Solar power for irrigation

~UId

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ruwt21

for lrri Ita ti on The Small Solar Thermal Pump: an Indian development o.o

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11

Month --Insolation

--

W

--Irrigation

Need

Electrical Supply

ater is

the basic elementfor human survival. A high per-

of the populaüon adequate water facilities

centage that is without

mainly for agricultural needs is concentrated in solar-abundant rural areas. Most of these areas are in developing and underdeveloped countries and are deprived of conventional sources of energies, either due to natural shortages or because of institutional and economic reasons restricting energy availability. In India, about 45 % of GNP originates from the agricultural sector, while the consumption of agricultural pump-sets is estimated to be about 9% of total electricity supply. Out of 550,000 villages of rural India, 80,000 are still to be electrified while the majorlty of the villages face extensiveshortages and uncertainty of electrical power supply mainly in summer when there is maximum need for irrigation. Kiran Chandwalker,

Thermalsolar / Stiletto Engineers, Hyderabad, India and M v. Oppen, University of Hohenheim, Stuttgart, Germany describe an Indian development, the small solar thermal pump, that offers a cost-effective answer to irrigation problems in countries such as India. During the past &ca&s, the demand for electricity has always increased more than the additional generating capacity installed resulting in sreadily increasing overall shortfall that presently is at about 15 to 20%. For social reasons, agricultural power in India is highly subsidised which is causing severe strain on the electricity boards with annual losses of Rs. 15 000 000 000 (US$ 350 million) on subsidies to irrigation pump-sets and due to transmission/distribution losses. No short-term solution appears to be in sight to bridge this gap between supply and demand. The use of diesel pump-sets is wide spread in non-electrified areas. The diesel is also high[y subsidised. Even so, the cost of the subsidised diesel has gone up by more May 2001

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www.re-focus.n«t

than 300% during the past decade and is likely to further increase exponentially so that diesel pump-sets do not offer a viable alternative for sma[[ farm irrigation. In India, there are about 20 million small farmers with [and holdings of less than 2 hectares. One quarter of the cultivated area is irrigated and more than half of the irrigation water comes from wells. Most of the irrigation wells are equipped with electrical pumps and the demand for electricity for irrigation increasingly exceeds suppiy. An estimated number of I5 million wells in India depend upon electrical power supply. Weil irrigation felles on groundwater, which tends to become scarce but new systems of surface water management for groundwater recharge have been deve[oped for augmenting depleted shallow aquifers ( B. Adolph, 1999 andT. Shah, 1993).

Solar power for irrigation Considering the possibilities for maintaining water tabtes through appropriate management at re[ativdy shallow levels and in view of the narrowing limits in conventional power supply in India, solar power offers an effective alternative for drawing irrigation watet from shallow wells and from surface watet in rivers, canals or tanks. Moreover, the suitability of so[ar power for lifting water to irrigate plants is undeniable because of the complementarity between solar radiation and the water requirements of plants. The more intensively the sun is shining the greater is the power to supply irrigation water while on the other hand on rainy

f-3

FEATURE

‘4

days irrigation Electrical has

is neither

power

maximum

irrigation

using

humans

version

fossil fuel. The

photovoltaic

steam An

ex-ante

costs

comparison

of water

engines power

sources

mal system, offer

by

manufacturing

1999).

engine

of

the

pumping

as to

make

it a ‘closed’

cycle.

Figure layout

2 illustrates of

the Pump.

working

used in SSP

fluid

a synthetic,

of

liquid

and latent

NTP.

The

more

diameter.

is done

to guide

such

as cooking,

and

heating

energy

into

is called

the small

solar

Even

though

the same

engine

adapted

water

to drive

sentation

limits

pumped

a cooling

for irriga-

can

system,

(SSP).

needs.

also be

alone

this pre-

on the SSI?

SSP works

working ates

A boiler

fluid receives

high-pressure

enters

type

mechanical vapour

of

is internally

pump

and

where

to

a water The

pump

is initial-

the exhaust.

vapour

it is cooled

enters indirectly

pumped

water

pressure

liquid.

