Title: Photovoltaic Design and Installation
1Photovoltaic Design and Installation
- Bucknell University Solar Scholars Program
Presenters Colin Davies 08 Eric Fournier 08
2Outline
- Why Renewable Energy?
- The Science of Photovoltaics
- System Configurations
- Principle Design Elements
- The Solar Scholars program at Bucknell (walking
tour)
3Whats wrong with this picture?
- Pollution from burning fossil fuels leads to an
increase in greenhouse gases, acid rain, and the
degradation of public health.
- In 2005, the U.S. emitted 2,513,609 metric tons
of carbon dioxide, 10,340 metric tons of sulfur
dioxide, and 3,961 metric tons of nitrogen oxides
from its power plants.
440
85 of our energy consumption is from fossil
fuels!
5Why Sustainable Energy Matters
- The worlds current energy system is built around
fossil fuels - Problems
- Fossil fuel reserves are ultimately finite
- Two-thirds of the world' s proven oil reserves
are locating in the Middle-East and North Africa
(which can lead to political and economic
instability)
6Why Sustainable Energy Matters
- Detrimental environmental impacts
- Extraction (mining operations)
- Combustion
- Global warming? (could lead to significant
changes in the world' s climate system, leading
to a rise in sea level and disruption of
agriculture and ecosystems)
7A Sustainable Energy Future
- Develop and deploy renewable energy sources on a
much wider scale - Bring down cost of renewable energy
- Make improvements in the efficiency of energy
conversion, distribution, and use
Three Methods - Incentives - Economy of
scale - Regulation
8Making the Change to Renewable Energy
- Solar
- Geothermal
- Wind
- Hydroelectric
9Todays Solar Picture
- Germany leads solar production (over 4.5 times
more then US production) Japan is 2nd (nearly 3
times more then US production) this is mainly
due to incentives - Financial Incentives
- Investment subsidies cost of installation of a
system is subsidized - Net metering the electricity utility buys PV
electricity from the producer under a multiyear
contract at a guaranteed rate - Renewable Energy Certificates ("RECs")
10Solar in Pennsylvania
- Pennsylvania is in fact a leader in renewable
energy - Incentives
- Local state grant and loan programs
- Tax deductions
- RECs (in 2006 varied from 5 to 90 per MWh,
median about 20)
11Harnessing the Sun
- Commonly known as solar cells, photovoltaic (PV)
devices convert light energy into electrical
energy - PV cells are constructed with semiconductor
materials, usually silicon-based - The photovoltaic effect is the basic physical
process by which a PV cell converts sunlight into
electricity - When light shines on a PV cell, it may be
reflected, absorbed, or pass right through. But
only the absorbed light generates electricity.
12Electricity
13Part 2 Learning Objectives
- Compare AC and DC electrical current and
understand their important differences - Explain the relationship between volts, amps,
amp-hours, watts, watt-hours, and kilowatt-hours - Learn about using electrical meters
14Electricity Terminology
- Electricity Flowing electrons
- Differences in electrical potential create
electron flow - Loads harness the kinetic energy of these flowing
electrons to do work - Flowing water is a good conceptual tool for
understanding
15Electricity Terminology
- Voltage (E or V)
- Unit of electromotive force
- Can be thought of as electrical pressure
- Amps (I or A)
- Rate of electron flow
- Electrical current
- 1 Amp 1 coulomb/second 6.3 x 1018
electrons/second
16Electricity Terminology
- Resistance (R or O)
- The opposition of a material to the flow of an
electrical current - Depends on
- Material
- Cross sectional area
- Length
- Temperature
17Electricity Terminology
- Watt (W) are a measure of Power
- Unit rate of electrical energy
- Amps x Volts Watts
- 1 Kilowatt (kW) 1000 watts
18Electricity Terminology
- Watt-hour (Wh) is a measure of energy
- Unit quantity of electrical energy (consumption
and production) - Watts x hours Watt-hours
- 1 Kilowatt-hour (kWh) 1000 Wh
19Power and Energy Calculation
- Draw a PV array composed of four 75 watt modules.
- What size is the system in watts ?
