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Ferry Road, Leith, Edinburgh

Ferry Road, Leith, Edinburgh

Solar Photovoltaic (PV) Feasibility Study for Housing Association Homes

Overview

This case study examines the possibility of retrofitting solar PVs to an existing sheltered housing complex on Ferry Road, which is located in the Leith conservation area in the City of Edinburgh. Benefits of this low & zero carbon technology include reducing electricity costs for the tenants, tackling fuel poverty, whilst at the same time reducing the carbon dioxide emissions. 

This study investigated the potential for PV panels and assessed the following:

  • Location and type(s) of PV panels to maximise solar gain, including output and returns
  • Benefits of Feed-in Tariff in relation to provision of solar PVs
  • Restrictions on PV placement on buildings in conservation area
  • Changes to the government’s Feed-in Tariff scheme, and introduced stipulations

Approach

Technical scope of study

The property on Ferry Road comprises of 35 self-contained one and two-bedroom flats, managed by a concierge service. It was constructed in 1989, and consists of a four-storey and a three-storey section, resulting in a stepped facade.

As the property is within the Leith Conservation Area, planning permission would be required to install PV panels on the roof. For the purposes of the study, it is assumed that by locating the panels away from the principal location so they are not visible from street level. The roof has two pitched sections, with a walkway access between.

This restriction means that only the sections PV01 and PV02 (see image below) are suitable for PV panels. PV01 is orientated 15° southeast, and the area PV02 is 60° southeast. Potential shading may occur from the other pitched roof section, so panels will have to be located to avoid this. This has resulted in a useful area of roof of 45m².

The annual energy consumption in the sheltered accommodation at Ferry Road has been estimated from electricity bills from 2010 and 2011 which were provided by Port of Leith Housing Association. The total annual consumption between August 2010 and August 2011 was 43,039kWh. It is hoped that a PV installation could reduce the consumption of grid electricity.

 

Ferry Road

Satellite images of Ferry Road, courtesy of TerraMetrics Map data ©2012 Google

 

Cost Analysis

The cost analysis of the solar PV systems in this report takes into consideration and evaluates the following information: 

  • Capital cost of materials
  • Labour to install such panels
  • VAT on labour & materials
  • Yearly estimated maintenance fee
  • Estimated inverter replacement (once every 20 years)
  • Decrease in solar panel efficiency
  • Feed in Tariff rate and its yearly increase in line with the Retail Price Index (RPI)
  • Savings made on electricity bill, based upon electricity price per kWh and its estimated increase with inflation
  • Electricity export at £0.31/kWh (if applicable)

A full breakdown of energy and income generation, cost of systems, and carbon dioxide savings are detailed in feasibility report.

Performance

The analysis process included modelling a number of PV panel sizes and technologies along with inverter size options for the building. The modelling mechanism takes influence from the buildings orientation, roof tilt, size of available roof area and any shading that impacts upon the roof. Each PV and inverter option was simulated to obtain a yearly output of electricity and the number of panels required to achieve different output levels. The selection of the ‘best fit’ PV system was based upon the annual kilowatt/hour output to cost ratio.

For the Ferry Road sheltered accommodation, three options were analysed.

  Option 1 Option 2 Option 3
Solar Panel Technology Monocrystalline Monocrystalline Polycrystalline
Number of Modules 16 16 16
Power (wp) per Module 240 250 240
Total Power (kWp) 3.8 4.0 3.8
Number of Inverters 1 1 1
Size (kW) 3.8 3.8 3.8
Number of Strings 2 2 2
Produced Energy (kWh/y) 3,010 3,122 2,916
Specific Production (kWh/kWp/y) 784 780 759

 

Option 2 was the preferred solution as it was capable of producing the most energy over a year, around 7% of the building's annual electricity requirement. This PV installation has an estimated cost of around £13,900 including tax and installation costs, with payback expected in year 13 or 14. In the 25 year FIT scheme, the installation could generate £26,100, plus savings on electricity bills of around £13,000

Lessons

One of the main drivers for making the investment for PV panels is the Feed in Tariff. Without this incentive for the production and export of energy, the pay back of such installations would rely only on the energy savings from the installation. It is for this reason that any changes to these tariffs can substantially affect any decision to invest in renewable technologies. This is further discussed in the report (downloadable on the right of this page).

PV systems are often sized or specified based on the amount of modelled or simulated energy required over the course of a year. It is important to appreciate that the PV system without a storage capacity i.e. batteries, will only generate power during daylight hours. Therefore, the calculation comparing the PV energy generation and the buildings energy demand should be granular enough to differentiate the day and night time energy demand profile.

 

It is of paramount importance to have an appreciation of the conservation zones and any listed building status. Early discussions with the local authority will allow for the best siting of PV panel installations during the design stage.

 

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