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DOE OSTI2015

A critical review of environmental assessment tools for sustainable urban design

Cities are responsible for the depletion of natural resources and agricultural lands, and 70% of global CO{sub 2} emissions. There are significant risks to cities from the impacts of climate change in addition to existing vulnerabilities, primarily because of rapid urbanization. Urban design and development are generally considered as the instrument to shape the future of the city and they determine the pattern of a city's resource usage and resilience to change, from climate or otherwise. Cities are inherently dynamic and require the participation and engagement of their diverse stakeholders for the effective management of change, which enables wider stakeholder involvement and buy-in at various stages of the development process. Sustainability assessment of urban design and development is increasingly being seen as indispensable for informed decision-making. A sustainability assessment tool also acts as a driver for the uptake of sustainable pathways by recognizing excellence through their rating system and by creating a market demand for sustainable products and processes. This research reviews six widely used sustainability assessment tools for urban design and development: BREEAM Communities, LEED-ND, CASBEE-UD, SBTool{sup PT}–UP, Pearl Community Rating System (PCRS) and GSAS/QSAS, to identify, compare and contrast the aim, structure, assessment methodology, scoring, weighting and suitability for application in different geographical contexts. Strengths and weaknesses of each tool are critically discussed. The study highlights the disparity in local and international contexts for global sustainability assessment tools. Despite their similarities in aim on environmental aspects, differences exist in the relative importance and share of mandatory vs optional indicators in both environmental and social dimensions. PCRS and GSAS/QSAS are new incarnations, but have widely varying shares of mandatory indicators, at 45.4% and 11.36% respectively, compared to 30% in BREEAM Community. Considerations of economic and cultural aspects are only marginal in the reviewed sustainability assessment tools. However, the newly developed sustainability assessment tools such as GSAS/QSAS and PCRS diverge from their predecessors in their consideration of cultural aspects. - Highlights: • Reviews six urban sustainability assessment methods: LEED-ND, BREEAM Communities, CASBEE-UD, SBTool{sup PT}-UP, PCRS, GSAS/QSAS. • Reviewed methods are biased more towards the environmental, followed by social and economic dimensions of sustainability. • Water issues are highlighted in the Middle East but natural hazards are emphasized only in CASBEE and BREEAM Communities. • SBTool{sup PT}-UP, the most recent of the groups puts more weight (7.32%) on cultural aspects. • Share of mandatory indicators is highest (45.4%) in the Pearl Community Rating System (PCRS)

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Methodology to evaluate design modifications intended to eliminate frosting and high discharge temperatures in air-source heat pumps (ASHPs) in cold climates

Air-source heat pumps (ASHPs) operating in cold climates experience problems with frosting and high refrigerant temperatures. These problems increase energy consumption, and their severity depends on the climatic conditions. In the present paper, a methodology for identifying the prevailing problem between frosting and high discharge temperatures is presented. Three performance indices, the frosting index (FI), the discharge index (DI), and the total loss index (TLI), are proposed to quantify the impacts of frosting and high discharge temperatures on the annual performance of ASHPs in different climatic conditions. The FI and DI show which problem (frosting or high discharge temperature) dominates, and the TLI indicates the combined effect of frosting and high discharge temperatures on the performance of an ASHP. A thermodynamic model of an ASHP coupled with the TRNSYS building simulation tool is used to estimate the performance of an ASHP and the proposed loss indices to estimate the impact of both frosting and high discharge temperatures for 45 cities in Canada. The results can be extended to other parts of the world that experience similar climatic conditions The results reveal that in cities in ASHRAE climatic zones 5 and 6 (classified as cold regions) where the ambient air temperatures are predominantly between -15 °C to 6 °C, ASHPs are heavily impacted by frosting. The problem of high discharge temperatures in ASHPs is predominant in cities in climate zones 7 and 8 (classified as very cold and subarctic regions) where the temperatures are frequently below -20 °C in winter. Among the cities considered, St. John, NL has the highest fraction of heating hours experiencing frosting (90 %), where the annual increase in energy consumption due to frosting is 13.5 % of the annual heating energy consumption. The highest annual increase in energy consumption due to high discharge temperatures is in Isachsen, NU (zone 8), where the increase is 30 % of the annual heating energy consumption. Based on the proposed indices, another index called the performance gain index (PGI) is created, which can be used as a first step to assess the energy-saving potential of design modifications applied to ASHPs to solve the problems of frosting and high discharge temperatures. The PGI will aid in developing climate specific ASHPs. One possible design modification is the use of a two-stage ASHP with an economizer. It is observed that the two-stage ASHP with economizer can mitigate high discharge temperatures and improve performance in very cold and subarctic regions (zones 7 and 8). However, it is not as beneficial in zones 5 and 6, where the impact of high discharge temperatures on performance is minimal and frosting dominates. Finally, a case study, using the PGI to evaluate the economic and environmental effectiveness of a two-stage ASHP with economizer is presented for the city of Saskatoon.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2019

