Download Solar Energy - Department of Mechanical and Materials Engineering

Solar Energy Introduction
MECH 430
Queen’s University,
Kingston, ON, Canada
Renewable Energy Renaissance
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Wind Energy
Solar Energy
Water Energy
Earth Energy
Bio Energy
Energy from Waste
Why Renewable Energy?
• Environment
• Energy Supply and security
• Cost
Motivation
Global Warming
- global warming is the increase in the average
temperature of Earth’s near-surface air and oceans
since the mid-20th century and its projected
continuation
- evidence for warming of the climate system
includes observed increases in global average air
and ocean temperatures, widespread melting of
snow and ice and rising global average sea level
- the most common measure of global warming is
the trend in globally averaged temperature near the
earth’s surface
Solar Collector Technology
Solar Resource
The Solar Energy Resource
The Solar
Energy
Spectrum
The Solar Energy Resource
here for Thursday Dec 3/15
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Varies over day and year
Generally non-dispatchable
Depends on the orientation
Solar constant 1360 W/m2 (Extraterrestrial)
Peak Power ~ 1kW/m2
Average Energy ~ 4 kWh/m2 day (Kingston)
Average Solar Radiation
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5
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2
1
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No
v
Oc
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Se
pt
Au
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Ju
l
Ju
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Ma
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Ap
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Ma
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Fe
b
0
Ja
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2
H (kWh/m day)
e.g., for 60
roof we
have 240 kWh/day
or 7200 kWh/month
0
30
45
60
6
m2
Collector Orientation
Effects of Receiving Surface
Tilt (fixed orientation)
Tracking vs
stationary
Tracki
ng
From “Solar Engineering of Thermal Processes”, Duffie & Beckman
Solar Energy Availability
From “Planning and Installing Solar Thermal Systems”, James & James/Earthscan, London, UK
The amount of solar energy available on the earth depends on the
geographical latitude and the time of day and year at a given location.
Average Solar Energy
The average annual global horizontal solar energy is
greater at lower latitudes, however this effect may be
reduced by tilting the receiver when at higher latitudes
Monthly solar irradiation (kWh/m2 per day on a horizontal surface) around the world
From “Planning and Installing Solar Thermal Systems”, James & James/Earthscan, London, UK
The Solar Energy Resource
How does Canada Compare?
Solar Radiation in Miami and Toronto on slope=latitude
0.7
Miami
Totonto
Toronto receives approx.
80% of solar radiation as
in Miami, and
Approx. 96% of solar
radiation as in Miami
from April to September.
Monthly total solar in GJ
0.6
0.5
0.4
0.3
0.2
0.1
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Jan Feb Mar Apr May Jun
Jul Aug Sep Oct Nov Dec
Solar Energy Conversion
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Passive solar:
– Direct gain – high performance fenestration/thermal mass
– Solar heating and daylighting
– Good architecture and energy conservation
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Photovoltaics: the production of electricity
– Grid connected/stand alone
– Building integrated PV
– “Net Zero” buildings
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Solar Thermal: solar heating
– space and water heating/cooling
– Packaged SDHW
– Solar boosted ground source heat pump
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PV Thermal/Hybrid systems
Passive Solar Heating
Summer
Good architecture?
The judicious use of south
glazing coupled with
appropriate shading and
thermal mass.
Winter
Attached
Sun
Space
Solar Thermal Energy
Photovoltaics Energy Systems
Utility-Scale Grid-Connected PV
Kingston Building
FIT program! (or unfit Program ?)
Solar Energy
Photovoltaics
Theory and Application
The PV Effect (http://inventors.about.com)
1904:Einstein published his paper on the
photoelectric effect.
1923: Albert Einstein received the Nobel
Prize for his theories explaining the
photoelectric effect.
1954: The PV effect in Cd was reported; primary
work was performed by Rappaport, Loferski and
Jenny at RCA. Bell Labs researchers Pearson,
Chapin, and Fuller reported their discovery of
4.5% efficient silicon solar cells; this was raised
to 6% only a few months later (by a work team
including Mort Prince).
