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. 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 insolation:
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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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*Design insolation
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*Average daily Watt-hours required
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*Design daily 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.
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*July (highlighted in red) has the worst ratio of solar resource relative to energy requirement throughout the year. The average insolation value (3.39 kWh/m²) and Average daily Watt-hours required (3000Wh) from this month should be used in the design.
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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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![[Weather and solar resource evaluation#Solar resource (insolation)|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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![[Load evaluation#Average daily Watt-hours required|Average daily Watt-hours required]]
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![[Special:MyLanguage/Load evaluation#Total average daily energy demand|Total average daily energy demand (Wh)]]
 
!Ratio
 
!Ratio
 
|-
 
|-
 
|January
 
|January
−
|6.06 kWh/m²
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|
−
|2000Wh
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|
−
|330
+
|
 
|-
 
|-
 
|February
 
|February
−
|6.32 kWh/m²
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|
−
|2000Wh
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|
−
|316
+
|
 
|-
 
|-
 
|March
 
|March
−
|6.49 kWh/m²
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|
−
|2000Wh
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|
−
|308
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|
 
|-
 
|-
 
|April
 
|April
−
|6.42 kWh/m²
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|
−
|2000Wh
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|
−
|311
+
|
 
|-
 
|-
 
|May
 
|May
−
|5.00 kWh/m²
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|
−
|2000Wh
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|
−
|600
+
|
 
|-
 
|-
 
|June
 
|June
−
|3.75 kWh/m²
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|
−
|3000Wh
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|
−
|800
+
|
−
|- style="background-color:#F08080;"
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|-
 
|July
 
|July
−
|3.39 kWh/m²
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|
−
|3000Wh
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|
−
|885
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|
 
|-
 
|-
 
|August
 
|August
−
|3.69 kWh/m²
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|
−
|3000Wh
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|
−
|813
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|
 
|-
 
|-
 
|September
 
|September
−
|4.21 kWh/m²
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|
−
|3000Wh
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|
−
|713
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|
 
|-
 
|-
 
|October
 
|October
−
|5.17 kWh/m²
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|
−
|3000Wh
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|
−
|580
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|
 
|-
 
|-
 
|November
 
|November
−
|5.27 kWh/m²
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|
−
|2000Wh
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|
−
|380
+
|
 
|-
 
|-
 
|December
 
|December
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|5.60 kWh/m²
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|
−
|2000Wh
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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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*'''[[Load evaluation#Average daily Watt-hours required|Average daily Watt-hours required]]''' from load evaluation.
 
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*'''Ratio =''' Average daily Watt-hours required ÷ Average daily insolation
 
  
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==Notes/references==
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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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<!--T:7-->
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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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<!--T:8-->
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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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<!--T:10-->
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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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<!--T:11-->
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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 15:19, 1 April 2021

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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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