Many airports have substantial on-site power and heat and/or cooling loads that are a good match for a local cogeneration plant. A debate is now underway in India and elsewhere in Asia about the merits of locating plants at new and refurbished airports, as Raghavendra Verma reports from New Delhi.

Location is obviously key to on-site power production. But what if traffic safety issues make it impractical to locate a major power plant right next to an industrial consumer? Dedicated airport power plants face this issue: can a plant 20 or 30 km from an airport really be considered on-site power, especially if its electricity has to dip in and out of the national grid to reach its destination? And does this negate the benefits of locating power plants close to major customers?

Such issues are being considered carefully in the debates now brewing over plans to build a power plant to safeguard the electricity needs of New Delhi’s Indira Gandhi International (IGI) Airport and to prevent neighbouring customers from suffering, even during shortages.

India is, of course, a key case study in the debate over how to meet power demand in a country with a growing economy. Should central planning or decentralized dedicated power plant construction prevail – or a mixture of both? And, if both strategies are employed, then how should they be linked to maximize benefits to producers and consumers?

The issue is particularly critical in an energy deficient country like India, where planned increases in installed power capacity are unlikely to keep pace with demand. The market must accommodate this demand, but how can this be achieved in a controlled and efficient manner?

Indira Gandhi International Airport’s new T3 terminal
Indira Gandhi International Airport’s new T3 terminal
Photo: Raghavendra Verma

INCREASING ENERGY LOADS

Indira Gandhi airport clearly faces a problem under the existing power supply system. The use of air conditioners to cool its glass-rich buildings in India’s hot summer months – essentially March to October – imposes a significant and sustained increase in the demand for power and the existing dependence on the overloaded grid is not the best option. The airport’s new Terminal 3 currently requires a generation capacity of only 80 MW but this is set to double by 2013 as annual passenger traffic rises from 40 million to 60 million and commercial complexes are developed in and around the airport.

Given this anticipated increase in electricity demand, it is no surprise that Delhi International Airport Limited (DIAL), a subsidiary of main airport operator GMR, is considering how to secure the power it needs by building a 420 MW gas-powered plant. A DIAL spokesperson told COSPP that the company is evaluating various options and needs to take strategic decisions soon. The airport operating company will almost certainly run the new plant itself. Construction is expected to be in two phases, each of 210 MW, with construction of the second beginning after the first is completed.

GMR has plenty of expertise in electricity production as it operates three power plants with total capacity of 800 MW: a 200 MW plant in Tamil Nadu that runs on a diesel turbine supplied by MAN B&W, Germany; a 220 MW plant in the state of Karnataka that uses aero-derivative gas turbines made by GE; and a 370 MW plant in Andhra Pradesh that operates with advanced class gas turbine technology also from GE. All supply the grid. GMR also has eight new power plants in the pipeline with a total capacity of 3680 MW, including two in Nepal based on coal and hydro power.

But the planned airport plant would be in Jhajjar, 60 km from the terminal in Haryana state, according to reports in Delhi’s Hindi language newspapers that the company is declining to confirm. The reports stress that the airport company has also requested that India’s ministry of petroleum and natural gas allocate 1 million m3 of natural gas per day for the first phase of the project. The country has an acute shortage of natural gas and major sales contracts are regulated by the government. The long queue of hopeful purchasers waiting for necessary approvals, includes proposed industrial units producing anything from power to fertilizer.

This may well not be the only key government permission that the project requires. The proposed plant‘s distance from the airport raises doubts that it can be a truly captive power generation facility: first, it is highly unlikely to get the necessary government permission to set up its own high tension cable lines to transmit electricity at high enough voltages; second, laying such infrastructure over such a distance would make this project too costly to be commercially viable.

If the company concludes – as is expected – that it cannot lay its own cables between the plant and the airport, it would have to depend upon the existing national grid network operated by Power Grid Corporation of India, a central government-owned company, to transmit its power. This would cost the airport the dependability and control that is such a useful facet of on-site power generation and force it to rely on the often patchy performance of the Indian grid. Voltage fluctuation is common across India and commercial and industrial units often have to install voltage stabilizers to protect sensitive equipment from unannounced power supply failures.

