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Sandport Way, Leith, Edinburgh

Sandport Way, Edinburgh

Solar Photovoltaic (PV) Feasibility Study for Housing Association Homes

Overview

This case study examines the possibility of retrofitting solar PVs to an existing block of flats in the Leith area of 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 building at Sandport Way is a curved building which houses five blocks of flats. Tthe property is within the Leith Conservation Area, and as such 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 elevation so they are not visible from street level, that planning permission would be given.

The building curves (as shown in the image below), and as such it was decided to divide the study into five areas (PV01 - PV05). The orientation of each section is:

  • PV01 - 25° southwest
  • PV02 - 5° southeast
  • PV03 - 25° southeast
  • PV04 - 40° southeast
  • PV05 - 40° southeast

The roof pitch (on the rear part of the split roof) is insufficient for the optimum gain from the PV panels, so additional framing would be required. The total area of PV panels which can be placed on the building is 156.4m².

The annual energy consumption in the communal areas of the five blocks has been extracted from electricity bills as provided by Port of Leith Housing Association. The total annual consumption and associated cost is:

  • PV01 - 210 kWh/yr  (£2,516)
  • PV02 - 41 kWh/yr  (£487)
  • PV03 - 44 kWh/yr  (£527)
  • PV04 - 47 kWh/yr  (£566)
  • PV05 - 44 kWh/yr  (£527)

It is hoped that a PV installation could reduce the consumption of grid electricity.

 

Sandport Way

Sandport Way - Satellite image, 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.

  • PV01 - 25° southwest
  • PV02 - 5° southeast
  • PV03 - 25° southeast
  • PV04 - 40° southeast
  • PV05 - 40° southeast

Performance

The analysis process included modelling a number of PV panel sizes and technologies along with inverter size options for the five areas of 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.

The table below shows three options analysed which would be suitable for the area PV03.

  Option 1 Option 2 Option 3
Solar Panel Technology Monocrystalline  Monocrystalline Monocrystalline
Number of Modules 14 14 14
Power (wp) per Module 250 255 240
Total Power (kWp) 3.5 3.6 3.4
Number of Inverters 1 1 1
Size (kW) 3.5 3.5 3.0
Number of Strings 1 1 1
Produced Energy (kWh/y) 2,731 2,739 2,651
Specific Production (kWh/kWp/y) 780 767 789

 

A fourteen panel system would cost £12,400, including labour, framing and VAT, and the analysed systems have the potential to generate up to 63,900kWh of electricity, £22,800 from the FIT, £11,800 through savings on electricity bills and 33 tonnes carbon dioxide in a 25 year lifespan. Payback would be expected in year 14.

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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Case Study

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