Carbon emissions reductions in cities through large scale PV deployment

Driven by the UK national target of reducing carbon emissions by 80% by 2050, many UK cities including London, Southampton, Birmingham, and Liverpool have published their own emission reduction targets. Realising these targets... [ view full abstract ]

Driven by the UK national target of reducing carbon emissions by 80% by 2050, many UK cities including London, Southampton, Birmingham, and Liverpool have published their own emission reduction targets. Realising these targets is through the development of low carbon strategies that can be achieved within the city border. Such strategies will require local authorities to conduct appropriate assessments of energy resources whilst addressing the challenges faced with the densely populated urban areas. In this work, the city of Portsmouth in the South of the UK was selected as a case study due to its high population density and appropriate building stock characteristics. Figure 1 shows the CO2 emissions of Portsmouth for the period 2005 to 2015, which showed a 37% drop in emissions from 6.5 tonnes to 4.1 tonnes per person.

However, as an island city, Portsmouth is faced with geographic limitations, causing its building stock to evolve with significant structure diversity during urban development. Therefore, the deployment of renewable energy systems, such as rooftop solar photovoltaics (PV), would face additional challenges caused by irregular building structure and inter building shading within a high dense urban environment.

To provide a clear understanding of the potential of building integrated and attached solar PV, a city-wide building model was developed to automatically identify suitable areas for the installation of solar PV. The model takes into account both engineering and economic assessment for each individual buildings in the city, providing more realistic estimates of power production in the context of densely populated areas. The model was applied to all buildings in Portsmouth (number > 111,000) and considers different scenarios based on roof areas, costs, and PV system capacity. The result from the central scenario indicates that 18,654 buildings (17%) in Portsmouth are suitable for rooftop PV. If the model estimated areas were fully utilised this could provide the city with around 54 MWp installed capacity. These results as well as the implication to cost and carbon emissions are also discussed in the paper.