ctbuh.org/papers

Title: A Proposal to Create an Energy-Producing Megatall for Kunming, China

Author: Thomas Kraubitz, Senior Consultant, Buro Happold

Subject: Sustainability/Green/Energy

Keywords: Energy Efficiency Passive Design Sustainability

Publication Date: 2012

Original Publication: CTBUH Journal, 2012 Issue IV

Paper Type: 1. Book chapter/Part chapter 2. Journal paper 3. Conference proceeding 4. Unpublished conference paper 5. Magazine article 6. Unpublished

© Council on Tall Buildings and Urban Habitat / Thomas Kraubitz About the Council

The Council on Tall Buildings and Urban CTBUH Habitat, based at the Illinois Institute of Journal Technology in Chicago, is an international International Journal on Tall Buildings and Urban Habitat not-for-profi t organization supported by architecture, engineering, planning, development and construction professionals. Founded in 1969, the Council’s mission is to disseminate multi-disciplinary information on Tall buildings: design, construction and operation | 2012 Issue IV tall buildings and sustainable urban environments, to maximize the international interaction of professionals involved in creating Inside Canada’s “Marilyn” Towers the built environment, and to make the latest knowledge available to professionals in a useful Creating an Energy-Producing Skyscraper form. Fluid-based Aerodynamic Performance The CTBUH disseminates its fi ndings, and facilitates business exchange, through: the Ice, Snow and Tall Buildings publication of books, monographs, proceedings and reports; the organization of Assessing Korea’s Technology Potential world congresses, international, regional and specialty conferences and workshops; the Talking Tall with Bjarke Ingels maintaining of an extensive website and tall building databases of built, under construction In Numbers: Canada Rising and proposed buildings; the distribution of a monthly international tall building Reports: Shanghai Congress & 2012 Awards e-newsletter; the maintaining of an international resource center; the bestowing of annual awards for design and construction excellence and individual lifetime achievement; the management of special task forces/ working groups; the hosting of technical forums; and the publication of the CTBUH Journal, a professional journal containing refereed papers written by researchers, scholars and practicing professionals.

The Council is the arbiter of the criteria upon which tall building height is measured, and thus the title of "The World’s Tallest Building" determined. CTBUH is the world’s leading body dedicated to the fi eld of tall buildings and urban habitat and the recognized international source for information in these fi elds.

Council on Tall Buildings and Urban Habitat

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News and Events Features Research: Climate and Environment 24 2004 2010 % Change cause, but likely a tipping point for this Increasing Problems of Falling Ice and Snow Opaque Elements Insulation Min. R-Value Insulation Min. R-Value particular example. Other infl uencing factors could include: the move to more effi cient Roof (Insulation entirely above deck) R-15 R-20 33% on Modern Tall Buildings with under fl oor displacement ventilation Wall above grade (mass) R-5.7 R-9.5 67% Reported incidents of hazardous ice and snow falling from buildings are on systems, the heat loss characteristics of the Steel-framed walls R-13 R-13 +R-7.5 Cont. 58% whole façade as a system, and external factors the rise, specifically for recently completed tall buildings. High performance Fenestration Assembly Max. U Assembly Max. U such as elevation, building geometry and 02 This Issue 40 Tall Buildings in Numbers façades have improved internal thermal performance, but increased the Vertical glazing 0%–40% of wall U-0.57 U-0.50 14% orientation to prevailing weather. Overall, this conditions for forming ice on metal and glass skins. This paper sheds light on Table 1. Building Envelope Requirements – ASHRAE Standard 90.1 2004 – 2010 Comparison (Table 5.5-4, Building example reveals that as improvements in the issues, describing the factors that contribute to icing and hazardous ice Envelope Requirements for Climate Zone 4 - Non-Residential) © ASHRAE building performance are made, and exterior and snow formation, and provides methods to address these issues within the skin temperatures are reduced or at a minimum modifi ed, there is opportunity for Michael Carter Roman Stangl design process. Dennis Poon Canada Rising to newly completed high performance operators of recently completed buildings, hazardous ice and snow formations to occur Authors buildings. combined with reviews of incident and cold in diff erent manners and amounts. Michael Carter, Director/Consultant Background standards have shown a trend towards room test reports. The cases reveal interesting Roman Stangl, Director/Project Manager increasing the performance of roof, wall, and In the simplest of explanations, the currently data that initially seemed counter intuitive, Northern Microclimate Inc. (NMI) Troublesome ice and snow formations on glass assemblies, as evidenced by comparing achieved reductions in heat loss from many but can be explained when the individual Case Example 2 33 Water Street N. Tall, High Performance CTBUH Trustee P.O. Box 277 buildings are in no way a new phenomenon. ASHRAE Standard 90.1 between the 2004 and buildings’ interiors are promoting an increase design details are investigated. Building Type: Cambridge Building designers and owners have long 2010 versions (see Table 1). Further in potentially dangerous ice and snow Location: Midwest United States Ontario N1R 5T8 Canada struggled with the various aspects of winter exacerbating the issue of ice and snow formations. As insulation values, glass precipitation. This has led to the development formations on façades is the addition of technology, and building systems progress in Case Example 1 The second example (see Figure 2) also deals t: +1 226 444 0188 f: +1 226 444 0183 of standards and codes to address such topics various exterior elements intended to control the future to conserve energy, the Building Type: Tall, High Performance with the relationship between glass and 42 Talking Tall: Bjarke Ingels has e: [email protected]; as wind loads and snow loads during building solar gain, which ultimately serve as cold corresponding further reductions in heat loss Location: Northeastern United States frame. However in this case the focus is on ice [email protected] www.northernmicroclimate.com design. However, the aspect of falling, sliding collection surfaces. As a result, reports of through the façade will only increase the and snow formations that accumulate on or windblown ice and snow from a building is falling ice and snow incidents from high probability of hazardous ice and snow In this example (see Figure 1), observations of window sills or mullion caps at the base of

