Thet Lin Thu

CEO @ Traverse

8 min read · November 5th 2018

Finding 20% IRR Hydropower Sites With a 5-Cent Tariff - Part 1

Today we are going to find a greenfield hydropower site using HydroDesk. It must fulfill an aggressive criterion: can it hit 20% equity IRR on a flat US$0.05 tariff?

Project Criteria

To make our lives harder, we are also going to impose all the criteria below on this site:

  1. Must not be in an environmentally protected area
  2. Backwater inundation must be far from any communities or farms
  3. The dam must be lower than 15m (an industrial benchmark for a large dam)
  4. Must be a run of river project
  5. Must be about 40MW
  6. The gross capacity factor must exceed 70% (baseload)

Other Parts of This Article

This article is divided into three parts:

  • In Part 1 (the page you are currently on), we “window shop” the terrain using HydroDesk’s prospecting tools. This allows us to make rough estimates on which river segments could fulfill our criteria.
  • In Part 2, we zero in on a candidate location and design a full project around it.

  • In Part 3, we simulate the get project and take a view on the predicted equity IRR.

Let’s get started with Part 1!

Part 1 - Prospecting on the Map

The River Slopes Layer

Any prospecting exercise begins with turning on the River Slope and Protected Areas layers:

img 001

When we do this, you will see many snippets of small colored lines which may seem confusing:

img 002

This is because the default River Length value is at 100m. Let’s see what happens when we change it to 1,000m:

img 003

Now it’s much better. River Length here means that we are measuring the slope over constant segments of 1,000 meters.

In order of descending slope, the colors denote Red [100m/1,000m], Pink [50m/1,000m], Yellow [25m/1,000m], Green [16.67m/1,000m] etc.

img 004

Now let’s zoom in to the red location near the top. The slope value we see here is 104 - which means 104m/1,000m.

img 004 2

The River (Not River Slopes!) Layer

We don’t know how big this river is. Let’s turn on the river layer.

img 005

You will see there are two sub-toggles Catchment and Flow. Catchment will be in km2:

img 006

Whereas Flow (average annual discharge) will be in m3/s:

img 007

River Slope - Filtering Out Small Rivers

We found a pretty steep place but it’s a tiny one, to the point that the satellite image doesn’t show even show the river. Now let’s change the Min Catchment (km2) under River Slope to 400km2:

img 008

All rivers smaller than 400km2 disappear:

There are now very few pink or yellow lines and there are almost no red lines! As expected big rivers are usually not steep. But after panning the map for a while, we manage to find one red segment which has a catchment of 521km2:

img 010

As we zoom in to this location, we see from the image that we found a real waterfall - with a pond right underneath. Nice!

img 011

This seems like a very picturesque recreational location for communities who live nearby. Let’s takes a quick look upstream and downstream. About 3km upstream, I find another pink segment which has a slightly smaller catchment of 475km2:

img 012

Protected Area?

Before we go any further, let’s check whether this pink segment is in a protected area by turning on the Protected Areas layer:

img 012 1

There are a few such areas but they are about 20 to 40km south of our candidate location. We seem to be in the clear for now. We should perform a check again later when we are drawing the transmission line and access roads.

River Profile and Dam Permutations

Now let’s use the Dam Permutations tool to understand the characteristics of this pink segment better. This is under Toolkit (bottom right corner):

img 013

img 014

We draw a dam crest that is perpendicular to and crosses the river line. HydroDesk will automatically find where the dam crest touches the banks of the river. We just have to draw a long line.

img 015

The following things will then happen:

  • HydroDesk will find the river line automatically

  • it will draw cross sections along the river line to figure out the

    • dam crest length,
    • dam face area,
    • inundation area and
    • inundation volume

for three different dam heights at each cross section (you can modify these heights).

Note that we did all of this in about 5 clicks!

This is a very powerful feature that you can use in a variety of ways to reduce inundation impact and construction costs. You can also imagine using Dam Permutations in low-head, high flow, flat rivers which can have a wide variety of inundation scenarios.

In this exercise though, we will just arbitrarily decide that our dam location will be at the beginning of the pink segment to exploit the natural head.

img 016

River Elevation Profile

To take a closer look at the slope of the river segment, we click on Elevation Profile:

img 017

We now see in greater detail that the first segment has 67m of gross head over a 1,000m distance. The second yellow segment is 72m/1,400m.

img 018

Combined, these two segments have a gross head of 140m over 2,400m. If we add a 15m dam and assume a design flow of 30m3/s, we found our 40MW, baseload site!

Part 1 Summary

We are going to stop here for Part 1. Here’s a summary of what we did:

  • Turn on the River Slopes layer and panned the map for high slope rivers

  • Based on a target installed capacity, filter out small rivers in the River Slopes layer

  • Ascertain candidate locations we are looking at do not encroach protected areas

  • Perform dam permutations to check for dam length, dam face area and inundation

  • Generate a river line geometry to view its elevation profile in detail

  • Our candidate location has

    • a head of 140m over a 2.4km relatively straight river,
    • a catchment area of 475km2,
    • an annual average discharge (Q50) of 30m3/s and
    • can easily be ~40MW in size for base load power (>70% capacity factor).

In Part 2, we will design a project and draw all the necessary structures around this pink and yellow segments.

Read Part 2 now.

Disclaimer: Any resemblance to any schemes or projects under development in the particular area used in this post is entirely a coincidence.

Tagged with insights | tutorials | hydropower

Enjoyed this post? Receive the next one in your inbox!