In November 2010 Mumbai city airport experienced a 20-minute power failure that two local power distribution companies – Tata Power and Reliance Infrastructure – blamed on each other. Flight schedules were unaffected, however, as emergency power supply kept essential services such as runway lights and x-ray machines functioning normally.

WHEELING POWER

Being connected to the grid can also offer benefits to an operator-owned plant. In this way, GMR can be assured of officially sanctioned ‘wheeling power’, whereby it has the absolute right to draw the same amount of power from the grid that its power plant has injected down the line. Another bonus is the opportunity to sell excess power to the grid, thereby ensuring enough electricity is available through the grid locally not only to feed the growing airport but also to boost the availability of power in the capital and neighbouring towns.

As an immediate step to fortify the power supply to the airport, in September 2010 Delhi Transco Limited (DTL), the state transmission company, set up a 220 kV power sub-station exclusively for the airport and the metro railway line connecting it to the city centre. DTL supplements the national grid by providing smaller – 400 kV and 220 kV – transmission networks.

The choices facing GMR also confront a wide range of commercial and industrial players in India. Without the safety issues that affect airports, the benefits of on-site captive power plants are only too clear. The lack of reliable and stable power supply makes self-sufficient plants vital to their operations. The central government also provides support for developing on-site power – although this backing is restricted to plants fuelled by non-conventional energy sources such as solar, wind and biomass cogeneration, while many on-site plants run on coal or gas to ensure their commercial viability.

Yet Indian captive plants have a limited generation capacity, ranging between 10 MW and 30 MW. Also, while incredibly useful in eliminating sudden power losses or high-voltage power surges and in enabling all operations to be integrated under one management, these plants do not necessarily produce cheaper power than the grid.

For airports, as such major consumers, this is an important issue. In addition, government designation of airports as essential services, with air traffic control services seen as especially critical, makes power distribution companies try to provide them with more stable power while shedding load – and cutting power – elsewhere when demand outstrips supply. This obviously reduces the benefit to airports of investing in on-site power.

Delhi power distribution centre
Delhi power distribution centre
Credit: Raghavendra Verma

Furthermore, Indian airports already have their own emergency contingency power systems. Each Indian airport has diesel generators that can meet 50% to 80% of its power requirements. Designed essentially for critical and emergency operations, they have to be rested after every eight hours or so, yet most airports have more than one generator so they can run essential systems for days, albeit at a much higher running cost.

The Airports Authority of India (AAI), a central government agency operating 115 smaller airports in India and two larger terminals in Chennai and Calcutta, depends extensively on backup systems and is not considering a substantial on-site power generator facility for any of the airports.

Yet demand for power at AAI run airports runs much lower than at modern airports – at new airports in Delhi, Mumbai, Hyderabad and Bangalore the authority is responsible only for maintaining air traffic control services. For buildings that can accommodate 30 million passengers annually the AAI generally currently requires only 20 MW of power. However, many AAI-run airports have yet to become fully air-conditioned, a change that would raise the demand for on-site power even for these smaller airports.

HEATING AND COOLING

In the meantime, the AAI has recently started installing at some of its airports solar panels that range from 100 to 500 kW, maintained by suppliers on a long-term contractual basis. The panels are mainly used for street and parking lights. They cost two to three times as much to install as diesel generators of equal capacity, but offer environmental benefits and cost savings in fuel inputs. The Himalayan airport of Leh, 3200 metres above sea level in Ladakh, in Jammu and Kashmir, provides an unusual example. Here the AAI aims to install 100 kW solar panels on the roof of a new terminal building to provide heating, a rare requirement in India. The project is due to complete in 2012 or 2013 and to cost more than $1 million.

