Net-0 Skyscraper Energy Calculator – A Case Study

Publication

(Shameless?) Self Promotion

Well folks, the big one has arrived: our first major publication (in a world-famous research journal, no less!), discussing what it may require to take a contemporary skyscraper off the grid!  This article expands on several issues debated at length elsewhere in this blog, including technological incorporation, location, and expanded functionality.  Additional details can be found at https://store.ctbuh.org/PDF_Previews/Journal/CTBUHJournal_2016-3.pdf, as part of the CTBUH's 'preview section'.

Yet while the link above and corresponding cover pictures provide a good idea of what was published in hard format, several additional pictures, captions, and diagrams within the article had to necessarily be withheld from the final document, based on editorial oversight. While it has been wonderful to see some of these sustainability items relate to other discussion in this same issue, our work is far from complete! For these and other reasons (and with permission of the CTBUH), we at HeightsRising have provided the full submitted document below for your viewing pleasure, and in the following PDF 'temporary download', attached: https://drive.google.com/file/d/0B95sg8QrLB0vYngxbHpFblJfcjA/view     

Overall, a considerable amount of commitments remain, if society seeks to use passive techniques by which to lower our energy use/carbon footprint: with luck, this article will be one of a series of steps, in a progressive direction!

See the full paper below:

The Full Paper:

Abstract

This paper seeks to add to the growing body of literature on Net-0 skyscraper energy use, documenting on-site resource calculation potentials as related to integrated building collector sizing.  It suggests structures that can use their size, bulk, and physical location by which to offset total energy use, forgoing any number of current or complicated baseline standards used in non-sustainable practices.  Such design features would better define Net-0 aspirations up front, underlining alternative strategies that can also be pursued from the very design outset.  Overall, this methodology suggests utilizing a wealth of data available from contemporary ASHRAE sources and on-site measurements, to showcase how many people a potential site could house as compared to expected on-site energy gains.     

INTRODUCTION:

As skyscrapers soar ever higher and explore greater depths of design efficiency, many new structures have begun to experiment with an initialized, more computational approach towards overall energy use.  This recent shift has attempted to transcend the traditional limits incurred by the typology thus far, utilizing opportunities from growing heights or existing site opportunities, to better incorporate next-generation design ideals.  Everything from formal arrangements, to occupant user groups, to internal layouts is now being considered by which to rework built structures as a sustainable whole.  When balanced against a variety of harvestable on-site resources, new figures are seeking to exceed current reductionist pursuits: to create a true Net-0 skyscraper from the initial design outset.

The emergence of such comprehensive planning initiatives follows several design approaches that have been growing in prominence over the last few years.  Major research oriented architecture firms like Perkins & Will and BNIM have begun to publish procedural steps by which to initiate Net-0 buildings in the United States, while theorists abroad continue to push the envelope towards fully integrated, self-sufficient buildings.  Such methods first encourage a minimizing of user point loads upon a building, then seek to offset remaining energy use through an array of various on-site or technological sources.  Structures like the Pearl River Tower (Guangzhou) and the Bank of America Tower (New York) have shown that substantial energy offsets are possible in today’s marketplace through such practices, while Chambers, et al. (2014) has theorized a point-by-point analysis on how to conceivably reduce current high-rise energy use by up to 90%.  Other structures have gone a step further, using tactile biological capture through Living Machines® to offset a greater range of human needs.

But while many such theories have often focused upon reductionist strategies to mediate overall energy use, practitioners in Europe are beginning to broach high-rise sustainability from an initialized, more computational perspective.  A system of “PlusEnergy” has recently taken root with German designers and theorists, seeking to create buildings that produce more energy than they need to operate, directly from design outset.  Such structures first map out energy requirements for a target structure or user group, then implement a variety of design systems to capture enough wind, solar, or geothermal resources by which to counterbalance user needs.  Case studies like Adolf Disch’s Heliotrope, or the solar settlement of Vauban, in Freiburg, Germany have shown that PlusEnergy is now achievable in shorter structures, even within harsh northern climates (Scheurer 2001).  While such facilities have yet to apply a complete biological capture approach or even expanded beyond mid-rise heights, they have the added benefit of being easy to calculate and evaluate over time. 

Meanwhile, additional possibilities have arisen from the integration of technological and cloud-based design sources at earlier intervals.  Companies like Google have begun cataloging available solar resources at sites all across the world using a variety of historical data and resources from the National Climactic Data Center (Quintal 2015), while plug-ins for BIM design software have begun to showcase the ecological benefits of various design decision iterations (Le 2014).  This has led to structures like the Bullitt Center (Seattle, WA), which can harvest tactile site information throughout initial design stages, and later display the full range of their collection data in real time, through personal download applications (Pena 2014). 