20Electricity Terminology
- Amp-hour (Ah)
- Quantity of electron flow
- Used for battery sizing
- Amps x hours Amp-hours
- Amp-hours x Volts Watt-hours
- A 200 Ah Battery delivering 1A will last _____
hours - 200 Ah Battery delivering10 A will last _____
hours - 100 Ah Battery x 12 V _____ Wh
21Types of Electrical Current
- DC Direct Current
- PV panels produce DC
- Batteries store DC
- AC Alternating Current
- Utility power
- Most consumer appliances use AC
22Meters and Testing
- Clamp on meter Digital
multimeter - Never test battery current using a multimeter!
23System Types
24Part 1 Learning Objectives
- Understand the functions of PV components
- Identify different system types
25Photovoltaic (PV) Terminology
- Cell lt Module lt Panel lt Array
- Battery stores DC energy
- Controller senses battery voltage and regulates
charging - Inverter converts direct current (DC ) energy
to alternating current (AC) energy - Loads anything that consumes energy
26Systems with DC Loads
27DC System Options
- Battery backup vs. discontinuous use
- LVD option in charge controller
- Load controllers
28Systems with AC loads
29AC System Options
- Combined AC and DC loads
- Hybrid system with back up generator
- Grid tied utility interactive system without
batteries - Grid tied interactive with battery backup
-
- (why might you need this?)
30Grid-Tied System(Without Batteries)
- Complexity
- Low Easy to install (less components)
- Grid Interaction
- Grid can supplement power
- No power when grid goes down
31Grid-Tied System(With Batteries)
- Complexity
- High Due to the addition of batteries
- Grid Interaction
- Grid still supplements power
- When grid goes down batteries supply power to
loads (aka battery backup)
32PV Modules
33Part 3 Learning Objectives
- Learn how a PV cell produces electricity from
sunlight - Discuss the 3 basic types of PV cell technologies
- Understand the effects of cell temperature and
solar insolation on PV performance - Gain understanding of module specification
- Identify the various parts of a module
34Solar Cells and the PV Effect
- Usually produced with Semi-conductor grade
silicon - Doping agents create positive and negative
regions - P/N junction results in 0.5 volts per cell
- Sunlight knocks available electrons loose
- Wire grid provides a path to direct current
35Inside a PV Cell
36Available Cell Technologies
- Single-crystal or Mono-crystalline Silicon
- Polycrystalline or Multi-crystalline Silicon
-
- Thin film
- Ex. Amorphous silicon or Cadmium Telluride
37Monocrystalline Silicon Modules
- Most efficient commercially available module (11
- 14) - Most expensive to produce
- Circular (square-round) cell creates wasted space
on module
38Polycrystalline Silicon Modules
- Less expensive to make than single crystalline
modules - Cells slightly less efficient than a single
crystalline (10 - 12) - Square shape cells fit into module efficiently
using the entire space
39Amorphous Thin Film
- Most inexpensive technology to produce
- Metal grid replaced with transparent oxides
- Efficiency 6 8
- Can be deposited on flexible substrates
- Less susceptible to shading problems
- Better performance in low light conditions that
with crystalline modules
40Selecting the Correct Module
- Practical Criteria
- Size
- Voltage
- Availability
- Warranty
- Mounting Characteristics
- Cost (per watt)
41Current-Voltage (I-V) Curve
42Voltage Terminology
- Nominal Voltage
- Ex. A PV panel that is sized to charge a 12 V
battery, but reads higher than 12 V) - Maximum Power Voltage (Vmax / Vmp)
- Ex. A PV panel with a 12 V nominal voltage will
read 17V-18V under MPPT conditions) - Open Circuit Voltage (Voc )
- This is seen in the early morning, late evening,
and while testing the module) - Standard Test Conditions (STC)
- 25 º C (77 º) cell temperature and 1000 W/m2
insolation
43Effects of Temperature
- As the PV cell temperature increases above 25º C,
the module Vmp decreases by approximately 0.5
per degree C
44Effects of Shading/Low Insolation
- As insolation decreases amperage decreases while
voltage remains roughly constant
45Other Issues
- Surface temperature can be measured using laser
thermometers - Insolation can be measured with a digital
pyranometer - Attaching a battery bank to a solar array will
decrease power production capacity
46PV Wiring
47Part 4 Learning Objectives
- List the characteristics of series circuits and
parallel circuits - Understand wiring of modules and batteries
- Describe 12V, 24V, and 48V designs
48Series Connections
- Loads/sources wired in series
-
- VOLTAGES ARE ADDITIVE
- CURRENT IS EQUAL
- One interconnection wire is used between two
components (negative connects with positive) - Combined modules make series string
- Leave the series string from a terminal not used
in the series connection
49Parallel Connections
- Loads/sources wired in parallel
- VOLTAGE REMAINS CONSTANT
- CURRENTS ARE ADDITIVE
- Two interconnection wires are used between two
components (positive to positive and negative to
negative) - Leave off of either terminal
- Modules exiting to next
- component can happen
- at any parallel terminal
50Quiz Time
- If you have 4 12V / 3A panels in an array what
would the power output be if that array were
wired in series? - What if it were wired in parallel?
