Post on 20-Aug-2018
transcript
POWERING AGRICULTURE
Sustainable Energy for Food
MASSIVE OPEN ONLINE COURSE
Assignment One
Solar Powered Irrigation Systems
POWERING AG MOOC | TEAM MIDDLE AFRICA - ASSIGNMENT ONE 3
LEADERSHIP TRACK UNIT 01 2014 04 14 3
Group’s name 1. HABANABASHAKA Marachie (Rwanda)
2. John M Wesonga (Kenya)
3. Edison J. Sempiira(Uganda)
4. Jill Dana. Mugisa(Uganda)
5. Canisius Matsungo (Namibia)
6. Daniel Gahleitner (Tanzania)
Chapter 1: Case study location
The proposed solar powered irrigation system will be located in the following area:
Continent Africa
Country Rwanda
Region East Africa
Coordinates 2°01'59.3"S 29°52'29.5"E
Short
description
about the
socio
economy of
the region
(max. 500
words)
The catchment of Mukunguri is located in Rwanda Southern Province within two Districts and five
sectors with about 500,000 people. Rice production is the main agricultural and economic activity.
The catchment of Mukunguri has been challenged by soil erosion and flooding wetland. Of the 700
ha marshland in this area, only 450 ha are useful for rice production and the remaining consisting of
250 ha has been degraded due to erosion hence simple irrigation with channel is not possible in this
part. The cooperatives that produce rice in this marshland use traditional method of irrigation (tracing
channels only). Electricity used is from hydropower but it is not enough to be also used for irrigation;
it is used in rice processing mill and in household activity. Since the hillside has been protected from
erosion people are looking forward to making the whole marshland productive. The climate is good;
the rice is produced twice (rainy and dry seasons) a year and the rice demand exceeds so far the
capacity of production. The area has access to markets and therefore potential exists for expansion.
To harness the potential, there is need to provide reliable electricity for pumping water for irrigation.
Fig 1: Rainfall and radiation patterns of the study site
From above the area is characterised by moderate rain (Total rain is 991.3 mm) with two seasons.
The main rain season is between January and May while the lesser season is from August to
December. The area is located close to the equator and receives high radiation throughout the year. It
is therefore possible to tap this solar power for pumping of irrigation water for rice production. This
exercise therefore analyses the feasibility of exploiting the abundant solar radiation for irrigating rice.
0
1
2
3
4
5
6
7
0
50
100
150
200
250
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Rad
iati
on
kW
h/m
2/d
)
Rai
nfa
ll (
mm
)
Month
Actual Rain Effective rain Radiation
POWERING AG MOOC | TEAM MIDDLE AFRICA - ASSIGNMENT ONE 4
LEADERSHIP TRACK UNIT 01 2014 04 14 4
Optional
Fig 2: Google map of the study site (https://www.google.rw/maps/place/2%C2%B001'59.3%22S+29%C2%B052'29.5%22E/@-
2.0331336,29.8726663,752m/data=!3m2!1e3!4b1!4m2!3m1!1s0x0:0x0?hl=en&hl=en
POWERING AG MOOC | TEAM MIDDLE AFRICA - ASSIGNMENT ONE 5
LEADERSHIP TRACK UNIT 01 2014 04 14 5
Fig 3: Visitors assessing production potential of Mukunguri area
Fig 4: Rice growing in Mukunguri area
POWERING AG MOOC | TEAM MIDDLE AFRICA - ASSIGNMENT ONE 6
LEADERSHIP TRACK UNIT 01 2014 04 14 6
Chapter 2: Farming system and water requirement
Farming
system
(maximum
200 words)
A semi-intensive farming system is used in this marshland where farmers are grouped in cooperatives.
The cooperatives provide seeds, fertilizers, pesticides and other technical support to farmers. The
productivity of rice is low (6.5 tons per hectare) because the marshland is not laid out well, there is no
agriculture mechanization and traditional irrigation techniques are used. With introduction of clean
energy in this area yields can be increased to 8 tons/ha. The unused part of marshland is used for the
production of sweet potatoes which have low market value. We want all the marshland to be covered
by rice production.
Water
requirement
(maximum
1000 words)
1. Existing irrigation systems: The existing traditional irrigation with tracing simple channels
from the river Mukunguri to the surrounding Plots. The channels width is about 0.5 m which
can ideally provide 100 m3/day.
2. Crop water requirement profile: We assumed that only rice is grown and used Cropwat to
estimate crop water requirements. Crop water requirement was estimated as 501.6 mm/dec
which is converted m3/day as follows 501.6 mm / 1000 m x 1 ha /10 days =
(501.6*10,000)/(10*1000) = 501.6 m3/day.
3. Water requirement from SPIS: We use the highest irrigation water requirement for
calculating the SPIS requirements, which is 24.3 mm/dec (i.e.per 10 days), which implies
2.43 mm per day. The selected value is the highest and will accommodate the worst case
scenario. The total water required per day = 2.43 mm /1000 x 10,000 m2 x 250 ha = 6,075
m3/day. The monthly water requirements are shown in Fig 6.
