Solar Thermal Solar Energy Workshop Colorado School of Mines

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Solar ThermalSolar Energy WorkshopColorado
School of Mines

• Presented by
• Daimon Vilppu,
• President, Simply Efficient
• Daimon_at_Simplyeff.com

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What it all boils down to

• Radiation
• Conduction
• Convection

Or, as I like to say Heat in/Heat out
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Heat Transfer of the collectors

• Allow sunlight in (transmittance)
• Dont allow sunlight out (emittance)
• Absorb the sunlight (absorptance)
• Transfer the sunlight energy to a fluid running
  through the collector (conductance and
  convection)
• Lose as little heat as possible (convection)

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Solar Ovens
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Solar Pool Heating Collectors
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Solar Hot Water and Heating
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Flat Plate Collectors
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Evacuated Tube Collectors
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Evacuated Tube Collectors
Viessman Vitosol 300, Cut-away View
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High Temperature (Concentrating Systems),
Industrial Power Generation, Hot Water, Process
Heat, System Owned By Solucar.
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Schott Solar Power Plant
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Solucar Parabolic Trough Concentrating
Collector The physical characteristics of the
concentrator modules are Overall Module Size 7
ft. 6 in. x 20 ft.(2.3m x 6.1 m) Concentrator
Weight 178 lb ( 81 kg) Concentrator Rim
Angle72 Materials of Construction Aluminum
Reflective SurfaceOptions Aluminum acrylic
Enhanced polished aluminumLightweight, low
maintenance concentratorReceiver The receiver
specifications are Absorber Tube Outside
Diameter 2.0 inch (5.08 cm) Absorber Material
SteelSelective Surface Blackened nickel
Absorptance  0.96 - 0.98 Emittance (80C)  0.15
- 0.25 Absorber Envelope Material Borosilicate
glass Envelope Anti-Reflective Coating Sol gel
Transmittance  0.95 - 0.965 Maximum Operating
Temperature 550F (288C)
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Solar Radiation

• Is Radiant energy from the sun (electromagnetic
  radiation) produced by a nuclear fusion reaction.
  Half of this radiation is in the Visible
  spectrum, the other half is mostly in the near
  infra-red spectrum of light.

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• Thermal systems use Diffuse and Direct Normal
  Light
• The National Solar Radiation Database gives us
  TMY (typical meteorological year) radiation data
  for cities across the US
• A computer simulation (TRNSYS) uses that data to
  give us the amount of radiation on a tilted
  surface.
• Denver, 45 degree, 20.89 MJ/m2 day, which is Mega
  Joules (106) per square meter for a day (1839
  BTU/ft2 day)
• SRCC (Solar Rating and Certification Center)
• Joule is the SI standard unit of energy
  (equivalent to a BTU)
• A Watt is Power in the SI units system.
• Also know as a Joule/Sec (BTU/hr)

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Solar Thermal Collectors

• Collect the suns radiation and transfer that to a
  fluid as it runs through them.
• Water, Propylene Glycol, Oil, Air
• High Temperature (Concentrating Systems),
  Industrial Power Generation
• Medium Temperature (Evacuated Tubes)
• Residential and Commercial
• Low Temperature (Flat plates)
• Unglazed (Pool Panels)

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Energy Storage

• WATER

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Why Water?

• Specific Heat is the amount of energy required to
  raise 1 gram of a material by one degree Kelvin.
• Water has a Constant Pressure specific heat of
  4.183 J/gK, Air 1 J/gK, Hydrogen 14,
  Concrete 0.88
• It is a measure of how much energy you can store
  in a mass of a material
• Water is frequently used because it is relatively
  cheap, abundant and holds more energy than most
  materials

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How Much Water?

• QMCp(T2-T1)
• Qenergy
• CpSpecific Heat
• T2Final Temperature
• T1Initial Temperature
• IF we had 2200 Kg of water ( approx. 120 gallons)
• And we wanted to raise its temperature 39 Kelvin
  (approx. 70 F)

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• We would need how much energy?
• Q(454 Kg)x(4.183 J/gK)x(39K)
• Q 74 MJ (Mega-Joules)

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• How many flat plate collectors would we need to
  do this in one day?
• A typical flat plate panel can collect on a cool
  clear day about 34 MJ/m2day
• Energy needed 74 MJ
• 74 MJ/ (24 MJ/m2day)
• 3 m2
• A 4x8 Collector is approx. 3 m2

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The rest of the equation

• For a system in Denver, I would recommend two
  4x8 panels.
• For a family of 3-4
• Solar Fraction, The amount of energy provided by
  the solar system divided by the amount of energy
  needed (or used).
• Modeling shows a 51 solar fraction for one panel
  and an 81 solar fraction for two panels (using
  Retscreen, available free online), a 70 solar
  fraction is considered best.
• What we havent considered
• Thermal losses
• In the pipes to and from the collector
• In the heat exchange between the collectors and
  the solar storage tank
• In the heat lost from the solar storage tank to
  the surroundings
• In the energy used up to pump the fluid through
  the collectors

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Total Solar Power Available to the USA

• 0.40 x 1367 W/m2 546.8 W/m2
• Available to the Earths surface
• Available to the USA
• 546.8 W/m2 x 9x1012 m2 4.921 Trillion KiloWatts
• Daily, Assuming 5 hours of useful sunlight that
  would be 5x4.921 Trillion KW 24.61 Trillion
  KWatts/day

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• USA use of Power, 2004
• 100,278 Trillion BTUs/year
• Convert that to Daily Watts
• 1 BTU 1055 Joules
• 365 days/year
• (100,278 Trillion BTUs/year)x(1055 J/BTU)x(1
  year/365 days)
• 289,800 Trillion Watts/Day
• 289.8 Trillion KW/Day

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Economics

• That system would cost from 8-10,000
• Would save about 500/year of electricity Which
  gives a best case simple payback of 16-20 years
  for electricity.
• This does not include the tax federal tax
  credit, any increase in electricity, appreciation
  of the home or reduction of greenhouse gasses

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• Thanks!
• I will be happy to answer questions
• Daimon Vilppu
• Daimon_at_Simplyeff.com
• 303-898-9951
• www.simplyeff.com