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The current generation of energy codes were born in the 1970s with the sole purpose of conserving energy in homes and buildings, and with no guidance surrounding renewable energy generation or grid integration for those structures. Over the intervening decades, that singular purpose has been complemented by increasing demands to reduce greenhouse gas emissions and to utilize a lower-carbon mix of fuel types. At the same time, the falling costs of renewable energy options, especially solar, have raised the importance of an optimizing calculus between renewable supply options and energy demand reduction options. The paper first reviews the framework for establishing the renewable/efficiency balance in California's Title 24-2019 Residential code. Based on additional analysis, the paper then presents a new framework that encompasses the range of U.S. climate zones and building types covered by the model energy codes, with a special focus on single family homes. This optimization framework is analyzed for its implications to update prescriptive, performance, and rating (such as the Energy Rating Index, or ERI) compliance paths in the model codes. The calculus is also examined for its application in determining impacts of renewable/efficiency combinations on electric grid stability. Additional topics covered include accounting for procuring onsite and offsite renewable energy and for measuring increases in building resiliency. The paper then offers recommendations for code developers by addressing the underlying code issues with regards to accounting, reporting, compliance, and enforcement. [ABSTRACT FROM AUTHOR]

Historical structures incur diverse challenges associated with energy consumption, specifically those surrounding opportunities for potential improvements. In the U.S., heating and cooling of spaces can account for up to half of all energy usage within a home. As a result, identification of cost-effective methods towards enhancing energy efficiency represents critical information for homeowners and businesses alike, and a measurable estimator of potential monetary investment and return. In this paper, a novel DC-powered picogrid is developed to support a local weather station adjacent to a residential home in order to optimize its energy consumption. Though regional meteorological data is readily available from numerous online cloud-services, in-situ environmental measurements afford more building-specific insights, ranging from wind direction and speed, humidity and dew-point levels, and UV and irradiance measurements. When coupled with on-site renewable energy generation such as solar and wind power, this weather data can drive real-time electrical management decisions (e.g., storing or expending battery energy, selling electricity to the grid, etc.), and also be leveraged for daily and weekly power consumption and generation forecasting. These findings illustrate the benefits of DC-powered designs, and the capability of low-cost sensors to improve residential energy administration. [ABSTRACT FROM AUTHOR]

Most larger buildings rely on one or more chillers operating on-demand to instantaneously meet building thermal loads as they occur. Unfortunately, the cost of electricity is highest during daytime, on-peak periods when building thermal loads are highest. Cool thermal energy storage (CTES) is a proven technology that enables decoupling the production of cooling from the coincident demand for cooling. CTES systems typically use either a single stratified chilled-water tank or a multiplicity of ice storage modules as a means of storing thermal energy during favorable chiller operating periods for later use to meet building cooling demands. For decades, building owners have benefited from CTES systems because of their ability to reduce utility costs by shifting the production of cooling from high cost on-peak periods to low cost off-peak periods. With increasing deployment of renewable energy generation, an additional application is provided for CTES related to alleviating problems associated with this intermittent source of electricity generation. As a technically mature and relatively inexpensive means of providing end-use electricity demand management, CTES has the potential to bridge mismatches between intermittent renewable generation and the utility aggregate demand for electricity. As we show in this paper, CTES is a technology that offers the potential to increase the deployment of renewable energy generation. This paper describes CTES design and control strategies that aim to more effectively use the generation of electricity from renewable energy resources. Specifically, one CTES control strategy discussed in this paper will charge the thermal storage system when renewable electricity generation is available and discharge storage to meet building cooling loads during periods of time when renewable energy is not available. This control strategy maximizes the fraction of the chiller's energy consumption met by electricity generated from wind or solar. A second CTES control strategy will maximize the net economic benefit of owning and operating a CTES system, based on equipment costs for both the CTES and the renewable generation systems and the operating cost of the net electric demand after wind or solar generation according to a time-of-use electricity rate structure. To illustrate the positive impact of CTES to enable increased penetration of renewable energy systems, an analysis is performed for a secondary school in the Los Angeles area. Simulated cooling loads for the prototypical school are based on the U.S. Department of Energy Commercial Reference Building Models (2011). To meet primary thermal loads, the secondary school employs air-cooled chillers and an ice storage system. The results show a trade-off between maximizing the use of renewable power and minimizing life-cycle cost, but a storage system designed to optimize the portion of chiller energy consumption met by renewable resources will be more costeffective and better at utilizing electricity from renewable energy resources than a system without thermal storage. These results suggest that widespread implementation of CTES systems may assist utilities in reaching their renewable penetration targets. [ABSTRACT FROM AUTHOR]

