hydropower retrofitted onto existing water …...hydropower retrofitted onto existing water...

Hydropower retrofitted onto existing water infrastructure assets Marco van Dijk

Lecturer and Principal Researcher

University of Pretoria / Water Research Commission

South Africa

Presentation Layout

• How to identify assets with hydropower opportunity?

• Aspects of importance in development of water infrastructure assets.

• Integration of the hydropower with the main function of the water infrastructure asset.

Presentation Layout

• Introduction

• Classification/groupings of hydropower

• Elements (Civil, Mechanical and Electrical/Electronic)

• Assets with hydropower opportunities

• Examples of opportunities

• Policy and regulation

• Integration of assets (water & hydro)

• Summary

Introduction

• Water storage and supply schemes in SA provide an exciting opportunity for hydropower development. As of the rest of the world.

• These assets worth billions in monetary value have been constructed over decades as the country developed and expanded.

Introduction

These assets onto which hydropower can be retrofitted however have various owners:

– Government (DWS)

– Water Boards

– Irrigation Boards

– ESKOM

– Municipalities (all levels)

– Privately owned

– Mines, etc.

Introduction

• Recently DWS compiled a draft policy document which aims to allow for the sustainable development of their infrastructure (dams, weirs, canals, pipelines etc.) by hydropower developers.

• This will open up numerous opportunities in the hydropower field.

Introduction

• What is hydropower?

Hydropower is often referred to as water power. The simplest definition of hydropower would be the power that derives from the force of energy of the moving water.

• Available WRC studies KV238/10 - A High Level Scoping Investigation into the Potential of

Energy Saving and Production/Generation in the Supply of Water Through Pressurized Conduits

TT596/14 - Conduit Hydropower Pilot Plants

TT597/14 - Conduit Hydropower Development Guide

KV323/13 - Scoping study: Energy generation using low head hydro technologies

Hydropower classification

Hydropower

category

Capacity in

power output

Potential hydropower use either as a single source or in a hybrid

configuration with other sources of renewable energy

Pico Up to 20kW 10kW network to supply a few domestic dwellings

Micro 20kW to 100kW 100kW network to supply small community or building with

commercial/manufacturing enterprises

Mini 100kW to 1MW 1MW to 10MW network– electrical distribution will be at

medium voltage ranging from 11 to 33kV and transformers are

normally needed. The generation must be synchronised with the

grid frequencies (typically to 50 or 60 Hertz). Small 1MW to 10MW

NB: All installations above 10MW are classified as macro (or large) hydropower plants


• Conventional hydropower Dams, run-of-river and pump storage

• Unconventional hydropower Anything else

Linked to:

Different application

New technology

Size


http://hydro4africa.net/

Elements

Head H (variable) Depends on: • Intake location • Powerhouse location • Pipe length • Pipe diameter Flow Q (variable) Depends on: Hydrology • Catchment • Rainfall • Storage • Geology • Surface cover • Flow duration curves

Hydraulics • Demand pattern • System layout • Reservoir capacities • Flow duration curves

Q H

Elements

Diversion Channel

Intake

Pipeline

Tailrace

Powerhouse

Power Line

Elements – Civil Works

Conventional hydropower schemes consist of a number of structures or combinations of structures, depending on the type and layout of the scheme. • Impoundments/dams/weirs • Intake structures • Trash rack and sediment trap • Canals and tunnels • Penstock • Powerhouse • Tailrace All these components are not always necessary

Elements – Civil Works Impoundments/dams/weirs/reservoirs

Elements – Civil Works Intake structures

Elements – Civil Works

Trash rack and sediment trap

Elements – Civil Works Canals and tunnels

Elements – Civil Works Penstock

Elements – Civil Works Powerhouse

Elements – Civil Works Powerhouse

5kW 80kW 2.5MW 100MW

Elements – Civil Works Tailrace

2.5MW 500kW 5kW

Elements

• Mechanical Works – Turbine

– Valves

– Pipework

• Electrical/Electronic – Generator

– Transformers & switchgear

– Controls

– Grid connection

Assets with hydropower opportunities

Due to SA having a semi-arid climate, we have a vast network of large dams and water distribution infrastructure (according to SANCOLD > 4500 registered dams)


We also have a vast network of rivers - Opportunities


Operational category Type Purpose

Conveyance

Open channel

Convey fluid from one point to another

Tunnel / conduit

Aqueduct

Drops (vertical and chutes)

Culverts

Water distribution systems

Bulk sewer lines

Regulatory and diversions

Sluice gates Control water level upstream side of structure.

