Kier is creating a striking London landmark that can also heat thousands of homes on Knight Dragon’s huge Greenwich Peninsula development.
Project: Greenwich Peninsula Energy Centre
Client: Knight Dragon
Contract value: £16.8m
Contract type: Design and build
Main contractor: Kier
Start date: May 2015
Completion date: December 2016
How do you solve a problem like heating 15,000 homes in east London?
That was the challenge facing developer Knight Dragon when it was tasked with heating Greenwich Peninsula, one of London’s largest housing developments.
Following in the footsteps of other major London schemes, the Greenwich Peninsula Energy Centre will be the heart of the new development, pumping hot water to the thousands of homes and businesses across the site.
But supplying energy is not the only part of main contractor Kier’s brief: client Knight Dragon also wants its new facility to become a visual landmark for London’s newest neighbourhood.
The need to balance artistic considerations with technical challenges has posed some unusual challenges for the construction team.
Energy of the future
The majority of new major new residential developments now incorporate an energy centre as the means of heating their homes and businesses.
The Queen Elizabeth Olympic Park and King’s Cross Central Development are among the high-profile schemes on which energy centres have been identified as the best solution for producing vast amounts of heat efficiently.
“Energy centres are the future,” says Knight Dragon construction director Paul Symons. “If you are really serious about reducing your carbon footprint, I think providing all of your hot water through an energy centre is the best way to do that.”
Greenwich Peninsula Energy Centre Kier Knight Dragon 5
With work overseen by specialist Pinnacle Power, by 2030 the Greenwich Peninsula Energy Centre will provide heat to 15,000 homes with an efficiency of 97 per cent.
“In essence the energy centre is very much like your hot water system at home: there are boilers, pumps and hot water storage vessels,” says Kier construction project manager Ben Fleming.
At the heart of this will be a Bosch combined heat and power plant. The CHP will heat water via its combustion chamber, producing steam that not only heats the development’s water but also drives a turbine to provide electricity back to the national grid.
“The client wanted to go down the route of site welded, but we said you have more control doing it at a fabrication yard to remove risk.”
Ben Fleming, Kier
Hot water will then fill the energy centre’s boilers – 333 times the size of a household boiler – as well as its massive 65,000-litre thermal energy stores – more than 2,000 times the size of a domestic hot water storage tank.
But while the CHP and boilers were relatively easy to install, the thermal tanks caused difficulties. Imported from Belfast, the tanks were all set to be lifted by a 350-tonne crane on a Thursday, but strong winds put paid to that.
“We had the tanks sitting around with five irate lorry drivers who wanted to get back to Belfast, so we had to soothe them and eventually did the lift over the Friday and Saturday.”
Greenwich Peninsula Energy Centre Kier Knight Dragon 8
From these tanks the hot water will be pushed out through a district heating network of pipes across the 60,000 sq m development. All of this has been designed through a fully integrated M&E BIM model that flagged clashes and enabled decision-making over piping connections and the locations of valves.
“The decision was made at an early stage to use flange connections,” Mr Fleming says. “The client wanted to go down the route of site-welded, but we said you have more control doing it at a fabrication yard to remove risk.”
New London landmark
The main purpose of the energy centre is to ensure the showers and radiators of Peninsula residents are supplied with hot water, but Knight Dragon also has another aim for the building. “What we want to create is a geographical and symbolic landmark that will give the Greenwich Peninsula an identity,” Mr Symons says.
Standing 48 m high, the centre’s 10 flue towers are wrapped in what its creator and Royal Academy artist Conrad Shawcross calls the “optic cloak”.
“There were a lot of people involved: the artists, the structural engineer Billingtons, the structural steel designers, the cladding designers Lakesmere and Aone Flues who put the flues in. This gave us some headaches”
Ben Fleming, Kier
“Our view was: rather than avoid the issue and try to hide it like you usually would with an energy centre, we wanted to embrace the chimneys and build something that would create a visual landmark for residents.”
Linking up with place-making consultancy Future City, a design competition was run with three established artists approached to come up with concept designs for the flue tower. The winner of this competition was Mr Shawcross, globally renowned sculpture and youngest living member of the Royal Academy of Arts.
The design he came up with was a tower covered with aluminium triangular panels, perforated to give a moiré pattern – an effect that is created when two semi-transparent identical patterns are overlaid at odd angles.
While the design looks like it will achieve its goal, with the tower already providing a striking centrepoint for the Peninsula, getting to that end point did come with its challenges. “There were a lot of people involved: the artists, the structural engineer Billingtons, the structural steel designers, the cladding designers Lakesmere and A1 Flues who put the flues in. This gave us some headaches,” Mr Fleming admits.