Photovoltaic Systems
- the term “photovoltaic” refers to the direct generation of
electricity by solar irradiation
photo = light
voltaics = electricity
photovoltaics = electricity from light
abbreviated as “PV”
Types of Silicon Solar Cells
- the three types of silicon cells are:
• mono-crystaline
• poly-crystaline
• amorphous
mono-crystaline
polycrystaline
amorphous
Source: Alternative Energy Systems and Applications, B.K. Hodge
Photovoltaic Cell Fundamentals
- photovoltaic cells are made of a semiconductor material
- the most common semiconductor used is silicon
- the two layers of silicon that constitute a silicon-based PV cell are
modified (doped) to more likely:
1) loose electrons
2) produce holes in the molecular structure where electrons
can reattach
+
silicon-based PV cell
Photovoltaic Cell Fundamentals
- as an example, in one PV cell design, the upper or n-type layer is
doped with phosphorus with 5 valence electrons while the lower or
p-type layer is doped with boron, which has 3 valence electrons
(recall that the silicon atom has 4 valence electrons in its outer shell)
- if the incident photon is energetic enough to dislodge a valance
electron (from the depletion zone / electric field), the electron will
jump to the conduction band and initiate a current flow
Prof. C. A. Cruickshank, Carleton University
Current Density Ratio and Power Ratio vs. Voltage
- I-V Characteristics Curve
Prof. C. A. Cruickshank, Carleton University
Standard Test Conditions and Temperature and Irradiance Effects
- the efficiency η of a solar cell is defined as:
the power Pmax produced by the cell at the maximum power point
under standard test conditions
the power of the radiation incident upon it
- most frequent conditions are: irradiance 100 mW/cm2, standard
reference AM1.5 spectrum, and temperature 25oC
- in practical applications, however, solar cells do not operate under
standard conditions
- the two most important effects that must be allowed for are due
to the variable temperature and irradiance
Efficiency of PV
Optimal Running Condition
- although it is desired to operate the cell at the maximum power
point, this may not easily be realize in practice
- a simpler but less efficient solution is to operate the cell at a
constant voltage below the voltage of maximum power point
- if the operating voltage remains in the linear part of the I-V
characteristic, temperature will have little effect on the power
output
- the power delivered to the
load will therefore be proportional to the short circuit
current and thus also irradiance
Source: Solar Electricity, Tomas Markvart
Prof. C. A. Cruickshank, Carleton University
The price of solar photovoltaic cells has dropped 99% in the past quarter
century. So in an increasing number of markets around the country, solar is
at or very close to grid parity, (http://thinkprogress.org)
the levelized cost of electricity
More and more countries and
regions will reach residential grid
parity. Germany, Spain, Italy,
Australia and Hawaii were among
the first to do so.
Photovoltaic Components
- the basic building block of a PV system is the individual solar cell
- individual cells are assimilated into ‘strings’ which make up a
module; modules are then assembled in arrays
- modules are constructed by placing PV cells in series and parallel
arrangements
glass cover to protect cells
various frame and backing materials to facilitate mounting
Prof. C. A. Cruickshank, Carleton University
Photovoltaic Components
- series and parallel configurations of solar cells follow the same rules as
series and parallel DC circuits
- for identical components placed in series, the voltages add at constant
current (multiple cells in series to increase operating voltage)
- for identical components placed in parallel, the currents add at
constant voltage (multiple strings in parallel increase current – used to
power up to several MW)
series
Source: Alternative Energy Systems and Applications, B.K. Hodge
parallel
EXAMPLE
Photovoltaic cells are to be arranged to provide an output of 12 V and
a power of 120 W. If the voltage and current at maximum power are
0.493 V and 5.13 A (V*I = 2.53 W), recommend an arrangement that
meets the specifications.