Michael Carter a topic that has not been widely performance buildings over the last ten years formation and release, creating signifi cant ice sheets were reported to form in the center vision panels. In this example, signifi cant ice Michael is a director and the lead technical consultant acknowledged, and consequently has have shown an increase in the frequency and challenges for building designers, owners and of vertical vision glass of a recently completed formations were consistently forming at the 04 CTBUH Latest BIG Plans for Tall Buildings of Northern Microclimate Inc., an architectural generated little in the way of standards, severity of hazardous ice and snow formation. operators, with further impacts to public building, and would subsequently release and edge of mullion caps and falling. Historically, consulting fi rm that focuses on the prediction, evaluation and mitigation of falling ice and snow. guidelines or prescriptive building code Although formal records of falling ice and safety. Consequently, investigation and fall to the busy street below. This report was sills or mullion caps of a relatively small He has contributed to publications with the National Institute of Building Sciences, Construction requirements to assist designers. In addressing snow incident reports do not yet exist, this research into the causes of these issues is taken with some skepticism as heat loss dimension were not prone to hazardous ice Specifi cations Canada and the International concerns, designers have largely relied on trend has been identifi ed through a record of needed and is ongoing. However, at this time characteristics of a traditional window and formations, as heat loss through the curtain Conference on Snow Engineering. Recognized as an expert in his fi eld, Michael works with architectural past experience or trial and error methods for media accounts and project experience. New empirical data and/or detailed case studies frame relationship call for the exterior skin wall system would create suffi cient melting to Antony Wood Bjark Ingels and engineering fi rms, focusing on his ability to reducing potential risks. The learning process reports in the last two years have detailed have not been developed due to the temperature of the center of the window to avoid signifi cant ice formations. However, visualize and interpret the characteristics of a building design within its local micro-climate. industry-wide has been slow or non-existent dozens of falling, sliding or windblown ice and reluctance of building owners and designers be the warmest location, since it is the due to the reluctant nature of various parties snow incidents in North America alone, to discuss their challenges openly. furthest from the infl uence of the frame that Roman Stangl to discuss errors or incidents, for fear of including such buildings as the Duke Energy would typically have the advantage of Roman is a director and the lead project manager litigation. Open discussion of the issues will Building in Charlotte and the New York Times The following case examples are based on insulation or a thermally broken profi le. of Northern Microclimate Inc. A CTBUH member CTBUH Executive Director with international experience, he has been actively accelerate the learning process around the Building in New York. interviews with building owners and However, in this particular case the large managing and consulting within the design and emerging problems created by advancing insulated glass panels off ered an improved High performance construction fi eld since 2005. Roman has contributed to publications with the National Institute of Building façade performance and tall building design. Many of the events investigated by the thermal performance over traditional glass Sciences, Construction Specifi cations Canada and the “façades have improved authors have not been found to be caused by and there was no spandrel panel, only a International Conference on Snow Engineering. 46 Design Research a single infl uencing factor, but rather by a list minimalistic metal frame. Thus, the glass internal thermal Modern Towers, New Issues of factors that tend to have a cumulative panels were the main resistive component of eff ect. True, there are situations where a single the assembly, promoting ice to form directly performance, but The façades of some recently completed high design feature, such as a window sill/mullion in the center (the coldest location) of vertical performance buildings are actively promoting confi guration or a solar shade device, has had vision glass panels. The key point to this increased the 05 Debating Tall: CTBUH International Student hazardous ice and snow formations under a signifi cant impact on the formation of example is the fact that the profi le of the typical winter conditions, rather than unusual, hazardous ice and snow. However, over the assembly is producing skin temperatures that conditions for forming severe or infrequent weather conditions. This course of numerous building investigations, align with exterior temperatures during more realization is unnerving, as modern high which includes multiple cold room laboratory typical winter precipitation events, thereby ice on metal and glass performance buildings often show only tests conducted in collaboration with the U.S. promoting an increase in frequency and skins… Tall Buildings: A Sustainable Design Competition 2012 modest or questionable reductions in energy Army Cold Regions Research and Engineering severity of icing over more traditional wall usage, at times falling short of their prediction Laboratory (CRREL), this is found to be the assemblies. To be clear, the relationship ” Figure 1. Example of snow and ice freezing on vision models. Furthermore, building codes and exception rather than the rule when it comes glass panel. © NMI between glass and frame is not the sole Future for Cities? 24 | Climate and Environment CTBUH Journal | 2012 Issue IV CTBUH Journal | 2012 Issue IV Climate and Environment | 25

