Small Hydro Power (SHP)
Preliminary Study and Hydro Resource Assessment
Roberto Suffredini
Enel – Generation and Energy Management
Renewable Energies
2
Hydro Power
• Convert potential and kinetic energy of water flow
into electrical energy:
Power (kW) = Head (m) x Flow (m3/s) x 9.81 x Plant Efficiency
• Hydro Power system are primarily classificated such
as:
– RUN-OF-RIVER (Run-off dependent, without reservoir, grid
base load)
– STORAGE (Renewable Energy may be storage, power
modulation and grid frequency regulation, high power)
– PUMPED STORAGE (High energy storage capacity, high
power)
May 2007
3
Hydro Power
• Secondary classification for HPP is for:
– LOW HEAD
– MEDIUM HEAD
– HIGH HEAD
Above definitions are not univocal, but power-related
•
•
•
•
•
Hydro Power providing more than 19% of world’s electricity
Mature (more than 100 years old) and high reliable technology
High efficiency convertion from primary energy, up to 90%
Very large power size in single station, up to 14.000 MW
Impact on environment is size dependent and may be very
large
• Very long lifetime of plant
• Low O&M costs
May 2007
4
Hydro Power
• An Hydro Power facility consist of:
– Diversion structure and reservoir (river run-off
capture; storage and transport of water)
– Powerhouse (hydraulic to electric energy
conversion)
– Transformers, Substation and Powerlines
(voltage convertion; switching and energy
trasmission)
– Access roads
May 2007
5
Hydro Power
Plant typical scheme
Hydropower Plant
Dam
Transformer
May 2007
6
Hydro Power Plant general layout
• Diversion & storage
–
–
–
–
–
–
Dam or weir
Intake
Open surface or pressure canal
Forebay or surge tank
Penstock and valves
Tailrace
• Powerhouse (outdoor or underground)
– Turbines and valves (hydraulic to mechanical power)
– Generators (mechanical to electric power)
– Substation with transformers and switchyard (generator to line
connection)
– Control & Protection system
– Ancillary (e.g.: cooling & lubricating system, governing, crane)
May 2007
7
Hydro Power Plant
• Very large size Storage HPP
ITAIPU’
Paraguay/Brasil
Dam
Paranà River
Spillway
Powerhouse
World’s Largest HPP
Reservoir: 29 x 109 m3
Units: 20 x 800 MVA
Capacity: 14.000 MW
Energy: 90 TWh/yr
May 2007
8
Hydro Power Plant
• Underground Pumped Storage Plant Scheme
Upper
Penstock
Lower
Reservoir
Pump-Turbine
May 2007
9
Hydro Power Plant
• Power spectrum of Pumped Storage Power Plant
May 2007
10
Small Hydro Power (SHP)
• Hydro Power Plant having power up to 10 MW
– Other classification limit is in max discharge for Low-Head SHP
• Small-scale Hydropower is one of the most cost-effective and
reliable energy technology
• More detailed power-classification:
– SMALL HYDRO: from 1 to 10 MW
– MINI HYDRO: from 100 kW to 1 MW
– MICRO HYDRO: < 100kW
• Generally, SHP are run-of-river system
• Environmental impact is minimal if sufficient precaution are
taken
• Grid connection:
– Usually on central grid in developed country
– On insulated grid or off-grid are typical in developing country
May 2007
11
Small Hydro Power (SHP)
• An example of Run-of-River SHP
BALMA
Penstock
Powerhouse
North Italy
Cervo River
Head: 75 m
Units: 1 x 1.4 MVA
Cross-Flow Turbine
Capacity: 1 MW
Tailrace
May 2007
Energy: 5 GWh/yr
12
Planning Run-of-River Small Hydro Project
• Preliminary Site Investigation
–
–
–
–
–
–
–
–
–
–
May 2007
Land reconnaissance and maps research
Hydrology and flow duration curve assessment
Head measurement
Preliminary geological and climatological land survey
Gross hydropower potential estimation
Residual flow determination
Electric grid distance survey (if grid connected)
Access way evaluation
Regional laws assessment
Energy price
13
Planning Run-of-River SHP
Land reconnaissance and Maps research
• Topographic maps are essential for any step of project
development
• Maps scale (Italy)
– From 1:100.000 to 1:25.000 usable prefereably only for hydrology
and general land survey, electric grid distance, access way