Navigation, Storage, Hydro. Weirs

Barrages

Flow measurement

Parshall flume

Measure flow Crump weir

Broad crested weir

Sharp crested weir

Dams Outlet works Reserve flow releases, domestic or irrigation

releases, spill/overtopping flows

Water treatment works Inlet works Treatment facility with specific opportunities at

both in- and outlet Outlet works

Waste water treatment works Inlet works Treatment facility with specific opportunities at

both in- and outlet Outlet works

Energy dissipation Drop structure Dissipate energy associated with big elevation

change, or velocity head Kinetic structure

Industrial flows Conduits and channels Water utilized in industrial activities/processes


Examples of retrofitting existing assets with hydropower

• Household supply (<1 kW)

• Waste Water Treatment Works outflow (20 kW)

• Irrigation canal (15 kW)

• Bulk water supply line (96 kW)

• Water Treatment Works inflow (

• Transfers scheme (10 MW)

• Hydraulic control structure (1.3 MW)

• Dam (? MW)

Examples of opportunities

Example – Household supply

Pico hydropower unit

10 W potential

Example - Zeekoegat WWTW


20 kW potential


5 kW developed

Example – Boegoeberg Irrigation Canal

15 kW potential (specific site)

Example – Boegoeberg Irrigation Canal

Example – Bulk water supply line (Bloemwater)

Pipeline Distance 105 km

Pipeline Diameter 1170 mm

Avg. Pressure Head 46.5 m

Avg. Flow rate 1.05 m3/s

Example – Bulk water supply line (Bloemwater)

96 kW developed (350 kW potential)

Example – Transfer scheme (Teebus)

Irrigation tunnel (5.3 m diameter, 82.8 km long)


Potential: ±10 MW


Tunnel outlet

Example – Control structure (Teebus)

Potential ±1.3MW 11 months a year 24 h/day

Example – Control structure (Teebus)

Example – Dam (Hartebeespoort)

Opportunity to generate 134 kW on a continuous basis. Site has greater potential, up to 5.7 MW, when utilizing the water released for irrigation, domestic and industrial consumption as well as excess yield available due to increasing inflows from WWTW

Example – Dam (Hartebeespoort)

Policy and Regulation

• The policy is at a very advanced stage now.

• Top Management categorised it as a Strategic Policy

• In other words there is support for the first draft

• Next step is to go through relevant governance structures approval process

• At the Ministers office, for approval to gazette and obtain public comments

• Start public consultations

SUSTAINABLE HYDROPOWER POLICY POSITIONS

Draft for internal consultation and

discussion - Version 1

• WDS analysis is governed by complex, non-linear, non-convex and discontinuous hydraulic equations.

• Adding to this complex network, the hydropower plant from which maximum benefit needs to be extracted requires a systematic procedure to evaluate the interrelationships

• A procedure could be using a multi-objective genetic algorithm, maximizing electricity generation and hence revenue and minimizing the risk of non-supply.

• Objective function: maximize the net annual income from the hydropower generation system whilst still operating the water supply system within acceptable reliability regimes

Integration of assets (water and hydro)

• Objective function 1: maximize the income from the hydropower generation system

Fj = max ρgHt,jQt,jηt,jCt,j

T

t=1

Constraints Reservoir storage limits Pipe system discharge limits Hydropower station power generation limits Hydropower station discharge limits Water balance equation


Similar to cascading reservoirs/dams


• Objective function 2: Minimize the risk of non-supply i.e. associated risk when reservoir levels are low, or operating scenarios which could compromise the system integrity (maximizing the reliability).

Ri = min αt,iβt,iPt,iIt,i

T

i=1

Reservoir operating risk evaluation Pipeline operating risk evaluation


Uitkijk reservoir

Brandkop reservoir

De Hoek reservoir

1 400

1 450

1 500

1 550

1 600

1 650

0 20 000 40 000 60 000 80 000 100 000

Chainage (m)

Ele

va

tio

n (

m)

Uitkijk - Brandkop profile

De Hoek - Uitkijk profile

HGL maximum flow


The peak rates for electricity are significantly higher than standard and off-peak rates and therefore the maximum income in this case is not generated when the total maximum power is generated for the week but rather generating maximum power during peak periods.

CHOT analyses provides Pareto-optimal trade-off curve


In summary

• The development of these hydropower schemes will require a management strategy to integrate the operation of the hydropower and the main function of the asset, which could be water supply, measuring of flow, treatment of water, etc.).

• Similarly the maintenance should be incorporated in a sustainable way with that of the asset

• It is believed that there are water assets in South Africa and elsewhere where hydro power opportunities exist

• Feasible and sustainable solutions without subsidies

• Require more successful working plants

• Require some legislative changes

In summary

The authors wish to thank the Water Research Commission of South Africa for funding the various research projects

hydropower retrofitted onto existing water …...hydropower retrofitted onto existing water...

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