06 Global News CTBUH Highlights from the CTBUH Research: Energy

th 30 renewable materials. The principle of the compared with thermal power generation. with a high air temperature are most suitable global news archive A Proposal to Create an Energy-Producing 48 9 World Congress Shanghai system was fi rst described by Isidoro The RMB 1.38 billion (US$208 million) project but radiation weakening components of the Cabanyes in 1903 and was revisited in the late calls for a full facility covering 277 hectares to atmosphere - such as clouds, aerosols and Megatall for Kunming, China 1970s by Michael Simon and Joerg Schlaich. produce a comparable output of 27.5 MW by water vapour need to be considered as well China’s fast-growing urban population and need for sustainable energy They successfully demonstrated the concept 2013. But only data from prolonged operation for the right location for a solar updraft tower. in 1982 in a small testing installation in will allow for a judgement on the perfor- Only by evaluating Meteotest/Meteonorm sources require alternative development ideas. The Krafthaus, which Report Manzanares, Spain. Combining the system mance of the power plant and its potential as satellite data, which includes the solar combines an energy-producing solar tower with an environmentally- with a tall building is, however, a new real estate property. So far only limited weakening components that reduce the W/ responsive, 215-story building, is one idea under consideration to address the approach. information on its existence and operation is m² heat gain on surface, an informed decision issues facing China’s cities. The building has installed power capacity about 30 available and still has to be verifi ed. for the most eff ective location be made. Very MW of electricity. With only a portion used by the building, the bulk of the In order to realize the potential of the important is also a high possible temperature Krafthaus linked with a tall building, it is diff erence between day and night to allow a Kevin Brass Thomas Kraubitz energy would be fed into the local grid. essential to fi rst study a commercial solar Finding the Ideal Location steady operation of the updraft tower that Author updraft tower in operation to gain technical can safe heat during the day in water packs Thomas Kraubitz, Senior Consultant The Concept lifts and infrastructure to be placed inside the and fi nancial input for the project. The solar A conventional solar updraft power station and releases it at night. Happold Ingenieurbüro GmbH (Buro Happold) concrete tube. On each fl oor there is a tower testing facility in Manzanares provided consumes several hundred hectares of land, if Pfalzburger Str. 43-44 Current energy provision systems in China are horizontal installment area for building valuable information; however it was limited it is designed to generate as much electricity In China, the Yunnan Province off ers many ele- 10717 Berlin Case Study Germany heavily based on exhaustible fuels such as services and technical equipment 150 meters by its height of only 195 meters and produced by modern power stations using ments necessary for the solar updraft tower 2 t: +49 30 860 906 3146 coal, hydrocarbons, and uranium. To fulfi ll long which allows an open space and a very maximum power output of 50 kW. The conventional technology, such as fossil fuels with up to 220–240 W/m of Annual Average f: +49 30 860 906 66 China’s commitment to reduce carbon fl exible fl oor plan.as well as easy access for research operation was too small to collect or nuclear energy. Until recently, most Global Radiation. The site of the chimney e: [email protected] www.burohappold.com dioxide emissions per unit of GDP by 40 to maintenance or replacement without taking data on commercial energy production. With discussions of Krafthaus have focused on hot plant in Jinshawan, Wuhai City, has a value of 52 CTBUH 2012 Awards Overview 50% by 2020, new systems to reduce the up valuable rentable space. a larger chimney height the pressure areas where large amounts of very low-value just 180–220 W/m2 and a much smaller infl uence on the environment must be diff erences increase the stack eff ect and a land is available, such as deserts. But the population (400,000 people), which means Thomas Kraubitz Thomas has been working in the fi eld of sustainable considered. Cities are turning to tall buildings The Krafthaus form of generating energy is higher power output is possible. limited number of consumers and high higher infrastructure costs due to the distance planning and design for over ten years and has to address the need for space in urban simple, reliable, accessible, and based on infrastructure and transport costs in those to consumers. developed a holistic view of buildings and the urban context. He has worked in diff erent climatic zones in settings, where little new land is available, but In 2010, a solar chimney plant started periods have made it economically 12 Absolute World Towers, consulting, project management, urban planning, Kevin Brass skyscrapers are typically big energy operation in Jinshawan, Wuhai City, Inner impractical. After overlaying solar radiation maps and the urban design and architecture for Stefan Behnisch, Ken Yeang, and Rem Koolhaas, amongst others. As consumers. They also tend to be ineffi cient, Mongolia, China. The 200-kilowatt power study of population maps (see Figure 2), the a Fulbright Scholar he was a Teaching and Research due to the space needed for vertical generating unit can supply 400,000 kWh of One of the most important aspects for City of Kunming, Yunnan Province, was Assistant at Harvard University from 2007–2009. Since 2012 he is also a studio critic at the Technical circulation. The higher the building, the more electricity per year, saving the equivalent of planning and running a solar power plant is identifi ed as an ideal site for this concept and Mississauga University Berlin. lifts and vertical infrastructure needed, limiting 100 tons of coal and 900 tons of water, global radiation. At fi rst it may seem that areas preliminary discussions have taken place on the amount of usable fl oor space. the concept with local planning authorities. Solar radiation already plays a large role in The Krafthaus can simultaneously address Kunming, with 60 to 70% of its warm water China’s need for more space and clean energy provided by solar-thermal energy. The 55 CTBUH on the Road (see Figure 1). The concept combines a population of Kunming prefecture stood at Bas Lagendijk, Anthony 6.4 million in 2010 and it is expected to grow A conventional solar 750-meter-tall solar updraft tower –some- times called a “solar chimney” or simply a “solar to become the largest metropolis of the “updraft power station tower” – and a climate responsive tall building. region. The strong economy of the Great consumes several At the heart of the Krafthaus is a solar thermal Kunming Area (GKA) largely depends on Pignetti & Sergio Vacilotto CTBUH events around the power plant utilizing a combination of a solar tourism and agriculture, with limited space air collector and the central updraft tube to Jinshawan, due to its hills and mountains. The city, often hundred hectares of generate a solar induced convective fl ow, Wuhai called “Spring City,” has also received attention land, if it is designed to which drives pressure staged turbines to for its proximity to the emerging business produce electricity. opportunities with Association of Southeast world generate as much Asian Nations (ASEAN) members, especially This solar facility is linked with a multi- Vietnam. The specifi c climatic conditions electricity produced by programmatic vertical tower reaching up 215 allow several harvests a year and its fl oors. The tower can off er gardens, shopping, picturesque setting makes it a national and modern power stations leisure, entertainment, and cultural facilities, in Kunming international tourist destination. At the same addition to offi ces and apartments – a time the most suitable areas for development using conventional complete vertical city. The 70-meter-wide are the prime farmlands on the lakeshore – technology… solar tube at the core of the Krafthaus allows off ering valuable views for new housing ” Figure 1. The Krafthaus, Kunming. © Thomas Kraubitz Figure 2. Kunming annual average global radiation overlay. © Schlaich Bergermann Solar Research 55 Diary 30 | Energy CTBUH Journal | 2012 Issue IV CTBUH Journal | 2012 Issue IV Energy | 31 Upcoming tall building events 18 A Different Approach to the Aerodynamic Performance 56 Reviews of Tall Buildings Review of new books in the 48 CTBUH Report: CTBUH 9th World Congress Shanghai World Congress Draws Global Industry David Menicovich; Jason CTBUH Library Leaders to Address Key Issues Skyscrapers We The CTBUH 9th World Congress closed to rave reviews, after three days of in-depth presentations, lively panel “purposely brought discussions and networking events. together a wide range Report by Kevin Brass, CTBUH Public Aff airs Manager of expertise and Vollen; Michael Amitay; Chris CTBUH 2012 Student Competition winner Alexis De Timothy Johnson issues research seed funding check Bosscher; Johannes de Jong, KONE; Chris Wilkinson, to winner Dr. Kristen Day, New York University with Li Wilkinson Eyre. © CTBUH Hongyu from sponsor AECOM. © CTBUH viewpoints, including

