HomeMy WebLinkAboutAtch 1 - 2012 feasibility study
Renewable Energy Feasibility Analysis
Wastewater Treatment Plant
City and Borough of Sitka
Prepared by:
Final Report
July 2012
Alaska Energy Engineering LLC
Blank Page
Alaska Energy Engineering LLC
Wastewater Treatment Plant Renewable Energy Feasibility Analysis 1
Table of Contents
Section 1: Executive Summary 3
Introduction ........................................................................... 3
Heat Pump Technology ......................................................... 3
Life Cycle Cost Analysis ....................................................... 3
Section 2: Introduction 5
Introduction ........................................................................... 5
Heat Pump Benefits ............................................................... 5
Heat Pump Options ............................................................... 7
Section 3: Life Cycle Cost Methodology 9
Economic Factors .................................................................. 9
Operating Costs ..................................................................... 9
Energy Costs ....................................................................... 10
Section 4: Life Cycle Cost Analysis 13
Heating System Options ...................................................... 13
Life Cycle Cost Analysis ..................................................... 14
Appendix A: Schematic Diagrams
Appendix B: Sizing and Life Cycle Cost Calculations
Alaska Energy Engineering LLC
Wastewater Treatment Plant Renewable Energy Feasibility Analysis 2
Blank page
Alaska Energy Engineering LLC
Wastewater Treatment Plant Renewable Energy Feasibility Analysis 3
Section 1
Executive Summary
INTRODUCTION
This report presents the findings of a Renewable Energy Feasibility Analysis for the Wastewater
Treatment Plant (WWTP) in Sitka, Alaska. The intent of this analysis is to determine if there is
economic incentive to invest in heat pump technologies to heat the building.
The heating and ventilating systems at the WWTP have reached the end of their service lives and
replacement is planned. This feasibility analysis evaluates whether the building should be converted
to renewable energy heat pumps as part of the replacement project.
HEAT PUMP TECHNOLOGY
Heat pumps are desirable systems for buildings in Sitka. The technology is mature and has been
adapted to heating dominated operating modes and cold climates. Benefits include:
High conversion efficiency
Extracts heat from the environment, significantly reducing the amount of purchased energy and
the cost of long-term energy inflation
Powered by renewable hydroelectric power
Reduction in greenhouse gas emissions
The following heat pump technologies were considered for the plant: ground source, seawater
source, air source, and effluent source. The effluent source heat pump is preferred because it can be
readily coupled to the plant recycled effluent which is a warmer heat source than the other options,
providing superior conversion efficiency.
The availability of hydroelectric power is central to the economics of a heat pump system. Sitka is
experiencing load growth due to electric heating, which has resulted in diesel supplementation of the
hydroelectric generation. It is likely that diesel supplementation will occur during the life of a heat
pump system. The analysis takes this into account by using a proposed 9% per year rate increase for
the first two years and 2.5% electric inflation in the remaining years. This rate of electric inflation
greatly exceeds historic inflation that has been around 1% per year.
LIFE CYCLE COST ANALYSIS
The analysis compares the life cycle cost of the baseline system with an effluent heat pump system.
The proposed replacement of the heating and ventilating systems provides an excellent opportunity to
convert the building to heat pump technologies. A heat pump system cannot be retrofitted into the
building unless the heating coils in the ventilation systems are also replaced. This is because the
existing coils have a capacity based on 180°F boiler water; a heat pump can supply only 115°F
heating water which will reduce the capacity of the coils. The analysis is based on the assumption that
the ventilation systems will be replaced in conjunction with the heat pump installation so the systems
can be designed for 115°F heating supply water from the heat pump.
Alaska Energy Engineering LLC
Wastewater Treatment Plant Renewable Energy Feasibility Analysis 4
Life Cycle Cost Comparison
Heating System Construction Maintenance Energy Total LCC
Baseline Fuel Oil Boilers $201,000 $147,000 $2,141,000 $2,489,000
Effluent Heat Pump System $810,000 $248,000 $451,000 $1,509,000
The economic comparison of the systems shows that the effluent heat pump has a much lower life
cycle cost than the baseline system. The system produces significant energy savings which more than
offsets its higher construction and maintenance costs.
Summary
For investment in a heat pump system to be preferred over the relatively lower construction cost of
the traditional fuel oil boiler system—likely siphoning dollars from other priorities—the system
should overwhelmingly have a lower life cycle cost. This is the case with the effluent heat pump
system. This result occurs because the plant effluent can be easily tapped as an energy source using
existing pipelines and pumps. The proposed upgrade of the heating and ventilating systems also
reduces the cost of converting to a low-temperature heating system.
Alaska Energy Engineering LLC
Wastewater Treatment Plant Renewable Energy Feasibility Analysis 5
Section 2
Introduction
INTRODUCTION
This report presents the findings of a Renewable Energy Feasibility Analysis for the Sitka
Wastewater Treatment Plant (WWTP) in Sitka, Alaska. The intent of this analysis is to determine if
there is economic incentive to invest in heat pump technologies to heat the building. The analysis is
performed by Jim Rehfeldt, P.E. of Alaska Energy Engineering LLC.
This study compares the life cycle cost of upgrading the existing fuel oil boiler heating system or
converting the buildings to heat pump heating. The options are evaluated using life cycle cost
analysis, which compares construction, maintenance, and energy costs of the heating options over a
30-year period.
