HomeMy WebLinkAboutHome Water Supply Micro-Hydro Feasibility Study 2009,
CITY OF HOMER
WATER SUPPLY SYSTEM MICRO-HYDRO
FEASIBILITY STUDY
DECEMBER 2009
Consulting
Contents
Introduction .......................................................................................................................................... !
Microhydro Stations ............................................................................................................................. 2
Energy Production ................................................................................................................................ 3
Construction Cost Estimate .................................................................................................................. 5
Benefit/Cost Analysis ........................................................................................................................... 7
Summary .............................................................................................................................................. 9
Appendices
A Water Supply System
B Energy Production Spreadsheet Sample
List of Figures
Figure 1 -Average Daily Flow ............................................................................................................ !
List of Tables
Table 1 -Micro hydro Sites .................................................................................................................. 2
Table 2 -Microhydro Energy Production ............................................................................................ 4
Table 3-Microhydro Capital Cost Estimate ....................................................................................... 6
Table 4 -Micro hydro Benefit/Cost Analysis ...................................................................................... 8
..
Introduction
EES Consulting (EES) was asked to examine the City of Homer's (City) East Trunk water
supply line at three pressure reducing stations (PRV) to determine the feasibility of adding
hydroelectric generation at each of these PRV stations. We have reviewed . the water treatment
plant flow data for the East Trunk. Figure 1 illustrates a one year record of average daily flows.
The City also advised that there is significant variation of flow within a day, as is typical for
water supply systems. The data that the City provided indicates that on a typical July day the
flow varied from a peak of 855 GPM down to a minimum flow of 116 GPM .
Figure 1 -Average Daily Flow
City of Homer
Avo. Doily Flow East Trunk
f2~r-------------~~-r~HHHH~~~~------------+-~
!!.
1 ~200 h~~lt~tl1tm~tf<tr-------------'-~lnl'~Nilrt.~~#tlll.l a
1~~~--~~~--~--------------------------~~~4-~
1·Jor>-08 2G-Feb-08 1G-Apr-08 19-Ju~08
Dolo
1
7-Sep-08 27-<let-08 16-De~
Microhydro Stations
Three existing pressure reducing stations (PRV) were identified in the City's system as locations
for microhydro sites, all of which are located on the East Trunk water line. Table 1 presents the
basic information for these three sites. Appendix A presents the water supply system with the
pressures for the various PRV stations.
Table 1 -Microh
Upper site
Middle site
Lower site
delta P-
delta P =
delta P =
61 H-
77 H=
95 H=
• I
140.91 Eft-
177.87 Eft=
219.45 Eft=
•
0.7 Fix Flow=
0.7 Fix Flow=
0. 7 Fix Flow=
0.4 Installed capacity=
0.4 Installed capacity =
0.4 Installed capacity =
As can be seen from the table above, the units are quite small with installed capacity of less than
6 kW. The sizing presented in Table 1 was based on a fixed flow of0.4 CFS (180 GPM), which
maximized energy production. Energy production was evaluated as described below.
2
Energy Production
Based on the head at each PRV station, a reaction-type turbine is indicated. This could be a
custom built Francis machine or a centrifugal pump-based design, which is similar in operation
to a Francis turbine. Francis turbines typically would have adjustable wicket gates, allowing
operation over a range of flows. Fixed geometry turbines, such as pumps, run in reverse can only
operate at a single flow. The generators are assumed to be induction generators, due to their
small size and ease of operation. A capacitor bank would likely be required on each machine to
stabilize line power factor. The generators would be 480V , 3 phase machines (or single phase if
small enough). If the local power line is 12 .5 kV, a small step-up transformer would be required
to raise the voltage to 12.5 kV. Some protective relays would be required to shutdown the
machine in case of short circuit or other fault. A very simple system is assumed to be able to
monitor each generator remotely, but this system would not allow detailed load controls or
remote adjustment of the machine, due to the cost of such systems.
Using the daily flows, a spreadsheet model was developed to calculate energy for two scenarios:
1. Each microhydro site has a variable flow recovery turbine-generator unit that can operate
over the entire range of daily average flow. This type of turbine would be similar to a
Francis turbine with adjustable wicket gates. For such a small turbine, it is not likely that
a variable flow unit can be procured that could cover the full range of flows, as Francis
turbines can typically only operate between 20% and 1 00% of its design full load flow.
