determining wind and snow loads for solar panels America s Authority on Solar

determining wind and snow loads for solar panels America s Authority on Solar

Determining wind and snow loads for solar panels 1 introduction As one of the largest and most established vertically integrated photovoltaic (PV) manufacturers on the planet, SolarWorld is intimately involved with every step of the solar PV value chain from raw silicon to installed systems to end of life recycling. This complete knowledge base combined with our extensive history provide the critical insight required to lead the solar industry on technical topics. The purpose of this paper is to discuss the mechanical design of photovoltaic systems for wind and snow loads in the United States, and provide guidance using The American Society of Civil Engineers (ASCE) Minimum Design Loads for Buildings and Other Structures, ASCE 7-05 and ASCE 7-10 as appropriate. With the introduction of the ASCE 7-10, there are two potential design principles used for calculating wind and snow loads for PV systems in the U.S. until all state building codes have transitioned to ASCE 7-10. This paper will show how to calculate for wind and snow loads using both design principles. SolarWorld modules have been tested according to UL and IEC standards and the maximum design loads for various mounting methods are provided in the Sunmodule User Instruction guide. Once we have gone through the sample calculations and have the applicable wind and snow loads, we will compare them to SolarWorld s higher mechanical load capacities to ensure that the Sunmodule solar modules are in compliance. The design methodology in this document has been third party reviewed. Please see certified letter at the end of this document for more details.

Determining wind and snow loads for solar panels 2 Figure 1. A typical rooftop solar installation. U.S. model building codes have used ASCE 7-05 as the basis for several years, which largely follows the design principles of Allowable Stress Design. Recently ASCE 7-10 was published and has become the basis for the 2012 series of the International Codes (I-Codes). ASCE 7-10 represents a shift in design principles toward Load Resistance Factor Design. A few states have already adopted the 2012 International Building Code 2012 (IBC) that includes references to ASCE 7-10 and, for the first time, specifically mentions PV systems. There are several key differences between these two versions of ASCE 7 standards. This paper provides sample calculations following both ASCE 7 standards that are reflected in the 2012 IBC and earlier versions.

Determining wind and snow loads for solar panels 3 Below are the portions of the code that will be referenced in the sample calculations: IBC 2012 (ASCE 7-10) Code References IBC 2009 (ASCE 7-05) Code References 1509.7.1 Wind resistance. Rooftop mounted photovoltaic systems shall be designed for wind loads for component and cladding in accordance with Chapter 16 using an effective wind area based on the dimensions of a single unit frame. 1603.1.4 Wind Design data. The following information related to wind loads shall be shown, regardless of whether wind loads govern the design of the lateral force resisting system of the structure: 1) Ultimate design wind speed, V 2) Risk category 3) Wind Exposure 4) Internal pressure coefficient 5) Component and cladding 1608.1 Design snow loads shall be determined in accordance with Chapter 7 of ASCE 7, but the design roof load shall not be less than that determined by section 1607. 1609.1.1 Determination of wind loads. Wind loads on every building or structure shall be determined in accordance with Chapter 26 to 36 of ASCE 7 or provisions of the alternate all-heights method in section 1606.6. 1609.4.1 Wind Directions and Sectors. For each selected wind direction at which the wind loads are to be evaluated, the exposure of the building or structure shall be determined for the two upwind sectors extending 45 degrees either side of the selected wind direction. The exposures in these two sectors shall be determined in accordance with Section 1609.4.2 and 1609.4.3 and the exposure resulting in the highest wind loads shall be used to represent wind from that direction. 1608.1 Design snow loads shall be determined in accordance with Chapter 7 of ASCE 7, but the design roof load shall not be less than that determined by Section 1607. 1603.1.4 Wind Design Data 1) Basic wind 2) Wind importance factor 3) Wind exposure 4) The applicable internal pressure coefficient 5) Components and cladding 1609.1.1 Wind loads on every building or structure shall be determined in accordance with Chapter 6 of ASCE 7. Table 1609.3.1, which converts from 3-second gusts to fastest-mile wind speeds. 1609.4.1 Wind Directions and Sectors 1) Select wind direction for wind loads to be evaluated. 2) Two upwind sectors extending 45 degrees from either side of the chosen wind direction are the markers. 3) Use Section 1609.4.2 and Section 1609.4.3 to determine the exposure in those sectors. 4) The exposure with the highest wind loads is chosen for that wind direction. 1609.4.2 Surface Roughness Categories 1) Surface roughness B: Urban, suburban, wooded, closely spaced obstructions. 2) Surface roughness C: Open terrain with few obstructions (generally less than 30 feet), flat open country, grasslands, water surfaces in hurricaneprone regions. 3) Surface roughness D: Flat areas and water surfaces outside of hurricane prone regions, smooth mud flats, salt flats, unbroken ice.