The findings are highly sensitive to the economic factors and energy costs used for the analysis.
Future energy inflation can significantly affect the findings, yet there is no one authority for these
values. For this reason, a sensitivity analysis will be used where base case, low case, and high case
values for electricity and fuel oil inflation are evaluated.
Wastewater Treatment Plant
The WWTP is currently heated by two fuel oil boilers and a hydronic heating system that supplies air
handling unit heating coils, unit heaters, and baseboard convectors. Air handling units provide
ventilation, air heating, and natural cooling to the plant and office areas.
The existing HVAC systems have reached the end of their service lives and will be replaced in the
near future. This offers an opportunity to integrate heat pumps into the building. The coils in the
upgraded systems can be sized for 115°F heat pump water, easing integration of the heat pump with
the building systems.
The primary opportunity for a heat pump is to couple to the plant effluent. The water is much warmer
than ground, air, and ocean sources and the quantity is sufficient to heat the building. This feasibility
analysis evaluates whether the building should be converted to renewable energy heat pumps when
the HVAC systems are upgraded.
HEAT PUMP BENEFITS
Community Benefits
Heat pumps are desirable systems for residential and commercial buildings in Sitka. The technology
is mature and has been adapted to heating dominated operating modes and cold climates. Some of the
primary benefits include:
High conversion efficiency
Extracts heat from the environment, significantly reducing the amount of purchased energy and
the cost of long-term energy inflation
Powered by renewable hydroelectric power
Reduction in greenhouse gas emissions
Alaska Energy Engineering LLC
Wastewater Treatment Plant Renewable Energy Feasibility Analysis 6
Heat pump heating efficiency typically ranges from 220-400%, depending upon the type of heat
pump and the temperature of the heat source. An effluent coupled heat pump will have a 400%
seasonal efficiency which will consume one unit of energy to extract three units of heat from the
environment and supply four units to the building. In comparison, fuel oil and electric boiler plants
have nominal seasonal efficiencies of 70% and 95%, respectively.
Heat pumps are powered by electricity, which is predominately hydroelectric generated in Sitka. As
such, they reduce greenhouse gas emissions when compared to fuel oil heated buildings. The same
can be said for electric resistance heat, but there is an essential difference between the two. Heat
pumps make efficient use of available hydroelectric resources, which meshes well with community
sustainability goals to make efficient use of renewable energy. Electric resistance heat has a much
lower efficiency, which has led to high load growth and depletion of the hydroelectric supply.
Cost of Heat Comparison
The following chart provides a 30-year heating cost comparison for fuel oil and electric heating
options. The widening gap between the cost of fuel oil heat and the other sources is the primary driver
for conversion to renewable energy sources. The conversion efficiency of heat pumps offers the
greatest protection from future energy inflation.
By transferring heat from the environment to the building, a heat pump requires less purchased
energy to meet the load, and most importantly, significantly reduces the long-term effect of energy
inflation.
$0
$50
$100
$150
$200
$250
$300
2013 2015 2017 2019 2021 2023 2025 2027 2029 2031 2033 2035 2037 2039 2041$ / MMBtuYear
Cost of Heat Comparison
Fuel Oil Boiler Heat @ 6.6% Inflation
Electric Boiler Heat @ 9% (Years 1‐2) and 2.5% (Years 3‐30) Inflation
Effluent Heat Pump @ 9% (Years 1‐2) and 2.5% (Years 3‐30) Inflation
Alaska Energy Engineering LLC
Wastewater Treatment Plant Renewable Energy Feasibility Analysis 7
HEAT PUMP OPTIONS
Potential heat pump technologies for heating and cooling the buildings include air-source, which
extract heat from outside air, and water-source, which extract heat from the plant effluent, ground or
an adjacent body of water such as the ocean. Both air-source and water-source heat pumps can
produce hydronic heating water (water-side) or supply heat via ventilation air (air-side). They can
also provide cooling, which is typically a small portion of overall energy consumption.
The existing hydronic heating system operates on 180°F boiler water. A heat pump retrofit will
supply a maximum of 115°F heating water, which detrimentally reduces the heat output of the
existing heating units. If a heat pump system is retrofitted into the building, the existing heating units
must be increased in size or additional heating capacity installed.
The current plan to upgrade the HVAC systems will make the heat pump conversion much easier.
The heating units for the upgraded systems can be sized for 115°F heating water by increasing their
heat transfer area; only the incremental cost of larger heating units are included in this analysis.
Options
The following heat pump options were considered for the study:
Plant Effluent Heat Pump System
The system couples a water-to-water heat pump to the plant effluent. The effluent flows through a
heat exchanger, which transfers the heat to the heat pump evaporator. The effluent is warmer than
other heat sources and has sufficient heat capacity to meet the building heating load year-round.
Ground Source Heat Pumps
This system utilizes a loopfield to extract heat from the ground. The heat pump “lifts” the heat to a
higher temperature for heating the building.
Seawater Heat Pumps
This system utilizes seawater as a heating source for the building. It is warmer than the ground during
the winter, which improves heat pump efficiency. The seawater can be extracted from the sea via an
intake or drawn from water wells located near the building.
Air Source Heat Pumps
Air source heat pumps extract heat from the ambient air to heat the building. Technology
improvements have made them effective at heating in cold climates and capable of varying their
output with the heating or cooling load.