SOLUTION
- the number of cells required for 120 W is
number of cells = 120 W / (2.53 W/cell) = 47.2 cells
- to provide the correct voltage 12 V, the number of cells in series are
cells in series = 12 V/ (0.493 V/cell) = 24.3 cells
- the number of cells in series can be rounding up to 25; two rows of 25
cells in parallel will required 50 cells with a total power of 126.5 W
SOLUTION
- the number of cells required for 120 W is
number of cells = 120 W / (2.53 W/cell) = 47.2 cells
- to provide the correct voltage 12 V, the number of cells in series are
cells in series = 12 V/ (0.493 V/cell) = 24.3 cells
- the number of cells in series can be rounding up to 25; two rows of 25
cells in parallel will required 50 cells with a total power of 126.5 W
Photovoltaics Energy Systems
Photovoltaics Energy Systems
Stand Alone
PV Systems with
Battery Backup
Renewable Energy
Technologies
How do we get “connected”?
Photovoltaics Energy Systems
Example: Building Integrated Solar Cells
(Goodwin Hall @ Queen’s)
Building Integrated Solar Cells: Construction
Utility-Scale Grid-Connected PV
Solar Generation in Ontario
Large scale (transmission-level grid) solar expected to come into service in
early 2014.
A list of solar projects are scheduled to come in service by Winter 2015
Haldimand Solar Project (100 MW)
2014-Q1
Silvercreek Solar Park (10 MW)
2014-Q3
Liskeard 1 (10 MW)
2014-Q3
Liskeard 2 (10 MW)
2014-Q3
Liskeard 3 (10 MW)
2014-Q3
Northland Power Solar Abitibi (10 MW)
2014-Q3
Northland Power Solar Empire (10 MW)
2014-Q3
Northland Power Solar Long Lake (10 MW)
2014-Q3
Northland Power Solar Martin’s Meadows (10 MW)
2014-Q3
Kingston Solar Project (100 MW)
2014-Q4
https://www.ieso.ca/imoweb/marketdata/windpower.asp
PV versus Solar Thermal
Physics: Where Does the Energy Go?
PV
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10 – 15% Electricity
10% Optical loss
75 – 80 % Waste Heat
$1 - $2 /Watt
Thermal
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15% Optical loss
45% Useful Heat
40% Heat Losses
$1-3 /Watt (thermal)
EcoTerraTM EQuilibrium House (Alouette Homes)
– an example of transformative SBRN work
2.8-kW
Buildingintegrated
photovoltaicthermal
system
Passive solar
design:
Optimized
triple glazed
windows and
mass
Prefabricated home
Partners:
NRCan, CMHC
designed to have close to net-zero annual energy consumption
Groundsource heat
pump
Active Solar Thermal
Energy Systems
• Can generate “clean & green” energy
- Photovoltaics >>> electrical energy
- Solar Thermal >>> thermal energy
• high capital cost - low fuel cost
• Both can displace conventional energy
and power production/consumption and
reduce peak loads
Residential Solar Heating
Applications
Solar Collection Basics:
Collector Types
• Stationary
– Fixed racks or roof installation
– No moving mechanical components
– Radiation intensity varies over day and season
• Tracking
– Increases incident solar radiation
– Enables high concentrations/temperatures
– Usually increased mechanical complexity
• Hybrids
– “Fixed” racks can be adjusted in tilt to account
for seasonal variations
– Tracking collectors can be single or dual axis
tracking
Glazed Flat-Plate Collectors
Advantages
• offers multiple mounting options
• good price/performance ratio
• typically cheaper than vacuum collector
• proven performance --durable
Disadvantages
• lower efficiency for high temperature applications because the
heat loss coefficient is higher (recent work on multi-glazed is
improving high temperature performance)
• not normally used for generating high temperatures (+100oC)
• may be heavier than other options
Flat Plate Solar Collector Designs
The task of a solar collector is to achieve the highest possible thermal yield.
Different collector designs
From “Planning and Installing Solar Thermal Systems”, James & James/Earthscan, London, UK
Glazed Flat-Plate Collectors
1. Frame
2. Seal
3. Transparent cover
4. Frame – side-wall
profile
5. Thermal insulation
6. Full-surface
absorber
7. Fluid channel
8. Fixing slot
9. Rear wall
From “Planning and Installing Solar Thermal Systems”, James & James/Earthscan, London, UK
Unglazed Swimming Pool
Collectors
Evacuated Tube Collectors (ETC’s)
Advantages
• achieves a high efficiency even with large ΔT’s between
absorber and surroundings
• low in weight, can be assembled at installation site
• may have lower wind loading?
