30
Wood Pellet Conversion Feasibility Analysis for the Northport School District Prepared by: Washington State University Energy Program Revision 2 March 2018 Northport, Washington
Wood Pellet Conversion Feasibility Analysis for the Northport School
District
Prepared by:
Washington State University Energy Program
Revision 2
March 2018
Northport, Washington
© 2017 Washington State University Energy Program
This publication contains material written and produced for public distribution. Permission to copy or disseminate
all or part of this material is granted, provided that the copies are not made or distributed for commercial
advantage and that they are referenced by title with credit to the Washington State University Energy Program.
WSUEEP15-013 • April 2016
i
Acknowledgments The authors wish to thank Don Baribault, Superintendent, and Rob Mawdsley, Maintenance
Manager, of Northport School District, (SD) for allowing us to review the site conditions and
evaluate the systems that are currently installed on the Northport school campus.
Disclaimer This project was supported by Grant No. WTED-9601 awarded by the U.S. Forest Service. Points of view
in this document are those of the author and do not necessarily represent the official position or policies
of the U.S. Forest Service. Grant funds are administered by the Office of Economic Development &
Competitiveness, Washington State Department of Commerce through grant number F14-52216-003.
Neither the U.S. government nor any agency thereof, nor the Washington State University, nor the
Washington State Department of Commerce, nor any of their employees, makes any warranty, express
or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness
of any information, apparatus, product, or process disclosed, or represents that its use would not
infringe privately owned rights. Reference herein to any specific commercial product, process, or service
by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its
endorsement, recommendation, or favoring by the U.S. government or any agency thereof.
Site Information
Name Northport Elementary School
Location 404 10th St., Northport, WA 99157
Electric Utility Avista Electric Company
Site Contacts
Contact Name Don Baribault
Contact Phone 509-732-4430 ext. 131
Contact Email [email protected]
Technical Contact
Contact Name Rob Maudsley
Contact Phone 509-994-8053
Washington State University Energy Program Contacts
Address 905 Plum Street SE, PO Box 43165 Olympia, WA 98504-3165
Renewable Energy Specialist David Van Holde, P.E., CEM
Contact Phone 360-956-2071
Contact Email [email protected]
ii
Contents
EXECUTIVE SUMMARY .......................................................................................................... 1
INTRODUCTION .................................................................................................................... 4
Wood Pellet Heat in Schools Pilot Program............................................................................... 4
Purpose of Study ....................................................................................................................... 4
PROPOSED WOOD PELLET BOILER SYSTEM ........................................................................... 5
Pellet Boiler System Size and Selection ..................................................................................... 6
Biomass boiler sizing and design options.................................................................................. 7
FINANCIAL ANALYSIS ……………………………………...................................................................... 11
Financial Analysis Assumptions................................................................................................. 11
FACILITY DESCRIPTION AND ENERGY USE ............................................................................. 13
Detailed Facility Description ..................................................................................................... 13
Energy Requirements and Costs ............................................................................................... 16
Electrical Energy, Power Demand and Typical End Uses........................................................... 17
Thermal Energy Us e at Northport Elementary School ............................................................... 19
WOOD PELLET BOILER SPECIFICATION ................................................................................. 20
Components............................................................................................................................. 20
Part 1 Products: Commercial Boilers and Accessories.............................................................. 21
HEATING ALTERNATIVES TO WOOD PELLETS........................................................................ 24
Base Case: Replace existing boiler with new oil boiler on failure……………………….................... 24
Use mill residue (wood chips) as fuel for the system ............................................................... 24
CONCLUSIONS .................................................................................................................... 25
iii
Tables Table 1. Facility Energy Profile .................................................................................................... 3
Table 2. Estimated Operating Savings and Simple Payback........................................................ 3
Table 3. Three years oil use Northport Elementary School boiler………………………..................... 5
Table 4. Most recent two years oil use and average cost of #2 fuel oil over last 2 years ......... 6
Table 5. Pellet main and fossil trim boiler loading model........................................................... 7
Table 6. LCCA with assumptions ................................................................................................. 11
Table 7. Budgetary installed costs estimate................................................................................ 11
Table 8. General financial assumptions…………………………............................................................ 11
Table 9. Life Cycle Cost (cash flow) Analysis Model .................................................................... 12
Table 10. Energy profile summary…………….................................................................................. 17
Photos Photo 1. Northport schools complex............................................................................................ 1
Photo 2. Example ‘containerized’ pellet boiler package for retrofit............................................... 8
Photo 3. Interior of a ‘containerized’ pellet boiler package......................................................... 8
Photo 4. Example of pellet storage silo........................................................................................ 8
Photo 5. Weil McLain 704MBTU Boiler........................................................................................ 14
Photo 6. Representative classroom air handler……………………………............................................... 14
Photo 7. Robertshaw pneumatic heating/cooling controls…………............................................... 14 Photo 8. Heating/cooling water circulation pumps...................................................................... 14
Photo 9. Common area air handler (attic)…………......................................................................... 15
Photo 10. New hot water boiler in Gym/Multipurpose/VO-Ed Building…..................................... 15
Photo 11. Rooftop heat pumps in Northport HS…………………....................................................... 16
Figures Figure 1. Representative biomass boiler mechanical systems..................................................... 10
Figure 2. Historical #2 Heating Oil Pricing .................................................................................... 11
Figure 3. Average monthly electric consumption and peak demand........................................... 18
Figure 4. Electrical energy use as a function of temperature....................................................... 18
Figure 5. Electrical peak power demand as a function of temperature...................................... 18
Figure 6. Typical K-12 Energy Uses by Area*................................................................................ 19
Figure 7. Northport Elementary School estimated monthly #2 fuel oil use................................. 19
This Page is Intentionally Blank
iv
1
Executive Summary The Washington State University (WSU) Energy Program conducted an energy analysis and site visit in
preparation for designing a densified biomass (wood pellet) heating system for the Northport School
District Elementary School. While on site, observations were also made at the high school and
multipurpose / vocational education building.
