1、496 2010 ASHRAEABSTRACTThis paper provides a methodology to evaluate end useoptions to reduce primary energy consumption and CO2emis-sions associated with buildings. First, the paper discussesalternative energy efficiency metrics, their uses, and limita-tions. In particular, limitations of site ener
2、gy and cost as mean-ingful societal metrics are reviewed, along with the challengesassociated with alternative metrics such as full fuel cycleenergy efficiency and CO2emissions. In addition, the paperprovides a methodology and example calculations for evalu-ating the site energy, full fuel cycle ene
3、rgy, and CO2emissionsof targeted direct use options. Results of the sample calcu-lations show that natural gas water heaters can reduce pri-mary energy consumption and CO2emissions significantlycompared to equivalent electric resistance water heaters. Vari-ations in calculated reductions occur depen
4、ding on the fuelsused to generate electricity and region selected for analysis.INTRODUCTIONBuildings consume nearly 40% of the primary energyresources and 74% of the electricity generated each year in theUnited States (DOE 2008). Homes and commercial busi-nesses have been growing contributors to CO2
5、emissions forthe last 15 yearsa trend that is projected to continue for thenext two decades. As shown in Figures 1 and 2, the increasingCO2emissions of residential and commercial buildings isbeing driven primarily by growing consumption of electricity,including generation losses (DOE 2008, 2009). Mu
6、ch of theincreased carbon impact from residential and commercialelectricity use (52% since 1990) comes from power plants andthe relatively inefficient “full fuel cycle” of production anddelivery of electricity to the buildings. Aggregate CO2emis-sions from natural gas consumption in U.S. buildings h
7、aveincreased by 13% since 1990. Emissions due to natural gasconsumption in residential buildings are projected to remainflat through 2030 despite growth in the number of gas custom-ers, while emissions from commercial buildings are projectedto increase by 15%. During the same period, emissions frome
8、lectricity use in residential buildings are projected to increaseby 9%, while emissions from commercial buildings areprojected to increase by 26% (DOE 2009).Natural gas is used predominantly for heating, water heat-ing, and cooking. Each of these markets has seen significantimprovements in energy ef
9、ficiency in the past two decades,with gas use per building continuing a steady decline thatstarted in the 1980s (Joutz 2007). For instance, in the residen-tial market, households decreased consumption of natural gasFigure 1 Gas and Electric CO2Emission Trends in Resi-dential and Commercial Buildings
10、.Methodology to Evaluate End Use Options to Reduce CO2Emissions from BuildingsNeil P. Leslie, PE Marek CzachorskiMember ASHRAE Member ASHRAEYanjie Yang Ron EdelsteinN.P. Leslie is a research manager, M. Czachorski is an institute engineer, and Y. Yang is a principal engineer in the End Use Solutions
11、 Sectorat Gas Technology Institute, Des Plaines, IL. R. Edelstein is director of regulatory and government relations at Gas Technology Institute, DesPlaines, IL.OR-10-052 2010, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Trans
12、actions 2010, Vol. 116, Part 1. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAEs prior written permission. ASHRAE Transactions 497by 1% annually between 1980 and 2000 and by 2.2% annuallybetween 2000 and 20
13、06.On the other hand, electricity consumption per buildinghas increased as a result of higher market penetration of cool-ing and significant increases in plug loads such as computers,TVs, and electronics. Future gains in electric appliance effi-ciency are projected to be offset by new applications f
14、or elec-tricity as well as market growth. Overall, electricity use perbuilding is projected to grow by 1.1% per year for residentialbuildings and 1.9% per year for commercial buildings through2030 (EPRI 2009). CO2emissions attributed to the electricity sector arecaused by fossil fuel and biomass gen
15、eration (DOE 2008).Hydropower, wind, and solar generation do not add materiallyto the nations CO2emissions once construction is completed.Biomas is considered a renewable resource with net CO2emis-sions a function of energy returned on energy invested toobtain the biomass factors that are beyond the
16、 scope of thispaper. Coal is the most significant contributor to buildingsCO2emissions due to its high carbon content compared to oil,propane, and natural gas (EIA 2009a). In 2007, coal provided49% of total electricity generation in the U.S., while the elec-tric power sector accounted for 93% of all
17、 coal consumption(DOE 2008). Natural gas use in power plants has also beenincreasing significantly since 1990, and accounted for 20% ofelectricity generation in 2007. Natural gas use in power plantsis now higher than residential, commercial, or industrial natu-ral gas consumption. Emissions associat
18、ed with the extraction,processing, and transportation of fossil fuels, nuclear fuel, andbiomass prior to combustion are also important to consider asthey can add anywhere from 3 to 20% to the overall CO2emis-sions from buildings depending on energy source and appli-cation (Deru 2007).These trends in
19、dicate an opportunity for future energyefficiency and CO2emission reduction initiatives that leverageimprovements in gas appliance efficiency with cost-effectivedirect gas use options that reduce resistance heat electricityconsumption in space heating, water heating, cooking, andclothes drying.In th
