Difference between revisions of "Load and solar resource comparison"

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The design process for an off-grid PV system should use conservative, worst-case values to ensure that the system is capable of meeting the energy needs of users throughout the year. There are many locations that have a significant seasonal variance in [[Weather and solar resource evaluation|solar resource]] due to poor weather or latitude. Many off-grid PV systems will see a significant variance in [[Load evaluation|how loads are used throughout the year]], especially in locations that are only seasonally occupied. These two different factors - load usage vs. solar resource - make it important to determine what month to use in the system design as the worst-case scenario. An analysis of loads and usage could be performed on a monthly basis, but the most drastic shift in usage likely occurs between the major seasons in a given region meaning two to four times per year. Determining the worst-case month can be done using a simple table and a quick calculation. The values and calculation can be performed in Wh or kWh - the ratio is what is important.
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Example of average monthly insolation for Puerto Maldonado, Madre de Dios, Peru in the Amazon rainforest with a tilt of 12 degrees of PV module tilt. Despite being relatively near the equator there is significant season variation. <ref name="pvwatts"> PVWatts Calculator https://pvwatts.nrel.gov/pvwatts.php</ref>
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{| class="wikitable" border=1
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!Month
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!Average daily insolation
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!Total average monthly Wh requirement
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!Ratio
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|-
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|January
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|6.06 kWh/m²
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|2.00kWh
 +
|.330
 +
|-
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|February
 +
|6.32 kWh/m²
 +
|2.00kWh
 +
|.316
 +
|-
 +
|March
 +
|6.49 kWh/m²
 +
|2.00kWh
 +
|.308
 +
|-
 +
|April
 +
|6.42 kWh/m²
 +
|2.00kWh
 +
|.311
 +
|-
 +
|May
 +
|5.00 kWh/m²
 +
|3.00kWh
 +
|.600
 +
|-
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|June
 +
|3.75 kWh/m²
 +
|3.00kWh
 +
|.800
 +
|-
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|July
 +
|3.39 kWh/m²
 +
|3.00kWh
 +
|.885
 +
|-
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|August
 +
|3.69 kWh/m²
 +
|3.00kWh
 +
|.813
 +
|-
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|September
 +
|4.21 kWh/m²
 +
|3.00kWh
 +
|.713
 +
|-
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|October
 +
|5.17 kWh/m²
 +
|3.00kWh
 +
|.580
 +
|-
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|November
 +
|5.27 kWh/m²
 +
|2.00kWh
 +
|.380
 +
|-
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|December
 +
|5.60 kWh/m²
 +
|2.00kWh
 +
|.357
 +
|}

Revision as of 07:03, 12 November 2020

The design process for an off-grid PV system should use conservative, worst-case values to ensure that the system is capable of meeting the energy needs of users throughout the year. There are many locations that have a significant seasonal variance in solar resource due to poor weather or latitude. Many off-grid PV systems will see a significant variance in how loads are used throughout the year, especially in locations that are only seasonally occupied. These two different factors - load usage vs. solar resource - make it important to determine what month to use in the system design as the worst-case scenario. An analysis of loads and usage could be performed on a monthly basis, but the most drastic shift in usage likely occurs between the major seasons in a given region meaning two to four times per year. Determining the worst-case month can be done using a simple table and a quick calculation. The values and calculation can be performed in Wh or kWh - the ratio is what is important.

Example of average monthly insolation for Puerto Maldonado, Madre de Dios, Peru in the Amazon rainforest with a tilt of 12 degrees of PV module tilt. Despite being relatively near the equator there is significant season variation. [1]

Month Average daily insolation Total average monthly Wh requirement Ratio
January 6.06 kWh/m² 2.00kWh .330
February 6.32 kWh/m² 2.00kWh .316
March 6.49 kWh/m² 2.00kWh .308
April 6.42 kWh/m² 2.00kWh .311
May 5.00 kWh/m² 3.00kWh .600
June 3.75 kWh/m² 3.00kWh .800
July 3.39 kWh/m² 3.00kWh .885
August 3.69 kWh/m² 3.00kWh .813
September 4.21 kWh/m² 3.00kWh .713
October 5.17 kWh/m² 3.00kWh .580
November 5.27 kWh/m² 2.00kWh .380
December 5.60 kWh/m² 2.00kWh .357
  1. ↑ PVWatts Calculator https://pvwatts.nrel.gov/pvwatts.php
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