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• This paper proposes a comprehensive optimization program to increase economic efficiency and improve the resiliency. • A demand response program integrated with home energy storage systems is presented to optimize energy consumption. • To modify the consumption pattern of household consumers, a real-time pricing algorithm is proposed. • A self-healing system reconfiguration program integrated with distributed energy resources is presented. • Real data of California households are considered to model the home appliances and home energy storage systems. This paper proposes a comprehensive optimization program to increase economic efficiency and improve the resiliency of the Distribution Network (DN). A Demand Response Program (DRP) integrated with Home Energy Storage Systems (HESSs) is presented to optimize the energy consumption of household consumers. Each consumer implements a Smart Home Energy Management System (SHEMS) to optimize their energy consumption according to their desired comfort and preferences. To modify the consumption pattern of household consumers, a Real-Time Pricing (RTP) algorithm is proposed to reflect the energy price of the wholesale market to the retail market and consumers. In addition, a Self-Healing System Reconfiguration (SHSR) program integrated with Distributed Energy Resources (DER), reactive power compensation equipment, and Energy Storage Systems (ESSs) is presented to manage the DN energy and restore the network loads in disruptive events. The reconfiguration operation is performed by converting the isolated part of the DN from the upstream network to several self-sufficient networked virtual microgrids without executing any switching process. Real data of California households are considered to model the home appliances and HESSs. The proposed comprehensive program is validated on the modified IEEE 123-bus feeder in normal and emergency operating conditions. [ABSTRACT FROM AUTHOR]

Inequities in the built environment have long persisted in communities around the world. Prior studies have exposed that energy retrofit programs invest inequitably in residential buildings, leaving racial minorities with disproportionately less energy inefficient homes, regardless of income level. This inequity in energy performance and retrofit investments has yet to be studied for commercial and institutional buildings. Further research has shown that tree canopy coverage and vegetation is less dense in historically disadvantaged communities, contributing to a greater urban heat island effect and corresponding higher energy consumption for cooling compared to historically advantaged communities. Moreover, there is limited albeit emerging research that utilizes granular socioeconomic data with fine temporal scale energy consumption data to help identify energy inequalities among race and income groups. This paper examines the differential impact of energy efficiency retrofit installation on energy performance between advantaged vs. disadvantaged groups using data from U.S. public school buildings. Additionally, it studies how the effect of retrofits is compounded by the presence of vegetation surrounding the building. Utilizing hourly interval smart meter data from primary and secondary school buildings in California, the impact of retrofits are quantified using three energy metrics. Then the disparities in retrofit impact for advantaged vs. disadvantaged groups (as defined by three equity metrics) are evaluated using school-level demographic data. Lastly, regression on the percent change in monthly energy consumption from the pre-retrofit to post-retrofit period is used to quantify the incremental benefits of retrofits compounded by vegetation. Findings show that energy efficiency retrofits can improve energy performance and reduce energy inequities. Specifically, retrofits significantly increase energy efficiency and reduce the energy efficiency equity gap by up to 198%. Evidence shows that vegetation surrounding a building has a synergistic effect with mechanical retrofits for reducing energy consumption in respect to reduced cooling loads, even in cases where mechanical retrofits alone resulted in significant increases in energy consumption. Dense vegetation provides around 6% energy savings, similar in magnitude to savings from mechanical retrofit installation. This validates the effectiveness of retrofits for reducing energy consumption and improving energy equity, and demonstrates the ability of vegetation to provide additional energy savings beyond mechanical interventions. [ABSTRACT FROM AUTHOR]