Urban heat island impacts on building energy consumption: A review of approaches and findings

Urban heat island (UHI) could have significant impact on building energy consumption by increasing space cooling demand and decreasing space heating demand. However, the impact of UHI on building energy use was understudied due to challenges associated with defining UHI-induced temperature change and evaluating building energy use. In this paper, we reviewed the existing literature to understand the quantitative impact of UHI on building energy, which is represented by the difference in energy consumption of a representative building in urban and rural areas. The previous studies found that UHI could result in a median increase of 19.0% in cooling energy consumption and a median decrease of 18.7% in heating energy consumption. Moreover, the reported UHI impact showed strong spatial variation within and among cities; the impact on cooling energy use ranges between 10% and 120% while the impact on heating ranges between 3% and 45%. Building on the previous studies, the future research could extend the study of UHI impact in four ways: 1) exploring the spatial pattern of the UHI impact within a city by considering the intra-city variation of UHI intensity and building characteristics; 2) investigating the inter-city variation of the UHI impact and the influence of different characteristics such as geographical location, city size, and development stage; 3) expanding studies in developing countries where rapid urbanization is expected in the next few decades; and 4) projecting UHI impact with future patterns of urbanization and climate change.

urbanization, urban heat island, building energy c↗
DOE OSTI2025

Integrating Intelligent Hydro-informatics into an effective Early Warning System for risk-informed urban flood management

The urban drainage system constantly facing flooding issues in coastal and urban areas. Robust and accurate urban flood management, particularly considering fast-moving compound floods, is crucial to minimize the impact of flood disasters in coastal cities. Till now, Ho Chi Minh City (HCMC) lacks an effective means of urban flood management because of flood risk communication among residents. Existing flood risk communication tools rely on post-disaster flood model outcomes and data. Therefore, this research proposes a real-time Early Urban Flooding Warning System (EUFWS) integrated with a user-friendly web and app interface. The backbone of this system consists of flood models developed using machine learning (ML) algorithms, combined with big data and Web-GIS visualization, with ML serving as the core for constructing the EUFWS. EUFWS offer several key advantages: they are available at all times, accessible from anywhere, and provide a real-time, multi-user working platform. Additionally, the system is flexible, allowing for the easy addition of components and services and scalable, adjusting to workload demands. EUFWS have been successfully deployed in Thu Duc City, Vietnam, as a case study and are operating effectively. EUFWS have been successfully deployed in Thu Duc City, Vietnam, as a case study and are operating effectively. Research results indicate that EUFWS supported decision-makers to be effectively risk informed and make intelligent decisions during urban flood emergencies. Finally, this underscores the significant potential of integrating ML and information technology to enhance the management of smart urban drainage systems in flood-prone cities worldwide.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Divergent urbanization-induced impacts on global surface urban heat island trends since 1980s

