Photovoltaic “Parallel System” for Duke Farms

1. Photovoltaic “Parallel System”for Duke Farms Group Members Trecia Ashman Paola Barry Mukti Patel Zarina Zayasortiz

2. Project 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.

3. Gantt Chart

4. Solar 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.

5. Solar Energy Harvesting (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.

6. Control 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

7. Master/Slave Configuration • 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.

8. PVWATTS Algorithm Description Background: • 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

9. PVWATTS - Background System 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

10. Program Parameter - Tracking

11. Program Parameter – Tilt Angle • 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

12. Program Parameter – Azimuth 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

13. Set 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

14. PVWATTS Calculations Maximum 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) 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)

15. PVWATTS Calculations (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” Where: DN = Monthly Direct Normal Radiation DF = Monthly Diffuse Horizontal Radiation GH = Monthly Global Horizontal Radiation ALB = Monthly Albedo = Monthly Direct Beam Component of POA = Monthly Diffuse Sky Component of POA = Monthly Ground Reflected Component of POA

16. PVWATTS Calculations (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%

17. PVWATTS 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.

18. PVWATTS Verification (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.

19. PVWATTS Verification (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.

20. Electrical Layout • The group needs to communicate to Duke Farms their alternatives System that provides electricity only for Duke Farms: • No electricity is sold back to the grid. • All surplus to power grid.

21. Interconnection Protection • 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.

22. Interconnection Protection (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.

23. Typical Interconnection Systems

24. Maintenance Costs • This expense can be explored in three ways: • Delegate work to current employees • Hire part-time workers • Hire contractors

25. System Placement

26. Visuals Life-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.

27. 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 Original Solar Support

28. Refined 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.

29. Total 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.

30. Payback 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.

31. Questions