|The International Quarter, Stratford City, once completed, will be connected to the Olympic Park’s low-carbon district energy scheme Credit: TIQ|
Thanks to its ambition of being the ‘greenest Games ever’, the London 2012 Games has left a legacy including an extensive district energy network serving the former Olympic Park and its surroundings, explains Kevin McDonald of Cofely.
There can be no doubt that the London 2012 Games have delivered a sporting legacy that will influence the UK’s athletes for many years to come. Less well known is the environmental legacy of the Games, in the form of a low-carbon district energy network that will also have a profound impact over future decades.
One of the main ambitions for the London Games was that it should have a low impact on the environment and contribute to the Olympic Development Authority’s commitment to reducing carbon dioxide (CO2) emissions. This was a key driver for the creation of a low-carbon district energy scheme which served the Olympic and Paralympic venues and other facilities during the Games, and continues to serve built assets in the area once the games were complete.
The Olympic Park District Energy Scheme (OPDES) has been designed, financed, constructed and operated by Cofely and its parent company GDF Suez. This represented an investment of more than £100 million ($160 million) by Cofely, which will be recouped through the sale of heating, cooling and electricity under a 40-year concession agreement between Cofely East London Energy Ltd – Cofely’s subsidiary company which owns the OPDES. In legacy, it is projected that 11,000 tonnes of CO2 emissions will be saved each year by 2015, compared with using traditional heating and cooling plant in each building.
The OPDES provides low-carbon combined cooling, heating and power (CCHP) from two energy centres – one at Kings Yard in the Queen Elizabeth Olympic Park, the other in nearby Stratford. King’s Yard served the Olympic venues during the Games and will serve the former Olympic Park as it is redeveloped.
The Stratford energy centre started providing heating and cooling to the Westfield Stratford shopping centre before the Games and will serve additional residential and commercial buildings in the Stratford area as the scheme develops. The International Quarter (TIQ), Stratford City – planned by developer LendLease – will add 11,219,200 m2 of workspace, an 83,820 m2 hotel and 15,849 m2 of retail, in addition to an estimated 537,843 m2 of total housing for the surrounding areas – all of which will be connected to the OPDES. Both energy centres will also generate electrical power for local use and export to the national grid.
While the energy centres can be operated independently for resilience, they are inter-linked by two large heating mains to make it easier to accommodate rising demand in the future and to ensure the heating plant can be operated efficiently at low load conditions. Each energy centre incorporates a control centre with the capability to operate both energy centres from either site.
Some redundancy has also been built in to enable systems to run without interruption if items of plant are taken off line for maintenance. These arrangements also provide greater resilience to the OPDES network.
The system operates with constant temperature, variable volume water circuits, using speed controlled circulating pumps to alter the volume, while ensuring a sufficient pressure difference between flow and return circuits to pass the water through heat exchangers in the substations. A total of 48 heating and 23 cooling substations are distributed around the network to supply the buildings. These comprise either one or two heat exchangers depending on whether the building is taking heating and/or cooling. A secondary circuit then transfers the heat or cooling to the building.
In the summer, when heating loads are low, CCHP run-time will be optimized by using the heat to drive absorption chillers, which are supplemented by 7 MW ammonia chillers when required. Heat is rejected from the chillers through roof-mounted cooling towers.
The hot water circuit includes a 27.5 MWh capacity buffer vessel that will enable uninterrupted operation of the CCHP engine and the boilers to maximize efficiency.
A similar principle has also been applied to the chilled water circuit with inclusion of a 750 m3 chilled water buffer vessel that increases the capacity of the chilled water system by 4.7 MWh. This will enable the absorption or ammonia chillers to continue running to charge the vessel, even when cooling loads are low.
A third tank is used to store treated make-up water for the hot and chilled water systems.
Hot and chilled water are generated from a number of sources, including gas-fired CCHP, biomass and biofuel boilers, absorption and ammonia chillers and traditional heating plant (see Table 1). The OPDES has 100 MW of heating and cooling capacity, and has the potential to expand to 200 MW.
Crucially, the energy centres have been designed to be both fuel and technology agnostic. The ability to switch between gas and biomass for heat generation enables Cofely to select the most economic option in line with fuel tariffs.
As the system is technology agnostic, additional renewable technologies can easily be introduced and integrated with existing systems to maintain minimum environmental impact and comply with future energy legislation. For example, residential developers in the former Olympic Park will be required to comply with CO2 reduction targets laid out in Policy 5.2 of the London Plan, which are more demanding than current building regulations and the proposals for Part L 2013. Local authorities are expected to impose the same or similar targets on developments outside the legacy area.