Data centers account for 1.5% of the energy consumption in the United States according to a recent report by the Environmental Protection Agency. These facilities' IT power and cooling requirements may increase in the future, especially with the rise of cloud computing and increased heat densities of servers. Since most utility power is generated by burning coal or fossil fuel, innovation is essential to meet the challenge of providing sustainable cooling and power for data centers. This paper proposes using Hydrothermal Energy for data centers whereby cooling and power are both sustainably generated. Coastal communities that have nearby cold and warm water resources are candidates for future data centers that can be operated completely off the grid while absorbing carbon from the atmosphere. The paper acknowledges that, while there are still challenges to be met in designing these facilities, Hydrothermal Net-Zero Energy data centers are within the realm of possibility. [ABSTRACT FROM AUTHOR]

This paper provides a methodology to evaluate end use options to reduce primary energy consumption and CO2 emissions associated with buildings. First, the paper discusses alternative energy efficiency metrics, their uses, and limitations. In particular, limitations of site energy and cost as meaningful societal metrics are reviewed, along with the challenges associated with alternative metrics such as full fuel cycle energy efficiency and CO2 emissions. In addition, the paper provides a methodology and example calculations for evaluating the site energy, full fuel cycle energy, and CO2 emissions of targeted direct use options. Results of the sample calculations show that natural gas water heaters can reduce primary energy consumption and CO2 emissions significantly compared to equivalent electric resistance water heaters. Variationsin calculated reductions occur depending on the fuels used to generate electricity and region selected for analysis. [ABSTRACT FROM AUTHOR]

Research into the development of fault detection and diagnosis (FDD) methods as applied to heating, ventilating, air-conditioning, and refrigerating equipment has been ongoing for over a decade, and several papers have been published. However, studies specifically related to large chillers have been few despite the importance of such equipment. The objective of this paper is to propose and illustrate a simple model-based FDD method for medium to large chillers that uses sensors available in most cooling plants, allows tuning of specific thresholds so as to attain the desired compromise between robustness and sensitivity, and has the potential to be automated and implemented online. Lacking actual field data of chillers operated under fault-free and faulty operation, the performance of the proposed FDD method is demonstrated with data generated from tests on a laboratory chiller in the framework of an earlier research study. This proposed FDD scheme is based on five important characteristic features (that have been identified from 15 variables evaluated) that allow six process faults to be identified (although two cannot be done uniquely). Since large chillers are not prepackaged as is unitary equipment, their design and assembly allow selecting different subsystems for a stipulated maximum cooling capacity. In such a case, selection of specific variables needed for FDD will be impacted by different faults, depending on several aspects unique to the chiller installation: the type of chiller load control (thermostatic expansion valve or inlet guide vane), specific choice of the relative heat exchanger size, and the load fraction at which the chiller is usually operated. Hence, it is likely that some customization would be needed to adapt the FDD thresholds and association rules for each chiller installation. Different options and challenges relevant to practical implementation of the proposed FDD method are discussed. [ABSTRACT FROM AUTHOR]

