FEMP Support to Central Solar Hot Water Design Guide January 28, 2010 Dallas TX Andy Walker PhD PE Vickie Healey National Renewable Energy Laboratory Anne Sprunt-Crawley US Department of Energy Federal Energy Management Program Goals and Mandates: Energy Independence and Security Act (EISA 2007): Section 523. “if lifecycle cost-effective not less than 30 percent of the hot water demand for each new Federal building or major renovation be met by solar hot water heaters.''. Section 441 changes the term for life-cycle-cost analysis from 25 years to 40 years in order to favor long-payback renewable energy measures. Section 431 energy consumption per gross square foot of the Federal buildings of the agency to be reduced 30% from a 2003 baseline by the year 2015. Section 323 GSA to include renewable energy in new-building prospectus and lease requirements. Section 433 fossil consumption of new buildings is reduced by a scale that escalates from 55% less in 2010 to 100% less (which would require on-site renewable energy systems) in 2030. Executive Order 13514 set goals to reduce greenhouse gases, which can be accomplished partly through on-site solar systems. EPAct 2005 requires renewable electricity consumption by the federal government of at least 7.5% in 2013 and thereafter. Solar water heating systems would not contribute to this electric goal, but would contribute to the executive order requirement that half of this renewable energy be new (installed after 1999), thus making it easier to meet the electric goal with pre-1999 renewables. FEMP Solar Hot Water Activities • Guidance • Support US Army with Central Solar Hot Water System Design Guide • Guidance regarding EISA 2007 SEC. 523. (30% solar hot water) • Publications: • Federal Technology Alert Solar Water Heating • Low Cost Solar Hot Water Systems • Solar Water Heating Resource Page on WBDG.ORG • Project Assistance • Screening for Opportunities • Feasibility Studies • Procurement Specifications • Alternative Financing (Energy Savings Performance Contracting, etc) • Measurement and Verification FEMP Contributions to Central Solar Hot Water System Design Guide • Diagrams of System Types • Simple Evaluation Procedure based on GIS Resource Data, with example. • List of required GIS Data for all Army locations. • GIS Maps of Cost of Delivered Energy ($/kWh, $/therm) for $50, $75, and $150/sf Solar System Cost • Case Studies of Residential, Commercial, and Industrial Solar Hot Water Systems. System Schematic Diagrams From FEMP training material. Simple Evaluation Procedure Estimate Daily Water Heating Load Determine Solar Resource Calculate Solar System Size – meet load on sunniest day – undersize rather than oversize Calculate Annual Energy Savings Calculate Annual Cost Savings Estimate System Cost Calculate Savings-to-Investment Ratio and Simple Payback Period Daily Water Heating Energy Load L = MC (Thot - T cold) L = Daily Hot Water Energy Load (kWh/day) M= mass of water per day (kg/day), 3.785 kg/gallon C = specific heat of water= 0.001167 kWh/kg°C Thot= hot water delivery temperature (°C), often 50 ° C = 120 ° F Tcold = cold water temperature (° C), often 13 ° C = 55 ° F Hot Water Use estimates for new buildings • New water Typical Hot Water consumption Usage: standards Dormitory 13 gal/day/person Barracks 10 gal/day/person • New technology Motel 15 gal/day/unit Hospital 18 gal/day/bed • Army Modeling: Office 1 gal/day/person – Admin 0.54 btu/sf/hr Food Service 1 to 2.4 gal/meal – Barracks 1.2 btu/sf/hr Residence 30 gal/day/person – Child Devl Cntr 0.27 btu/sf/hr School 1.8 gal/day/student – Dining Hall 1.56 btu/sf/hr Solar Energy Resource Collectors should face south (in northern hemisphere) Tilt Angle=latitude maximizes annual gain (lat+15°for winter, lat-15° for summer) Location I Max I Ave (kWh/m2/day) Anchorage, AK 4.6 3.0 Austin, TX 6.3 5.3 Boston, MA 5.6 4.6 Chicago, IL 5.7 4.4 Data for all military sites Cleveland, OH 5.6 4.1 has been compiled by Denver, CO 6.1 5.5 NREL. Fargo, ND 6.5 4.6 For COMPLETE data on Honolulu, HI 6.5 5.5 hundreds of sites, check Jacksonville, FL 6.1 4.9 out www.nrel.gov Sacramento, CA 7.2 5.5 9 San Diego, CA 6.5 5.7 Seattle, WA 5.7 3.7 Solar Water Heating System Size and Delivery Solar Water System Size Annual Energy Savings Ac = L . Es = Ac Iave ηsolar365 (ηsolar Imax) ηboiler I ave = average solar radiation Ac = collector area (m2) (kWh/m2/day) L = Daily Load (kWh/day) ηboiler = auxiliary heater efficiency ηsolar= efficiency of solar gas 0.57 0.43 to 0.86, assume system (typically 0.40) electric 0.77 to 0.97, assume 0.88 I max = maximum daily solar heat pump assume radiation (kWh/m2/day) 2.0 propane 