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Re-Tek, East Kilbride

Assessment of renewable energy technologies suitable for an office and warehouse facility


This case study provides an assessment of the potential renewable energy technologies which would be suitable for an office and warehouse facility in East Kilbride. The company, who recycle electrical and IT equipment, wished to reduce their energy costs and environmental impact.


The objectives of the assessment were:

  • Conduct an evaluation of the buildings current energy use
  • Evaluate the best renewable technologies suitable for the site and building restrictions
  • Indicate the investment required for the technologies and the associated pay back periods
  • Assess how current and future funding mechanisms may benefit the company
  • Advise on the next steps for adequate design and installation of renewable technologies.


The company employs 18 people and the warehouse and office facilities cover 1,900m². The building is situated on the outskirts of East Kilbride.

Initially, an assessment of the energy use within the warehouse and offices was conducted. This highlighted the following key areas of consumption:

  • Computing equipment (used to erase data from IT equipment before it is recycled)
  • Ventilation for the computing equipment
  • Forklift charging
  • Machinery for separating equipment elements
  • Warehouse space heating (warm air heaters)
  • Office lighting and space heating (radiators linked to gas boiler).


Re -Tek - Energy Consumption

Electricity demand is fairly constant throughout the year (average monthly consumption = 4,950kWh), but as can be expected the heating season (October to March) sees the greatest gas consumption, averaging 15,400kWh per month.

The assessment first suggested ways of reducing energy consumption, such as producing and circulating a company energy policy, sub-metering, checking meter readings are correct and good housekeeping.

The assessment identified some renewable technologies which would not be suitable for this particular building (hydroelectric, ground and air source heat pumps) before analysing in detail the following technologies:

  • Solar PV panels
  • Solar thermal panels
  • Wind turbines
  • Biomass and combined heat and power (mini-CHP)


Solar PV

Design software was used to identify the potential for solar PV to contribute to energy generation at the warehouse facility. In this location, the most efficient direction for PV panels to face is between South-East and South-West and with a tilt of 30° from the horizontal. The current warehouse roof tilt is 6°, but racking and frames can be used to increase this.

The software provided analysis of two different PV specifications. Both considered the most appropriate size, facing direction and cost of the PV panels and their installation. In addition, the available feed-in tariffs were calculated to estimate a payback period for the technology.

The two options are shown in detail below.

PV Panel Options
  Option 1 Option 2
Roof Tilt / Azimuth 20° & -60° SE 20° & -60° SE
Technology Type Polycrystalline Monocrystalline
Number of modules 51 162
Power per module 190Wp 280Wp
Total power 9.7kW 45.4kW
Inverter size 8kW 40kW
Energy Produced 6,944kWh/yr 21,133kWh/yr
Specific Production 717kWh/kWp/yr 708kWh/kWp/yr
Generation tariff 16.8p/kWh 15.2p/kWh
Capital cost £30,000 £75,000
Payback 13 years 13 years

Payback is achieved through FITs and savings to energy bills. NOTE: the FIT quoted here were correct when the case study was written.

Wind Turbine

Average wind speed at the location of the Re-Tek factory as provided by the DECC NOABL database, are 6.1m/s at 10m above ground level and 6.9m/s at 25m above ground level. Two different wind turbines were assessed, a 5kW and a 10kW.

Wind Turbine Options
  5kW Turbine 10kW Turbine
Height 9m 12m
Estimated Output (kWh/yr) 15,305 34,518
Total Capital Investment £22,500 £45,000
FIT available 28p/kW 28p/kW
Income from FIT £3,428 £7,732
Income from export tariff @3p/kWh £92 £207
Savings on electricity bills (12p/kWh) £1,837 £4,142
Total savings/income per year £5,357 £12,081

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Solar Thermal

RHI (Renewable Heat Incentives) is paid to producers of heat through renewable (e.g. non-fossil fuel) means. Solar thermal panels attract RHI payments of 89p/kWh, thus the scheme detailed below would be paid back in 13 years. These evacuated tube panels would be positioned as the PV panels, and would offset around 10% of the warehouses gas consumption (of approx. 100,000kWh).

No. of panels 10
Output (kWh/yr) 8,965
Capital investment £10,944
Income from RHI/year £798
Savings from gas bills/year @3p/kWh £269
Total savings/income £1,067


A 30kW biomass boiler with efficiency of 90% was also specified for Re-Tek's warehouse facility. The table below outlines the cost, payback and output of the specified system.

Estimated Output (kWh/yr) 72,000
Capital investment £24,000
RHI available (average) 5p/kWh
Income from RHI/year £3,766
Savings from gas bills/year @3p/kWh £2,160
Cost of biomass/year £2,880
Total savings/income (minus on-going costs) £3,038
Payback 8 years


For all the technologies considered, it is important to consult a Microgeneration Certification Scheme (MCS) accredited installer. They will consider the most suitable technologies, help with design and identify any constraints associated with the site.

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The initial energy audit showed that Re-Tek's warehouse and office facilities consumed over 160,000kWh of energy per annum (gas and electricity), costing the business over £13,000 and generating 64 tonnes of CO2.

The study first highlighted some energy saving measures and techniques that could be adopted by the company, before presenting analysis of a range of renewable technologies that would be suitable for producing energy at the warehouse facility.

As energy price rises may occur, and as the company wishes to reduce its impact on the environment, it is likely they would benefit from a suite of renewables. A summary of the analysis of each technology is shown below.

Different combinations of the detailed technologies could be used. Larger systems will have a greater initial capital outlay, but also greater production.

Before installing any renewable technologies, it is advised to gain advice from the MCS Scheme.

Technology Type

Estimated Output


Payback period


Energy savings

(gas - %)

Energy savings

(electricity - %)

CO2 savings per year


Solar PV (10kW) 7,000 13 - 12 3.7
Solar PV (45kW) 32,000 13 - 54 16.8
Wind 5kW 15,000 4 - 25 8
Wind 10kW 35,500 4 - 60 18.6
Solar Thermal 9,000 13 9 - 1.7
Micro CHP 5,000 4 - 8 2.6
Biomass 72,000 8 70 - 1.7
Total 103,500 (max) - - - 53.1 (max)


Scottish Energy Centre, Edinburgh Napier University

CIC Start Online

Re-Tek (UK), Ltd.

Microgeneration Certification Scheme


Resource Efficient Scotland supported the preparation and presentation of this case study for the Retrofit Scotland website.

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