THE CHILTERN TUNNEL IS HS2’S LONGEST TUNNEL SPANNING 16KM, AND 90M DEEP AT IT’S LOWEST POINT. THE TUNNEL ALSO HAS FIVE SEPERATE HEADHOUSE AND VENTILATION SHAFTS ALONG IT’S ROUTE, FOR EXTRACTING HEAT AND ENTRY POINT FOR EMERGENCY SERVICES.
Overtime the London Clay surrounding the deep level tunnels has been saturated with heat released from the Underground. Rather than the absorbing heat into the clay, this effect now traps heat within the tunnelcaused the tunnels to heat up overtime, from air temperature of 14°C in the 1900s to 30°C in present-day. In an attempt to reduce fuel poverty and to make Islington a fairer place to live, London Borough of Islington has found a way to make use of the heat trapped in the tunnels. The scheme extracts hot air via heat pumps and repurposing them to heat up homes and leisure centres in the borough.
The controversial HS2 proposal (economic, political and environmental concerns), offers a chance to recover excess heat within bored tunnels. Trains generate heat through its movement via aerodynamic drag, air compression, brakes, and engine heat, the heat generated is trapped within bored tunnels and pumped out into the atmosphere. This offers an opportunity to restore the excess heat and convert it into energy to be used for various purposes such as, district heating, energy generation, drying biomass, warming greenhouse, waste water treatment, forest recovery. The approach provides a testing ground to further implication of heat recovery for rail infrastructure. The proposal is a catalyst for converting traditional rail vents into heat recovery centres, the modular design is intended to be reapplied to existing vents.
The simulation will explore the relationship between air and heat within and around a bored tunnel. The first simulation consists of four iterations of tunnel geometry, focusing on friction, pressure, and velocity changes and its effect on heat accumulation throughout the tunnel. Air velocity is the main element tested as it shows pressure changes and aerodynamic drag, which in turn signifies the change in temperature. The second simulation explores the radiation and permeation of heat from within the tunnel into the surrounding ground, through the use of a heat exchanger on the tunnel walls.
In priniciple a heat exchanger is the function in which two mediums, liquid or gas, exchange heat by passing through the other medium without coming directly in contact, the two medium is often seperated by steel panels of rods. The initial artifact is a representation of a heat exchanger expressed in a different form, using geometry and air simulations to improve its function whilst following the core principle of a exchanger,
The inflating heat storage ‘bubble’ is intended to restore excess heat from the HS2’s Chiltern Tunnel. The ‘bubble’ draws heat generated from rail friction, aerodynamic drag, engine heat and pressure change within the tunnel. The heat drawn is then transfered into the heat exchange chamber where cold air is brought in from the atmosphere to create a heat exchange process, as a result the newly generated warm air is transferred to the ‘bubble’ which will inflate as the heat accumulates. After a collection period of 3-5 days the warm air is then released to a processing plant which then uses the warm air for purposes such as, district heating, waste water treatment, drying biomass, generating energy, and forest restoration.
The inflation serves as a storage device and a dynamic display of the accumulation of heat recovered
Visitors can engage physically and visually in thermal experience and awareness in the heat recovery process
The inflation process begins as excess heat from the hs2 tunnel is transported into the heat exchanger coil. Cool air is then drawn into the thermal chamber, thus initiating the heat exchange process, converting cool air into warm air. Subsequently, the warm air is transferred into the ‘bubble‘ for temporary storage. After an accumulation period of 3-5 days, the warm air is then release to processing plant
Despite many controversies and protests against the hs2 proposal due to economical, environmental and political concerns the project is currently under construction. In light of these controversies, this project sets out to identify positive impact(s) from the proposal, to restore excess heat within the bored-tunnels. The heat restored can be repurposed in ways such as, district heating, waste water management, forest restoration, powering community hubs and many more. The project also strives to provide a ‘thermal experience’ for visitors and passer-by, to engage with the heat restored in a tactile manner and atmospherically, while raising awareness on the possibilities of heat restoration.
This project will also be a catalyst on approaching subsurface heat management. The artifact, heat storage bubble’s principle is modular and can be implement on existing and new vent shafts to recycle heat instead of dispersing them into the atmosphere. The form of the heat storage bubble is flexible depending on its purpose beyond the heat restoration.
As the outter ETFE panels are inflatable and deflatable, a retractoring motorhouse is required to pull down and secure the ETFE panel ensure its stability when deflated. Heat within the inner ETFE pillow permeated out into the outter ETFE panels and inflate it.
The air beams are connected the heat exchanger’s pipes through a rotation lock to ease installation and maintance. The connection point also houses a retractable vavle which will stop the flow of air back down the heat exchanger’s pipes when no hot air is being pumped into the air beams. Furthermore the internal skin of the air beams are lined with horizontal and vertical ribs to acceleration the air temperature, as previously explored in the heat-tunnel simulations,
ETFE is a recyclable fluorine based plastic, it is commonly used as an inflatable element in architecture. The material is fully recyclable and is consider more sustainable than glass panels, as it requires fewer structural supports and its lightweight allows of easier transport. Each component are manufacture off-site and brought in for assembly, lowering the embodied carbon in the construction process.
Fritting patterns are printed on to the ETFE foil/surface to control solar gain and control the opacity of the material. These patterns often consist of solid circular shapes or honeycombs with different interval lengths and sizes which will determine the amount of solar gain and light penetration.