20、is paper, calculation methodologies and samplecalculations for site energy efficiency, full fuel cycle energyefficiency, and CO2emissions associated with different tech-nology options in buildings are discussed. First, site energyand full fuel cycle efficiency methods are described, with anemphasis
21、on their uses and limitations. Then, approaches tocalculating full fuel cycle CO2emissions due to buildings areidentified. Finally, sample calculations of CO2emissions arepresented for a residential water heater comparison showingthe impact of different calculation approaches on results.METHODOLOGYG
22、overnment sources provided most of the data for calcu-lating energy conversion and emission factors for electricityand fossil fuel use attributable to buildings. Government datasources included the Energy Information Agency (EIA) of theDepartment of Energy (DOE), the Environmental ProtectionAgency (
23、EPA), Argonne National Laboratory (ANL), Na-tional Renewable Energy Laboratory (NREL), and the Cali-fornia Energy Commission (CEC). Additional informationwas obtained from publicly available reports and presenta-tions that were supplemented by conversations with experts inthe field. These discussion
24、s were especially helpful for hydro-power efficiency estimates and environmental impacts.Government Data SourcesEIA Annual Energy Review. This database uses anextensive set of data surveys and estimation techniques todevelop data series and graphical information on energysupply and consumption in th
25、e U.S. (DOE 2008). The data-base provides overview information for total energy, petro-leum, natural gas, coal, and electricity and also showsextensive details of the supply and consumption componentsby fuel type and market sector. Greenhouse gas emissionsinformation includes statistics on CO2, CH4,
26、 N2O, SO2, andNOx.EIA-906/920 and EIA-923 databases. These databasesprovide monthly and annual data on generation and fuelconsumption at the power plant and prime mover level (EIA2009b). This supplemented information provided in the EPAeGRID database to establish power plant fuel mix.EPA eGRID2007 v
27、1.1Database. This spreadsheet data-base and accompanying reference material provides detailedand aggregate data on electric power plant emissions for theyears 2004 and 2005 (EPA 2009a). Data is reported for all U.S.power plants that provide power to the electric grid and reportdata to the U.S. gover
28、nment. The data is aggregated at electricgenerating company, parent company, power control area,state, eGRID sub-region, National Electric Reliability Coun-cil (NERC) region, and national levels. The eGRID emissionsdatabase includes data for NOx, SO2, CO2, Hg, CH4, and N2Oair emissions from annual e
29、lectric power generation. The data-base also includes heat rates and the percentage of powersupplied by coal, oil, natural gas, nuclear, hydro, and otherrenewable sources. This generation mix data is useful toFigure 2 Energy use trends 19502007 in residential andcommercial buildings (DOE 2008). 2010
30、, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions 2010, Vol. 116, Part 1. For personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAEs
31、prior written permission. 498 ASHRAE Transactionsestimate source energy conversion factors at state, regional,and national levels. In addition, a state level grid gross lossfactor is provided that can be used to estimate electric distri-bution efficiency.EPA AP-42. This database provides representat
32、ive valuesfor quantities of pollutants released into the atmospherecaused by an activity releasing the pollutant (EPA 1995). It isuseful for estimating source emission factors for natural gas,propane, and oil stationary combustion as well as pre-combus-tion factors for electric power generation. In
33、addition to CO2,the database includes EPA criteria pollutant emission factorsas well as particulate emission factors. EPA AP 42, ExternalCombustion Sources, is a set of reports documenting air emis-sion factors for external combustion of natural gas, fuel oil,and liquefied petroleum gas/propane (EPA
34、 2008a). This set ofdata is useful in defining emissions from building energy usesother than electricity. EPA AP 42, Stationary Internal Com-bustion Sources, is a set of reports documenting air emissionfactors for stationary internal combustion engines using natu-ral gas, diesel, and gasoline (EPA 2
35、008b). The reports containdata supporting calculation of emissions factors for extraction,processing, and transportation of fuels for combustion inbuildings and power plants.EPA National Energy Performance Rating System.This methodology provides performance ratings for commer-cial buildings (EPA 200
36、8c). It provides a benchmark that helpsenergy managers to assess how efficiently their buildings useenergy relative to similar buildings nationwide. To determinethe performance of a facility, EPA compares its source energyuse to other, similar types of facilities for 12 different commer-cial buildin
37、g space types. Source energy use includes energyconsumed at the site as well as energy used in generation andtransmission (but not extraction, processing, or transporta-tion). DOE Commercial Building Energy ConsumptionSurvey (CBECS) data is the basis for most of the rating calcu-lations (DOE 2005).
