Solar Energy Systems in the Eco-Village at the University of Manitoba

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Solar Energy Systemsin the Eco-Village at the
University of Manitoba

• Mechanical Thesis Defense
• Heather King

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What is the aim of this thesis?

1. To discuss the types of solar collectors to be
   installed at the eco-village.
2. To determine the optimum angle and direction
   these collectors should be installed at.
3. To model the efficiency of the evacuated tube
   collector and the flat-plate collector.
4. To carry out a brief economic and environmental
   analysis.

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SOLAR COLLECTORS TO BE INSTALLED AT
THEECO-VILLAGE
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Apricus Evacuated Tube Collector
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How does it work?

• Radiation is absorbed from the sun through a
  system of 30 evacuated tubes.

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• A vacuum is created between the transparent
  outer tube and the selectively coated inner tube.

A copper heat pipe is inserted into the inner
tube. This works as a condenser.
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• Liquids boil at a lower temperature when the
  surrounding air pressure is decreased.
• Water in the heat pipe will vaporize if the
  temperature of the heat pipe reaches 30C.
• Vapor rises to the top of the heat pipe and
  transfers heat into the manifold fluid.
• This cooled vapor condenses and returns to the
  bottom as liquid.

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EnerWorks Flat Plate Collector
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How does it work?

• Radiation strikes the glazed, flat surface of the
  collector.
• Heat is transferred into
• the heat transfer
• fluid, which is
• then transferred
• into storage
• water through a
• heat exchanger.

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Sunsiaray Northern Comfort Flat-Plate Collector
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How does it work?

• Works the same way as the EnerWorks flat-plate
  collector.
• Only difference is that air flows through the
  fluid transfer tubes, not a heat transfer
  solution.

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NRG Solar Wall
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How does it work?

• Metal cladding on the wall contains thousands of
  tiny perforations that let air pass through.
• Air accumulates free heat from the cladding as it
  passes through.
• Warmed up heat is added to the HVAC system.

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SOLAR COLLECTOR LOCATION
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Ultimate Goal Determine the optimum tilt angle.

• S Tilt Angle

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1. Geographic Location
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2. Calculate the Incident Angle, ?

• Incident angle the angle between the suns rays
  and the plane surface of the collector

? Incident Angle
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• We want to optimize the tilt angle and direction.
• This can be done by setting cos? in the following
  relation equal to 1 and using the solver function
  in Excel to optimize S and F.
• cos? (sinA)(cosS) (cosA)(sinS)cos(Z-F) 1
• Where
• A the angle of elevation of the sun
• Z the azimuth angle of the sun
• S the tilt angle of the plane
• F the direction of the tilt angle

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Results Optimum Tilt Direction 0
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Results Optimum Tilt Angle ???
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3. Calculate the Solar Irradiance at the
Eco-Village

• In order to determine the optimum tilt angle of
  the plane we must calculate the amount of solar
  irradiance received at the Eco-Village.
• This is done by using the relation
• Where
• the direct radiation received by the
  collector
• the solar radiation received at
  ground level

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• Use varying values of the tilt angle, S, in the
  previous equation allows us to determine the
  optimum tilt angle.

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Results Optimum Tilt Angle 45- 50
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HEAT TRANSFER ANALYSIS
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Apricus Evacuated Tube Collector Efficiency
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• The transfer of heat through the collector is
  analyzed by modeling the collector as an electric
  circuit.
• The amount of useful energy collected by the
  evacuated tube collector is determined by
• Which allows us to calculate the collector
  efficiency

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Efficiency Calculator

• The seven variable inputs necessary for the
  spreadsheet to calculate the efficiency are
• 1. The temperature of the ambient air
  surrounding the collector, in degrees K.
• 2. The temperature of the heat transfer fluid
  entering the manifold, in degrees K.
• 3. The mean temperature of the collector tube,
  in degrees K.
• 4. The mean temperature of the heat pipe, in
  degrees K.
• 5. The mass flow rate, in kg/s, of the liquid
  within the heat pipe.
• 6. The velocity of the air flow over the
  collector, in m/s.
• 7. The month of the year. A scroll down menu is
  available for the user to choose the month of
  the year that the preceding three parameters
  were collected. Once the month of the year is
  known, the spreadsheet can calculate the
  appropriate incident radiation value received by
  the collector.

