Photovoltaic Photovoltaic “Parallel System”“Parallel System”

forfor Duke Farms Duke Farms

Group Members

Trecia AshmanPaola BarryMukti Patel

Zarina Zayasortiz

Project UpdateProject Update In this update the group will discuss all of

the new findings as well as planned approaches for the spring semester of 2005. This semester, there will be a greater overall focus on the electrical layout design of the photovoltaic system as well as the refining and finalizing of the solar panel support.

Gantt ChartGantt Chart

Solar Energy HarvestingSolar Energy Harvesting For effective harvesting

of the sun’s rays the angle that the sun hits the panel must be close to 90 degrees.

When the angle is not 90 degrees the incoming power is reduced by a factor of cos(beta) Where beta is the is the

deviation from 90 degrees.

Solar Energy Harvesting Solar Energy Harvesting (cont.)(cont.) The modules should be placed

in an unobstructed area.

If the modules are set up behind one another, then the distance from each other has to be wide enough to prevent shading.

As in the case with Duke Farms, the modules will be set up on a stand and placed behind one another. The proper distance (b) has to be determined.

Control ConfigurationControl Configuration To enable one axis tracking a good control

configuration was needed.

Options One tracker for every five modules. One tracker that will control all of the modules

Master/slave configuration

Master/Slave Master/Slave ConfigurationConfiguration The primary module

will have a tracker, while the others (secondary modules) will mimic the motion of the primary module.

The motion will be mimicked by using small motors that will position the modules.

PVWATTS Algorithm PVWATTS Algorithm DescriptionDescriptionBackground:

Recommended by Department of Energy Internet accessible User sets location in US from station map User sets PV system parameters or selects default values Program performs hour-by-hour simulation

Monthly energy production (AC) in kilowatts Energy value in dollars

PVWATTS - BackgroundPVWATTS - BackgroundSystem Parameters:

Size (AC rating for Standard Reporting Conditions) PV array type (fixed or one/two-axis tracking) PV array tilt angle PV array azimuth angle System size can range from 0.5 to 1000 kW SRC stipulates certain meteorological conditions:

PV array solar irradiance of 1000 W/m2 Spectral irradiance conforming to American Society for

Testing and Material Standard E892 PV cell temperature of 25ºC

Electricity default cost is average 1999 residential electric rate for state selected

Program Parameter - Program Parameter - TrackingTracking

Program Parameter – Tilt Program Parameter – Tilt AngleAngle Angle from horizontal of the inclination of PV array

0º = horizontal and 90º = vertical For one-axis tracking:

Tilt angle is angle from horizontal of the inclination of tracker axis

Tilt angle not applicable for two-axis tracking Default angle is equal to station’s latitude

Normally maximizes annual energy production Increasing tilt angle favors energy production in winter Decreasing tilt angle favors energy production in

summer

Program Parameter – Program Parameter – Azimuth AngleAzimuth Angle

Angle clockwise from true north of direction that PV array faces For one-axis tracking:

Azimuth angle is angle clockwise from true north of direction of axis of rotation

Azimuth angle not applicable for two-axis tracking Default value is 180º (South-facing)

Normally maximizes energy production Increasing azimuth angle favors afternoon energy production Decreasing azimuth angle favors morning energy production

Orientation N NE E SE S SW W NW

Azimuth Angle (˚) 0 or 360 45 90 135 180 225 270 315

Set Program ParametersSet Program Parameters Users cannot change the following parameters:

Installed nominal operating cell temperature of 45ºC

Power degradation due to temperature of 0.5% per ºC

Soiling losses of 3%

Angle-of-Incidence (reflection) losses for glass PV module cover

PVWATTS CalculationsPVWATTS CalculationsMaximum Power of Array:

Accounts for differences in solar radiation and dry bulb temperature

Wind speed on module temperature and changes in inverter efficiency with power not accounted for (assumed small)

)](1[1000 0TT

EPmp

Where:Pmp = Maximum Power (Watts)E = Plane-of-Array (POA) Irradiance (W/m2)γ = Pmp Correction Factor for Temperature (-0.005 ˚C-1)T = PV Module Temperature (˚C)

PVWATTS Calculations PVWATTS Calculations (con’t)(con’t)

Monthly POA Irradiance (Edg): Sum of the direct beam, diffuse sky, and ground-reflected radiation

components Scaled based on ratios of monthly direct, diffuse, and global radiation Values for data grid cells denoted by subscript “dg” and for reference

stations “TMY”

reflskydn TMYTMY

dg

TMY

dgTMY

TMY

dgTMY

TMY

dgdg E

ALB

ALB

GH

GHE

DF

DFE

DN

DNE

Where:DN = Monthly Direct Normal RadiationDF = Monthly Diffuse Horizontal RadiationGH = Monthly Global Horizontal RadiationALB = Monthly Albedo = Monthly Direct Beam Component of POA = Monthly Diffuse Sky Component of POA = Monthly Ground Reflected Component of POA

dnTMYE

skyTMYE

reflTMYE

PVWATTS Calculations PVWATTS Calculations (con’t)(con’t)