- Is it possible to have a configuration that would
produce 24 V / 6 A? Why?
51Dissimilar Modules in Series
- Voltage remains additive
- If module A is 30V / 6A and module B is 15V / 3A
the resulting voltage will be? - Current taken on the lowest value
- For modules A and B wired in series what would be
the current level of the array?
52Dissimilar Modules in Parallel
- Amperage remains additive
- For the same modules A and B what would the
voltage be? - Voltage takes on the lower value.
- What would the voltage level of A and B wired in
parallel be?
53Shading on Modules
- Depends on orientation of internal module
circuitry relative to the orientation of the
shading. - SHADING can half
- or even completely
- eliminate the output
- of a solar array!
54Wiring Introduction
- PV installations must be in compliance with the
National Electrical Code (NEC) - Refer to NEC Article 690 (Solar Photovoltaic
Systems) for detailed electrical requirements - Discussion points
- Wire types, wire sizes
- Cables and conduit
- Voltage drops
- Disconnects
- Grounding
55Wire Types
- Conductor material copper (most common)
- Insulation material thermoplastic (most common)
- THHN most commonly used is dry, indoor locations
- THW, THWN, and TW can be used indoors or for wet
outdoor applications in conduit - UF and USE are good for moist or underground
applications - Wire exposed to sunlight must be classed as
sunlight resistant
56Color Coding of Wires
- Electrical wire insulation is color coded to
designate its function and use
57Cables and Conduit
- Cable two or more insulated conductors having an
overall covering - As with typical wire insulation, protective
covering on cable is rated for specific uses
(resistance to moisture, UV light, heat,
chemicals, or abrasion) - Conduit metal or plastic pipe that contains
wires - PVC is a common conduit used
- Using too many wires or too large of wires in a
given conduit size can cause overheating and
also causes problems when pulling wire
58Wire Size
- Wire size selection based on two criteria
- Ampacity
- Voltage drop
- Ampacity current carrying ability of a wire
- The larger the wire, the greater its capacity to
carry current - Wire size given in terms of American Wire Gauge
(AWG) - The higher the gauge number, the smaller the wire
- Voltage drop the loss of voltage due to a wires
resistance and length - Function of wire gauge, length of wire, and
current flow in the wire
59Safety Considerations
- Unsafe Wiring
- Splices outside the box
- Currents in grounding conductors
- Indoor rated cable used outdoors
- Single conductor cable exposed
- Hot fuses
- Disconnects
- Overcurrent Protection (Fuses Breakers)
60Safety Equipment
- Disconnects
- Allow electrical flow to be physically severed
(disconnected) to allow for safe servicing of
equipment
- Overcurrent Protection
- Protect an electrical circuit from damage caused
by overload or short circuit - Fuses
- Circuit Breakers
61Grounding
- Limit voltages due to
- Lightning
- Power line surges
- Unintentional contact with higher voltage lines
- Provides a current path for surplus electricity
to travel too (earth) - Two types of grounding
- Equipment grounding (attach all exposed metal
parts of PV system to the grounding electrode) - System grounding (at one point attach ground to
one current carrying conductor) - DC side of system gt Negative to ground
- AC side of system gt Neutral to ground
62Batteries
63Part 4 Learning Objectives
- Battery basics
- Battery functions
- Types of batteries
- Charging/discharging
- Depth of discharge
- Battery safety
64Batteries in Series and Parallel
- Series connections
- Builds voltage
- Parallel connections
- Builds amp-hour capacity
65Battery Basics
The Terms
- Battery
- A device that stores electrical energy (chemical
energy to electrical energy and vice-versa) - Capacity
- Amount of electrical energy the battery will
contain - State of Charge (SOC)
- Available battery capacity
- Depth of Discharge (DOD)
- Energy taken out of the battery
- Efficiency