Urbanization experiences different speeds and forms under diverse development stages across the globe. However, urbanization-induced impacts on long-term surface urban heat island intensity (I s ) trends across global cities and the regulators of such impacts remain understudied. Here we estimate interannual trends in daytime I s (i.e., urban-rural differences in surface temperatures) across 511 major cities for 1985 –2020 using annual averages calculated by using reconstructed land surface temperature data derived from more than >250,000 Landsat thermal images. Our study reveals that the global mean I s growth rate is 0.156 °C/decade. We further examine I s change associated with per 1% impervious land growth (denoted as ß) in each city throughout the research period and during different periods. The global mean ß is 0.018 ± 0.025 °C/% (mean ± 1 standard deviation) for the whole period, with greater values in humid than in arid climates; and the ß may change during different periods, e.g., it has more than tripled when urban impervious land exceeds 30%, indicating the spatiotemporally divergent impacts of urbanization on Is trends across global cities. The spatial variations in ß across global cities are well correlated with rural vegetation abundance and precipitation but not with urban population. Among these three factors, rural vegetation abundance possesses the greatest standardized regression coefficient of partial least-squares model, signifying the critical role of biome background in regulating ß. Furthermore, the finding implies that future urbanization over densely vegetated regions should be more carefully and strategically planned due to the greater urbanization-induced surface warming effect.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

A global urban heat island intensity dataset: Generation, comparison, and analysis

The urban heat island (UHI) effect, a phenomenon of local warming over urban areas, is the most well-known impact of urbanization on climate. Globally consistent estimates of the UHI intensity (UHII) are crucial for examining this phenomenon across time and space. However, publicly available UHII datasets are limited and have several constraints: (1) they are for clear-sky surface UHII, not all-sky surface UHII and canopy (air temperature) UHII; (2) the estimation methods often neglect anthropogenic disturbance, introducing uncertainties in the estimated UHII. To address these issues, this study proposes a new dynamic equal-area (DEA) method that can minimize the influence of various confounding factors on UHII estimates through a dynamic cyclic process. Utilizing the DEA method and leveraging various gridded temperature data, we develop a global-scale (>10,000 cities), long-term (over 20 years by month), and multi-faceted (clear-sky surface, all-sky surface, and canopy) UHII dataset. Further, based on these estimates, we provide a comprehensive analysis of the UHII and its trends in global cities. The UHII is found to be greater than zero in >80% of cities, with global annual average magnitudes around 1.0 °C (day) and 0.8 °C (night) for surface UHII, and close to 0.5 °C for canopy UHII. Furthermore, an interannual upward trend in UHII is observed in >60% of cities, with global annual average trends exceeding 0.1 °C/decade (day) and over 0.06 °C/decade (night) for surface UHII, and slightly surpassing 0.03 °C/decade for canopy UHII. Notably, there exists a positive correlation between the magnitude and trend of UHII, suggesting that cities with stronger UHII tend to experience faster growth in UHII. Additionally, discrepancies in UHII are found between different temperature data, stemming not only from distinctions in data types (surface or air temperature) but also from differences in data acquisition times (Terra or Aqua), weather conditions (clear-sky or all-sky), and processing methodologies (with or without gap filling). Overall, our proposed method, dataset, and analysis results have the potential to provide valuable insights for future urban climate studies. The UHII dataset is publicly available at https://doi.org/10.6084/m9.figshare.24821538.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Exploiting OMI NO 2 satellite observations to infer fossil-fuel CO 2 emissions from U.S. megacities

