Keeping The Head High Of High Rise Buildings Good Power Quality

Published On: Oct 05, 2020

Vertical growth has always been an imperative compulsion in urbanization. The high-rise buildings may not reflect the magnitude of urbanization, but they have always held an iconic importance, in promising a solution. With the surge of high-rises in every city around the world, there is now an increasing concern on taking 360deg holistic view for the functionality of such high-rise buildings – by continuously improving their performance on efficiency, reliability and safety. In this blog, we review the use of good Power Quality in achieving the same.

INTRODUCTION

Buildings, in many ways, are like a living organism. They consist of multiple systems that must work in harmony with each other to function and flourish. They need energy and power to run (food), maintenance to perform (exercise), refurbishment to grow (regeneration). It’s the symbiotic relationship between the various systems in the buildings – electrical, mechanical, power electronics, the equipment, infrastructure and the people that contributes to the survival and success of the building’s life. Buildings are exposed to changes, pressures and tough conditions, both internally and from the outside. And like every life, the buildings also age. To survive, buildings need to stay fit.

The DNA of a building’s fitness and survival is hidden in several strands. The design standards encoded in every system to final workmanship, testing and maintenance, every strand is vital to Building’s functional sustainability. The Power Quality and Energy Efficiency are two such genes that define the sustainability of the Building’s performance.

This blog reviews the nature of the Power Quality and Energy Efficiency genes – their character, science and importance for building’s longevity.

SUSTAINABLE VERTICALISED URBANIATION – PQ MATTERS!

High rise building is essentially a building with a small land footprint, small roof area and very tall facades. The differentiation from conventional buildings is in the special engineering systems it requires from building construction, materials or the electrical design and workmanship.

From a standards point of view – The International Building Code (IBC 2000) and the Building Construction and Safety Code, NFPA 5000TM-2002, define high-rise buildings as buildings 75 feet or greater in height measured from the lowest level of fire department vehicle access to the floor of the highest occupiable story. According to National Building Code buildings and structures having total height of occupiable or usable space of more than 28 meters above the lowest grade or lowest level of Fire Service Access into that occupancy is categorized as High-rise Building. State Municipal Councils or Development Bodies also indicate norms for high rises, from time to time, for approvals and certifications in their areas. However, the local standards are typically never considered in practice for design or planning of the buildings.

Land in cities is scarce and expensive and tall buildings represent a lasting solution. In Egypt for instance, only 4% of the terrain is where the entire population has chosen to live – making tall buildings an important element to achieve high-density development.

Vertical growth is essential for the city’s sustainability. But the sustainability of the vertical growth is itself under the scanner many times. Whether it’s an incident of fire in a high-rise building or a rising unauthorized colony, or the people stuck in an elevator for hours together – the questions about the safety and reliability of such facilities put them under the scanner.

High rise housing around the world is predominantly of two types. The first, and the one popularly known, is the high-rise structures – planned and built by professional architects, executed by qualified agencies. The other category is the high-rise housing, self-built by residents or local communities. It includes a wide range from vertically growing slums to occupations (authorized or unauthorized) of unutilized high-rise spaces in the cities that is home for tens of thousands of underprivileged people. With the Covid-19 crisis several high-rise spaces in India and around the world are expected to stay vacant or go defunct – only indicates the growth in such spaces in near future.

Examples of self-built high-rise urban spaces

Kowloon Walled City – (Hong Kong) a 14-story-high, 700-foot-long unplanned megastructure was once the densest housing development
Tower of David slum (Venezuela) rose above the city for eight years with permission by Hugo Chavez’s government to colonize the skeleton of an unfinished 45-story corporate skyscraper
Dharavi (India) – has technically quite a few high-rise buildings in a dense and unplanned setting – housing residences and industries of all types

Contrary to the above, the planned high-rises are the icons of engineering excellence and project management. In fact, globally, the two indicators for City’s brand and development index are its iconic high-rise buildings and the number of high-rise buildings housed in the City.

These iconic building further lead to a high-rise boom in the region. For instance, in Lower Parel – upmarket and densely populated area in Mumbai, Lodha World – a 117 storied building in turn lead to a high-rise boom with several 80+ floor buildings came up to surround it.

China for example has 13 of the world’s 20 tallest buildings. A position previously held by the US for a long time. This has sort of fueled a race as well as inspiring the growth of high-rises and also setting the direction for the City’s future growth.

The one thing that’s common about both kind of high-rises is the longevity. It’s almost always more than the life expectancy of its occupants, systems and the surrounding environment.