Determining wind and snow loads for solar panels 4 In this paper, examples explain step-by-step procedures for calculating wind and snow loads on PV systems with the following qualifications in accordance with ASCE. The recommended chapter references for ASCE 7-05 are: Chapter 2 Load Combinations Chapter 6 Wind Load Calculations Chapter 7 Snow Load Calculations In ASCE 7-10, the chapters have been re-organized and provide more detailed guidance on certain topics. The recommended chapter references are: Chapter 2 Load Combinations Chapter 7 Snow Load Calculations Chapters 26 31 Wind Load Calculations Example calculations: In the following examples, we outline how a designer should calculate the effect of wind and snow loads on a PV module for residential and commercial buildings based on few assumptions and using the Low-Rise Building Simplified Procedure. ASCE 7-05: Section 6.4 ASCE 7-10: Section 30.5 In the Simplified Method the system must have the following qualifications (see ASCE 7.05 section 6.4.1.2 or ASCE 7-10 section 30.5.1 for further explanation): The modules shall be parallel to surface of the roof with no more than 10 inches of space between the roof surface and bottom of the PV module. The building is not in an extreme geographic location such as a narrow canyon a steep cliff. The building has a flat or gable roof with a pitch less than 45 degrees or a hip roof with a pitch less than 27 degrees. In case of designing more complicated projects the following sections are recommended: ASCE 7-05: Section 6.5.13.2 ASCE 7-10: Section 30.8 Example 1 - Residential Structure in Colorado: System Details: Location: Colorado Terrain: Urban, suburban, wooded, closely spaced obstructions Exposure: Class B Building Type: Single-story residential (10- to 15-feet tall) Mean height of roof: ~12.33 feet Building Shape: Gable roof with 30 pitch (7:12) System: Two Rail System; attached module at four points along the long side between 1/8 to 1/4 points as described in the SolarWorld Sunmodule User Instruction guide Module area: 18.05 ft (Reference: Sunmodule datasheet) Module weight: 46.7 lbs (Reference: Sunmodule datasheet) Site ground snow load (P g ): 20 psf The building height must be less than 60 feet. The building must be enclosed, not open or partially enclosed structure like carport. The building is regular shaped with no unusual geometrical irregularity in spatial form, for example a geodesic dome.

Determining wind and snow loads for solar panels 5 SYMBOLS AND NOTATIONS Wind I = Importance factor K zt = Topographic factor P = Design pressure to be used in determination of wind loads for buildings 30 = Net design wind pressure for exposure B at h = 30 feet and I = 1.0 V = Basic wind speed λ = Adjustment factor for building height and exposure Zone 1 = Interiors of the roof (Middle) Zone 2 = Ends of the roof (Edge) Zone 3 = Corners of the roof Snow C e = Exposure factor C s = Slope factor C t = Thermal factor I = Importance factor = Snow load on flat roof P g = Ground snow load P s = Sloped roof snow load Load Combination D* = Dead load E = Earthquake load F = Load due to fluids with well-defined pressures and maximum heights H = Load due to lateral earth pressure, ground water pressure or pressure of bulk materials L = Live load L r = Roof live load R = Rain load S* = Snow load T = Self-straining load W* = Wind load Hip Roof Gable Roof Interior Zones Roofs - Zone 1 Interior Zones Roofs - Zone 2 Interior Zones Roofs - Zone 3 * In this white paper we only use dead, snow and wind loads.