This Revision 1 of the original project Feasibility Analysis that was presented in April 2017 is submitted in
August 2017. Several added findings and further design developments require reporting updated
assumptions and recommendations at this time.
Photo 1: Northport Schools complex
This Revision 1 report adds the recommendation of an expanded and interconnected hydronic (hot
water or HW) heating system that would serve the elementary school (as described in the original
report) and the Gym/ Vocational Education (Gym/ Vo-Ed) building.
One other option was generally considered, but not analyzed in depth:
A pellet or wood-chip fueled boiler serving both the High School and Elementary buildings at Northport SD.
The site staff became familiar with wood pellets based on discussions with Mr. David Van Holde, of
WSU’s staff.
The site visit focused on proper sizing of the potential wood pellet heating system, and discussions to
eliminate possible fatal flaws to such a system in this location, as well as a review of the existing boiler
and its operation. Implementing efficiency measures can help reduce the size and reduce the
operating cost of a modern wood pellet heating system. In reviewing these systems, the following
objectives were addressed:
1. Develop an understanding of current systems; and
2. Gather sufficient information to complete the wood pellet system feasibility analysis
Because the Northport School District was selected for the Washington State funded Wood Pellet Heat in
Schools Pilot Program, this report discusses the technical and financial feasibility of installing a pellet
biomass boiler for normal building heat.
2
The Northport Elementary School and the Gym/Vo-Ed buildings already have hydronic heating systems
and there were no asbestos abatement problems identified associated with the scope of the proposed
project. Both of these conditions should reduce the cost of a consolidated wood pellet heating system.
Our general recommendations are summarized as follows:
WSU EP recommends that the Northport SD integrate the recently installed (2010) Gym/Vo-ED
boiler and hydronic heating system with the existing Elementary School hydronic heating
system, by joining their currently separate hot water heat distribution piping systems in an
appropriate manner. This will allow the use of the existing high capacity (1,700,000 Btu/hr., or
1700 MBH) fuel oil boiler currently supplying the Gym/Vo-Ed building to act as trim and backup
boiler for one consolidated heating system with the pellet boiler as the primary heat source. In
this configuration, most (> 93%) of the annual heating energy will be supplied by the packaged
pellet boiler system. This should result in lower fuel costs and environmental impacts, while still
providing sufficient backup heat.
The Northport School District should consider installation of a wood pellet boiler using the
available funds. The tables, graphs, and figures in this analysis primarily reflect analysis for the
proposed wood pellet boiler option.
The Northport School District should continue to closely assess the condition and operation
of its hydronic heating and air distribution systems and controls associated with the
elementary school and gym/Vo-Ed before installing a new pellet boiler. This should be
included in the scope of work of the hydronic heating contractor as due diligence when
interconnecting the two building heating systems. While no complaints were registered with
respect to these systems during our visit, a detailed systems condition review of them has
not been performed. At minimum, modest controls updates improvements will certainly be
needed to ensure the new system can operate efficiently. The WSU Energy Program can
support these assessments and investigate separate funding for corrections and
improvements, as needed, including discussions with the Office of the Superintendent of
Public Instruction regarding funding. This recommendation is important for two reasons:
– A properly functioning HVAC system will free up some the maintenance person’s time. A
well automated wood pellet boiler has minimal workload impact on maintenance (mainly
ash disposal and checking wood pellet supply); and
– If a new wood pellet boiler were installed and worked properly but other aspects of the
heating system were deficient, the new system would have trouble delivering the heat to
the classrooms. As noted above, there is no evidence that this is the case, but due
diligence requires a review.
Findings from the energy analysis are summarized in Table 1 and Table 2.
Table 1. Facility Energy Profile
Purchased Power (All buildings) 454,560 kWh/yr.
Baseline Boilers (for both the Elementary School and the Gym/Vo-Ed Building : 3-year average fuel Oil Use
1,372 MMbtu/yr. = 9872 gallon/yr.
Biomass Boiler: Wood Pellets Use 1,040 MMbtu/yr. = 74 ton/yr.
3
Trim Boiler for Biomass System: 59 MMbtu/yr. = 427 gallons/yr.
Table 2. Estimated Operating Savings and Simple Payback
Base Case Wood Pellet
Boiler Alternative Baseline Boiler: Fuel Oil Price
$/MMBtu
$/gallon
$2.44/gal.
$17.53
Wood Pellet Boiler: Wood Pellets Delivered Price / Ton $/MMBtu
$/ton
$167.00 $ 10.12
Base Electric Rate, $/kWh $0.109 $0.109
Heating Fuel Costs, $/year $24,088
$13,480
Plant O&M Costs, $/year $500
Operating Savings, $/year $10,608
Total Capital Costs $300,000
Total Grants $250,000
Simple Payback Before Grant, years 28
Simple Payback With Grant, years 4.5
4
Introduction
Wood Pellet Heat in Schools Pilot Program
During the 2013 legislative session, $500,000 was allocated in the Capital Budget to fund the installation
of wood pellet boiler systems in two K-12 schools. For the purpose of the demonstration, the supporting
legislation required that one school be located in Western Washington and one in an Eastern
Washington county bordering British Columbia or Idaho. Wood pellet heating systems are an efficient
and cost-effective approach to providing thermal energy from a single fuel source – a wood pellet boiler.
This is especially true when compared to existing fuel oil boilers that are several decades old.
Northport Elementary High School in Stevens County has been selected to participate in the Wood Pellet
Heat in Schools Pilot program, which provides funding to convert the existing oil heating system to a
wood pellet solution as the primary heat source.
The Northport School District, located in Northport, Washington has expressed an interest converting
their elementary school to a wood pellet heat system, providing the system will effectively heat the
school, fuel can be reliably sourced and is easy to manage, maintenance efforts are not increased,
operating costs are significantly reduced and capital costs to the Northport School District are relatively
small.
