Difference between revisions of "Load and solar resource comparison"
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*'''Month:''' The month of the year. | *'''Month:''' The month of the year. | ||
| − | *'''Average monthly insolation:''' Solar resource data obtained for the location from [[Weather and solar resource | + | *'''Average monthly insolation:''' Solar resource data obtained for the location from [[Weather and solar resource evaluation]]. |
*'''[[Load evaluation#Total average daily energy demand|Total average daily energy demand]]''' for the month from the load evaluation. | *'''[[Load evaluation#Total average daily energy demand|Total average daily energy demand]]''' for the month from the load evaluation. | ||
*'''Ratio =''' Total average daily energy demand ÷ Average monthly insolation | *'''Ratio =''' Total average daily energy demand ÷ Average monthly insolation | ||
Revision as of 12:36, 5 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 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 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 | Total average daily energy demand | 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 from month with the highest ratio ÷ 30 |
|---|
| Design daily watt-hours required | = Total average daily energy demand from month with the highest ratio |
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