Design of Photovoltaic (PV) Pumping
Introduction
In order to implement cost effective photovoltaic (PV) pumping system, it is necessary to follow some basic guidelines to design and size every system component. This page will explain about detailed calculation needed for sizing every system component. The basic step to design photovoltaic (PV) pumping system is:
1. Determination of water supply need
2. Calculation of pumping head
3. Estimation of solar resource
4. Finding appropriate solar pump and inverter
5. Calculation of PV panel required
Determination of Water Supply Need
According to [1], there are two distinct application for photovoltaic (PV) pumping system;
1. Drinking water supply (domestic water supply)
2. Irrigation water supply
Determination of Water Supply Need (domestic water supply)
For domestic water supply, the first data needed is to estimate the water requirement for one person/day. A good estimate can be found from [2], that relate how much water required to sustain particular activities. Here is the estimate:
Purpose Recommended minimum (liter/person/day)
Drinking water 5
Sanitary services 20
Bathing 15
Cooking and Kitchen 10
_______+
Total 50
For example, if there are a village with basic need of drinking water, bathing and sanitary services but no need for cooking; then it will require 5+20+15=40 liter/person/day. If the population is 300 persons, then the entire village will require 300 x 40 = 12 000 liter/day. Normally to compensate for water leakage on piping or distribution, 20% additional water will be required then the village will require 14 400 liter/day or 14.4 m3/day.
Calculation of Pumping Head
Pumping head is normally measured in meter (m), so sometimes there are misconception that pumping head is equal to pumping elevation. In actual, pumping head is divided into three components: elevation head, major losses head, and minor losses head.
Pumping Head (m) = Elevation Head (m) + Major Losses Head (m) + Minor Losses Head (m)
1. Elevation head is measured from the water source surface level to the point of outlet pipe level.
2. Major losses head is influenced by water flow rate, diameter of pipe, length of pipe, and type of pipe (PVC, HDPE etc)
3. Minor losses head is influenced by piping accessories including valve, elbow, inlet pipe etc
The detailed explanation can be found on [3].
Estimation of Solar Resource
Ideally, a ground based solar radiation measurement in location to be installed with solar water pumping system, is required in order to measure accurately the solar resource available for every part of the year. However, due to expensive equipment required, alternative data can be obtained from http://eosweb.larc.nasa.gov/sse/ for every part of the world freely or other solar resource data website available in the internet.
Solar resources available per day is cited on unit of kWh/m2/day or PSH (peak sun hour) with 1 kWh/m2/day = 1 PSH. Common confusion of solar resource data understanding is usually with solar data cited on unit of W/m2 that describe power. What is needed on solar pumping design is data cited on energy.
1. Solar Energy / Day --> cited on unit of kWh/m2/day or PSH (commonly used for solar pumping design)
2. Instantaneous Solar Power --> cited on unit of W/m2 (only used for complex modelling)
References