This

liquid

is picked

pump

and

pumped

back

the feed pressure

and gets converted

to the boiler

to complete

From

annual

sent

forest

cover

on firein

150

and

the pre-

of total

land

to meet.

Performance of the SSP Additional

features

inlet vapour, pump

like a super-heater

feed storage

for charging

some liquid

as shown

of

gram

tional

at

SSP

about

temperature,

at the

concentrator.

solar

the water

240

overall

2 to 2.5%

is around

insolation).

balance

in Figure

effi-

A dia-

of SSP is shown

3.

Expected Costs and Returns There

are

many

larger

tems

built

with

much

However,

all these

higher

output

rupees.

Even

Government not

the

around

trials.

are

for

much

above

if the

cost

is subsidised

agencies,

a small

to find

The

a million

investment

of this to keep

However,

in small

in developing

The

coun-

manufacturing

prototype

batches

can-

SSP is developed

farms

Rs 45 000

by

farmer

low so as to be applicable

present

in small

systems

sys-

efficiency.

cost

marginal

initially

better

and

be expected

and priming

solar-thermal

of

SSP

(ca US$lOOO) for field the

SSP

cost of would

per unit

application once

be

and

manufac-

boiler

focal

zone

of

With of about

the SSP operates speed

and

2,000

litres

meters

of head.

pumping

SSP

The

is easily

temperature

RPM

or

layout

90°C

the

to

of land

is opera-

which

achieved

amount

hectare

output/solar

tries like India.

with

would

on one

of the energy

and for

day or 20 m3 over a

which

of a hectare.

the

(hydraulic

the cost

the cycle are also pro-

in the

The

tank

the boiler

to initiate

at a stabilized

the cycle.

which 11%

unable

on l/3

magnitude.

by the

up by

heavily

for firewood

tonnes

of only

area is absolutely

30 to 35”C,

at high

population

to be between

metric

a con-

to a low-

alternative

of a rural

demand

is estimated million

diagram.

low-pressure

which

300

vided

to recover

from

still depends

piston

a regenerator

the

in India,

The

industrial

an excellent

3.5m,

in a chart

water,

this concentrator

needs

a feed

by the expander

some of the energy

denser

The

to seal.

through

regenerator,

of the

synchro-

connected

externally

exhausted

ly passed

generates

direction

pistons.

a hermetic

vapour

acting

to maintain

power

engine

through

vapour

by a set of valves, which

automatically

nisation

which The

is controlled

operate

the

This double

expander, power.

the

solar heat and gener-

vapour.

in to a reciprocating

piston

of a closed

containing

provide

purpose

cottage

for the cooking

India

on the principle

“Rankine-Cycle”.

can

of water

ciency

sterilizing

for

2mm 6mm

can also be

70-m4/

of

the

i.e. over 90”.

of the SSP for 6 hours/day

around

head

can

for any other

cooker

Operation

device

3 pm,

baking,

water

implies

to follow

and concentrator

As a solar

wood.

Principle of operation The

collector

hour.

1.5 m in

tracking mirror

9 am and

at of

the help of one or of around

the

used as a heat source

solar

pump

itself to focus

sun between

80 callgm

concentration

with

mirrors

The

tion

and

An automatic

be used

waterpump

Figuw 2: Schematic layout of the small solav thermal

heat of about

parabolic

tank

about

collection

This

heat

boiling

of

40°C

Water

non-

with

remperature

solar energy

so far for

for converting

The

environ-

Small solar thermal engine developed

Small

Solar-thermal

non-inflamma-

on a

is so

ble

and for cooling.

engine

and

inside

explosive,

solar-thermal

developed

system

to

K. Chandwalker,

small

the

does not go

friendly,

over the alter-

focuses

operation,

contained

the

Feed

and

mentally

ther-

costs

so

losses

fluid

of the

fully

Small solar - thermal pump

the

efficiency. the

out

is

is likely

the following

as it has been

water

a solar

in

and operation

presentation

powered

solar-thermal

advantages

Therefore

estimated

below

( M. von Oppen,

natives

or via

Diesel

that

as described

via

directly.

