Efficient Energy Production for High-Demand Tenants of Tall Buildings
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ctbuh.org/papers Title: Efficient Energy Production for High-demand Tenants of Tall Buildings Author: Alexander Durst, Chief Development Officer, The Durst Organization Subjects: Architectural/Design Building Case Study Property Ownership/Management Sustainability/Green/Energy Keywords: Energy Efficiency Renewable Energy Sustainability Publication Date: 2015 Original Publication: Global Interchanges: Resurgence of the Skyscraper City 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 Unpublished conference paper 5.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 Unpublished © Council on Tall Buildings and Urban Habitat / Alexander Durst Efficient Energy Production for High-demand Tenants of Tall Buildings Abstract Alexander Durst Chief Development Officer Tall Buildings in urban landscapes present a unique challenge in the field of sustainable The Durst Organization, building. These structures tend to attract a tenant base of dynamic industries such as financial New York City, USA services, communications, technology and digital media. Such workforces demand intensive energy usage, sometimes around the clock, and consequently the energy use intensity (EUI) of the buildings they inhabit is consistently higher than EUIs of commercial buildings with other Alexander Durst is Chief Development Officer and a fourth generation family member of The Durst Organization. tenants. The mandate of the sustainable builder of tall buildings is to deliver this energy as Alexander began his career at The Durst Organization in 2005 efficiently as possible. Large-scale natural gas-fueled cogeneration facilities are potentially the working in building operations. He moved on to managing a portfolio of small residential buildings and the management most efficient means of producing onsite energy, although the successful and safe operation of delinquent accounts in the company’s 13 million square of such facilities depends upon the cooperation of local public utility companies. This paper foot commercial portfolio. He oversaw the restoration of seven buildings that were severely damaged by Hurricane Sandy on examines the successes and failures of onsite energy production in a select group of buildings Front Street in Lower Manhattan. Currently, Alexander focuses built and managed by The Durst Organization in New York City. on project development, project management, financial analysis and acquisitions, working closely with father Douglas, cousin Jonathan and his sister Helena. Keywords: Energy Efficiency; Sustainability Overview Despite substantial innovation in sustainable building and renewable technologies in recent years, New York City’s large buildings remain the City’s largest energy consumers, accounting for some 45% of the City’s total energy usage (PlaNYC, 2012). The heaviest concentrations of high-demand tenants occur in the skyscraper-dominated commercial districts of downtown and midtown (Howard et al., 2012) (see Figure 1). Tall buildings continue to attract commercial tenants with high energy demands. Providing energy in an efficient manner to such intensive-demand tenants could significantly reduce New York’s energy consumption and carbon emissions in the immediate future. Older buildings have consistently lower EUI ratings than new large buildings, despite the fact that newer buildings are generally designed with more energy efficient technologies and construction principles. With limited workable occupancy data available, analysts suggest that this apparent discrepancy can be explained by the greater building population density and more extreme energy demands of commercial tenants in modern skyscrapers, which result in greater economic output (Aboff, Baumgartner & Coleman, 2014). Tenant bases comprised of such dynamic industries as financial services, communications, and digital media typically require 24- hour activity, open “bullpen” layout plans for large workforces, and heavy plug loads for multiple computers, monitors, and other technological equipment. In particular, trading floors may have such extreme energy demands as to require a unique categorization. Thus, high demand tenants pose a particular challenge, as well as a unique opportunity for the sustainable builder. Certainly, much good in the way of conservation can be achieved when a building remains committed to energy efficient operations. Energy reduction programs such as daylight dimming and occupancy sensing have achieved modest success in reducing wasteful use. Further, by conscientiously monitoring tenant needs and adapting protocols beyond benchmarking and commissioning stages, a building’s management can achieve optimal HVAC, lighting, and plug-load use. Such measures, however, should