Underground Heating: A Necessity For Airport Runways In Winter

Underground heating for airport runways is an idea that has been proposed to reduce delays and cancellations caused by ice and snow. While heated runways are not common, there are a few examples of them. For instance, ICAX™ Solar Runway Systems use underground heating to clear ice from runways and aircraft stands. This system captures summer heat from solar runways and stores it in ThermalBanks in the ground until it is needed to maintain the runway above the freezing point in winter. However, the main challenge to implementing heated runways is the high cost of installation and operation. For example, it is estimated that it would cost $53 million to install an electric heated wire system for a 150 x 10,000-foot runway, with an additional $8,250 for each hour the system operates. Furthermore, there are engineering challenges to building underground runways, such as the need for a wide unsupported span and the management of extreme turbulence caused by descending aircraft.

Heated runways can reduce cancellations and delays

Heated runways, which use conductive materials embedded in the tarmac or pipes supplying hot water, can provide a solution by keeping the runway surface above freezing. This technology has been trialled at some airports, such as O'Hare and Keflavik, and has the potential to reduce the need for mechanical snow removal and de-icing chemicals. Additionally, it can help airports meet their environmental targets by reducing the use of chemical compounds.

However, there are several challenges associated with implementing heated runways. One significant issue is the cost of installing and operating such systems. The Federal Aviation Administration (FAA) estimates that installing an electric heating system on a standard-sized runway would cost around $53 million, with operational costs of $8,250 per hour. There are also technical challenges, such as managing meltwater, which can cause safety issues if not properly addressed. Furthermore, the power requirements to keep runways heated are substantial, and the benefits may not always outweigh the costs.

Despite these challenges, some companies and researchers are exploring alternative solutions. For example, ICAX™ has developed a solar-powered runway heating system that uses photovoltaics to supply underground heating. This system has the potential to reduce costs and environmental impacts, but it still faces economic challenges. Overall, while heated runways have the potential to reduce cancellations and delays, they have not yet seen widespread adoption due to the cost, technical challenges, and the belief that the benefits may not outweigh the investment.

The cost of installing and operating a heated runway system

According to the Federal Aviation Administration (FAA), the estimated cost to install an electric heated wire system for a 150 x 10,000-foot runway is approximately $53 million. This figure represents a substantial investment for any airport, and the benefits would need to outweigh the costs for it to be economically viable.

The operational costs of a heated runway system are also considerable. The FAA estimates that it would cost around $8,250 per hour to operate the heating system. This means that running the system for an extended period during cold weather could result in significant expenses for the airport.

In addition to the installation and operational costs, there are also maintenance and energy demands associated with heated runway systems. The management of meltwater and ensuring proper drainage are critical safety considerations that require additional resources. The power requirements to keep runways heated are substantial, and the cost of energy can quickly add up, especially during prolonged cold spells.

While heated runways offer potential benefits in terms of reducing delays and cancellations due to snow and ice, the high installation and operational costs have been a deterrent for many airports. The decision to implement such a system requires a careful analysis of the benefits and costs, taking into account factors such as passenger safety, economic welfare, and the potential reduction in operation costs.

The environmental impact of chemical de-icers

While de-icers are critical for airport operations, they are also a major source of organic compounds that can contaminate airport surface waters during the de-icing season. De-icers containing propylene glycol and potassium acetate are a major source of organic pollution in airport surface waters. The compounds used in de-icer formulations are linked to a range of detrimental environmental and ecological effects, particularly if they are discharged into receiving surface waters before treatment.

The environmental effects of de-icers include the development of thick biofilm growths near the discharge location, resulting in adverse aesthetic and olfactory effects. Ecological effects include macro-invertebrate and fish fatalities, and the loss of migratory fish species such as salmon and sea trout. Toxicity towards aquatic flora and fauna is also a concern, primarily relating to the additive ingredients alkylphenol ethoxylate, a surfactant, and benzotriazole, a corrosion inhibitor.

The primary environmental concern associated with airport de-icing activities is oxygen depletion in receiving waters. This occurs during biodegradation when heterotrophic bacteria aerobically oxidise organic compounds in a process that consumes dissolved oxygen. The potential oxygen demand associated with contaminated runoff from airports can be quantified through the determination of biochemical oxygen demand (BOD).

To address these environmental concerns, airports are required to comply with stringent regulations, such as the European Water Framework Directive (WFD) and the environmental permitting regulations (EPR) 2010. These regulations set limits on the discharge of pollutants, including BOD, into the environment. Failure to meet these requirements can result in prosecution and the payment of damages.

In addition to regulatory measures, airports have implemented de-icer management plans (DMPs) to outline pollution prevention strategies and manage contaminated runoff. This includes conveying contaminated runoff to a local wastewater treatment plant (WwTP) or using treatment wetlands to remove pollutants from wastewater before discharge.

Underground runways are impractical to build and land on

Additionally, the tunnel's confined space would make it challenging for planes to take off due to the horizontal version of vortex ring state. The tunnel would need to be significantly wider than the wingspan, and even then, precision from the pilot and engineers would be crucial. The cost of such a project would be astronomical, as underground construction and tunneling are incredibly expensive. For example, subway systems can cost hundreds of millions of dollars per mile.

Furthermore, maintaining a safe and functional underground runway presents several challenges. Dedicated ventilation systems would be essential to managing jet exhaust, sound, fumes, and pressure. Fire safety would be another critical concern, as fires in an enclosed space could be catastrophic if people do not understand the ventilation system or if doors are locked. Rock mechanics, roof bolts, and shotcrete would also need to be carefully considered to ensure the structural integrity of the tunnel.

The potential for foreign object debris (FOD) is high if the tunnel is not fully lined, creating hazards for aircraft engines. The size of the excavation would also need to account for the approach path of the aircraft, making it even more massive and costly. In conclusion, while underground runways may seem like a novel idea, they present numerous engineering, operational, and financial challenges that make them impractical to build and land on.

The challenges of heating a runway

Heated runways are not a new idea, but they have not become popular despite the obvious benefits. So, what are the challenges of heating a runway?

Cost

The most significant challenge is the cost. Installing an electric heating system under a 150 x 10,000-foot runway is estimated to cost $53 million by the Federal Aviation Administration (FAA). This is a huge amount of money, and this is before the running costs are considered. The hourly operational cost of the heating system is $8,250, according to the FAA. These costs are likely to be prohibitive for most airports.

Power Requirements

The power requirements to run a heated runway are immense. The electricity needed to melt snow is huge, and this would need to be generated by the airport or bought from the grid. This is likely to be very expensive and could impact the wider power network.

Meltwater Management

The management of meltwater is a significant challenge. If not properly managed, it can cause safety issues and may even require more mechanical snow removal.

Maintenance

Maintenance of the heating system would be a complex and costly process. The system would need to be durable enough to withstand the weight of aircraft, which have much higher weight on each tyre than cars.

Safety

Heating a runway could potentially create safety hazards in certain weather situations. For example, the heat could create fog above the runway, reducing visibility.

Alternative Methods

There are already tried and tested methods of dealing with snow and ice on runways. These include snow ploughs, chemicals, and de-icers. While these methods can cause delays, they are generally effective and do not require the huge investment of installing and running a heating system.

In conclusion, while heated runways may seem like a good idea, there are several significant challenges that need to be overcome before they can become a reality.

Frequently asked questions