4 hour energy storage flywheel

I thought I would never see a flywheel with 4 hours of energy storage.  Amber Kinetics has managed to develop a 6.25 kW flywheel with 29 kWh of energy storage.  The traditional flywheels I was aware of stored less than one minute of energy.

Here is what we know:

- Weight of flywheel = 5,000 lbs

- Speed of rotation = 8500 rpm

- Flywheel is a monolithic steel rotor

- Flywheel is also used as rotor for the motor/generator

- Stator is 8 pole permanent magnet

- Full power conversion to get 60 Hz AC

Although no cost is mentioned, one of their key objectives is low $/kWh cost and second is low self discharge rate.

Details are available at:

Hawaii Electric seems to be the first customer.

Reaching for the sky ... 166m hub height of onshore wind turbines

Vestas has introduced onshore wind turbines with hub height of 166m.  It is the V126-3.45MW model.  They also offer hub heights of 87m, 117m, 137m, 147m and 149m.  The tall hub heights are made possible by the large diameter steel tower (LDST) sections that are below the standard 3 sections of the tower.  LDST is made in 3 sections for ease of transportation.  The claim is hub height of 166m versus 117m results in 20% higher annual energy production.

This approach has some advantages over an alternate approach adopted by suppliers like Enercon who build a concrete base tower onsite, and then place the 3 sections of the steel tower on top of the concrete base.  The advantages of LDST is faster installation (2 days) and 99% recyclable (after decommissioning).  

Wind turbine integrated with pumped hydro

I just saw an innovative concept from GE: Storage of water below the wind turbine. Details are not very clear, but it looks like, there will be a 40m tall water storage unit below the wind turbine. The tower of the WTG is 138m and it sits on a 40m high water storage unit for a total hub height of 178m. GE is using the 3.4 MW WTG with rotor diameter of 137m. So the total height to tip of blade is 246.5m, which GE claims is the tallest wind turbine. There will be 4 such WTGs in the hybrid park. What is really unique is tight integration with hydro ... storing water under each WTG.

A 16 MW hydro generator sits 200m below the wind turbines; there is also a lake to store the water after it has gone through the hydro-generator. So the concept is when there is excess wind energy, water will be pumped from the lake to the water storage unit below the wind turbine, and when the electricity prices are high hydro power will be generated. An alternative concept may be more important--use of this scheme for secondary frequency response for grid stabilization during ramping and other random events caused by varying WTG output or varying load that would otherwise require expensive ancillary services.

It would be interesting to compare cost of wind-hydro versus wind-battery. Obviously this wind-hydro hybrid requires the stars to line up in terms the right location with good wind, hydrology and contour/elevation, while the wind-battery hybrid does not need any of this. Nevertheless, it would an interesting cost comparison.

For more details see

Flexible generation with Wind and Solar

City of Denton, TX has a goal of using 70% of electricity from wind and solar by 2019.  In order to achieve this goal it is buying 12 highly flexible Wartsila internal combustion-based gas generators with a total capacity of 225 MW.  These generators have quick start/stop times and high ramp rates, which are required when balancing wind and solar.  The claim is this allows wind and solar to act like base-load generators and the fossil-fuel generators to fill in the gap.  Interesting narrative.

For more information, see

However, i suspect, this configuration may not work for island grids, because of low overall grid inertia.  Denton must be getting its primary frequency control from ERCOT, but an isolated grid would need inertia--possibly from wind generators with synthetic inertia.

Solar energy prices: Low and going lower

I wrote about the falling price of wind energy, see  

Here are amazingly low prices of solar PV (

  1. Chile awarded a contract for 2.91 c/kWh for a 12 MW solar plant in the Atacama desert
  2. Dubai awarded a contract in May 2016 for 2.99 c/kWh for an 800 MW solar plant

An update on wind prices, the 2015 Wind Technologies Market Report from LBNL reports that wind PPA in interior of the US dropped to around 2 c/kWh in 2016, which is based on a sample of 2 projects totaling 207 MW.  Note this does not include the 2.3 c/kWh of production tax credits for 10 years.  So with the incentive the levelized revenue of these wind projects is below 4.3 c/kWh.

Wind PPA prices, cost and other 2015 data in US

The 2015 Wind Technologies Market Report from Lawrence Berkeley National Lab was released this month.  My takeaway from the report are:

  1. 8.598 GW of wind power was added in 2015. which amounted to $14.5 billion investment
  2. Wind power was 41% of electricity generating capacity additions in 2015
  3. Wind penetration is slightly above 5% of total electricity generation
  4. Project finance environment was strong in 2015: After-tax Tax Equity yield was about 7.5% and after-tax 15-year debt interest rate was about 2.5%
  5. In 2015, average rotor diameter crossed 100m.  Average hub height was slightly above 80m.  Average nameplate capacity was slightly above 2 MW
  6. Average specific power of wind turbines was about 250 W/m2
  7. Average capacity factor of wind plants in 2014 was close to 42%
  8. Average 2015 price of wind turbine was $1,100/kW
  9. Average 2015 total installed cost of wind power plant was $1,690/kW
  10. Average 2015 O&M costs were close to $8/MWh for projects built in 2014
  11. Average 2015 PPA was $38/MWh, based on sample of 6 projects of total capacity of 401 MW.  It was much higher than 2014 PPA of $23/MWh and 2016 PPA of below $20/MWh.  The 2016 sample was based on 2 projects.
  12. The forecasted amount of wind power additions until 2020 is 8 GW per year.


Cost of wind energy worldwide: Low and going lower


The the price of wind energy paid by utility buyers in the USA using 20 year power purchase agreements has give from: in 2006 the average PPA was 5c, in 2009 it was 6.8c in 2014 it was 2.3c and we do not have data for 2015, but it is probably lower.  This is lower than the wholesale price of electricity in the US.  Even with incentives like 2.3c production tax credit for 10 years the unsubsidized price paid for wind energy is less than 5c.  Even at such low prices about 8.6 GW were added in the US in 2015.


In 2015 Brazil saw competitive auction prices of wind of 4.78 US cents per kWh.

South Africa:

In 2015, South Africa wind energy was procured at 4.5 US cents per kWh, way below the price of new coal of 7 US cents.


In 2016, Egypt signed to procure wind energy at 4.7 US cents per kWh.


In 2016, Mexico had an auction of solar and wind.  394 MW of wind projects were awarded 5.5 cents to 4.2 cents per kWh.  What is really surprising is solar PV was awarded 1.8 GW prices came in at an weighted average of 4.5 cents, with lowest at 3.54 cents.

Progress of Wind Deployments in the Philippines

Wind power has grown tremendously in the Philippines.  The Energy Regulatory Commission started with a feed-in tariff (lets call it FIT-1) of P8.53 with quota of 200 MW.  This quota was exhausted quickly.  In October 2015, FIT-2 came into existence with tariff of P7.40 with quota of additional 200 MW.  At the time of approval of FIT-2, 144 MW was already commissioned and delivering power, that is for FIT-2 only 56 MW was left.  Last data, as of May 2016, indicates that 194 MW of the 200 MW is taken.  This rapid wind power development is a testament to clear and transparent FIT, the demand for wind power and readiness of private sector to develop and finance wind power.  The Philippines adopted an unusual approach of awarding the FIT after 80% electro-mechnical completion.