Site Assessment and Design of a Small Off-Grid
Hydroelectric System at the Jama-Coaque Ecological
Reserve in Costal Ecuador
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Brett Ziter
06 October, 2013
This report includes a number of online resources embedded in links.
For an electronic copy (or if you have any questions) contact me. Cheers,
Brett
bziter@gmail.com
Abstract
Small hydroelectricity is a dependable source of renewable energy well suited for off-grid
application. A well designed system will provide years of reliable power with minimal
environmental impact. To make this happen requires considerable planning; it is necessary to
know the available water resource with confidence. This report documents an assessment of
hydroelectric potential at the Jama-Coaque Ecological Reserve in Pacific Ecuador. It includes
an estimate of power requirements at the reserve, a site assessment, and two months of dry
season flow rate measurements (a campaign that should be continued). Several possible sites
have been identified for hydroelectric installation. The best is a large waterfall that offers an
easily accessible 14 m total head and an upper limit of 320 W in the current flow conditions. The
report concludes by exploring the design of a hydroelectric system at the site. Although
incomplete, it touches on many important considerations. These include intake and penstock
design, turbine selection, and power transmission requirements. A first order cost estimate
suggests that Third Millennium Alliance can have an ideal system for less than $3000 (capable
of optimizing production with seasonal flow variations) and a serviceable one for $1500. This
does not include the cost of batteries and electrical regulation.
Table of Contents
1 Introduction!
1
2 Background!
1
3 Methods!
2
3.1 Power Requirements!
2
3.2 Site Assessment!
2
3.3 Flow Rates!
4
4 Results!
6
4.1 Power Requirements!
6
4.2 Site Assessment!
7
4.3 Flow Rates!
8
5 Discussion!
10
5.1 On Power Requirements!
10
5.2 On Hydroelectricity at Rio Chila!
10
5.3 On Hydroelectricity at Camarones Upstream!
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5.4 On Hydroelectricity at the Camarones Waterfall!
11
5.5 Summary!
11
5.6 Additional Options!
12
6 System Design!
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6.1 Power Requirements and Site Selection!
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6.2 Intake Design!
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6.3 Penstock Design!
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6.4 Turbine Selection!
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6.5 Power Transmission and Regulation!
19
6.7 A Note On Costs!
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6.8 Environmental Considerations and Noise!
21
Conclusions!
22
References!
23
1 Introduction
Small hydroelectricity has a small environmental footprint, requires limited maintenance, and
provides a constant source of energy independent of local climate and instantaneous weather. It
is a reliable source of energy for off-grid applications. At the correct site it can be more cost
effective than competitive renewable technologies.
Third Millennium Alliance is interested in a small hydroelectric system at the Jama-Coaque
Ecological Reserve in Pacific Ecuador. System requirements and power demands have not
been strictly defined. On a large scale, there is value in considering the highest level of
electricity generation possible without disrupting the local freshwater ecosystems. Whether it is
necessary to design a system at this scale will depend on the local water resource.
The objective of this project is to investigate the potential for a micro hydro project at the reserve
by completing a detailed site assessment, initiating a flow rate measurement campaign,
determining power requirements, and formulating a basic system design with the intention of
future implementation at the reserve.
2 Background
The two most important determinants of hydroelectric potential are the available flow rate and
head. Flow rate is the volume of water passing a channel’s cross section per unit time. Head is
the difference in elevation between a system’s intake and its turbine location. In small streams
and rivers flow rates can be highly variable, changing seasonally and sometimes within the day.
Any good system design must consider flow rate information throughout the year and
accommodate seasonal fluctuations.
The power available in the waterway is directly proportional to both flow rate and head, and is
expressed in the following equation,
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(Equation 1)
where Q is flow rate (most often expressed in m3/s), h is head (m), g is a gravitational constant
(9.81 m/s2), and ρw is the density of water (~1000 kg/m3 at relevant temperatures). It is
important to note that the efficiency of small hydro is usually less than 50% (whereas larger
systems commonly surpass 80%) and therefore the useful power generated by a system will be
much lower than Pavailable.
If flow rate and head are adequate, it is possible to proceed. Important design considerations
include (but are not limited to) identifying inlet and outlet locations, intake and penstock (the
pipes carrying water to the turbine) design, turbine selection, power transmission and regulation,
and installation of everything. This does not need to be complicated but it does require
considerable investigation and diligence. A well designed and properly installed system should
provide years of reliable power.
1
3 Methods
3.1 Power Requirements
I set out to estimate power requirements by obtaining two lists of relevant electronics. The first is
a list of high priority items provided by Jordan Trujillo, reserve manager and intern coordinator at
Third Millennium Alliance. The second is a list of additional items that the reserve might want to
consider. They are as follows,
Table 1. Electronics In Use or Worth Considering at the Reserve
High Priority Item
Additional Item
Reserve telephone
Simple light system
Camera batteries
Cheap cell phones
Laptops
iPhone, iPod, tablet
Multiple AA & AAA
rechargeable batteries
Small refrigeration system
Walkie talkies
Batteries for Power Tools
To obtain power estimates, I relied on product specifications, internet research, and basic
calculations. The idea is that most battery chargers have either a power rating in watts on their
technical labels or they state their common output voltage (V) and current (I). In the latter case,
power (P) can be calculated from the following equation,
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(Equation 2)
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Due to inefficiencies, the magnitude of the power put out by a battery charger will differ slightly
from the magnitude of the power it draws. For this reason, my method is not exact. However, it
should provide an appropriate estimate. From here I used a number of online sources to verify
my estimates and to provide information about other various electronics.