Fossil-fuel CO 2 emissions and their trends in eight U.S. megacities during 2006–2017 are inferred by combining satellite-derived NO X emissions with bottom-up city-specific NO X -to-CO 2 emission ratios. A statistical model is fit to a collection NO 2 plumes observed from the Ozone Monitoring Instrument (OMI), and is used to calculate top-down NO X emissions. Decreases in OMI-derived NO X emissions are observed across the eight cities from 2006 to 2017 (-17% in Miami to -58% in Los Angeles), and are generally consistent with long-term trends of bottom-up inventories (-25% in Miami to -49% in Los Angeles), but there are some interannual discrepancies. City-specific NO X -to-CO 2 emission ratios, used to calculate inferred CO 2 , are estimated through annual bottom-up inventories of NO X and CO 2 emissions disaggregated to 1 × 1 km 2 resolution. Over the study period, NO X -to-CO 2 emission ratios have decreased by ~40% nationwide (-24% to -51% for our studied cities), which is attributed to a faster reduction in NO X when compared to CO 2 due to policy regulations and fuel type shifts. Combining top-down NO X emissions and bottom-up NO X -to-CO 2 emission ratios, annual fossil-fuel CO 2 emissions are derived. Inferred OMI-based top-down CO 2 emissions trends vary between +7% in Dallas to -31% in Phoenix. For 2017, we report annual fossil-fuel CO 2 emissions to be: Los Angeles 113 ± 49 Tg/yr; New York City 144 ± 62 Tg/yr; and Chicago 55 ± 24 Tg/yr. A study in the Los Angeles area, using independent methods, reported a 2013–2016 average CO 2 emissions rate of 104 Tg/yr and 120 Tg/yr, which suggests that the CO 2 emissions from our method are in good agreement with other studies' top-down estimates. Lastly, we anticipate future remote sensing instruments – with better spatial and temporal resolution – will better constrain the NO X -to-CO 2 ratio and reduce the uncertainty in our method.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Linking transportation agent-based model ($\mathrm{ABM}$) outputs with micro-urban social types ($\mathrm{MUSTs}$) via typology transfer for improved community relevance

The human relationship with transportation is shaped by social, economic, demographic, and urban form variables, or socio-spatial factors. The spatial dynamics of these are key to generating and interpreting outputs of transportation models that are most relevant for a community and the diverse mobility needs of its members. Here we present a typology transfer framework, grounded in socio-spatial dynamics shaping people's mobility, to take transportation-themed regional mobility model outcomes, in this case from two agent-based models (ABMs), and extrapolate them to other cities, with less time and resource intensity than new ABM development. The typology transfer process first identifies micro-urban social types (MUSTs) using socio-spatial factors, then defines city types based on spatial patterns of MUSTs to assess across which cities transfer results are likely to best hold. Lastly, a typology transfer multiplier matrix extrapolates a given variable, in our case the Mobility Energy Productivity (MEP) metric, to another city. The full process demonstration uses ABM results from Chicago (POLARIS model) and San Francisco (BEAM model), applying them to New York City. We discuss how MEP or other outputs can be appropriately estimated and used for integrated, human-centered mobility analysis. Key findings include that this MUST framework of user-defined dependent and independent variables allows tailoring ABM results and interpretations to specific community needs and data availability. Findings clarify that positive outcomes can be targeted towards user groups, based on sociospatial characteristics, using a typology approach, such as inclusive access to mobility choices, transportation affordability, and greater efficiency in resource use.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2020

The Evolving Distribution of Relative Humidity Conditional Upon Daily Maximum Temperature in a Warming Climate