- Energy out/Energy in (typically 80-85)
66Functions of a Battery
- Storage for the night
- Storage during cloudy weather
- Portable power
- Surge for starting motors
Due to the expense and inherit inefficiencies
of batteries it is recommended that they only be
used when absolutely necessary (i.e. in remote
locations or as battery backup for grid-tied
applications if power failures are common/lengthy)
67Batteries The Details
Types
- Primary (single use)
- Secondary (recharged)
- Shallow Cycle (20 DOD)
- Deep Cycle (50-80 DOD)
Charging/Discharging
- Unless lead-acid batteries are charged up to
100, they will loose capacity over time - Batteries should be equalized on a regular basis
68Battery Capacity
Capacity
- Amps x Hours Amp-hours (Ah)
100 amps for 1 hour 1 amp for 100 hours 20 amps
for 5 hours
100 Amp-hours
- Capacity changes with Discharge Rate
- The higher the discharge rate the lower the
capacity and vice versa - The higher the temperature the higher the percent
of rated capacity
69Rate of Charge or Discharge
- Rate C/T
- C Batterys rated capacity (Amp-hours)
- T The cycle time period (hours)
Maximum recommend charge/discharge rate C/3 to
C/5
70Cycle Life vs. Depth of Discharge
of Cycles
Depth Of Discharge (DOD)
71Battery Safety
- Batteries are EXTREMELY DANGEROUS handle with
care! - Keep batteries out of living space, and vent
battery box to the outside - Use a spill containment vessel
- Dont mix batteries (different types or old with
new) - Always disconnect batteries, and make sure tools
have insulated handles to prevent short
circuiting
72Battery Wiring Considerations
- Battery wiring leads should leave the battery
bank from opposite corners - Ensures equal charging and discharging prolongs
battery life - Make sure configuration of battery bank allows
for proper connections to be easily made
73Controllers Inverters
74Part 5 Learning Objectives
- Controller basics
- Controller features
- Inverter basics
- Specifying an inverter
75Controller Basics
Function
- To protect batteries from being overcharged
Features
- Maximum Power Point Tracking
- Tracks the peak power point of the array (can
improve power production by 20)!!
76Additional Controller Features
- Voltage Stepdown Controller compensates for
differing voltages between array and batteries
(ex. 48V array charging 12V battery) - By using a higher voltage array, smaller wire can
be used from the array to the batteries - Temperature Compensation adjusts the charging of
batteries according to ambient temperature
77Other Controller Considerations
- When specifying a controller you must consider
- DC input and output voltage
- Input and output current
- Any optional features you need
- Controller redundancy On a stand-alone system it
might be desirable to have more then one
controller per array in the event of a failure
78Inverter Basics
Function
- An electronic device used to convert direct
current (DC) electricity into alternating current
(AC) electricity
Drawbacks
- Efficiency penalty
- Complexity (read a component which can fail)
- Cost!!
79Specifying an Inverter
- What type of system are you designing?
- Stand-alone
- Stand-alone with back-up source (generator)
- Grid-Tied (without batteries)
- Grid-Tied (with battery back-up)
- Specifics
- AC Output (watts)
- Input voltage (based on modules and wiring)
- Output voltage (120V/240V residential)
- Input current (based on modules and wiring)
- Surge Capacity
- Efficiency
- Weather protection
- Metering/programming
80Solar Site
81Part 6 Learning Objectives
- Understand azimuth and altitude
- Explain magnetic declination
- Describe proper orientation and tilt angle for
solar collection - Describe the concept of solar window
82Site Selection Panel Direction
- Face south
- Correct for magnetic declination
83Orientation and Tilt Angle
84Sun Chart for 40 degrees N Latitude
85Site Selection Tilt Angle
Max performance is achieved when panels are
perpendicular to the suns rays
- Year round tilt latitude
- Winter 15 lat.
- Summer 15 lat.