For future reference, it may be advisable to measure the electrical demand of any specific
product directly. This can be done using a digital power meter.
3.2 Site Assessment
Near the reserve station there are multiple waterfalls and cascades and there are two main
stream convergences that feed into the Rio Camarones. A bird’s eye view would look something
like this,
2
Figure 1. Overhead schematic of the reserve station and local waterways.
Not to scale or cartographically accurate.
An ideal location for a hydroelectric system at the reserve would facilitate power production,
maximize simplicity and minimize environmental obstruction and cost. In other words,
somewhere close to the reserve station, with high flow and head within a short run of river. Also
important is a natural inlet, or one requiring minimal landscape modification. With these
thoughts in mind, I prioritized the following measurements and observations,
• Elevation changes (necessary to determine head)
• River run (to determine the length of pipe required from inlet to turbine)
• Distances from the reserve station (for accessibility and power transmission)
• Possible inlet and outlet locations
Additionally, I measured flow rate in three locations. They have their own section following this
one.
I explored the rivers and selected three areas for detailed investigation: a large waterfall on Rio
Camarones below the reserve station (70 m downstream of the entrance gate), a cascading
waterfall on Rio Camarones to the north (accessible by Sendero Ronquillo), and a stretch of Rio
Chila corresponding with the inlet to the reserve station’s irrigation system. For consistent
nomenclature, these will be referred to as Camarones Waterfall, Camarones Upstream, and Rio
Chila, respectively.
I used a variety of methods to estimate elevation changes and river run: physical measurements
with a tape measure and 30 m length of rope, GPS altimetry, and laser optic measurements
using the TruPulse 200 laser gauge by Laser Technology Inc.
In most cases, the laser gauge was the most accurate and easiest to implement. It functions by
calculating the distance (horizontal, vertical, or true, depending on the setting) to any object in
its optic scope. It then outputs to a digital display.
3
With gauge in hand, I navigated the relevant sections of each waterway and created sketches of
the terrain, labeling all elevation changes and distances along the river. In some areas, the tape
measure was used to verify accuracy.
I identified possible inlet and outlet locations subjectively. The idea is that outlets should be
accessible, as close as possible to the reserve station, and near the base of a waterfall or
cascade to maximize head. Inlets must be upstream from outlets and elevated, striking a
compromise between high head and low pipe run. Geographic features that facilitate installation
are also important.
Distances from the reserve station were found with a combination of laser gauge measurements
and tape measure runs. For consistency, I measured from the main entrance of the station to
the most likely outlet location at each site.
3.3 Flow Rates
I measured flow rate (Q) using the common method of holding a pale of known volume (V)
under a column of falling water and recording the time (t) required to fill the pale.
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(Equation 3)
Other methods (use of stream gauging technologies, construction of a weir, floating an object
down a uniform channel) were difficult or impossible given the local topography.
The available measuring vessels were a 5-gallon paint bucket and a 1-gallon food container
(see Figure 2). I labeled the volume of each bucket in increments by pouring water from a
graduated baking pitcher. The 1-gallon bucket was preferable where flows were low; the 5gallon bucket otherwise.
Figure 2. Critical Materials for Site Assessment and Flow Rates
Flow rates were measured a minimum of once per week at various times of day throughout the
internship. There were no perfect locations. I chose the following three because they were the
best available options,
4
1. Rio Chila, immediately upstream of the Trasero trail crossing. At the trail crossing, look
upstream. There is a channel with hardly enough space to insert a bucket at an angle.
2. Rio Ronquillo, about 5 m upstream of its convergence with Rio Camarones. From Sendero
Ronquillo, cross Rio Camarones and look ahead to Rio Ronquillo. There is a tiny channel with
even less space than the one at Chila.
3. Camarones Upstream, at the base of the 4 m waterfall accessible from Sendero Ronquillo.
Images of the three locations are provided in Figure 3.
Figure 3. Flow rate measurement locations.
Unfortunately, I did not find an adequate location to measure the flow rate of Rio Camarones
downstream of its convergence with Rio Ronquillo. We will assume that this value equals the
sum of the two converging upstream flows.
On each occasion, I repeated the measurement process several times to improve the
confidence and accuracy of results. In a perfect world, I would have recorded the exact volume
and time of each trial and calculated the averages. In reality, an amount of discretion and
subjectivity was required. There were no ideal columns of falling water, and some of the flow
inevitably escaped the bucket (which was often wedged into the rocks on an angle). Also, it was
difficult to know when to stop the timer. I settled on recording best estimates to the nearest ½
liter per second (after several trials and accounting for the escaped water). For example, if I
estimated that 80% of the water entered the bucket, I would adjust my result accordingly.
On one occasion a second person assisted by operating the stopwatch and recording the data.
However, in the interest of establishing a practical routine I continued alone. (The assumption
here is that by requiring more people there is less likelihood that the campaign will continue.)
