King's Cross Cooling Energy Centre & Network

Proximity to the HS1 trainline brought many challenges to the project.  This included routine issues such as working with Network Rail to ensure all nearby crane works were acceptable to more in depth concerns which needed design-led solutions.   There was a concern from Network Rail, for example, that pluming from the plant could drift across the rail tracks and impair drivers’ sight lines. The concern was so great that it was agreed that substantial financial penalties would be imposed if trains were disrupted by pluming.

This restriction resulted in the need for a robust solution which could be relied on under all circumstances and weather conditions.  The design of the energy centre includes three different types of chillers; absorption, water cooled and air cooled, which each produce chilled water.  The absorption chiller, which converts waste heat from the T1 energy centre into cooling, only initiates when the external temperature reaches 17°C or above which eliminates the possibility of pluming.  These three types of cooling are controlled by a sophisticated Building Management System which ensures the correct combination of cooling is in use at any time.

Where possible, the system utilises the excess heat from the T1 energy centre.  If this heat is not available, as it is being used for heating in the colder winter months then the system will switch to the water source chillers as they are more efficient than the air chillers (during these colder environment conditions).  When the temperature creates the possibility of pluming the system switches to the air chillers.  All three of these types of cooling are extremely efficient and as the grid decarbonises, the air and water chillers result in lower carbon emissions.

The Cooling Pod is capable of producing 12.4MW of cooling but as standard will deliver 9MW.   The Cooling Pod plant comprises a 1.4MW absorption chiller, three 3MW water-cooled electric chillers, two 1MW dry air-cooled chillers and two 30m³ thermal stores.  Crucially, the solution also has two 2.5MVA transformers which gives added resilience, allowing cooling to be maintained should one fail.

A major benefit of the cooling solution is that it makes the overall energy scheme more efficient. An electric chiller operates during the majority of the year when the cooling demand is low, but in the warmer summer months, the waste heat which is generated by the CHP engine is transported to the cooling pod, converted into chilled water through an absorption chiller and then distributed via a network of district cooling pipework connecting office blocks, residential and the King’s Cross Coal Drops facility.

The hot water is produced by the CHP in the T1 energy centre and pumped through 80m of buried, pre-insulate, twin series pipework.  Once the heat has been converted into cooling through the absorption chiller it is distributed through a district cooling network which is currently made up of 680m of Series 1 pre-insulated pipework.

This network currently connects two buildings, but this will expand to four commercial and three residential, with the Cooling Pod able to deliver 9MW of cooling overall.  Whilst the installation of district cooling is the same process as district heating, it still encountered some substantial technical hurdles which required a 38m thrust bored tunnel which allowed it to avoid the High Voltage electric cables and gas mains in its path.

One of the biggest restrictions for the project was noise, which severely limited the acoustic emissions from the plant and this called for the design of a specialist, bespoke solution.  Our designers worked very closely with the project acoustic specialist to create a range of internal acoustic insulation to ensure noise emissions were acceptable to the planning conditions’ noise criteria.  The most innovative part of this solution saw the creation of an acoustic green roof to attenuate the noise of the cooling towers and air cooled chillers.  This ensured acoustic emissions fell within acceptable parameters, but also provided an attractive architectural feature for the structure.

The commissioning process is an essential step to ensuring the energy installation will perform as designed.  Vital Energi consider this to be one of the most important steps in designing an efficient and reliable energy solution and the King’s Cross Cooling Pod project presented several interesting challenges.

Firstly, the project was commissioned before the heat loads were connected to the network.  This resulted in our Prefabrication department creating a custom made Heat Load Bank which enabled us to run the system as normal, thoroughly testing every aspect to ensure it was performing optimally.

Any pluming from the cooling towers could be dangerous to the nearby trains and would result in significant fines.  Vital staff arranged to test the cooling emissions during overnight sessions when the trains weren’t running, negating the possibility of any issues.  During the commissioning process the system performed as predicted meaning we could have full confidence that it would not interfere with the nearby train line.

Our solution met all legislation and planning conditions and restrictions while satisfying the client’s brief and resulted in a cost effective, energy efficient cooling solution which will benefit the surrounding development for years to come.