Determining wind and snow loads for solar panels 6 ASCE 7-10 (IBC 2012) ASCE 7-05 (IBC 2009) Steps in wind design: Steps in wind design: 1. Determine risk category from Table 1.5-1 1. Determine risk category from Table 1.5-1 Risk category type II Risk category type II 2. Determine the basic wind speed, V, for applicable risk category (see Figure 26.5-1 A, B, C) 2. Determine the basic wind speed, V, for applicable risk category (see Figure 6-1 A, B, C) Wind speed in Colorado is V = 115 mph Wind speed in Colorado is V = 90 mph (excluding special wind regions) (excluding special wind regions) 3. Determine wind load parameters: Exposure category B, C or D from Section 26.7 Exposure B 3. Determine wind load parameters: Exposure category B, C or D from Section 6.5.6.3 Exposure B Topographic factor, K zt, from Section 26.8 and Figure 26.8-1 K zt = 1.0 Topographic factor, K zt, from Section 6.5.7.2 K zt = 1.0 4. Determine wind pressure at h = 30 ft, 30, from figure 30.5-1 5. Determine adjustment for building height and exposure, λ, from Figure 30.5-1 Adjustment factor for Exposure B is λ = 1.00 4. Determine wind pressure at h = 30 ft, 30, from Figure 6.3 5. Determine adjustment for building height and exposure, λ, from Figure 6.3 Adjustment factor for Exposure B is λ = 1.00 6. Determine adjusted wind pressure,, from Equation 30.5-1 6. Determine adjusted wind pressure,, from Equation 6-1 = λk zt 30 = λk zt 30 Wind effective area is the pressure area on the module that is distributed between four mounting clamps. Each mid-clamp takes one-quarter of the pressure and holds two modules which are equal to one-half area of one module. Wind effective area is the pressure area on the module that is distributed between four mounting clamps. Each mid-clamp takes one-quarter of the pressure and holds two modules which are equal to one-half area of one module. Area of module is 18.05 square feet. Area of module is 18.05 square feet. Effective area is ~10 square feet. Effective area is ~10 square feet. for wind speed of 115 mph and the wind effective area of 10 ft 2 : for wind speed of 90 mph and the wind effective area of 10 ft 2 :

Determining wind and snow loads for solar panels 7 ASCE 7-10 (IBC 2012) (Cont'd) ASCE 7-05 (IBC 2009) (Cont'd) Zone 1 Zone 1 Downward: +21.8 psf Downward: +13.3 psf Upward: -23.8 psf Upward: -14.6 psf = λk zt 30 = λk zt 30 P Down = 1 * 1 * 21.8 = 21.8 psf P Down = 1 * 1 * 13.3 = 13.3 psf P up = 1 * 1 * -23.8 = -23.8 psf P up = 1 * 1 * -14.6 = -14.6 psf Zone 2 Zone 2 Downward: +21.8 psf Downward: +13.3 psf Upward: -27.8 psf Upward: -17psf = λk zt 30 = λk zt 30 P Down = 1 * 1 * 21.8 = 21.8 psf P Down = 1 * 1 * 13.3 = 13.3 psf P up = 1 * 1 * -27.8 = -27.8 psf P up = 1 * 1 * -17 = -17 psf Zone 3 Downward: +21.8 psf Upward: -27.8 psf Zone 3 Downward: +13.3 psf Upward: -17psf = λk zt 30 P Down = 1 * 1 * 21.8 = 21.8 psf P up = 1 * 1 * -27.8 = -27.8 psf Steps in snow design: = λk zt 30 P Down = 1 * 1 * 13.3 = 13.3 psf P up = 1 * 1 * -17 = -17 psf Steps in snow design: 1. For sloped roof snow loads P s = C s x 2. is calculated using Equation 7.3-1 1. For sloped roof snow loads P s = C s x 2. is calculated using Equation 7.3-1 = 0.7 x C e x C t x I s x P g = 0.7 x C e x C t x I s x P g 3. When ground snow load is less than or equal to 20 psf then the minimum value is I * 20 psf. (7.3.4) 4. Find exposure factor from Table 7-2, in category B and fully exposed roof C e = 0.9 3. When ground snow load is less than or equal to 20 psf then the minimum value is I * 20 psf. (7.3.4) 4. Find exposure factor from Table 7-2, in category B and fully exposed roof C e = 0.9