5
4 Results
4.1 Power Requirements
Here we revisit the two lists of relevant electronics. This time they are in separate tables,
accompanied by estimates of their power requirements and the sources I relied upon.
Table 2. Power Estimates for High Priority Electronics
High Priority Item
Power Requirement
Source
Reserve telephone
3W
• Input specs listed on back panel:
6V ⎓ 500mA
Camera batteries
2-4 W
• Mine charges on 2 W
• Sony LI battery specs:
Max charge current 0.9A
Max charge voltage 4.25V
• Cockeyed Science Club
Laptops
40-70 W
• Macbook Air Charger Specs: 45 W
• HP Pavilion Charger Specs: 65 W
• Cockeyed Science Club
• Coding Horror
Multiple AA & AAA
rechargeable batteries
6 W (max) to charge 4 batteries
• Kodak K620 Specs
• Energizer RECHARGE Specs
Walkie talkies
The ones at the reserve take 4
AA batteries
Table 3. Power Estimates for Electronics of Secondary Concern
Additional Item
Power Requirement
Source
Simple light system
10-20 W per LED or CFL
lightbulb
eartheasy.com
Cheap cell phones
A few watts
Alcatel charger specs: 5V ⎓ 400mA
iPhone, iPod, tablet
5-12 W depending on charger
• iPod wall charger specs: 5V ⎓ 1A
• Apple Shop
Small refrigeration system
150-200 W to run the
compressor but much higher at
startup (maybe as high as 1.5
kW)
I read about this on a variety of off
grid power sites. The MicroHydropower Forum, for example.
Batteries for power tools
Depends on size of batteries
and speed of charger. Probably
as high as 60 W per battery.
DeWalt Cordless Tools
6
4.2 Site Assessment
The following schematics and descriptions provide elevation change, approximate river run, and
distance from the reserve station at each area of study. I’ve also included information on what
lies upstream and downstream. All measurements are best estimates intended to provide an
idea of the power potential at each site.
Figure 4. Site description of Rio Chila.
• The trail crossing is 160 m from the reserve station along the available trails.
• Upstream of the irrigation inlet I measured an additional 210 m run and 37 m rise before
turning around.
• Downstream of the trail crossing I measured a 150 m run and 30 m drop to the convergence of
Rio Chila with Rio Camarones.
Figure 5. Site description of Rio Camarones upstream.
• The base of this waterfall is 165 m from the reserve station along the available trails.
7
• Upstream of the 3rd pool I measured a 46 m run and 4 meter rise to the next set of waterfalls.
These are 7 m to the top and are followed by a 150 m run and 17 m rise before a long rocky
stretch of very shallow grade.
• Downstream there is a 240 m run and 9 m drop until the following schematic.
Figure 6. Site description of Rio Camarones downstream.
• The base of this waterfall is 150 m from the reserve station out the gate and along the river. It
is 110 m following the barbed wire fence that runs west behind the bathroom.
• Upstream there is a 240 m run and 9 m rise until the previous schematic.
• Downstream, there is a long run of gradually sloping river.
4.3 Flow Rates
The following tables provide measurements to the nearest ½ liter per second. These are early
results in what will hopefully be an ongoing campaign.
Table 4. Rio Chila Flow Rate Measurements
Date (2013)
Time
Flow Rate
23 August
15:00
3.5 l/s
30 August
14:00
3.0 l/s
03 September
12:00
3.0 l/s
09 September
14:30
3.0 l/s
12 September
11:00
2.5 l/s
19 September
09:00
2.5 l/s
8
Date (2013)
Time
Flow Rate
25 September
14:30
2.5 l/s
30 September
17:00
2.0 l/s
Table 5. Rio Ronquillo Flow Rate Measurements
Date (2013)
Time
Flow Rate
23 August
15:00
2.5 l/s
30 August
14:00
2.0 l/s
03 September
12:00
2.0 l/s
09 September
14:30
1.5 l/s
12 September
11:00
2.0 l/s
19 September
09:00
1.0 l/s
25 September
14:30
1.5 l/s
30 September
17:00
1.0 l/s
Table 6. Rio Camarones Upstream Flow Rate Measurements
Date (2013)
Time
Flow Rate
23 August
15:00
7.0 l/s
30 August
14:00
7.0 l/s
03 September
12:00
6.5 l/s
09 September
14:30
6.5 l/s
12 September
11:00
6.5 l/s
19 September
09:00
6.5 l/s
25 September
14:30
6.5 l/s
30 September
17:00
6.0 l/s
For clarity, the tabular information has been plotted below. The data suggest a small decline in
flow during the available six week period. It will be necessary to continue monitoring the
situation.
9
7
Flow Rate (m3/s)
6
5
4
3
2
1
0
0
10
20
30
40
Time Elapsed (days)
Rio Chila
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Rio Ronquillo
Camarones Upstream
Figure 7. Flow rate versus time, demonstrating a gradual decline.
5 Discussion
5.1 On Power Requirements
Referencing Tables 2 and 3 it is easy to estimate how much power is required from a
hydroelectric installation. A system rated at 150 Watts would charge two laptops simultaneously
and maybe a few smaller items. 200 Watts would provide more certainty. If the plan is to have
electric lighting, appliances, and an assortment of charges, the system will need to be sized
accordingly. This decision will be in the hands of Third Millennium Alliance should they decide to
proceed with the project.
