Cooling the Tube

Elsewhere, conventional air-conditioning units have been installed above platforms at Oxford Circus and Green Park, but these are expensive to install and difficult to maintain. 

Jamie Burns, a programme delivery manager with the cooling team, explains: “Where there are no shafts, it requires a different approach. St Paul’s was only made possible by an empty lift shaft, and the Victoria ground water project was a one-off. 

“We can increase the speed of fans where they exist, and install platform air management systems, which works well and generally takes six degrees Celsius off platform temperatures. But they are hard to service when they sit above public areas and running tracks. Actively removing heat using energy is expensive and has to be a last option.”

With restrictions on adding ventilation shafts in central London, and air-conditioning on or off trains generating additional heat to the environment, LU has been busy seeking a third way. In 2005 former London Mayor Ken Livingstone memorably offered a prize of £100,000 for suggestions from the public, but this failed to produce any workable ideas or concepts that LU was not already considering.

McInulty stresses that the silver bullet to reducing temperatures on the network can only come from placing the removal of heat within a wider mathematical equation. 

Historically LU has focused purely on taking heat out of the system, without serious efforts being made to reduce the amount of heat being put in. This has now become LU’s first preference. 

As 80% of inputted heat comes from train motion and brakes, and 15% from equipment including lighting, LU has been able to examine a host of ways to reduce how much heat enters the tunnels in the first place, thereby reducing the need for cooling.

“It’s not just about cooling, it’s a whole energy management approach. Power and cooling are two sides of the same coin,” says McInulty.

“There’s no escaping the fact that a more intensive service requires extra power. Trains coasting is a great idea to reduce acceleration and save power, but that’s hard when in some parts you’re running a service of over 30 trains per hour. 

“We can make gains from deceleration, and we are buying trains with regenerative braking, which produces electrical energy from braking rather than all that heat from friction. 

“And there are other things that go unseen by the public that make a difference - we have put a thin film on the windows of Central Line trains, so they absorb less energy on the outside parts of the line which is then dumped underground. We’ve also made massive steps in using LED lights which give out less heat.”

The aim of the game might be achieving lower temperatures, but it has not escaped LU’s attention that biting down on energy use will bring other welcome benefits, not least substantial energy bill savings and reductions to the network’s carbon footprint.

“Customers are always our priority, but so is efficient use of their money,” adds McInulty. 

“We have a £90 million annual energy bill, and it is incumbent on us to reduce that. We are clearly conscious of our environmental credentials, too, and measure that in all sorts of ways. We can become energy efficient, but having so much of the network outside also gives us a great opportunity to work with solar panels. 

“In the meantime, we will continue to incrementally reduce temperatures on the network, so it’s win-win all round.” 

Growing the network and increasing service frequency might be the most noticeable end-result of LU’s investment in meeting the demands of London’s growing population, but thanks to McInulty’s team and their hidden efforts, more comfortable temperatures may not be far round the corner. 

• This feature was published in RAIL 793 on February 3 2016