Figure 1: Overview of 'energy-positive' skyscraper approach

For skyscrapers – a building type that uses considerably more energy than low-rise counterparts – the integration of these methodologies can have enormous design connotations.  Incredible quantities of resource data can now be integrated into final designs at an early point, creating better prediction possibilites, or of measuring initial harvest potentials from almost any site. Towers have now been suggested that could incur offsets through a heightened ‘economies of scale’, exceeding the original conditions of a site several times over, such as by providing external vegetation on multiple floor levels, or by using their size or bulk for additional user benefit or resource collection (Krier 2011). Such strategies can range between redirecting excess roof rainwater to flush surrounding buildings, nestling extensive solar panel groupings within exterior facades by which to facilitate greater energy production, or else applying intensive use of vegetation inside central courtyards, increasing natural biofiltration (Yeang 2003).  What emerges is a layout like that seen in Figure 1, where a singular tower could potentially link to, or even support, several smaller structures around it. In this manner, theorists have sought to justify new developments with factors other than profit, seeking to capture and utilize the growing opportunities offered by tall buildings, to more fully offset their enormous consumption rates.  These and other questions led to the following assessment, showcasing the following results:   

Figure 2: Energy neutral 'balance' approach/methodology

INITIAL CALCULATIONS: ALTERNATIVE METHODS BY WHICH TO ACHIEVE NET-0

This research suggests an agenda similar to the aforementioned PlusEnergy tactics, while superseding several reductionist strategies that have traditionally defined skyscraper energy efficiency.  This five step procedure could provide parameters for a computational program for designing net-zero skyscrapers, and contrasts those factors against on-site resources (see figure 3). 

1.       Select a site, and identify desired building size/general program parameters

2.       Document all on-site resource potentials that are available for capture and energy offsets

3.       Determine internal occupant types and occupant energy users that will inhabit a building over the course of its lifetime

4.       Balance these users against available on-site resources

5.       Exceed all energy minimums

These strategies can be thought of as a comprehensive energy use ‘calculator’, with several uses beyond low or mid-rise building applications.  It would continue the aforementioned PlusEnergy strategies, balancing on-site resources against rentable building space of our tallest building types.  From there, additional energy or municipal criteria can be added to better correspond to each selected site, expanding upon local initiatives or applicable site precedents as needed. 

First Step: Site Selection and Target Building Size

To initiate this Net-0 skyscraper calculation methodology, several steps must be taken, to balance energy figures of tall buildings below zero energy use. The first step of this procedure would be to identify a prospective site, and contrast it against a general building program.  From this initial analysis, lessons could be shifted and scaled to other locales.  

As all PlusEnergy strategies are highly reliant on site, the City of Chicago was tentatively selected as an initial test locale, for a variety of Plus-Energy reasons.  The area is one region rich in available capital, investment opportunities, transportation, natural resources, and commitments to green design (Hendershot 2011).  It also remains a dense, growing metropolis (Holtz 2012), with a long history of clients willing to invest and experiment with passive energy buildings (Rosenfield 2015).  Most importantly, the city is one of the ‘wettest and windiest’ big cities in the United States (cities over 750,000), containing major harvest potentials from wind and rain resources (Why 2010).

Additionally: For the purpose of this paper, a 100’x100’x600’ test structure was also initially considered along the main fork of the downtown Chicago River branch.  This suggested size aligns with ‘standard skyscraper’ dimensions currently employed in the current downtown building assemblage (CTBUH 2015), at a location which would also expand upon a number of ongoing infill proposals itself (Chicago Department of Planning and Development 2015).  From here, additional criteria and calculations were added, after initial design considerations were generally tested.  

Figure 3: Chicago Test Site Location (Courtesy of SOM)

Second Step: On-Site Potentials

The next step in this suggested Net-0 Skyscraper calculation process, is to document available on-site resources.  Like most North American cities, Chicago maintains an extensive listing of its weather phenomenon and other resource data through the National Climate Data Center.  From these and other similar sources, a catalogue for the riverside location was created, utilizing engineering calculations acquired through both the American Society of Heating, Refrigeration & Air Engineers (ASHRAE) and the refrenced texts (Grondzik * Kwok 2014).  An chart of each possible potential at this site was then mapped and compared, with the results shown below in Figure 5.  Additional measurements were taken from online databases and physical field measurements on site, combined with a conventional site analysis or applicable solar studies.  