5.2 On Hydroelectricity at Rio Chila
The studied section of Rio Chila offers a total head of about 20 m within a run of 94 m. If a
hydroelectric system were designed here it might be preferable to use only a segment of this,
foregoing some of the available head in the interest of a shorter penstock.
A potential advantage of this site is that a hydroelectric intake could be collocated with the
reserve station’s irrigation system. This would minimize the number of obstructed waterways
and provide one easy access point. On the other hand, there would be risk of interference
between these systems if either were drawing too much water.
10
In any event, the available flow rate (2.0 l/s) and distance from the reserve station (160 m) do
not warrant continued study at this location. Let’s say we conservatively extract two thirds of the
flow (1.33 l/s) to generated power. Applying Equation 1, and assuming 50% efficiency, the
maximum power we could expect to obtain is ~130 Watts. Similar power can be obtained more
sensibly elsewhere (requiring substantially less than 94 m of pipe). Also, even a small drop in
the river’s flow rate between now and the end of the dry season would jeopardize these plans.
An exceptionally dry year would do the same.
5.3 On Hydroelectricity at Camarones Upstream
The studied section of Rio Camarones upstream offers 7 m head within a run of 15 m. The
measured flow rate has not fallen below 6 m/s. Here there is potential. A design flow of 4.00 l/s
(⅔ of total) in Equation 1 and 50% efficiency gives ~140 Watts. This is obtainable with a 15 m
penstock, meaning lower cost and negligible environmental impact caused by removing water
from the stream (and 50% efficiency is more believable here because there is less pipe in which
head loss will occur). In my opinion this a better option than Rio Chila at a similar distance from
the reserve station.
5.4 On Hydroelectricity at the Camarones Waterfall
The waterfall provides 14 m head within a 38 m run. It offers the highest available flow rate,
estimated at 7 l/s (found by adding the flow rates at Camarones upstream and Ronquillo). A
design flow of 4.67 l/s (⅔ of total) in Equation 1 and 50% efficiency gives ~320 Watts. This site
provides the greatest power potential of the three and offers the shortest distance to the reserve
station.
5.5 Summary
For clarity, the discussion is summarized here in a table. Note that the Power Potential column
gives an estimate of the upper limit of the power that can be expected at each site (assuming
we extract ⅔ of the current flow rate and 50% system efficiency). These parameters are still
uncertain at this point and do not include head loss. It should be used as a rough guideline.
Table 7. Summary of Maximum Power Expectations at Three Sites
Site
Features
Power Potential
Notes
Rio Chila
h = 20 m
Q = 2.0 l/s
run = 94 m
dist. to station = 160 m
130 Watts
Huge pipe run and low
flow rate make this
site impractical
Camarones
Upstream
h=7m
Q = 6.0 l/s
run = 15 m
dist. to station = 165 m
140 Watts
Low pipe run makes
this site attractive
11
Site
Camarones
Waterfall
Features
h = 14 m
Q = 7.0 l/s
run = 38 m
dist. to station = 110 m
Power Potential
320 Watts
Notes
This site has strong
potential and is closest
to the reserve station
Again, these results are pending the collection of additional flow rate data, especially further into
the dry season. It is possible that all of this becomes void if flow rates decline more than
anticipated. Speaking with locals has been reassuring. This is an unusually dry year and they do
not anticipate substantial declines going forward.
5.6 Additional Options
A final set of options involves drawing water from far above the reserve station, extracting power
at the station, and channeling the water through an outlet into Rio Camarones. I am not
necessarily in favor of these options because shorter pipe run minimizes environmental impact
and often minimizes cost. Either way, here are three possibilities:
1. If we ran a penstock all the way down from the Chila irrigation inlet to the reserve station, we
might create a small amount of useful power. Assuming a well designed system with 10%
head loss (this will be covered in a later section), an available head of 18 m (estimated with
GPS and laser gauge from the reserve station) and a design flow of 1.33 l/s (⅔ of total), we’re
looking at roughly 100 W. This is about enough to charge two laptops.
In the dry season, this would involve removing the majority of the flow from Rio Chila for
almost 250 m before its convergence with Rio Camarones. It would also involve installing
pipe of at least 2-inch diameter for more than 200 m to the reserve station and an additional
outlet system. If the penstock was not designed well (or if any unexpected head losses
occurred) it would not be feasible. If the river’s flow rate continues to decline, it will not be
feasible regardless.
2. The second option involves extracting water from Rio Chila far upstream of the irrigation inlet.
If we ran pipe an additional 200 m up the river (55 m total head) and extracted about half of
the available flow we could conceivably generate 250 W at the reserve station. We would
need a 400 m penstock with 1.5-inch or 2-inch diameter. Again, this would require removing a
lot of water from a long stretch of Rio Chila and the lack of available flow makes it risky.
3. A similar idea can be explored using Rio Camarones as a source. My measurements suggest
that an inlet 160 m upstream of the stretch shown in Figure 5 would achieve a head of 20 m
above the reserve station. To reach the station, this would require a penstock of at least 300
m and 2-inch diameter. Here, a small percentage of the river’s flow rate would provide the
necessary power. For example, assuming 10% head loss and 50% efficiency, we could
generate ~200 W by taking only 2.25 l/s. This is probably the most viable of the three options
but still carries environmental risk and requires considerable investigation. It may be
something to discuss with a professional turbine supplier.