Cold climate air source heat pumps are not in wide use and there is no historic operating data to
assess their real-time performance in Sitka’s temperate marine environment. They were recently
installed in Blatchley Middle School, which offers the opportunity to gain valuable performance data
for Sitka’s maritime climate. It is prudent to understand the following concerns when considering air-
source heat pump technologies:
The outdoor unit extracts heat by cooling outside air. This can cause moisture in the air to
condense and freeze on the coil surface. When the frost builds up and restricts air flow, the unit
initiates a defrost cycle that sends heat to the outdoor coil to melt any frost accumulation.
Optimization of defrost operation is essential to maximize equipment efficiency while operating
in our unique maritime climate. While air-source heat pumps are successfully heating buildings in
coastal Alaska, there is incentive to reduce defrosting operation through control strategy
optimization.
Alaska Energy Engineering LLC
Wastewater Treatment Plant Renewable Energy Feasibility Analysis 8
The technology has evolved so that air source heat pumps can efficiently heat, even during cold
weather, but we do not have long-term data on the long-term maintenance requirements imposed
by our climate or the actual service life of outdoor units that are harshly exposed to maritime salt-
laden air.
The capability to maintain heat pump systems, both in-house and through local refrigeration
contractors, must be developed. This is true of all heat pumps, but more important for air source
heat pumps that are outdoors and more affected by climate. As the use of these systems
increases—a likely occurrence if current installations are successful—the capability to maintain
them will be developed within our communities.
To minimize exposure to salt-laden air, rain and blowing snow, the optimum location for the outdoor
unit is within a louvered room which protects the equipment from the elements and mitigates noise. A
successful arrangement is for the heat pump to draw air in through louvers and then discharged
through an exhaust duct to the outdoors.
Summary
The wastewater effluent is a superior heat source over the other options. It has the lowest installation
cost because the plant recycled effluent line runs right to the boiler room. In addition, the effluent is at
a higher average temperature, which results in a higher efficiency than the ground or seawater
coupled systems.
The air source heat pump system is another option. However, it will require 6 outdoor units and 12
indoor hydronic heat exchangers to supply the required heating load. The high cost of installing and
operating the system makes it unlikely to compare favorably with the effluent heat pump system.
For these reasons, the analysis investigates coupling a water-to-water heat pump to the recycled
effluent to heat the building.
Alaska Energy Engineering LLC
Wastewater Treatment Plant Renewable Energy Feasibility Analysis 9
Section 3
Life Cycle Cost Methodology
The purpose of the feasibility analysis is to compare the life cycle cost of a renewable energy heating
system for the building. The findings are highly sensitive to the economic factors, energy costs, and
energy inflation used for the analysis. While future energy inflation often has the greatest impact,
there is no authority for these values. For this reason, a sensitivity analysis is used where base case,
low, and high values for electricity and fuel oil inflation are evaluated.
ECONOMIC FACTORS
The following economic factors are used in the analysis:
Economic Period: The economic period is set at 30 years with all costs based on 2013
construction.
Nominal Interest Rate: This is the nominal rate of return on an investment, without regard to
inflation. The CBS estimates that the bond rate will be between 4 and 7%. The analysis uses a
rate of return of 5.5%.
Inflation Rate: The Consumer Price Index has risen at a rate of 2.9% over the past 20-years. The
State of Alaska predicts general inflation of 2.5-3% per year. The analysis is based on a 2.9% rate
of inflation over the 30-year economic period.
OPERATING COSTS
Operating costs include maintenance and repair cost—on an annual and intermittent basis—and
equipment replacement costs at the end of its expected service life. The costs are derived from
industry standards for the long-term operation of the systems.
Maintenance and Repair
The heating systems will have the following maintenance and repair requirements. Heat pumps have
higher maintenance requirements than the existing systems. It is assumed that maintenance will be
performed by CBS facilities staff except where noted.
Fuel Oil Boilers: Requires daily inspections, monthly service, and annual cleaning of the firebox
and a combustion test.
Water-to-Water Heat Pump: Requires daily inspections, monthly service, 3-month service, and
annual cleaning of the heat transfer surfaces. In addition, a factory tune up is required every five
years. It is assumed that the 3-month service, annual maintenance and factory tune-ups will be
contracted out.
Pumps: Require annual lubrication and periodic replacement.
Effluent Heat Exchanger: Requires biannual cleaning.
Alaska Energy Engineering LLC
Wastewater Treatment Plant Renewable Energy Feasibility Analysis 10
Replacement
The following heating and cooling equipment will require replacement at the end of its expected
service life:
Water-to-Water Heat Pump: Expected service life of 18 years.
ENERGY COSTS
Fuel Oil
Current Cost
The CBS currently pays $3.76 per gallon for #2 heating oil.
Future Inflation
Base Fuel Oil Case: In recent years, fuel oil inflation has been very sporadic, with a decidedly
upward trend in prices. Looking at oil prices over a longer period will smooth out the data and
provides a longer-term assessment of future costs. Using this perspective over the past 25-years, fuel
oil inflation has averaged 6.6% per year. The base case assumes that future fuel inflation will
continue at this rate.
High Fuel Oil Case: There is potential for world oil demand to increase due to increased
consumption by developing countries and/or an expanding global economy. Disruption of the world
oil supplies could also affect supply, causing prices to rise. The high case assumes these factors and
others could cause fuel inflation to be higher than the base case at 8% per year.
