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Albert Street, Leith, Edinburgh

Albert 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 on Albert Street, Leith. 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 Albert Street comprises five storeys, housing a number of flats. It was constructed in the late 1990's and has a mansard style roof.

The roof area suitable for PV panels is at the rear of the building, on the pitched section of the roof. This part of the building is orientated southwest, and has a tilt of 35º. There is no potential shading from surrounding buildings. The useful area of roof is 72m².

The annual energy consumption for the communal areas in the building has be calculated from electricity bills. The total annual consumption is 7,500kWh, at a cost of £930 per year.

 

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 Albert Road flats, three options were analysed.

  Option 1 Option 2 Option 3
Solar Panel Technology Monocrystalline Polycrystalline Monocrystalline
Number of Modules 36 36 36
Power (wp) per Module 255 255 260
Total Power (kWp) 9.2 8.1 9.4
Number of Inverters 1 1 1
Size (kW) 9.0 8.0 9.0
Number of Strings 3 3 3
Produced Energy (kWh/y) 7,441 6,539 7,565
Specific Production (kWh/kWp/y) 811 807 808

 

Option 3 was the preferred solution as it was capable of producing the most energy over a year, 100% of the building's communal annual electricity requirement in the first year, though over time the efficiency of the PV panels will decrease and they will produce less electricity.

This PV installation has an estimated cost of around £31,000 including tax and installation costs, with payback expected in year 13 or 14. In the 25 year FIT scheme, the installation could generate £50,600, plus savings on electricity bills of around £31,400.

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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