Abstract The impacts of heat waves in a warming climate depend not only on changing temperatures but also on changing humidity. Using 35 simulations from the Community Earth System Model Large Ensemble (CESM LENS), we investigate the long‐term evolution of the joint distribution of summer relative humidity (RH) and daily maximum temperature ( Tmax ) near four U.S. cities (New York City, Chicago, Phoenix, and New Orleans) under the high‐emissions Representative Concentration Pathway (RCP) 8.5. We estimate the conditional quantiles of RH given Tmax with quantile regression models, using functions of temperature for each city in July for three time periods (1990–2005, 2026–2035, and 2071–2080). Quality‐of‐fit diagnostics indicate that these models accurately estimate conditional quantiles for each city. As expected, each quantile of Tmax increases from 1990–2005 to 2071–2080, while mean RH decreases modestly. Conditional upon a fixed quantile of Tmax , the median and high quantiles of RH decrease, while those of the Heat Index (HI) and dew point both increase. This result suggests that, despite a modest decrease in median relative humidity, heat stress measured by metrics considering both humidity and temperature in a warming climate will increase faster than that measured by temperatures alone would indicate. For a fixed Tmax , the high quantiles of RH (and thus of HI and dew point) increase from 1990–2005 to 2071–2080 in all four cities. This result suggests that the heat stress of a day at a given Tmax will increase in a warming climate due to the increase of RH.

Yuan, Jiacan↗
DOE OSTI2026

Mapping Philadelphia's Floodscape: A 35‐Year Analysis of Coastal Urban Flood Hazards and Drivers

Low-lying coastal urban cities face significant flooding risks from river flooding (fluvial), storm surges and high tides (coastal), and intense local rainfall (pluvial). Accurately assessing these hazards requires modeling frameworks capable of capturing both the individual and combined effects of multiple flood drivers, as well as the diversity of flood scenarios that can arise from their interactions. In this study, we implemented a physics-based, high-resolution modeling approach to assess flood hazards in Philadelphia, PA, a coastal city exemplifying multi-driver flood risks over multiple decades (1985–2019), by simulating a wide range of flood events at a 10-m resolution. By integrating watershed, coastal, and urban flood models, we explicitly resolved the interaction between fluvial, pluvial, and coastal processes across the city. From these simulations, we identified flood hazard hotspots and systematically attributed the primary drivers of flooding for each event. The results suggested that 44% of Philadelphia's flood events were compound floods, primarily driven by fluvial-surge and fluvial-pluvial combinations. Notably, 77% of these events involved fluvial flooding, either as a single flood driver or in combination with other drivers, underscoring the dominant role of riverine processes in the city's flood hazard. Overall, this study demonstrates the value of a comprehensive, process-based approach for urban flood hazard assessment and highlights the importance of considering the full spectrum of flood scenarios to inform targeted and adaptive flood management strategies in coastal cities.

Compound flooding↗
DOE OSTI2015

Cultural implications of late Holocene climate change in the Cuenca Oriental, Mexico

There is currently no consensus on the importance of climate change in Mesoamerican prehistory. Some invoke drought as a causal factor in major cultural transitions, including the abandonment of many sites at 900 CE, while others conclude that cultural factors were more important. This lack of agreement reflects the fact that the history of climate change in many regions of Mesoamerica is poorly understood. We present paleolimnological evidence suggesting that climate change was important in the abandonment of Cantona between 900 CE and 1050 CE. At its peak, Cantona was one of the largest cities in pre-Columbian Mesoamerica, with a population of 90,000 inhabitants. The site is located in the Cuenca Oriental, a semiarid basin east of Mexico City. We developed a subcentennial reconstruction of regional climate from a nearby maar lake, Aljojuca. The modern climatology of the region suggests that sediments record changes in summer monsoonal precipitation. Elemental geochemistry (X-ray fluorescence) and $δ$ 18 O from authigenic calcite indicate a centennial-scale arid interval between 500 CE and 1150 CE, overlaid on a long-term drying trend. Comparison of this record to Cantona’s chronology suggests that both the city’s peak population and its abandonment occurred during this arid period. The human response to climate change most likely resulted from the interplay of environmental and political factors. During earlier periods of Cantona’s history, increasing aridity and political unrest may have actually increased the city’s importance. However, by 1050 CE, this extended arid period, possibly combined with regional political change, contributed to the city’s abandonment.