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6 System Design
I’ve decided to select an appropriate site and carry out a basic system design, as far as I can
take it given the available resources and time constraints. This will not be as technical as it
should be. It will provide is an educational experience for myself and will aim to raise awareness
of the various components and considerations involved in getting hydroelectricity to the reserve.
I will leave details about construction and installation mostly untouched. These will require
appropriate knowhow and also timeliness: the final decisions about installation are best left to
the people involved when it happens. A lot of credit for this section goes to Home Power
Magazine. They offer a fantastic series of articles on small hydro design considerations.
6.1 Power Requirements and Site Selection
It is well documented above that the large waterfall on Rio Camarones below the reserve station
is the site with the greatest power potential within a short run of river. This is also the closest site
to the station and will not interfere with the irrigation system in Rio Chila or the popular natural
setting provided by Rio Camarones upstream. Above the waterfall there are a number of pools
that facilitate intake design. Below it, there is a natural catchment to reintroduce the water.
Given the available water resource and the desired range of electronics, Third Millennium
Alliance should aim for a system of at least 200 watts. This size conveniently corresponds with
the smallest range of commercial turbine products I’ve been able to find (which I’ll discuss later).
It must be noted that a larger system (in the range of 300+ watts) is likely possible at the site
and might be preferable to the people in charge.
6.2 Intake Design
A good intake should be structurally sound, well installed, and accessible. It must serve its
purpose of diverting water from the river into the penstock and it should be well screened to
avoid blockage and prevent hazardous debris from entering. It must either be removable and
reparable or capable of withstanding the worst possible flow conditions while fixed in place.
There are many common intake designs for small hydroelectric systems. Research and
common sense suggest that a dam or any significant landscape modification should be avoided
if possible. Siphon intakes are discouraged because of frequent problems (they lose their
suction as energy is removed from the flow at the turbine end) and a shallow rocky riverbed
makes a variety of other installations difficult.
I like a system that relies on a siphon to divert water from the river but avoids the problem of
suction loss. This is accomplished by channeling water from a natural pool at the top of the
waterfall into a basin installed on the shoreline about one meter below (in a tree, for example).
Here, the penstock is attached. This design circumvents the reason not to have a siphon. It also
minimized penstock length and moves major components out of the river where they will not get
washed out during wet season. The only damageable part of the system will be the least
valuable and easiest to repair. The only disadvantage I see is that we lose ~1 m from our net
head by placing the catch basin below the highest inlet pool.
I have provided a schematic of the intake design in Figure 8.
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Figure 8. Intake system design schematic. Not to scale at all.
The five highlighted components are as follows:
1. Intake Box
This should mimic the intake design of the irrigation system. It should be fixed in a natural
pool in the river, secure enough to withstand the worst of winter conditions.
2. Inlet Pipe
This can be plastic hose pipe of an appropriate diameter to provide the necessary flow rate.
Diameter can be calculated using Bernoulli’s equation for incompressible flow (Equation 4),
where we assign our reference points above the inlet pool and at the outlet of the pipe, as in
Figure 9.
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(Equation 4)
where v = velocity (m/s); g = gravitational constant (9.81 m/s2); z = elevation (m); P =
pressure (kg/m⋅s2); ρ = density of water (1000 kg/m3); and ∑hi = the sum of all head losses in
the pipe.
Figure 9. Points of analysis for inlet pipe calculations.
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The pressure terms cancel out (both are atmospheric) and we can assume that v1 = 0 (the
height of the pool remains constant). If this is a relatively short length of pipe we can assume
negligible head losses. We are left with,
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(Equation 5)
Thus we have our outlet velocity. From here we calculate the minimum necessary cross
sectional area of the inlet pipe,
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(Equation 6)
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(Equation 7)
and from here we calculate the minimum necessary pipe diameter,
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If the intake pipe is long and head losses are substantial, the calculation becomes slightly
more complicated (but follows the same steps). I will discuss head loss in greater detail in the
following section on penstock design. For now we’ll proceed without it. A drop of Δz = 1 m
from inlet pool to catch basin and a design flow of Q = 4.67 l/s (⅔ of our current flow rate)
indicates a necessary pipe diameter of 1.5-inches (rounded up). In practice in might be
necessary to play with these parameters during installation to ensure that at least 4.67 l/s
pass through the screen into the catch basin.
3. Filter Screen
This must be designed small enough to filter out any debris that might get lodged in the
nozzle pointed at the turbine runner. It should also filter out smaller particles capable of
damaging the runner. Something smaller than ¼-inch should suffice.
4. Catch basin
This is an area for water to collect before entering the penstock. Dimensions are mostly
arbitrary, although it must be tall enough that the penstock remains free of air bubbles. It
should be slanted across the top so that falling water naturally removes debris from the
screen.
5. Outlet Pipe
This is a PVC pipe sized according to penstock design calculations.
6.3 Penstock Design
A well designed penstock (pipeline) is one of the most important components of a hydroelectric
system. An inefficiently design fails to maximize the power available at a site.