Determining wind and snow loads for solar panels 8 ASCE 7-10 (IBC 2012) (Cont'd) 5. Determine thermal factor using Table 7-3, for unheated and open air structures C t = 1.2 6. Find the importance factory from Table 1.5-2 I s = 1.00 (7-10) 7. Using Section 7.4 determine C s. Using above values and θ = 30 C s = 0.73 ASCE 7-05 (IBC 2009) (Cont'd) 5. Determine thermal factor using Table 7-3, for unheated and open air structures C t = 1.2 6. Find the importance factory from Table 7-4 I s = 1.0 (7-05) 7. Using Section 7.4 determine C s. Using above values and θ = 30 C s = 0.73 = 0.7 x C e x C t x I s x P g P g 20 lbs P g is the ground snow load and cannot be used instead of the final snow load for the sloped roof in our load combinations' equations. We need to calculate the sloped roof snow load as follows: = 0.7 * 0.9 * 1.2 * 1 * 20 = 15.12 psf or 1 * 20 P s = C s x P s = 0.73 * 20 = 14.6 psf Load Combinations: (LRFD) Basic combinations Section 2.3.2, according to ASCE 7-10 structures, components and foundations shall be designed so that their design strength equals or exceeds the effects of the factored loads in the following combinations: 1) 1.4D 2) 1.2D + 1.6L + 0.5 (L r 3) 1.2D + 1.6 (L r + (L or 0.5W) 4) 1.2D + 1.0W + L + 0.5 (Lr 5) 1.2D + 1.0E + L + 0.2S 6) 0.9D + 1.0W 7) 0.9D + 1.0E = 0.7 x C e x C t x I s x P g P g 20 lbs P g is the ground snow load and cannot be used instead of the final snow load for the sloped roof in our load combinations equations. We need to calculate the sloped roof snow load as follows: = 0.7 * 0.9 * 1.2 * 1 * 20 = 15.12 psf or 1 * 20 Load Combinations: (ASD) P s = C s x P s = 0.73 * 20 = 14.6 psf Basic combinations Section 2.3, according to ASCE 7-05 loads listed herein shall be considered to act in the following combinations; whichever produces the most unfavorable effect in the building, foundation or structural member being considered. Effects of one or more loads on acting shall be considered. 1) D + F 2) D + H + F + L + T 3) D + H + F + (L r 4) D + H + F + 0.75 (L + T) + 0.75 (L r 5) D + H + F + (W or 0.7 E) 6) D + H + F + 0.75 (W or 0.7 E) +.75L +.75 (L r 7) 0.6D + W + H 8) 0.6D + 0.7E + H

Determining wind and snow loads for solar panels 9 ASCE 7-10 (IBC 2012) (Cont'd) ASCE 7-05 (IBC 2009) (Cont'd) The highest values for upward and downward pressures will govern the design. The highest values for upward and downward pressures will govern the design. Load Case 3) 1.2 * 2.59 + 1.6 (14.6) + 0.5 (21.8) = 37.4 psf Load Case 6) 2.59 + 0.75 (14.6) + 0.75 (13.3) = 23.5 psf Load Case 6) 0.9 * 2.59 + 1.0 (-27.8) = -25.7 psf Load Case 7) 0.6 (2.59) + 1.0 (-17.0) = -15.45 psf The next step is to check that the module can withstand the design loads for this two-rail mounting configuration. The designer should refer to the module installation instructions where the design loads for different mounting configurations are provided. The next step is to check that the module can withstand the design loads for this two-rail mounting configuration. The designer should refer to the module installation instructions where the design loads for different mounting configurations are provided. F min, max F min, max When two rails are supporting the module with topdown clamps, the module design capacity is: When two rails are supporting the module with topdown clamps, the module design capacity is: Downward: +113 psf Downward: +55 psf Upward: -64 psf Upward: 33 psf These values are well above the governing design loads of: These values are well above the governing design loads of: Downward: +37.4 psf Downward: +23.5 psf Upward: -25.7 psf Upward: -15.45 psf To distribute the combined loads on the module that are transferring to the rails, please refer to the Mounting User Instruction guide and ASCE 7-10 section 30.4. To distribute the combined loads on the module that are transferring to the rails, please refer to the Mounting User Instruction guide and ASCE 7-05 section 6.5.12.2.

