Residential Solar Thermal System: Salt Lake City, Utah

1. Residential Solar Thermal System: Salt Lake City, Utah Bradley Godshalk: Foundation and Architectural Abraham Ruper: Structural Kevin Molocznik: Fluid Systems Charles Borrello: Building Thermal Systems Mark Vaughn: Solar Thermal Systems

2. PDR Agenda • Introduction • Floor plan layout • House elevation drawings • Foundation analysis • Roof Truss analysis • Hydronic subsystem analysis • Heat Transfer analysis • Building and Flat Plate Collector • F-Chart analysis

3. Floor Plan Layout

4. House Elevation Drawings

5. Foundation Analysis Assumptions: Flexure Strength of concrete is 600 psi Weight of a house without foundation walls is 20 lb/ft Soil density at site is 87.23 lb/ft^3 Factor of Safety of 5 Using max flexure strength of concrete at 120 psi after using the factor of safety, you can obtain a max bending moment of 144000 lb in by the formula σ=Mmax*c/I, where c is the distance at which the moment is applied and I is the moment of inertia Using that maximum moment in a bending diagram, you can obtain a maximum shear value of 1800 lb, which will also equal the reaction at the top of the foundation wall

6. Foundation Analysis After subbing in the reaction at the top of the foundation walls into the equations obtained from summing the forces in the x-direction of the free body diagram and the moment equation, you can find the force of the soil on the wall Using this maximum force, you can sub it into the fluid mechanics formula for hydrostatic fluid on a solid body, which is F=ρ*w*(d^2)/2, where ρ is the density of the soil, w is the maximum width of the wall without failure, and d is the distance of the soil, assumed here to be 10 feet, the full foundation wall length The maximum length of the wall without breaking made of pure concrete was found to be 1.24 feet for our 10 inch wall. It is then every 1.24 feet that rebar will be placed to handle the bending moment. For an extra factor of safety, rebar can be placed at every 1 foot.

7. Foundation Analysis There are two different types of foundation walls that can be used for this foundation. Masonary wall, which is cement blocks bonded together with mortar with rebar placed in the hollow core, or a poured cement wall with rebar placed inside the poured cement. Each type will require rebar at about the same interval, about 1 foot. The costs will be comparable to each other for installation, depending on the contractor. The advantage in the long run however is clearly poured concrete, as it has a much higher insulation value, which will reduce the amount of energy used for space heating. This can save a significant sum of money over the life of the home.

8. Foundation Analysis The allowable bearing pressure that can be placed on the soil according to the Salt Lake City building codes is 1500 lb/ft^2. By dividing the approximate weight of the house and foundation walls, 70,000 lbs, by the perimeter of the foundation, we can come up with that the footers should be about a foot wide to handle the load safely. Waterproofing should also be looked into for the area and the site that this house is to be built on. Options include plastic sheeting on the outside of the foundation walls and tar on the outside of the foundation walls.

9. Roof Truss Options

10. Roof Truss Analysis Givens/Assumptions: -1 truss every 2’ (25 total) -Southern pine 2x12’s -Southern pine: ρ=37 ft/lb3, σb max=1.56x106 lb/ft2, E=2.8x108 lb/ft2 -Factor of safety = 5 -Roof pitch: 65° lower section, 40° upper section (FPC location) -Allowable normal stress=1.66x105 lb/ft2 -Allowable bending stress=3.12x105 lb/ft2 Loading Conditions Roofing Material - 3.8 lb/ft2 Total FPC - 25 lb/ft2 (upper section only) Snow - 42.5 lb/ft2 (upper), 5 lb/ft2 (lower) Living - 20 lb/ft2

11. Gambrel Roof Truss Analysis Loading in members: BC = CD = 855.7 lb in Tension AB = DE = 1310.9 lb in Tension AE = 554 lb in Compression Normal stress in members: (allowable 166,000 lb/ft2) BC = CD = 7143 lb/ft2 (ok) AB = DE = 10943 lb/ft2 (ok) AE = 4625 lb/ft2 (ok) Bending stress in members: (allowable 312,000 lb/ft2) BC = CD = 5,240,000 lb/ft2 (X) AB = DE = 6,460,000 lb/ft2 (X) AE *= 11,500,000 lb/ft2 (X) Gambrel style achievable but extra supports needed will take some 2nd floor living space *some of living weight will be supported by rafters

12. Hydronic Subsystem Analysis Layout: The hot water storage tank will be located in the basement and piping will run up through the house through the bathrooms on each floor to the roof and FPC’s to minimize pipe lengths and keep piping neatly tucked away. Pipe/Fluid Selection: CPVC – Like PVC but designed for hot water applications 50/50 Water Glycol mix for fluid. Pump Selection: 8249K52 from the McMaster-Carr catalog, or 2 smaller circulating pumps if a smaller, quieter, more economical pump is desired over a robust one. Hot Water Storage & Heat Exchanger: Caleffi Solar Water Heater Tank (119 gallons) It has a built in heat exchanger and small back up heater if supply of hot water is exhausted. Head value for pump: With current values 32 feet Misc: -Considering adding insulation to piping, low cost/easy install -Components such as valves, fittings, elbows, can all be purchased off McMaster-Carr -It is not feasible to try to harness geothermal benefits in SLC