Low Fuel Oil Case: The U.S. Energy Information Agency predicts fuel oil inflation of 4.8% per year
for the next 25-years. While this reference has historically under-predicted actual fuel oil inflation, it
is possible that future fuel oil inflation may be lower than the base case due to: new technologies that
increase oil field production; new sources such as oil sands; and efficiency gains that reduce global
oil demand. These factors and others could lead to less demand which would result in fuel oil
inflation lower than the base case at 4.8% per year.
Electricity
Current Cost
Electricity is supplied by the CBS Electric Department. Power generation facilities include Blue Lake
Hydro, Green Lake Hydro, and the Jarvis Street diesel plant.
The building is billed under the General Services Rate, which charges for both electrical consumption
(kWh) and peak electric demand (kW). Electrical consumption is the amount of energy consumed and
electric demand is the rate of consumption. Electric demand is determined by averaging demand over
a continuously sliding fifteen-minute window. The highest fifteen-minute average during the billing
period determines the peak demand. The following table lists the electric charges:
Alaska Energy Engineering LLC
Wastewater Treatment Plant Renewable Energy Feasibility Analysis 11
General Services Rate
Monthly Charge Rate
Energy Charge per kWh
First 500 kWh 14.17¢
Over 501 kWh 9.03¢
Demand Charge per kW $4.50
Future Inflation
Over recent history, Sitka’s electricity inflation has been low, lagging general inflation. However,
electric heating conversions have created load growth that has caused the utility to use more diesel
supplementation to meet the load. Diesel supplementation last winter resulted in a 1.35¢ per kWh fuel
surcharge.
To reduce diesel supplementation, the dam at Blue Lake will be raised, increasing hydroelectric
power production by 27%. The utility recently completed a rate design study that recommended
raising rates to put the utility on firm financial footing. A 9% increase for the next two years is
included in the analysis.
Base Electric Case: Even with the Blue Lake expansion and proposed rate increase, electric heating
loads are likely to continue to place demands on the hydroelectric generation facilities. Energy
balance reports for Southeast Alaska communities show that heating loads are 175% greater than the
non-heating load. While most of the heating load is currently met with fuel oil, only a small
percentage of this large potential load needs to convert to electricity to place demands on the electric
grid. In essence, future electricity prices may be tied to fuel oil inflation. The life cycle cost analysis
uses an electric inflation of 2.5% to account for the impacts of future fuel oil to electric heat
conversions.
High Electric Case: If fuel oil prices continue to rise, load growth due to electric heating loads will
increase. This scenario will result in greater diesel supplementation in the short-term and possible
construction of additional hydroelectric generation as a long-term measure. Higher electric rates will
result. The high case assumes these factors will result in an average electric inflation rate of 4%.
Low Electric Case: The low case assumes that load growth does not deplete the hydroelectric
surplus; electric rates continue at the historic inflation rate of 1%.
Alaska Energy Engineering LLC
Wastewater Treatment Plant Renewable Energy Feasibility Analysis 12
Summary
The following table summarizes the energy and economic factors used in the analysis. A sensitivity
analysis is also provided to determine how modest variations in energy inflation affect the results.
The following table shows the base, high and low case energy inflation that is applied to the analysis.
Summary of Economic and Energy Factors
Factor Rate or Cost
Nominal Discount Rate 5.5%
General Inflation Rate 2.9%
Electricity, 2013 10.9¢ per kWh
Electricity Inflation 1 1%, 2.5% (base), 4%
Fuel Oil $3.76 / gallon
Fuel Oil Inflation 1 4.8%, 6.6% (Base), 8%
1. The inflation rates for electricity and fuel oil represent the base case and
the low and high cases used for the sensitivity analysis.
Alaska Energy Engineering LLC
Wastewater Treatment Plant Renewable Energy Feasibility Analysis 13
Section 4
Life Cycle Cost Analysis
The proposed upgrade of the HVAC systems provides an excellent opportunity to convert the
building to heat pump technologies. Incorporating heat pumps will require added investment in the
heat pumps and the couple to the environment, but the heating and ventilating systems can be readily
designed for heat pump technologies with minimal added cost of construction.
HEATING SYSTEM OPTIONS
Baseline Heating System
The baseline system replaces the existing heating plant in-kind. The upgraded plant will consist of
two fuel oil boilers, primary loop with pumps, piping, and appurtenances, and secondary loop with
building pumps, piping, and appurtenances.
Effluent Heat Pump System
The wastewater plant has a recycled effluent system that is used for equipment spray down and
cleaning. The distribution piping is full size outside the boiler room and a reduced size line runs
through the boiler room. Connection to the line will be outside the boiler room where the pipe is full
size.
Recycled effluent flow occurs by manually starting the recycled effluent pump and opening a valve at
one of the hose stations in the plant. The recycled effluent system must be modified to be used as a
heat source. The recycled effluent pump will require a new motor, variable frequency drive and
controls so the pump operates automatically at optimum speed whenever the heat pump operates. The
controls must also disable the heat pump whenever the recycled effluent is needed for cleaning (the
system is used for short durations a few times each week).
The recycled effluent will flow through the warm side of a stainless steel heat exchanger. An
evaporator pump will circulate antifreeze through the cold side where it will gain heat for the heat
pump. The heat pump will “lift” the heat to 115°F for distribution to the building. The heated water
will be stored in a buffer tank. A fuel oil boiler will be utilized to provide redundancy and
supplemental heat during cold weather. The heat pump and boiler are sized for 70% of the design
load which provides redundancy without oversizing the system. If either heating units fails, the other
will be able to heat the building.