15
Common penstocks are smooth plastic PVC or polyethylene. It is important to use a pipe of
sufficient pressure rating. At our site (ρgh ≈ 125 kPa ≈ 18 psi) we have nothing to worry about
with either of these choices. Thin walled polyethylene (like the black pipe at the reserve) is
probably a good choice as it can be installed in one long section and maybe even weaved
through trees. This avoids the need to anchor a pipeline to the riverbed.
It is critical to size the penstock properly. Friction along the walls of small pipes will cause
energy losses to accumulate. In an undersized headstock the advantage of head is negated. An
oversized penstock will not have this problem but will be excessively expensive.
Energy losses that occur as fluid moves through a pipe are expressed as head losses and
calculated by a combination of hydraulic principles and empirical formulas. A good penstock
design keeps head losses to a minimum. They should not exceed 10-15% of total head in a
small hydroelectric system (Home Power, 2012).
In this section I will document some of the important head loss considerations and how they are
calculated. Credit goes to the European Small Hydropower Association’s (ESHA) Layman’s
Guidebook on How to Develop Small Hydropower and Frank White’s textbook Fluid Mechanics.
Head loss due to friction (hf) can be calculated from the following equation, derived by Darcy
and Weisbach for incompressible steady flow in pipes,
!
!!
!
!
!
!
!
!
(Equation 8)
where L is the length of pipe, D is diameter, v is velocity and g is the gravitational constant. The
friction factor (f) is a dimensionless number dependent on the flow characteristics and the pipe
size and material. For turbulent flow, f is commonly found using the Moody Diagram.
To use the Moody Diagram, one must determine the roughness height (e) of the desired pipe
material. This can be found in tables in the literature. I’ve used a value of 0.003 mm for
polyethylene (ESHA, 1998). From here, e/D can be calculated and used to select the
appropriate curve on the diagram. It is also necessary to determine the Reynold’s Number (NR =
Dv/μ where μ is the kinematic viscosity of water, 1.31x10-6). This is a dimensionless number
used to characterize the turbulent characteristics of the flow.
Alternatively, Hazen and Williams provide an empirical approach for calculating hf,
!
! !
!
!
!
!
(Equation 9)
where C is an empirical coefficient named after the authors (C ≈ 140 for plastics). This method
is common for pipes larger than 5 cm diameter and velocities lower than 3 m/s.
A third option (also empirical) is the Manning Equation,
16
!
!
!
!
!
!
!
!
(Equation 10)
where n is the Manning Coefficient, also available in the literature (for polyethylene, n = 0.009).
I used Equations 6-9 to select an appropriate pipe size for our penstock. In the calculations I
used a design flow of Q = 4.67 l/s and a conservative penstock length of 40 m (the distance
down the waterfall is about 25 m).
Table 8. Friction Head Loss Caused by 4.6 l/s in 40 m of PVC or Polyethylene Pipe
Pipe Diameter
Friction Head Loss
Percent of Available (13 m) Head
1-inch
110 m
856%
1.5-inch
16 m
123%
2-inch
4.0 m
31%
2.5-inch
1.4 m
11%
3-inch
0.56 m
4.3%
3,5-inch
0.29 m
2.2%
4-inch
0.15 m
1.2%
Looking at these results, anything smaller than a 2.5-inch pipe is too small. 2.5-inch is probably
acceptable but 3-inch pipe might be a better option. A well designed penstock should not
exceed 10-15% head loss (and there will be other small sources of head loss in the system).
This agrees well with a guideline provided by Home Power Magazine that flow rates
approaching 75 gpm (4.8 l/s) can use 2.5-inch pipe but flow rates between 75 and 110 gpm (7.1
l/s) should use 3-inch pipe.
Other important considerations are the head losses caused by turbulence. These are losses
that occur as a fluid passes through bends, valves, entrances, expansions and contractions and
other modifiers of the flow geometry. For any common situation (i) it is possible to find an
experimental coefficient (ki) that expresses the resulting head loss as a percentage of the kinetic
energy in the flow,
!
!
!
!
!
!
!
!
!
(Equation 11)
I will not document all of these possibilities. Better information can be found in ESHA, White, or
in any good fluid mechanics textbook. In cases with low flow velocity (like our case) these
losses are small compared with the potential losses caused by friction. What is important is that
the penstock should be as straight and as simple as possible. Bends and elevation decline
should be gradual. It should be well anchored and have a shut off valve and a pressure gauge
at the turbine end. A great way to finalize penstock design is to consult a turbine supplier.
17
6.4 Turbine Selection
With a design flow of 4.67 l/s, a net head of 11.5 m (after removing 1 m for the inlet design and
10% for head loss), and assuming 50% efficiency, we can expect about 260 W. This is a
reasonable set of parameters for a commercial turbine product. I’ve located a few companies
that cater to the micro hydroelectric market:
PowerSpout in New Zealand has been responsive and knowledgeable. I was quoted $1600
including shipping for a unit capable of handling a wide range of site conditions and power
outputs. At the time of contact they did not have a dealer in Ecuador. The contact I’ve been
talking with is Michael Lawley in NZ; michael@ecoinnovation.co.nz. He would undoubtedly aid
with system design.
KWK in Germany has a solid online presence and a suitable product for our site but they
provided very little information.