– From 1:10.000 usable for geodetic and gross head estimation in
High and Medium Head SHP
– Low Head SHP assessment require most detailed maps (1:2.000,
1:1.000 or less scale) and customized topographic survey
• Land survey and detailed photographic relief are required
• Images from aerial and satellite survey may be very useful
May 2007
14
Planning Run-of-River SHP
Hydrological study
• Need for river flow statistics assessment
Rainfall
Snow
Water cycle
Catchment
May 2007
15
Planning Run-of-River SHP
Hydrology for SHP evaluation – Main problems
• Hydrology and river flow statistics assessement often
represent a great difficulty step for SHP feasibility
study
• For a correct SHP planning is required run-off
database based on a reliable long-term record,
ideally 10 years
• Unfortunately, when long-term run-off records exist,
not always the recorded river site is the same or near
to the projected SHP water diversion
May 2007
16
Planning Run-of-River SHP
Hydrology – Statistics at ungauged river site
•
If streamflow statistics are missing or incomplete, catchment
must be characterizated from thematic and topographic maps,
meterological and geographical database
– Catchment area and their boundary perimeter, hypsographic curve and
mean altitude
– Side and riverbed talweg slope, main river and tributary lenght, catchment
form
– Soil permeability classification and groundwater presence
– Mean rainfall heigh and isohyet curves
– Vegetation kindes and their surfaces
– Snow presence, air temperature, wind intensity and other meteorological
data
– Other (e.g. time constants)
•
May 2007
Above methodology may be adopted by an expert hydrologist for to work out an accurate,
complete, but many expensive and long duration hydrologic study. This is typically
unacceptable for an SHP, particularly for the preliminary feasibility assessment
17
Planning Run-of-River SHP
Hydrology – Methods for to obtain statistics at ungauged river site
• Alternative ways for streamflow statistics estimation:
– Regionalization methods (dimensionless FDC)
– Catchments similitude method (trasposition of hydrometric data
from nearest gauged catchment)
– Hydrological software tools (if relevant meteorological and
topographical data are available then it may be used for a quick
flow statistics assessment)
– Recording streamflow at continous gauged station for relevant
time (almost one year)
– Flow measurement only at significant run-off conditions
– Measurement of Q95% (or Q90%) low flow indicator. It could help
the user in estimation of flow statistic curves, of natural yearly
mean flow and also for the study of SHP environmental impact
mitigation
May 2007
18
Planning Run-of-River SHP
Hydrology – Final data outputs
• Hydrological study on the catchment has the following goals:
– Flow Duration Curve (FDC)
– Simulated (or analiysed) Streamflow
• Streamflow analysis has like output an hourly (daily) time series of
streamflow at an indicated river site.
Daily simulated streamflow
– Flood peak intensity and frequency analysis, necessary for to
assess the hydraulic risk in engineering of weir, intake,
powerhouse, tailrace canal and access road
May 2007
19
Planning Run-of-River SHP
Hydrology – Flow Duration Curve (FDC) analysis
• The Flow Duration Curve is the graph showing the percent
time (e.g. of year or month) that the streamflow at a site is equal
or exceed to an assigned value
Flow (m³/s)
50.0
Flow-Duration Curve
40.0
30.0
20.0
10.0
0.0
0 10 20 30 40 50 60 70 80 90 100
Percent Time Flow Equalled or Exceeded (% )
May 2007
20
Planning Run-of-River SHP
Hydrology – Main parameters related to water flow
• Run-off statistics at an analysed site:
– Flow Duration Curve
– Average yearly natural flow Qnat
– Flood peak flow (for assigned return time)
– Q95% (or Q90%) like low-flow indicator
May 2007
21
Planning SHP resources in large area region
• Requirement of Topographical Maps for Large Area
• Geographic Information System (GIS) for topographic and
thematic maps. GIS tools for hydrology
