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

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 10 6 BTU Natural gas costing $1.40 per Therm: $1.40* (10 Therms) / (70%) = $20.00/MMBTU 10 6 Btu Propane (LPG) costing $2.00 per Gallon: $2.00/gal* (10.5 gal) / (70%) = $30.00/MMBTU 10 6 Btu

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

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.

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?

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

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%

Compare Apples to Apples Requires looking at different energy sources on a delivered energy bases: Heat-BTUs Electricity - kWh

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!

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

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/m 2, 25°C Cell temperature Must be adjusted for site parameters

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

System Sizing Available Options for Solar Water Heating System Sizing – and Evaluation

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

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.

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

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

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 = 70 gallons An 80 gallon model would be selected for this application.

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

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 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.

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.

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

FSEC Simplified Sizing Procedure C-GP-10-R01.pdf

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

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

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)

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

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

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

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 Ft 2 from the FSEC ratings Use alternative energy technologies collector Model: AE-40Gross area: 40 ft 2 Intermediate Temperature Rating: 34,400 Btu/day

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 Ft 2 from the FSEC ratings Estimate number of collectors needed: Number = RATREQD / BTURATING Number = 30,840 / 34,400 Number = 0.90 = 1 collector

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 40ft 2 Total area = 40ft 2

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

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.”

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.

FSEC Simplified Residential Solar Hot Water system Calculator ater/homes/calculator/index.htm

F-Chart

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

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.

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