One example to support the point above is the Empire State Building Retrofit which surpassed Energy Savings Expectations. The building was built in 1931, in the New York City. Today, it is one of the oldest tallest standing buildings in use. The building has changed hands in terms of its occupants and the agencies that manage the upkeep and maintenance. The Energy efficiency measures were performed jointly by Johnson Controls and Jones Lang LaSalle totaling to first year saving that added up to $4,393,796. In the process quite a few physical and electrical elements of the building were revamped. These included window panes, Chiller unit, installation of Variable Air Flow Systems, introduction of digital controls and lighting changes. At the core of supporting such sweeping changes successfully is the electrical foundation of the facility that was placed years ago.

The building’s electrical network had to continue to deliver power in a safe and reliable way as the building’s load, occupants, and usage was undergoing change every time. Power Quality is the secret and also the measure of how successfully the high-rise building is able to adapt to change over its lifetime. And not all buildings are good at it!

However, there are examples on the other end as well. Take the world’s tallest building, Burj Khalifa in Dubai, which had saw the closure of its famed viewing platform only after a month of its opening due to electrical problems. It not just caused irritation to the enthusiastic tourists who had pre-booked tickets to the ride up the building’s top floor but also hit Dubai’s reputation as a luxury destination. It also cast a shadow back then on the 12,000 odd permanent residential and offices who were to occupy the facilities in the same month.

COPPER PROTECTS QUALITY POWER IN HIGH RISES

The case of Power Quality Problems in Columbus, Ohio, High-Rise Office Tower

Capitol Square, an attractive 27-story, 400,000-sq ft office tower in downtown Columbus, Ohio was built in 1982. Growing loads and some false economizing taken at the time of construction caught up with the original system.

When Jones Lang LaSalle (JLL) took over management of the property for its owner in 1998, the old wiring system had become a noticeable problem.

The problems

Every Friday afternoon, a fuse would blow, or a breaker would trip at around 2:00 pm, and all lines that were fed from that floor would lose one of the three phases. With the way building is wired, maybe half the building would be down for several hours.
Growing loads were a key issue as the building was constructed for a power load of 3 W/sq ft, in 1982 and the tenant today wants 8 W/sq ft for general- service loads (including computers) and 4.5 W/sq ft for heating and lighting.
Feeders from the transformer to the floors below were wired with 4/0 aluminum.
Transitions from aluminum to copper on floors 17 through 26 were made improperly
Many of the connections were loose and Breaker cabinets on floors 17 through 26 also contained improper neutral-ground connections
The Grounding of the building was not anywhere close to supporting the modern office’s load requirements which included computers, lighting and other sensitive equipment

JLL replaced the existing feeders with 100% copper conductors and listed copper lugs and connectors whenever any new circuits are installed. The specifications could become a model for other properties managed by JLL. As a result, recurring problems vanished when Copper replaced Aluminum Feeders in the building. The tenants and facility management company had to bear the price of earlier economizers.

Summary adopted from source: https://www.copper.org/applications/electrical/pq/casestudy/high_rise_office_A6095.html

The case above clearly shows how the importance of following design and sourcing standard codes that would suffice not just the immediate but the distant future. The electrical systems in the high-rise buildings must be designed and built with a 100-year life-cycle in the mind. This is where most miss the point.

Short sightedness and opportunistic approach are certain to cost the building’s safety, reliability and efficiency, often making it unhabitable. The short-sighted and misplaced cost economizers have the power to transform the outside iconic structure to become an unlivable space from inside. That is to say the experience and ‘quality of life’ would be no different from the unplanned self-built high-rises of the city mentioned earlier.

RETROFITTING TO IMPROVE ENERGY EFFICIENCY IN HIGH-RISE BUILDINGS – THE ROLE OF PQ

Poor PQ can affect the energy efficiency of the building. Whereas, good PQ is a natural booster for Energy Efficiency. With rapid improvement in energy efficient (EE) technologies, the economic benefits of upgrading older high-rise buildings is extremely high. The general trend of adding electronic controls in building systems which provide better control, lower maintenance costs and much higher efficiencies is also on the rise.

Typically, the low hanging fruits here would include variable speed drives to replace standard motors used in ventilation, air-conditioning, water pumping systems, LEDs to replace incandescent or fluorescent lights and switched-mode power supplies to replace conventional power supplies. However, the adverse impact of energy-efficiency projects on PQ is not understood well and leads to significant increase in losses.