Attendees openly exchanged ideas and their Shanghai Tower’s aspirations go far beyond its the developers that are Letchford; Edward DeMauro; 57 Comments experiences, providing a unique opportunity height. The developers want to make it the leading the tall to go behind the scenes at many of the “most sustainable building in the world,” with world’s biggest and most innovative projects. green areas and a design that makes it a building boom in “We hope by sharing our experience and comfortable and effi cient part of Shanghai’s insight into the building system we would changing landscape. Asia. Ajith Rao & Anna Dyson Feedback on past journal make a contribution to sustainable supertall ” buildings in the world,” said Qing Wei Kong, Sustainability and the need to create effi cient Shanghai Tower Chairman, striking a chord and well-organized projects that integrate consistent themes. Speakers focused on the that would resonate throughout the event. and enhance the urban environment were complexities of developing large projects, from energy costs and project management to the political infl uence on iconic projects. issues Traditional dragon dance troupe performance at the opening ceremony. © CTBUH Richard Tomasetti of Thornton Tomasetti, Vincent Tseof Parsons Brinckerhoff ; Rafael Vinõly and Tony Long of CB Richard Ellis engaged in the panel discussion. © CTBUH Working Groups Shanghai provided an opportunity for the “We need to work together to fi nd a balance When Shanghai Vice Mayor Shen Jun took the The ballroom of the Grand Hyatt Jin Mao was Asia was the centerpiece of the event, which CTBUH’s array of working groups to gather Design for High Rises Buildings released by between iconic design and sustainability,” said 24 Increasing Problems of stage to offi cially open the CTBUH 9th World packed to capacity for the opening ceremo- was titled, “Asia Ascending: the Age of the and plot strategy for new and on-going the CTBUH Outrigger Working Group, and Mehdi Jalayerian, executive vice president of Congress, he quickly set the tone for the nies. The Congress sold out weeks before the Sustainable Skyscraper City,” but discussions projects. The sessions which took place the Natural Ventilation in High-Rise Offi ce Environmental Systems Design, during a issues that would dominate the next three opening, with 850 registered delegates from inevitably focused on issues aff ecting cities day before the congress – included a Buildings, a product of the CTBUH rousing panel discussion on the opportunities days of discussion and debate. “Land 43 countries in attendance, including many of and builders around the world. From the roundtable meeting of CTBUH leaders, Sustainability Working Group (see and barriers to sustainability. “They clash at resources are not renewable,” Mr. Jun said. “We the top developers, architects, engineers and outset, CTBUH Chairman Timothy Johnson, a which attracted more than 30 active advertorial on page 51.) The other working some point.” Falling Ice and Snow on 58 Meet the CTBUH have no choice but to build high rises to save building owners from China and around the design partner at NBBJ, challenged the representatives from around the world. The groups – Building Information Modeling; land effi ciently.” Tall buildings, he emphasized, world. “We purposely brought together a audience. “Let’s fi nd new ways to make rousing discourse primarily focused on the Fire & Life Safety; Research, Academic & Delegates shared information and designs for must serve as solutions to China’s long- wide range of expertise and viewpoints, buildings more sustainable,” he said. “Let’s be fl edgling city representative program and Postgraduate; Seismic Design and Wind the latest projects, as well as the challenges standing urban issues of pollution and including the developers that are leading the innovative. Let’s fi nd ways to change the way the best ways to grow the Council’s Engineering – focused discussions on projects are facing around the world. Over over-crowding. “It is an urgent and critical task tall building boom in Asia,” said CTBUH we think of tall buildings.” initiatives on a grass roots level. developing research projects and the best and over again, speakers emphasized that tall Modern Tall Buildings to meet these challenges.” Executive Director Antony Wood. ways to share the latest information in their buildings are still a young typology and the Javier Quintana de Uña Two of the working groups touted the respective fi elds. industry is still wrestling with the issues of release of new technical guides – Outrigger creating effi cient projects that address the needs of fast-growing cities. Michael Carter & Roman “This is a huge challenge for us. It is still not a mature business model in China,” said Zhaohui Jia, general manager of the Greenland Group, one of the largest developers of tall buildings in China. “We are still trying to explore this Stangl 59 CTBUH Organizational business model.”

