Individual_module_po.. - the Midwest Solar Training Network

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					  PV Module Power Optimization

Individual module (MPPT) maximizing power production
Use Policy
   This material was developed as a result of a partnership
    with the Midwest Renewable Energy Association (MREA)
    and Aur j Beck (da energy mon).
   This material was developed by the Midwest Solar
    Training Network with funding from U.S. Department of
    Energy as part of the grant DE-EE0002089.001
   All materials in this presentation are designed expressly
    for educational use. They may not be used for publication
    or commercial advertisement.
Contributors, co-authors

   Collaborator: Aur J Beck, 'da energy mon', chief tech
    for Advanced Energy Solutions install network (the
    Green Geek Squad)

Xandex- Kevin Peebles
Solar Edge
Solar Pro magazine
The Root Cellar-John Root
                                                There is very little to
                                                  differentiate between
                                                  modules anymore.
                                                Companies are now trying to
                                                  differentiate themselves
                                                  from other module
                                                One of the new ways is to
                                                  have a power optimizer
                                                  replace the junction box on
                                                  the back of the PV module.

Source: Aur J Beck. Picture of Exeltech inverter taken at the Midwest Renewable Energy Fair 2010
Executive Summary
Individual module Maximum Power Point Tracking
  (MPPT) power optimizers work on maximizing power
  production at the individual module level instead of
  on a whole central inverter level.

Broad Categories of these products;
*Module MPPT- divided into DC to AC and DC to DC
*Shade Mitigation- divided up to just put on shaded area or have
  to put on all modules

*   Note: I was having a real hard time trying to figure out how to title or what category to
    put this new line of great products that eliminate a few age old problems. Every
    product focuses on different aspect of these problems. So far no product does all of
    these things.
Source: Aur 'da energymon' & Solar Pro magazine
                          Installer Benefits
                 Every product focuses on different aspects of these.
                      So far no product does all of these things.

Module mismatch losses.
                                 Strings of different length
                            Modules on multiple roof facets
                           Modules with different power ratings
                            Modules of different technologies
Shade mitigation. There are two kinds (have to put on all modules in a system or just
   shaded area).
Warranty Issues. Under performing modules or bad ones. Also how do you replace a
   bad or damaged module if they are no longer made.
Increased Energy yield. This one is so far just a claim by the manufacturers but good
Safety. No power output from the module when grid is down
   Source: Solar Pro Magazine August/September 2010
                          Installer Benefits
                 Every product focuses on different aspects of these.
                      So far no product does all of these things.

Individual module-level data monitoring. This is huge (see warranty), maintenance,
   and for marketing.
Simplifying system design. No more string sizing
Module integration. Exeltech has already done this but all manufacturers claim to be
   in negotiations with module manufacturers
Cost reductions. This one is so far just a claim by the manufacturers although you can
   have Incremental growth capability - no need to purchase many expensive
   modules at one time.
Reliability: Inverters with 5- to 15-year warranties have to be replaced multiple times
   during the life of a PV system.

   Source: Solar Pro Magazine August/September 2010
                             What is MPPT?
                      Explanation of maximum power point tracking

A maximum power point tracker (or MPPT) is a high efficiency DC to DC converter. It extracts
               additional power from your PV array, under certain conditions.

       PV modules have the unique characteristic of increasing current under short circuit (Isc) and
                              increasing voltage under open circuit (Voc).

                   MPPT uses high speed switches to take advantage of this uniqueness.

                             MPPT was originally used in grid intertie inverters.

   As high speed switches became faster and more reliable and smaller, MPPT started to be used in PV
                                           charge controls.

                       And now they are being used for individual PV module MPPT.

Tech explanation: MPPT manipulate (using solid state high speed switching devices including transistors
   and thyristors) the load or output voltage of an array in order to maintain at or near the maximum
                         power point under changing temperature and irradiance.

  Source: &
                               What is MPPT?
                       Explanation of maximum power point tracking

        Maximizes the performance of the PV array by allowing the modules to
operate at the voltage which produces the most power. The increased power produced is
    similar to having a larger PV array. The MPP (Maximum power point) curve of a solar
     module is knee shaped and the point at which the power is at it's maximum is where the
           voltage multiplied by the current gives the highest output (Measured in Watts).

The voltage of a solar module varies with temperature and the amount of sunshine falling on it so
                                 the maximum power point moves.

    Source: ,
 How does Shade Mitigation work?