Purpose of Project
The purpose of this feasibility study is to provide a detailed estimate of the technical and economic
feasibility converting the fuel oil boiler at the Northport Elementary School to a modern wood pellet
heating system. This study also examined the use of wood chip equipment, recognizing that the use of
wood chip fuels may have higher fuel management requirements and possibly air quality concerns. This
study includes preliminary engineering design alternatives, financial analysis, next steps, and
conclusions/recommendations.
This study provides a mature evaluation of biomass boiler technology as a basis for the school board to
decide whether to expend funds to install a new heating system (it is not, however, an investment grade
study). This detailed analysis includes:
An energy analysis of plant operations based on monthly average utility billing records,
A simplified life cycle cost analysis (LCCA),
Equipment information and plant schematic, and
A detailed design and specifications for interconnecting the elementary school and Gym/Vo-ED hydronic heating systems, with heating supplied by either the existing Gym/Vo-Ed boiler, the new pellet boiler or both boilers, as needed. See related reference documents available from Northport School District:
o E-01 Northport - 2017-11-15 - stamped set.pdf -:- The Electrical drawings for the piping / pumping of the interconnection/integration tasks as proposed.
o M0.1-6.4 Northport 2017-11-20 - stamped set.pdf -:- Mechanical drawings for the piping / pumping of the interconnection / integration tasks as proposed.
Installed system cost estimates based on consultations with a representative experienced wood pellet system design/build firm (this firm was contracted specifically to help with the design and is not specifically endorsed in any way to perform the work).
5
Proposed Wood Pellet Boiler System It is recommended that the Northport School District install a 350,000 Btu/hr. (350MBH) wood pellet
boiler. This Revision 1 to the report specifically also recommends interconnecting the hydronic heating
systems in the Elementary School and Gym/Vo-Ed buildings using an appropriate piping system
including new pumps and limited added controls as required. In this case, the existing 1700MBH oil
hot water ‘boiler’ used to heat the Gym/VO-Ed building can supply sufficient heat for both buildings,
acting as both trim boiler and as a backup for the pellet boiler. Most of the cost for this project will be
supported by a $250,000 grant available. Depending on the condition of the existing hot water heating
equipment and final system design details associated with the piping interconnection in particular, it is
expected that the district is likely to need to contribute between $10,000 and $25,000; however it is
estimated that approximately $30,000 would need to be spent in the next 5 years to replace the aging
boiler, so that avoided cost was reduced in financial estimates.
Energy Analysis and Heat Load Assumptions
In order to estimate the economics of a biomass heating system and to size it properly, a monthly
thermal energy analysis of this school’s system was performed, based on averaged data from three fiscal
“school” years of oil use (2013 – 2016), and two years electrical energy use (2014-2016). An extended
study of oil use was necessary to normalize the irregular purchases typical of oil systems and to capture
representative use over several heating seasons with varying conditions.
Table 3. Three Years Oil Use in both Northport Elementary and Gym/Vo-Ed Boilers
However, because oil prices have fallen continuously during this period, we only considered the last two
years when averaging fuel prices. The average cost for #2 fuel oil in this period is shown below in Table 4.
for contrast. Note that pellet prices have remained stable.
6
Table 4. Most recent two year use and cost of #2 fuel oil
The school elementary and Gym/Vo-Ed buildings both use fuel oil hot water ‘boilers’ and a 6000 gal
underground fuel oil storage tank. Three years of fuel use data and the average annual use from both
buildings by the boilers are shown above, in Table 3.
It is important to note here that in the earlier analysis, mis-identification of billing records provided led to
the incorrect conclusion that all of this oil use was for the elementary school alone. A correction to this
information revealed that these records represent fuel oil consumption for BOTH the elementary school
and the Gym/Vo-Ed hot water boilers. This critical finding, along with research on both school buildings’
peak heating loads led to the conclusion that the existing 1700 MBH oil boiler recently installed in the
Gym/Vo-Ed build can support both buildings under design conditions. This conclusion is supported by a
check sum of Gym/Vo Ed system delivery capacity added to the capacity of the existing elementary school
boiler system, as described below:
Below is an explanation for the peak heating load calculation used to confirm that the existing Burnham
1700 MBH (1,700,000 Btu/hr.) hot water boiler can support both buildings:
Peak heat delivery capacity is limited by both hot water pumping capacity as well as boiler sizing:
1. In the case of the elementary school, the boiler capacity rating absolutely limits the heat that
can be supplied to the building: the current peak heat delivery is limited to 704,000 Btu/hr.,
per the nameplate capacity of the existing elementary school boiler.
2. The Gym/Vo-Ed building is of somewhat larger than the elementary school (19,380 sf, vs.
17,557 sf) and its annual oil use represents about 64% of the total heating oil used, versus
approximately 36% by the elementary school as revealed by tracking conducted by Rob
Maudsley, the district maintenance person. Therefore, the much larger 1,700,000 Btu/hr.
boiler would not be expected to be the heating capacity limiting factor. However, for the
Gym/Vo-Ed building, the current peak heat delivery is limited at a much lower capacity by
the hot water circulating pumps: Using an assumed 20 degree drop between the hot water
supply and return temperatures (as specified by several heating coils in the system) with a
specified maximum flow of 85 GPM by the hot water pumps in the Gym water loop, the
maximum deliverable heating capacity is 849,660 Btu/hr. to that system.
3. Combining these two peak heating capacities, the total coincident heating delivered cannot
be greater than 1,553,660 Btu/hr., from both buildings. This is 91.4% of the 1,700,000
existing Gym/Vo-Ed hot water boiler capacity in the maximum design case.
Pellet Boiler System Size and Selection
Many factors influence the selection of the 350,000 Btu/hr. wood pellet boiler, including:
Thermal loads during peak winter months and percent of heat to be supplied by the wood pellet
boiler: Most importantly, biomass boilers should be operated at full power as much as possible,
and modulated only within moderate ranges. For this reason, hot-water heat storage is usually
7
employed for short demands and an easily modulated “trim” boiler (such as the existing Gym oil
boiler) provides heat for extended peak heating in cold snaps and low load periods in spring and
fall. However, the biomass boiler still assumes more than 90% of the annual heating loads.