58 GEOSCIENCES↗
DOE OSTI2020

Urban warming advances spring phenology but reduces the response of phenology to temperature in the conterminous United States

Urbanization has caused environmental changes, such as urban heat islands (UHIs), that affect terrestrial ecosystems. However, how and to what extent urbanization affects plant phenology remains relatively unexplored. Here, we investigated the changes in the satellite-derived start of season (SOS) and the covariation between SOS and temperature (R T ) in 85 large cities across the conterminous United States for the period 2001–2014. We found that 1) the SOS came significantly earlier (6.1 ± 6.3 d) in 74 cities and R T was significantly weaker (0.03 ± 0.07) in 43 cities when compared with their surrounding rural areas (P < 0.05); 2) the decreased magnitude in R T mainly occurred in cities in relatively cold regions with an annual mean temperature <17.3 °C (e.g., Minnesota, Michigan, and Pennsylvania); and 3) the magnitude of urban–rural difference in both SOS and R T was primarily correlated with the intensity of UHI. Simulations of two phenology models further suggested that more and faster heat accumulation contributed to the earlier SOS, while a decrease in required chilling led to a decline in R T magnitude in urban areas. Furthermore, these findings provide observational evidence of a reduced covariation between temperature and SOS in major US cities, implying the response of spring phenology to warming conditions in nonurban environments may decline in the warming future.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

When energy doesn’t add up: use of an energyshed framework in assessing progress towards renewable energy transitions

Global progress in energy transitions to support climate mitigation goals has been slower than anticipated; this has prompted shifts away from traditional paradigms of regulated energy ownership towards a model of energy democratization by local communities and individuals. For example, in the United States, local communities in over 250 cities, counties, and states have made pledges to reach 100% renewable electrification by target dates ranging from 2020 to 2050. However, the availability of infrastructure and the competition for renewable energy resources, as well as lack of awareness of these limitations, present significant barriers to overcome. In this study, we explored a subset of 31 of these cities to assess their current electricity generation and how much further they have to go to meet their goals. Through an energyshed framework, we estimated powerplant electricity allocation to each city assuming competition for power from various renewable and non-renewable resource types, as well as look at the ‘best case scenario’ assuming 100% allocation of renewable-sourced electricity for a handful of cities in order to understand the existing and planned energy mixes for 2021 and the following 20 years. It is likely most cities will meet 10% of their energy demand with renewable energy, with best cases scenarios reaching between 35% and 65% renewable penetration, within the next 20–30 years. This highlights the need for infrastructural development in the energy sector, as well as intentional planning efforts in order to make these energy goals a reality.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

Recovery Act: Hydroelectric Facility Improvement Project - Replacement of Current Mechanical Seal System with Rope Packing System