A review of 14 leading energy efficiency program administrators demonstrates that high levels of energy savings are not only achievable but also sustainable. Despite substantial challenges that may limit savings opportunities in traditional areas, energy savings have increased from year to year. Average net energy savings levels have doubled for the administrators in this sample, from 0.9% in 2008 to 1.8% in 2014. Utility-sector energy efficiency programs have grown substantially in the past decade. According to the most recent ACEEE State Energy Efficiency Scorecard, electric-efficiency program investments have increased from approximately $1.5 billion in 2006 to over $5.9 billion in 2014. As savings levels have increased, national leaders in program administration have emerged. In this paper we review annual program performance for 14 leading energy efficiency program administrators. We sought diversity in the selection of program administrators and included administrators of varying service-territory size and geographic location. Among the 14 program administrators we reviewed, none achieved electricity savings of 1.5% of retail electric sales in 2009. By 2014, 8 of the 14 were achieving savings higher than 1.5%, with 4 of the 8 saving more than 2%. The data also show that high savings are sustainable over time. We find that as savings rise, levelized costs of energy efficiency remain relatively flat. This paper also seeks to identify the drivers of high savings. State or local policy requirements to meet specific energy-efficient savings goals guide all program administrators in this study. The design of the targets and goals vary, but these policies are critical in driving high levels of savings. [ABSTRACT FROM AUTHOR]

• A novel c-Si based semi-transparent BIPV laminate was introduced. • Energy performance of the BIPV insulated glass unit (IGU) was investigated. • The BIPV laminate has high energy conversion efficiency and visible transmittance. • The BIPV laminate could reduce discomfort glare compared to clear glass windows. • The shade effect was influenced by the solar cell configurations and shading patterns. This paper introduces a novel c-Si based building integrated photovoltaic (BIPV) laminate. It was produced by cutting standard crystalline silicon solar cells into narrow strips and then automatically welding and connecting the strips into continuous strings for laminating between two layers of glass. The overall energy performance of the BIPV insulated glass unit (IGU) including power, thermal and daylighting performance was investigated experimentally. The daily energy conversion efficiency of the active solar cell area was about 15% on sunny days, but it was less than 12% on cloudy days and overcast days. Due to the combined effect of both the semi-transparent PV laminate and the insulated glass unit, the solar heat gain coefficient (SHGC) of the BIPV IGU was as low as 0.25, which was much lower than commonly used glazing windows. Daylight analysis by means of high dynamic range (HDR) cameras and daylight glare probability (DGP) indicated that the BIPV IGU could reduce discomfort glare to some extent compared to clear glass windows. The net energy production of the BIPV IGU was estimated without considering the differences in HVAC energy use in this study. The artificial lighting energy consumption was about 431 W h/day while the average BIPV electricity production for the same period was 1940 W h/day. The net power generation was therefore 1509 W h/day for this BIPV IGU in Berkeley, California. Shading tests for the BIPV IGU were also conducted and the results revealed that the vertical configuration of solar cell wiring in the BIPV laminates was much more sensitive to horizontal shading patterns than vertical shading models. Thus, if shading was unavoidable in some cases, a reasonable arrangement of PV strings should be considered to bring down the energy loss as much as possible. Also, the impacts of environmental factors on the energy conversion efficiency of BIPV IGU were analyzed. Specifically, the power output declined by 0.42% of the peak power for each Celsius degree temperature rise. Thus, if more attention was paid to the heat dissipation issue of BIPV IGU, the overall energy conversion efficiency would be improved. [ABSTRACT FROM AUTHOR]