Thermal storage options and space for storage;
Size requirements of the system’s thermal load from the above analysis compared to market
equipment options; and,
Design of the boiler equipment to handle wood pellets
Biomass boiler sizing and design options Wood energy boilers are typically substantially undersized relative to load, so as to operate them at full
load as much as possible; in order to support peak heat load requirements, both a heat storage system
and a high efficiency and power trim boiler are also included in the system. At the same time, the wood
boiler produces more than 90% of the annual heat energy. Below (Table 5.) are sample of calculations of
the sort employed by specialist system designers in this business, as an illustration. Building load
requirements are derived from past fuel use and distributed according to site Heating Degree Days, as a
proxy for typical weather conditions that drive building thermal loads:
Table 5. Pellet main and fossil trim boiler-loading model
What is shown above is an estimate, used for energy economics to determine feasibility. For actual
design calculations and bid, the designer will apply a more refined model, using parameters matched
closely to the actual equipment and system being specified.
Based on the loads presented and typical design guidelines for biomass boilers (e.g.: size biomass boiler
for base-load at 50% - 75% of design load), a pellet boiler of 350,000 Btu/hr. was suggested. Since a high-
output trim boiler will be included (as proposed, the existing 1,700,000 Btu/hr. Gym fuel-oil boiler), as
well as a significant heat storage system, the chances of the system not being able to meet peak thermal
demand for an indefinite period are nil, thus there is no occupant comfort risk. Further security is
8
provided by a design that interconnects and integrates the two building heating systems supplied by the
one boiler capable of heating both buildings. If the pellet boiler runs out of fuel or fails, the oil boiler can
take over and carry heating loads. The greatest risk in wrongly estimating the size of the biomass boiler
is operating the boiler for extended periods under capacity, which would result in poor performance and
shorter life as a result of cycling too much and operating at low fire, where the boiler is less stable. This
risk ironically occurs when too large a biomass boiler is specified.
A third significant value associated with the proposed design is that the piping changes required to
interconnect and integrate the two buildings can be done as a construction separate project, either at
the same time as the pellet boiler is installed or any time before. Since the buildings can operate
indefinitely without the pellet boiler, this provides for flexibility in contracting the work.
Retrofit pellet boiler packages such as proposed for Northport are often installed in modular packages
outside the existing boiler room. This allows the manufacturer or design / build firm to pre-assemble and
test the system before delivery at their factory, and more importantly, to control and standardize almost
all aspects of the physical equipment installation. By minimizing the need to demolish existing boiler
equipment and then design and install a custom configuration to fit in its previous place, costs are greatly
reduced. Photos 2 and 3 show an example of such a “containerized” pellet boiler systems. This is the
strategy recommended for Northport’s project.
Photo 2: Example of a ‘containerized’ pellet boiler package for retrofit
9
Photo 3: Interior of a ‘containerized’ pellet boiler package for retrofit
Pellet fuel is typically stored in a silo adjacent to the boiler system enclosure, similar to the one shown
Photo 4). Loading is direct from a truck, using material handing technology similar to grain transport. In
the concept design for the pellet boiler system at Northport, it is anticipated that the pellet storage
system will be integrated in the pellet boiler “container” reducing added costs and providing a lower
hopper for easier loading with pellets.
Photo 4: Example of Pellet Storage Silo
As proposed, the wood pellet boiler will tie into the existing fuel oil boiler plant supply and return hot
water piping in the boiler room, minimizing the need to disturb the existing boiler room. The existing
boiler and new pellet boiler should have separate circulating pumps for flow through each piece of
equipment, similar to Figure 1 (next page):
10
Figure 1. Representative biomass boiler mechanical systems
(including heat storage and trim boiler - not a specific design for this site)
Image Courtesy of the Biomass Thermal Energy Council, John Siegen haler, PE
11
Financial Analysis A Life Cycle Cost Analysis was performed for the proposed biomass boiler system. These results,
summarized in Table 4, show a significant financial benefit for the school district. Details of our life-
cycle analysis are shown in Table 6.
Table 6. LCCA with incentives
Biomass Boiler
Project Internal Rate of Return (IRR) Before Grant -9%
Project IRR With Grant 36%
Simple Payback 2.8 years
Financial Analysis Assumptions
Estimated capital costs of the wood pellet boiler are presented in Table 5 with references for sources of
equipment cost estimates. Other financial assumptions are summarized in Table 6.
Table 7. Budgetary installed costs estimate
Wood Pellet boiler (equipment and installation) $104,000
Fuel storage, fuel feed and management $170,000
Controls, and other assumed necessary upgrades to accommodate boiler $25,000
Present value of assumed avoided cost of boiler replacement in 5 years ($25,878)
K-12 Wood Pellet Grant (lump sum in year 1) ($250,000) Total Capital Costs minus Grant $23,122
Table 8. General financial assumptions
Project
Project Life 15 years
Discount Rate 3%
Escalation
General Inflation 2.5%
Electricity, Relative to General Inflation 0.0% Fuel Oil, Relative to General Inflation
The Federal Energy Information Agency (EIA) has increasingly focused on volatility vs. inflation in short- and long-range analyses.
In lieu of fuel oil prices relative to general inflation, Figure 2 indicates multi-year weekly fuel oil
prices from the EIA.