On January 27, 2010 the City of North Little Rock, Arkansas received notification of the awarding of a Department of Energy (DOE) grant totaling $450,000 in funding from the American Recovery and Reinvestment Act (ARRA) under the Project Title: Recovery Act: Hydroelectric Facility Improvement Project – Automated Intake Clearing Equipment and Materials Management. The purpose of the grant was for improvements to be made at the City’s hydroelectric generating facility located on the Arkansas River. Improvements were to be made through the installation of an intake maintenance device (IMD) and the purchase of a large capacity wood grinder. The wood grinder was purchased in order to receive the tree limbs, tree trunks, and other organic debris that collects at the intake of the plant during high flow. The wood grinder eliminates the periodic burning of the waste material that is cleared from the intake and reduces any additional air pollution to the area. The resulting organic mulch has been made available to the public at no charge. Design discussion and planning began immediately and the wood grinder was purchased in July of 2010 and immediately put to work mulching debris that was gathered regularly from the intake of the facility. The mulch is currently available to the public for free. A large majority of the design process was spent in discussion with the Corps of Engineers to obtain approval for drawings, documents, and permits that were required in order to make changes to the structure of the powerhouse. In April of 2011, the City’s Project Engineer, who had overseen the application, resigned and left the City’s employ. A new Systems Mechanical Engineer was hired and tasked with overseeing the project. The transfer of responsibility led to a re-examination of the original assumptions and research upon which the grant proposal was based. At that point, the project went under review and a trip was booked for July 2011 to visit facilities that currently had an IMD installed. This further study of facilities revealed that the implementation of the project as originally described, while proving the benefits described in the original grant application, would likely intensify sand intake. Increased sand intake would lead to an increase in required shutdowns for maintenance and more rapid depreciation of key equipment which would result in a loss of generation capacity. A better solution to the problem, one that continued to meet the criteria for the original grant and ARRA standards, was developed. A supporting day trip was planned to visit other facilities located on the Arkansas River to determine how they were coping with the same strong amounts of sand, silt, and debris. Upon returning from the trip to other Arkansas River facilities it was extremely clear what direction to go in order to most efficiently address the issue of generator capacity and efficiency. Of the plants visited on the Arkansas River, every one of them was running what is called a rope packing shaft sealing system as opposed to mechanical shaft seals, which the facility was running. Rope packing is a time proven sealing method that has been around for centuries. It has proved to perform very well in dirty water situations just like that of the Arkansas River. In April of 2012 a scope change proposal was submitted to the DOE for approval. In August of 2012 the City received word that the change of scope had been approved. Plans were immediately set in motion to begin the conversion from mechanical seals to a packing box at the facility. Contractors arrived on October 1st, 2012 and the project team began unwatering the unit for disassembly. The seal conversion was completed on February 29th, 2013 with start-up of the unit. Further testing and adjusting was done throughout the first two weeks of March.

13 HYDRO ENERGY↗
DOE OSTI2015

Municipal Complex Solar Project

This project is a great benefit to the City of Perth Amboy by saving energy and savings costs. The project serves as a great example to city residents about the importance of renewable energy, energy conservation and other environmental topics. An electronic display in the City Hall shows how much energy was generated on that day, how much energy is saved, and environmental benefits. The project serves to educate people of environmental concerns and may spark the interest of individuals in other environmental topics. Hopefully, other residents will be encouraged to use solar energy. The project is also saving money for the City and its taxpayers. Anywhere we can save money means that residents can pay less in taxes and/or the City can provide improved services.

14 SOLAR ENERGY↗
DOE OSTI2019

Smart DG Hub Resilient Solar Project Final Report

Hurricanes, unstable fossil fuel supplies and increased energy loads have revealed the vulnerability of America’s electric grids. Renewable energy has emerged as a viable option; however in order for this sector to reach its full potential it needs to be paired with storage. For example, all of the solar installations in New York City in 2014 were wired to automatically shut down during grid outages for safety reasons and lacked battery backup or other means to function during outages. Pairing solar with batteries can provide critical power needs and reduce dependency on delivered fuel. Additionally, resilient solar systems can also provide benefits outside of emergencies such as utility bill savings and grid support services. Solar+Storage needed a pathway through regulatory, policy and financial hurdles, some of which are unique to urban environments. Sustainable CUNY of the City University of New York (CUNY) formed the Smart Distributed Generation (DG) Hub to develop a strategic pathway to a resilient distributed energy system that integrates storage into resiliency planning and provide support to the grid on peak power days. Through the Smart DG Hub Resilient Solar Project, with support from the U.S. Department of Energy (DOE) as well as the New York State Energy Research and Development Authority, the New York Power Authority and private funding, Sustainable CUNY worked with project partners - including the National Renewable Energy Laboratory, Meister Consultant Group (now Cadmus), subject matter experts at utility companies, and authorities having jurisdiction - to develop a roadmap for the greater deployment of solar+storage as well as a toolkit of resources. Ultimately, in addition to the completed deliverables of multiple resources, the project established a baseline of the current policy, financial, and market landscape, and an understanding of which key areas would require further actions. The DG Hub’s collaborative platform and subject matter expertise gained through this project led directly to a new award from the NYS Energy Research & Development Authority to continue CUNY’s work in targeted areas including energy storage permitting and stakeholder education, similar to the way DOE’s prior support had sowed the initial seeds for the growth of the solar market in NYC, to the NYS market. Finally, the Resilient Solar Project helped inform the New York City (NYC) administration, leading to a significant policy development that included Mayor Bill de Blasio setting a city-wide storage goal of 100 MW by 2020, the first of any city in the country.