Post-Games, the Olympic Park legacy area is being redeveloped, with only a few of the Olympic venues being retained. The Greater London Authority anticipates nearly 3.7 million m2 of new development, with over 29,000 housing units (a mix of private and social housing) and 1.36 million m2 of commercial space on the park.
The former Olympic Park will be divided into five new ‘neighbourhoods’, each with a distinct character and centred around parks and squares. The development will also provide play areas, schools, community spaces, health centres, shops and a wide range of leisure facilities. The first neighbourhood to be developed is Chobham Manor, over about 93,000 km2 between the former athletes’ village and the VeloPark. Taylor Wimpey and L&Q have been appointed to build the neighbourhood, which will address the local need for larger homes with 75% of the 870 dwellings having three or more bedrooms.
|The Kings Yards energy centre’s plant room Credit: Cofely|
The legacy area has been designated as an ‘area of exclusivity’, so that Cofely is the sole provider of heating and cooling to the site. Prices are determined via a concession agreement that includes a price control formula to ensure energy costs are comparable to or below market rates.
The concession agreement also requires that Cofely undertakes all aspects of service provision for the energy network, including design, financing, construction, connections, operation and maintenance of the energy centres and networks.
While the heating and cooling loads could be accurately predicted for the period of the Games, future loads were less certain when the scheme was being designed. As the design needed to be highly flexible, Cofely therefore adopted a modular approach in designing the energy centres so that additional plant can be added in the future. Bays have been allocated in the energy centres for the additional plant, with pipework and flues already in place. Both energy centres have been designed so that sections of cladding can be easily removed for the new plant items to be installed.
This modular arrangement will also enable Cofely to ensure that as heat loads increase the proportion of energy generated from renewable sources remains constant. For example, there is currently a 3.5 MW biomass boiler at the King’s Yard site, with provision for another biomass boiler of the same capacity to be installed in the future. It is anticipated that further renewable technologies, and potentially new thermal conversion technologies, will also be introduced to the scheme as it evolves.
Several technologies could be incorporated into the scheme. The key impacts and constraints are likely to be the space required, the reliability of the technology and the economic impact on the operation of the district energy system. Using renewable gaseous fuel (syngas) from waste gasification would be seen as a carbon-neutral option, as would biogas from an anaerobic digestion plant. Both these fuels could be used with the existing CCHP plant, but each technology or fuel will have a different impact and would need to be assessed on a case by case basis.
Another challenge was the installation of 18 km of pre-insulated heating and cooling pipework, much of which had to be installed before the venues were constructed. Extensive 3D modelling enabled the mains pipes to be installed in sections and gradually joined as each area of the site became available.
The pre-insulated carbon steel pipes are buried so that the top of the pipe is at least 1 metre below the surface, and the high level of insulation ensures that network losses are low, with a temperature change of around 1°C/km. In some instances these were installed before the landscaping had been completed, so that the ground was not always at the finished level. These pipe sections were installed above ground on temporary supports and then subsequently covered as the groundworks were finished.
To allow for future expansion, the pipe network includes points for running extensions to new buildings. Bridges across railways and waterway have also been fitted with sleeves for running pipework through at a later date, which should minimize the use of expensive bespoke pipe gantries and tunnels for crossings.
The OPDES team is also working closely with building operators and developers in the legacy area to ensure that it understands their future heating and cooling requirements. For instance, iCITY is currently developing the former International Broadcast Centre to create a centre for innovation and enterprise and BT has recently announced it will use the north end of the centre as the home of its new sport channels. As well as TV and editing suites, a control centre and an audience area, the facility will incorporate a 23,225 m2 data centre. Peak cooling loads are projected to reach about 40 MW.
Other buildings being retained include the former athletes’ village, which is being converted to 3000 apartments (again mixed private and social housing), the stadium, the aquatic centre, the VeloPark, Eton Manor and the handball court, which will be made into a multi-use sports venue.
While most district energy schemes are developed in conjunction with a local authority, the OPDES is unique in being procured by the Olympic Delivery Authority and Stratford City Developments Ltd for the entire Olympic Park.
However, there are major plans to expand the heating network outside of the park, and at times there is also a need to liaise with other authorities such as the Canal and Rivers Trust. For example, a bridge to Hackney Wick Fish Island, which is due to be completed in 2019, will have provision for district heating pipes. But development work on the island has already begun, so it will be necessary to construct a temporary bridge for the pipework to ensure these new developments benefit from connecting to OPDES.