13. CPCV Vs. Copper Pipes:

14. Pump Selection Fluid- There are 127 days in SLC where temps drop below freezing. Also the record lows hit -30F. Therefore a mix of glycol and water (50%) will be used in the piping running from the FPC to the Heat Exchanger. With this mixture we still retain some of the benefits of using water, while gaining the benefits of glycol and not have to worry about water freezing in the pipes. *Flow must be increased %20 for a 50/50 glycol water mixture when compared to water. Pipe sizing- Flow rate is one major factor that governs pipe sizing. The less flow you have the smaller the piping you need. Our system has a particularly low flow so were going to go with ¾” piping. Pump Selection- 8249K52 from the McMaster-Carr catalog, or 2 smaller circulating . Both options will cover the need flow rate and head. The trade offs are that the smaller pumps are quieter, more economical. But they are not as robust and will most likely require more maintenance. Hot Water Storage & Heat Exchanger: (NAS20123) Caleffi Solar Water Heater Tank (119 gallons) It has a built in heat exchanger and small back up heater if supply of hot water is exhausted. 119 gallons was chosen after comparing various average water usages in homes. Very heavy hot water usage in families of 2 adults and 2 children were in the 119 gallon area. Average hot water usage varied from 60 to 80 gallons a day.

15. Sources (HSA): http://www.flasolar.com/pipes.php <-----pipe selection http://www.flasolar.com/active_dhw__heat_exchange.php <-----ditto http://geoheat.oit.edu/toa/toa5task2.pdf <---- study on geothermal feasability of SLC http://www.builderswebsource.com/techbriefs/cpvccopper.htm#Introduction <----plumbing selection http://www.aceee.org/consumerguide/waterheating.htm http://www.siliconsolar.com/solar-water-storage-tanks.html http://www.eagle-mt.com/radiantmax/indirect_tanks.php http://www.bamsolarpower.com/solarwaterheater.html http://www.mcmaster.com/#cpvc-drinking-water-pipe-fittings/=43qw8i <-pipe fittings http://www.engineeringtoolbox.com/ethylene-glycol-d_146.html <-sizing water glycol http://www.engineeringtoolbox.com/pvc-pipes-friction-loss-d_803.html <- friction loss of water in pvc http://harvelsprinklerpipe.com/harvel/pdf/friction-loss-tables.pdf <- friction loss of water in cpvc http://www.mcmaster.com/#8249k52/=455ks4 <-pump sized http://www.sssolar.com/Caleffi_Solar_SolarCon_solar_water_heater_tank_tech_specs.pdf http://www.pipeflowcalculations.com <- various useful calculators

16. Heat Transfer Analysis • Wall construction • Drywall (5/8’’) • Interior film (still air) • Foil faced insulation and air gaps 85% of wall area • Studs (2’’x6’’) 16’’ OC, 15% of wall area • Plywood (3/4’’) • Foil faced sheath • Exterior film (avg wind speed: 8.8mph) • Siding • Other construction materials • Windows ≤15% of wall area • Doors <5% of wall area • Concrete, poured or blocks • Thermal gradient: Tin=70°F Tout=10°F

17. Heat Transfer Analysis • Options • Wall versus windows • Buy better windows (low U-value) and insulate the walls less. • Buy decent widows and heavily insulate the walls. * U-value for windows must be ≤.3 in order to get energy tax credit of $1500 • Floor versus basement • Insulate the first floor thus excluding the basement from the thermal envelope • Do not insulate the first floor, and assume the concrete form of the basement will suffice for insulation. • Gambrel roof versus standard roof • This is not the option of the Building Thermal Engineer but it does affect the heat transfer analysis.

18. Heat Transfer Calcs *source http://www.coloradoenergy.org/procorner/stuff/r-values.htm

19. F-Chart • Best Case Scenario - House U value of 412.6 BTU/hr-F • 42.6% of the homes energy needs will be met by the FPC array with 5 solar collectors and a life cycle savings of $8761, and life cycle cost of $3081 for equipment and $15957 for additional heating bills. • Worst Case Scenario - House U value of 496.59 BTU/hr-F • 38.2% of the homes energy needs will be met by the FPC array with 5 solar collectors and a life cycle savings of $8976, and life cycle cost of $3081 for equipment and $19489 for additional heating bills. • The water temperature for these values was set to 125 deg F with 120 gallons used per day, and an environmental temperature of 70 deg F. Conventional heating was provided by electricity because it was the cheapest of the alternative heat sources. • The FPC units that were used for this simulation were 21.5 square feet in aperture area and an estimated cost per unit area of 37 $/ft^2, and oriented at an angle of 40deg from horizontal. • These values and costs can be changed by an increase in the homes overall insulation, as well as the addition of more collectors, however the number of collectors is limited by the area of the roof, and the roof trusses ability to support their weight. A lower estimate of hot water usage would also result in a more efficient system, as would lowering the temperature of the water. Another option would be to remove either the DHW or heating option.

20. Questions?