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					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://205.254.148.40/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!

				
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