The challenge of the Science House at the Science Museum of Minnesota was to create habitable, cold-climate architecture that would result in a net zero energy building and to get it built in a ‘low bid’ environment. The design team used scientific evaluation to resolve design integration conflicts between functionality, aesthetics, and performance. The team significantly reduced annual energy consumption, beginning with expectations of use by the owner and architectural form and then by adding a renewable energy source. The defining question became, ‘How much building, with fixed program requirements, can we build and generate power for with the given budget?’ The resulting building uses passive solar design, daylighting, ground-source heat pumps, and photovoltaic (PV) panels as the major design strategies. This paper documents the predicted energy use and actual monitored performance, comparing to a calibrated DOE-2 model. It shows the extent of load reduction achieved with passive solar design. A challenge for getting to ‘real zero’ is the difference between expected performance and actual building performance. This paper illustrates how measured data are used to trace the causes to unexpected equipment performance, heat pump behavior, and off-line PV panels. Assumptions regarding occupancy and building use during the design phase often differ from their actual use; this makes operating a building for zero energy an additional challenge beyond just designing one. Overall, the actual building is exceeding the design goals, using on average 22,385 Btu/ft2·yr (0·71 kWh/m2·yr) annually and generating 30,864 Btu/ft2·yr (0.97 kWh/m2·yr) to result in a building that generates more energy than it uses. [ABSTRACT FROM AUTHOR]

The U.S. Army Corps of Engineers, in collaboration with the U.S. Department of Energy's (DOE) National Renewable Energy Laboratory (NREL), academia, and private sector subject matter experts, recently completed an energy study to evaluate potential site and source energy-use reduction in new Army buildings. The study was completed in response to the mandates for energy savings in federal buildings enacted by the U.S. Energy Independence and Security Act of 2007 (U.S. Congress 2007). The building types studied included an Unaccompanied Enlisted Personnel Housing (UEPH or barracks), a brigade headquarters (administrative building), a company operation facility, a maintenance facility, and a dining facility (DFAC). The study was conducted for representative locations in all 15 DOE identified climate zones in the United States with building designs adapted to these climatic conditions. This paper presents the results of the energy analysis for a typical Army dining facility. It discusses energy efficiency measures and combinations used to reduce both internal and external loads on the building and overall energy use. The largest load in a DFAC is the cooking, and the currently available best-in-class kitchen equipment is included in the final design. The potential site energy savings compared to the energy code range from 21% to 38%. The potential source energy savings compared to Commercial Building Energy Consumption Survey ranges from 37% to 42%. Additional savings may be obtained if an efficient cogeneration system is used and the building is considered as a part of the building cluster or community to fully utilize the energy from the cogeneration system. [ABSTRACT FROM AUTHOR]

The 2007 Energy Independence and Security Act (EISA) require that all new federal facilities be built fossil fuel free by 2030. This raises the bar considerably from the 2005 Energy Policy Act, which required federal facilities be built to achieve at least 30% energy savings over ASHRAE Standard 90.1 - 2004. On the trajectory towards the 2030 goal, buildings have to meet 65% decrease of source energy from the Commercial Building Energy Consumption Survey (CBECS) survey for the building type specified. The EISA requirement is not a comparison between a baseline and an energy efficient simulation, but a direct comparison with the actual results from the final simulation with the EISA target. This is not a delta percentage comparison; it includes total source energy and all the building loads must be addressed and not left out of the calculation as an unregulated portion of the building load. The result of the study was guidance on how to reach a 60-80% energy use reduction from Commercial Building Energy Consumption Study (CBECS). The 2005 Energy Policy Act requires that federal facilities be built to achieve at least a 30% energy savings over the 2004 ASHRAE Standard 90.1-2004. The Construction Engineering Research Laboratory (CERL) of the U.S. Army Corps of Engineers in collaboration with USACE HQ and Centers of Standardization for respective building types, subject matter expert (SME) contractors, and the DOE National Renewable Energy Laboratory (NREL) participated in a study to recommend design guides to achieve the Federal requirements for new buildings to be constructed under the Military Transformation Program. The building types included Unaccompanied Enlisted Personnel Housing or UEPH, administrative buildings (e.g., a brigade headquarters, and a company operation facility), a tactical equipment maintenance facility, and a dining facility. This paper presents the results of the energy analysis for the soldier barracks (UEPH). It provides the baseline building selected for the analysis and the modeling assumptions. As a result of a computer analysis using EnergyPlus, the target energy budgets are defined for all DOE 15 Climate Zones. Finally, a recommended set of energy efficient solutions for each climate zone is presented that shows the buildings limit as it approached net zero ready. It shows potential energy savings both on the building site and source energy when energy use reduction is considered on a building-by-building basis. It also shows further energy use reduction opportunities when energy improvements are made with each building considered as a part of the building cluster or community. [ABSTRACT FROM AUTHOR]

