Light and power

By Rebecca Knight and Paul Macrae

Wind power is making a massive contribution to the generation of renewable energy, but what are the implications for how turbines are lit?

To achieve net zero, there will need to be a considerable increase in the number of on and off-shore wind turbines. Landscape professionals need to understand the potential impacts of these structures and how to minimise adverse effects. As wind turbines have increased in size, so has the need for lighting to ensure the safety of air traffic. LUC estimates that there is over 11GW of onshore wind development in the planning system, most of which would require safety lighting.

There is a statutory requirement for lighting of wind turbines of 150m or more above ground level. (1) Wind turbines below 150m are not required to be routinely lit for civil aviation purposes, but aviation stakeholders (including the Civil Aviation Authority, CAA) may make a case for aviation warning lighting where a structure is considered a significant navigational hazard. The Ministry of Defence (MOD) may also specify lighting, although in the interests of public amenity they will seek to specify InfraRed (IR) lighting.

Light pollution is a recognised problem in the UK, and the value of night skies has been brought to attention in part by the Campaign to Protect Rural England’s (CPRE’s) Night Blight campaign, and its associated mapping. (2) For wind farms requiring lighting, effects on dark landscapes can be of particular concern in more remote areas, resulting in delays to permissions.

The need to accurately model and carefully assess effects is especially important in the UK’s darker, more sensitive and wilder landscapes. NatureScot has set out guidance on assessing lighting effects, (3) in which they suggest an appropriate scope for landscape and visual assessment of turbine lighting, including night-time visualisations “from a limited / proportionate number of representative viewpoints”. These visualisations, together with lighting intensity Zone of Theoretical Visibility (ZTV) mapping, can be useful to inform an understanding of the effects of turbine lighting.

As for any effects on the environment, mitigation should be considered to prevent, avoid, reduce or offset any significant adverse effects. As the Institute of Lighting Professionals states “Good lighting practice is the provision of the right light, at the right time, in the right place, controlled by the right system”. (4) This is useful advice to inform appropriate mitigation. For wind turbine lighting, mitigation measures may include:

• Using InfraRed lighting where possible (this is only currently an option for turbines below 150m above ground level)

• Limiting the highest intensity of visible light to the horizontal plane and restricting it in other planes

• Minimising the number of visible lights required in agreement with the CAA

• Reducing the intensity of lights in periods of good meteorological visibility

• Using ‘smart’ transponder-based demand-controlled aviation lights that only switch on when aircraft are detected within a particular airspace around the wind farm (known as an Aircraft Detection Lighting System, or ADLS).

References

1) As set out in the UK. Air Navigation Order (ANO) 2016, Article 222 which has been translated into the Civil Aviation Authority’s (CAA) Policy Statement on the lighting of onshore wind turbines (2017).

2) https://nightblight. cpre.org.uk/

3) NatureScot (2020) General pre-application and scoping advice for onshore wind farms: Guidance, Annex 2.

4) https://theilp.org.uk/ ilp-guidance-note-onobtrusive-light-hasbeen-revised/