HomeMy WebLinkAboutNew Stuyahok Heat Recovery - Assessment
9/19/2012
New Stuyahok, AK
Preliminary Heat Recovery Assessment
AVEC Power Plant and New Stuyahok School
Prepared by Devany Plentovich
Program Manager, Alaska Energy Authority
Introduction
The Alaska Village Electrical Cooperative and the Southwest Region School District requested a pre-
feasibility analysis of the potential of providing recovered heat from the existing New Stuyahok power
plant for heating the adjacent New Stuyahok High School, built in 2007.
PCE data from 2009 and 2012 was used for the power plant loads. AVEC provided existing diesel
generation equipment and SWRSD provided annual fuel usage for FY 2009 – 2012 for the high school. A
site visit WAS NOT conducted for this analysis, so it is recommended that all assumptions and
calculations be verified in the field.
There is already momentum in the community for the construction of a heat recovery system. The New
Stuyahok High School has already purchased some piping materials for heat recovery construction and
piping tie-in for a heat recovery system are in place in the power plant.
Analysis
The purpose of this assessment is to provide an estimate of the heat that can be recovered from the
jacket water of the New Stuyahok power plant diesel engines and used to offset heating oil consumption
at the nearby high school. Useable recovered heat is quantified in gallons of heating fuel saved using a
gross heating value of 140,000 BTU per gallon for #2 arctic diesel fuel and an overall efficiency of 75%
for boilers.
The estimated average annual heating fuel consumption for the New Stuyahok High School is 30,533
gallons. The boiler room is the school is located approximately 300’ from the power plant.
The current generators in the New Stuyahok power plant are as follows:
#1 – Cummins QSXx15G9 – 499 KW
#2 – Detroit Series 60 1800 RPM – 363 KW
#3 - Caterpillar 3456 – 505 KW
The Caterpillar 3456 is currently not converted to a marine jacket configuration which increases the
recoverable heat available by up to 60%. The analysis was performed using recoverable heat rates for a
marine jacketed configuration.
Using a heat recovery utilization spreadsheet developed by Alaska Energy and Engineering, recoverable
heat was estimated using the monthly total electrical power production, engine heat rates, building
heating demand, and heating degree days. Passive losses for the power plant heat and piping and arctic
piping losses were estimated to be similar to the Buckland Heat Recovery System. The spreadsheet uses
assumed time-of-day variations for electrical power production and heat demand. Power Cost
Equalization (PCE) data for FY 2009 – FY 2012 were averaged and used in the spreadsheet.
Heating degree-days for Dillingham were used in the analysis. The spreadsheet uses monthly heating
degree days to distribute annual fuel consumption by month. The monthly heat load is then allocated
by hour of day using an estimated daily temperature variation (diurnal cycle). The end-user hourly heat
load is compared to the hourly available heat from the power plant, less power plant heating loads and
parasitic piping losses, and the net delivered heat to the end-user is determined.
Based on the analysis using a marine jacketed Cat 3456 genset and assuming parasitic heating loads
similar to the Buckland power plant, a heat recovery system in New Stuyahok could displace
approximately 27000 gallons of heating fuel at an annual savings of $119,000. The analysis is in the
attached file “New Stuyahok Heating Analysis and Graph”.
Capital Estimate
A capital estimate was developed based on the Buckland Heat Recovery Feasibility Study developed by
Alaska Energy and Engineering in 2011 and input from Alaska Village Electrical Cooperative. The
Buckland power plant and generator loads are similar to New Stuyahok and the project also includes the
conversion to a marine jacketed Cat 3456.
The school has purchased much of the piping required to complete the construction. Because the actual
required scope to complete this project is not known until a site visit can be made, the capital estimate
is a worst case only for the purpose of conducting the economic analysis of the project. The actual
capital requirements will most likely be less.
The capital estimate:
Site and Exterior Work $70,000
Power Plant Additions including Marine Jacket
Conversion $120,000
School connections $40,000
Mechanical, Controls, Insulation $22,000
Overhead $30,000
Miscellaneous $13,000
Freight $70,000
Construction Sub-total $365,000
Design and Construction Adm $25,000
Construction Management $25,000
Project Sub-Total $415,000
Contingency - 20% $83,000
Total Project Cost $498,000
Economic Analysis
A Benefit to Cost Ratio economic analysis was performed using the Renewable Energy Fund B/C Model
worksheet developed by ISER. Using the capital estimate of $588,000, an annual displacement of 27,000
gallons of diesel fuel, and $500 additional annual O&M costs, the project results in a B/C ratio of 4.56
(attached file). Any project with a B/C ratio above 2.0 receives full points for the economic analysis
category in the Renewable Energy Grant program.
Conclusion and Recommendations
Based on this preliminary analysis, it appears that the design and construction of a heat recovery system
in the New Stuyahok power plant supplying recovered heat to the High School is a viable project. The
B/C ratio is more than sufficient to indicate a favorable project even using worst case capital costs.
It is recommended that the project team develop a realistic capital estimate taking into consideration all
of the work that has been completed to date. This project is eligible for application to the Renewable
Energy Fund. The deadline for applications for the RE Fund Round 6 is September 24, 2012.