0.42 to 0.86, assume 0.57 oil 0.51 to 0.66, assume What efficiency to use for new construction? Energy Factors from the Gas Appliance Manufacturer’s Association [http://www.ahrinet.org/Content/CommercialWaterHeaters_593.aspx]: includes stand-by losses from the storage tank, which could not be saved by the solar water heating system. Conventional Gas Storage: 0.43 to 0.86, assume 0.60 High Efficiency Gas Storage: assume 0.65 Condensing Gas Storage: assume 0.86 Demand gas (no storage tank): assume 0.82 Conventional Oil-Fired with Storage: 0.51 to 0.66, assume 0.55 Conventional Oil-fired Storage: assume 0.55 Conventional Propane-Fired with Storage: 0.42 to 0.86 assume 0.57 Conventional Electric With Storage: 0.77 to 0.97 assume 0.90 High Efficiency Electric With Storage: assume 0.95 Electric heat pump water heater: assume 2.20 Solar Water Heating System Cost and Savings Solar System Cost Annual Cost C = csolar Ac Savings S = Es C e C = Installed Cost of Solar System ($) S = annual cost savings csolar = per-unit-area cost of ($/year) installed solar system Ce = cost of auxiliary ($/m2), typically energy $400/ m2 for large system typically: $1000/m2 for small Electricity $0.084/kWh systems Natural Gas $0.040/kWh Propane $0.040/kWh $750/ m2 might be Oil $0.025/kWh Installed Cost – Single, small system $100-250/ft2 – Large central system $30-80/ft2 – Swimming Pool system $80/ft2 Source: Graphs compiled by Dylan Cutler, NREL; RS Means “Green Building Project Planning and Cost Estimating, FCI Phoenix project Solar Water Heating System Cost Effectiveness Savings-to-Investment Simple Payback Ratio Period SIR = S*pwf / C SPB = C / S project is cost effective if SIR>1. pwf = present worth factor for future savings stream, = 24 years for 40 year lifetime and 3% real discount rate (specified by NIST). Example: 4 person residence in Cleveland against electricity M=4person*40gal/person/day*3.785 kg/gal=606 kg/day L=MC(Thot-Tcold) =606 kg/day*0.001167kWh/kgC*(50C-18C) =22.6 kWh/day For Cleveland OH, Imax = 5,6 and I ave = 4.1 kWh/m2/day Ac = L / (ηsolar Imax) = 22.6 kWh/day / (0.4 * 5.6 kWh/m2/day) =10 m2 Es = Ac Iave ηsolar 365/ ηboiler = 10 m2 * 4.1 kWh/m2.day * 0.4 * 365days/year / 0.88 = 6,802 kWh/year C = csolar Ac = $1000/m2 * 10 m2 = $10,000 S = Es Ce = 6,802 kWh/year * $0.084/kWh = $571/year SIR = S*pwf / C = $571/year * 24 years / $10,000 = 1.37 SO IT IS COST EFFECTIVE! Payback period = 18 years. Case Study: USCG Housing, Honolulu HI 62 units installed 1998 Active (pumped), Direct systems Average cost $4,000 per system 80 sf per system $800 per system HECO rebate Energy Savings of 3,008 kWh/year Demand Savings of 1.62 kW/house Solar Fraction 74% Efficiency 24% USCG Housing, Honolulu HI Solar Water Heating Example: Social Security Administration Building (Philadelphia, PA) • Reheats recirculation loop • 180 evacuated heat-pipe collector tubes • 27 m2 gross area • Cost $37,500 • Delivers 38 GJ (36 million Btu)/year • Installed 2004 Solar Water Heating Example: Social Security Administration Building (Philadelphia, PA) 6000 Energy/Month (MJ/month) 4000 2000 0 Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Alternative Financing Example: Phoenix Federal Correctional Institution 17,040 square feet of parabolic trough collectors 23,000 gallon storage tank Installed cost of $650,000 Delivered 1,161,803 kWh in 1999 (87.1% of the water heating load). Saved $77,805 in 1999 Utility Costs. Financed, Installed and Operated under Energy Savings Performance Contract with Industrial Solar Technology, Inc. The prison pays IST for energy delivered at a rate equal to 90% of 26 the utility rate (10% guaranteed savings), over 20 years. High Temperature Example: Phoenix Federal Correctional Institution Month Energy and Cost Savings 500 400 Total Delivered Heat (million Btu) 300 1999 2000 2001 2002 200 2003 100 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Resources and References Federal Technology Alert “Solar Water Heating” http://www1.eere.energy.gov/femp/pdfs/FTA_solwat_heat.pdf Federal Technology Alert “Parabolic Trough Solar Water Heating” “http://www1.eere.energy.gov/femp/pdfs/FTA_para_trough.pdf Low-Cost Solar Water Heating (available soon) Federal Energy Management Program Maps http://www.nrel.gov/gis/femp.html Technical Assistance Detailed Case Study “A Solar Success Story at Moanalua Terrace” http://www1.eere.energy.gov/femp/pdfs/25377.pdf “Solar Water Heating: Using the Sun to Heat Water Makes Sense in any Climate” http://220.127.116.11/femp/pdfs/26013.pdf Whole Building Design Guide Resource Page “Solar Water Heating” 28 http://www.wbdg.org/resources/swheating.php?r=minimize_consumption Thank You!