NET ZERO ELIZABETHTON TENN Photovoltaic System Annual Energy

NET ZERO ELIZABETHTON, TENN Photovoltaic System

Annual Energy Usage • 4 million KWH/month • 4 x 12 months = 48 Million KWH/year

Array Sizing • General Rule of Thumb • Average Daily Sun Hour Approach • PV Watts

General Rule of Thumb for Array Sizing • Each 1000 KWH desired requires approximately 1 KW • 48, 000 KWH / 1000 = 48, 000 KW or 48 MW • Assumes some shading, inverter inefficiency and other typical BOS losses

Average Daily Sun Hour Approach

Average Daily Sun Hour Approach (70% BOS efficiency) • AEO = Rated Power x Average Daily Sun Hours x 365 x BOS efficiency (70 to 80%) • Rated Power at 70% BOS eff = AEO / Average Daily Sun Hours x 365 x. 70 • Rated Power at 70% BOS eff = 48, 000 KWH / 4. 6 hrs/day x 365 x. 70 • Rated Power at 70% = 40, 840 KW = 40. 84 MW

Average Daily Sun Hour Approach (80% BOS efficiency) • AEO = Rated Power x Average Daily Sun Hours x 365 x BOS efficiency (70 to 80%) • Rated Power at 80% BOS eff = AEO / Average Daily Sun Hours x 365 x. 80 • Rated Power at 80% BOS eff = 48, 000 KWH / 4. 6 hrs/day x 365 x. 80 • Rated Power at 80% = 35, 735 KW = 35. 73 MW

PV Watts • http: //pvwatts. nrel. gov/ • Polysun might be another option (in room 40)

Estimated Installed Costs • 35, 000 watts x $1. 06/watt = $37, 100, 000

Land Required • Each MW requires 5 – 10 acres • 35 MW x 5 acres = 175 acres • 35 MW x 10 acres = 350 acres • Land should ideally be level with good solar access and close to grid connection

Number of Modules or Panels Required • https: //www. wholesalesolar. com/ • Astronergy 260 watt modules for example • 35 MW = 35, 000 watts / 260 watts per module = 134, 615 modules

Inverters • SMA is a good brand (http: //www. sma-america. com/ ) • Array DC rating is often 25% larger than inverter rating to save money without significantly reducing AEO because modules don’t produce their rated power and inverters are not 100% efficient • 35 MW / 1. 25 = 28 MW of inverter • SMA 2. 75 MW Inverter with 1500 VDC maximum input • 28 / 2. 75 MW = 10 inverters

String Sizing

String Sizing • Module Voc = 37. 78 • Record cold multiplier = 37. 78 x 1. 25 = 47. 22 Voc @ -31 C

String Sizing • 1500 volt maximum DC input voltage / 47. 22 Voc = 31. 7 = 31 modules per string is maximum • 134, 615 modules / 31 = 4342 strings or voltage units

Combiner Box • Combines strings in parallel to increase amps, power and energy production while mainting maximum voltage • Solar BOS is a good brand • 1500 VDC and 36 input circuits • 4342 strings / 36 = 121 combiner boxes • 121 / 10 inverters = 12. 1 combiner boxes/ inverter http: //www. solarbos. com/Combiners

Summary of System Design • 10 Inverters • 12 combiner boxes per inverter • 36 strings per combiner box • 31 modules per string

Racking • Schletter is a good brand in Charlotte http: //www. schletter. us/fs-system. html https: //www. youtube. com/watch? v=c. B 6 KMAey. OCc

Trackers • http: //arraytechinc. com/commercial/duratrack-hz-comm • 25% annual increase in KWH typical

Avoiding Shading with Multiple Rows of PV on Flat Roofs or Ground Mounts • Need to avoid shading problems • 3 times the height

3 times the height 3 x 40” = 120” 120/12 = 10’

Alternate Inter-row spacing • 3 x Height of row or module • 3 x 40” = 120”/12 = 10’

TRIG Method Example for south facing PV array: Distance between rows = H x cos azimuth angle tan altitude angle H = Vertical difference between top of module on one row to the bottom of module on the next row Target is typically 9 -3 on December 21 st