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    Better Buildings By Design 2013
Building the Renewable Energy Ready Home
Solar Thermal Lessons Learned and Results

       Doug Merrill, Sunward Systems
                Doug Merrill
• 20 + years of manufacturing experience
  – General Electric
  – Husky Injection Molding
  – Consulting, Teaching
• 5 Years of Solar Hot Water experience
  – Consulting (supply chain)
  – Monitoring development
  – Principal in Sunward Systems
   Solar Hot Water System Advantages

• Reduces need for electricity or fossil fuel

• Saves money

• Easy to integrate
 Comparison of Energy Standards




DHW Heating is Typically Second Highest Building Load
           Why Solar Hot Water ?
• Saves money…a good investment
  – ROI is good for most any fuel
     •   Propane       9%
     •   Oil           7%
     •   Electricity   7%
     •   Gas           3%
  – Few alternatives in New England
     • Heat pump & geothermal economics not great
     • Wood is good, but labor intensive in the summer
               Solar Hot Water Siting
• Building Compromises: Collector orientation
   – Collectors facing true South are ideal
       • Fall-off in production is gradual…up to 45 from South OK
       • Makes ‘tracking’ unnecessary
   – Collector ‘tilt’ is also a gradual falloff…nominal is angle=latitude
       • Steeper is better (up to 5-10 degrees)
       • Helps boost production in winter
       • Assists in snow shedding
   – Shading
       •   Partial shading OK- do analysis!
       •   Small feature shading (sticks, power lines) not a factor
       •   Want at least 5-6 hours of direct sunlight a day
       •   For new home sites…consider the landscaping choices and how they will look in
           10 years
       Roof Design Considerations
• Orientation & pitch determine if roof is viable
• 50-80 square feet of space
• Check ‘border’ around collectors for fire access
• No penetrations or features within space
• Design for 6 lbs/ft2 more than code
• Access to attic makes installation easier
• Slate & ceramic roofs are a challenge!
      Integrating a SHW System
• Ground mount options
  – Usually lower, so watch for shading
  – Tubing & wiring run in trenches
  – Easier to service & clear snow
  – Typically more flexible, slightly more expensive
       Integrating a SHW System
• Integration with backup DHW system
   – SHW acts as a ‘pre-heater’
   – Not cost-effective to produce 100% solar
     in New England
• Fuel agnostic…works with gas, oil,
  electricity
• Functions most effectively with storage
  type heater
• Indirect fired systems are much less
  efficient than their ratings (due to
  summer cycling)
         Mechanical Integration
• Integrated tank/heater/heat exchangers
  available, but force many compromises
  – Lower efficiency (less storage, mixing)
  – Higher lifetime costs
  – Less space required
• Review total rise of system versus pump spec’s
• Mixing valve is necessary
  – Preferably on the output of the backup system
  – This is consistent with current building codes in most
    places
         Minimize DHW Load!
• Insulate hot water piping throughout the
  home
• Minimize hot water piping run length
• Install low flow shower heads and aerators
 Water & Space Heating Readiness
• Much larger collector footprint required
  – (roughly 10% of heated area)
• Radiant heating with high thermal mass ideal
• Maximize passive heating to minimize solar
  collection system needs
• Must address summer heat over-production
  – Mechanically
  – Physically
  – Heat Dump
  Benefits of building Solar-Ready
• Cost to contractor/homeowner minimal ~$150
• Some design compromises may be required

• System effectiveness far higher
• Installation cost savings about $600
• Builder can finish home before customer
  makes final installation decision
   Lessons Learned: Performance Data

• 500+ Systems sold
• A dozen monitored
• Two case studies….
  – Low use passive home
  – High use passive home
   Lessons Learned – Case Study
• Home occupied 2011
• Typically 2 residents
• Low hot water usage
  – 38 gallons per day
         Passive House Solar Hot Water Data
                                                                                               Found Heat
                                                                                                   October
                      Solar Hot Water Production 2012 - Low Load Home                           Exchanger
                                                                                                 Output Well
800,000                                                                                               100%
                                                                                                 Plugged
                                                                                                    Under
700,000
                                                                                                 Expectation
                                                                                                      90%


                                                                                                      80%
600,000
                                                                                                      70%

500,000
                                                                                                      60%


400,000                                                                                               50%


                                                                                                      40%
300,000

                                                                                                      30%
200,000
                                                                                                      20%

100,000
                                                                                                      10%


     -                                                                                                0%
          Jan   Feb     Mar   Apr     May     June    July     Aug          Sept   Oct   Nov    Dec

                                    DHW BTU     SHW BTU      % from Solar
   Passive House Solar Hot Water
• Low Load Home Conclusions
   – 70% of the 2012 DHW energy needs have come
     from solar
                           2012 Hot Water Electricity Bills
                                  Electrical Cost
         $70.00
           $35.00
         $60.00
           $30.00
         $50.00
           $25.00
           $20.00
         $40.00
           $15.00
         $30.00
           $10.00
         $20.00
             $5.00
         $10.00
             $0.00
          $0.00
                     Jan   Feb March April May June July Aug Sept Oct   Nov Dec

                                       With SHW    Without SHW



•• Compared tohome with a higher DHW Load?SHW
   What about a an identical home with no
    Passive Home SHW Study #2
• 250’ South of home #1
• SHW system installed in July 2012
• Monitoring installed in August 2012
  – Data is fresh!
• 3-5 Residents
• Very high DHW use
  – 100 Gallons/Day
        Passive Home SHW Study #2
                                Daily DHW Energy Usage Sept 2012
90000

80000

70000

60000

50000

40000

30000

20000

10000

    0
        9/6 9/7 9/8 9/9 9/10 9/11 9/12 9/13 9/14 9/15 9/16 9/17 9/18 9/19 9/20 9/21 9/22 9/23 9/24 9/25 9/26 9/27 9/28 9/29 9/30

                                                                DHW BTU             SHW BTU


 • 81% of DHW energy from solar
        – (Compares with 86% on low use home)
 • 2X Energy produced (45KBTU per day!)
          Passive Home SHW Study #2
                                              Electric Cost
$100.00


 $90.00                                                               SHW System
 $80.00
                                                                        Installed

 $70.00


 $60.00


 $50.00


 $40.00


 $30.00


 $20.00


 $10.00


    $-
          Mar-12   Apr-12   May-12   Jun-12      Jul-12   Aug-12   Sep-12   Oct-12   Nov-12   Dec-12



  • Savings of $40 - $70 per month
Questions ?

				
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posted:7/24/2013
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