Tall buildings still play a unique role in cities, a point brought home by the plenary session featuring the owners/developers behind the (Left to right) Qing Wei Kong, Shanghai Tower; Timothy Johnson, CTBUH Chairman; Attendees of the sold out Congress listen to the Day 2 plenary session presentations. past, present and future world’s tallest Structure & Member Listings Shen Jun, Shanghai Vice Mayor; Antony Wood, CTBUH Executive Director; Guo Qing Li, © CTBUH Attendees of the Global Leaders workshop. © CTBUH Tongji University. © CTBUH building. 30 A Proposal to Create an 48 | CTBUH 9th World Congress Shanghai CTBUH Journal | 2012 Issue IV CTBUH Journal | 2012 Issue IV CTBUH 9th World Congress Shanghai | 49 Energy-Producing Megatall for Kunming, China Thomas Kraubitz The challenges associated with the inherent 36 Assessing Potential “inconsistency of air flow may open a new way of Development in South Korea’s Supertall Building thinking about tall buildings as highly adaptive, Technology Payam Bahrami, David Scott, dynamic systems capable of responding to the Eun-Ho Oh & Young-Ho Lee opportunities and challenges associated with spatially and temporally fluctuating resources.

Menicovich et” al., page 18.

CTBUH Journal | 2012 Issue IV Inside | 3 Research: Energy A Proposal to Create an Energy-Producing Megatall for Kunming, China China’s fast-growing urban population and need for sustainable energy sources require alternative development ideas. The Krafthaus, which combines an energy-producing solar tower with an environmentally- responsive, 215-story building, is one idea under consideration to address the issues facing China’s cities. The building has installed power capacity about 30 MW of electricity. With only a portion used by the building, the bulk of the Thomas Kraubitz energy would be fed into the local grid.

Author

Thomas Kraubitz, Senior Consultant The Concept lifts and infrastructure to be placed inside the Happold Ingenieurbüro GmbH (Buro Happold) concrete tube. On each floor there is a Pfalzburger Str. 43-44 Current energy provision systems in China are horizontal installment area for building 10717 Berlin Germany heavily based on exhaustible fuels such as services and technical equipment 150 meters t: +49 30 860 906 3146 coal, hydrocarbons and uranium. To fulfill long which allows an open space and a very f: +49 30 860 906 66 China’s commitment to reduce carbon flexible floor plan as well as easy access for e: [email protected] www.burohappold.com dioxide emissions per unit of GDP by 40 to maintenance or replacement without taking 50% by 2020, new systems to reduce the up valuable rentable space.

Thomas Kraubitz influence on the environment must be Thomas has been working in the field of sustainable considered. Cities are turning to tall buildings The Krafthaus form of generating energy is planning and design for over ten years and has developed a holistic view of buildings and the urban to address the need for space in urban simple, reliable, accessible, and based on context. He has worked in different climatic zones in settings, where little new land is available, but consulting, project management, urban planning, urban design and architecture for Stefan Behnisch, skyscrapers are typically big energy Ken Yeang and Rem Koolhaas, among others. As a consumers. They also tend to be inefficient, Fulbright Scholar he was a Teaching and Research Assistant at Harvard University from 2007–2009. due to the space needed for vertical Since 2012 he is also a studio critic at the Technical circulation. The higher the building, the more University Berlin. lifts and vertical infrastructure needed, limiting the amount of usable floor space.

