unit’s land/sea farm space, under all conditions. Commercial viability will be dependent on the number (and cost) of kite/tether replacements per unit lifetime. Keeping the kite on the ground (safe) or in an unproductive state will decrease CF, and also affect viability.
- Levelised Cost Of Energy (LCOE)
LCOE is the metric used to differentiate between potential solutions.
The new Offshore HAWT GE 12MW, predicts < ~9 cent/kWh (current Offshore benchmark) in the near future, and Onshore HAWT is already at 3 to 5 cent/kWh (Lazard LCOE v13 2019).
The two most widely studied AWE designs (YoYo and FlyGen) give no evidence that they can compete with diesel at ~30 cent/kWh, let alone with HAWT.
- Miles Loyd ‘Crosswind Kitepower’ (1980)
The paper is well worth a read, because it introduces the concepts of ‘lift power’ (YoYo) and ‘drag power’ (FlyGen) using a quantitative analysis. These designs were plausible alternatives to the HAWT of the period.
HAWT has moved on, higher Capacity Factors, bigger size MW, much lower LCOE.
AWE needs to move on. AWE needs new designs that can compete (on LCOE) with the new HAWT.
- AWE Standard Design
The ‘Standard Design’ for AWE is still to be found, although some things seem obvious.
Imagine your first day at a new AWE Company. You are given a blank piece of paper and tasked to create a new design. The boss says “Where do we put the generator?” :
a) on the wing
b) on the tether
c) on the ground
Makani a), Altaeros b) and Ampyx c) have spent millions on different solutions.
There are no experts in AWE, just good ideas and bad ideas …
ref A) Offshore Comparison : Makani vs HAWT