Difference between revisions of "Load and solar resource comparison"

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[[Category:Site evaluation]]
 
[[Category:Site evaluation]]
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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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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 [[Special:MyLanguage/Weather and solar resource evaluation|solar resource]] due to poor weather or latitude. Many off-grid PV systems will see a significant variance in [[Special:MyLanguage/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 times per year. Determining the worst-case month can be done using a simple table and a quick calculation using [[Special:MyLanguage/Weather and solar resource evaluation|monthly insolation data]] and [[Special:MyLanguage/Load evaluation|Average daily Wh estimates]] for the two different time periods October - March and April - September. The two following values used for the design should be chosen from the month with the highest ratio of average daily watt-hours relative to average monthly insolation:
  
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'''Example 1:''' A potential off-grid PV system in Puerto Maldonado, Madre de Dios, Peru in the Amazon rainforest with [[PV module|PV source]] with a tilt of 12 degrees of PV module tilt. Solar resource data shows that despite being relatively near the equator there is significant monthly variation due to seasonal rains.<ref name="pvwatts"> PVWatts Calculator https://pvwatts.nrel.gov/pvwatts.php</ref> The load evaluation shows that loads will be used more frequently during the rainy season, which is common. July (highlighted in red) has the worst ratio of solar resource relative to energy requirement throughout the year. The solar resource and loads from this month should be used in the design.
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*Design daily insolation
  
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*Design daily watt-hours required
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====Step 1: Determine monthly ratio of energy demand to solar resource==== <!--T:4-->
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{| class="wikitable" border=1
 
{| class="wikitable" border=1
 
!Month
 
!Month
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!Average daily insolation
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![[Special:MyLanguage/Weather and solar resource evaluation#Solar resource (insolation)|Average monthly insolation (kWh/m²)]]
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!Total average monthly Wh requirement
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![[Special:MyLanguage/Load evaluation#Total average daily energy demand|Total average daily energy demand (Wh)]]
 
!Ratio
 
!Ratio
 
|-
 
|-
 
|January
 
|January
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|6.06 kWh/m²
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|
−
|2.00kWh
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|
−
|.330
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|
 
|-
 
|-
 
|February
 
|February
−
|6.32 kWh/m²
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|
−
|2.00kWh
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|
−
|.316
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|
 
|-
 
|-
 
|March
 
|March
−
|6.49 kWh/m²
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|
−
|2.00kWh
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|
−
|.308
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|
 
|-
 
|-
 
|April
 
|April
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|6.42 kWh/m²
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|
−
|2.00kWh
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|
−
|.311
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|
 
|-
 
|-
 
|May
 
|May
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|5.00 kWh/m²
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|
−
|3.00kWh
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|
−
|.600
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|
 
|-
 
|-
 
|June
 
|June
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|3.75 kWh/m²
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|
−
|3.00kWh
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|
−
|.800
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|
−
|- style="background-color:#F08080;"
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|-
 
|July
 
|July
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|3.39 kWh/m²
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|
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|3.00kWh
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|
−
|.885
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|
 
|-
 
|-
 
|August
 
|August
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|3.69 kWh/m²
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|
−
|3.00kWh
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|
−
|.813
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|
 
|-
 
|-
 
|September
 
|September
−
|4.21 kWh/m²
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|
−
|3.00kWh
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|
−
|.713
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|
 
|-
 
|-
 
|October
 
|October
−
|5.17 kWh/m²
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|
−
|3.00kWh
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|
−
|.580
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|
 
|-
 
|-
 
|November
 
|November
−
|5.27 kWh/m²
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|
−
|2.00kWh
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|
−
|.380
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|
 
|-
 
|-
 
|December
 
|December
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|5.60 kWh/m²
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|
−
|2.00kWh
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|
−
|.357
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|
 
|}
 
|}
 
*'''Month:''' The month of the year.
 
*'''Month:''' The month of the year.
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*'''Average daily insolation:''' Solar resource data obtained for the location from [[Weather and solar resource data sources]].
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*'''Total average daily Wh requirement =''' [[Load evaluation#DC load evaluation|Total average daily DC Watt-hours]] +  [[Load evaluation#AC load evaluation|Total average daily AC Watt-hours]]
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*'''Ratio =''' Total average monthly Wh requirement ÷ Average daily insolation
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*'''Average monthly insolation:''' Solar resource data obtained for the location from [[Special:MyLanguage/Weather and solar resource evaluation|Weather and solar resource evaluation]].
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==Notes/references==
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*'''[[Special:MyLanguage/Load evaluation#Total average daily energy demand|Total average daily energy demand]]''' for the month from the load evaluation.
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*'''Ratio =''' Total average daily energy demand ÷ Average monthly insolation
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====Step 2: Determine design values==== <!--T:9-->
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{| class="wikitable" border=1 style="width: 80%;"
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! style="width: 20%"|Design daily insolation  
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! style="text-align:left;"| = Average monthly insolation (kWh/m²) from month with the highest ratio ÷ 30
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|}
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{| class="wikitable" border=1 style="width: 80%;"
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! style="width: 20%"|Design daily watt-hours required
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! style="text-align:left;"| = Total average daily energy demand (Wh) from month with the highest ratio
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|}
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==Notes/references== <!--T:12-->
 
<references/>
 
<references/>
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Latest revision as of 14:19, 1 April 2021

Other languages:
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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 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 times per year. Determining the worst-case month can be done using a simple table and a quick calculation using monthly insolation data and Average daily Wh estimates for the two different time periods October - March and April - September. The two following values used for the design should be chosen from the month with the highest ratio of average daily watt-hours relative to average monthly insolation:

  • Design daily insolation
  • Design daily watt-hours required

Step 1: Determine monthly ratio of energy demand to solar resource

Month Average monthly insolation (kWh/m²) Total average daily energy demand (Wh) Ratio
January
February
March
April
May
June
July
August
September
October
November
December
  • Month: The month of the year.
  • Ratio = Total average daily energy demand ÷ Average monthly insolation

Step 2: Determine design values

Design daily insolation = Average monthly insolation (kWh/m²) from month with the highest ratio ÷ 30
Design daily watt-hours required = Total average daily energy demand (Wh) from month with the highest ratio

Notes/references

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