Determining wind and snow loads for solar panels 10 Example calculations Exposure: Class B In the following example we outline how a designer should calculate the effect of wind and snow on a PV module for commercial buildings based on few assumptions and using Main Wind-force Resisting Systems design. ASCE 7-05: Section 6.5.12.4.1 ASCE 7-10: Section 30.4 Building Type: Two-story Commercial (25 feet tall) Mean height of roof: ~25.33 feet Building Shape: Gable roof with 5 pitch (1:12) System: Two Rail System; attached module at four points along the long side between 1/8 to 1/4 points as described in the SolarWorld Sunmodule User Instruction guide Example 2- Commercial Structure in Colorado: Location: Colorado Terrain: Urban, suburban, wooded, closely spaced obstructions Module area: 18.05 ft. (Reference: Sunmodule Datasheet) Module weight: 46.7 lbs (Reference: Sunmodule Datasheet) Site ground snow load (P g ): 20 psf SYMBOLS AND NOTATIONS Wind C n = New pressure coefficient to be used in determination of wind loads G = Gust effect factor I = Importance factor K d = Wind directionality factor Kz = Velocity pressure exposure coefficient evaluated at height z K zt = Topographic factor P = Design pressure to be used in determination of wind loads for buildings qh = Velocity pressure evaluated at height z = h θ = Tilt angle of the module Snow C e = Exposure factor C s = Slope factor C t = Thermal factor I = Importance factor = Snow load on flat roof P g = Ground snow load P s = Sloped roof snow load Load Combination D* = Dead load E = Earthquake load F = Load due to fluids with well-defined pressures and maximum heights H = Load due to lateral earth pressure, ground water pressure or pressure of bulk materials L = Live load L r = Roof live load R = Rain load S* = Snow load T = Self-straining load W* = Wind load * In this white paper we only use dead, snow and wind loads.

Determining wind and snow loads for solar panels 11 ASCE 7-10 (IBC 2012) ASCE 7-05 (IBC 2009) Steps in wind design: Steps in wind design: 1. Determine risk category from Table 1.5-1 1. Determine risk category from Table 1.5-1 Risk category type II Risk category type II 2. Determine the basic wind speed, V, for applicable risk category (see Figure 26.5-1 A, B, C) 2. Determine the basic wind speed, V, for applicable risk category (see Figure 6.1 A, B, C) Wind speed in Colorado is V = 115 mph Wind speed in Colorado is V = 90 mph (excluding special wind regions) (excluding special wind regions) 3. Determine wind load parameters: Wind Directionality factor, K d, see Section 26.6 Main wind-force resisting system components and cladding, K d = 0.85 3. Determine wind load parameters: Wind Directionality factor, K d, see Section 6.5.4.4 Main wind-force resisting system components and cladding, K d = 0.85 Exposure category B, C or D from Section 26.7 Exposure B Exposure category B, C or D from Section 6.5.6.3 Exposure B Topographic factor, K zt, from Section 26.8 and Figure 26.8-1 K zt = 1.0 Topographic factor, K zt, from Section 6.5.7.2 K zt = 1.0 4. Determine velocity pressure exposure coefficient, K z of K h, see Table 30.3-1 For exposure B and height of 25 ft, K z = 0.7 4. Determine velocity pressure exposure coefficient, K z of K h, see Table 6-3 For exposure B and height of 25 ft, K z = 0.7 5. Determine velocity pressure, q h, Eq. 30.3-1 q h = 0.00256 x K z x K zt x K d x V 2 5. Determine velocity pressure, q h, Eq. 6-15 q h = 0.00256 x K z x K zt x K d x V 2 x 1 6. Determine net pressure coefficient, GC p 6. Determine net pressure coefficient, GC p See Fig. 30.4-2A See Fig. 6-11B Downward: GC p = 0.3 Upward: GC p = -1.0 (zone 1) -1.8 (zone 2) -2.8 (zone 3) Downward: GC p = 0.3 Upward: GC p = -1.0 (zone 1) -1.8 (zone 2) -2.8 (zone 3)

