3. Introduction
Micro-hydropower plants (MHP) play an important role in the rural electrification of
Nepal.
In Nepal, hydropower plants with installed capacity in range of 10 kW to 100 kW are
termed to be Micro hydro and Nepal techno-entrepreneurs have gained wide and adequate
knowledge and expertise in MHP technology from the experiences for around 40 years.
About 28 MW electricity is being generated by 2900 MHPs as of July 2012 and the
number is still growing. This fact reveals that the scope of the MHP is high. As the global
concern of the environment impact from the renewable energy sources are widely being
researched
The present work aims to analyze the impacts caused by a typical micro hydro power in Nepal
by the help of Life Cycle Assessment (LCA) tool.
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1
4. LAC (Life Cycle Assessment)
LCA is a technique for analyzing various impacts from the product’s life cycle to the environment. The
product life cycle comprised from the extraction of raw materials to the disposal or recycle of the
products after its useful service life and therefore, it is also called as Cradle to Grave analysis .
The scope and range of an LCA study varies from the product to product, for instance if the study is
done for the products from the extraction of the raw materials to the manufacturing of the product
then the study is considered as the cradle to gate analysis.
LCA study is carried out mainly for assessing the impacts causing during the products life cycle, however
it is also used for the decisive tool if there exist alternatives. In this regard, data used, methodologies,
scope, range, assumptions and the output from the study should be completely transparent.
The stages of an LCA is shown in Fig. 1, which consists mainly three stages goal and scope definition,
inventory analysis, impact assessment and interpretation of the outputs from the study.
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1.1
5. Methodology
The environmental impact assessment is
based on LCA technique and modeled in
GaBi 6 software and flow chart is
shown in Fig.1.
Flowchart
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2 Methodology
6. Project site description
• The Agra Khola MHP project site is located at Pachhabang village of Rolpa district in Nepal.
The source of the flow is Agra River. The project area is not easily accessible for
transporting the goods.
• The nearest road head of the project site is Ghartigaun village of Rolpa District.
• Intake of the plant is about 25 km walking distance from Ghartigaun.Agra Khola is the
source of discharge and the discharge is 0.121 m3/s
• Design discharge is taken as 0.1 m3/s after making provision of 15% for evaporation,
flushing, seepage and downstream release. The gross head of the scheme is 24.2 m
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2.1
7. Agra Khola MHP’s location
Fig. 2.1Map of Project site (Rolpa District) Fig. 2.2Map of Nepal
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8. Goal and Scope definition
• To analyze the environmental impact caused by a typical micro hydropower plant in Nepal.
• Agar khola micro hydropower plant in Rolpa district of Nepal is selected for this purpose.
• To suggest possible improvements to reduce these impacts and calculate the energy payback
time.
The modeling of the system is done according to it’s installation time, year 2010 and the life
cycle period of the MHP is taken as 20 years.
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2.2
9. Functional Unit
• Data are organized and displayed in terms of the fundamental unit which is defined in the
ISO 14040 standard as ‘the quantified performance of a product system for use as a
reference unit a life cycle assessment study’.
• The product system for hydropower is considered as generation of electricity. The
functional unit should be in energy unit and in the study it is considered as 1 KWh as
generally used in this kind of analysis.
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2.3
10. System boundary
• The present assessment considers the
extraction of raw materials to operation
of the power plant. The end-of-life and
recycling of the material have not been
included in the model. The phases consists
of : extraction of resources, material
manufacturing, construction of the site
and operation. The transportation phase is
also included in the model.
The flow chart in fig. 3 shows the system
boundaries and scope of the present work.
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2.4
11. Model description
• Agra Khola MHP is a run-of-rive type plant with installed capacity of 14 kW intended to provide
electricity for 296 households.
• The output power of the plant is 14 kW considering losses in penstock, drive system, turbine and
generator.
• 15 Cross flow turbine with shaft output of 18 kW is used in the plant.
The end use plan for the project is shown in Fig.
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12. Model description
• The project is designed in such a way that the non-local materials required for
the construction purpose can be minimized. Important construction materials like
stone, wooden poles, sand and aggregate are available locally.
• The non-local materials for the construction of the power plant are transported
to the site with the help of porter from the nearby road in Ghartigaun village.
The model is divided into civil structures construction, electro-mechanical
components and operation phase.
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13. Civil structure components
Civil structure consists of head
works, trash rack to protect the whole
system from the larger waterborne objects
from entering the canal, flushing gates,
gravel trap, headrace canal, Forebay cum
silt basin, penstock alignment, anchor
blocks and support piers, power house
building and tailrace canal.
The major construction material
used in this phase is cement, steel bars,
gabion wires and CGI sheets. Other locally
available materials like sand, gravel are
not included in the model.
Electro-mechanical components
• Electro-mechanical components consists
of mechanical and electrical components.
• The mechanical components includes
penstock pipe, valves and turbine.
• The electrical components includes
generator, control and protection system
and transmission and distribution system.