25 ENERGY STORAGE↗
DOE OSTI2019

Economics of Solar PV and Stationary Storage for Electric Bus Charging in Missoula, Montana [Slides]

This analysis was conducted under the first round of the Solar Energy Innovation Network (SEIN), a program led by the National Renewable Energy Laboratory (NREL) that assembles diverse teams of stakeholders to research solutions to real-world challenges associated with solar energy adoption. This analysis supported the efforts of the Montana Solar Powered Community Transportation Initiative, a team consisting of the Montana Renewable Energy Association, Montana Energy Office at the Department of Environmental Quality, City of Missoula, City of Bozeman, City of Whitefish, Climate Smart Missoula, and Yellowstone-Teton Clean Cities. The team is investigating the synergies between solar generation and electric vehicle (EV) charging, including the potential opportunities and challenges related to co-locating solar energy and charging infrastructure to reduce costs and enhance co-benefits of the electrification of transportation. The City of Missoula's transit agency has purchased six electric buses. This analysis supports the team's efforts to understand the potential costs and specific options for using solar and storage to reduce EV bus charging costs.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2019

Akutan Geothermal: Resource Report

Geothermal energy resources are present in the Hot Springs Bay Valley geothermal area, and the City has invested considerable money and time in the exploration of the resource for future use. Exploration activities funded primarily through a grant the City was awarded from Alaska Energy Authority and later supplemented by the U. S. Department of Energy (DOE), with cost share from the City. The exploration led to the development of a geothermal resource conceptual model that was built and refined between 2008 and 2018. During this period, geological and geophysical studies, exploration drilling and other activities were completed, including a preliminary feasibility study for a power project, investigations of the terrain for suitability for access and development, environmental and archeological review, plus TG well abandonment and a review of economic considerations. The model of the resource predicts that there is a viable geothermal resource in two general areas: on the northwest edge of Hot Springs Bay Valley going northwest of the valley (hot springs area) and southwest of the Valley (fumarole area). The resource temperature for the valley area is expected to be about 170°C (340°F) and given the size and permeability estimates (with a factor for the level of confidence in the estimates), the mean power capacity of the outflow resource is 3 MWe and the P50 (most likely) power capacity is 1 MWe. The fumarole area has an expected resource temperature of 240°C (464°F) and given the size and permeability estimates mean capacity is 20 MWe and the P50 (most likely) capacity is 9 MWe. Permeability is the most difficult factor to predict and has a significant impact on the available geothermal fluids and therefore the amount of power that can be generated. The uncertainty in this value is the main reason for lower confidence in the likelihood of exploration success and the wide range in predicted MW values. The permeability has been difficult to locate as indicated by the results of the flow test at AK-3 in 2017. The test resulted in the production of some fluid, but due to low permeability, the recharge to the wellbore was too slow to sustain flow. The greatest probability of overall MWe production is in the fumarole region, but development is hampered by poor accessibility. The extremely high cost of road building for exploratory drilling, put an end to planning at an intermediate stage of the project and refocused attention on the viability of development in the hot spring outflow part of the resource. The City will be determining what the next steps are with AK-3, which is still that is still open and maintained in a suspended status in HSBV. While AK-3 remains accessible (not plugged with cement) it will need to be maintained. The City has a bond with AOGCC that will remain in place until the well is abandoned. GRG recommends that the well be maintained open as an asset for the foreseeable future.

15 GEOTHERMAL ENERGY↗