The Army is required by law (EPACT 2005, EISA 2007) to eliminate fossil fuel use in new and renovated facilities by 2030 and to reduce overall facility energy usage by 30% by 2015. Army policy is to achieve eight net zero energy pilot installations by 2020, 25 net zero energy installations by 2031, and for all installations to achieve net zero energy status by 2058. Achieving Net Zero Energy (NZE) will only be possible if an optimum mix of demand reduction and renewable sources are put in place at a community (installation) or building cluster scale. The Army operates what are essentially small campuses, or clusters of buildings on its installations. The US Department of Energy (DOE) is focused on the national grid scale or on individual buildings, while the commercial focus is on retrofits to individual buildings. There are only few case studies worldwide that address dynamics of energy systems at the community scale, and to date, there is a lack of tools to perform that task. The building stock at most US Army installations is complex and includes a mix of high and low energy use buildings. Energy use in these buildings varies due to the different military mission and requirements for each building, installation growth and expansion, and soldier deployment. Achieving net zero energy economically at such installations will require a seamless blend of energy conservation in individual buildings and building systems automation, utility management and control, and power delivery systems that have the capability to offer integration of on-site power generation (including renewable energy sources). This paper describes the Net Zero fossil fuel based energy optimization process and illustrates it with an example based on the results of study conducted for a cluster of buildings at Fort Irwin, CA. The integrated optimization process is being developed under the Army research and development project "Modeling Net Zero Installations - Energy (NZI-E)" and the International Energy Agency (IEA) Energy Conservation in Buildings and Community Systems (ECBCS) Annex 51. The process is stepped, beginning with the optimization of each building to achieve the most cost effective energy efficient optimization of building envelope and energy using systems. Then energy saving measures affecting the total building cluster are optimized taking advantages of the diversification between energy intensities, scheduling, and waste energy streams utilization. The energy demands of the resulting energy-use optimized cluster will require the minimum sized renewable energy system needed to make the building cluster Net Zero fossil fuel energy. [ABSTRACT FROM AUTHOR]

The Centre for Efficient and Renewable Energy in Buildings (CEREB) is a unique teaching, research and demonstration resource for the built environment hosting a number of renewable and intelligent energy solutions. CEREB has been developed in partnership between London South Bank, City and Kingston Universities with funding from the Higher Education Funding Council for England (HEFCE), London Development Agency (LDA) and M&E Sustainability. Located at roof level of the new London South Bank University teaching facility K2, the Centre houses evacuated solar tubes for domestic hot water, Photovoltaics (PV) providing electricity and ground source heat pumps providing heating for the entire building, and, through reverse cycle operation, provide cooling in the summer. The data from the monitoring systems is available via a web interface that allows it to be used for collaborative research, which gives the Centre an important international dimension. The data has been collected since May 2010 and its performance closely monitored to add invaluable resource for understanding how to design, operate and manage technologies for future low carbon buildings - both new build and retrofit. This paper reviews the performance of the building integrated renewables; solar thermal, PV and ground source heat pumps. It explores the designed building against real performance through data collected to date and identifies difficulties in integrating, commissioning and operating renewable technologies. [ABSTRACT FROM AUTHOR]