At this sizing, the heat pump will require 220 gpm of flow through the evaporator. The recycled
effluent pump peak capacity of 200 gpm will be needed to supply sufficient heat at peak loads. A
VFD will be installed to modulate the pump to vary the recycled effluent flow with heat pump output.
The heat pump will be located in a separate room that will be positively pressurized to separate the
equipment from the corrosive nature of the facility air.
Since the heat pump output of 115°F is much lower than a design boiler supply temperature of 180°F,
the ventilation system heating coils, unit heaters, cabinet unit heaters, and baseboard heaters must be
replaced with higher capacity units.
Alaska Energy Engineering LLC
Wastewater Treatment Plant Renewable Energy Feasibility Analysis 14
LIFE CYCLE COST ANALYSIS
The analysis compares the life cycle cost of the baseline HVAC system with an effluent source heat
pump system. A conceptual diagram of the heat pump system is provided in Appendix A. Sizing and
life cycle cost calculations are provided in Appendix B.
Construction Costs
The following table compares the cost of the systems.
Construction Costs
Construction Scope Cost Estimate Budget Increase
Baseline Heating System $ 200,000 -
Effluent Heat Pump System $ 810,000 $ 610,000
Assumptions
Baseline Heating System: The fuel oil boilers have exceeded their service life and require
replacement.
Effluent Heat Pump System: It is assumed that a recycled effluent flow of 200 gpm will be
continuously available for the heat pump. Peak and average flow data suggests that this is likely. The
heat pump will be located in the space adjacent to the boiler room with the remaining heating
equipment within the boiler room.
Electrical Service: The electric service has sufficient spare capacity to supply the heat pump system
loads. The analysis includes a cost estimate to install a separate sub-panel for the heat pump system.
Operating Costs
The following table summarizes the operating costs for each option. The basis for these costs is
provided in the Life Cycle Cost Methodology Section.
Operating Costs
System Annual Cost 1 Life Cycle Cost 2
Baseline Heating System
Maintenance and Repair $ 7,000 $ 150,000
Replacement - 0
Total $ 7,000 $ 150,000
Effluent Source Heat Pump System
Maintenance and Repair $ 8,400 $ 180,000
Replacement - 70,000
Total $ 8,400 $ 250,000
1. Annual costs include regular and intermittent maintenance and repair costs that have been averaged
over an annual basis.
2. Life cycle cost includes equipment replacement costs at the end of its service life.
3. Note: Negative values (in parenthesis) represent savings.
Alaska Energy Engineering LLC
Wastewater Treatment Plant Renewable Energy Feasibility Analysis 15
The baseline heating has the lowest operating costs because there is less equipment to maintain and
the maintenance work is accomplished in-house.
Energy Consumption and Costs
Baseline Heating System
The energy analysis is based on the fuel oil boiler supplying 100% of the heating load. Energy use of
the building is predicted to be 10% lower due to efficiency improvement associated with upgrading
the HVAC systems and controls.
The boilers will supply heat to the building, natural cooling will provide cooling, and pumps will
distribute the heat to the building.
Effluent Source Heat Pump System
The heat pump is sized for 70% of the design heating load and will supply 95% of the heat at a
seasonal efficiency of 400%. This high efficiency is due to the relatively warm temperature of the
effluent. The effluent source heat pump system benefits from a high conversion efficiency to have
lower energy costs than the baseline system. In addition, electricity is predicted to inflate at less than
half the rate of fuel oil which results in a life cycle cost savings of 75%.
Energy Consumption and Costs
Energy Costs Annual Energy Life Cycle
Consumption 2013 Cost Energy Cost
Baseline HVAC System
Fuel Oil 15,000 gals $ 60,000 $ 2,130,000
Electricity 4,000 kWh 1,000 10,000
Total $ 61,000 $ 2,140,000
Effluent Source Heat Pump System
Fuel Oil 840 gals $ 3,000 $ 120,000
Electricity 133,000 kWh 15,000 330,000
Total $ 18,000 $ 450,000
Life Cycle Cost Comparison
A life cycle cost comparison of the options shows that the effluent source heat pump system has the
lowest life cycle cost. A sensitivity analysis was applied to determine how modest variations in
energy inflation affect the findings. The following adjustments were made:
To account for increasing fuel oil price volatility, fuel oil inflation (base = 6.6%) was varied from
8% to 4.8%.
To account for a possible drop or increase in the electric load, electricity inflation (base = 2.5%)
was varied from 4% to 1%.
Alaska Energy Engineering LLC
Wastewater Treatment Plant Renewable Energy Feasibility Analysis 16
Life Cycle Cost Comparison
Heating System Construction Maintenance Energy Total LCC
Base Case: 6.6% Fuel Oil, 2.5% Electricity
Baseline Fuel Oil Boilers $200,000 $150,000 $2,140,000 $2,490,000
Effluent Heat Pump System $810,000 $250,000 $450,000 $1,510,000
High Fuel Oil Case: 8% Fuel Oil, 2.5% Electricity
Baseline Fuel Oil Boilers $200,000 $150,000 $2,660,000 $3,010,000
Effluent Heat Pump System $810,000 $250,000 $480,000 $1,540,000
Low Fuel Oil Case: 4.8% Fuel Oil, 2.5% Electricity
Baseline Fuel Oil Boilers $200,000 $150,000 $1,640,000 $1,990,000
Effluent Heat Pump System $810,000 $250,000 $420,000 $1,480,000
High Electricity Case: 6.6% Fuel Oil, 4% Electricity
Baseline Fuel Oil Boilers $200,000 $150,000 $2,140,000 $2,490,000
Effluent Heat Pump System $810,000 $250,000 $520,000 $1,570,000
Low Electricity Case: 6.6% Fuel Oil, 1% Electricity
Baseline Fuel Oil Boilers $200,000 $150,000 $2,140,000 $2,490,000
Effluent Heat Pump System $810,000 $250,000 $400,000 $1,460,000
Note: Highlighted costs are lowest life cycle cost in each case.