Determining wind and snow loads for solar panels 12 ASCE 7-10 (IBC 2012) (Cont'd) ASCE 7-05 (IBC 2009) (Cont'd) 7. Calculate wind pressure, p, Eq. 30.8-1 7. Calculate wind pressure, p, Eq. 6-26 p = q h GC p p = q h GC p q h = 0.00256 x k z x k zt x k d x V 2 q h = 0.00256 x k z x k zt x k d x V 2 q h = 0.00256 * 0.7 * 1 * 0.85 * 115 2 = 20.14 psf q h = 0.00256 * 0.7 * 1 * 0.85 *90 2 = 12.34 psf p down = 20.14 * 0.3 = 6.04 psf p d = 12.34 * 0.3 = 3.7 psf psf p up = 20.14 * (-2.8) = 56 psf p u = 12.34 * (-2.8) = 34.6 psf Steps in Snow design: Steps in Snow design: 1. For sloped roof snow loads P s = C s x 2. is calculated using Equation 7.3-1 1. For sloped roof snow loads P s = C s x 2. is calculated using Equation 7.3-1 = 0.7 x C e x C t x I s x P g Pf = 0.7 x C e x C t x I s x P g 3. When ground snow load is less than or equal 20 psf then the minimum value is I * 20 psf (7.3.4) 4. Find exposure factor from Table 7-2, in category B and fully exposed roof C e = 0.9 3. When ground snow load is less than or equal 20 psf then the minimum value is I * 20 psf (7.3.4) 4. Find exposure factor from Table 7-2, in category B and fully exposed roof C e = 0.9 5. Determine Thermal factor using Table 7-3, for unheated and open air structures C t = 1.2 5. Determine Thermal factor using Table 7-3, for unheated and open air structures C t = 1.2 6. Find the importance factory from Table 1.5-2 I s = 1.00 (7-10) 6. Find the importance factory from Table 7-4 I s = 1.0 (7-05) 7. Using Section 7.4 determine C s. Using above values and θ = 5 C s =1.0 7. Using section 7.4 determine C s. Using above values and θ = 5 C s =1.0 = 0.7 x C e x C t x I s x P g = 0.7 C e C t I s P g

Determining wind and snow loads for solar panels 13 ASCE 7-10 (IBC 2012) (Cont'd) ASCE 7-05 (IBC 2009) (Cont'd) P g 20 lbs P g 20 lbs P g is the ground snow load and cannot be used instead of the final snow load for the sloped roof in our load combinations equations. We need to calculate the sloped roof snow load as follows: P g is the ground snow load and cannot be used instead of the final snow load for the sloped roof in our load combinations equations. We need to calculate the sloped roof snow load as follows: = 0.7 * 0.9 * 1.2 * 1 * 20 = 15.12 psf or 1 * 20 = 0.7 * 0.9 * 1.2 * 1 * 20 = 15.12 psf or 1 * 20 P s = C s x P s = C s x To find out the effect of snow load perpendicular to the plane of module we multiply the P s value by COS (θ). To find out the effect of snow load perpendicular to the plane of module we multiply the P s value by COS (θ). P s = 1 * 20 * COS (5 ) = 19.9 psf P s = 1 * 20 * COS (5 ) = 19.9 psf Load combinations: (LRFD) Load Combinations: (ASD) Basic combinations section 2.3.2, according to ASCE 7-10 structures, components and foundations shall be designed so that their design strength equals or exceeds the effects of the factored loads in following combinations: Basic combinations section 2.3.2, according to ASCE 7-05 loads listed herein shall be considered to act in the following combinations; whichever produces the most unfavorable effect in the building, foundation or structural member being considered. Effects of one or more loads on acting shall be considered. 1) 1.4D 2) 1.2D + 1.6L + 0.5 (L r 3) 1.2D + 1.6 (L r + (L or 0.5W) 4) 1.2D + 1.0W + L + 0.5 (L r 5) 1.2D + 1.0E + L + 0.2S 6) 0.9D + 1.0W 7) 0.9D + 1.0E 1) D + F 2) D + H + F + L + T 3) D + H + F + (L r 4) D + H + F + 0.75 (L + T) + 0.75 (L r 5) D + H + F + (W or 0.7E) 6) D + H + F + 0.75 (W OR 0.7E) +.75L +.75 (L r 7) 0.6D + W + H 8) 0.6D + 0.7E + H The highest values for upward and downward pressures will govern the design. The highest values for upward and downward pressures will govern the design.