38、The EPA rating system includes spacetypes representing 60% of U.S.commercial building squarefootage.NREL Report TP-550-38617. This report providespower generation state level data on use of bituminous, subbi-tuminous, and lignite coal (Deru 2007). It also lists compositesource energy factors for ext
39、raction, processing, and deliveryfor major fuel types. These data are useful in calculatingenergy factors for fuels prior to combustion in buildings andpower plants.NREL U.S. LCI database. This database provides acradle-to-grave accounting of the energy and material flowsinto and out of the environm
40、ent that are associated withproduction and use of various fuels and electricity (NREL2004). The database provides supplemental information tocalculate source energy factors for fuels being delivered to thepoint of use.NREL Life Cycle Assessment of Coal-fired PowerProduction. This report provides dat
41、a useful in estimatingenergy used for extraction, processing, and transportation ofcoal delivered to power plants (NREL 1999).California Title 24, Part 6. Californias Energy Effi-ciency Standards for Residential and Nonresidential Build-ings contain administrative regulations relating to the energyb
42、uilding regulations in Title 24, Part 6, of the California Codeof Regulations (CEC 2008a). The building standards apply toall residential and nonresidential buildings. Until 2005, theCalifornia new building energy efficiency standard provisionsstipulated a simplified source energy conversion factor
43、of 3.0(10 239 Btu/kWh) for purchased electricity, with no adjust-ment required for other purchased fuels, when comparing thebudgeted building to the proposed building under the perfor-mance compliance approach (CEC 2001). This value repre-sented a net source energy conversion factor when comparingel
44、ectricity consumption to natural gas, oil, or propane con-sumption. Starting in 2005, the California standard changedthe conversion factor methodology to time dependent valua-tion (TDV). TDV adjusts source energy consumption of threecategories (purchased electricity, natural gas, and all otherdeplet
45、able resources) for each building type covered in thestandard (CEC 2008a). Building-specific TDV values in eachof the 16 California climate zones change hourly by time ofday and day of week throughout the year, and include variablelife cycle evaluation periods for non-residential buildings(CEC 2008b
46、). Hourly CO2emission rates are calculated onlyfor two regions: Northern California and Southern California.This methodology is more detailed than the previous approachto accommodate not only annual energy efficiency options,but also time of day and seasonal options such as energy stor-age to offset
47、 peak cooling demand. It involves application ofhourly simulation tools when choosing the performance com-pliance path rather than the prescriptive path.California is also exploring a methodology to estimate themarginal CO2emissions from building energy use (Mahone2009). This methodology uses the ho
48、urly load profile of thebuilding to estimate coincident hourly CO2emissions basedon a simulated GHG emissions profile of Californias electric-ity generation. It is intended to account for marginal CO2emissions and permit improved decision making on compet-ing energy efficiency alternatives.Supplemen
49、tal Data SourcesASHRAE Building Energy Labeling Program. Thisreport of an ASHRAE Presidential Ad-Hoc Committeeincludes background information, recommendations, and pro-tocols for an energy efficiency rating that facilitates the com-parison of commercial buildings performance (ASHRAE2008). The recommended rating methodology would provideAsset ratings of new building designs and Operational ratingsfor existing buildings based on source energy consumptionsimilar to the EPA National Energy Performance Rating Sys-tem.Hydropower Generation Efficiency. Information onhydropower technolog