PowerPal in Canada has a good reputation and a presence on the international market. They
have a distributor in Quito who quoted me $500 USD for a 200 W turbine. His contact details
are as follows: Milton Balseca; mbalseca@uio.satnet.net; 0999724140.
When deciding on a turbine it is advisable to seek as much information as possible and to get
multiple opinions. The one I spent the most time researching is the PowerPal MHG-200HH. It is
a Turgo turbine well suited for the head and flow rate conditions at our site (Cobb, 2013) rated at
200 W. It is attached to a permanent magnet alternator and comes with an electronic load
controller to output ready-to-use electricity at the charge station. Selection of this turbine would
require a few alterations to my design parameters (260 W is a bit high and could damage the
alternator).
While PowerPal is a reasonably priced option, I don’t love it. Its design does not control the flow
rate from the turbine end of the penstock. As a result, its output can be highly variable. This
means there is risk of damage to the alternator (and our electronics) in high flows.
An ideal turbine would allow us to extract the maximum possible power in dry season and
produce higher power in wet season. This is a common practice implemented by installing
various flow regulating nozzles at the turbine end of the penstock. Switching nozzles allows the
user to manage the flow rate hitting the turbine runner and consequently alter its power
production. Now that I finally get around to documenting this, PowerSpout is sounding like a
good option. I regret not spending more time researching it.
This section should provide a good starting point on the microhydro turbine market. I
recommend continuing the search and contacting as many leads as possible. Alternatively, DIY
turbine design would make a good intern project given the right candidate and budget. If Third
Millennium Alliance decides to explore this route, there are many examples of small turbines
designed with Pelton wheels or with pumps operated in reverse. There are also complete sets
of calculations for selecting turbine class, jet velocity, nozzle size, etc, that can be found in an
appropriate reference such as ESHA, 1998.
18
6.5 Power Transmission and Regulation
Power transmission and regulation deserve as much attention as penstock design. A poorly
designed electrical system can result in inefficiencies and unnecessary capital costs. Once
again Home Power Magazine has great information on this. I will do my best to cover the
basics.
There are two options for our system. One is to use a turbine that generates messy three-phase
AC, run power to the house or charging station, and rely on an electronic load converter (ELC)
to create safe (useful) power. This is the PowerPal method. The other option is to use a turbine
that outputs either three-phase AC or DC voltage and wire it to a battery bank with an
appropriately sized inverter to meet peak power demand. This will minimize the risk of
damaging electronics (or the alternator itself).
The latter method appears to be far more common for small off grid applications. However,
these applications usually involve running high power appliances, not just charging batteries.
Our situation is unique in this sense. Unfortunately, I have to leave this issue in the air. I have
not had enough time away from the reserve to tackle this. Any good turbine supply person
should be able to help.
Either of these options require a diversion load to prevent the alternator from overheating or
battery bank from overcharging. This is commonly a large water heater wired into the system.
Third Millennium Alliance might consider installing it over the shower.
As for sizing transmission wires from the turbine to the house, let us recall the equation used in
Section 3 for identifying the power requirements of electronics,
!
!
!
!
!
!
!
!
!
(Equation 2, revisited)
Clearly, higher voltage generated by the turbine requires a smaller current to carry a given
amount of power. Smaller current means less energy lost during transmission. It allows the user
to save money by purchasing smaller wires. The correct wire size will therefore depend on the
voltage generated by the turbine. The equation that governs this is,
!
!
!
!
!
!
!
!
!
(Equation 12)
where Plost is the amount of power dissipated during transmission and R is the resistance of the
wire. The power dissipated during transmission should not be more than 5%. Resistance is a
material property that depends on wire type and thickness. Tables are readily available that list
the resistance of copper transmission wire by gauge. Therefore, the process to size
transmission wire is to calculate the current that will travel through it (I = P/V), calculate the
maximum allowable resistance (R = 0.05*Ptotal/I2) and look up the appropriate wire gauge in a
table.
To make the current as low as possible it is often appropriate to use two or three lengths of
smaller gauge wire in place of one large wire. For example a current of 10 amps can be
conducted in two 5 amp channels, effectively quadrupling the maximum allowable resistance,
19
lowering the required gauge, and cutting cost. It should be noted that the smallest
recommended wire gauge is 14 AWG (Home Power, 2012).
I played around a lot with these calculations. Sizing wire for our site (wire run of ~110 m) should
not be difficult. The numbers will depend on turbine selection and whether we’re channeling
high voltage AC electricity or low voltage DC. Either should be fine provided we avoid the lowest
available (12 V) models.
6.7 A Note On Costs
A local hardware store in Pedernales sells black polyethylene tubing at the following sizes and
prices,
Table 9. Polyethylene Pipe Prices in Pedernales
Diameter (inches)
!
Cost per 100 m (USD)
1
$39.75
1¼
$65.00
1½
$75.00
2
$139.00
Note: I’m not sure if these are outer or inner diameter
The pipe we are interested in is 2½ or 3-inch diameter polyethylene. I could not find these sizes
nor was the internet of any help for estimating prices. I decided to plot the data,
Cost (USD)
140
105
70
35
0
0
0.5
1.0
1.5
2.0
Diameter (inches)
Figure 10. Cost versus Diameter for Extrapolating Upward
I fit this data with as many trendlines as possible to obtain as many price estimates as possible.
