Difference between revisions of "Load and solar resource comparison"
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[[Category:Site evaluation]] | [[Category:Site evaluation]] | ||
| − | 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 times per year. Determining the worst-case month can be done using a simple table and a quick calculation using [[Weather and solar resource evaluation|monthly insolation data]] and [[Load evaluation|Average daily Wh estimates]] for the two different time periods October - March and April - September | + | 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 times per year. Determining the worst-case month can be done using a simple table and a quick calculation using [[Weather and solar resource evaluation|monthly insolation data]] and [[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: |
*Design daily insolation | *Design daily insolation | ||
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{| class="wikitable" border=1 | {| class="wikitable" border=1 | ||
!Month | !Month | ||
| − | ![[Weather and solar resource evaluation#Solar resource (insolation)|Average monthly insolation]] | + | ![[Weather and solar resource evaluation#Solar resource (insolation)|Average monthly insolation (kWh/m²)]] |
| − | ![[Load evaluation#Total average daily energy demand|Total average daily energy demand]] | + | ![[Load evaluation#Total average daily energy demand|Total average daily energy demand (Wh)]] |
!Ratio | !Ratio | ||
|- | |- | ||
| Line 81: | Line 81: | ||
{| class="wikitable" border=1 style="width: 80%;" | {| class="wikitable" border=1 style="width: 80%;" | ||
| − | ! style="width: 20%"|Design daily insolation | + | ! style="width: 20%"|Design daily insolation |
| − | ! style="text-align:left;"| = Average monthly insolation from month with the highest ratio ÷ 30 | + | ! style="text-align:left;"| = Average monthly insolation (kWh/m²) from month with the highest ratio ÷ 30 |
|} | |} | ||
{| class="wikitable" border=1 style="width: 80%;" | {| class="wikitable" border=1 style="width: 80%;" | ||
! style="width: 20%"|Design daily watt-hours required | ! style="width: 20%"|Design daily watt-hours required | ||
| − | ! style="text-align:left;"| = Total average daily energy demand from month with the highest ratio | + | ! style="text-align:left;"| = Total average daily energy demand (Wh) from month with the highest ratio |
|} | |} | ||
==Notes/references== | ==Notes/references== | ||
<references/> | <references/> | ||
Revision as of 08:16, 18 January 2021
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.
- Average monthly insolation: Solar resource data obtained for the location from Weather and solar resource evaluation.
- Total average daily energy demand for the month from the load evaluation.
- 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 |
|---|