Figure 2. Historical #2 Heating Oil Pricing
12
Table 9. Life Cycle Cost (Cash Flow) Analysis Model
USE
D IN
REP
ORT
+++
"W
isew
ood
Type
" Pe
llet B
oile
r Rep
lace
men
t Mod
el ~
50%
Cap
acity
w/
Trim
Boi
ler:
Syst
em R
epla
cem
ent E
stim
ated
Cos
ts a
nd E
cono
mic
sCa
pita
l Cos
t Est
imat
es:
Data
Sou
rces
Pelle
t Sys
tem
350
MBT
U Pe
llet +
Trim
Boi
ler
(w/ f
uel h
andl
ing
and
stor
age)
: 27
4,00
0.00
$
ba
sed
on S
impl
e Es
timat
ed P
acka
ged
Pelle
t Sys
tem
Inst
all (
Pelle
t boi
ler i
n pr
e-en
gine
ered
ship
ping
uni
t
Addi
tiona
l R&
R an
d co
mpa
tibili
ty u
pgra
des t
o ex
istin
g ho
t wat
er h
eatin
g sy
stem
s:
25,0
00.0
0$
SW
AG -
Assu
med
HVA
C/Pi
ping
Reh
ab a
nd S
impl
e Co
ntro
ls
Capi
tal C
ost R
educ
tions
:
Stat
e K-
12 D
ensif
ied
woo
d de
mo
proj
ect g
rant
: 25
0,00
0.00
$
Gr
ant -
ava
ilabl
e &
qua
lifie
d
PV o
f Avo
ided
cost
of b
oile
r/eq
uip
repl
acem
ent (
$30,
000
5 ye
ars i
n fu
ture
)$2
5,87
8.26
Req
uire
d No
rthp
ort S
choo
ls or
oth
er fi
nanc
ing
(Firs
t Yea
r Out
lay)
: 23
,121
.74
$
(Che
cksu
m) U
npai
d:-
$
Fina
nce
Econ
omics
:
Sim
ple
Payb
ack:
2.
76
Year
s:N
ote
that
repl
acem
ent H
VAC
only
hav
e pa
ybac
ks if
they
are
sign
ifica
ntly
mor
e ef
ficen
t tha
n ex
istin
g sy
stem
s
Estim
ated
15-
year
Cas
h Fl
ow (Y
ear):
0
12
34
56
78
910
1112
1314
15
Annu
al P
aym
ent o
n ot
her s
ourc
e fin
ancin
g:
0(2
,228
)$
(2,2
28)
$
(2,2
28)
$
(2
,228
)$
(2,2
28)
$
(2,2
28)
$
(2
,228
)$
(2,2
28)
$
(2,2
28)
$
(2,2
28)
$
(2,2
28)
$
(2
,228
)$
(2,2
28)
$
(2
,228
)$
(2
,228
)$
Annu
al E
nerg
y Co
st S
avin
gs:
010
,608
$
10,6
08$
10
,608
$
10,6
08$
10
,608
$
10
,608
$
10,6
08$
10
,608
$
10
,608
$
10,6
08$
10
,608
$
10,6
08$
10
,608
$
10
,608
$
10,6
08$
16-'1
7 Sv
gs17
-'18
Svgs
17-'1
8 Sv
gs18
-'19
Svgs
19-'2
0 Sv
gs20
-'21
Svgs
21-'2
2 Sv
gs22
-'23
Svgs
23-'2
4 Sv
gs24
-'25
Svgs
25-'2
6 Sv
gs26
-'27
Svgs
27-'2
8 Sv
gs28
-'29
Svgs
29-'3
0 Sv
gs30
-'31
Svgs
Cash
Flo
w S
trea
m:
(23,
121.
74)
$
8,38
1$
8,38
1$
8,38
1$
8,38
1$
8,38
1$
8,
381
$
8,
381
$
8,
381
$
8,38
1$
8,38
1$
8,38
1$
8,38
1$
8,38
1$
8,38
1$
8,38
1$
Net A
nnua
l Sav
ings
: 8,
380.
60$
Fina
nce
Inte
rest
Rat
e:
5%
Assu
med
Disc
ount
Rat
e:
3%
Net P
rese
nt V
alue
: 76
,925
$
Inte
rnal
Rat
e of
Ret
urn
(IRR)
: 36
%
13
Facility Description and Energy Use
Detailed Elementary School Facilities Description
Northport School District, is – believably – located in Northport, Washington, There are two schools in
the Northport School District: 1) Northport Elementary School with conditioned floor space of 17,557 sq.
ft. serves approximately 100 students in grades K-6; and 2), Northport High School is in a separate
building of 7,682 sq. ft. with 60-70 students. These two schools share a Gym/Multipurpose/VO-Ed building
of 19,380 sq. ft. The district has a number of additional structures, most notably a building that was
constructed as a performing arts annex, but now houses a number of offices. This building has
approximately 3,000 sq. ft. of conditioned space, although no exact size was available. Also, there are
three portable classrooms and an outbuilding containing the Elementary school boiler and an electric
service switch room. All of these buildings are clustered closely around a central courtyard, occupying a
total area of perhaps a half city block. Parking and fields surround the Northport school buildings.
The primary focus of this report is consideration of replacing the boiler in the heating system for
Northport Elementary School and interconnecting this new system with the Gym/Vo-Ed building, using its
recently installed boiler as trim and backup boiler for the new pellet boiler, which would supply most heat
to both buildings. Consistent with school designs of the time, the elementary school is centered around a
shared central “pod” containing library and media resources. Nine classrooms wrap around this core, and
there is space approximately equivalent to two more classrooms occupied by district administrative
offices, health and educational resource functions, such as testing rooms, “Title 1” spaces , etc.. It appears
that space uses – especially in the elementary school core – have been significantly reallocated to meet
changing need over time, as compared to the original architectural plans studied.
The elementary school is heated with a 1970’s vintage Weil-McLain oil boiler (Photo 5) rated at 704,000
Btu/hr. as well as a direct expansion chiller. Both sources provide hot (or chilled) water, depending on
conditions, through a shared 2-pipe distribution system, to constant volume air handlers located in the
school (Photo 6). These air handlers operate largely independently under pneumatic thermostatic control
of the zones (mostly classrooms) that they serve, presenting thermal load to the boiler or chiller. The
space thermostats directly control water valves, fans and dampers on the air handlers through existing
independent pneumatic control modules (Photo 6 & Photo 9) These air handlers also have outside air
mixing, however control logic of air mixing and damper control have not been assessed. Supply water
temperature is set in the boiler room by an original simple central pneumatic Robertshaw control system
(Photo 7), which apparently uses loop supply and return temperatures and outside air for control, setback,
and also to switch to cooling. Staff also indicated that night setback of room temperature also occurs, but
it is not clear how this is implemented. The control scheme was not investigated in detail, but appears
documented and functional. Staff indicates that the chiller only used approximately 30 days per year
maximum, since there are few hot days that correspond to school being in session.