be considered best practices to limit excessive consumption: they do not solve the problem of finding an efficient means of delivering energy to heavy users. The essential metric when assessing a building’s efficiency of energy delivery is Source Energy Use Intensity (Source EUI). The Environmental Protection Agency’s EnergyStar program identifies weather-normalized source EUI as the critical measurement for analyzing energy efficiency because it accounts for the total energy required to produce the power consumed by a building, and it reflects onsite efficiencies or waste. The EPA indicates that the national average source-site ratio for electricity purchased from the grid is 3.14; i.e., every unit of electricity consumed at a building requires more than three times as much electricity (primarily from fossil fuels) to be consumed for the generation at the plant or plants. This is largely due to the inefficiencies of the power plants as well as losses during transmission. Natural gas, on the other 40 | CTBUH 2015 New York Conference Figure 2. 2012 & 2013 Energy and Water Data Disclosure for Local Law 84. (Source: The Durst Organization) hand, maintains a much more efficient ratio of 1.05; i.e., 1.05 units of natural gas leave a storage facility for every unit of natural gas consumed at a building site (EnergyStar, 2015). Naturally, electricity generated onsite has a site-source ratio of very close to 1.0, as there are negligible transfer, conversion, or distribution losses. To understand the efficiency of buildings in New York City it is helpful to review some examples of buildings built in the last twenty-five years. Figure 2 demonstrates that while One Bryant Park has a high site EUI compared to similar buildings in Manhattan, it also has the lowest ratio of source EUI to site EUI (i.e., its source EUI is a smaller multiple of its site EUI) because it produces energy, heating, and cooling onsite. Buildings that are able to reduce their demand for electricity from the grid using onsite generation are able to achieve a more favorable source-to-site EUI ratio, and greater efficiency. It follows that companies with intensive energy demands will be attracted to buildings that supply efficient energy for simple economic reasons: buildings that can supply energy efficiently to top consumers will be able to offer greater bottom-line savings to those tenants. Meanwhile, as long as public utilities designed to generate electricity Figure 1. An interactive online map by the Modi Research Group details New York City’s highest energy demand areas. from fossil fuels remain the sole or primary (Source: Modi Research Group/Sustainable Engineering Lab, Columbia University) source of electricity, energy supply will remain exceptionally inefficient while producing substantial greenhouse gasses. The most efficient way to supply electricity to a large building with minimal loss is through onsite generation. Generally, electricity can be produced onsite either CTBUH 2015 New York Conference | 41 from renewable sources such as solar technology by which tall buildings could sufficient electricity to offset each building’s and wind power, or from fuel cells and produce renewable energy. Of all renewable demand. The Bahrain World Trade Center (2008, generators relying on utility steam, natural energy sources, wind is the cheapest when 50 floors) in Manama, Bahrain (Figure 3), the gas, etc. Unfortunately, the vast majority harvested efficiently, and once a turbine is built Strata SE1 in London, UK (2010, 43 floors) and the of available data and anecdotal evidence and installed, it creates no greenhouse gasses Pearl River Tower (2011, 71 floors) in Guangzhou suggests that onsite renewable energy during energy generation. Because wind speed City, China (Figure 4) were among the first tall sources will not be sufficient to meet high typically increases at higher altitudes, the roof buildings in the world to use commercial-scale energy demands in tall buildings for the of a skyscraper could appear to a developer wind turbines for onsite energy production. foreseeable future. Nor is it clear that any as an ideal location at which to place a wind They were sited and designed to maximize wind such technologies will ever be feasible turbine. Yet multiple factors diminish the exposure and minimize impact on tenants and for large buildings in an urban setting. practicality and value of wind as an onsite neighbors. During development, each building This paper will briefly survey onsite wind, energy source for tall buildings. hoped to generate approximately 10% of its solar, and geothermal energy and heat energy needs from the wind turbines. However, production, and will document The Durst Wind turbines are maximally effective in available evidence suggests that the Bahrain Organization’s recent efforts