The Krafthaus can simultaneously address China’s need for more space and clean energy (see Figure 1). The concept combines a A conventional solar 750-meter-tall solar updraft tower –some- times called a “solar chimney” or simply a “solar “updraft power station tower” – and a climate responsive tall building. At the heart of the Krafthaus is a solar thermal consumes several power plant utilizing a combination of a solar air collector and the central updraft tube to hundred hectares of generate a solar induced convective flow, land, if it is designed to which drives pressure staged turbines to produce electricity. generate as much This solar facility is linked with a multi- electricity produced by programmatic vertical tower reaching up 215 floors. The tower can offer gardens, shopping, modern power stations leisure, entertainment and cultural facilities, in addition to offices and apartments – a using conventional complete vertical city. The 70-meter-wide technology… solar tube at the core of the Krafthaus allows ” Figure 1. The Krafthaus, Kunming. © Thomas Kraubitz 30 | Energy CTBUH Journal | 2012 Issue IV renewable materials. The principle of the compared with thermal power generation. areas with a high air temperature are most system was first described by Isidoro The RMB 1.38 billion (US$208 million) project suitable but radiation weakening Cabanyes in 1903 and was revisited in the late calls for a full facility covering 277 hectares to components of the atmosphere – such as 1970s by Michael Simon and Joerg Schlaich. produce a comparable output of 27.5 MW by clouds, aerosols and water vapor need to be They successfully demonstrated the concept 2013. But only data from prolonged operation considered as well for the right location for a in 1982 in a small testing installation in will allow for a judgement on the perfor- solar updraft tower. Only by evaluating Manzanares, Spain. Combining the system mance of the power plant and its potential as Meteotest/Meteonorm satellite data, which with a tall building is, however, a new real estate property. So far only limited includes the solar weakening components approach. information on its existence and operation is that reduce the W/m² heat gain on surface, an available and still has to be verified. informed decision for the most effective In order to realize the potential of the location be made. Very important is also a Krafthaus linked with a tall building, it is high possible temperature difference essential to first study a commercial solar Finding the Ideal Location between day and night to allow a steady updraft tower in operation to gain technical operation of the updraft tower that can safe and financial input for the project. The solar A conventional solar updraft power station heat during the day in water packs and tower testing facility in Manzanares provided consumes several hundred hectares of land, if releases it at night. valuable information; however it was limited it is designed to generate as much electricity by its height of only 195 meters and produced by modern power stations using In China, the Yunnan Province offers many ele- maximum power output of 50 kW. The conventional technology, such as fossil fuels ments necessary for the solar updraft tower research operation was too small to collect or nuclear energy. Until recently, most with up to 220–240 W/m2 of Annual Average data on commercial energy production. With discussions of Krafthaus have focused on hot Global Radiation. The site of the chimney a larger chimney height the pressure areas where large amounts of very low-value plant in Jinshawan, Wuhai City, has a value of differences increase the stack effect and a land is available, such as deserts. But the just 180–220 W/m2 and a much smaller higher power output is possible. limited number of consumers and high population (400,000 people), which means infrastructure and transport costs in those higher infrastructure costs due to the distance In 2010, a solar chimney plant started periods have made it economically to consumers. operation in Jinshawan, Wuhai City, Inner impractical. Mongolia, China. The 200-kilowatt power After overlaying solar radiation maps and the generating unit can supply 400,000 kWh of One of the most important aspects for study of population maps (see Figure 2), the electricity per year, saving the equivalent of planning and running a solar power plant is City of Kunming, Yunnan Province, was 100 tons of coal and 900 tons of water, global radiation. At first it may seem that identified as an ideal site for this concept and preliminary discussions have taken place on the concept with local planning authorities. Solar radiation already plays a large role in Kunming, with 60 to 70% of its warm water provided by solar-thermal energy. The population of Kunming prefecture stood at 6.4 million in 2010 and it is expected to grow to become the largest metropolis of the region. The strong economy of the Great Kunming Area (GKA) largely depends on

Jinshawan, tourism and agriculture, with limited space Wuhai due to its hills and mountains. The city, often called “Spring City,” has also received attention for its proximity to the emerging business opportunities with Association of Southeast Asian Nations (ASEAN) members, especially Vietnam. The specific climatic conditions allow several harvests a year and its Kunming picturesque setting makes it a national and international tourist destination. At the same time the most suitable areas for development are the prime farmlands on the lakeshore –

Figure 2. Kunming annual average global radiation overlay. © Schlaich Bergermann Solar offering valuable views for new housing

CTBUH Journal | 2012 Issue IV Energy | 31 developments and an easy way to dispose in order to achieve electricity costs that can rises from about 20 to 60°C closer to the wastewater. compete with other power plants. Covering middle. Higher temperatures at the center such an area with floatglass is far too make it possible to plant exotic fruits and A key element of the solar updraft tower, the expensive and the disadvantages of transport, vegetables and to increase the pallet of locally collector, is already available in greenhouse maintenance and superstructure made ETFE available agriculture products. The target site structures widely used in the Kunming area. foil a much better choice, especially since southeast of Kunming is already heavily The collector is covered by ETFE foil which is much of the area already is covered by thin farmed and the additional greenhouse space produced within the mainland, allowing for a foil for the current greenhouses. will increase productivity from the area. Black simple superstructure and easy maintenance. water tube bladders are placed where the In order for the system to work, the collector Underneath the foil roof warm air can rise to temperature is highest, allowing them to be would need a minimum diameter of 2,900 the tower and its turbine to generate warmed during daylight hours and returning meters, which would create the world’s largest electricity. To allow the required warm air flow, the heat at night to the structure to enable a greenhouse (see Figure 3). The size is needed the temperature under the greenhouse slowly 24-hour operation.