Energy costs are typically the largest component of the total life cycle cost of a heating system. While
this is true here, the heat pump option has a much higher installed cost, which also factors greatly into
overall life cycle cost.
For any of the options to be preferred over the relatively lower construction cost of the baseline
system—likely siphoning dollars from other priorities—the system should overwhelmingly have a
lower life cycle cost. This is true of the effluent heat pump system.
Alaska Energy Engineering LLC
Appendix A
Schematic Diagrams
Alaska Energy Engineering LLC
Appendix B
Sizing and Life Cycle Cost Calculations
Alaska Energy Engineering LLC
Blank page
Alaska Energy Engineering LLC Conceptual Sizing
25200 Amalga Harbor Road Tel/Fax: 907.789.1226
Juneau, Alaska 99801 jim@alaskaenergy.us
Wastewater Treatment Plant
BASELINE SYSTEM
Sizing Existing Boilers Boiler Net MBH
B-1 954
B-2 954
1,908
Existing Pumps GPM MBH Factor Boiler MBH
124 1,240 77% 955
Energy Consumption
Fuel, gal Total kBtu Efficiency kBTU/gal Heat, kBTU
Heat 16,700 2,312,950 68% 138.5 1,572,806
Efficiency gain 10%
Use 15,030 2,081,655 68% 138.5 1,415,525
Pumps Unit HP % Load kW Hours kWh
CP-1 3 50% 1.1 3,600 4,028
EFFLUENT SOURCE HEAT PUMP SYSTEM
Sizing Heating Plant Load, MBH Factor Size, MBH kWh Tons COP kW
Heat Pump 1,240 70% 868 - 72 3.0 85
B-1 1,240 77%955
147% 1,823
Pumps Pump GPM/ea Head whp effic bhp
Boiler 110 10 0.3 65% 0.4
R. Effluent 200 50 2.5 65% 3.9
HP Evap 217 30 1.6 65% 2.5
HP Cond 217 30 1.6 65% 2.5
Effluent Heat Exchanger Flow Inlet Outlet Spec Heat
Side gpm °F °F Btu/lb°F MBH Tons
Effluent 200 44.0 37.9 1.00 612 51
Evaporator 217 36.0 42.0 0.94 -612 -51
Electric Loads Load Qty HP hm kW
Heat Pump 1 - - 84.8
Evap Pump 1 3 91% 2.5
Cond Pump 1 3.0 91% 2.5
Total 90
Electric Service Capacity Volts Amps KVA PF kW
480 1,600 1,330 84% 1,117
Calculated Peak Load 105
Additional peak 20%
Current peak demand 126
Available capacity 991
Heat Pump System 90
Spare Capacity 902
June 26, 2012
Page 1
Alaska Energy Engineering LLC Conceptual Sizing
25200 Amalga Harbor Road Tel/Fax: 907.789.1226
Juneau, Alaska 99801 jim@alaskaenergy.us
Wastewater Treatment Plant
June 26, 2012
Energy Analysis
Ground Source Heat Pump Heat kBTU % Load HP kBTU
1,572,806 95% 1,494,166
Month % Load kBtu Source Temp COP kBtu kWh
Jan 24% 358,600 45 3.9 91,996 26,962
Feb 20% 298,833 45 3.9 76,663 22,469
Mar 16% 239,067 45 3.9 61,330 17,975
Apr------
May------
Jun------
Jul------
Aug------
Sep------
Oct------
Nov 18% 268,950 50 4.3 62,004 18,172
Dec 22%328,716 48 4.1 79,545 23,313
100% 1,494,166 371,538 108,891
402%
Fuel Oil Boiler Heat kBTU % Load Boiler kBTU Efficiency kBTU/gal Fuel, gals
1,572,806 5% 78,640 68% 138.5 835
Pumps Unit kW Hours kWh
Boiler 0.3 100 32
R. Effluent 1.7 3,600 6,260
Evaporator 2.5 3,600 8,854
Condenser 2.5 3,600 8,854
23,999
AIR SOURCE HEAT PUMP
Sizing Heating Plant Load, MBH Factor Size, MBH Tons COP kW
Heat Pump 1,240 70% 868 - 72 3.0 85
B-1 1,240 77%955
147% 1,823
MBH/ea Number Total MBH
Heat Pumps 160 6 960
HEX 80 12 960
Additional Electric Load MBH kW
868 254 Backup electric resistance heat
Page 2
Alaska Energy Engineering LLC Conceptual Sizing
25200 Amalga Harbor Road Tel/Fax: 907.789.1226
Juneau, Alaska 99801 jim@alaskaenergy.us
Wastewater Treatment Plant
June 26, 2012
Energy Analysis
Consumption kBtu
Baseline Heating Load 1,572,806
System Efficiency Gain 10%
Net Load 1,415,525
Month % Load kBtu Backup %Backup, kBtu Ave Temp COP kBtu kWh
Jan 14% 198,174 5% 9,909 33 1.9 100,983 32,501
Feb 11% 155,708 5% 7,785 35 2.0 75,758 24,485
Mar 9% 127,397 5% 6,370 37 2.1 58,861 19,118
Apr 8% 113,242 5% 5,662 40 2.2 48,074 15,749
