Advanced buildings & integrated communities: the next frontier of energy-water nexus
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Buildings and communities are complex, ever-changing organisms. On one hand, they are constantly transforming as a result of human-based factors, such as the interactions between their occupants, social mores, political establishments, and economic conditions. On the other, a mélange of man-made and natural systems, including building technologies, municipal water infrastructure, regional climate patterns, and the wider energy grid.
Untangling multifaceted relationships of buildings and communities are extremely difficult if not impossible. However, to streamline development, standard industry practice was to adopt a top-down, divide-and-conquer approach, which normalized multiple disciplines often working in isolation through centralized entities. Despite best intents, this segregation to development encouraged prioritization of individual systems over the whole, which left system-wide hierarchical stratification and interdependencies unevaluated and optimization opportunities underutilized.
With this backdrop, energy and water systems have long experienced a disconnection, which lead to enormous system-wide inefficiencies (i.e. carbon emissions) that added challenges to the climate crisis. While much headway had already taken place to inform energy and water communities their nexus broadly at the infrastructure level (i.e. water is required to extract, process, and consume fuels, and energy is required to source, treat, and distribute water), a lack of actionable knowledge[1] and the topic’s nascency plagued progress toward improved comprehension of their intricacies at the buildings’ and communities’ scales. To better grasp the relationships and consequences of buildings’ and communities’ energy and water usage, the following unanswered questions must be addressed: What are the next steps for the energy and water systems to curb carbon emissions? Where should we look to better understand their disconnections? And how can we enhance system integrations to withstand shocks from the changing climate?
In pondering these questions, I argue that advanced buildings and integrated communities are the next step towards expanding our knowledge of energy-water nexus, to advocate for their close examination through 3 distinct pathways listed below.
Decentralization: A new regime for civil infrastructure?
Following the footsteps of electricity grid that I explained previously, there is a growing interest towards the design, planning, and operation of water systems in a distributed fashion. Akin to the electricity grid, reason for said growth is because of costs associated with the distribution of water resources. Water is heavy and sensitive, and its conveyance is among the highest costs incurred for any water utility due to energy demand[2]. Furthermore, water—embodied carbon—is frequently lost along the distribution system through leaks and evaporation, which is difficult to detect before severe system failures.
In curbing carbon emissions, huge energy and water expended along the distribution system necessarily means that the collection/sourcing, treatment, and distribution of water supplies closer to their end-use—in or around buildings and communities—can reduce energy and water consumption. The less the water has to travel to get to its destination, the less water lost and energy consumed to move it. Consequent savings in other aspects are a cherry on top.
This idea is sound in concept. In fact, distributed and/or independent water systems exist, but for very niche and specific use cases, such as nuclear power plants (e.g. coolant), manufacturing facilities (e.g. rinsing), and other industrial applications. However, these are surrounded in a myriad of industry-specific regulatory requirements and processes for environmental protection. Likewise, their translation into typical buildings and communities is viable but demanding and unrealistic to perform, even at limited scales for the purposes of investigating infrastructure-wide ramifications of energy-water nexus.
Therefore, decentralized water systems at the scales of, and applications for, everyday buildings and communities present salient and potential opportunities to answer many questions, which include: What are the conditions that determine the configuration, scale, and technology of distributed systems across vastly different environments? How can consistency, safety, reliability, and accessibility of clean public water supplies be ensured? Which systems, processes, and end-uses can and should be decentralized?
Policies and regulations surrounding water is enormously complicated and awfully fragmented in the United States across all levels, which take away the agency of designers, engineers, and communities to exercise influence over what they do. Furthermore, lack of cooperation between different agencies make matters even worse[3]. However, despite the environmental and technological variations that lead to varying levels of interdependencies between energy and water systems in buildings and communities[4], distributed water systems more tangibly enable its immediate stakeholders to participate in, and respond to, their design, planning, operation, as well as energy and water consumption behaviors (i.e. costs), while also providing additional touch points for scientists, engineers, and regulators to gather data to better understand and project future needs.
Big data: Quantification of demand-supply interdependencies?
Speaking of data, a significant data gap in understanding the push-and-pull of energy and water systems exist across all scales, but especially at the buildings’ and communities’ levels[3]. In particular, data points surrounding the use of hot water, its relationship to the energy loadshape, adopted rate structures, and real-time resource availability are just some of the key missing information[5], which could help unpack uncertainties in the energy-water nexus through and through. However, such in-depth datasets are currently lacking due to limited intervention points for collection (as the saying goes “there is never enough data”), and those that are available often need to be vetted appropriately to ensure privacy (e.g. personally identifiable information) which add additional barriers to obtaining and making effective use of them.