“Conrad understandably cared about the aesthetics, but didn’t worry too much about how it worked structurally, we had to change things to get that balance”
Ben Fleming, Kier
The arts and engineering worlds are not ones that often collide, and getting the right balance between the aesthetics and structural design of the tower needed careful appraisement. “Conrad understandably cared about the aesthetics, but didn’t worry too much about how it worked structurally; we had to change things to get that balance,” Mr Fleming says.
One of the biggest changes was the height of splice plates that were required. “They were initially designed to come up with the best engineering solution, but Conrad decided that didn’t look very good,” Mr Fleming says. “[He] wanted these plates to be in a certain way to show a flow, rather than just haphazardly positioned.”
This would result in more plates than initially planned being placed on the flue tower. After long discussion the team agreed on 137 panels. There was also a compromise with cladding brackets too.
Greenwich Peninsula Energy Centre Kier Knight Dragon 3
“The cladding involves each individual piece clipping onto the primary steelwork through brackets,” Mr Symons explains. “Lakesmere came up with an initial solution that had those brackets in the best locations to suit the structural integrity of the tower, picking up wind-loadings, etc.”
“But what Conrad wanted was something where brackets were in position that fitted with his initial design so there was an element of symmetry to where the brackets were. There was a lot of toing and froing about how to find the right symmetry, yet still ensure the thing would stay fully supported, which did take some time.”
Mr Fleming adds: “There had to be a lot of conversations before we came up with something everyone was happy with. It did slightly eat into our schedule, but we got there in the end and that is the main thing. I think all parties are pleased with the final outcome.”
One challenge after another
While the energy centre remains on time and on budget, its construction and design posed not only aesthetic difficulties. “There were definitely challenges we had to overcome at both design and construction stage,” Mr Symons says.
The first was in the flue tower’s design. With such a complex structure and building envelope and with many stakeholders to appease, there were worries that an elongated design period would see the project miss its 15-month completion deadline.
“Getting the design right for the optic cloak took us longer than expected and started to eat into our build time,” Mr Symons says.
With construction starting before the design was completely finished, the project hit a potential stumbling block when Billington Structures began the steelwork.
“If we went ahead with Billington installing the building’s full steel structure straight away, we would have locked off the area where we needed to put in the steel frames for the flue tower,” Mr Symons explains. “If we weren’t careful, the project would grind to a halt.”
Greenwich Peninsula Energy Centre Kier Knight Dragon 7
The energy centre building was effectively built in two sections to combat this, leaving a space in the middle so the flue tower could be accessed. “We realised this worked really well, and what could have been a big problem was eventually mitigated to have almost no impact on delivery times.”
Then there was the issue of access to the flue tower so that the optic cloak could be installed. Built on a slope just metres away from the A102, the construction teams soon realised they could not secure a crane long enough to allow the cladders to place the steel plates on the flue tower.
Kier came up with the idea of using a spider crane at the top of the tower to ensure cladding could be installed with minimum fuss.
“Using the crane on top of the flue tower is pretty unusual,” Mr Fleming points out. “It is self-supporting and allows other things to go on around it. It is self-supporting – all you need is a crane on top of the tower so it takes that off the site logistics.”
“This real forward thinking allowed us to get over what could have been a major problem,” Mr Symons adds.
Despite the various challenges already faced, the team remains confident that energy will be being generated for homes at Greenwich Peninsula by Christmas.
Adaptable to the Peninsula’s needs
While the completion date for Kier’s initial contract will finish in December, work will continue on the energy centre for years to come.
Unlike most projects, it will not be a case of building it and leaving it to run. When the energy centre first comes online in December, only three boilers will have been installed, producing just 25 MW of heat output. The finished project will eventually see six boilers installed producing 85 MW.
The extra boilers and CHPs will be installed as the site around it expands. “The energy centre grows as the development grows – there is little point putting in all the equipment on day one and then not using it,” Mr Symons explains.
Panels on the side of the main will be removed in due course, allowing more boilers and CHPs to be installed over the coming years. This, according to Mr Symons, gives the developer more flexibility and can allow for changes in the building schedule.
“We have a plan and we think we know when extra load will be required, but it is dependent on whether the building sequence slows down or speeds up. If either happens, we can adapt appropriately.”
It could also allow for the energy centre being scaled down, depending on the energy usage of the first tranche of housing developments that come online.
“We will reform our final build plan on what the real numbers are in terms of energy usage instead of predicted numbers,” Mr Symons says. “This means the model stays flexible to match what the final need will be.”