Steam power in New York City

New applications for steam in the Big Apple

By most accounts, the steam age ended decades ago…but not in New York.

When you think of New York, you probably think 'Empire State Building', 'Big Apple' or terrorist attacks of '9/11'.  With a bit of prompting, you might consider yellow cabs, bagels and, of course, the Statue of Liberty.  But somewhere in the depths of our media-informed minds are images of plumes of steam issuing from the streets.  So what’s this all about?  Why is New York steaming?

The reason is that steam is a standard utility in the city, alongside electricity, water and sewage.  Indeed, it might come as a surprise - in a world that largely associates steam power with the golden age of rail - that the buzzing, skyward-thrusting metropolis of New York City boasts 'the largest steam system in the world'.

In fact, steam is generated at no less than eight plants in the area and distributed for heating, hot water and air conditioning to customers from the southern tip of Manhattan to the area bordering Central Park - a service that dates back to 1882.

Consolidating power

The company currently known as Con Edison traces its history back to 1823 and the foundation of the New York Gas Light Company, which received a charter from the State Legislature to lay gas pipes across the lower tip of Manhattan.  Like most early gas companies it concentrated on street lighting, but on 4 October 1824 the Cherry Street residence of Samuel Leggett, one of the company’s founders, became the first house in New York to be illuminated by gas.  By the end of the decade, there were half a dozen gas companies competing for customers and even ripping up their rivals’ gas mains when installing their own.

When Thomas Edison demonstrated his incandescent light bulb in 1879, the writing was on the wall for gas lighting and the gas companies began to shift towards heating and cooking applications.  And in 1884, with too many companies competing for the same business, it also prompted the formation of the Consolidated Gas Company of New York.  In what we think of today as a relatively modern business gambit - ‘diversification’ - Consolidated Gas recognised that other energy sources would play an important role in the development of the city and began to acquire electricity companies and steam generation businesses.

Interestingly, at around the time Edison was developing his concept for a central electricity generating station, the lesser-known Birdsill Holly of Lockport, New York, was working on another centrally produced energy source: steam.  Known as the 'father of district steam heating', Holly had, by 1882, registered 50 patents related to steam heat and extended his district steam system to other cities across America.

But it was Wallace Andrews, one of the original directors of the Standard Oil Company, who took on the challenge of providing steam to a city the size of New York when he acquired the franchise and licensing rights to deploy the Holly system in 1879.  Working with Charles Emery, a leading steam engineer of the day, he divided the city into ten heating districts, acquired land for central boiler plants and began to lay the steam mains. Apparently, Emery would often meet Edison 'in the trenches', where they would discuss the challenges of building their respective energy systems.

According to Con Edison’s archive, New York Steam’s first boiler plant was located at the junction of Cortlandt, Dey, Greenwich and Washington Streets, which, as it turns out, is right at the centre of the area now known as Ground Zero, the former site of the twin towers of the World Trade Center.  Completed in 1881, the plant housed 48 boilers and incorporated a 69m chimney, which, coincidentally, made it one of the tallest features of the lower New York skyline, second only to the 86m spire of Trinity Church.  Apart from that, the district steam installation was so novel that it made the cover story of the November 19, 1881 issue of Scientific American.

By 1932, six stations provided steam heating to more than 2,500 buildings, including landmarks such as Grand Central Terminal, the Empire State Building, the Chrysler Building, Pennsylvania Station and the Daily News Building (which doubled as 'The Daily Planet' in the Superman movies).  A key marketing advantage, and a factor that ultimately affected the architecture of these buildings, was that centrally-supplied steam avoided the need for individual heating plants and smokestacks.

By that time, the diversified Consolidated Gas had become the world’s largest electricity supplier, and revenue from those businesses was, according to the company, 'far ahead' of that for gas. Consolidated Gas continued its diversification programme by acquiring some 75 per cent of New York Steam’s common stock and, in 1936, the business was renamed the Consolidated Edison Company of New York.

Steaming ahead

Today, Con Edison operates 'the world’s largest district steam system, with an installed capacity of about 13 million pounds per hour', using an infrastructure of some 170km of mains and service pipes to provide steam for heating, hot water, and air conditioning to approximately 1800 customers in Manhattan.  Indeed, the company is proud of the fact that some of the newer buildings - the Hearst Tower, Time Warner Center and 7 World Trade Center - 'have all chosen steam'.

