Image Courtesy of Harvestar 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 FoundOctober Heat Solar Hot Water Production 2012 - Low Load Home ExchangerOutput Well 800,000 PluggedUnder100% 90% 700,000 Expectation 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 HotElectrical Water Electricity Cost Bills $70.00 $35.00 $60.00$30.00 $50.00$25.00 $40.00$20.00 $30.00$15.00 $20.00$10.00 $5.00 $10.00 $0.00 $0.00 Jan Feb March April May June July Aug Sept Oct Nov Dec With SHW Without SHW •• ComparedWhat about toa home an identical with a higher home DHW with Load? no SHW 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 Installed $80.00 $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 ? .