The developed world is increasingly energy constrained. There is an urgent need to reduce dependence on energy imports from unstable or unfriendly areas of the world and to increase the use of renewable energy technologies to meet our energy needs into the 21st century. In Europe the provision of a more secure energy supply is now the primary driver of energy supply and efficiency related policies. In the UK there are now explicit incentives for the use of technologies delivering heat from renewable sources: the Renewable Heat Incentive (RHI) and a mechanism for paying incentives for the installation of electricity generation equipment through the "Feed in Tariff". There is also a programme for the installation of energy efficiency measures in existing buildings which are initially funded by market packages, and these are then paid off over the following years from the reduced utility bills which the measures facilitate. There is also the European Union's Energy Performance of Buildings Directive, which has recently been updated and will require mandatory improvements to existing buildings as well as the setting of minimum standards of energy performance for new and existing buildings, with a target for all new buildings within the European Union to be "nearly zero carbon" by 2020. This paper will review the legal mechanisms being introduced to incentivise low or zero carbon technologies, or to require standards of building fabric performance that will reduce dependency on energy imports. It will discuss the introduction of new standards for energy efficient dwellings, and will also detail the various technologies supported or encouraged and will also demonstrate the benefits offered by the various schemes. While it will focus on the UK experience, it will also draw on experience from the various schemes adopted elsewhere in Europe. [ABSTRACT FROM AUTHOR]

The definition of a good indoor climate is important to the success of a passenger rail coach, not only because it will decide its energy consumption and thus influence its sustainability but also because good comfort for long journeys is essential. The intention is to use the results to optimize the control of the ventilation system to provide an indoor climate that passengers will find comfortable. The results of this study show how passengers' thermal comfort was affected by changing the supplied air conditions. This paper primary discusses and analyzes the simulation of the air flow and thermal patterns in a Subway station. Numerical simulation of a typical model is presented. Modifications were applied to the numerical model to show the improvement of the thermal comfort level. The pre-processor Gambit is used to create the geometric model with parametric features. Commercially available simulation software "Fluent 6.3" is incorporated to solve conservation of mass, momentum and energy in the processing of air distribution, and to analyze turbulence affection combined heat transfer on air distribution. In this thesis work, the socalled standard k-ε turbulence model, one of the most widespread turbulence models for industrial applications, was utilized. Basic parameters included in this work are air temperature, air velocity, relative humidity and turbulence parameters are used for numerical prediction of indoor air distribution. Measurements of air velocity, and temperature were undertaken in a plane perpindicular to the supply diffuser. These values were then compared to the obtained results from the simulated cases. The thermal comfort prediction through this work was based on the PMV (Predicted Mean Vote) model and the PPD (Percentage Predicted Dissatisfied) model, the PMV and PPD were estimated using Fanger's model. [ABSTRACT FROM AUTHOR]

Urban energy consumption plays an ever increasing role, as more than half of the world's population already lives in cities. Many municipalities have decided on ambitious goals to become climate neutral within the next decades, however, very limited experience is available of how demand can be significantly reduced on a city scale and what contributions local renewable energy sources can bring to cities. Many cities are starting to analyse their current CO2 emission levels, although continuous monitoring is very rarely available. In the current paper, two case studies were carried out in Southern Germany, which cover an entire medium sized city (Ludwigsburg) as well as a city quarter in Ostfildern. Although in both cases solar technologies have the highest potential for decentral renewable supply, the most significant contribution to cover the demand is by central power plants based on biomass. In the low energy building quarter of Ostfildern, a biomass cogeneration plant covers 80% of the heating and 50% of the electricity consumption. The remaining electricity consumption could be provided by photovoltaics on easily available roof tops, however, less than 5% of consumption is currently covered by installed PV systems. The studies show that the main challenge is to reduce emissions caused by individuals in their buildings and transport activities and to implement solar technologies in buildings. The municipalities themselves can be front-runners with highly efficient buildings and central renewable plants constructed by their municipal energy supply companies. However, they are directly responsible for less than 5% of all urban emissions and their energy supply companies only provide a limited fraction of households with heat and electricity. [ABSTRACT FROM AUTHOR]