Monthly AC Energy Production (ACdg):

Where:

ETMY = + +

Tdg = Monthly Average Daily Maximum Dry Bulb Temperature for Data Grid Cell

TTMY = Monthly Average Daily Maximum Dry Bulb Temperature for Reference Site

ACTMY = Monthly AC Energy Production Calculated for Reference Site

*Calculations have overall accuracy of 10-12%

TMYTMYdgTMY

dgdg ACTT

E

EAC )](1[

dnTMYEskyTMYE

reflTMYE

PVWATTS VerificationPVWATTS Verification PVWATTS was developed by the National

Renewable Energy Laboratory in order to calculate the electrical energy thaw would be produced by a d grid connected photovoltaic system.

The group cross checked the PVWATTS data with other 30 year data from the Department of Energy website in order to check the accuracy of the program.

The team uncovered that the PVWATTS generator was correct, since another source validated its data.

PVWATTS Verification PVWATTS Verification (cont.)(cont.) In order to verify the data on

PVWATTS, the group sampled data from January 1963, for a 50kW system with one axis tracking

The group found hourly data,

and totaled it for the month and checked to see if it matched with PVWATTS data

The total amount of AC power for January 1st 1963 is 6099900 watts or 6099.9kWh. The number that is generated by PVWATTS for a 50 kW system is 6110 kWh.

Year "Month" "Day" "Hour" "AC Power (W)"

1963 1 1 08:00 2439

1963 1 1 09:00 23962Total for January

1st

1963 1 1 10:00 34774 283009 watts

1963 1 1 11:00 36458

1963 1 1 12:00 43528

1963 1 1 13:00 42011

1963 1 1 14:00 40908

1963 1 1 15:00 36621

1963 1 1 16:00 21657

1963 1 1 17:00 651

PVWATTS Verification PVWATTS Verification (cont.)(cont.) The group also sampled

another data set from February 1966.

It was found that the data was also consistent.

The total amount of AC power for February 2nd 1966 is 6704357 watts or 6704.357kWh. The number generated by PVWATTS for a 50kW system in February is 6734 kWh.

Year "Month" "Day" "Hour" "AC Power (W)"

1966 2 27 07:00 212

1966 2 27 08:00 30701

1966 2 27 09:00 42787

1966 2 27 10:00 47515

1966 2 27 11:00 50939 Total for February 28th

1966 2 27 12:00 50080 382729 watts

1966 2 27 13:00 45641

1966 2 27 14:00 38079

1966 2 27 15:00 41025

1966 2 27 16:00 23701

1966 2 27 17:00 12049

Electrical LayoutElectrical Layout The group needs to communicate to

Duke Farms their alternatives

System that provides electricity only for Duke Farms:

1. No electricity is sold back to the grid.2. All surplus to power grid.

Interconnection Interconnection ProtectionProtection If surplus is connected back to the power grid it

is necessary

The function is three-fold: Disconnects the generator when it is no longer

operating in parallel with the utility system.

Protects the utility system from damage caused by connection of the generator, including the fault current supplied from the generator for utility system faults and transient over voltages.

Protects the generator from damage from the utility system, especially through automatic re-closing.

Interconnection Protection Interconnection Protection (Cont.)(Cont.) Interconnection protection varies

depending on the following factors: System Size Point of Interconnection to PSE&G Type of Power Generated Interconnection Transformer Configuration

Therefore the group needs to find what works best for our system.

Typical Interconnection Typical Interconnection SystemsSystems

Maintenance CostsMaintenance Costs This expense can be explored in

three ways: Delegate work to current

employees Hire part-time workers Hire contractors

System PlacementSystem Placement

VisualsVisualsLife-Sized Models vs. Display:

Life- Size Model Give the customer an idea of how one individual

module will look. Not working model.

Small Display Commercial visualization with the purpose to create

a better overall picture of the system and what kind of space it would take up.

Original Solar SupportOriginal Solar Support Several Problems:

Presence of a hole where pipe met flat part of support

Hole did not aid to the design

Created more stresses in the design

Presence of hole did not allow for one-axis tracking

Type of tracking group decided on

Refined Solar SupportRefined Solar Support

Figure 1 – Refined Design of Solar Support Figure 2 – Close-up of Solar Support Joint

Further analysis is needed in order to determine how wind, rain, and snow loading will affect this new design.

Total Capital CostTotal Capital Cost A large portion of the total capital cost will

come from the structures themselves. This large amount of capital will probably

need to be borrowed so interest costs will have to be taken into account.

Operation and maintenance costs will also be added to the total capital cost.

Payback PeriodPayback Period Factors that may cause the payback time

to change: The price you pay for your system will vary

depending on local market conditions. Another factor is that the energy generated by

your system depends on sunlight conditions at your location.

Finally, the inclination of your solar module array may be less than optimal.

QuestionsQuestions