However, for modeling, it was assumed the full flow range could be accommodated.
2. Each microhydro station has a turbine-generator, which can only operate at a constant
steady flow . This type of turbine is a fixed-flow machine, which in this size ranges would
typically be a centrifugal pump run in reverse . This is a very common application for
these types of units, and there are several manufacturers that supply this type of machine.
The energy production model (see Appendix B for sample output) of the pipeline system was
constructed using EXCEL software. A daily time-step model was developed that projects daily
energy generation using daily inflows obtained from the daily average flow data. For each day
in the model, inflow at the turbine inlet was taken from the flow data file. This is then capped at
the maximum flow capability for the turbine, which is a function of the size of the turbine
selected in the model. Any available flow in excess of turbine capacity would be bypassed back
into East Trunk through the existing PRV. Turbine operation is then modeled, taking into
account the available flow , head available at the turbine, and variation in machine efficiency
(both turbine and generator) depending on percent load. Daily generation is calculated, and then
generation from each day is added up to provide monthly and annual total expected gross
generation.
3
However, this total needs to be adjusted for other expected losses. The model allows the user to
make deductions to the gross generation for the following:
• Step-up Transformer and transmission line losses-set at 1% and 2% respectively
• Plant Outage for planned and unplanned maintenance-set at 3%
• Use of energy for station service (heat, lights, controls)-set at 0.5 kW
The results of the energy production study, based on the spreadsheet analysis, are presented in
Table 2.
333
101
210
0.7
0.2
0.5
Energy (kWh) 34308
Total kWh
43307
131045
53431 22870 28869 35618
87357
As can be seen from the table above, if variable flow turbines could be procured, average annual
energy would be 131,045 kWh. If fixed flow turbines are utilized, energy production drops to an
average of 87,357 kWh (both numbers are before deducts for losses and outages). With fixed
flow turbines, there are some days when there is insufficient flow for the turbine to operate.
This analysis utilizes the average daily flows and it is known that the flow variation within a day
is significant. An analysis based on using hourly flow data would undoubtedly indicate a
significant reduction in average annual energy production as there would be extended periods of
time when flows would be too low to generate with fixed flow turbines, or would exceed the
turbine capacity. If storage is built into the system below the lower site, average daily flows
could be kept much more constant throughout the day and then flows could be re-regulated
below the lower site.
4
. .
Construction Cost Estimate
We have reviewed the City's Reconnaissance Report capital cost estimate. We believe the cost
could be reduced somewhat by mounting the turbine-generator equipment in a prefabricated
enclosure in a slab-on-grade arrangement. This would significantly reduce the cost as the large
precast vaults could be eliminated.
Canyon Industries was contacted for a budgetary quotation for a turbine-generator equipment
package. Canyon provided the following for the three turbine-generator sets. Each turbine
equipment package will consist of the following components:
• Cornell turbine, in horizontal direct drive configuration
• Marathon Electric, 240 V AC, 60 Hz, 1 ph, induction generator
• Bray turbine inlet valve, hydraulic actuator open, spring closure
• Lot flanged inlet and outlet transition piping
• Hydraulic power unit for inlet valve opening, 120 VAC
• Custom structural steel turbine/drive/generator mounting frame
• Rex Omega direct drive couplings with custom drive guard
• Switchgear/controls package to parallel the generator with the utility grid and provide
protective relays to North American utility grid standards for projects this size. Control
package to run and shut down turbines based on signal from existing station logic.
Turbine will automatically shut down on loss of grid power. An auto restart feature may
be added to restart the system when grid power returns. The control panel will be PLC
based and capable of communication with the City's existing SCADA system by
telephone line.
Budget Estimate Upper site, as described ................................................ $54,770.00
Budget Estimate Middle site, as described ................................................ $55,955.00
Budget Estimate Lower site, as described ................................................. $54,260.00
Crating and transit from Deming, WA to Homer, AK is estimated at $2,000 per crate.