Not surprisingly, a key advantage of today’s steam system is the same as it was a century ago: the centralised distribution that obviates on-site generator plant.  The importance of this in a city where, perhaps more than most, space is at a premium is not lost on Con Edison.  As its marketing literature points out, it reduces equipment monitoring and maintenance, while eliminating fuel delivery and storage.  This in turn reduces noise and vibrations inside the building, 'improving quality of life for…tenants', and releases space where the boilers would be 'as revenue-generating storage'.

Con Edison uses conventional fuels such as oil and natural gas - whichever is most competitive at the time - and more than 46 per cent of its district steam is 'cogenerated' (as a byproduct of electricity generation), which means that 'air emissions are lower and steam is cheaper', says the company.  This ‘cogeneration’ is otherwise known by the abbreviation CHP, for combined heat and power.

Steam is generated at seven company plants - five in Manhattan, one in Queens and one in Brooklyn - and supplied under contract from a plant at the Brooklyn Navy Yard.  Con Edison’s boilers burn either low-sulphur oil or natural gas, and utilise what the company calls 'state-of-the-art burners', which were installed as part of a joint project with the Electric Power Research Institute to reduce nitrogen oxide (NOx) emissions [see panel: Green Steam]. The height of the chimney stacks ranges from 100m to over 150m to improve the dispersion of emissions.  At the point of delivery, individual customers tap-off steam from the main using a service valve, much as they would for a natural gas supply.

While using steam to provide heating and hot water seems straightforward, its use for air-conditioning is perhaps less so.  In reality, the steam is simply an alternative driver for a 'chiller' (a machine that removes heat from a liquid via a vapour-compression or absorption refrigeration cycle), which can be driven either by an electric motor or a steam turbine.  Con Edison recommends a 'hybrid cooling plant', where one electric chiller in a typical three-chiller plant is converted to steam.  According to the company, this helps to 'reduce summertime electric-peak demand, therefore helping to reduce overall costs'.  Steam chillers are also said to be more flexible than 'all-electric' air-conditioners, because steam turbines have 'intrinsic variable speed control' and run cheaper during peak periods. They are also more space-efficient than chilled water cooling, because they avoid the need to store water that 'may or may not be used', thus making steam cooling a 'just in time' solution.

Not surprisingly, with the general increase in electrical load required for computer and video technologies and the increased frequency of ‘brown-outs’, the company is keen to push the advantages of steam as a flexible response.

Although its steam business currently accounts for only about 5 per cent of Con Edison’s total revenue, the company continues to make 'significant investments' in its steam-generating infrastructure.  Indeed, anticipating that peak demand for energy will increase by 10 per cent over the next decade, Con Edison intends to invest approximately $8 billion in its electric, gas and steam systems over the period 2009-2011.  Of that, the capital budget for steam production and distribution is 'approximately $400 million', according to company spokesman Patrick Wheeler.

Key challenges for the future are similar to those of any large company, adds Wheeler: 'Attract and retain profitable business, enhance system reliability, meet regulatory commitments, contain costs and protect worker and public safety'.  And where high-pressure steam is involved, the importance of safety cannot be overstated [see panel: Explosive Potential].

Iconic status

So what actually causes those plumes of steam rising from the streets. According to Con Edison, 'steam can come from manhole covers for several different reasons'. The most common is 'water infiltration', in other words water dripping onto a steam pipe.  However, the company does admit to leaks, either within the manhole or from piping buried between manholes.  It points out that 'there is no ‘natural’ venting process', so a plume of steam generally represents a problem of one sort or another.  Even today, the sight of an orange-and-white venting tube placed over a steaming manhole is a fairly common one on the streets of the Big Apple.

New York, New York - 'So Good They Named It Twice', according to Gerard Kenny - will always be a city of icons, whether it’s Lady Liberty or the Freedom Tower.  Although condensing water vapour billowing from manhole covers doesn’t quite have the iconic status celebrated by city fathers and tourism officials, it is an indication that even a 21st century city can be run, at least to some extent, on steam.

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