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Lorne Street, Leith, Edinburgh

Lorne Street, 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 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 property on Lorne Street is an L-shaped building, containing eight blocks of flats. The front elevation of the building faces 27° Southwest and is large enough to accommodate PV panels. The area above one block (number 34) is 64 though this is interrupted by a pitched section above the main entry door.

The annual energy consumption in the communal areas of number 34 has been extracted from electricity bills from 2010 and 2011 as provided by Port of Leith Housing Association. The total annual consumption is calculated as 2,420kWh. It is hoped that a PV installation could reduce the consumption of grid electricity.

 

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 Lorne Street flats, three options were analysed.

  Option 1 Option 2 Option 3
Solar Panel Technology Monocrystalline  Monocrystalline Monocrystalline
Number of Modules 16 16 16
Power (wp) per Module 250 230 240
Total Power (kWp) 4.0 3.7 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) 3,076 2,923 3,005
Specific Production (kWh/kWp/y) 769 794 782

 

Option 3 was the preferred solution as it had the best cost to output ratio. This PV installation has an estimated cost of around £13,000 including tax and installation costs, with payback expected in year 13 or 14. In the 25 year FIT scheme, the installation could generate around £30,000, plus savings on electricity bills, as the system can produce all of the communal energy required in number 34. Around 37 tonnes of carbon dioxide would be saved compared to using grid electricity.

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.

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Case Study

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