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Delivering a Hybrid Renewable Energy Solution for the Elizabeth line Depot at Old Oak Common

Old Oak Common in west London for many decades has been 100 acres of railway lines, sidings and depots south of the Grand Union Canal as well as down-at-heel industrial estates. The area is currently undergoing regeneration and 25,000 homes and 55,000 jobs are due to be created there over the next 15 years, that will be supported by 250,000 passengers a year using a transport super-hub with proposals for Elizabeth line, HS2, Tube and Overground stations all close to each other.

The Old Oak Common Elizabeth line depot consists of the redevelopment of railway land to construct a new rail maintenance facility including an Operations, Maintenance and Control (OMC) building containing nine maintenance roads, which includes a jacking road and an accommodation block for both the train maintainer Bombardier and the operator of Elizabeth line services (MTR) and 33 stabling sidings accommodating the Elizabeth line fleet.

The project has demonstrated the importance and benefits of early contractor involvement and collaboration from bid stage through to construction. The Bombardier, Taylor Woodrow team with GI Energy and NG Bailey have worked closely together for the past 3 years, initially on the bid proposal, then more recently on detailed engineering and now currently on the construction of the new Depot building at Old Oak Common, that will enable Bombardier to operate and maintain the new trains for 32 years once the railway opens from 2018.

The initial project concept design did not meet the required planning consents thresholds for CO2 savings and the use of renewable energy. Taylor Woodrow, GI Energy and NG Bailey worked together to create a solution that exceeded the 20% reduction in C02 planning requirements for the project. The workshops that took place for the development of the M&E design followed the London Plans recommended Be Lean> Be Clean> Be Green process

Be Lean

  • Insulation levels were increased to the OMC building
  • Thermal mass of building utilised - floor slab
  • On site plant use was reviewed with the end user and energy efficient options selected
  • Boilers downsized to single system standby

Be Clean

  • LED lighting is being installed throughout the site
  • Use Low to Zero Carbon Technologies (LZCT) where possible, supplement or replace energy hungry systems
  • Combined Heat and Power (CHP) units to be installed to provide high temperature heating and electrical demand

Be Green

Use a range of renewable energies;

  • Ground sourced heat pump (GSHP)
  • Solar Photo Voltaic and
  • Solar thermal

Supplement and widen low energy solutions (provide underfloor heating and cooling)
Integrate systems and appoint lead energy controller – capture waste heat from CHP and transfer into geothermal ground loop

What resulted from the early workshops was a system that would deliver over 30% renewable energy solution by clever integration of CHP, solar PV and thermal with GSHP that enables any surplus heat to be stored within the ground loop, thereby reducing the client’s operational costs and increasing CO2 savings significantly. This integrated design development enabled the team to exceed the original brief whilst maintaining our objectives. We developed a scheme that provided for all energy production to be developed as a single solution to meet the energy demands of the project.

Our enhanced design initially used 466 foundation piles as geothermal piles supplementing 25 closed loop deep bores. This was amended during refinement of the structural design to 366 geothermal piles and 52 150m deep bores twinned with GSHP to provide 900kW of heating and 780kW of cooling; these are supported with two Combined Heating and Power (CHP) systems delivering 420kWth heating and 290kWe of electrical load along with 1500m2 of PV cells providing 220kWe on the roof of the OMC and 170kW of solar thermal panels. 54% of the new railway depot’s heating and cooling will be provided from renewable technologies and 20% of electrical load will be generated on site from CHP / Solar PV, providing the rail depot with an overall 33% renewable energy solution.

Energy Pile construction sequence -

Our design divides the building into two service zones, providing flexibility for moving energy throughout the main building. In addition, our recharge cycle introduced a cooling opportunity into the underfloor heating system, making Old Oak Common (we believe) the first UK Railway depot with underfloor cooling throughout the workshop. The energy piles sit in London Clay which will be used as an energy store, retaining thermal energy from both production and regeneration for use when building demand requires it, rather than losing this to atmosphere. This supports the incorporation of CHP plant into the design, which provides a constant thermal output for hot water, with any over-production stored in the ground and also provides a parallel electrical generation for non-essential electrical services.

Our design has expanded the innovative underfloor heating and cooling system to cover the majority of the building which includes both workshop and accommodation areas and is all fed primarily from the GSHP system. We have added low temperature radiators in areas where raised access floors make the use of underfloor heating circuits difficult; these are also fed from the GSHP system, thereby reducing the demand for gas-fired boilers to serve conventional radiators. This has resulted in almost entirely removing conventional space and water heating from the design.

The use of multiple energy sources along with connecting the north and south low temperature thermal circuits, enhances the system resilience, as we are able to transfer thermal energy between the north and south mechanical systems.

The technical team has developed the solution in collaboration across both distribution and controls disciplines, enabling the development of a single integrated design that together optimises the generation, storage and use of energy. By making use of the seasonal cycle of heating and cooling along with regeneration of the geothermal mass we are able to introduce green cooling into the majority of the building. The system provides underfloor and low temperature radiator heating and cooling throughout the building (with the exception of a few temperature controlled areas using conventional air conditioning).

Whilst the use of renewable technologies is now widely employed, the scheme for Old Oak Common Depot is unique in; the extent and integration of system technologies, the use of a thermal store, and provision of heating and cooling through low temperature distribution to both the accommodation and maintenance areas. The individual systems are tried and tested, our innovation is in developing a renewable systems design which fully integrates separate systems to provide a holistic energy solution, switching between energy sources as demand and availability dictate.

The system development provides the following direct benefits:

  • 50% renewable energy provision exceeded requirements for 20% provision
  • 65% reduction in CO2 production exceeded planning requirements for 20% reduction
  • A net increase in the CAPEX for building services of approximately 5% which yielded a net reduction in the OPEX costs of approximately 33% of the building services CAPEX (and providing a projected 1500% Return on Investment)
  • It is anticipated Bombardier will save some 17,000tonnes of CO2 over the 32-year life of the building.

Of significant importance to this system will be the sophisticated control system that GI Energy has developed and designed to optimise the integration of the renewable technologies installed, that will actively maximise both annual run cost savings and CO2 savings, and at the same time enable remote monitoring. We believe that the through the long term management of the system, and optimisation, performance can be significantly enhanced, improving savings by up to 10% from that currently stated.

As the market leader in the UK, GI Energy has considerable experience designing and installing renewable energy solutions, having installed more than 250MW of renewable energy solutions in schools, hospitals, universities, supermarkets, commercial developments, housing associations and Railway infrastructure since its inception in 2000.  GI Energy recognise the need to offer turnkey solutions to clients utilising the most appropriate renewable solutions to best deliver their objectives for each project, our role acting as an ‘Energy Partner’ is key to ensuring we offer the best possible solution for every scheme. GI Energy was recently voted Heating and Renewables Installer of the year and more recently the Old Oak Common project was voted Renewable Energy project of the Year by H&V News.

The design concept has been embraced by TfLand assists them in meeting their aspirations for a Green Railway. Our collaborative approach has delivered a truly innovative sustainable hybrid renewable energy system, breaking the boundaries and setting a new benchmark in delivering renewable energy projects. The system has exceeded client and Planning requirements and delivered significant monetary and environmental savings, which will be used as best practice to deliver the same benefits to future projects.

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