May 5% 70,776 5% 3,539 46 2.7 25,179 8,417
Jun 3% 42,466 5% 2,123 49 2.9 13,905 4,698
Jul 3% 42,466 5% 2,123 54 3.3 12,375 4,249
Aug 5% 70,776 5% 3,539 55 3.3 20,240 6,969
Sep 8% 113,242 5% 5,662 52 3.1 34,435 11,752
Oct 9% 127,397 5% 6,370 44 2.5 48,046 15,948
Nov 11% 155,708 5% 7,785 39 2.2 68,041 22,224
Dec 14%198,174 5%9,909 32 1.8 108,521 34,710
100% 1,415,525 70,776 614,419 200,819
219%
kBtu
Cooling Load 212,329
Month % Load kBtu Ave Temp COP kBtu kWh
Jun 20% 42,466 49 4.0 10,675 3,129
Jul 40% 84,932 54 3.9 21,602 6,331
Aug 40%84,932 55 3.9 21,652 6,346
100% 212,329 53,930 15,806
394%
Page 3
Alaska Energy Engineering LLC Summary
25200 Amalga Harbor Road Tel/Fax: 907-789-1226
Juneau, Alaska 99801 alaskaenergy@earthlink.net
Wastewater Treatment Plant
Heating System Optimization Analysis
Baseline Economic Factors
Economic Factors Energy Inflation
Study Period (years) 30 Fuel Oil 6.6%
Nominal Discount Rate 5.5% Electricity, Yrs 1-2 9.0%
General Inflation 2.9% Electricity, Yrs 6-30 2.5%
Base Case: 6.6% Fuel Oil, 2.5% Electricity Construction Maintenance Energy Total
Baseline Fuel Oil Boilers $201,000 $147,000 $2,141,000 $2,489,000
Effluent Heat Pump System $810,000 $248,000 $451,000 $1,509,000
High Fuel Oil Case: 8% Fuel Oil, 2.5% Electricity Construction Maintenance Energy Total
Baseline Fuel Oil Boilers $201,000 $147,000 $2,662,000 $3,010,000
Effluent Heat Pump System $810,000 $248,000 $480,000 $1,538,000
Low Fuel Oil Case: 4.8% Fuel Oil, 2.5% Electricity Construction Maintenance Energy Total
Baseline Fuel Oil Boilers $201,000 $147,000 $1,643,000 $1,991,000
Effluent Heat Pump System $810,000 $248,000 $423,000 $1,481,000
High Electricity Case: 6.6% Fuel Oil, 4% Electricity Construction Maintenance Energy Total
Baseline Fuel Oil Boilers $201,000 $147,000 $2,143,000 $2,491,000
Effluent Heat Pump System $810,000 $248,000 $515,000 $1,573,000
Low Electricity Case: 6.6% Fuel Oil, 1% Electricity Construction Maintenance Energy Total
June 26, 2012
Present Worth
Page 4
Alaska Energy Engineering LLC Life Cycle Cost Analysis
25200 Amalga Harbor Road Tel/Fax: 907.789.1226
Juneau, Alaska 99801 alaskaenergy@earthlink.net
Wastewater Treatment Plant
Baseline Fuel Oil Boilers
Basis
Economic Factors Energy Inflation
Study Period (years) 30 Fuel Oil 6.6%
Nominal Discount Rate 5.5% Electricity, Yrs 1-2 9.0%
General Inflation 2.90% Electricity, Yrs 3-30 2.5%
Real Discount Rate 2.5%
Construction Costs Qty Unit Base Cost Year 0 Cost
Demolition
Remove boilers 1 ls 2,000.00 $2,000
Removing piping and appurtenances 1 ls 2,500.00 $2,500
Remove heating pumps 1 ls 750.00 $750
New Heating Plant
Boiler, 954 MBH with appurtenances 2 ls 20,000.00 $40,000
Primary piping, pumps and appurtenances 1 ls 15,000.00 $15,000
Secondary loop and appurtenances 1 ls 12,000.00 $12,000
Chimney 1 ls 4,000.00 $4,000
Controls 16 pts 2,000.00 $32,000
Contingency
Design contingency 20% $21,650.00
General Overhead & Profit 30% $38,970.00
Design fees 10% $16,887.00
Owner's project costs 8% $14,860.56
Total Construction Costs $201,000
Maintenance Costs Years Qty Unit Base Cost Present Value
Maintenance and Repair
Boiler Maintenance
Daily: 5 minutes per day 1 - 30 22 hrs $60.00 $26,444
Monthly: 2 hours per month, ea 1 - 30 48 hrs $60.00 $58,585
Annual: 8 hours, 2x per year 1 - 30 32 hrs $60.00 $39,056
Parts Allowance 1 - 30 2 LS $150.00 $6,103
Pump maintenance 1 - 30 4 ea 200.00 $16,685
Total Annual Costs $147,000
Energy Costs Years Qty Unit Base Cost Present Value
Fuel Oil 1 - 30 15,030 gals $4.01 $2,131,070
Electricity, Years 1-5 1 - 2 4,028 kWh $0.109 $922
Electricity, Years 6-30 3 - 30 4,028 kWh $0.13 $9,165
Total Energy Costs $2,141,000
$2,489,000
0
0
0