Disadvantages
• more expensive than a glazed flat-plate collector
• cannot be used for in-roof installation
• most heat pipe systems need to be inclined at least 25o tilt to
horizontal
Typical Efficiencies of Collectors
Solar Collector Performance Plots
Ambient
0.9
0.8
Low Temp
High Temp
Medium
0.7
Efficiency
0.6
0.5
1
0.4
0.3
2
3
1 - Vacuum Tube
Collector
0.2
0.1
3 - Unglazed Swimming
Pool Absorber
2 - Glazed Flat
Plate Collector
0
(Ti-Ta)/G, (m2 oC) / W
Solar collector efficiencies generally fall within specific ranges.
#
FR  (  )e
FR  UL (W/m2oC)
1
0.5 - 0.75
1-2
Depends on tube spacing for ETC
2
0.65 - 0.8
3-8
Depends on # of covers and absorber coating
3
0.8 - 0.95
10 - 20
Depends on wind speed
Sun Tracking Concentrating Solar Collectors
Concentration of solar radiation to increase high temperature performance
Concentration of solar radiation: single reflector
with two-axis tracking
From “Planning and Installing Solar Thermal Systems”, James & James/Earthscan, London, UK
Concentration of solar radiation: multiple
reflectors with two-axis tracking
Power Generation Systems
Usually use high temperature concentrating collectors to produce
steam to turn a turbine/generator unit.. Suitable for locations with
clear sunny days
Concentrating Solar Collectors
Parabolic Trough Collectors
The world's largest solar
power facility, located near
Kramer Junction, CA.
Solar Air Preheat
Source: http://www.rockymtsolar.com/
Source: http://oee.nrcan.gc.ca/
Solar Air Heating Systems
Solar Water Heating
Systems
Types
Thermosyphon
bread box
Close coupled
Drain Down
Drain Back
Closed Loop anti-freeze
Solar Domestic Hot Water
(Passive Systems)
Source: http://www.volker-quaschning.de/
From “Solar Thermal Systems”, James & James, London, UK
Passive solar systems have no pumps, controls, or moving parts.
Indirect Solar Domestic Hot Water System
Solar
Collector
Fixed
Flow Rate
Roof Line
Hot Water
to Load
Storage
Tank
Heat
Exchanger
Electric Pump
Variable
Flow
Rate
Storage
Tank
Cold Mains
Inlet
Solar Domestic Hot Water Heating
6.1.
Howard Johnson Hotel in Kingston
HOSPITAL FOR SICK CHILDREN, TORONTO
Commercial Systems
System
Description:
• Green Phoenix Apt
Toronto Canada
• 40 EnerWorks
collectors
• 93,798 kWh per
year
• 27% solar fraction
• 4 year payback
Example Projects
Commercial Installations
Toronto Hospital For
Sick Children
- 92 collectors offsets
domestic hot water
U of T 100 Collectors
6 x 454 L storage tanks
System Schematic
Drake Landing Solar District Heating
Source: “http://www.dlsc.ca/”
Drake’s Landing Solar Community Highlights
• the largest subdivision of R-2000 single family
homes in Canada, each 30% more efficient than
conventionally built homes
• a first in the world, 90% of residential space heating
needs will be met by solar thermal energy.
• a reduction of approximately 5 tonnes of greenhouse
gas (GHG) emissions per home per year
Drake Landing Solar Community (Okotoks Alberta)
> 95% annual Solar Fraction for space and water heating
District Heating System
• there are four
individual home-run
loops off a manifold
in the Energy
Centre
• plastic, insulated,
underground pipe is
used to distribute
heated water from
the community’s
Energy Centre back
to the homes
Source: “http://www.dlsc.ca/”
Thermal Storage and Demand Side Management
The Energy Centre
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