Net load curves in California

CA is shooting for 33% RE by 2020.  This is likely to change the daily load curve.  With high solar penetration, in summer the load curve will match solar generation, while in winter, the net load curve will have two peaks--early morning and evening.  California Independent System Operator (CAISO) has initiated these to mitigate the impact (Source: North American WindPower, Jan 2015):

- Increased focus on flexible resources

- Implementation of a storage mandate

- Market design enhancements for intra-hour scheduling

- Creation of energy imbalance market

- Development of time-of-use pricing

- Assessment of demand response options

Popularity of Class III wind turbines

In 1999 more than 95% of the turbines installed in the US were Class I; in 2013, more than 65% of the turbines are Class III.  In the same period, the average specific power has dropped from more than 390 W/m2 to about 250 W/m2.  

Turbine manufacturers and independent engineers are approving Class III turbines for sites with Class II wind speeds & turbulence.  This is done after site-specific load analysis of the turbine.  The reasons are Class III turbines produce more energy because of larger rotor.

IEC 61400-1 specifies Class requirements for turbines in terms of a) Vref, which is onsite 50 year extreme wind speed computed based on 10-min average, and b) Iref, which is onsite turbulence intensity (TI) at wind speed of 7.5 to 8 m/s.  Part (a) determines Class I, II, III or IV, while part (b) determines A, B, C.  

Part (a).  Although the IEC standard specifies classification in terms of Vref, a more practical classification is in terms of annual average wind speed has evolved.  Vref is difficult to compute because unavailability of dataset of sufficient size, so for a quick classification average wind speed is used.  Note, the manufacturer or an independent engineer will still compute Vref before approving the turbine class.

Class I:  Wind speed up to 10 m/s

Class II:  Wind speed up to 8.5 m/s

Class III: Wind speed up to 7.5 m/s

Class IV:  Wind speed 6 m/s

Part (b).  Here X is I, II, III or IV.

Class X A:  TI less than 0.16

Class X B:  TI less than 0.14

Class X C:  TI less than 0.12

So a wind turbine classified as Class IIIA is designed for wind conditions: Average wind speed is less than 7.5 m/s, and TI is less than 0.16.


Source:  North American WindPower, January 2015.

YieldCo & MLPs: A new method to finance wind projects

About 8 YieldCos have been formed in 2014 as a way to tap the stock market for funds.  NextEra, SunEdison and others have created yieldCo companies, and sold a lot of their renewable assets to these new companies.  The new companies pay dividents to shareholders based on revenues from electricity generation.  Selling assets to YieldCos frees up a lot of capital for new RE investments.

According to Senator Chris Coons (D-DE) “By statute, MLPs have only been available to investors in energy portfolios for oil, natural gas, coal extraction, and pipeline projects. These projects get access to capital at a lower cost and are more liquid than traditional financing approaches to energy projects, making them highly effective at attracting private investment."  He continues, “Investors in renewable energy projects, however, have been explicitly prevented from forming MLPs, starving a growing portion of America's domestic energy sector of the capital it needs to build and grow.”

For more see


Wind generation in Denmark


Denmark generated a record amount of from wind in 2014, it amounted to 39% of electricity consumption in the country.  This twice the percentage 10 years ago., the Danish national transmission operator reports that Denmark is on track to reach 50% of electricity from wind by 2020.  The key challenge is to better use wind energy for heating.

For more details see,


Wind farm fined for bird deaths

PacificCorp Energy was fined $2.5m for bird deaths in Wyoming wind farms.  The US government alleged that "PacifiCorp Energy failed to make all reasonable efforts to build the projects in a way that would avoid the risk of avian deaths by collision with turbine blades, despite prior guidance from the U.S. Fish and Wildlife Service."


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Uncertain future of the first US offshore wind project

Two power companies terminated the PPA contract with Cape Wind, the wind project in Nantucket Sound which was projected to be the first offshore wind farm in the US.  The reason given: "failure to obtain financing and begin construction by Dec 31, 2014."


For details see,

China lowers Feed-in Tariff for wind

For details see,

FiT will be cut down by $0.02 for type 1, type 2 and type 3 wind regions, reducing electricity prices to CNY 0.49 ($0.078), CNY 0.52 and CNY 0.56 per kilowatt hour.

The CNY 0.61/kWh FIT will be unchanged in the type 4 region, which has low wind resources.