June 26, 2012
Year
0
0
0
0
0
Present Worth
0
0
0
0
Page 5
Alaska Energy Engineering LLC Life Cycle Cost Analysis
25200 Amalga Harbor Road Tel/Fax: 907.789.1226
Juneau, Alaska 99801 alaskaenergy@earthlink.net
Wastewater Treatment Plant
Effluent Heat Pump System
Basis
Economic Factors Energy Inflation
Study Period (years) 30 Fuel Oil 6.6%
Nominal Discount Rate 5.5% Electricity, Yrs 1-2 9.0%
General Inflation 2.90% Electricity, Yrs 3-30 2.5%
Real Discount Rate 2.5%
Construction Costs Qty Unit Base Cost Year 0 Cost
Recycled Effluent
Recycled Effluent Pump
Replace motor 1 ls $1,500.00 $1,500
Install VFD 1 ls $7,500.00 $7,500
Recycled effluent piping to heat exchanger 1 ls $1,200.00 $1,200
Heat exchanger and appurtenances, stainless steel 1 ls $25,000.00 $25,000
Recycled effluent discharge to influent well 100 lnft $40.00 $4,000
Heating System
Boiler, 954 MBH with appurtenances 1 ls $20,000.00 $20,000
Primary piping, pumps and appurtenances 1 ls $30,000.00 $30,000
Secondary loop and appurtenances 1 ls $12,000.00 $12,000
Chimney 1 ls $4,000.00 $4,000
Heat pump room with ventilation 400 sqft $75.00 $30,000
868 MBH water-to-water heat pump 1 ls $140,000.00 $140,000
Evaporator pump, 3 HP and piping 1 ea $6,000.00 $6,000
Condenser pump, 3 HP and piping 1 ea $6,000.00 $6,000
Heating tank, 400 gallons 1 ls $10,000.00 $10,000
Distribution
Increase AHU heating coil size 5 ea $3,000.00 $15,000
Replace baseboard heaters 12 lnft $60.00 $720
Replace cabinet unit heater 1 ea $1,750.00 $1,750
Replace unit heaters 16 ea $1,400.00 $22,400
DDC Controls
Heating 24 pts $2,000.00 $48,000
Electrical
Electric subpanel 1 ls $40,000.00 $40,000
Electrical, 3-phase power 3 ls $3,500.00 $10,500
Electrical, 1-phase power 1 ls $1,500.00 $1,500
Contingencies
Design contingency 20% $87,414.00
General Overhead & Profit 30% $157,345.20
Design fees 10% $68,182.92
Owner's project costs 8% $60,000.97
Total Construction Costs $810,000
June 26, 2012
Year
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Page 6
Alaska Energy Engineering LLC Life Cycle Cost Analysis
25200 Amalga Harbor Road Tel/Fax: 907.789.1226
Juneau, Alaska 99801 alaskaenergy@earthlink.net
Wastewater Treatment Plant
Effluent Heat Pump System
June 26, 2012
Maintenance Costs Qty Unit Base Cost Present Value
Maintenance and Repair
Heat Pump
Daily: 5 minutes per day 1 - 30 30 hrs $60.00 $37,124
Monthly: 30 minutes per month 1 - 30 6 hrs $60.00 $7,323
Every Three Months: 30 minutes each 1 - 30 2 hrs $110.00 $4,475
Annual: 8 hours per year 1 - 30 8 hrs $110.00 $17,901
Contracted Tune-up: Every Five Years 5 - 5 1 ls $1,500.00 $1,291
Contracted Tune-up: Every Five Years 10 - 10 1 ls $1,500.00 $1,140
Contracted Tune-up: Every Five Years 15 - 15 1 ls $1,500.00 $1,006
Contracted Tune-up: Every Five Years 20 20 1 ls $1,500.00 $888
Contracted Tune-up: Every Five Years 25 25 1 ls $1,500.00 $784
Parts Allowance 1 - 30 1 LS $200.00 $4,068
Heat exchanger cleaning 1 - 30 16 hrs $60.00 $19,528
Recycled influent intake cleaning, 1 hour per month 1 - 30 12 hrs $60.00 $14,646
Boiler Maintenance
Daily: 5 minutes per day 1 - 30 22 hrs $60.00 $26,444
Monthly: 1 hours per month 1 - 30 12 hrs $38.50 $9,398
Annual: 8 hours, 1x per year 1 - 30 8 hrs $38.50 $6,265
Parts Allowance 1 - 30 1 LS $150.00 $3,051
Pump maintenance 1 - 30 5 ea 200.00 $20,856
Replacement
Heat pump replacement 18 - 18 1 ea 112,000.00 $71,474
Total Annual Costs $248,000
Energy Costs Qty Unit Base Cost Present Value
Fuel Oil 1 - 30 835 gals $4.01 $118,393
Electricity, Years 1-5 1 - 2 132,891 kWh $0.109 $30,428
Electricity, Years 6-30 3 - 30 132,891 kWh $0.13 $302,332
Total Energy Costs $451,000
$1,509,000
Years
Years
Present Worth
Page 7