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EnerWorks Flat-Plate Collector

• The amount of useful energy collected by the
  flat-plate collector is determined by
• Which allows us to calculated the collector
  efficiency

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Efficiency Calculator

• The four variable inputs necessary for the
  spreadsheet to calculate the efficiency are
• 1. The temperature of the ambient air
  surrounding the collector, in degrees K.
• 2. The temperature of the heat transfer fluid
  entering the collector, in degrees K.
• 3. The mass flow rate, in kg/s, of the heat
  transfer fluid entering the collector.
• 4. The month of the year. A scroll down menu is
  available for the user to choose the month of
  the year that the preceding three parameters
  were collected. Once the month of the year is
  known, the spreadsheet can calculate the
  appropriate incident radiation value received by
  the collector.

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ECONOMIC ANALYSIS
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U of M District Heating System

• The power plant runs 6 steam boilers, two of
  which are summer boilers.
• These two summer
• boilers have a max
• steam output of
• 15,000 lbs/hour.
• The boilers run at
• approx. 81 efficiency.

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Can we replace one of the summer boilers with
solar energy?

• The most steam one of the summer boilers produced
  in 2006 was 9879 lbs/hour.
• In order to completely eliminate one of the
  summer boilers from the district heating system,
  a system of solar collectors must be able to
  produce the equivalent amount of energy as the
  produced by the boiler.
• Using the following relation, it can be seen that
  a boiler emitting 9879 lbs/hour of steam is rated
  at approximately 332.5 kW.

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How many collectors does it take to produce 332.5
kW?

• As we do not have any data collected from the
  collectors to test the efficiency calculators,
  the stated manufacturer efficiencies will be used
  in the following calculations.
• Collector Efficiencies
• Apricus Evacuated Tube Collector 0.717
• EnerWorks Flat-Plate Collector 0.4776 (using
  SRCC data)

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• The table below shows the RETScreen daily
  radiation values for Winnipeg Airport, in
  kWh/m²/d, converted to W/m².
• We will use the value for August (367.3 W/m²).

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Results
We would need to use a system of either 1. 418
Apricus Evacuated Tube Collectors - or- 2.
560 EnerWorks Flat-Plate Collectors
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What is the payback period of installing a system
of solar collectors?

• Boiler operation cost based on a natural
• gas price in Winnipeg of 0.024/kWh.
• CO2 reduction
• incentive based on a
• trading price of
• 32.40/tonne of CO2
• Reduction of 64.14 tonnes of CO2 per year!

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How much land is needed?
Approximately ½ a football field
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Rooftop Availability
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Engineering Building 1000 m²
Architecture Building 1500 m²
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Results A substantial amount of the district
heating system can be supplemented by solar
energy.
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CONCLUSIONS
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Evacuated Tube or Flat-Plate?

• Evacuated Tube Collectors

• Flat-Plate Collectors

• High accuracy (70 80)
• High price (2500)
• Easy to repair (replace one or more tubes)

• Moderate accuracy (35 - 45)
• Moderate cost (1750)
• Costly to repair (must replace the whole
  collector)

• Quantity over quality decision.
• In the long run, evacuated tube
  collectors are the recommended choice.

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Should solar collectors be installed?

• Yes, solar collectors should be installed.
• The payback period is less than the life span of
  the collectors, creating a profit for the
  university and a large reduction in carbon
  dioxide emissions.
• More research should be carried out to further
  examine the potential of installing solar
  collectors on the rooftops of campus buildings.

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QUESTIONS?