Figure 3. The Krafthaus – solar radiation principle. © Thomas Kraubitz Figure 4. The Krafthaus – services distribution. © Thomas Kraubitz

32 | Energy CTBUH Journal | 2012 Issue IV H The tower wrapped “around the solar chimney leads to a novel definition of a vertical building . The occupiable building is placed like rings around the chimney, allowing a very high level of sunlight and views.”

specifying the correct equipment and synergetic advances to reduce the overall demand of the building. They include an intelligent use of solar gain control through orientation as well as external shading H elements in the summer and the use of free heating in the winter. Level 40 ------The building will be connected to the main +136,50Figure 5. Krafthaus m typical floor plan. © Thomas Kraubitz utility networks of Kunming and feed electricity produced by the Krafthaus into the A New Form of Vertical Building elements can be installed on top of the grid. The operation would function as a green concrete walls of the chimney and power provider that allows the city to reduce

To make high-rise buildings sustainable, maintained and updated whenever needed. its CO2 emissions further and to subsequently

adaptations from other fields need to be The value is tremendous since each floor has meet China’s commitment to reduce CO2 made. Tall structures typically become more the 150-meter long services and technical emissions by 40 to 50% by 2020. inefficient as they go higher because of the equipment area for any kind of installation. huge amount of space required for circulation This approach brings great freedom in design, The key component of the concept is the to move from the ground floors to reach the much larger rentable space and endless concrete tube that needs to reach up to 750 top. possibilities for future modifications, which is meters to produce the required suction effect necessary for the building to be sustainable for the power plant to operate. While a The tower wrapped around the solar chimney over the long term. number of materials have been considered for leads to a novel definition of a vertical the superstructure of the Krafthaus, concrete building (see Figure 4). The occupiable The rational use of energy in the Krafthaus is has been found to be ideal since it is a building is placed like rings around the essential for both environmental and relatively low-tech approach that could utilize chimney, allowing a very high level of sunlight economic reasons, and forms a key part of the local resources and labor for construction and and views. This also allows diverse layouts for concept. The project seeks to reduce energy maintenance. Concrete also allows the wall each floor. With this new typology of building, demand through passive measures, efficient thickness to adjust from 1.8 meters at the the biggest part of the circulation is put inside systems, and the use of renewable energy. base to 0.3 meters at the top. The floors (12 the solar chimney, including the lifts and Demand reduction is achieved through meters in depth) are placed like rings around infrastructure (see Figure 5). All the support passive measures and detailing, and the tube and provide additional stability and

CTBUH Journal | 2012 Issue IV Energy | 33 highest internal comfort. When the external temperatures are uncomfortable and energy The Krafthaus requires a large initial capital losses using natural ventilation are high, the mechanical ventilation is used to provide a “outlay, but would have relatively low operating comfortable internal environment sealed from the external environment. Whenever external costs. The initial capital required is roughly the temperatures and humidity levels permit, ventilation openings in the façade allow for same as next-generation nuclear plants. natural ventilation, connecting the user with ” the external environment. Ventilation will be controlled through detectors to allow set back ventilation rates, controlled by variable ample natural daylight for the building. decentralized distribution strategy while motorized dampers to reduce unnecessary Included are bubble decks or honey comb achieving high efficiency and reducing ventilation of unoccupied spaces. floor systems that also reduce the load of the maintenance in the plant area. The cooling floor slabs. In addition, simple water tubes in strategy uses a combination of air- and The installation of the centralized BMS system the walls or slabs allow for heating (ca. water-based systems to maximize efficiency allows the overall management and operation 50–55°C) in the winter. The water will be and occupant comfort. Free cooling will be of the Krafthaus to be tracked, controlled and warmed by the warm updraft in the chimney, achieved by using the groundwater as a heat monitored. The BMS system gives centralized which will provide a free heating system. Life sink through the use of a closed loop heat control to functions related to lighting, Cycle Costing (LCC) and Life Cycle Assessment exchanger. The feasibility of this solution will ventilation, heating, cooling and facility (LCA) has been considered with the cement depend on the ground water conditions on management. Active load management uses for the tube having a net energy payback of the site and the local regulations on the use of a coordinator within the BMS system to log three to four years. ground water. It will, however, not be possible the required actions and ensure that to meet the full cooling demands of the simultaneous loading of the electrical system project using only ground water as a means does not occur. Metering and sub-metering Energy Efficiency of heat rejection. Thermal wheel heat allows a full audit and control of the users to exchangers combined with desiccant wheels be conducted. Only through measurement The façade is double glazed, allows ample will be used to create a highly efficient can the energy users and improvements be levels of air tightness and incorporates method to pre-cool and dehumidify fresh found. The logging of energy use from the external shading. All three of these features incoming air. Enough fresh air will be drawn in BMS provides a valuable resource to enable reduce the energy consumption of the to meet the ventilation requirements of the strategies for energy use reduction and building by lowering its cooling demand. The space; the recirculated air will be passed identification of high users and potential plant double glazing insulates the building from the through a standard AHU. This will minimize problems. heat of the outside air, while good air the energy required for cooling and tightness prevents infiltration of hot humid air dehumidification. Photo-voltaic panels on the southern façade from the outside. The shading is intended to (approximately 15,000 square meters) are in reduce the solar gains of the building. In order A mixed mode ventilation strategy utilizing line with the projects’ commitment to green to ascertain the effectiveness of the external both natural and mechanical ventilation energy and also generate electricity for the shading the building was also simulated in modes is proposed to optimize the building’s building. Several generators will be installed the IES Virtual Environment. Air tight performance by reacting to the external to provide power to sprinkler pumps, lifts and construction and intelligently-designed surroundings. The offices will use a VAV lighting operations, as well as essential power shading further limits the cooling energy (variable air volume) system. This has the requirements, in case of an emergency. A UPS demand and allows for maximum levels of advantage of providing optimal internal air System is required for the protection of daylight while minimizing heat gains through quality and is very quiet, while allowing for services such as telecommunications and the façades. Solar gain through the windows flexibility and personal temperature control server rooms. could potentially be reduced through the use within individual zones. In the hotel section a of reflective coatings or films. This is combined VRF (variable refrigerant flow) system is with the use of high efficiency lighting and proposed. The plant strategy will be modular Water Management office equipment that reduces the electricity to allow maximum efficiency, matched to the demand of the building. demand. An intelligent building management Sustainable water resource management is system will control when it is energetically also a key issue for the Krafthaus. Water is an A central energy center for the Krafthaus beneficial to utilize the mechanical ventilation important resource in Kunming and plays a provides chilled water to all areas, enabling a mode, offering the highest efficiency and the major role in both the aesthetics of the area

