Fonte (Source): Consulting – Specifying Engineer

Por (By): Andrew Solberg, Coy Miller, and Keith Kibbee, CH2M

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Implementing key enablers, high-performance manufacturing or industrial buildings can become extremely efficient.

Learning objectives

• Define net zero energy building (NZEB) and positive-energy building (PEB).
• Identify key enablers to the realization of PEBs.
• Describe PEB solutions for manufacturing/industrial buildings.

Green building programs can be credited for bringing together a diverse group of stakeholders that are responsible for the design and operation of the built environment, and creating an informed conversation around the value of holistic building design. Green building rating programs and standards—including the U.S. Green Building Council LEED program (U.S.), Living Building Challenge(U.S.), BREEAM (U.K.), HQE (France), ESTIDAMA (United Arab Emirates), CASBEE (Japan), GreenMark (Singapore)—have energy efficiency requirements, as well as additional credits associated with energy demand reduction. These programs also reward participants for installing on-site renewable energy systems, and sourcing offsite macrogrid renewable energy. Building rating programs have contributed to the plethora of energy-efficient buildings worldwide. They have facilitated the identification of key efficiency strategies and propagation of cutting-edge technologies while creating a demand for on-site and offsite renewable energy. They have opened the door for the next generation of green buildings—buildings that are energy-positive and harvest more energy than they consume. Positive is the new green.

Whether a building is deemed green, smart, intelligent, or high-performance, efficient use of energy resources will undoubtedly be at the core of the design, and rightly so. Buildings and their systems consume more energy and generate more emissions than any other sector in the U.S., and likely the world. Combined, residential and commercial buildings account for nearly 30% of the total energy use in the U.S., industry accounts for about 33% (8% building systems and 25% manufacturing processes), and transportation consumes the remaining 37% (25% vehicles and 12% air-marine-rail-pipeline transport).

Thus, buildings account for approximately 38% of U.S. energy consumption today. With increasing electrification of vehicles, transportation loads will likely shift from the gas pump to electrical meters, resulting in more than 40% of U.S. energy consumption occurring behind the meters of buildings in coming years (see Figure 1). This concentration of load behind the meters of buildings provides a clear opportunity—and responsibility—for building owners, architects, engineers, financiers, and constructors to significantly change how energy is consumed and generated in the U.S. In doing so, they also have tremendous positive impact on built infrastructure operational costs, reducing air emissions, and enabling new technology. A net zero energy building (NZEB) generates enough renewable energy on-site to equal its annual energy use. A positive-energy building (PEB) produces more energy from on-site renewable sources than it consumes. The level of excess energy should be sufficiently high to offset the embodied energy of the building infrastructure over the building’s lifetime. In either case, grid connection is allowed and power is delivered to or extracted from the grid. Energy storage may be deployed to control the timing and amount of grid power used.

The benefits of net positive

PEBs are the pinnacle of green building design. There is no question regarding the sustainability of buildings that produce more energy than they consume. PEBs are expanding the conversation regarding high-performance buildings. A green building’s effectiveness must include not only the operational energy but also the embodied energy of the building materials. By considering the embodied energy, we capture the ultimate footprint of a building, from concept to present operation. A PEB’s excess energy has the potential to offset its own embodied energy, and to pay off historical energy debts.

Embodied energy within building materials will be reduced in the future as materials are created in net positive manufacturing facilities and material transportation systems. PEB’s excess

energy also has the potential to offset the building occupants’ transportation energy used in commuting to and from the building. It is already the case where electric vehicle owners charge at home where they have rooftop photovoltaic (PV) arrays, and charge at work based on parking lot PV arrays. The energy payback and emission/resource offsets are, undoubtedly, the marked benefits of PEBs.

Driver of green industry

The single goal of creating a PEB is to simplify the design process, essentially liberating the design team from the burden of estimating percent savings over a hypothetical baseline model for the purpose of achieving a green building ranking. When the goal is net zero energy, or positive energy, a different approach is embedded in the design process. With more stringent design conditions, engineers begin from a budget based on available energy that can be harvested and stored on-site. These conditions drive efficient design by holding the process accountable to the availability of limited resources. Additional costs associated with on-site energy systems and advanced building materials are often paid back over the lifetime of the building by the power produced by the building after construction. Therefore, PEBs increase the demand for higher cost, more advanced materials by balancing the lifecycle costs of the project, ultimately bolstering the market for high-performance building technology.

Fringe benefits

Arguably, one could make sustainability claims solely based on achieving a PEB alone. However, there are many other facets of green building, such as indoor air quality, daylighting, and positive community feedback, that could be overlooked if the focus is on energy alone. Therefore, it is worth mentioning that positive-energy design will likely enhance the greater quality of the edifice. The need for more efficient lighting will enhance daylighting, the benefits of which have become common knowledge. Research, such as that conducted by the Lighting Research Center in Troy, N.Y., has shown that daylighting increases occupant comfort and productivity, and provides the proper stimulation to regulate healthy circadian rhythms. Indoor air quality may be improved as well by shifting the traditional approach to more efficient ways of controlling interior conditions. For example, use of natural ventilation can help reduce symptoms of sick building syndrome by decreasing concentrations of pollutants from indoor sources. Finally, PEBs will enhance a community’s perception and value of the buildings they interact with, leading to community support and positive feedback. Ultimately, the fringe benefits beyond energy balance should not be overlooked.

Vision

The first step to creating net zero and positive-energy buildings is simply having the vision, and articulating it in such a way that stakeholders completely understand the benefits. Many companies are doing so. References and examples that illustrate the benefits and costs of high-performance buildings are leading the charge to achieving energy balance. Intel, Microsoft, Apple, Proctor & Gamble, Google, and others have declared their commitment to becoming carbon neutral. They recognize the value in green building and are leading the way by aspiring and planning for energy balance. For example, Tesla has recently announced plans to construct a massive “gigafactory,” a facility that will produce finished battery packs on a large scale from raw materials. The process of manufacturing these batteries is an energy-intensive process that traditionally relies on cheap, highly polluting sources. However, Tesla’s new facility will be powered largely by on-site renewable energy generation, mostly wind and PV. Tesla’s internal studies suggest that the carbon footprint of a single battery pack from the gigafactory will be completely offset after 10,000 miles of driving in its Model S, potentially making the battery the most carbon-neutral component in the vehicle.

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