In California, the majority of office and other nondomestic buildings use mechanical cooling and ventilation even when an optimized natural ventilation (NV) system could meet cooling and fresh air requirements. Unfortunately, in most large California cities, the outdoor environment is contaminated with noise, fine particles, heat, toxic gases or, in most cases, a combination of all four. This contaminated environment has a detrimental impact on naturally ventilated buildings due to their lack of filtration and outdoor noise attenuation systems. This paper presents a study on the impact of airborne particle pollution on the potential for NV cooling of office buildings in California. The study uses a multi-year database of measured hourly weather data and PM2.5 data for the five largest metropolitan areas in California, representative of 90% of the state’s population. The analysis is performed in two stages with increasing complexity. The first stage is a statistical analysis that identifies coincidence between high PM2.5 and outdoor air temperatures that are suitable for NV. In addition, this phase includes multivariable correlation to identify particular weather events or time periods that affect PM2.5 levels. The second level of analysis is more complex, using building thermal simulation (EnergyPlus) to perform a detailed assessment of NV potential in the five urban locations, calculating NV flow rates, resulting indoor exposure to PM2.5 and supplemental HVAC system energy consumption. The results show that using NV in moments when the outside weather is favorable can result in HVAC energy savings of 25–80%. However, limiting NV use to moments with outdoor particle levels below 12 μg/m 3 decreases this energy saving potential to 20–60%. In addition, in the majority of the cities analyzed in this study, the use of NV leads to an increase in indoor exposure to PM2.5 of outdoor origin of 400–500%. [ABSTRACT FROM AUTHOR]

In this paper we study the performance of 855 large (⩾10 kW) commercial rooftop photovoltaic (PV) system installations in California. Drawing on the nonparametric data envelopment analysis (DEA) method, our study takes the PV capacity, electricity generation, modules, system cost, solar irradiance, and ambient air temperature into account to provide a unified measure of the PV installation performance. This approach can overcome some of the limitations of simple output-to-input ratio analysis and allow us to assess whether solar capacity and electricity generation have been efficiently integrated into the grid in a holistic way. We find widespread inefficiencies in roughly 80–90% of the installations both within a specific year and across different years. There is a significant efficiency gain in solar installation from 2008 to 2012. Through regional analysis, we find high dispersions of performance across counties and cities, and identify locations where PV installations have achieved the best performance. The analysis also sheds lights on the magnitude of the gap between inefficient installations and efficient ones. [ABSTRACT FROM AUTHOR]

• Propose a method for embedding demand flexibility into building benchmarking. • Utilizes emerging building characteristics and time-series energy data streams. • Apply method to case study of 306 buildings in Southern California, USA. • Demonstrates ability to cluster buildings by attributes of demand flexibility. • Can inform decarbonization performance-specific policy targeting for buildings. The intermittency of carbon-free renewables and the demand changes associated with the widespread push for electrifying the transportation and building sectors provides an opportunity for buildings to go beyond energy efficiency and push towards providing demand flexibility to the electricity grid. The duality of energy efficiency and demand flexibility is necessary for success in a sustainable and reliable energy transition. Current building energy benchmarking models are limited in their ability to integrate concepts of demand flexibility and/or utilize granular smart meter data. Thus, current benchmarking methods are focused annual energy usage and fail to incorporate how the time of use of energy consumption impacts emissions in a quickly changing energy grid. Without a more comprehensive view of energy usage and associated real-time emissions, current benchmarking methods are unlikely to realize the full decarbonization potential of buildings. New emerging data streams provide an opportunity to develop a new generation of benchmarking energy models that embed dimensions of energy efficiency, grid interactivity, and demand flexibility into their analysis. In this paper, we propose a four-step method for embedding grid interactivity and demand flexibility into building benchmarking models that utilizes emerging building and time-series electricity data streams. We first engineer features to produce a mix-type dataset that encompasses many attributes of grid-interactive and efficient buildings, and then we apply K-medoids using Gower's Distance to produce peer-group clusters. We apply the method to a case study of 306 primary and secondary schools in southern California, USA. The results show that the method effectively clusters buildings by attributes of demand flexibility and energy efficiency. The clustering results reveal patterns in inefficient building operations and demand inflexibility at the building peer group level. The interpretation of clusters can serve as an integrated energy efficiency and demand flexibility benchmarking model and inform performance-specific policy targeting for buildings that go beyond traditional efficiency measures. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, an EnergyPlus model was used to simulate the operation of a novel integrated HVAC system. This system combines an underfloor air distribution system with a cooled radiant ceiling slab. A cooling tower supplies water to pre-cool the structural slabs during the night and early morning period. The paper compares the performance of this system to both a typical overhead system and a typical UFAD system in the cooling season for the Sacramento, California climate. When compared to the overhead system, the integrated UFAD/Radiant system shows a 22–23% reduction in total energy consumption during the peak cooling months (June to August) and a 31% reduction in peak hourly electricity demand. When compared to the UFAD system, these reductions are 21–22% and 24% respectively. An investigation of the simulation results showed that the integrated UFAD/Radiant system also improves occupant thermal comfort and reduces thermal decay issues in the underfloor plenum. [Copyright &y& Elsevier]