Figure 4: Resource Potentials from Chicago River Site (mWh generation, per unit height)

Though these numbers represent a rough approximation of energy that could actually be captured in a real world environment, it serves to highlight that two sources in particular, Wind & Stormwater Hydro, appear to offer the greatest on-site potentials at this location. 

In addition to these items: the initial documentation phase also demonstrated surprising low figures from several common sustainable sources - such as Solar and Geothermal - underlining the fact that a majority of these capture systems are highly site specific, and fairly erratic.  The downtown local also demonstrated lowered resource capture, which was likely due in part to the proximity of nearby building structures reducing initial harvest potential, or from additional difficulties need to construct any subterranean elements beneath the existing CTA rail lines.  It was also discovered that taller buildings to the south and west of the test site could eliminate collection potentials of solar and wind power, until the example structure rose above a 50-100’ threshold. 

Third Step – Occupant Type

The third step of the Net-0 Skyscraper calculation methodology is to explore and document an expected range of occupant types: daily users that would need to be balanced by the available on-site resources.  As the internal resource needs of various tenant groups have been accurately quantified and measured over the last fifty years (Oldfield, et. al. 2008), these figures can be compared or contrasted with various occupant types that could potentially inhabit the building.  For the Chicago site, a determination was made to explore and expand upon normally expected occupant groupings and modern energy consumption rates, with a moderate anticipation of future user needs to be explored on an ad hoc basis. 

Yet several additional factors need to be considered and balanced for this approach to be applicable towards a full range of possible users.  Unsurprisingly, the interaction between residents, office workers, cleaning crews and innumerable other facility caretakers were discovered to have considerable impact upon overall building energy use.  Hotel patrons, high-rise residents, or general hospitality have traditionally accounted for 30% more energy use than their clerical or low-rise counterparts (Office of Air and Radiation 2008, Brabar 2013).  Meanwhile, tenants inhabiting the upper heights of a tall or super-tall structure were found to require substantially more energy by which to supply any number of basic services - everything from water, to vertical transportation access to and from residences (Government Accountability Office 2008).  Even tourists, a traditional mainstay of Chicago super-tall high-rises, were found to use double or even triple the energy of all other users groups over a similar time frame (Brown 2015, Rastogi 2009). 

As this dynamic offers a considerable range of possibilities upon a possible test structure, an ‘average user’ was suggested by which to initiate this test research – one specifically catering towards low-impact users.  This ‘typical user’ is documented below in Figure 5, as a standard clerical office worker inhabiting a genearl building, for only an eight hour portion of the day.  Other daily user groups, such as hospitality, food service, and tourists would be considered for the subject building only after initial calculations were tested and compared with other nearby structures. 

Figure 5: Office occupant ratio programming & spatial requirements, for full Net-0 balance

[2.4] Fourth Step: Energy-Space Relationships, Trials, Energy Balance, and The Empty Tower

The last phase of this calculation methodology is one of balance and exploration: comparing how many users a site could potentially house, based upon any number of resources available on-site.  From there, experimentations in building proportions, collector sizes, or other design features could then be factored back into the initial model, with a greater focus or emphasis on methods that showed the greatest returns. 

For the Wind and Water harvest potentials at the Chicago site, the original Net-0 selection was found to be even more dynamic and layered than first predicted. Wind collection works best with large diameter turbines located at the peak of tall structures, while storm water energy generation requires substantial collection apparatus’ sizing, pipe diameters, and internal turbines by which to generate any excess power.  Further limits arose, after discovering that occupant-to-collection-sizing ratios were exponentially inverse, as only a limited quantity of occupants could be offset before the test building reached certain heights or collector sizes.  The initial analysis suggested a test building that would have to climb at least 300-500 feet before any potentials from wind power was even applicable at this selected site, and was found to require larger swaths of the building be left open for collection than previously assumed.  This would also assume for 100% capture ratios, and assume average efficiency loss from typical systems.

     

Figure 6: Chicago Energy Gain Potentials (at selected site)

In addition to these initial sources, harvest potentials also varied considerably depending on the time of day or year, and were not as consistent as current fossil-fuel sources.  Both Wind and Water collection was found to be highly infrequent, leading to serious questions of offsets during times of drought, or possibly selling energy back to the grid during periods of collection excess.  This suggested a building that was much larger, thinner and considerably more open than initially guessed, with greater space requirements dedicated towards direct resource capture, within thinner buildings.  For these and other reasons, several variations between design arrangements were initially contrasted and tested. 