Four ‘break out’ points from the Olympic Park have been identified to enable the OPDES to be extended to properties in the neighbouring London Boroughs of Hackney, Tower Hamlets, Waltham Forest and Newham. The first of these to be connected will be the Stratford Halo, a 700-unit residential tower with attached sheltered accommodation, the first of five blocks being developed by Genesis Housing Association.
It is anticipated that most of the new development over the next 20 years will be close to the Olympic Park and Stratford City, with little change anticipated for the relatively low-density housing in the more peripheral areas. There is also a large hospital at Homerton and some industrial activity along the River Lea and its waterways that could connect to the scheme in the future.
Connecting existing heating and cooling systems to the network is very straightforward as the hot and chilled water temperatures are comparable to those generated by separate boilers and chillers.
Linking to the network could also enable building operators to free up plant room space and could remove the need to maintain existing central plant items. The inherent efficiency of district energy schemes means that most consumers can expect to save 5–10% on their overall energy bills, compared with traditional methods.
When the OPDES was first conceived, there were plans to make it part of a wider-ranging London Heating Plan that would connect several district energy schemes.
To that end, planning support will be vital in maximizing the opportunities that the district energy scheme offers and the new Planning Policy and Decisions Team will be using the London Plan and the Olympic Legacy Supplementary Planning Guidance as the basis for future developments. High density developments will therefore be encouraged to take advantage of the carbon savings that can be achieved through using centralized energy generation, rather than discrete solutions on individual sites. As further encouragement, energy supplied to developments outside of the legacy area will continue to be competitively priced.
As a result, the OPDES is expected to expand substantially over the coming years, supported by the existing and emerging planning policies of the ‘host’ boroughs and the Mayor of London. It is also seen as a key contributor to achieving the Mayor of London’s target to supply a quarter of London’s energy from decentralized sources by 2025.
Legacy beyond London
Developing the largest district energy scheme to be built in one go in the UK presented the Cofely team with several challenges along the way. Apart from the sheer scale of the scheme, there were some unique features to this project that do not apply when a district energy scheme is developed within an existing urban environment.
The procurement process, the number of stakeholders involved both pre- and post-Games, and the extensive modelling required to plan the network infrastructure in parallel with the construction of new buildings on the site have all contributed to a steep but very satisfying learning curve. Furthermore, the lessons learned in the development of the OPDES are now to be applied to other new urban district energy schemes being developed by Cofely in mainland Europe and in the Far East. This export of expertise is yet another legacy of the London 2012 Games.
Kevin McDonald is Business Development Manager – London with Cofely District Energy; www.cofely-gdfsuez.co.uk
Key facts and figures
18 km of supply and return pre-insulated pipework
Pipework diameters range from 50 mm to 700 mm
Hot water flow/return temperatures 95°C/55°C
Water flow rates up to 400 litres per second
Integral leak detection
First phase capacity
- 93 MW total heating
- 3 MW biomass heating
- 57 MW cooling
- 10 MW low-carbon electricity
Legacy potential capacity
In legacy, the combined district energy network has potential for total capacities up to:
- 200 MW heating
- 64 MW cooling
- 30 MW low-carbon electricity
Energy centre focus
There are two interconnected energy centres, one at Kings Yard on the Olympic Park and the other at Stratford.
Kings Yard Energy Centre
The Kings Yard Energy Centre is on the western perimeter of the Olympic Park, serving the Olympic venues and the developments that will be constructed after the Games.
The building features innovative construction methodology, using over 500 tonnes of steel and 3500 m2 of concrete planks to form the floors and roof.
Adjacent to the energy centre building are two 750 m3 thermal storage tanks, and a 750 m3 treated water store. The thermal storage tanks allow water to be heated in the most efficient manner and stored ready for use. The retained building has a further two storage tanks.
The system design is modular, with space allowed for future increases in capacity.
Stratford City Energy Centre
The Stratford City Energy Centre is at the east of the Olympic Park and adjacent to the new Stratford City retail and commercial development. Like the Kings Yard centre, this energy centre uses a gas-fired CCHP system, along with biomass boilers.
The Stratford Energy Centre provides heating and cooling to the new Westfield Stratford City shopping centre and is being extended to Stratford High Street and beyond.
Both energy centres incorporate demountable pre-weathered steel panels over a timber frame, structural insulating panels and a re-sealable membrane. This will allow additional plant capacity and future low-carbon technologies to be implemented in a cost-effective manner.