Start-up assistance is offered at the field service rate of $1,100.00 per day. Travel is charged at
the same rate. Food and lodging are charged at cost.
Table 3 below presents an updated feasibility cost estimate.
5
·.
Mob/Demobilization LS $ 10,000 $ 10,000
Inlet/outlet piping modifications 3 $ 9,000 $ 27,000
Hydro turbine-generator package 3 $ 58,000 $ 174,000
Above ground enclosures/concrete 3 $ 5,000 $ 15,000
Equipment installation 3 $ 9,000 $ 27,000
F&l SCADA equipment 3 $ 3,000 $ 9,000
Utility distribution line work 3 $ 1,000 $ 3,000
Site restoration/reseeding 3 $ 1,500 $ 500
Subtotal $ 269,500
Contingency 20%
Subtotal
Engineering/eM 15%
p
Total
6
•.
Benefit/Cost Analysis
Using the estimated construction cost and the average annual energy production, we completed a
simple benefit/cost ratio calculation to determine the feasibility of the Microhydro Project.
Similar to the City's Reconnaissance Report we assumed the following:
• Discount rate is 3%
• Operation and maintenance (O&M) costs are 1% of construction cost
• O&M costs escalate at 3% per year
• The value of the annual energy production is $9,800 based on the HEA power purchase
rate of$0.12 per kWh and the losses/outage time.
Table 4 presents the benefit/cost analysis. As can be seen from the analysis, the benefit/cost ratio
is significantly less than one.
7
. .
1 $ 371,910
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
$ 3,719
$ 3,831
$ 3,946
$ 4,064
$ 4,186
$ 4,311
$ 4,441
$ 4,574
$ 4,711
$ 4,853
$ 4,998
$ 5,148
$ 5,303
$ 5,462
$ 5,625
$ 5,794
$ 5,968
$ 6,147
$ 6,332
$ 6,521
$ 371,910 $ 72,216 $ 444,126 $ 9,801 $ 145,815
$ 9,801
$ 9,801
$ 9,801
$ 9,801
$ 9,801
$ 9,801
$ 9,801
$ 9,801
$ 9,801
$ 9,801
$ 9,801
$ 9,801
$ 9,801
$ 9,801
$ 9,801
$ 9,801
$ 9,801
$ 9,801
$ 9,801
BENEFIT COST RATIO= 0.33
8
Summary
Using fixed flow turbines at each site is likely the only practical installation for such small flows.
We do not believe that it would be practical to procure variable flow turbines in this size range.
Estimated average annual energy production is significantly lower that originally estimated by
the City in its Reconnaissance Report. The City's report indicated average annual energy
production of 85,000 kWh at each site.
One of the fundamental problems to making this feasible is the wide diurnal variation in flow.
This wide flow range cannot be easily accommodated in a single turbine/generator. A large
storage tank would need to be installed somewhere at the lower end of the system, then flows in
East Trunk could be held more constant throughout the day, increasing generation significantly.
The cost of adding storage has not been considered in this analysis.
The energy analysis performed in the report assumed the use of average daily flows, so without a
storage tank as noted above, the energy production would even be less than stated.
Because of the low annual generation, the calculated benefit/cost analysis indicates that the
project is not feasible. If the flows are not levelized by the addition of a storage tank, as
discussed above, the project has an even lower benefit/cost ratio. If the PRV stations need to be
rebuilt at some point in the future, then this project may be feasible.
9
:
Appendix A
Water Supply System
1-----wTP::J
ovvnoy •vun --
it--1.0 MG Tank
Section Comer ______.
Ridge line
U RL 113·50
2"KO 60
3"KO 50
6" 40
HillTop
O HT 65-25
2"KO 47
3"KO 36
:ti!!!..D:l!.!l 6" 25
(8"CIP to A-Frame) MidHm
{ MH 134-21
2"KO 21
3" KO 16
6"KO 11
(Main/Mountainview)
l!i!!!..In!.!!l ( AF 112·49
2"KO 49 1
Hillside Pl. F'ViewAve. 3"KO 44 ~
6" 39
{BartleHSt.)