• The transmission and distribution system
includes iron poles, service wire,
transformers, and insulators
Civil structure components Electro-mechanical components
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3.1
14. Life cycle inventory analysis
Life cycle inventory provides a complete list of materials and energy
and going ad coming out of system. It is a process of quantifying energy
and raw material needed for a system, emission to the environment,
solid waste and other releases incurred during the products entire life.
It is the most important phase of an LCA, where all the relevant
data is collected and organized.
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15. Table 1: Required Materials Extracted from the bill of quantities (BOQ)
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17. Transportation
The transportation of the material used for the construction of power plant has been
considered. It consists national and international transportation and the distance is
approximated. The actual origin of all the components in the system is difficult to locate.
Hence it is assumed that the most of the materials are manufactured within the nation,
whereas some components are being imported from nearby country India. 20 ton payload
trucks are assumed to carry the components to project site with the distances mentioned
in Table 3..
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4.1
18. Total life time energy
The total life time energy, considering 20 years life time, available to the villagers is 1961539
kWh and calculated as:
Transmission losses = 5.56 %
Distribution losses = 5.9 %
Average power available = 0.9444*0.941*14kW = 12.44 kW
Total lifetime energy = Average power available*hours in a year*% of operation time*life
time =12.44*365*24*20*0.9=1961539 kWh
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4.2
19. Result and discussion
Life cycle impact assessment (LCIA)
• Life cycle impact assessment in another major phase of an LCA. It shows the
environmental burden caused by considered stages of the model and classified into several
categories or indicators.
• The impact assessment is done using the CML 2001 baseline methodology and it shows the
environmental hotspots due to Agra Khola MHP.
• The considered indicators according to this methodology are global warming potential,
ozone depletion potential, acidification potential, eutrophication potential and abiotic
depletion potential.
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5.1
20. Life cycle environmental impact potential in kg-equivalent from civil structure,
electro-mechanical components, operation and maintenance and transportation phase
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22. The graph shown in Fig. 5 includes all the stages considered in the model. The main
contributor to the global warming is seen to be electro-mechanical components with 64.5 %, civil
structure construction with 28.9 %. Other phases like transportation and operation & maintenance
contribute relatively low. Global warming is the relative measure of the amount of heat trapped by
a greenhouse gas in the atmosphere. The significant emission is CO2 and the present assessment is
also based on the kg-equivalent of CO2 emissions from the activities. Ozone Depletion Potential
(ODP) is the relative amount of degradation caused in the ozone layer due to R11 compounds.
Electro-mechanical components is seen to be a major contributor with 86.7 %
Fig. 5 Explanation
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24. The graph shown in Fig. 6 shows the relative contribution to the environmental burden by
doing breakdown of the electro-mechanical components into penstock, power house equipment and
transmission and distribution system. Power house equipment includes the components that are
located inside the power house. Transmission and distribution is seen to be highly contributing to the
selected environmental impacts. It is mainly because of the aluminum being used in the distribution
wire and steel used in the poles. Penstock is also significantly contributing to the environmental
loads, whereas power equipment have lesser significance.
Fig. 6 Explanation
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25. Energy Payback time
Due to the unavailability of the actual data for the energy required to produce a
single power plant, data available in the literatures are taken into account in the present
work. Total electricity consumed for the construction and electro-mechanical equipment is
taken 366480 kWh. It does not include energy required for operation and maintenance.
Hence the energy payback time is 3.7 years and calculated as:
Energy payback time (years) = Total energy consumed/Energy produced in a year
= 366480 kWh/98079 kWh = 3.7 years
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5.2
26. Financial analysis
• Total project cost is estimated to be 7.3 million Nepalese rupees (NRs) with 0.287
million NRs as an annual operating cost.
• The domestic lightning sales rate is 3.5 NRs per watt electricity power provided per
month. With this plan, 11 month operating time yields 0.539million NRs.
• The income from business other than lightning is calculated as NRs 11 per total energy
consumption (kWh) with power factor 0.8.
• The annual income from this plan is expected to be 0.2904 million NRs. Hence the total
annual income of 0.8294 million NRs is expected to be generated. With a simple financial
analysis, payback return of the investment is seen to be 8.9 years.
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5.3
27. Conclusion and Recommendation
• LCA technique has been utilized to analyze the environmental burdens occurred
during the life cycle of a typical micro-hydro plant in Nepal. Agra Khola MHP, a
typical plant, is considered for the present work. The analysis shows that the
environmental hotspots are mainly due to the construction activities and electro-
mechanical components. The materials consumed in the construction of the power
plant contribute most for the global warming. Other several environmental indicators
are also considered. The transmission and distribution of the electricity is also
considered as a major player in creating the environmental burdens. Further payback
analyses revealed that energy payback time is about 3.7 years and financial payback
time is 8.9 years.
Multipurpose use of electricity produced, mainly for the business use
could boost the payback time and energy required to construct a power plant
could be deduced by using local materials as far as possible. Thus, this technique
could be utilized further to make decision in choosing and comparing with
different power generation alternatives.
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