the

vs.

has shown

considerable

con-

either

from

reduce

increase

IRRIGATION

liquid

of the expander

to

FOR

heat in the

regenerator

as

POWER

to the boiler,

up some

working

of

supply

picks

or

energy

vs. photovoltaic

high-pressure

movements

of producing

kinetic

its way

In

process

for generating

On

or

mechanical

SOLAR

the

animals

of electricity

thermodynamic

-

-

exhaust has

on the basis

is possible

generation

1 illus-

year.

of

water

of solar energy

for

water

generated power

or of wind-or

of burning

Figure

irrigation

been muscle

hand,

demand

for a typical

for pumping

conventionally

the

when

is at a maximum.

Energy

nor needed.

on the other

shortage

trates this graphically

of

possibie

supply,

_

of

work

May 2001

of around

can lift around water This of

RE

over

6

results

in

12m4

per

Figure 3: Energy balance of the mall solar thermal water pump

www.re-focus.net

25

O

FEATURE

tured at a scale of a few thousand units per year could probably be produced and sold at less than Rs 20 000 (ca US$420) a piece. Considering an annual cost of I 0 % interest and depreciation of also 10 % this would amount to Rs 4000 per year for a water supply sufficient to grow three erops per year on 1/3 of a hectare. At an incremental yield from these crops of only 500 kg (of 1.5 t/ha) sold at Rs 8 / k g this cost is just covered. The present prototype, however, could conveniently be increased to three or four times in capacity without much additional cost. Since incremental yields from a larger pump irrigation three times the area would be in the order of 3 to 5 tons/ha, the SSP obviously promises to be a highly effective proposition( B.D. Dhawan, 1988). All the materials and machinery needed for manufacturing and maintaining the SSPs are available in local markets in India. The design has a scope for increasing the capacity of the system or even adapting the basic design for different applications. These features can allow development of small Iocal maintenance or production units of SSP when it is popularised. Taking into consideration these aspects enhances further the viability and the need for imple-

MIRO

- SOLAR POWER FOR I R R I G A T I O N

mentation of SSP in developing countries like India.

poor countries most. In this scenario, products like the SSP offer bope for the future.

Future steps required for implementation

Contact. Prof. M von Oppen, Institute of Agricultural Economics, Hohenheim University (490), D-705993, Stuttgart, Germany. Tel: +49 711 4592784; e-mail: [email protected]. or contact Mr. Kiran Chandwalker, Stiletto Engineers, F-5/A, IDA Kukatpally, Hyderabad (A.P), India, Pincode -500037. Tel: +91 40 4754734/ 3079295; e-mail: [email protected]

For a successful introduction of the SSP into the Indian and the world market several preliminary steps have to be careful[y taken. These would need to lead from one prototype via a smal[ series of operational units for advanced field trials to a first batch of several hundred units for extended field trials, within and outside India. In view of the steadily worsening energy situation and the viable alternative offered by the SSP, early support and investments in to the efforts for SSP production would be desirable. Apart from the social benefits, the investments in the SSP production units can also be financially attractive with a virtually unlimited market and scope. As mentioned above, the SSP offers scope for adapting the basic system for many other applications inc[uding solar-thermal cooling. It is common knowledge that out available fossil fuels are not going to last for ever and the inevitable energy shortage will hit the

References B. Adolph, People's participation in Natural Resource management in "Kommunication und Beratung", No 36, Margraf Verlag Weikersheim, 1999 B.D. Dhawa, Irrigation in India's agricuItural development, Sage Publications, New Delhi, 1988 M. von Oppen and K. Chandwalker, Einsatz der Solarthermie zur Kühlung und Wasserförderung in Indien, University of Hohenheim, 1999 T. Shah, Groundwater markets and irrigation development, Oxford University Press, Bombay 1993

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