• Zero net energy is feasible when clean fuel is combined with electrification. • Building energy consumption valuation method impacts the component sizing. • Time dependent valuation of energy in California reflects its cost and emissions. • Solid oxide fuel cell provides efficient electricity and heat at the building. • Building can go off-grid with optimized operation of battery and fuel cell. California is seeking to mandate Zero Net Energy (ZNE) buildings by 2030 as part of its efforts to combat climate change. A ZNE building is required to compensate its annual energy consumption from the grid (electricity or gas) by injecting clean electricity back to the grid. So far, the most common approach for a ZNE building is utilizing solar photovoltaic (PV) or a PV and battery energy storage system. One key problem is the feasibility of installing PV if the surface area requirement is too large to achieve ZNE; another issue is grid congestion during the off-peak hours of midday when a large number of houses export their excess solar power to the grid. Hence, other ZNE home scenarios need to be evaluated to tackle these restrictions in achieving California's climate goals. In this work, we proposed and evaluated different system arrangements to reduce the required PV installation that is commonly installed as power generation source for ZNE residential units in California. The aim of this technical analysis is to provide a societal level policy guidance to accelerate fulfilling the ZNE home mandate. Due to the availability of the gas grid and potential for having more renewable gas in the grid, we investigated using gas-based heat generation versus only electric-based heat appliances. In addition, we incorporated a residential solid oxide fuel cell (SOFC) on the building site as a micro combined heat and power (mCHP) to facilitate achieving ZNE. The impact and contributions of different components, including energy storage, on grid-dependence, and the overall energy demand are also studied. With analysis of different mix of technologies that could be used for a ZNE home, we propose the potential solutions and discuss their strengths and weakness. In this paper, energy performance and optimal PV capacity are assessed for a ZNE home in all 16 climate zones of California established by California Energy Commission (CEC). The ZNE measurements for all four scenarios are based on three metrics of energy evaluation: (1) site energy (energy measured by the meter used at the building site); (2) source energy (raw fuel consumption at the source of energy generation to account for energy loss in production and distribution); and (3) time dependent valuation (TDV) of energy, which has been developed by the CEC to comply with its building energy efficiency standards. The TDV of each energy type depends on the time of use, climate, grid constraints, and other factors that reflect its societal value at any given hour of the year. The PV size required by each ZNE metric is calculated and compared. The results proved that relying on some gas in addition to electricity improves the practicality of required PV for ZNE homes particularly in regions with high heating demands. It was found that depending on the energy metric (site, source, and TDV), a different arrangement is required for the most efficient ZNE performance. Unlike the site metric, using source and TDV metrics where electricity is more valuable than gas shows that having both gas and electricity significantly reduces the PV size. This encourages investment in introduction of more renewable gas in the grid as one possible solution to achieving ZNE in individual homes. The great impact of an mCHP SOFC on a ZNE home in terms of reliability and feasibility points to the need for research, development, and commercialization to reduce the cost of mCHP SOFCs in residential application. Also, the addition of a battery does not reduce the PV size with site and source metrics; it only reduces the electric grid reliance. However, with TDV, where the time of energy consumption affects its value, not only does it reduce grid reliance during peak hours, but also less PV is required to achieve ZNE. [ABSTRACT FROM AUTHOR]