Yet even with these accommodations, several startling figures emerged after a range of quantifiable data was applied to a succession of test structures.  Even by harvesting a combination of all available on-site potentials, not even a modest 150x150x110’ building of 1310 people could be supported through passive means.  A tower would have to soar to at least 600’ to offset this underwhelming quantity of occupants, and be comprised mostly of collection panels, or open space allocated for total resource capture.  These conditions occur even after limiting the structure to low-impact users on only the first few floors, and assuming for a 100% capture for all available resources, at all times of the day, throughout the entire year.  Such figures persisted, regardless of building shape or arrangement, or even by what energy calculation method was used.  While additional energy possibilities could exist by filling such empty spaces with urban farming or natural bio-filtration, such possibilities have serious questions of cost, impact or practicality (Green 2009).

Additionally, the riverfront site was discovered to be far from an ideal rainwater or solar collection test site.  While the heightened densities around the initial Chicago locale remained prime for other facets of sustainability, it reduced the availability of solar and wind collection until a structure rose above a quantifiable threshold of 50-100’.  Locations several blocks to the south or west of this downtown cluster offered slightly higher energy returns, as fewer buildings existed to interfere with overall collection potentials.  Rural and suburban Chicagoland offered even better possibilities, having substantially less obstructions than their urban counterparts.

Elsewhere around the world, even greater potentials were found to be possible through these same calculation methodologies.  Several southeastern Asian sites were found to average almost double the annual amount of rainfall or solar potentials as the initial Chicago test site, all while maintaining similar wind velocity patterns (see Figure 8 below).  Most of these locals were also found to contain higher populations and urban densities than in the United States, while having a strong market demand for next-generation resource management.  Energy use at these sites was also 20-50% less than the current level of American consumption patterns (Diamond 2015), suggesting that a greater quantity of occupants that could be offset by next-generation structures or design frameworks in these possible locations.  [

Yet even with drastically increased resource potentials at other sites, no cursory location was found to generate enough energy to fully offset any ‘standard sized’ 30.5x30.5x183 meter skyscraper.  From high energy environs like Dubai, to lower impact users in Shanghai, not even a scant 45% occupancy of similar test structures was found to be achievable through these same calculation processes.  It was discovered that the resources required to operate or inhabit contemporary skyscrapers far surpassed the ability of modern energy capture technology to match even a basic set of Net-0 design parameters.  What remains is a concept structure that is mostly empty, using a majority of its resource capture to power only a small portion of the buildings base.  

Figure 7: Net-0 Skyscraper Occupancy Variations, per 'Resource Region'

CONCLUSION

As the next generation of skyscrapers seeks a greater amount of self-sufficiency, a continued push for increased design analysis and integrated application remains tantamount.  This presented 'Net-0 skyscraper energy calculator’ offers one prospective on how to expand upon passive energy concepts into the near future, better magnifying efforts already utilized for shorter building types.  Though the figures presented in this research suggest additional design shifts may be necessary to offset higher heights, it also serves to highlight the possible challenges and opportunities that remain as the typology shifts towards complete net-neutrality.  Site, orientation, and occupant users types remain critical in the discussion of any PlusEnergy structures, as does the continued integration of technological and passive integration sources. While the increase of resource collection, energy code minimums, and technology displays is helping to reduce these figures, the tested Chicago site (as well as other locations around the globe) has shown that an incredible array of resources remains available by which to harvest.  While it may be too soon to completely remove the skyscraper from the current metropolitan grid, significant advances in technological energy capture can, and are, playing an increasing role in mitigating future energy use. 

The author also wishes to thank Lawrence Tech Thesis Advisers Ed Orlowski, Ralph Nelson, Margaret Wong (along with critics Martin Scwartz, Philip Plowright, and Danielle O’mara, and Yelena Suktoherina) for their feedback, discussions, and general dissections of these topics: without your kindness and gravitas, this paper would not be a reality.   

REFERENCES

Alter, L.  (2013)  LEED-bashing: Is the Bank of America Building really a 'toxic tower'?  Treehugger.  Accessed 2 Sept., 2015.  Web.

Belroit, J. (2010)  Vauban: a pioneering sustainable community in Germany.  Ellen MacArthur Foundation.  Accessed 15 Sept., 2015.  Web.

Bentley, C.  (2011)  When will Chicago get its next supertall skyscraper?  WBEZ91.5.  Accessed 28 Jan., 2015.  Web.

Brabar, H. (2013)  The Closest Look Yet at the Relative Energy Efficiency of Big Buildings.  The Atlantic.  Accessed 28 Aug., 2015.  Web.

Brown, E. (2015)  For Tourists, a 3.9 Billion View.  News Corp.  Accessed 27 Aug., 2015. Web.

