Viewpoint: Wind can be flexible - if given a reason

WORLDWIDE: Wind projects are often presented as a problem for the grid. They have different characteristics to conventional power stations: generation is variable and subject to a degree of uncertainty.

Projects are often comparatively small, quickly developed and far from load centres. Power-electronic interfaces provide new capabilities not available from conventional synchronous generators.

At low penetrations, these differences are largely unproblematic for the network, although congestion may be experienced in local hotspots. But as the amount of wind on the grid increases, they introduce a dual challenge: a rise in costs to resolve multiple technical issues relating to the grid; and a decreasing economic value of wind projects as production approaches or exceeds demand at some times of the day or year.

In future, these two drivers could bring a fundamental shift in how we develop and operate wind projects. Industry will increasingly move from focusing on the cost per kilowatt hour, to also considering when and where that kilowatt hour is generated.

The good news is that, with the exception of providing energy on demand, wind can do anything a network operator wants - and often faster or more accurately than conventional generation.

Across the project lifecycle, there is potential for developers to make decisions in different ways. For site selection, developers may choose locations where their project can benefit most from providing services to the network, such as voltage control. Or they may choose to accept a "curtailable" connection in an area where the grid is weak, when they know that periods of high curtailment risk correlate with low wind production.

Turbine capabilities

When choosing the turbines, developers might select, for instance, turbines with capabilities to provide grid ancillary services, such as synthetic inertia - where a wind-turbine controller can allow an increase in power output for a matter of seconds during a change in grid frequency. In operation, during periods of low electricity demand overnight, project operators may be able to reduce their output in order to make the "headroom" to provide frequency response, thereby avoiding the need for conventional thermal generation to run at low output. Of course, since these decisions are typically associated with increased levelised costs, they only make sense where wind projects can deliver flexibility more cheaply than alternatives.

The optimal portfolio of flexibility options will vary substantially by market. In many cases, measures such as demand response and interconnection to deliver power further afield will be more cost-effective, as shown in scenario analysis for the European Commission by DNV GL, Imperial College and NERA Economic Consulting. But it remains likely that in some circumstances, particularly on more isolated grids, wind projects will provide a competitive contribution.

How to do it

Technology is not the limiting factor. Although wind's flexibility potential is significant, in most markets project developers and operators are not given a reason to use it. The trick is to structure markets and regulation so that project benefit is aligned with grid benefit. The European Wind Energy Association recently published a report on how wind can provide grid support services for frequency, voltage and system restoration.

At a broader policy level, there will be a transition away from fixed feed-in tariffs and towards more market-reflective support mechanisms, to better reflect the differing value of kilowatt hours generated at different times of the day. These mechanisms will need to be structured carefully to make project risk acceptable.

Achieving change will not be simple, due to the sheer number of stakeholders involved. It is not easy for turbine manufacturers to reach out to every network operator where turbines are sold. And network operators that deal with a few key players in conventional power generation may feel overwhelmed by the number of manufacturers in the wind business.

When opening up these communication lines, one key principle must hold: reforms to cater for the grid must not place wind projects at a disadvantage. Rather than seeing wind power as the problem, regulators and network operators should ask: how can we unlock the flexibility capabilities of wind so that it becomes part of the solution, alongside other measures such as demand response and storage? That this question is becoming relevant is a success in itself. The wind industry's horizons are broadening, from optimising turbines, then wind farms, and now to optimising the power system.

Fliss Jones is leading DNV GL's Low Carbon Future team's research on grid integration of renewables, based in Norway.