Detailed data for water cost of energy demand at the scales of buildings and communities is important, because it will inform a more accurate model to estimate future needs in planning the operations of infrastructures at large scale[1]. There are enough convincing evidences of energy-water nexus at the buildings’ and communities’ scales, from focused and isolated studies examining the opportunities to save both energy and water from use of efficient boilers[4], harvesting rainwater versus on-site treatment and reuse of greywater[6], recovering energy from hot water drainage[7], using hot water as energy [thermal] storage[8], et cetera. However, with tens of building types built using different codes, techniques, materials, fixtures, equipment, size, and end-use, spread across vast geographic areas representing different climates and hundreds of diverse social, cultural, ethnic, and economic backgrounds, each variable can drive unique user behaviors and seriously complicate the results[9].
In that vein, thousands of buildings currently exist with LEED, Living Building Challenge, and other similar rating certifications, with initial and recertification building performance data available for deeper analysis to quantify the demand-supply of energy and water simultaneously. However, these certification programs are voluntary code measures, meaning those that “opt-in” are making intentional choices and may have predispositions (some of which I wrote about previously). Therefore, the data could represent specific subsets of cases unsuitable for generalization. Furthermore, most certification programs attempt to make the process as easy to pursue as possible. Consequently, to simplify complex concepts, applications of certification requirements do not make meaningful associations between energy and water. This bifurcation of energy and water at the code level is not isolated to voluntary certification programs, and are deeply rooted in the existing building regulations, including codes and standards that encourage it.
Confluence: Unified framework for codes & standards?
Codes and standards is another area in which the energy-water nexus is a niche topic. There has been an increasing recognition of their nexus among those developing codes and standards, such as the U.S. Department of Energy (DOE), Environment Protection Agency (EPA), and even the U.S. Geological Survey (USGS). Still, concrete actions and integrations of energy and water through policies and regulations is minimal (at least in my personal opinion), and have largely focused on national-regional scales to understand the issues more broadly first.
There is a delicate choreography between local, regional, and national bodies in crafting codes and standards. Local and regional codes cannot be less stringent than the national requirements, and national requirements cannot be too stringent as to impose unreasonable burden on local and regional communities (e.g. one cannot expect all of Alaska to be net-zero carbon in real-time all the time because the entire state is too cold to limit hot water and electricity use, and does not get enough sunlight to generate renewable energy a big chunk of the year). Similarly, federal agencies need to understand the larger picture to develop policies and regulations that encourage and support local and regional bodies to go above and beyond, but this cannot be done without understanding the local and regional conditions first.
This is where buildings and communities with LEED, Living Building Challenge, and other similar rating certifications become useful, in helping to fill the data gap to understand local and regional conditions. However, as I alluded to earlier, considerations and applications for water use as part of energy use, vice-versa, is unexplored and not considered in these rating systems, and consequentially lacking in the resulting buildings[10]. Furthermore, adopted state codes, local ordinances, and even Reach/Stretch codes are almost always amended derivations of the International Code Council’s (ICC) model codes (I-Codes). These rarely incorporate energy-water nexus into the code language, inadequately address integrations of distributed water (and energy) systems[11], and isolate energy and water into distinct categories under different code areas (e.g. electrical, plumbing, and mechanical to some extent). These code divisions allow for focused examinations and therefore streamlined enforcement, but leaves much to be desired in nurturing a more holistic approach to integrating building technologies and urban systems.
Pursuing more sustainable, optimal pathways that are environmentally, ecologically, and even financially-friendly is a confluence of all the pieces clicking in-to-place simultaneously. There is no one person, organization, or government that is hindering progress or responsible for moving the needle. Current shortfalls in codes and standards are products of system-wide inadequacies, which stem from a lack of understanding that follows insufficient data from hundreds and thousands of touch points representing equally diverse conditions. Buildings and communities provide unprecedented opportunities to study the energy-water nexus, not only for the sake of cutting carbon emissions locally, but in planning the larger infrastructure to further reduce subsequent environmental harm globally.
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K. Smith, S. Liu. (2017). Energy for Conventional Water Supply and Wastewater Treatment in Urban China: A Review. Global Challenges 2017, 1, 1600016. https://doi.org/10.1002/gch2.201600016.
H. Amirreza, K. Dolaana. (2020). Exploring Water-Energy Nexus at the Building Level. ASHRAE Transactions, Atlanta, 126, 308-314. https://www.proquest.com/openview/4d970dea8a82f8c825863da123fce971/1?pq-origsite=gscholar&cbl=34619)%20(https://sanjoseashrae.wildapricot.org/resources/Documents/24-31_Poole.pdf.
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R. Raveendran, et al. (2020). Diagnoses for Potential Enaction of Water–Energy Nexus in Green Building Rating Systems: Case Study of the Pearl Rating System of United Arab Emirates. Energies, 2020, 13(20), 5284. https://doi.org/10.3390/en13205284.
P. Kalehbasti, M. Lepech, C. Criddle. (2022). Integrated Design and Optimization of Water-Energy Nexus: Combining Wastewater Treatment and Energy System. Front. Sustain. Cities. 03/2022. https://doi.org/10.3389/frsc.2022.856996.