Bristol, UK

Hammerson is a major British REIT with retail assets across the UK, France & Ireland.

PROJECT GOAL

Hammerson has had a 2030 net positive commitment in place for CO2 since 2017. This has led to a huge drive to try and reduce the emissions associated with their assets and they therefore asked Longevity to analyse the PV potential of Cabot Circus, one of Hammerson’s flagship shopping centres in Bristol.

CHALLENGE

Lack of single, central rooftop across the centre: There were multiple logistical challenges associated with installing solar PV at Cabot Circus. The Centre is built on three multi-level pedestrianised streets flanked by shops. The streets, and the square where they converge, are covered by several large, dramatic glass-panelled roofs. This created challenges for the installation of solar PV as there is no single expanse of roof that covers the entire Centre, as you would typically expect.

Challenging existing electrical infrastructure: Longevity identified Block 6 as the most suitable roof for solar PV. However the two main incoming electricity meters to the Centre were located a considerable distance away, and there were no substations nearby with sufficient spare capacity to take the required electrical load. Furthermore, there was an existing 40 kWp solar PV system located on Block 4 that had previously been used by a tenant that needed to be remediated and redirected to the landlord supply.

SOLUTION

Longevity conducted several scenario analysis of potential system set-ups: The team assessed several potential scenarios, including different pitches and panel sizes to establish the optimal solution in terms of kWh/m² and £/kWh. Block 2 and Block 6 were identified as the most suitable roofs for the installation of solar PV. Block 6 has a metal seam roof, split by parapets of various sizes. The pitch itself is only 5 degrees, and we therefore assessed the potential of enhancing the pitch and therefore increasing the yield of each of the panels. However while each panel was able to produce more electricity in this scenario, the number of panels that could be installed was reduced, due to the gaps required to account for the increased shading caused by the panels. At the same time, the increased costs that would be incurred from the equipment required to enhance the pitch led to a less favourable £/kWh.

Weighing the costs and benefits, Longevity maximised the number of installed panels across the roof by installing them flush with the roof. This means that the O&M costs are slightly higher as the self-cleaning properties of the panels are inhibited when they are installed at a pitch of less than 10 degrees. However, even with these increased O&M costs, this was still the optimal solution with a more favourable IRR.

Longevity developed a bespoke installation plan across two separate PV systems: Longevity also employed a specialist cable contractor to run a large cable over 100 metres to ensure that the system could feed into the appropriate incoming meter. To reduce costs, the system was split into two distinct systems to allow us to utilise the spare capacity on the existing distribution board, and avoid costly switchgear upgrades that would have reduced the financial attractiveness of the project for the client.

Longevity developed and led a tenant engagement exercise to get all tenants onboard: The team liaised with multiple tenants to assuage their concerns surrounding several issues, including potential roof damage and acoustic pollution associated with the solar PV system. After several discussions and the presentation of a range of different material and case studies, all tenants came to appreciate the limited risks and significant benefits of the project.

BENEFITS

Following our installation, Hammerson was able to:

• Reduce the CO2 emissions of Cabot Circus by 15% compared to the previous year.

• Establish an IRR of 14%, taking into account all O&M costs and future inverter replacement costs.

• Enhance the brand of the Centre by installing one of the largest rooftop solar PV installations in Bristol, and one of the largest across a shopping centre in the UK.

• Engage with tenants on a positive initiative that reduces their collective CO2 emissions and provides them with a good source of marketing, at no additional cost.