A pioneering development being delivered by United House in Kingston-upon-Thames is using the river’s water to heat residents’ homes.
Project: Kingston Heights mixed-use development, Kingston-upon-Thames
Client: NHP Leisure Developments
Contract value: £34m
Main contractor: United House
For flood-hit residents across the country, the attraction of living near water must be wearing pretty thin.
Householders in Scotland, the North-east, East Anglia, Wales, the South-west and the Thames Valley have been hit by the record-breaking wind and rainfall that winter has delivered.
The rising waters of the River Thames put 3,000 homes in Kingston-upon-Thames alone at serious risk of flood, but for one of the town’s latest developments the river is crucial to delivering sustainable energy attributes.
Cutting-edge heat pump
Kingston Heights is a £70m mixed-use development that will offer 81 privately owned and 56 affordable residential apartments alongside a 142-bedroom hotel and conference centre.
It will use the latest in green power – a water-source heat pump – to deliver all its hot water, heating and cooling requirements.
“UKPN was a little concerned about using CFA rigs because of the fear they might collapse onto the substation, putting it out of action”
Patrick Egan, United House
Contractor United House is developing the site for client NHP Leisure Developments.
The 81 privately owned apartments in the development have already been pre-sold to housebuilder Redrow, which is completing the fit-out for the block.
United House construction manager Patrick Egan is overseeing the rest of the scheme.
It is a tricky site – historically a hotch-potch of industrial land sitting alongside a railway, part of which was originally Kingston Power Station.
Since it ceased production in the 1980s, the station has been demolished and part of the site left as a huge, fully operating substation owned by electricity network provider UK Power Networks.
And as leaseholder of the site, UKPN needed to keep the vital substation operating. This is the main reason the site had remained undeveloped over the years, but the project team had a plan.
Its proposals encapsulated the existing substation, incorporating it into the design of the final scheme while isolating the noise and vibration from residents in the hotel, apartments and surrounding area.
The team has installed a steel-lined concrete box over the top of the substation in what is believed to a first for encapsulating an operating substation like this.
It has been anything but a simple challenge.
“We used plastic shovels to hand-dig the trial holes. It meant that much of the pile layout had to be redesigned ad-hoc”
Patrick Egan, United House
The box itself is a 200 m-long, 38 m-wide and four storeys-high precast concrete structure supported on some of the 600 CFA piles spanning 600 mm in diameter that have been installed across the site at depths of up to 27 m.
“UKPN was a little concerned about using CFA rigs because of the fear they might collapse onto the substation, putting it out of action,” Mr Egan explains.
“But we managed to persuade UKPN that by installing the correct, robust piling mat, CFA rigs could operate safely without fear of toppling.”
Piling on the fly
But with high-voltage electricity and cables running around the site, the siting of the piles themselves was critical, with hundreds of hand-dug trial holes being excavated to provide the location of services.
“When you get so close to such huge voltages of electricity then the safety implications are very serious,” Mr Egan says.
“We used plastic shovels to hand-dig the trial holes. It meant that much of the pile layout had to be redesigned ad-hoc.”
“We had to work out maximum bridge loading weights and work with the police to agree the route”
Patrick Egan, United House
These redesigns affected the initial pile layout and pilecap design. Some of the piles were boosted to 750 mm diameter to account for the extra loading on them.
The encapsulation box itself is formed using precast concrete columns, with precast bridge beams and infill panels stretching between the columns.
Fifty u-shaped precast beams form the deck of the box, spanning up to 38 m and weighing more than 70 tonnes.
These 1,500 mm-deep precast, pre-stressed beams were brought in during overnight deliveries to site on the back of telescopic trailers with rear-steering axles.
“Planning the delivery route in took time,” Mr Egan recalls. “We had to work out maximum bridge loading weights and work with the police to agree the route.”
Delivery was limited to between 8pm and 5am, with three of the beams being brought onto site each evening. A 1,000-tonne Superlift crane provided by Sarens was used to lift the beams into position at 1 m centres.
Concrete over steel
Initially the design had been a steel structure, but the heavyweight nature of the blast resistance, fire, vibration and noise insulation requirements pushed the team toward a concrete-frame solution for the encapsulation.
Steel has, however, played a major part in the structure, with the whole concrete enclosure encased in a 10 mm-thick steel sheet outer box, which acts similarly to a Faraday Cage.
This protects the equipment from external electrical fields such as lightning strikes, while also isolating that of the substation.
One section of the residential development launches directly from the concrete enclosure and is steel-framed from the fifth floor and above, but the hotel features a cast in-situ concrete frame.
Serious climate control
Thanks to the four transformers within the substation box, there are tight climate control measures in place that keep temperatures below 70 deg C.
“We have very tight acoustic standards for the development. Stopping noise and vibration have been a real focus throughout the development”
Patrick Egan, United House
This does however mean that 1.2 m-diameter fans have been installed to provide airflow through the building.
These huge fans can create challenges managing the acoustic requirements of the building, but the team has put in attenuation systems including louvres at the base of the outer walls, which baffle any noise.
“We have very tight acoustic standards for the development,” Mr Egan says. “The specification is very heavy on that. Stopping noise and vibration have been a real focus throughout the development.”
With its one-off substation encapsulation and innovative use of the Thames to deliver its renewable energy strategy, residents of the Kingston Heights development are set to benefit from a proximity to the river.
UK ‘first’ in green power
Mike Spenser-Morris is a force of nature. The director of NHP Leisure Developments oozes enthusiasm and is glowing in his belief in the water-source heat pump that will provide heating and cooling to the scheme.
And well he might be. Without his drive it is unlikely that the system, which he says is the first of its type in the UK, would even have been contemplated.
“I had looked at the feasibility of using ground-source heat pumps here but they were impractical. It occurred to me that we should be making use of the river,” he says.
At 2 m below the surface, the water temperature averages around 8 to 10 deg C and never falls below 7 deg C, making it a constant source of renewable energy all year.
But after months of research, Mr Spenser-Morris had still not been able to find anyone who had carried out this sort of installation.
“We kept being told that there didn’t seem to be any reason why it would not work in principle – but the next minute people would say, ‘If it’s such a good idea why hasn’t it been done before?’” he says.
Eventually he tracked down a local authority in Japan which had commissioned a similar scheme.
Engineering giant Mitsubishi had worked on that project and Mr Spenser-Morris had been consulting with the firm in the UK over the installation of heat pumps at the development.
Following a visit to Eastern Asia, the two developed the system that has been installed at Kingston-upon-Thames.
The team has constructed a small pump house alongside a berthing dock, which once handled barges carrying coal and coke to fuel the old power station.
Here an abstraction pump system has been secured to the riverbed using a series of needle piles. Up to 150 litres of water per second are abstracted and taken through a two-stage filtration process.
Water then passes through high-efficiency heat exchangers to harvest the low-grade heat before being returned to the river.
These heat exchangers transfer this heat to an internal closed-loop water system that carries it to a plant room inside the development.
From there the water is distributed to 37 Mitsubishi Electric condensers, which boost the heat to the 45 deg C that is delivered to the apartments.
“It has taken a huge amount of time and effort to reach this point but it is definitely worth it,” Mr Spenser-Morris says.
The installation is expected to save more than 500 tonnes in CO2 emissions and is forecast to cut residents energy bills by 20 per cent.
Already the system is generating interest and has been welcomed by energy secretary Ed Davey, who labelled it a “game changer” in renewable energy provision.