I used 3-inch pipe in my calculations rather than 2.5 to err on the side of more expensive. This is
what the estimates look like,
20
Table 10. A Range of Possible Price Estimates for 3-inch Pipe
Trend
Trend Line Equation
Resultant Price
Linear
y = 97.5x - 60.4
$232.10
Polynomial
y = 41x2 - 27.5x + 28.5
$315.00
Power
y = 40.5x1.74
$273.93
Exponential
y = 13e1.19x
$461.72
$320.69 (avg)
This puts the price of 3-inch diameter polyethylene tubing at about $320 per 100 m. Of course
this may or may not be a good estimate and it does not mean the pipe will be easy to locate. But
if this estimate is at all reliable and we only need half the amount, we’re looking at a pipeline for
under $200 (before the cost of valves and miscellaneous pieces).
Using the equations in Section 6.6 with P = 260 W, a wire run of 110 m, and various voltage
options, I was able to calculate the wire gauge we would need in a variety of situations. It should
be possible to design a transmission system on the smallest recommended wire size (14 AWG)
at a cost of about $100 (not including conduit). Even if a system were in place that would allow
us to double our power in the winter the upper end of wire cost looks like $300. Wire prices
come from a table I found in a Home Power article from 2012. They may be dated and not
specific to Ecuador but I can’t imagine the prices here being higher.
These calculations allow us to obtain a rough estimate of the total system cost. Assuming a
turbine on the order of $500 to $1500 (PowerPal on the low end and something like the
PowerSpout on the high end), pipe and wire together on the order of $500, a bunch of
miscellaneous (valves, fittings, intake design, etc), and rounding up, we’re probably looking at a
total cost not higher than $3000 for an ideal system and maybe $1500 for a serviceable one, not
including the cost of batteries and electrical regulation.
6.8 Environmental Considerations and Noise
For systems on this scale, there do not appear to be any major environmental concerns. A river
should never be completely stripped of its water but there is not an objective rule for how much
water is too much. I’ve been using an arbitrary design flow of ⅔ of the total flow rate for small
stretches of river. This should not be an issue at our site unless TMA decides to draw water in a
long pipeline from far above the reserve station.
A well design intake system will not allow fish or other aquatic life from entering the penstock
and thus fish kill is a non-issue.
Noise is a minor concern. I read in one turbine manual that small hydro turbines should be kept
“at least 30 m away from your home” (PowerSpout, 2012).
21
Conclusions
This report documents my internship project: an assessment of hydroelectric potential at the
Jama-Coaque Ecological Reserve in Pacific Ecuador. It includes an estimate of power
requirements at the reserve, a site assessment, and the initiation of a flow rate measurement
campaign.
Results indicate that the most likely site for a hydroelectric installation is the large waterfall at
Rio Camarones immediately below the reserve station. This site offers a flow rate of 7 l/s (in
October, 2013) and 14 m total head in a short stretch of river. An upper limit of 320 W can be
expected at this location in the dry season. To ensure flow rates remain close to their current
level, it is important that the measurement campaign continues, especially as we move further
into dry season.
The report ends with a look into the design of a hydroelectric system at the site. Although
incomplete, this touches on many important design considerations, including intake and
penstock design, turbine selection, and power transmission requirements. A first order cost
estimate suggests that Third Millennium Alliance can have an ideal system for less than $3000
(capable of ramping up production with seasonal flow variations) and a serviceable one for
$1500. This does not included the cost of batteries and electrical regulation. No concrete needs
to be poured.
22
References
First, a note of apology for a lack of quality references and for not including them throughout the
report as rigorously as I would have liked to. Limited computer access made this difficult and
time caught up with me. Here are my references:
Balseca, M. Email consultation, August 2013.
Cobb, B. R., Sharp, K. V., “Impulse (Turgo and Pelton) turbine performance characteristics and
their impact on pico-hydro installations,” Renewable Energy, Vol. 50, 2013, pp. 959-964.
Engineering Toolbox, Pipe Pressure Ratings. URL: http://www.engineeringtoolbox.com/pipespressure-rating-t_40.html [cited September 2013]
European Small Hydropower Association (ESHA), Layman’s Guidebook on How to Develop
Small Hydropower, 2nd Ed., prepared for the Commission of the European Communities
Directorate-General for Energy, 1998.
Home Power Magazine, Microhydro Power Design and Installation [various articles]. URL:
http://www.homepower.com/articles/microhydro-power/design-installation/ [cited August 2013]
Lawley, M. Email consultation, August 2013.
Lubitz, W. D., Email consultation, August 2013.
Micro-Hydropower Forum, [online advice and discussion furum], affiliates unknown. URL:
http://www.microhydropower-forum.com [cited August-September 2013]
PowerPal, “Use and Care Instructions for Your New High Head Micro-hydroelectric
Generator,” [Users’ Manual], Asian Phoenix Resources Ltd., Canada, 2008.
PowerSpout, “Pelton (PLT) Installation Manual,” Version 1.3, EcoInnovation Ltd. 2012.
White, F. M., Fluid Mechanics, 5th Ed., McGraw-Hill, Toronto, Canada, 2003.
23