Traditional energy and demand savings metrics for distributed energy resources (DER) do not accurately describe the value of DERs to meet future energy needs, minimize grid investments, maintain reliability, and reduce greenhouse gasses. This problem is exacerbated in an increasingly renewable grid in which DER impact varies significantly with time and location. Moreover, different DERs are also valued using disparate metrics; this fragmented DER valuation and procurement creates process and economic inefficiencies. A new path forward is the Total System Benefits metric (TSB); the TSB aggregates all electric system benefits, and relevant environmental externalities that accrue to DERs. The TSB is the only metric that comprehensively values DER's to meet future electric system needs and environmental policy goals. This common metric will enable electricity planners, regulators, utilities, and implementers to best deploy and track DER to meet electric grid and environmental policy needs. This paper explains why the TSB is the right metric to value all DER, data requirements to develop the TSB, how to express DER in terms of the TSB, and lessons learned so far from California's implementation of the TSB. [ABSTRACT FROM AUTHOR]

• Ownership structure of small commercial buildings makes energy retrofits challenging. • Retrofit package for Zero Net Energy small offices in Mediterranean climate. • Energy use and occupant comfort evaluated experimentally, side-by-side, in real time. • 65%-68% energy savings for cooling season; 22%-25% for heating season. • Energy savings are achieved while maintaining visual and thermal comfort. Making buildings zero-net energy (ZNE) is one of the major strategies for achieving carbon emission reduction goals. For this strategy to be successful, it entails a very significant reduction in energy use – 50% or more. In small commercial buildings, however, owners and building management teams usually have limited resources for identifying, analyzing, and procuring appropriate retrofit measures for reducing such use. An approach to overcome this limitation is the development of bundles of energy efficiency measures that can be presented to building owners/operators as a comprehensive package. The research presented in this paper focuses on an experimental evaluation of the impacts of a retrofit package developed for small office buildings in California. Performing this evaluation in a full-scale whole-building integrated systems test facility allowed a side-by-side evaluation in real time, against a reference case, of the impact of the retrofit package not only on energy use but also on visual and thermal comfort. The retrofit package evaluated is comprised of a combination of HVAC, lighting (including daylighting), and plug load measures. The evaluation occurred at different times of the year in order to account for seasonal variations in environmental conditions, including solar angles and weather. The experimental facility allowed testing for two different façade orientations: south and west. Results show that the proposed ZNE retrofit package can save significant amounts of energy for small commercial buildings. During cooling-prevalent periods, total energy savings were 65% for south orientation and 68% for west orientation; during heating-prevalent periods total energy savings were 22% for south orientation and 25% for west orientation. Measurements indicate that the ZNE retrofit package resulted in small but not very significant changes in comfort levels for building occupants. [ABSTRACT FROM AUTHOR]

Battery electric vehicles (BEVs) are important for reducing fuel consumption and vehicle operating cost, and have the potential to reduce GHG and pollutant emissions. However, the range limits and long recharging times serve as obstacles to mass deployment. Well planned Level 3 DC fast charging stations are a potential solution to satisfy long distance travel demand instead of an expansive Level 2 non-home charging infrastructure. This paper identifies candidate charging routes and uses freeway exits and highway intersections as approximate candidate charging locations, and consequently solves a set covering problem to minimize the number of charging stations. Results show that 290 Level 3 charging locations are required for the State of California based on the 2000 California Travel Survey and BEVs with 60 mile range. With this optimized station network, electric light duty vehicle miles travelled (VMT) can reach 92% and BEVs can be used by 98% of drivers. If BEVs with 100 or 200 mile range are used, 126 or 31 Level 3 charging locations are required, respectively. This study also assesses the temporal utilization of charging stations. Congestion at several stations suggests extra chargers are required. A reservation system can benefit both the BEV drivers and station operators by reducing the wait times, decreasing the extra chargers needed, and more evenly utilizing all the stations. Related policies are also discussed to better deploy fast charging stations. [ABSTRACT FROM AUTHOR]

