In 2016, Fox Lloyd Jones commissioned Pager Power Ltd to investigate and assess the possible effects of glint and glare from a proposed sculpture on a retail development to the north of Newcastle. The 5 metre sculpture is known as Silverlink and marks the entrance to the retail development.
The sculpture consists of a three dimensional array of irregular triangles made from mirror polished stainless steel. There was a concern that reflections from the Sun, vehicle headlights and led lighting designed to illuminate the sculpture could cause an unacceptable distraction to road users.
Undertaking a glint and glare assessment for ground level receptors such as roads and dwellings is a common request for various forms of development. Typically assessments are required for Solar PV developments and large glass faced buildings – particularly those near airports or railways.
Less frequently assessments can be required for other reflective structures such as sculptures and chimneys. This particular requirement – to assess the impact of a complex highly polished sculpture – required custom software to be developed so that the impact of direct solar reflections could be quantified. The figure shows the location of the sculpture (marked as a blue dot) overlaid on aerial photography – prior to construction of the retail development.
There were a number of challenges associated with this project:
- The complex shape of the sculpture
- The potential for direct solar reflections from the sculpture’s highly polished surfaces
- The sculpture’s proximity to a road junction
- The complexity of modelling direct solar reflections generally
- The lack of specific guidance on glint and glare issues
The figure below shows a 3D computer model of the sculpture which was built for specifically for this project:
The following methodology was adopted.
- Considering relevant guidance and studies on glint and glare.
- Establishing sculpture coordinates and dimensions.
- Identifying sculpture vertices.
- Identifying sculpture surfaces.
- Building a 3D computer model of the sculpture.
- Establishing sculpture location, elevation and height.
- Establishing sculpture orientation.
- Establishing sample vehicle locations.
- Building a schedule of sculpture reflective surfaces.
- Modelling direct solar glint and glare for sample vehicle locations and all reflective surfaces.
- Considering the reflectivity of the sculpture’s surface.
- Calculating the likely duration/area of any direct reflection effects.
- Assessing the likely overall impact of direct solar reflections.
- Assessing the likely impact of reflections from vehicle headlights.
- Assessing the likely impact of reflections from ground level LEDs.
- Comparing the likely impact of reflections from the sculpture with the impact of other common reflections.
- Determining the overall glint and glare impact of the sculpture.
Times and dates of direct solar reflections were predicted for specific observer locations. Results for one observer are reproduced in the figure below
The assessment was made using computer modelling of the Sun’s trajectory and the reflectors to determine where and when direct solar reflections could occur. Modelling of the proposed sculpture was more complicated than modelling a solar photovoltaic development because of the irregular surfaces which have different 3-dimensional orientations and heights. It was therefore necessary to build a custom computer model of the sculpture to determine the relevant orientation and position information for the individual reflecting surfaces.
Once the orientation and position of the surfaces had been determined modelling of direct solar reflections was undertaken for nine sample locations within the retail development car park and on local approach roads.
The analysis showed that direct solar reflections from the sculpture will be experienced at all locations at various times and dates. The intensity of reflections will not be magnified because the sculpture does not have curved convex surfaces. The intensity of reflections will actually be diminished because mirror polished stainless steel (like any reflector) only reflects a proportion (typically 62%) of the incident light energy.
The likely glint and glare effects will be comparable to those regularly experienced in a normal driving environment. Therefore no requirement to modify the design, location or orientation of the sculpture has been identified for glint and glare reasons. The results of Pager Power’s Glint and Glare Assessment were accepted by the local planning authority with the local planning authority subsequently awarded planning permission for the retail development and sculpture.