Do solar PV modules hold up to hail?

Discussion in 'Frequently Asked Questions' started by scott, Jan 2, 2015.

  1. scott

    scott Administrator Staff Member

    In a solar power system, only the modules are typically exposed to hail. All other equipment should be tucked below the modules or mounted in less exposed locations. Here in Colorado we have hail storms every year. It is common for us to be contacted to remove a PV system so that the hail damaged roof can be replaced. We have yet to come across a system with hail damage to the modules themselves.

    It is now common for most permitting authorities to require that solar modules are listed to UL1703 which requires PV modules to be impacted by steel spheres of 2 inch diameter that generate impact energy of 5 foot pounds. The glass on the surface of the modules are tempered and fairly flexible. Additionally, we find that it is unusual to have the hail stone impact the module exactly perpendicular and more commonly at a glancing blow.

    While it is very uncommon for a solar PV module manufacture to cover hail damage under its warranty, we find that most all home insurance companies with cover the modules under your home owners insurance policy. We highly recommend contacting your insurance agent as soon as the system is installed to be sure the system is registered in their systems and covered under the policy.

    One important note here is that we have been discussing physical damage to the module. There are studies out there that show how a module can be impacted by hail, and while the surface will show no damage, the electrical characteristics of the cell can change and production be reduced. This can be hard to prove after the fact (or even notice in the first place) and is another reason that we HIGHLY recommend a monitoring system on all Solar PV power systems.
     
  2. scott

    scott Administrator Staff Member

    Some additional details for those researching hail damage:


    ASTM International Standards
    Both standards are based on measuring the velocity of pneumatically launched ice spheres with a ballistic timer.
    ASTM E8224. Determining Resistance of Solar Collector Covers to Hail by Impact With Propelled Ice Balls
    (physical damage to the cover of solar collectors)
    ASTM E1038-05. Determining Resistance of Photovoltaic Modules to Hail by Impact With Propelled Ice Balls
    (measures variation in electrical output of the PV modules before and after impact)


    Factory Mutual Global
    For both the SH and MH tests, the minimum rating required by FM Approvals is Class 2, indicated by a PV module showing no signs of cracking or splitting, misaligned external surfaces, or rupture when examined closely under 10x magnification. This test is applied to both weathered and unweathered modules.

    FM 44766, Approval Standard for Flexible Photovoltaic Modules
    FM 44787, Approval Standard for Rigid Photovoltaic Modules

    Class MH. Moderate Hail Test
    MH test involves dropping the steel spheres from a height of 81 inches, generating an impact energy of approximately 8 lbf over the 2-inch impact area. According to data from the National Bureau of Standards (NBS), as reported in “Hail Resistance of Roofing Products,” BSS #238 this is equivalent to impact from ice spheres approximately 1.50 in.

    Class SH. Severe Hail Damage Resistance Test
    Class 1-SH ratings involves dropping the steel sphere from a height of 141.5 inches, generating an
    impact energy of approximately 14 lbf over the 2-inch impact area, equivalent to impact from ice spheres approximately 1.75" in diameter. According to data from the National Bureau of Standards (NBS), as reported in “Hail Resistance of Roofing Products,” BSS #238 this is equivalent to impact from ice spheres approximately 1.75"

    Underwriters Laboratory (UL) Standard 1703

    Requires PV panels to be impacted with steel spheres of 2.0-in. diameter that generate impact energy of 5 foot-pounds. According to NBS, this is equivalent to the impact from an ice sphere with a diameter of between 1.25 and 1.50 in. In North America, these tests are a 5 ft·lbs impact of a 2 inch diameter ball of 1.18 lbs that’s dropped at a distance of 51 inches- no parts of the solar panel can be damaged to acquire this label.


    International Electrotechnical Commission
    The European quality certificate specifically for hail is IEC 61215. Solar panels with this label were shot with frozen ice balls at varying sizes and speeds from an air gun.
     
    Last edited: Jan 14, 2015
  3. Landon

    Landon Member

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    We don't get hail frequently here so I am not real concerned, although it's good to hear that it's unlikely to damage the panels. How resistant to freezing are the panels? I know that they can withstand freezing temperatures but can they hold up to it for an extended time period?
     
  4. scott

    scott Administrator Staff Member

    You are right to not be too concerned with hail. We have rarely (if ever) seen a module broken from hail. As for freezing, the main concern is the thermal cycling. Since modules are located in direct sun, it is pretty common to experience sub freezing conditions at night and rapidly heat up when the sun comes out. This is worsened by damp conditions and moisture buildup.

    This thermal cycling can take its toll on the construction of the modules themselves over time, though one overlooked aspect is the diodes. Some lesser quality diodes can fail due to the thermal cycling, unfortunately the temperature effects on diodes isn't always tested as heavily as the modules themselves.

    In our experience, I have not seen many modules that seem to be suffering purely from thermal cycling. It can be hard for a field technician to say though. The damage is generally a linear process that gets worse over time. If you are inspecting a old, worse for wear module, it could be hard to pinpoint exactly what has taken its toll on the module exposed to the elements for all this time.

    If you purchase a higher quality module that is well constructed, I would not be concerned about thermal cycling. I would not be surprised if a lower quality module were to get moisture leaking in and over time begin to delaminate.

    Here is a list of some standards that are used for testing if you care to do more research. This was found at Envirotronics

    Humidity Freeze Test
    +85°C ± 2°C , 85% ± 5% RH / -40°C ± 3°C
    To determine the ability of the module to withstand the effects of high temperature and humidity followed by sub-zero temperatures.
    IEC61215, 10.12 (JIS C-8990)
    IEC61646, 10.12 (JIS C-8991)

    Thermal Cycling Test
    -40°C / +90°C
    To make an assessment of the module's ability to withstand exposure to several environmental conditions during transportation and/or storage.
    JIS C-8917
    JIS C-8938

    -40°C / +85°C
    To make an assessment of the module's ability to withstand exposure to several environmental conditions during transportation and/or storage.
    IEC61215, 10.11 (JIS C-8990)
    IEC61646, 10.11 (JIS C-8991)

    Damp Heat Test
    +85°C ± 2°C , 85% ± 5% RH
    To evaluate the ability of the module for use and/or storage under high temperature and humidity.
    IEC60068-2-78 (JID C-8917, C-8938, C-60068-2-3)

    To determine the ability of the module to withstand the effects of long-term penetration of humidity.
    IEC61215, 10.13 (JIS C-8990)
    IEC61646, 10.13 (JIS C-8991)

    Temperature/Humidity Cycling Test
    +85°C ± 2°C , 85% ± 5% RH / -40°C ± 3°C
    To determine the deterioration level for use and/or storage in short time under condition of temperature change in high relative humidity.
    JIS C-8917
    JIS C-8638

    Low Temperature Sub-Cycle Test
    +65°C ± 2°C , 93% ± 3% RH /+25°C ± 2°C , 80-96% RH / -10°C ± 3°C
    IEC60068-2-38, 6.3.1 (JIS C-8962)

    Temperature Test
    +85°C ± 2°C
    To evaluate the ability of the module for use and/or storage under high temperature
    IEC60068-2-2, (JIS C-8917, C-60068-2-2)
    IEC60068-2-2, (JIS C-8938, C-60068-2-2)
     
  5. garrycolins

    garrycolins New Member

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    Last edited: Aug 30, 2020
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