The results of two recent vehicle emission studies are described in this paper, along with a statistical analysis of the changes in tailpipe emissions due to the use of ethanol that includes the results from these two studies in combination with results from other literature reports. The first study evaluates the effect of two low blend ethanol gasolines (E10, E20) on tailpipe and evaporative emissions from three multi-port fuel injection vehicles and one gasoline direct injection vehicle at two different test temperatures. The second study evaluates the differences in tailpipe emissions and fuel consumptions of paired flexible fuel and conventional gasoline vehicles operating on California RFG Phase 2 and/or E85 fuels at 20°C. The vehicles were tested over the four-phase FTP or UDDS and US06 driving cycles. Tailpipe emissions were characterized for criteria pollutants (CO, NO X , NMHC, NMOG), greenhouse gases (CO2, CH4, N2O), and a suite of unregulated emissions including important air toxics (benzene, 1,3-butadiene, formaldehyde, acetaldehyde, acrolein), and ozone reactivity. In the low blend ethanol study, evaporative emissions were quantified and characterized for NMHC. While contradicting, results can be seen among the various literature reports and with these two new studies, the statistical analyses of the aggregated data offers much clearer pictures of the changes in tailpipe emissions that may be expected using either low blend ethanol gasoline (E10) or E85. The results of the statistical analysis suggest that the use of E10 results in statistically significant decreases in CO emissions (−16%); statistically significant increases in emissions of NMHC (9%), NMOG (14%), acetaldehyde (108%), 1,3-butadiene (16%), and benzene (15%); and no statistically significant changes in NO X , CO2, CH4, N2O or formaldehyde emissions. The statistical analysis suggests that the use of E85 results in statistically significant decreases in emissions of NO X (−45%), NMHC (−48%), 1,3-butadiene (−77%), and benzene (−76%); statistically significant increases in emissions of formaldehyde (73%) and acetaldehyde (2540%), and no statistically significant change in CO, CO2, and NMOG emissions. [Copyright &y& Elsevier]

• We interview 10 facility managers and consultants to understand how they manage energy. • Smart meter data is used to benchmark energy use at multiple time scales. • Key Performance Indicators (KPIs) summarize multitiered energy performance. • KPIs are compared to perceptions of facility managers through a survey. • KPIs are used as an energy management system to identify building energy issues. Energy management information systems (EMIS) play a critical role in providing actionable insights into building operations, timely feedback, and—ultimately—large energy savings. Current EMIS technologies often focus on industrial applications or require large upfront investments and trained operators, therefore greatly limiting its penetration into existing buildings. This paper integrates methods from social, building, and data sciences to understand limitations of current EMIS systems and inform the design of a new Multitiered Energy Management Performance Indicators (MEMPI) framework for characterizing the energy performance of buildings. Specifically, we employed a mixed methods research approach in which we first conduct in-depth qualitative interviews of 10 facility managers and energy consultants. We utilize the insights from our interviews to inform the design of the MEMPI framework, which harnesses highly granular data from already installed advanced metering infrastructure (AMI) (i.e., smart meters). The MEMPI framework employs quantile regression to first benchmark the energy performance of buildings to each other and generate key performance indicators (KPIs). We apply the MEMPI framework to real data from 569 public school buildings in California and measure their energy performance across multiple time scales (e.g., daily, monthly, yearly). Finally, we conduct case studies to compare insights from the MEMPI framework to the perceptions of facility managers overseeing 8 schools through a mixed methods qualitative and quantitative post-interview survey. Results from the case study show that facility managers' perceptions of the performance of their schools were largely accurate, yet the poor energy performance from certain pieces of building equipment and operating schedules was overlooked by building managers. Overall, the MEMPI framework aims to bridge the gap between data-driven energy management models and qualitative domain knowledge held by facility managers to provide more comprehensive insights into the energy performance of buildings. [ABSTRACT FROM AUTHOR]