Data Centers are an ever increasing user of energy in our economy. While the performance per watt of our IT equipment continues to increase exponentially, this energy performance improvement is still outstripped by increasing demand. Because of this, the efficiency of data centers must continue to improve. Beyond just efficiency, many data centers now are working towards reuse of their waste energy in other areas in the data center or on the site or campus. How to account for this, through metrics and measurements, is the topic of this paper. The Energy Reuse Effectiveness metric or ERE is discussed; both the development and application of the metric are looked at in detail. The use of ERE in conjunction with PUE (Power Usage Effectiveness) is also considered. [ABSTRACT FROM AUTHOR]

Sustainable on-site cooling-heating-power (CHP) systems for large multibuilding projects require a simplified design and implementation approach from conventionally designed mini-utility-type CHP systems employing large volume/footprint, costly, high thermal mass heat-recovery- steam-generators, and 24/7 stationary engineers. This paper demonstrates the use of prefabricated, skid-mounted hybrid steam generators with internal headers, fully integrated with low pressure drop heat extraction coils located in the gas turbine exhaust and employing environmentally benign heat transfer fluids. The proposed thermal tracking integrated CHP gas cooling system includes close-coupled plate-and-frame heat exchangers, pumps, and self-regulating controls, interconnected via a closed, low-pressure, nonvolatile recirculation loop capable of efficient year-round heat transfer to on-demand HVAC&R building heat sinks, including absorption chillers. Available waste heat is transferred directly to a gas turbine exhaust, extraction heat exchanger, interconnected to a recirculating, closed-circuit, nonvolatile, low-pressure heat transfer fluid loop. Available waste heat is cascaded to serve multi-building space cooling, heating, and domestic hot water loads, which permits maintaining high log-mean-temperature-differentials at the subject extraction coil, significantly lowering gas turbine back-pressure, and permitting significant life-cycle cost savings. These benefits were demonstrated during a recent, comparative CHP study ofa 3.5 MW gas turbine installation at a central California university campus. [ABSTRACT FROM AUTHOR]

This paper describes a model for investigating pure conduction heat transfer through the ground and its influence on room air temperature. The differential equation of energy conservation for each node of the building envelope was discretized by using the finite-difference method, a uniform grid, and a fully implicit scheme. In order to investigate the use of simpler models for reducing computer run time of yearly building simulation programs, we considered three approaches. First, a one-dimensional model for the ground is adopted and then compared with two-dimensional and three-dimensional models. Also considered is lumped approach for a building, which is externally subjected to convection, solar radiation, long-wave radiation, and infiltration. Internally, interchange long-wave radiation and convection are considered. People, equipment, and lighting are also considered in formulation as internal energy gain. In conclusion, we show that it may be important to take into account the use of three-dimensional ground heat transfer modeling in building simulation programs for thermal load calculation and thermal comfort evaluations of low-rise buildings. [ABSTRACT FROM AUTHOR]

This paper summarizes efforts to identify economically viable strategies to reduce HVAC-related energy use while improving the indoor air quality for a public zoo facility that houses primates and large cats. The primary focus of energy conservation strategies/or the facility centered on use of air- to-air energy recovery devices. Computer simulations, validated with experimental data from the facility, were used to estimate energy savings for alternative energy conservation strategies. The findings suggest that more than 80% of the heating energy and 45% of the cooling energy can be saved by implementing air-to-air energy recovery equipment coupled with alternative temperature control settings. An extension of the energy analysis to environmental impacts suggests that up to 73 tons of CO2 emissions can he saved annually by implementing the equipment and operating strategies identified in this study. [ABSTRACT FROM AUTHOR]