34 | Energy CTBUH Journal | 2012 Issue IV and the well-being of the users. The ethos of a non-potable demands. This approach ensures least 100 years. The concept is expected to sustainable water strategy should reflect the that the most efficient and cost effective have less of a requirement for standby natural environment, where conservation of approaches are pursued first and that the capacity from traditional energy sources than resources depends on highly integrated right water is used for the right purpose. wind power, since thermal storage systems. The water hierarchy thus aims to mechanisms – the water bladders in the reduce the demand for potable water A number of passive measures can be center – are incorporated to smooth out through the use of efficient fixtures and employed to reduce water demand (see power yields over the day/night cycle. fittings and ensuring that the distribution Figure 6). These require no behavior change design is efficient before considering the use by the user, and tend to be very cost effective, Until reliable electricity cost figures are of alternative sources for lower grade or using such elements as fixtures and fittings. A available for a time period on a utility-scale good practice water distribution system power plant size, predictions on the levelized design, while less visible to users, can also electricity cost (LEC) are in the range of 11 reduce water use. The domestic hot water Euro cents (Sclaich et al. 2005) but have to be (DHW) will be pre-heated using the waste verified by a facility in operation, such as the heat from the chimney (50°C) before being Jinshawan tower. The solar updraft tower can’t heated to the required temperature, using currently compete with the LEC of approxi- high efficiency gas-fired calorifiers. One goal is mately 5 Euro cents per kWh for a wind or to reduce the overall demand and pressure natural gas plant of comparable size (30 MW), on the potable water connection. A rainwater creating a high risk for the developer building harvesting system is planned to collect a combination of a supertall skyscraper and rainwater for irrigation. This has the added power plant. But the income from running an benefit of reducing rain water runoff into the observation deck and selling off units in Asia’s local sewer. In addition, water tanks between tallest building has to be considered and the 181st and 188th Floors help to stabilize the could lower the LEC and reduce the invest- building during natural disasters (the Motion ment payback time of the Krafthaus. Control System) while also functioning as a water tower. Conclusion All wastewater from the Krafthaus is recycled on site and the solid waste is used as fertilizer China’s need for sustainable green energy is used in agriculture production. The water is sources combined with its history of treated through natural organisms in the agriculture and interest in developing tall roots of the plants, providing an energy- buildings make it an ideal setting for the efficient means of grey water treatment, Krafthaus. Given the right environment, a which will turn the effluent water back to 750-meter solar tower can help generate 30 drinking water and the sludge will be used as MW of energy for the local community, as well fertilizer on site. as creating a self-sustaining vertical city with residential, office, retail and recreational space. More study is needed, but the concept offers Economic Considerations a variety of benefits for China’s growing urban areas.  The Krafthaus requires a large initial capital outlay, but would have relatively low operating costs. The initial capital required is References roughly the same as next-generation nuclear Gov.cn. “China’s First Solar Chimney Plant Starts Operating plants. Like other renewable power sources in Desert.” Accessed June 1, 2012. http://www.gov.cn/ english/2010-12/28/content_1773883.htm. there would be no cost for fuel, and due to the location and its continuous use for Solar-chimney.biz. “NEW about solar chimney power plants.” agriculture there would be no costs for the Accessed June 1, 2012. http://www.solar-chimney.biz/new. php?PHPSESSID=160852743538f135a1ef6e9c58c983a4. land. The less than 5,000-square meter site for the tower would be rented for a period of 99 SCHLAICH, J., BERGERMANN, R., SCHIEL, W. & WEINREBE, G. years. The costs per kWh of energy are largely 2005. “Design of Commercial Solar Updraft Tower Systems – Utilization of Solar Induced Convective Flows for Power determined by interest rates and years of Figure 6. The Krafthaus – water distribution. © Thomas Generation.” Journal of Solar Energy Engineering 127 (1): Kraubitz operation, which should be considered for at 117–124.

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