{. IBTLT 110 ·55
{West Hil Rd .} 2" 46
~ 7 WH 67-30 6" 39
114" 30 3" PO 79 .M!in..§1
3" 25 ~ -6" 20
~
f_.o.-{Olson Lne} {
Sterling Hloy O BG 115.561
{Sterling Hwv.l 2" 56
SH 64-26 6" 51
1W' 26
3"KO 21
6" 16
NO ITES:
All PRV valves are Cla-Val Model ~1.
PRV valves with KO trim are designated "KO"
--
...................
.wtlll!!l!!
(12" PVC to Elller PRV Slation)
(10" PVC EF to BT PRV)
(10" DIP BT PRV ·E. End Rd .)
Weal Trunk
.26MG AF Tank
(Main/Danviow Sis.) · (Kachemak Way}
MD 60 • 34 I U KK 97-36 I
2" 34 I 2" 36 I 6" 29 6" 31
Pioneer Ave.
{Lucky Shot St.)
(Main St.} ()LS 104-441
JS 94-31 I 2" 44 I ,
2" 31 I 6" 39
6" 26
.76 MG Selt Tank~-•
A-I
(Fireweed Ave.)
71 EF 66·30
2"KO 30
3"KO 25
6" 20
(East Hill Rd .)
0 SB 103-26
2" KO
East Trunk 3'KO
6"
{East HiH Rd .)
11 BT 145-50
2"KO 50
3"KO 45
6" 40
(East Hill Rd.}
1 HL 106 -26
2"KO 26
3"KO 23
6" 16
{Lake Street)
HE 102 ·36
1W' 36
3" 31
6" 26
~PR19{Ramp4)
A Small Boat Harl>or
~PR20 (Ramp2)
Pioneer Dock
{Ben Wahers Lne.)
0 LK 95-41 I
2" 41 I 6" 36
City ofHo1
Pre88U!'!! F
--• I
0
22
2
PO
East Trunk
East End Rd .
i
--o-PR22 {Ramp 6)
Q!!
..
...
Appendix B
Energy Production Spreadsheet Sample
. '
City of Homer-Microhydro feasibility study
12-Aug-09
Energy Production Estimate
ITE PRVPRESSUREDROP •HEAD(FTf EFFICIENCY ' ''F'LOW!CFSI . <>·' CAPACITYIKVVl~ · •
Upper site delta P • 61 H= 140.91 Eft= 0.7 Fix Flow= 0.4 Installed capacity =
'clcla lite -P· nH• 1n.87 Ell< 0. 7 Fax Flow: 0.4 ll\llllled c:.pecity.
Low..-lite -P· 95 H• 219.45 Ell= 0.7Fax~ 0.4 lllllelled
Variable flow Fixed flow
Mcn1l1 E. Trunk E. Trunk E. Trunk Upper Site Middle Site I..Dwer Site Upper Silo Middle Site Lower Site
Date MGD GPM CFS kW kW kW kW kW kW
1.JorH!e 0.256 178 0.4 3.3 4 .2 5 .2 0.0 0.0 0.0
2.JirHI8 0.252 175 0.4 3.3 4.1 5.1 0.0 0.0 0 .0
~·rHJe 0.311 218 0.5 4 .0 5.1 8 .3 3.3 4.2 5.2
4-Jan-08 0.275 191 0.4 3.8 4.5 5.5 3.3 4.2 5.2
S-Jan-08 0.254 178 0.4 3.3 4.1 5.1 0.0 0.0 0.0
e-Jan-08 0.247 tn 0.4 3.2 4.0 5.0 0.0 0.0 0.0
7.JarH!e 0.258 179 0.4 3.3 4 .2 5.2 0.0 0.0 0.0
thlarH!e 0.281 181 0.4 3.4 4.3 5 .3 3 .3 4.2 5 .2
