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Conversion Factors

Conversion Factors. Natural Gas (70-85%) 1 Therm 10 Therms. = 100,000 BTU = 1,000,000 BTU. Electricity (70-95%) 1 kWh 293.3 kWh. = 3,413 BTU = 1,000,000 BTU. #2 Fuel Oil (60-85%) 1 Gallon 7.2 Gallons. = 138,690 BTU = 1,000,000 BTU. LPG (70%) 1 Gallon 10.5 Gallons. = 95,475 BTU

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Conversion Factors

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  1. Conversion Factors • Natural Gas (70-85%) 1 Therm 10 Therms = 100,000 BTU = 1,000,000 BTU • Electricity (70-95%) • 1 kWh 293.3 kWh = 3,413 BTU = 1,000,000 BTU • #2 Fuel Oil (60-85%) 1 Gallon 7.2 Gallons = 138,690 BTU = 1,000,000 BTU • LPG (70%) 1 Gallon 10.5 Gallons = 95,475 BTU = 1,000,000 BTU

  2. Comparative cost and value • $10^6BTU=(Cost of Energy Unit) x (Energy Units Per Million Btu’s) / (Efficiency of Energy Conversion) For electricity costing 10 cents per kWh: • $.10*(293.3 kWh) / (95%) = $30.85/MMBTU KWh 106 BTU Natural gas costing $1.40 per Therm: • $1.40* (10 Therms) / (70%) = $20.00/MMBTU 106 Btu Propane (LPG) costing $2.00 per Gallon: • $2.00/gal* (10.5 gal) / (70%) = $30.00/MMBTU 106 Btu

  3. Solar Applications Sounds Great! What’s it Cost? What’s it worth? Where do we start?

  4. Economics of Solar • How can we compare the costs of Solar to Conventional Energy? • The problem is that the solar energy is free, typically the cost of solar is the initial cost of the installation and the operation & Maintenance costs to operate it (which is minimal) • Compare the cost of solar and conventional energy directly on a Life Cycle cost basis.

  5. Comparing the cost of solar to Other energy Sources • What is the cost of energy for: • Water or space Heating or Cooling? • Pool or Process Heating? • Electric Power Generation?

  6. How much do you pay for: • Electricity? • Natural Gas? • Oil? • Propane? Which is the better value?

  7. Comparing Operating Costs & Energy Efficiency of Water Heaters Efficiency (output/input) In same units i.e. (BTU in)/(BTU out) • Natural Gas fired water heater: 75% • Oil Fired Water Heater: 70% • Electric water Heater: 95% • Boilers: • NG Fired: 83% • Oil Fired: 80-85%

  8. Compare Apples to Apples • Requires looking at different energy sources on a delivered energy bases: Heat-BTUsElectricity - kWh

  9. Solar Costs for Energy • Determine the effective cost per energy unit when using solar • How? • We purchase solar energy in advance • We purchase it with “First Cost” and add a small O&M cost • Solar requires an initial investment but provides free energy over an extended period-determine the amount of energy produced and its value!

  10. Solar System Value ($/Energy Unit) • Solar Water heating • MMBtu per Year • Photovoltaic • kWh per year • Basis • Average climatic data • System parameters (energy ratings)

  11. Solar Equipment Energy Ratings • Solar water heating • SRCC Rating of Solar Collectors • Based on climatic data for location & Collector performance • Photovoltaic • Manufacturers STC Rating • Based on Standard test conditions • 1,000W/m2 , 25°C Cell temperature • Must be adjusted for site parameters

  12. Solar System Comparative Value Determination • Total life cycle cost ($) • Installed cost • O&M (1%/yr) • Energy Delivered (MMBTU – kWh) • Annual/monthly energy production • Life of system • Levelized cost $/MMBtu or $/kWh

  13. System Sizing • Available Options for Solar Water Heating System Sizing – and Evaluation

  14. Solar Water Heating • Rule of thumb • FSEC simplified sizing procedure • FSEC simplified residential solar hot water system calculator • F-Chart • RETScreen • TRNSYS

  15. Rule of thumb • Residential homes • 20-gallons per day for first two people • Then 15-gallons for each additional person • Family of one or two = 50 gallon system • Family of four = 80 gallon system • Family of six or more = 120 gallon system • 1 to 2 gallons per square foot of collector • Typical residential systems are 80 or 120 gallon solar tanks with electric or gas back up.

  16. Rule of thumb • 4 person family • 20 + 20 + 15 + 15 = 70 gallons • Thus use 80 gallon solar tank • 1 to 2 gallons per square foot of collector • Choose 2 gallons • 80 / 2 = 40ft2 • Thus use a 40 ft2 collector • 80 gallon solar tank with 40ft2 collector • Very rudimentary method – not much taken into consideration

  17. Rule of thumb • Gathering information – Site survey • Determine the volume of storage • Determine the temperature differential • Calculate the energy demand • Determine the solar resource • Putting it all together

  18. Rule of thumb Determining the Volume of Storage • Collect the number of persons or number of bedrooms in the home • Allow 20 gals/person for the first two persons and 15 gals/person for each additional person(s) • Calculate the required volume of storage • Example: (Family of 4) 2 x 20 gal = 40 gallons 2 x 15 gal = 30 gallons 40 + 30 = 70 gallons An 80 gallon model would be selected for this application.