Fig 5: Screenshot from CROPWAT showing computation of Crop Water Requirement. NB.
Irrigation is only required when rainfall is less than ETc.
Fig 6: Monthly irrigation requirement for rice growing in the study site. Details of computation, parameters and references used in CROPWAT are provided as a separate documents
submitted already.
24.322.6
7.9
15.1
12.7 12.2
0.1 0 0 0 0 00
5
10
15
20
25
30
1-F
eb
11
-Feb
21
-Feb
1-M
ar
11
-Ma
r
21
-Ma
r
1-A
pr
11
-Ap
r
21
-Ap
r
1-M
ay
11
-Ma
y
21
-Ma
y
Irri
gat
ion
Req
uir
emen
ts (
m3/d
)
Dates
POWERING AG MOOC | TEAM MIDDLE AFRICA - ASSIGNMENT ONE 7
LEADERSHIP TRACK UNIT 01 2014 04 14 7
Chapter 3: Pumping head (height) calculation
Pumping head
(maximum 500 words)
1. Please calculate the height difference between the water level in the well or basin
(or ground water pumping level) and the water storage tank (of your irrigation
system). To simplify matters, we do not go into details of frictional and other losses
here (in reality, these losses need to be accounted for while calculating the total
head).
Drip irrigation may not be possible for rice because it is not planted in rows like
cabbages on maize. Crops like rice and wheat which are broad cast on planting are
difficult to irrigate using drip irrigation. Overhead sprinkler irrigation, or centre
pivot irrigation or flood irrigation can be used. Because of the extent of our field,
250 ha and the nature of the crop flood irrigation may be most suitable. It has the
advantage of a very low friction head loss and it is simple technology however its
disadvantage is water efficiency because a lot of water is lost through seepage and
evaporation. However, as highlighted in the background story, flood irrigation is
not suitable.
Sprinkler irrigation is suitable for the situation but has the disadvantage of high
head loss because even the nozzle requires the water to have substantial amount of
head in order for the sprinkler to throw. This is the case where centre pivot
irrigation could be better as it does not really need to throw the water as much as
the sprinkler would do. However, it requires the land to be fairly flat, is more
expensive and more complex than the other forms of irrigation.
Just as the pictures in the background show, centre pivot irrigation is chosen for
this site.
Since centre pivot irrigation is selected a total pumping head of 10 m is used.
Note: Here, in order to decide the position (height) of the water storage tank from ground (land to be
irrigated) you need to choose a proper water distribution type (irrigation type) for your site. You may
choose the following heights for different schemes: Flood Irrigation: 0.5 m, Open channels: 0.5-1 m,
Drip/trickle: 1-2 m and Sprinkler: 10-20 m.
POWERING AG MOOC | TEAM MIDDLE AFRICA - ASSIGNMENT ONE 8
LEADERSHIP TRACK UNIT 01 2014 04 14 8
Chapter 4: Sizing of the SPIS
PV panel size
(capacity)
(maximum 500
words)
1. By using the equation listed in the reader, you should now be able to calculate the PV
panel size needed to supply your water demand.
We use formula for calculating the PV panel size, taking G at the tilted angle of 10°
(G=5.18 kWh/m²/day)
From Ppeak = 8.0 𝐻𝑇×𝑉𝑑𝑎𝑦
𝐺𝑡𝑜𝑡𝑎𝑙,𝑑𝑎𝑦
Where;
HT = 10 m,
Vday = 6075 m3/day,
Gtotal,day = 5.18 kWh/m2.day,
Ppeak = 8.0 x 10 × 6075
5.18
Ppeak = 93,822 Wp
Ppeak = 93.822 kWp
Chapter 5: Summary
PV panel size
(capacity) (maximum
300 words)
An analysis was carried out to assess feasibility of a solar powered irrigation system for rice
production in the Mukurungi region of Rwanda in Africa. Rice production in the area is
limited due to lack of energy for irrigation. The area has readily available water supply
and receives abundant solar radiation throughout the year. Using CROPWAT the crop
water requirement was estimated for the various growth stages. Data for various parameters
required to implement CROPWAT were obtained from literature or assumed from
experience. After factoring rainfall, irrigation requirement was estimated for 10 day
interval. The highest irrigation requirement was estimated to be 2.43 m3/day/ha and this
value was used a basis for designing the solar power irrigation system. For 250 ha area the
total irrigation water was 6075 m3/day. Using data from NASA website, the solar radiation
profile of the study area was determined. A tilt angle of 10 was assumed and a value of 5.18
kWh/day was used for calculation of peak energy requirement. For rice production a
centre pivot irrigation system was selected for which a head of 10 m would be required.
We determined that the capacity of solar panel required would be 93.8 kWp. Since, the
worst case scenario was used this would be able to serve the area throughout the growing
period. The system is only applicable if only rice is grown and other demands were not
included.