Physical evaluation
Location: Puerto Arturo, Madre de Dios, Peru
GPS coordinates: -12.48694444, -69.21305556
Altitude: 3378m
Description: A community building with lighting and AC power needs. The system is used all year long, but it is typically only used three to four times a week by community members for meetings, parties, or training sessions. Load usage is typically during the day. The community does not intend on adding any major appliances in the near future.
The system will use DC for lighting and AC for powering loads. DC is used for lighting so that the system continually provides light regardless of whether the inverter is turned on. As the building is used intermittently, the inverter can be turned off to reduce wear and to lessen the liklihood of an accident or damage from lightning.
Location of the building.
Although the system is used only one day a week, inputting 1 day a week of usage for the loads will lead to an undersized array and a poor system design. We will input 4 days a week to ensure that the PV source is still of a reasonable size.
DC load evaluation
Step 1: Fill out DC load chart
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April - September
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October - March
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| #
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Load
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Quantity
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Watts
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Total watts
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Duty cycle
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Hours per day
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Days per week
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Average daily DC watt-hours
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Hours per day
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Days per week
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Average daily DC watt-hours
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| 1
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LED light
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8
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5 W
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40 W
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1
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3 hours
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4 days
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69 Wh
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3 hours
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4 days
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69 Wh
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| 2
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Inverter
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1
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7 W
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7 W
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1
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3 hours
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4 days
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12 Wh
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5 hours
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4 days
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12 Wh
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- Load: The make and model or type of load.
- Quantity: The number of the particular load.
- Watts: The power rating in watts of the load.
- Total watts = Quantity × Watts
- Duty cycle = Rated or estimated duty cycle for the load. If the load has no duty cycle a value of 1 should be used. A load with a duty cycle of 20% would be inputted as .2
- Hours per day: The maximum number of hours the load(s) will be operated per day. If the load has a duty cycle 24 hours should be used.
- Days per week: The maximum number of days the load(s) will be operated per week.
- Average daily DC watt-hours = Total watts × Duty cycle × Hours per day × Days per week ÷ 7 days
Step 2: Determine DC energy demand
| Total average daily DC watt-hours (April - September)
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= sum of Average daily DC watt-hours for all loads for April - September
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= 81 Wh
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| Total average daily DC watt-hours (October - March)
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= sum of Average daily DC watt-hours for all loads for October - March
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= 81 Wh
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AC load evaluation
Step 1: Determine inverter efficiency
A conservative inverter efficiency value of .85 is going to be used.
Step 2: Fill out AC load chart
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April - October
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March - September
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| #
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Load
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Quantity
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Watts
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Total watts
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Duty cycle
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Surge factor
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Surge watts
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Power factor
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Volt-amperes (VA)
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Hours per day
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Days per week
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Average daily AC watt-hours
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Hours per day
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Days per week
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Average daily AC watt-hours
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| 1
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Projector
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1
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300 W
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300 W
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1
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0
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0
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.9
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333 VA
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3 hours
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4 days
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605 Wh
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3 hours
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4 days
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605 Wh
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| 2
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Stereo
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1
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30 W
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30 W
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1
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0
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0
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.9
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33 VA
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3 hours
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4 days
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61 Wh
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3 hours
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4 days
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61 Wh
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| 3
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Cell phone
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5
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5 W
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25 W
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1
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0
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0
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.9
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28 VA
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1 hour
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4 days
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17 Wh
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1 hour
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4 days
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17 Wh
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- Load: The make and model or type of load.
- Quantity: The number of the particular load.
- Watts: The power rating in watts for the load.
- Total watts = Quantity × Watts
- Duty cycle = Rated or estimated duty cycle for the load. If the load has no duty cycle a value of 1 should be used. A load with a duty cycle of 20% would be inputted as .2
- Surge factor = Rated or estimated duty cycle for the load. Common values are between 3-5. If the load does not have a surge requirement a value of 0 should be used.
- Power factor = Rated or estimated power factor for the load.
- Volt-amperes (VA) = Total watts ÷ Power factor
- Hours per day: The maximum number of hours the load(s) will be operated per day. If the load has a duty cycle 24 hours should be used.
- Days per week: The maximum number of days the load(s) will be operated per week.
- Average daily AC Watt-hours = Total watts × Duty cycle ÷ Inverter efficiency (Step 1) × Hours per day × Days per week ÷ 7 days
Step 3: Deteremine AC energy demand
| Total average daily AC watt-hours (April - September)
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= sum of Average daily AC watt-hours for all loads for April - September
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682 Wh
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| Total average daily AC watt-hours (October - March)
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= sum of Average daily AC watt-hours for all loads for October - March
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682 Wh
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Step 4: Determine AC power demand
| Total VA
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= sum of volt-amperes (VA)
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394 VA
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| Total VA with surge watts
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= sum of Surge watts for all loads + Total VA
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394 VA
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