According to staff, the boiler was rehabilitated in 2006, but is now somewhat problematic – repair costs
are increasing as it reaches the end of its life; similarly, the water loop pumps were recently rebuilt (Photo
8), but are also having some problems. The condition of the chiller system is unknown, as are the internal
water piping conditions and water treatment regimen; these system elements will require investigation
prior to any substantive improvements. In general, however, the water distribution, air handling and
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pneumatic controls appeared to be well maintained and functional. There were no signs of major water or
air leaks, equipment was clean and operative, as is visible in the pictures below. As part of any upgrade, it
is also recommended that air and water systems be tested and balanced and at least a general operative
commissioning be performed on the system as a whole, once any new major heating or cooling system
elements are installed.
The Gym/Vo-Ed building is heated using hot water supplied by a 1,700,000 Btu/hr. (1700MBH) Burnham
fuel-oil hot water boiler (see Photo 10). This was installed as a part of an Energy Service Performance
Contract (ESPC) that replaced a steam heating system there in 2010. That ESPC also installed all new hot
water piping and air heating units (principally fan coils) in the Gym/Vo-Ed building. The boiler is controlled
by simple thermostatic DDC controls, including night and outside air temperature setbacks, while the
terminal units are independently thermostatically controlled. Some integration of terminal and boiler
controls was implied in discussions with maintenance staff, however the specifics (system sequence of
control) are unknown at this time. The boiler modulates as needed to provide hot water supplied at an
estimated 180 deg. F maximum. Hot water circulation is provided by a constant-speed 85 GPM, 90 ft.
head pump with a backup pump. The flow control is via a mixing valve, assumed controlled by return
temperature. All this equipment is in excellent operating condition.
Site HVAC Equipment Photos Photo 5: Weil McLain 704 MBTU hot water boiler
Photo 6: Representative classroom air handler
Photo 7: Robertshaw pneumatic heating/cooling controls
Photo 8: Heating/cooling water circulation pumps
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Photo 9: Common area air handler (attic space)
Photo 10 – New hot water boiler in Gym/Multipurpose/VO-Ed
Building
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Of importance to this report, each of the 4 main buildings in the closely spaced campus is heated
separately. As discussed above, the elementary school and the Gym/Multipurpose/VO-Ed building are
heated with oil-fueled boilers feeding hot water / air handler systems. The high school and repurposed
performing arts building are heated electrically by air-source heat pumps, indicated by staff to be a
retrofit of 2004 vintage. Anecdotally, there are occasional water leakage issues around these units. We
could not access these units; see Photo 11. An Informal conversation occurred as to whether a larger
wood heat system could serve this building as well as the elementary school. It is certainly proximal
enough, and this possibility is worth investigation, but should not hold up the elementary school
project, as funds for this are limited in both time and amount.
Photo 11 – Rooftop heat pumps on Northport high school
Energy Requirements and Costs
Annual totals for energy use in this feasibility analysis are based on oil purchase records for three
“school years” (previously shown in Table 3.), and electric utility billing records for 24 months.
Typically, an energy analysis would merge these data in order to assess overall energy use in a facility
being studied. In the case of Northport schools, two conditions made this impossible:
1. Oil purchases are irregular, because oil is stored at the facility in a 6000-gallon tank. This
means that oil use can only be studied in aggregate, and that oil heating energy use rates must
be estimated, based on timing of oil purchases and outside air conditions. This was done in the
modeling for boiler size, as detailed in Table 5.
2. All major electric loads at Northport Schools are served by one Avista Electric account and
meter set (account 3586100000 / meter 00031336). This makes it impossible to determine
what electric use is attributed to the elementary school, versus other buildings.
Although major electrical loads being on one main electric meter precluded a complete billing analysis
of the elementary school, electric billing analysis did suggest opportunities for energy savings. In
particular, a high correlation between electricity use and demand vs. temperature suggests that
electrically heated buildings are major consumers at Northport, which is not surprising, given that two
buildings in this cold climate are heated with older air-source heat pumps. Our analysis of electric use
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does point out substantial impacts from the electric heating loads at the high school and the old
performing arts building, as will be shown. These systems appear fairly expensive to operate, and
might be considered for alternative heating methods, including possibly expanding the wood heating
project to provide heat to these buildings. This option has not been technically or financially modeled
at this time, however. An attempt was made to disaggregate the electric bills to assess what portion of
them may be heating, with limited success. The two oil-heating systems (in the elementary school and
the multipurpose building) also use significant electricity for pumping and fans, confounding this
analysis. Electrical sub-metering or a combination of specifications on the units and some modeling of
the building could provide more accurate disaggregation of loads, revealing both the electrical use by
the heat pumps and by the oil heating heat distribution systems.
Therefore, the energy profiles and electric billing analysis presented below, while important, is not
central to the consideration of the boiler replacement at Northport Elementary School.
Table 10. Energy profile summary
Average Annual Electric Consumption (kWh) 454,560
Average Hourly Electric Demand (kW) 52
Maximum Electric Demand (kW-hr) 194
Minimum Electric Demand (kW-hr) 55
Elementary School Annual Fuel Consumption (MMBtu) 1372
Elementary School Average Heating Season Hourly Thermal Demand (MMBtu/hr.)
0.36
Minimum Hourly Thermal Demand (MMBtu/hr.) 0.0
Electrical Energy, Power Demand and Typical End Uses
Avista Electric Company provides electricity to the Northport school facilities. Figure 3 illustrates
the school’s 2-year average monthly electric energy use and demand.
