Case Studies

Wind Energy - SW UK
Energy use at this pharmaceutical site in the rural south west of England is made up of electricity for site plant and office operational requirements, natural gas and fuel oil which are used building heating and steam generation process use. Based on 2007 data the site consumes 4,884,995kWh of electricity a year. There are also 122,000litres of fuel oil consumption which equates to 142,740kWh and an additional 116,095kWh of natural use. Half hourly data indicated a site base electricity load profile of ~520kW.

The identified scheme considers installation of 2 number 2 megawatt wind energy generator (WEG) turbines to generate electricity for site demand and export to the grid or other end users. It has been identified that annual site electricity demand is ~ 4.8GWh/year and that potential combined WEG output would be ~7.4GWh/year.

Taking this into account ALL on site demand can be met with notional WEG output with a further ~2.6GWh of electricity being available for export to the grid or potentially a private wire system to other industrial estate end users.

For the purposes of economic appraisal savings identified are calculated based on the combined value of displaced electricity (at 10p/kWh current price), Renewable Obligation Certificates (ROC’s) revenue at £34.30/MWh and the value of grid export electricity which has been estimated at a value of 5p/kWh which is thought to be representative of potential market acceptance.

Two implementation options are recommended for consideration, those being option 1 to enter into a long term design build and operate agreement with a wind energy contract entity whereby a pence per kilowatt hour (p/kWh) charge mechanism would apply and option 2 where the company would realise full capital investment for erection and operation of wind turbines at their site.

There is an identified cost benefit of £155K a year saving for option 1 and £563K per annum saving for option 2 with an estimated payback of 6.92 years against an estimated total capital investment of ~£3.9 million.

Indicative carbon dioxide savings from displaced grid supplied electricity by wind turbine generation output are 3,186.3 tonnes a year.

CHP - SW UK
This company is a multi-national chemical and pharmaceutical business who has an aspiration to deliver a reduced energy cost base whilst reducing their carbon footprint as part of business plan and Corporate Social Responsibility (CSR) objectives. In addition the site has historically experienced unplanned power outages from grid supply resulting in a significant loss of sales; taking this into account the study has also reviewed security of supply as part of potential CHP business need objectives.

Two implementation options have been identified as part of the CHP feasibility study; they are shown below:

Option 1 to utilise a biodiesel fuelled CHP installation 
Option 2 to implement a natural gas fired Spark Ignition Reciprocating engine CHP with heat recovery steam boiler for process distribution.

Both options identified are based on a ~1 MW electrical and ~1.3 MW thermal installation as calculated from average current and future predicted process steam demand at the site.

At the higher level at present only Option 2 would be economically viable as a potential CHP installation technology, which if implemented could deliver a simple payback of ~5.55 years. Alternatively it is estimated that a Third Party Design, Build, Finance and Operate CHP contract would cost ~£84/MWh including gas fuel costs, however at present calculations indicate a net increase in annual costs for the site of ~£75K a year. It should be recognised however that this is an estimated figure and further commercial competitive tender evaluation is recommended.

In summary, overall saving opportunity identified of £149,498 is the product of grid supplied electricity and Climate Change Levy cost avoidance, plus thermal cost avoidance minus gas consumption cost for CHP and maintenance cost for CHP.

Opportunities for Waste Utilisation - Northern Ireland
Option 1 – Installation of a 25 ktpa Dry AD Fermentation Process with CHP Energy Recovery
This option would require installation of a suitable Dry AD Fermentation plant capable of treating up to 25 Ktpa of organic waste input. Appendix 1 details key process inputs and outputs which have been modelled on assumed data and plant performance parameters. At the higher level the plant would typically require a ~ 2 hectare area footprint including upstream waste handling, installed AD's, a CHP unit of ~200 KWe capacity and downstream composting before final disposal offsite. It is estimated that this solution would have a capital cost of ~£1.4 million and achieve saving of ~£302K a year.
Option 2 – Installation of a 45 ktpa Wet AD Process with CHP Energy Recovery
The wet AD option requires upstream brown bin management to achieve appropriate segregated food and kitchen organic waste input through municipal authority combined waste management. The brown bin waste would be collected every week in 25 litre containers from domestic and appropriate commercial sources having a dry solids content of ~3-6%. The key factor in realising a successful project is provision of a homogenous material with modelled plant performance and assumed input
data detailed in Appendix 1. It is estimated that an installation could deliver ~11,549 MWh of electrical output and ~15,000 MWh of thermal output. Estimated digester retention time is approximately 15 to 20 days with mesophilic operation. Capital costs of ~£6.7 million have been identified with annual saving including NI ROC's estimated at ~£1.67 million a year with this figure potentially increasing if planned ROC banding criteria are implemented in 2009 which would give AD technologies 2 ROC's for every MWh of output.
Option 3 – Installation of 2 MW Thermal Biomass Boiler
This option would utilise existing wood waste biomass as a biomass boiler fuel to provide thermal energy to an appropriate site or industrial estate. Appendix 1 provides modelled data based on a fuel input of ~5 ktpa to produce ~17,000 MWh of thermal output. Revenue savings are calculated from an indicative biomass gate fee of £25/tonne for NWP, with the operational user potentially avoiding heating gas costs of ~£690K a year based on a gas cost of 4.1p/kWh.