                                       Performs localized Maximum Power Point Tracking
                                               (MPPT) at the panel substring level

                                      Provides power to the string at the optimum current
                                           level so unshaded panels are not degraded

                                             Harvests power that would have been lost

Source: Sun Mizer Educator presentation January 2010
Source:   08/08/10
                       Effects of Shading



                              Unshaded Modules are not degraded!
Source: Sun Mizer Educator presentation January 2010
          Explanation of some products
                         Shading Optimization Example

Dc-to-dc optimizer. System will produce more power when modules experience unavoidable
                    Shaded modules do not impact the power output of the un-shaded modules
                                   You get more power from the shaded module
                           Install a larger system and produce more power!
                         Modules are added at a fraction of the cost due to fixed overhead
                                         Revenue and profit are increased

    Source: Sun Mizer Educator presentation January 2010
          Explanation of some products
                                    Dc-to-dc optimizer

Dc-to-dc optimizer. A power electronic device with a dc output that is designed to maximize the
 output of individual PV modules or strings belongs to the dc-to-dc optimizer category. These units
 are available in a wide variety of flavors: for series or parallel circuit architectures, for example, or
     utilizing a full buck/boost design versus a buck-only or boost-only or even a transformerless
 design. In some cases, like the Xandex SunMizer, these can be selectively deployed at a module
  level. In other cases, as with the SolarMagic power optimizers, they can be deployed as needed
  per string. String sizing protocols also vary by product and manufacturer. With dc-to-dc products
   the PV source and output circuits are still dc circuits all the way back to the centralized inverter.

   Source: &
       Explanation of some products
                                     Two-stage inverter.

Two-stage inverter. An increasing number of companies have proprietary dc-to-dc
 optimizers that work with proprietary centralized inverters. For example, the first suite
of products to be offered by SolarEdge also features a two-stage inverter approach. In
 this case module-level dc-to-dc optimization is coupled with centralized inversion for
residential and small commercial applications. In the case of SolarEdge products, the
first stage (the dc to dc optimizer) performs MPP tracking and dc-to-dc conversion; the
              second stage (the inverter) inverts dc to ac and is centralized.
           Explanation of some products

 Microinverter. The Microinverter attaches to the racking beneath each solar module and converts
   DC power to grid-compliant AC power. This power conditioning unit is designed to convert the dc
       output from a single PV module to grid intertie ac electricity (either 120 or 240Vac so far).
          Microinverters are installed in parallel to build an appropriately sized branch circuit.
One inverter per module makes a system truly modular. If one microinverter fails, the rest continue to
     operate as usual. Also, if a microinverter is damaged or fails, it can be replaced during routine
      maintenance or when convenient, further reducing maintenance costs. The main difference
     between microinverters and dc-to-dc optimizers, of course, is that microinverters eliminate dc
        circuits altogether or limit the extent of the dc circuits to individual module output wiring.
  Tech Note:Disadvantage is it is now lower voltage (either 120 or 240Vac compared to the 350 to
    550Vdc typical in whole systems). Possible Voltage drop. Mounted on roof so high temperature
     Photo Source: &
           Explanation of some products
                                             Ac module

Ac module. A PV module with an embedded or integrated microinverter is often referred to as
    an alternating-current photovoltaic module or ac module. The NEC defines an ac module as a
      “complete, environmentally protected unit” that consists of both solar cells and an inverter.
   According to the National Electrical Code Handbook, an ac PV module has “no accessible, field-
  installed dc wiring.” When a microinverter is embedded in place of a module’s junction box, there
    is no accessible dc wiring. In this case, the unit could be listed as a complete assembly, an ac
   module. The unit might be field serviceable, meaning the embedded micro could be replaced in
  the field. Any assembly that comes short of this level of integration— anything with accessible dc
     wiring, in other words—is technically a listed PV module with a separately listed microinverter
                                          attached to its frame.

    Photo Source: Aur J Beck. Picture of Exeltech inverter taken at the Midwest Renewable Energy Fair 2010 &
          Explanation of some products
                                   Data monitoring

The majority of these products include individual module-level data monitoring. Some
    like Tigo & Enphase is very much focused on the data monitoring aspect. A great
   example is a system installed and due to data monitoring we were was able to find
     out within two months that 3 modules in the system were under preforming by at
                  least 15% and they were replaced as a warranty issue.

Photo: SolarPro magazine August/September 2010
Photo: SolarPro magazine August/September 2010
Information and/or works cited

             Here are some manufacturers:
       ExcelTech / 817.595.4969 /
       eIQ Energy / 408.533.8560 /
  Enphase Energy / 877.797.4743 /
 National Semiconductor / 877.765.6244 /
    Satcon Technology / 888.728.2664 /
 SolarBridge Tech / 512.637.6860 /
        SolarEdge / 650.320.7695 /
      Tigo Energy / 408.364.0150 /
       Xandex / 707.763.7799 /
Works Cited
   List of sources that appear at the bottom of each slide as a list of
    references and works cited.

1. Solar Pro Magazine August/September 2010
2. Sunmizer presentation
3. Panel discussion at AEE Conference Feb 2010
4. The Root Cellar-John Root
5. MPPT:,, ,

6. &
7. Photo Source: &
8. Aur 'da energy mon' chief tech,

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