Determining wind and snow loads for solar panels 14 ASCE 7-10 (IBC 2012) (Cont'd) ASCE 7-05 (IBC 2009) (Cont'd) Load Case 3) Load Case 6) 1.2 * 2.59 + 1.6 (19.9) + 0.5 (6.04) = 38 psf 2.59 + 0.75 (19.9) + 0.75 (3.7) = 20.3 psf Load Case 6) Load Case 7) 0.9 * 2.59 + 1.0 (-56) = -53.7 psf 0.6 (2.59) + 1.0 (-34.6) = -33 psf The next step is to check that the module can withstand the design loads for this two-rail mounting configuration. The designer should refer to the module installation instructions where the design loads for different mounting configurations are provided. The next step is to check that the module can withstand the design loads for this two-rail mounting configuration. The designer should refer to the module installation instructions where the design loads for different mounting configurations are provided. F min, max F min, max For the case of two rails simply supporting the module with top-down clamps, the module design capacity is: For the case of two rails simply supporting the module with top-down clamps, the module design capacity is: Downward: +113 psf Downward: +55 psf Upward: -64 psf Upward: -33 psf These values are above the governing design loads of: These values are above the governing design loads of: Downward: +38 psf Downward: +20.3 psf Upward: -53.7 psf Upward: -33 psf To distribute the combined loads which are transferring to the rails please refer to the Mounting User Instruction and ASCE 7-10 section 30.4. To distribute the combined loads which are transferring to the rails please refer to the Mounting User Instruction and ASCE 7.05 section 6.5.12.2.

Determining wind and snow loads for solar panels SW-02-5156US-MEC 04-2013 15 As this white paper illustrates, SolarWorld Sunmodules easily meet many high wind and snow load requirements within the United States and therefore are ideal for installation in most climates. The ability to meet these requirements is essential when designing solar systems that are expected to perform in various weather conditions for at least 25 years. As America s solar leader for over 35 years, SolarWorld s quality standards are unmatched in the industry. Unlike most other solar manufacturers in the market today, our systems have proven performance in real world conditions for over 25 years. References 1. Minimum design loads for buildings and other structures. Reston, VA: American Society of Civil Engineers/ Structural Engineering Institute, 2006. Print. 2. Minimum design loads for buildings and other structures. Reston, Va.: American Society of Civil Engineers :, 2010. Print. 3. International building code 2009. Country Club Hills, Ill.: International Code Council, 2009. Print. 4. International building code 2006. New Jersey ed. Country Club Hills, IL: The Council, 2007. Print.

ENGINEERED POWER SOLUTIONS MATTHEW B. GILLISS, PROFESSIONAL ENGINEER 879 SYCAMORE CANYON RD. PASO ROBLES, CA 93446 (805) 423-1326 STRUCTURAL LETTER OF APPROVAL Date: Project: EPS Job Number: To: From: December 30, 2012 Solar Module Design Loads Methodology Review 12-SWD003 Amir Sheikh SolarWorld Americas (SolarWorld) 4650 Adohr Lane Camarillo, CA 93012 Matthew Gilliss Engineered Power Solutions (EPS) 12/31/14 At the request of SolarWorld, Engineered Power Solutions (EPS) has reviewed the design methodology presented in SolarWorld s White Paper titled: Determining Wind and Snow Loads for Solar Panels (Version 7). The paper presents the recommended ed design methodology for determining the code prescribed wind and snow loads for solar modules mounted on and flush to a roof surface in accordance with either the 2009 (and 2006) Internationalal Building Code (IBC) - which references the 2005 Minimum Design Loads for Buildings and Other Structures by the American Society of Civil Engineers (ASCE 7-05), or the 2012 IBC which references ASCE 7- -10. EPS has found that the design methodology and examples presented in this paper are consistent with the design intentionsions of each said building code. This letter is in approval of the general design methodology for flush roof mounted solar modules only as discussed in the referenced paper.. It is the responsibility of the project engineer of record to address the site specific loading conditions for each project. Please note that the industry recommended ended design methodology for roof mounted solar systems has continually changed over recent years as new studies are published. Because of this, EPS recommends periodically reviewing the stated methodology to ensure it matches with the most current code requirements and industry recommendations. Please feel free to contact me with any questions. Thank you. Sincerely, Matthew B. Gilliss, P.E., LEED AP Engineered Power Solutions Letter of Approval SolarWorld Design Loads Methodology Review Page 1