Chicago Department of Planning and Development.  (1999)  Chicago River Corridor Development Plan.  City of Chicago.  Accessed 24 July, 2015.  Web.

Chicago Department of Planning and Development.  (2015)  Overview of the Green Permit Program.  City of Chicago.  Accessed 24 July, 2015.  Web.

Chicago Department of Planning and Development.  (2015)  Sustainability Section.  City of Chicago.  Accessed 24 July, 2015.  Web.

CTBUH. (2015)  The Skyscraper Center Council of Tall Buildings and Urban Habitat.  Accessed 25 July, 2015.  Web.

Diamond, R., et. al. (2015)  Sustainable Building in China-A Green Leap Forward.  Buildings - Open Journal..  Scholarly Journal.   Accessed 31 Oct., 2015. Web.

Dunlap, A.  (2011)  Sustainability Section.  Vox Media.  Accessed 22 Sept., 2015.  Web.

Environmental Policy Alliance.  (2014)  LEED Certification Fails to Increase Energy Efficiency.  PRNewswire.  Accessed 22 Sept., 2015.  Web.

Foster, N., et. al.  (2009)  Green Skyscrapers: What is being built and why?  Green Cities.  Accessed 12 Sept., 2015.  Web.

Government Accountability Office. (2008)  ENERGY-WATER NEXUS - Amount of Energy Needed to Supply, Use, and Treat Water Is Location Specific and Can Be Reduced by Certain Technologies and Approaches.  United States Government Accountability Office.  Print.

Green, H. (2009)  Let's Make This Clear: Vertical Farms Don't Make Sense.  Ecogeek.  Accessed 1 Mar., 2014. Web.

Hendershot, S.  (2011)  Chicago's clean-energy innovators aim to catch up with the coasts.  Crains.  Accessed 22 Sept., 2015.  Web.

Holtz, M.  (2012)  Downtown seeing residential boom; population up 36% in last decade.  Tribune Publishing Company.  Accessed 12 Sept., 2015.  Web.

Krier, L.  (2011)  Leon Krier: Architect, Urbanist, Theorist.  Detroit AIA.  Lecture.

Le, M.  (2014)  Autodesk® Green Building Studio for an Energy Efficient, Sustainable Building.  HAMK University of Applied Sciences.  Accessed 31 Sept., 2015.  Web.

Merrion, P.  (2013)  Chicago among world's top 10 business hot spots.  Crain Communication Inc.  Accessed 1 Sept., 2015.  Web.

Office of Air and Radiation. (2008)  EnergyStar® Building Upgrade Manual.  United States Environmental Protection Agency.  Accessed 30 July, 2015.  Web.

Oldfield, P., et. al. (2008)  Five Energy Generations of Tall Buildings: A Historical Analysis of Energy Consumption in High-Rise Building.  Change Over Time. Vol. 14. Issue 5: 110-128.  Scholarly Journal.   Accessed 20 Oct., 2011. Web.

Pena, R.  (2014)  Living Proof – The Bullitt Center.  University of Washington.  Accessed 27 Dec., 2015.  Web.

Population Division.  (2011)  Land Area, Population, and Density for Places and (in selected states) County Subdivisions: 2010  United States Census Bureau.  Accessed 2 Sept., 2015.  Web.

Prindle, D. (2015)  Google Project Sunroof shows how much solar juice is on your roof, no math needed.  Digital Trends.  Accessed 17 Sept., 2015.  Web.

Quintal, B.  (2015)  Launch of Google Sunroof Brings Valuable Solar Power Data to the Mainstream.  ArchDaily.  Accessed 1 Dec. 2015.  Web.

Rastogi, N. (2009)  When people take the elevator, does Earth get the shaft?  The Slate Group.  Accessed 25 Aug., 2015. Web.

Rosenfield, K.  (2015)  Studio Gang to Design Net Positive Energy Campus for Chicago Children's Academy.  Plataforma Networks Broadcasting.  Accessed 1 Sept., 2015.  Web.

Scheurer, J. (2001)  Urban Ecology, Innovations in Housing Policy and the Future of Cities: Towards Sustainability in Neighborhood Communities.  Perth: Murdoch University Institute of Sustainable Transport. Print.

Why, T.  (2010)  How do Chicago's winds compare with other major U.S. Cities?  Tribune Publishing Company.  Accessed 10 Sept., 2015.  Web.

Yeang, K. (2003) The Ecosraper: Premises for Tall Building Design.  Wiley Interscience.  Accessed 3 May 2015.  Web PDF. <http://www.PDFjgb.5.1.132?cookieSet=1>.  pg 20

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