As a thumb rule, EE retrofits focus on saving the energy by optimizing the environment controls for human comfort. The second dominant theme is to generate own power using rooftop or on-site solar PV. Both require addition of non-linear loads – a key concern for PQ. We are also expecting EV wave hitting soon our shores.

PQ problems can be corrected using many solutions. The most advisable among all would be to arrest the PQ problem at the planning and design stage itself that is at source. But this may not be possible always while retrofitting. For instance, LED lighting systems could use localized DC distribution, fed from a converter/controller, where PQ measures must be applied as an input to the controller. It is also common to fit LED controllers with a dimming function for better efficiency. The degree of dimming affects would influence the shape of the input current waveform and pose a threat to PQ. The increased concentration of SMPS based loads can severely impact the neutral conductor by overheating and catastrophic fire caused by failure of insulation. This needs double sizing of neutral even 4 times the phase conductor size if load is highly nonlinear. Similarly, local UPS, inverters and battery chargers used as back up for emergency must be above board to ensure good PQ. This and several such instances necessitate the need for PQ mitigation in a retrofit project.

PQ Monitoring – the continuous quest for improved PQ with Energy Efficiency
The loads in high-rise Buildings could change significantly over years. Changes and replacement of the energy efficient devices especially have the potential to alter the PQ status. PQ monitoring on a continuous basis has emerged as a permanent check on the PQ and effective measure to bring about PQ corrections, including identifying the source of PQ problems. The continuous PQ monitoring coupled with Energy Efficiency initiatives will provide an accurate know-how on the increased risks on the PQ side.

PQ, BUILDING CODES AND HIGH RISE BUILDINGS IN INDIA

As of now, the collective average age of super high-rise/tall building in India is quite low as compared to the ones in USA. That is to indicate a majority of the high-rises built in India are recent, mostly in the last 10 years, whereas most high-rises built in the USA are already 20+ years older. Purely in terms of their age, the Indian high-rise buildings are quite young. But they already show quite a few signs of early ageing. The increasing incidents of fire, constantly failing systems within the buildings and higher maintenance requirements – all raise questions on sustainability of such buildings. The root cause is often not following the right building design and construction practices as prescribed by the National Building Codes and other relevant agencies.

The adage goes: “code represents the worst possible building that can legally be built.” What was true for energy efficient buildings of the US fifty years ago, is probably true for PQ for today’s high-rise buildings. The oil usage penalties imposed in the US in 1970s forced the design industry to consider saving energy. There was no national policy in the USA at that time. ASHRAE came up with a standard for the energy-efficient design of buildings, Standard 90, and published in 1975. ASHRAE also developed Standard 100: Energy Efficiency in Existing Buildings to provide “greater guidance and a more comprehensive approach to the retrofit of existing buildings for increased energy efficiency.” There is a specific standard for high-rise buildings today and its being followed to the core in the US building construction and services industry. The case in India, however, is far more complicated.

The National Building Code 2016 (NBC) govern the building construction norms in India. The NBC also comprises various guidelines and provisions for regulating and preventing fire in Indian buildings. But going by the adage mentioned above, the tendency in India is to ensure an on-paper compliance rather than a strictly on-field compliance when it comes to various standards and codes. Compared to energy efficiency, building a consensus on PQ is even more challenging. The energy efficiency standards are constantly rising, and the codes often outpacing the other guidelines issued by the local and national authorities. It’s about time that the PQ parameters are given their due importance in the defining the codes and standards of electrical design, materials and workmanship. You may have world’s best design but if executed by mediocre skilled workforce using economized material the catastrophe is waiting to happen. Otherwise, there is a high chance that PQ emerges as the regressive gene in the building’s DNA, altering its life and performance capability forever.

CONCLUSION

Good Electrical system design not just using high class products and Power Quality has a lasting impact on high-rise buildings and the criteria of using them as an efficient urban development instrument. But achieving this depends on how the Govt. and local institutions control the use of ad hoc methods, materials and workmanship and lack of integrated approach in design of high-rise building. High-rises are an economic phenomenon in the modern society. Their sustenance is critical to the sustenance of the city living itself and the quality of power that runs through the veins of the building is therefore a vital element in making it so.

The destruction of 110-story twin towers on the Sept 11, 2001 sent a strong message to the world. The impact on engineering codes, fire protection and in general the safety of high-rise buildings and their increasing technical sophistication is under constant question. While 9/11 could be considered as an exception, the preparedness of high-rise buildings for the exceptions – small or large is an ongoing process in their evolution. The need for specific building codes and emphasis on Good Power Quality is a defining strand in ensuring sustainable functioning and long life of high-rise buildings.