9.JarH!e 0.2n 189 0.4 3.5 4.4 5 .5 3 .3 4 .2 5 .2
10.JarH!e 0.284 197 0.4 3.7 4.8 5.7 3.3 4.2 5 .2
11.JorH!e 0.282 182 0.4 3.4 4.3 5 .3 3.3 4.2 5.2
12.JarHJe 0.278 192 0.4 3.8 4.5 5 .8 3.3 4.2 5 .2
1~orH!e 0.203 141 0.3 2 .8 3 .3 4.1 0.0 0.0 0.0
14.JorH!e 0.344 239 0.5 4.4 5 .8 8 .9 3.3 4.2 5 .2
15.JarHI8 0.308 213 0.5 4.0 5 .0 8 .2 3.3 4.2 5 .2
1thlarHI8 0.289 187 0.4 3.5 4.4 5 .4 3.3 4.2 5.2
17.JirHI8 0.277 192 0.4 3.8 4 .5 5 .8 3.3 4.2 5 .2
1thlorH!e 0.274 190 0.4 3.5 4 .5 5.5 3.3 4.2 5 .2
19.JarH!e 0.282 182 0.4 3.4 4.3 5 .3 3.3 4.2 5.2
20.Jon-08 0.258 179 0.4 3.3 4.2 5 .2 0.0 0.0 0.0
21.Jan-08 0.259 180 0.4 3.3 4.2 5 .2 3.3 4.2 5 .2
22.JarH!e 0.284 197 0.4 3.7 4.8 5 .7 3 .3 4.2 5 .2
2~arHI8 0.278 192 0.4 3.8 4 .5 5 .6 3 .3 4.2 5 .2
24.JarHI8 0.283 197 0.4 3.7 4.8 5.7 3.3 4.2 5 .2
25.JarH!e 0.290 201 0.4 3.8 4.7 5 .8 3.3 4.2 5.2
28-JarH!e 0.249 173 0.4 3.2 4.1 5 .0 0.0 0.0 0.0
27.JorH!e 0.250 174 0.4 3.2 4.1 5 .0 0.0 0.0 0 .0
2thlarH!e 0.274 190 0.4 3.5 4.5 5 .5 3.3 4.2 5 .2
29.JirHl8 0.275 191 0.4 3.6 4 .5 5 .5 3.3 4.2 5 .2
30.JarHI8 0.283 197 0.4 3.7 4 .6 5 .7 3 .3 4.2 5 .2
31.JarH!e 0.284 197 0.4 3.7 4.8 5 .7 3.3 4.2 5 .2
1-Fo~ 0.297 206 0.5 3.8 4.8 8 .0 3.3 4.2 5 .2
2-F~ 0.280 181 0.4 3.4 4 .2 5 .2 3.3 4.2 5 .2
3-Fal>48 0.266 185 0.4 3.4 4.3 5 .4 3.3 4.2 5 .2
4-Fal>48 0.272 189 0.4 3.5 4 .4 5 .5 3.3 4.2 5 .2
5-Fo~ 0.277 192 0.4 3.8 4.5 5 .8 3.3 4.2 5 .2
8-F~ 0.252 175 0.4 3.3 4.1 5 .1 0.0 0.0 0.0
7-Fob-08 0.281 181 0.4 3.4 4.3 5 .3 3.3 4.2 5 .2
8-Fe~ 0.266 185 0.4 3.4 4 .3 5 .4 3.3 4.2 5.2
~81>48 0.248 1n 0.4 3.2 4 .0 5 .0 0.0 0.0 0.0
10-Fob-08 0.224 158 0.3 2.9 3.7 4.5 0.0 0.0 0.0
11-Fa~8 0.204 142 0.3 2.8 3.3 4.1 0.0 0.0 0.0
12-Fe~B 0.267 185 0.4 3.5 4.4 5.4 3.3 4.2 5.2
13-Fo~ 0.258 179 0.4 3.3 4 .2 5 .2 0.0 0.0 0 .0
14-Fo~ 0.278 194 0.4 3.8 4 .8 5 .8 3.3 4.2 5 .2
15-Fob-08 0.315 219 0 .5 4.1 5 .1 6 .3 3.3 4.2 5.2
18-Fob-08 0.282 182 0.4 3 .4 4.3 5.3 3.3 4.2 5.2
17-Fo~ 0.288 201 0.4 3.7 4.7 5 .8 3.3 4.2 5 .2
18-Fa~ 0.239 166 0.4 3.1 3 .9 4.8 0.0 0.0 0.0
1~eb-411 0.326 226 0.5 4.2 5.3 6 .6 3.3 4.2 5.2
B-1
3.3
4.2
5.2