Standards Development

Scope

The proposal provides a systematic approach for the operation assessment, problem identification, and implementing repowering for the wind turbine generator systems (WTGS) in service, especially for the ones suffering from problems of low-efficiency and poor-competitiveness.

The approach and methods described in the proposal enable the stakeholders including WTGS owners, WTGS manufactures, and repowering providers to reach an agreement on the decision-making and goal-setting of the repowering activity.

This proposal:

a) specifies the methods for assessing theoretical energy production of WTGS and quantifying energy curtailments;

b) provides reference ranges for different lost production factors (LPFs) for identifying the most significant energy- curtailment cause;

c) requires the repowering activity be decided based on the analysis of LPFs, and perform safety verification before implementation;

d) provides requirements and guidance for the implementing WTGS repowering activities, as well as the post-repowering reviewing and report.

The proposal can be applied to the repowering of any number of WTGSs. The alteration of balance of plant (BOP) is beyond the scope of the document.

Comparing to IEC TS 61400-28, which emphasizing on the safety side of WTGS when extending its service life, the proposal focuses on the economic side of the WTGS. The two documents can be aligned or integrated with each other at the implementation level to achieve sustainable operation of WTGS.

Purpose

Background:

Since the first commercial wind farms were commissioned in the late 1970s, wind energy has become a mainstream electricity form, which now account for 10% of total electricity production capacity globally. Because the designed service life of wind turbine is normally 20 years, a large share of the already installed wind turbines are reaching or have reached the end of their operational lifetime. It is reported that the shares of wind power that has been in operation for over 10 years in Spain, Italy and Denmark are 85%, 66% and 63% respectively. The age -turbine shares of US and China are relatively lower compared to Europe, but their turbines operated longer than 10 years had reached 40.0 GW and 19.7 GW due to their large installed capacities by 2020. Repowering, which combines activities of upgrading, retrofitting, or refurbishing of the age wind turbines, will become a primary source of business for the wind industry across Europe, US and China in the late 2020s.

Repowering can enhance the productivity of existing projects and improve their profitability without expanding land use. Other benefits of repowering include lower implementation barriers through existing grid connection, long-term knowledge and record of available wind resource at a given site, relatively well-known environmental impacts and accustomed neighbors. With subsidy schemes and short-term market incentives, substantial repowering activities have been carried out in a few countries, from which some best practices can be gathered and empirical insights can be derived.

In the existing IEC 61400 series standards, IEC/TS 61400-28 Wind energy generation systems – Part 28: Through life management and life extension of wind farms address the life-extension of age wind power assets from a safety perspective, which specifies the requirements to ensure the structural integrity of assets of age wind power project and personal safety. However, aside from safety problem after long-time operation, some WTGS also show substantial reduction in the energy production and lose competitiveness. Without carrying out effective repowering activity, many of the age WTGS would have to be decommissioned. Thus, the repowering procedure of WTGS with relevant guidance and requirements should be specified by an international technical specification.

Purpose:

This TS is proposed to provide a guidance for stakeholders including owners, WTGS manufacturers, operators, and repowering providers of wind power projects to reach a consensus when evaluating the WTGS’ current performance and carrying out repowering activity.

The proposal can provide the following technical supports for repowering WTGS:

1. It will specify the determination of the theoretical energy production of the WTGS for the decision-making and goal- setting of repowering. IEC 61400-12 provides methods for measuring power curve and AEP of wind power projects. Because the aim of repowering is to explore the potential of the WTGS instead of maintaining the current energy production, the theoretical energy production needs be calculated. IEC 61400-26-1 only provides two possible methods for determining the potential energy production. The proposal will specify the approach on calculating the theoretical energy production based on the wind resource data and historical performance of WTGS;

2. It will propose the method for identifying the factors that causing the most significant energy production losses. IEC 61400-26-1 provides an information model which can be used to assess the production-based availability of the wind project caused by different site conditions. The proposal will provide empirical reference ranges for different lost production factors (LPFs). If the LPFs in the actual operation of the WTGS falls out of the reference range, they will be considered nonnegligible, and corresponding measures should be taken to mitigate their negative impact on energy production. A package of repowering measures will be provided for the stakeholders to develop repowering scheme;

3. Besides technical specification and requirements, the TS will establish a Plan-Design-Check-Action approach for repowering WTGS. In the Plan stage, the present operation situation of the WTGS is investigated and evaluated. Repowering scheme is developed based on the present situation in the Design stage. The safety of the repowering measures needs to be Checked through load and structural integrity analysis prior to implementation. After the repowering activities are put in Action, the improvements regarding the performance and profitability are presented and reported through before and after comparison.

The proposal enables stakeholders to carry out WTGS repowering through a systematic, data-driven and facts-based process. If the proposal is approved, we believe it will be a good supplement to the present methodology and technical system established by the existing IEC 61400 series standards.