86Solar Access
- Optimum Solar Window 9 am 3 pm
- Array should have NO SHADING in this window (or
longer if possible)
87Solar Pathfinder
- An essential tool in finding a good site for
solar is the Solar Pathfinder - Provides daily, monthly, and yearly solar hours
estimates
88Practical Determinants for Site Analysis
- Loads and time of use
- Local climate characteristics
- Distance from power conditioning equipment
- Accessibility for maintenance
- Aesthetics
89Energy Efficiency
90Part 7 Learning Objectives
- Identify cost effective electrical load reduction
strategies - List problematic loads for PV systems
- Describe penalties of PV system components
- Explain phantom loads
- Evaluate types of lighting efficiency comparison
91Practical Efficiency Recommendations
- For every 1 spent on energy efficiency, you save
3-5 on system cost - Adopt a load dominated approach
- Do it efficiently
- Do it another way
- Do with less
- Do without
- Do it using DC power
- Do it while the sun shines
92Typical Wattage Requirements
93Appliances to Avoid
- Electric oven or stove
- Electric space heater
- Dishwasher with heaters
- Electric water heater
- Electric clothes dryer
94Improving Energy Efficiency in the Home
- Space Heating
- Super insulation
- Passive solar design
- Wood stoves
- Propane
- Solar hot water
- Radiant Floor/ baseboard
- Efficient windows
- Domestic hot water heating
- Solar thermal
- Propane/natural gas
- No electric heaters
- On demand hot water
95Improving Energy Efficiency in the Home
- Kitchen Stoves
- Solar cookers
- Gas burners- no glow bar ignition
- Microwaves
- Washing machines
- High efficiency horizontal axis
- Cooling
- Ceiling fans
- Window shades
- Evaporative cooling
- Insulation
- Trees
- Reflective attic cover
- Attic fan
96Phantom Loads
97Phantom Loads
- Cost the United States
- 3 Billion / year
- 10 power plants
- 18 million tons of CO2
- More pollution than 6 million cars
- TVs and VCRs alone cost the US 1 Billion/year
in lost electricity
98Lighting Efficiency
- Factors effecting light efficiency
- Type of light
- Positioning of lights
- Fixture design
- Color of ceilings and walls
- Placement of switches
99Incandescent Lamps
- Advantages
- Most common
- Least expensive
- Pleasing light
- Disadvantages
- Low efficiency
- Short life 750 hours
Electricity is conducted through a filament which
resists the flow of electricity, heats up, and
glows Efficiency increases as lamp wattage
increases FROM THE POWER PLANT TO YOUR HOME
INCANDESCENT BULBS ARE LESS THAN 2 EFFICIENCT
100Fluorescent Bulbs
- Les wattage, same amount of lumens
- Longer life (10,000 hours)
- May have difficulty starting in cold environments
- Not good for lights that are repeatedly turned on
and off - Contain a small amount of mercury
101(No Transcript)
102Light Emitting Diode (LED) Lights
- Advantages
- Extremely efficient
- Long life (100,000 hours)
- Rugged
- No radio frequency interference
- Disadvantages
- Expensive (although prices are decreasing
steadily) - A relatively new technology
103Mounting
104Part 8 Learning Objectives
- Evaluate structural considerations
- List hardware requirements
- Pros and cons of different mounting techniques
105General Considerations
- Weather characteristics
- Wind intensity
- Estimated snowfall
- Site characteristics
- Corrosive salt water
- Animal interference
- Human factors
- Vandalism
- Theft protection
- Aesthetics
106Basic Mounting Options
- Fixed
- Roof, ground, pole
- Integrated
- Tracking
- Pole (active passive)
107Pole Mount Considerations
- Ask manufacturer for wind loading specification
for your array - Pole size
- Amount of concrete
- Etc.
- Array can be in close proximity to the house
without penetrations to roof structure
108Tracking Considerations
- Can increase system performance by
- 15 in winter months
- 40 in summer months
- Adds additional costs to the array
109Passive Vs. Active
- Passive
- Have no motors, controls, or gears
- Use the changing weight of a gaseous refrigerant
within a sealed frame member to track the sun - Active
- Linear actuator motors controlled by sensors
follow the sun throughout the day
110Roof Mount Considerations
- Penetrate the roof as little as possible
- Weatherproof all holes to prevent leaks
- May require the aid of a professional roofer
- Re-roof before putting modules up
- Ballasted roof mounts work on certain roofs
- Leave 4-6 airspace between roof and modules
- On sloped roofs, fasten mounts to rafters not
decking
111Building Integrated PV
112Ready for a field tour?
- Questions?
- If you are interested in anything you have seen
today and would like to get involved, please
contact any member of the Solar Scholars team - Colin Davies, Eric Fournier, or Jess Scott
- (cjdavies, efournie, jpscott)
113The END
- Thank you for participating in this lecture
series - Now lets go out into the field and take a look at
the systems that we have already installed.