• Remote Sensing Technology (aerial & satellite)
• Hydrological Assessment Software Tools
GIS and Remote Sensing used for potential SHP assessment in Uganda region – 2005, Lund University/Sweden
May 2007
22
Planning Run-of-River SHP
May 2007
23
Planning Run-of-River SHP
May 2007
24
Planning Run-of-River SHP
May 2007
25
Planning Run-of-River SHP
May 2007
26
Planning Run-of-River SHP
May 2007
27
Planning Run-of-River SHP
Head estimation
• Measurement of geodethical heads
– From topographic site survey
– From maps
– Other (GPS, water level instrument on Very Low Head site)
• Net Head
– Gross Head Hg is the indicator of potential hydro power available
at the site, in accord with the adopted SHP scheme
– Gross head may be variable with flow discharge
– Net Head Hn = Hg – Head Loss
– Head losses are analysed as:
• Friction Loss -> quadratic function of flow: DH = k x Q2
• Local Loss -> quadratic function of velocity: DH = k x V2
May 2007
28
Planning Run-of-River SHP
(Related with Qnat)
(Related with Qdiv)
May 2007
29
Planning Run-of-River SHP
SHP-related flow definitions
• Main flow parameters in SHP facility are:
– Maximum diverted flow Qmax
– Minimum usable flow Qmin (from hydraulic turbine
lower operation limit)
– Average diverted flow Qdiv (related to net mean
water volume used for energy production)
– Residual flow Qres (released at the intake for
enviromental impact mitigation purposes)
May 2007
30
Planning Run-of-River SHP
Turbine selection
Pelton
• Turbine type and
number of units choice
are depending by:
Turgo
Francis
 Net Head (Hn) and
Design Flow (Qmax)
 FDC trend, by
means of energy
production estimation
(interactive analysis)
 Suction head Hs on
Low Head SHP
May 2007
Kaplan
Crossflow
31
Planning Run-of-River SHP
Plant Global Efficiency and Power Duration Curve
• Efficiency items:
–
–
–
–
–
–
hH Hydraulic, from all water conduit loss
hT
Turbine
hG Generator (and gearbox if present)
hTR Trasformer
hA Ancillary system
Above efficiency parameter may be defined for every value of flow
discharge
• Punctual SHP Global Efficiency hi
– hi = hHi x hTi x hGi x hTRi x hAi
– To abtain net power on the grid connection, the punctual global
efficiency hi will be applied to gross hydraulic power available for
each flow related to every 5% of duration in FDC
May 2007
32
Planning Run-of-River SHP
May 2007
33
Planning Run-of-River SHP
Energy items summary
• From SHP preliminary study we can obtain the
following main energy parameters:
– Average annual energy delivered Em (MWh/year)
– Peak power Pmax (kW) [Plant capacity]
– Minimum power Pmin (Firm capacity for a related time
period)
– Plant capacity factor = Em/Hydraulic energy available
• Energy Em is the main economic item
• Peak power is related, e.g., to the possibility of
connection to main grid
• Minimum power is important parameters for energy
production on insulated grid or off grid
May 2007
34
Planning Run-of-River SHP
Geology and Land survey
•
•
•
•
•
May 2007
Geological preliminary study is essential for to perform at first step
an accettable layout for new SHP plant and to supply at hydrologist the
necessary information about catchment
Soil geological information at a studied site may be obtained by
geologic maps (if exist) or from a land survey, performed by an expert
geologist
Clearly, all parts of land interested by SHP layout may be critical and
must be examined mainly in sense of soil stability evaluation
In the main component site, e.g. weir and powerhouse, is important to
evaluate necessity of core boring investigation (e.g. for water filtration
and stability of weir and for good engineering of concrete foundation of
powerhouse). Usually this important step on SHP design will be
performed after preliminary study. The cost must be considered now
Access road may be an important part of plant cost. In a correct
preliminary land survey must be added reconnaissance for plant
access evaluation . The same is valid for grid connection.