It is also worth noting the high correlation between electrical energy and demand and low
temperatures, shown in Figure 4 and Figure 5. What this shows is that both electrical energy
and peak power increase steeply and roughly linearly as temperature drops. This sort of
analysis also helps to identify the so-called “base-load” (approximately 25,000 kWh. - $2,800
per month) that the school has when not using HVAC systems significantly. Major electrical
energy end-uses within the school are HVAC, lighting, and kitchen appliances and systems. A
typical breakdown of typical electric energy use in a K-12 school is shown in Figure 6.
Northport School District’s “melded” electrical cost during the study was: $0.105/kWh. This melded
cost is a composite of the cost of electrical energy and metered demand charges for the total
amount of energy consumed in a single month. The melded cost is a useful cost factor that can be
used to quickly apply to permanent incremental electrical use increases or decreases to estimate
electrical cost impacts.
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Figure 3. Average monthly electric consumption and peak demand
Figure 4. Electrical energy use as a function of temperature
Figure 5. Electrical peak power demand as a function of temperature
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Figure 6. Typical K-12 energy uses by area*
* This energy use profile is based on typical energy use in a public school. Source: U.S. Department of Energy
Thermal Energy Use at Northport Elementary School Thermal demands at in the elementary school and Gym/Vo-Ed buildings are met with diesel fuel for space heating. Estimated Monthly fuel oil consumption is shown in Figure 7. Thermal systems modeling and load estimation is discussed in detail in the Proposed Wood Pellet Boiler System section above.
Figure 7. Northport Elementary School estimated monthly #2 fuel oil consumption – 2013-2016
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Suggested Wood Pellet Boiler Specification The following specification is offered as an example of likely specifications needed in the
development of a bid specification, should Northport wish to proceed to develop a bid.
The specifications below are not intended as requirements, but suggestions. The WSU
Energy Program will assist and coordinate assistance from OSPI and others to develop
an actual appropriate boiler replacement bidding process to ensure the district receives
what it needs.
1. General Requirements
Components 1.1 General
1. Commercial service wood pellet boiler system. ASME rated.
2. The packaged system shall include an integrated wood pellet burner and firetube heat exchanger, and automatic control of fan speeds based on firebox temperature or residual oxygen to achieve optimum combustion.
3. Accessories should include all ASME pressure relief valves, an automated system to remove ash from the heat exchanger tubes, and a system to extract ash from the combustion chamber into a sealed storage. The control system shall control the complete combustion, operation, and all functions of the wood pellet boiler system.
4. Components for the piping interconnection / integration of the two school buildings with the existing boiler and the new boiler shall be as specified in owner accepted engineering documentation.
1.2 Submittals 1. Product Data: Manufacturer's data sheets on each product to be used, including:
a. Preparation instructions and recommendations
b. Storage and handling requirements and recommendations
c. Installation method
d. Shop drawings: system schematics and detailed drawings of components and devices
e. Performance data
f. Maintenance manual
1.3 Quality Assurance 1. Manufacturer Qualifications: Manufacturer shall engineer, fabricate, and install system
components appropriate for a complete Commercial-service integrated heating system.
2. ASME Compliance: Fabricate and label boilers to comply with ASME Boiler and Pressure Vessel Code Section IV.
1.4 Delivery, Storage, and Handling 1. Store products in manufacturer's unopened packaging until ready for installation.
2. The contractor shall be responsible for paying the permit fee associated with the wood boiler system installation.
1.5 Warranty 1. Manufacturer's Standard Warranty for Commercial Boilers: Two-year warranty against defects
in material and workmanship on the pressure vessel.
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2. Manufacturer's Standard Warranty for Electrical: One year from the date of installation.
Commercial Boilers and Accessories A. Commercial Boilers
1. Biomass boiler with integrated burner and separate primary and secondary air nozzles with automatic control of fan speeds in order to achieve optimum combustion.
2. EPA certified to meet the 2015 New Source Performance Standard (NSPS) for New Residential Wood Heaters, New Residential Hydronic Heaters and Forced-Air Furnaces at 40 CFR Part 60 (Subpart QQQQ) and are deemed to be EPA-certified until May 15, 2020.
3. Automatic ignition based on an electric heating element
4. Ash extraction: Complete ash extraction from boiler burner and heat exchangers to closed ash container.
5. Automatic heat exchanger cleaning.
6. Flue gas fan: Induced draft fan to maintain a negative pressure in boiler.
7. Fire back burn protection system.
8. PLC-based automatic control system.
9. Boiler breeching and connecting flue gas pipe and cleanouts
10. Pneumatic fuel conveying equipment capable of conveying fuel from fuel storage silo to combustion chamber.
B. Performance 1. EPA Certified to 2015 New Source Performance Standard.
2. Achieves 85% HHV efficiency using digital modulating output control.
C. Construction 1. Separate nozzles for primary and secondary combustion air.
2. Burner elements made from stainless steel.
3. Automatic ash extraction and automatic heat exchanger cleaning.
D. Fire (Back Burn) Protection 1. Provide three back-burn fire safety devices:
a. Water deluge valve – mechanical, located in intermediate hopper. b. Positive fuel shut off – mechanical, located between upper feed auger and stoker auger. c. Hose connection – mechanical, connection between bulk silo and intermediate hopper
is made out of a burnable material to eliminate fire to bulk silo.
E. Component Design 1. Fuel Handling System: Supplies solid fuel for boilers.
2. Fuel transport for storage bin to day bin shall be by pneumatic transport and shall include static discharge grounded supply and return air hoses.
3. Fuel Storage Bin: Stores wood pellets (or wood chips).
4. Volume: minimum fuel storage for 60 days of operation at 80% of full load.
5. Venting with filter.
6. Explosion Safety Device.
7. Access points for inspection.
8. Level sensor for low-level, integrated and monitored by PLC control.
9. Low-level alarm set at the amount of fuel required for five days of operation at 80% load.
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H. Boiler Controls 1. The boiler system shall be controlled and supervised by biomass boiler controls.
