Detailed DC system design

Location: Pampachiri, Apurimac, Peru
GPS coordinates: 14°11'37.65"S 73°32'31.73"W
Altitude: 3378m
Description: A two story adobe home in the Peruvian Andes with only DC power needs.

• 

  Photo of the home.

• 

  Location of the home.

DC load evaluation

#	Load	Quantity	Watts	Total watts	Duty cycle	Hours per day	Days per week	Average daily DC watt-hours
1	Cree 5 W LED	6	5 W	30 W	1	3 hours	7 days	90 Wh
2	Retekess radio	6 W	1	6 W	1	5 hours	7 days	30 Wh
3	Samsung cell phone	2	10 W	20 W	1	1 hour	7 days	20 Wh
Total average daily DC watt-hours								140 Wh

• Load: The make and model or type of load.
• Quantity: The number of of that 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
• Total average daily DC watt-hours = sum of Average daily DC watt-hours for all loads

Average daily watt-hours required

Average daily watt-hours required	= Total average daily DC watt-hours + Total average daily AC watt-hours
Average daily watt-hours required	= 140 Wh

Weather and solar resource evaluation

Maximum ambient temperature = 23°C
Minimum ambient temperature = 2°C
Minimum indoor temperature = 10°C

• 

  Retrieving PVGIS monthly insolation data.

• 

  Retrieving PVGIS monthly insolation data.

• 

  Retrieving PVGIS weather data.

• 

  Retrieving PVGIS weather data.

Load and solar resource comparison

Month	Average daily insolation	Average daily Watt-hours required	Ratio
January	193.85 kWh/m² / 30 = 6.46 kWh/m²	140 Wh	21.67
February	162.2 kWh/m² / 30 = 5.41 kWh/m²	140 Wh	25.90
March	(179.81 kWh/m² / 30 = 6.00 kWh/m²	140 Wh	23.36
April	174.98 kWh/m² / 30 = 5.83 kWh/m²	140 Wh	24.00
May	214.31 kWh/m² / 30 = 7.14 kWh/m²	140 Wh	19.60
June	200.05 kWh/m² / 30 = 6.67 kWh/m²	140 Wh	20.10
July	210.35 kWh/m² / 30 = 7.01 kWh/m²	140 Wh	19.97
August	229.96 kWh/m² / 30 = 7.67 kWh/m²	140 Wh	18.26
September	126.87 kWh/m² / 30 = 4.23 kWh/m²	140 Wh	33.10
October	214.82 kWh/m² / 30 = 7.16 kWh/m²	140 Wh	19.55
November	212.91 kWh/m² / 30 = 7.10 kWh/m²	140 Wh	19.73
December	176.98 kWh/m² / 30 = 5.90 kWh/m²	140 Wh	23.73

• Month: The month of the year.
• Average daily insolation: Solar resource data from PVGIS.
• Average daily Watt-hours required from load evaluation.
• Ratio = Average daily Watt-hours required ÷ Average daily insolation