35
Planning Run-of-River SHP
Potential environmental impact of SHP plant
• Main effect of new SHP plant on preexistent
environment condition are:
– River streamflow reduction on subtended
lenght
– Fish migration obstacle
– Fish damage on turbine crossing
– Modify of river section at weir and powerhouse
sites resulting on flood risk increase
– Landscape alteration
• Another important environmental impact may be
during the construction stage of the project
May 2007
36
Planning Run-of-River SHP
Environmental impact mitigation of SHP plant
•
May 2007
The essential environmental conditions for new SHP project acceptance are
generally as follow:
– Release of certain residual flow at weir section (e.g. 10% of annual
natural mean flow)
– Installation of fish ladder across the weir section to restore fish
migration
– When is technically possible, use of low width space between screen bars
for to prevent fish passage through the turbine
– Remowable gates may be installed on weir barrage for to prevent flood
damage (e.g. inflatable rubber weir)
– Careful design for to prevent flood damage at powerhouse and tailrace
– Careful architectural design (mainly for powerhouse) respectful of site
landscape
– Plant construction engineering and yard planning can reduce the
environmental impact in construction step
37
Planning Run-of-River SHP
SHP plant authorization
• There are two main step for to obtain the necessary
authorization for the construction and operation of new SHP
plant:
– Water diversion licence
– Plant construction authorization
• Another important permit to obtain is for to deliver energy on
central grid and for relative interconnection
• Inside to above steps is the environmental impact evaluation
• Preliminary request must be do for to obtain Green Energy
benefits (e.g. Green Certificate or other grant)
May 2007
38
Planning Run-of-River SHP
SHP costs analysis – Investment cost
•
•
Each SHP plant has so particulary character so isn’t possible to
define reliable power-related global cost index
For every parts of SHP are available methods based on algorithms
for to evaluate their preliminary cost, but:
– Preliminary cost estimation is regional dependent
– Preliminary tun-up is required
– Valid only for “standard” layout
•
•
More reliable process is to evaluate investment costs with detailed
methods
Usually the investment cost are so detailed:
–
–
–
–
–
•
May 2007
Civil works (all civil and hydraulic works, access road)
Electromechanical & Electrical (from turbine-generator, up to line)
Electric line and grid connection
Engineering cost
Contingency (usually 10%)
Feasibility study and development may be not investment cost
39
Planning Run-of-River SHP
SHP costs analysis – O&M costs
• Operation
–
–
–
–
–
–
–
Water rental
Land rental (if present)
Central grid connection cost
Metering cost
Insurance cost
Surveillance and Operation labour cost
General and administrative cost
• Maintenance
–
–
–
–
May 2007
Spare parts and other consumable materials
Labuor cost for ordinary maintenance
Fault repair
Extraordinary maintenance (only for some scheduled year)
40
Planning Run-of-River SHP
SHP benefits
• Environmental benefits
– Clean energy production
– Land control
– Other uses of water
• Irrigation system for agriculture
• Municipal water system, industrial acqueduct
• Recreation use of intake’s basin)
• Economical benefits
– Energy selling
• Energy base price
• Energy incentived price (regional regulation, e.g. Green Certificate)
– Other green energy incentives
• Partial grant on investment cost
May 2007
41
Planning Run-of-River SHP
Economics - Generality
• Current SHP economic analysis model based on
Discounted Cash Flow (DCF) analysis
• Series of annual renevues (or benefits) and costs
over an assumed investment time horizon
• Economic indicators such as IRR, NPV, SP, available
for Decision Makers
• DCF is a flexible tools, adaptable for any stage of
SHP project development
May 2007
42
Planning Run-of-River SHP
Economics - Discounted cash flow (DCF) analysis
Input Data
• DCF input data are connected to:
PROJECT
– (investment cost, construction period, O&M cost, energy
production, energy destination, technical lifetime, etc.)
INVESTOR
– (capital cost, internal discount rate, equity, etc. )
REGION
– (energy price, tax, asset depreciation, water licence cost,
land rental, incentives, etc.)
May 2007
43
Planning Run-of-River SHP
Economics - Discounted cash flow (DCF) analysis – Output
• DCF output main indicators:
Net Present Value NPV
– Sum of all discounted annual cash flow over the assigned lifetime.
Must be > 0. Size dependent
Internal Rate of Return IRR
– The discount rate that brings NPV=0. Must be > investor’s internal
discount rate. Size independent
Payback Period or Simple Payback SP
– Total investment cost divided by first year benefits.
Energy production cost (currency/kWh)
– Avoided cost of energy that brings the NPV=0
May 2007
44
Planning Run-of-River SHP
Economics - Sensitivity and Risk Analysis
• Particularly necessary for SHP development in:
– Ungauged river (cash flow risk)
– Uncertain geological terrain (investment cost risk)
– Uncertain energy price market (cash flow risk)
May 2007
45
Table of Contents
•
Hydropower
•
Planning Run-of-River Small Hydro Project
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
May 2007
Land reconnaissance and maps research
Hydrology and streamflow assessment
Planning SHP resource in large area region
SHP typical scheme
Head definition
Head estimation
Using Flow duration curve
SHP turbine selection
Efficiency
Power duration curve and energy evaluation
Geology and land survey
Environmental impact / mitigation
SHP plant authorization
Cost analysys
Benefits
Economics
46
Thank You
May 2007