2. The integral biomass boiler control shall control the combustion system.
3. Combustion control: with O2 lambda sensor or combustion temperature probe, individual primary and secondary air nozzles, fuel feeding, ash handling, heat exchanger cleaning, flue gas fan, variable load regulating 30-100%, source selector, flue gas temperature, self-adjusting combustion control.
4. Hydronic control: Water temperature, distribution pump, boiler pump, Btu meter, safety devices, zone valves.
5. Level sensor in fuel storage, alarm handling, GSM-alarm with status.
6. Control panel is equipped with circuit breakers for motors.
I. Automatic Ash Removal System 1. System shall incorporate an automatic ash removal system.
J. Pellets (or wood chips) 1. Only premium wood pellets certified by the Pellet Fuels Institute may be used and
shall follow these guidelines:
1. Bulk density per cubic foot shall be a minimum of 40 pounds.
2. The diameter shall be between 1/4 inch and 5/16 inch (6 mm to 8 mm).
3. Maximum length shall be 1.5 inches (38 mm).
4. Fines (dust) of not more than 0.5% by weight.
5. Sodium content shall be less than 300 parts per million.
6. Ash content of 1% or less.
7. Moisture content of 10% or less.
K. Interconnection / Integration Piping System Electrical and Controls Systems
1. Controls and electrical systems for the piping interconnection/integration of the two school buildings with the existing boiler and the new boiler shall be as specified in owner accepted engineering documentation.
L. Hot Water Storage Tank 1. At least 1.5 gallons storage per 1,000 Btu boiler capacity or 200 gal., whichever is
greater. 2. The heating hot water storage tank shall be rated ASME-H
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Heating Alternatives to Wood Pellets Two other heating alternative options for Northport Elementary School were considered as part of
standard due diligence and for comparative reference, but are not recommended at this time: A new
oil boiler, and a mill wood waste- fueled boiler.
Base Case: Replace existing boiler with new oil boiler
The “Base Case” or “Business as Usual” option to replace the current fuel oil-fired heating system is a
simple “replace-on failure” strategy, installing a new oil boiler in its place. Absent any other changes,
this option, when combined with tuning the existing system and upgrading controls could be expected
to improve efficiency by up to 15%, lowering oil costs accordingly. Given an average cost for oil of
$24,052 over the past two years, a 15% improvement would save approximately $3600 per year. Oil
boiler replacement and system upgrades were not specifically quoted, but based on Means estimates,
the boiler replacement avoided cost used in the pellet fuel case is estimated at $30,000, installed.
Another $25,000 is estimated for repairs to the hydronic systems and controls upgrades, again similar
to the estimate used in the pellet boiler case. The total installed cost is thus roughly $55,000. At
present fuel oil costs this results in a simple payback period of roughly 15 years, based on energy
savings.
Use mill residue (wood chips) as fuel for the system It is possible that a much larger boiler using mill waste could supply 100% of the Elementary, High School
and the Gym/Multipurpose/VO-Ed building, tying all heating systems together and using the new boiler at
the VO-Ed building as a trim boiler. Fuel for such a boiler appears to be plentiful in areas around Northport,
and could result in attractive economics on that basis.
Capital costs would be far greater for this option, such that the $250,000 grant would likely only cover a
relatively small portion. Based on discussions with district staff, it was assumed the District would not likely
wish to build such a large system, so economics of this option were not explored. If the district wishes to
study this option further, WSU will attempt to support such research. However discussions should be held
with the State Department of Commerce to ensure the grant opportunity is not lost and to inquire about
other possible funding for a larger project, which is uncertain.
A system of this type was installed at the the Quillayute Valley School District in Forks, WA. Planning
calculations estimated that the system would provide an annual cost savings of approximately $120,500,
resulting in a simple investment payback period of 3.4 years. Actual savings in the first three years were
$50,000 - $60,000 per year; the actual payback is thus about 7 years – still quite attractive, assuming
these conditions have persisted. The overall project (including building and HVAC upgrades) was funded
with a $1 million state grant and $1.6 million school district bond.
Other operational factors need to be considered when implementing a wood chip-fueled system,
including the need for a larger fuel storage footprint for chips vs. pellets (a covered or enclosed building
to protect wood chips from exposure to the weather), and greater staffing requirements, possibly
including 24/7 on-call staff to respond to operational system needs that are unique to wood chip use.
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Conclusions The WSU Energy Program appreciates the opportunity to work with Northport School District staff
during the development of this feasibility study. Conclusions are summarized as follows:
This project has technical and financial viability. Proceeding with construction documents and
installing a new wood pellet boiler is recommended.
The Northport School District should consider installing one 350 MBTU wood pellet boiler
system with sufficient heat storage and trim boiler capacity, as described in this report.
In addition, the district should consider interconnecting and integrating the hydronic heating
systems in the elementary school with those in the Gym/Vo-Ed building, supplying trim
heating water supply for the pellet boiler, as well as full backup heating water capacity for
both buildings from the existing 1700 MBH Burnham hot water boiler installed in the
Gym/Vo-Ed building in 2010.
If the district decides to proceed, WSU will work with the offices and departments above to
develop an effective bid process. This is currently underway.
If the district decides to proceed, WSU will release funds of up to $40,000, as required for
final engineering design, specifications and bid documents, in addition to the $250,000 in
capital equipment grant funds. Based on initial approval by the Northport School Board,
Approximately $5000 of engineering feasibility studies for Northport have already been
contracted (5/24/17). Among other findings, that contract resulted in the findings and revised
recommendations and conclusions provided in this Revision 1 report.
Based on continuing interest by Northport SD in developing this project, as expressed in
email and telephone communications with Don Baribault of Northport, detailed engineering
designs of the hydronic heating systems interconnection/integration of the elementary school
and Gym/Vo-Ed building were contracted and a detailed design is available for reference.
If the district decides to proceed, WSU will work with the district to secure a fuel supply
contract as condition of proceeding.
If the district decides to proceed, WSU will work with the district, the Washington Office of
Superintendent of Public Instruction Facilities Department and the Washington Department
of Commerce in good faith to attempt to secure such funds as are needed to complete the
project.