  19. Rule of thumb Determining the Temperature Differential • Subtract the Avg Cold water inlet Temperature listed from a desired Tank Temperature of 140° F (▲T) • Calculate the temperature differential • 76° = Avg cold water inlet temp for Florida 140° - 76° = 64° ▲T

  20. Rule of thumb Calculate the Energy Demand (Btu’s) • A BTU (British Thermal Unit) equals the amount of energy required to raise 1 pound of water, 1 degree Fahrenheit • Water weighs approx. 8.34 pounds/gallon • Calculate the energy demand Example: (80 gals – Florida) 80 Gallons x 8.34 lbs/gal x 64° F = 42,701 BTU’s NOTE: Use standard storage tank sizes for calculation purposes. Using the calculate volume may result in an undersized system.

  21. Rule of thumb Determine the solar Resource • Determine the solar collector performance using the certification at right. • Calculate the number of collectors required by dividing the energy demand by the intermediate Temperature rating listed. Example: 42,701 / 21,700 = 2 (AE-26) collectors Thus, this system is 2 AE-26 collectors and one 80 gallon storage tank.

  22. FSEC Simplified Sizing Procedure • Developed for residential solar water heating systems in Florida • Step up from back of the envelope calculation • Requires information input • Based on mathematical calculations • Provides final solar fraction • Amount of hot water heated by the sun

  23. FSEC Simplified Sizing Procedure http://www.fsec.ucf.edu/en/publications/pdf/FSEC-GP-10-R01.pdf

  24. FSEC Simplified Sizing Procedure • Step 1 estimation of daily hot water use and selecting tank size

  25. FSEC Simplified Sizing Procedure • Step 2 Selecting cold water temperature for geographic location

  26. FSEC Simplified Sizing Procedure Step 3 Calculate how much energy is needed (BTU Needed) to heat the water to 122° F • BTU Need = 8.34 x Gallons x (122 – COLDTEMP) x Standby loss factor* • BTU Need = 8.34 x 55 Gallons x (122-72) x 1.12 • BTU Need = 8.34 x 55 x 50 x 1.12 • Btu Need = 25,687 (Round off to 25,700)

  27. FSEC Simplified Sizing Procedure Step 4 Determine penalty factors that affect system sizing • Table 3 system Factors • Table 4 Tilt Factors • Table 5 Orientation Factors

  28. FSEC Simplified Sizing Procedure Step 4 Determine penalty factors that affect system sizing • Table 3 system Factors • Table 4 Tilt Factors • Table 5 Orientation Factors

  29. FSEC Simplified Sizing Procedure Step 4 Determine penalty factors that affect system sizing • Table 3 system Factors • Table 4 Tilt Factors • Table 5 Orientation Factors

  30. FSEC Simplified Sizing Procedure • Step 6 for collector selected, record the thermal performance rating at the intermediate temperature (BTURATING) in Btu/day and gross collector area (GROSSAREA) in Ft2 from the FSEC ratings • Use alternative energy technologies collector Model: AE-40 Gross area: 40 ft2 Intermediate Temperature Rating: 34,400 Btu/day

  31. FSEC Simplified Sizing Procedure • Step 6 for collector selected, record the thermal performance rating at the intermediate temperature (BTURATING) in Btu/day and gross collector area (GROSSAREA) in Ft2 from the FSEC ratings • Estimate number of collectors needed: • Number = RATREQD / BTURATING • Number = 30,840 / 34,400 • Number = 0.90 = 1 collector

  32. FSEC Simplified Sizing Procedure • Step 7 select the actual number of collectors to be used. This is to the nearest whole number. • Select 1 collector • The total area of the collector array is • Total area = number of collectors x Gross area • Total area = 1 x 40ft2 • Total area = 40ft2

  33. FSEC Simplified Sizing Procedure • Based on the actual number of collectors to be used, compute the Solar Fraction • Solar fraction = 0.70 x Number of collectors = (0.70 x Step 7 [# of collectors]) / Step 6c [# of collectors before round off] • Solar Fraction = (0.70 x 1) / 90 = 78 • Solar Fraction = 78

  34. FSEC Simplified Residential Solar Hot Water system Calculator • Provides consumer information on the energy, cost and environmental savings potential of residential solar hot water systems in Florida • To use this calculator • Answer the two questions under the heading “Basics Solar System Information” Using the pull-down menus provided • For the input “Florida Climate Zone,” If your home is north of Volusia county, select “North” and if your home is south of St. Lucie County, select “South.” Otherwise select “Central.”

  35. FSEC Simplified Residential Solar Hot Water system Calculator • The calculator depends on a number of pre-selected assumptions. • To view and change these assumptions, select the checkbox below and the additional input fields will appear • If you choose to not change these assumptions, simply uncheck the box below anytime.

  36. FSEC Simplified Residential Solar Hot Water system Calculator http://www.fsec.ucf.edu/en/consumer/solar_hot_water/homes/calculator/index.htm

  37. F-Chart http://www.fchart.com/fchart/fchart.shtml

  38. F-Chart • Computer program useful for the analysis and design of active and passive solar heating systems • Developed at the University of Wisconsin Solar Energy Laboratory to estimate the long-term average performance of: • Domestic water heat (DWH)Systems • Pebble bed storage space and DWH Systems • Water storage space and DWH Systems • Active collection with building storage space heating systems • Direct-gain passive systems • Collector-storage wall passive systems • Pool heating systems • General solar heating systems (Process heating systems) • Integral collector-storage DWH systems

  39. F-Chart • Weather data for hundreds of north American locations, the 16 California climate zones and numerous other locations are included with the program User can add new weather data.

  40. Similar Annual Energy Use Profile in All Climates • Heating and/or Cooling (~40%) • Water Heating (~20%) • Appliances (~20%) • Lighting & plug in devices (~20%)

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