For many decades, the area south of the Grand Union Canal at Old Oak Common in West London has included 100 acres of railway lines, sidings and depots as well as down-at-heel industrial estates. However, it is currently undergoing regeneration and 25,000 homes and 55,000 jobs are due to be created there over the next 15 years.
This development will result in 250,000 passengers a year using a transport super-hub with proposals for Elizabeth line (née Crossrail), HS2, Tube and Overground stations all close to each other.
There will also be an Old Oak Common depot for the Elizabeth line. Existing railway land will be redeveloped to construct a new rail maintenance facility including a nine-road operations, maintenance and control (OMC) building. One of the roads will be fitted with jacks which will be able to lift an entire train.
The new depot will also include offices for both Bombardier, the train maintainer, and MTR, the operator of Elizabeth line services, as well as providing 33 stabling sidings.
The London Plan challenge
The project has demonstrated the importance and benefits of early contractor involvement and collaboration from bid stage through to construction. A team of engineers from Bombardier, main contractor Taylor Woodrow, GI Energy and NG Bailey has worked closely together on the project for the past three years.
From the original bid proposal, the integrated team has since developed the detailed engineering design and is now overseeing 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 consent’s 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 per cent target reduction in CO2. The workshops that took place for the development of the M&E design followed the London Plan’s policy of Be Lean> Be Clean> Be Green.
Defined in the current London Plan of March 2016, the project team took the following steps to comply:
Be lean: use less energy
» Insulation levels were increased in the OMC building;
» Thermal mass of building utilised – floor slab; » On-site plant use was reviewed and energy efficient options selected;
» Boilers downsized to single system standby.
Be clean: supply energy efficiently
» 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 renewable energy
» Use a range of renewable energies; » Ground-sourced heat pump (GSHP);
» Include solar photovoltaic and solar thermal solutions;
» Supplement and widen low energy solutions (provide under-floor heating and cooling);
» Integrate systems and appoint lead energy controller – capture waste heat from CHP and transfer into geothermal ground loop.
A series of workshops resulted in a solution that would deliver over 30 per cent renewable energy using a clever integration of CHP, solar photovoltaic 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 its objectives. A scheme was developed that provided for all energy production to be integrated into a single solution to meet the energy demands of the project.
The 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 52 150-metre-deep bores twinned with GSHP to provide 900kW of heating and 780kW of cooling. These are supported by two CHP systems delivering 420kWth heating and 290kWe of electrical load along with 1500 square metres of PV cells providing 220kW on the roof of the OMC and 170kW of solar thermal panels.
In total, 54 per cent of the new depot’s heating and cooling will be provided from renewable technologies and 20 per cent of electrical load will be generated on site from CHP/solar PV, providing the depot with an overall 33 per cent renewable energy solution.
The depot’s design divides the building into two service zones, providing flexibility for moving energy throughout the main building. In addition, the recharge cycle introduced a cooling opportunity into the underfloor heating system, making Old Oak Common probably 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 the 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.
The innovative underfloor heating and cooling system has been expanded to cover the majority of the building, including both workshop and accommodation areas, and is all fed primarily from the GSHP system. Low-temperature radiators have been added 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 thermal energy can be transferred 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 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, green cooling has been introduced into the majority of the building and the system provides underfloor and low temperature radiator heating and cooling throughout (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 the provision of heating and cooling through low-temperature distribution to both the accommodation and maintenance areas. The individual systems are tried and tested, the innovation is in developing a renewable-systems design which fully integrates separate systems to provide an holistic energy solution, switching between energy sources as demand and availability dictates.
The system development provides the following direct benefits:
» 50 per cent renewable energy provision exceeded requirements for 20 per cent provision;
» 65 per cent reduction in CO2 production exceeded planning requirements for 20 per cent reduction;
» A net increase in the CAPEX for building services of approximately five per cent which yielded a net reduction in the OPEX costs
of approximately 33 per cent of the building services CAPEX (and providing a projected 1500 per cent return on investment) ;
» It is anticipated that Bombardier will save some 17,000 tonnes of CO2 over the 32-year life of the building.
Of significant importance will be the sophisticated control system that GI Energy has developed and designed to optimise the integration of the renewable technologies installed. This will actively maximise both annual run-cost savings and CO2 savings and, at the same time, enable remote monitoring.
It is believed that, through the long-term management and optimisation of the system, performance can be significantly enhanced, improving savings by up to 10 per cent 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 recognises the need to offer turnkey solutions to clients utilising the most appropriate renewable solutions to best deliver their objectives for each project. The company’s role, acting as an ‘Energy Partner’, is to ensure it offers 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 TfL as part of its aspirations for a Green Railway. The 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.
Written by Tony Amis, business development director at GI Energy, and Mike Beagle, senior M&E manager at Taylor Woodrow.