Water heated by the solar panels will be circulated through coils to warm building in this mountain desert where temperatures can plunge 20 degrees below freezing. Ladakh depends mostly on hydropower but in winter, when heating drives a surge in demand, reduced river flow often triggers severe shortages. Electric and diesel powered boilers currently heat the airport.

Solar power has added importance for airports because wind power is usually ruled out by the visual and physical obstacle that turbines can pose to aircraft and air traffic controllers. Airports are also typically sited to experience low wind speeds, which aids safe take-offs and landings.

CUTTING SITE LOADS

An AAI spokesperson told COSPP that it is assessing future cogeneration projects in its airports for recovering heat or steam from power generation. But no formal and specific plans have been released. Unlike in Europe, or indeed Ladakh, most airports in India require heating or hot water for only a few months in a year. On the other hand, with most of India’s summers being very hot and long, cooling is a key issue. A holistic approach is therefore being developed towards airports that incorporates on-site power and cogeneration but considers these issues alongside ways of conserving power and optimizing the use of natural resources.

For instance, in Hyderabad, south India, when planners sat down to design a greenfield airport, the top priority was reducing energy demand, rather than ensuring a major on-site power plant guaranteed energy supplies. Interestingly, this happens to be the only other airport built and operated by GMR – although it also operates Malé International Airport in the Maldives and Turkey’s Istanbul Sabiha Gokcen International Airport.

Indira Gandhi International Airport’s new T3 terminal
Indira Gandhi International Airport’s new T3 terminal
Credit: Raghavendra Verma

Hyderabad airport’s capacity demand is 66 MW, 25% less than a similar facility without environment friendly measures. Its energy efficient features include: overhangs and vertical fins to reduce solar gains; high performance glass with low shading coefficient and optimum visual light transmittance; efficient grid-powered air-conditioning; efficient lighting using T5 lamps; naturally lit common spaces with photo sensor-controlled electric lighting; and energy-efficient primary and secondary chilled water pumping.

To tackle Hyderabad’s peak summer temperature of 40°C, GMR installed energy efficient air conditioning chillers and heat exchangers. It designed the system so that heat from the air conditioners is released through water to reduce its heating effect outside and to generate hot water for various uses throughout the airport. All its chillers have variable frequency drives to make them 30% more energy efficient than standard models. Furthermore thermal insulation has been installed within the ducts, sidewalls and the glazed facade of the building.

Three hundred days of sunshine provide huge natural resources for light at Hyderabad: lighting ducts in the five-layered insulated roof of the new airport’s terminal building make supplementary lighting unnecessary.

GMR has also tried to use its environmental nous at New Delhi’s Indira Gandhi airport. This April it won a ‘Leadership in Energy and Environmental Design’ (LEED) gold rating from the local chapter of US Green Building Council for aspects such as sustainability, water efficiency, energy and atmosphere, materials and resources, indoor environmental quality and innovation in design. That said, New Delhi airport terminal has been criticized on energy usage grounds. Sunita Narain, director of India’s Centre for Science and Environment, has branded it a ‘shopping mall’ and criticized it in a news article in the Times of India for being deliberately designed to be massive, so it takes time to walk to the aircraft through 20,000 m2 of shopping. ‘Just think of the millions of square inches of built-up space inside the airport that need to be cleaned, serviced, cooled, heated and lighted,’ she wrote. She claims that the two old terminals that the third terminal replaced consumed only 12 MW power while catering for 25 million passengers a year, while the new one already uses 80 MW. ‘The airport needs a dedicated power station for itself. In this great Indian sale, do we ever consider such material maths?’ she wrote.

Furthermore, at various sections of Indira Gandhi airport, many lights remain permanently switched on, despite the many large glass windows. Experts have suggested improvements whereby lights close to windows are switched off by day and interior lights in the aisle can be controlled through motion sensors sparked by moving passengers. ‘Power saved is power produced’ is a slogan being peddled by Indian government campaigns to conserve energy.

Raghavendra Verma writes on Asian energy matters from India Email: cospp@pennwell.com Additional reporting by Keith Nuthall

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