Biomass Heating on a Small Scale
Timothyy A. Volk
SUNY – ESF, Syracuse, NY
Sustainable Use of Renewable Energy (SURE)
SUNY ESF, Syracuse, NY
November 4,
4 2009
US Energy Sources
History of U.S.
U S Energy Use
(EIA 2007)
Energy Use in U.S.
US
39 6
39.6
31 1
31.1
28.8
Thermal/Other
Transportation
p
Electric Power
• Approximately 1/3 of
primary energy use in
the U.S. is for thermal
applications
• 82% of heating oil used
in the U.S. is consumed
in the Northeast U.S.
NE US Heating Characteristics
• Reliance on oil as a heating source creates vulnerability to
fluctuating oil prices
• Currently spending over $13 Billion/yr on heating oil in the NE
• EIA estimates that over the next 10 yyears heating
g oil will average
g
$3.59/gallon
Benefits from Biomass
• It is a renewable,, sustainable resource
• Fuel is available in large quantities across the
northeast and elsewhere
• Use of local, natural resources creates independence
and reinforces local networking
• Biomass
Bi
fuel
f l dollars
d ll andd the
th value
l added
dd d from
f
their
th i
conversion stays in the local economy
Benefits from Biomass
• Large
g or innovative projects
p j
pave
p
the wayy for other
projects or industries
• Biomass fuel prices have historically been fairly
stable
bl
• Biomass price increases will be more gradual than
competing fuels
• Future energy and carbon taxes should not impact
biomass
b
o ss fuels
ue s
• Low grade markets can improve opportunities for
sustainable forest management
Common Concerns
• Higher capital and M&O costs
• Biomass fuel requires more attention during
operation
p
• Attention to fuel quality is required
• May have to build and maintain a local fuel
supply network
• Concerns with emissions from burning biomass
• Biomass
i
systems may require
i more maintenance
i
than conventional fuel systems
$/M
MMBtu
Prices of Residential Heat Sources in MA
(Kingsley 2009)
Heating Cost Assumptions
Fuel
Wood Pellets
Heatingg Value
16.4 million BTU/Ton
Efficiencyy
83%
Fi
Firewood
d
20 million
illi BTU/Cord
BTU/C d
77%
Coal - Anthracite
Fuel Oil #2
Natural Gas
25 million BTU/Ton
134,500 BTU/Gal
1.03 million BTU’s per MCF
80%
83%
80%
Propane
91,200 BTUs Per Gallon
80%
Electricity
3413 BTU/Kwh
100%
Heating Costs by Fuel Type
$ per MBTU
Annual Fuel
Costs**
F l
Fuel
C
Cost
Wood Pellets
250 $/ton
18.37
918.50
Firewood
250 $/cord
16.23
811.50
Coal
200 $$/ton
10.00
500.00
Fuel Oil #2
2.50 $/gallon
22.39
1,119.50
Natural Gas
2 16 $/ccf
2.16
26 21
26.21
1 310 50
1,310.50
Propane
3.00 $/gallon
41.12
2,056.00
Electric
0 14 $/kwh
0.14
41 02
41.02
2 051 00
2,051.00
• Google ‘fuel
fuel calculator
calculator’
• http://www.fpl.fs.fed.us/documnts/techline/fuel-valuecalculator.pdf
Pellet fuels Institute - http://www.pelletheat.org/3/residential/compareFuel.cfm
Important Biomass Characteristics
• Main characteristics that influence the use of
bi
biomass
as a source off energy are:
–
–
–
–
heating value
moisture content
density
chemical composition
• volatile matter
• amount of solid carbon
• ash content and composition, melting and slagging behavior
• Characteristics vary somewhat by
– type of plant material – woody versus herbaceous
– species within general types
– handling
h dli andd processing
i procedures
d
Higher Heating Value (HHV)
• the GROSS amount of heat energy released
when biomass is combusted at standard
atmospheric conditions and 60% relative
h idi
humidity
• Also called the Gross Heating Value (GHV),
Calorific Value (CV) or Calorimetric Value
(CV)
(
• includes the calorific value of the fuel (bone
dry) and the latent heat of vaporization of the
water in the fuel
Lower Heating Value (LHV)
• the NET amount of heat released when biomass is
combusted at standard atmospheric conditions and
60% relative humidityy
• Also called Net Heating Value (NHV) or Lower
Calorific Value ((LCV),
), Net calorific value ((NCV),
),
Effective Heating Value (EHV)
• The difference between HHV and LHV is the latent
heat of vaporization, which depends on the moisture
content of the fuel and its hydrogen content
Moisture Content
• Fuels are often compared on a dry
weight basis (0% moisture content)
– odt – oven dry tons
– bone dry weight is same as oven dry
• Green weight is less rigorously
defined term but is used to express the
g of freshly
y harvested biomass
weight
• However, biomass is often bought and
green weight
g basis
sold on a g
Moisture Content
Energy C
Contnet (LHV - B
Btu/lb)
9,000
8,000
7,000
6,000
5,000
4,000
3 000
3,000
2,000
1,000
0
0
15
20
25
30
35
40
45
50
55
60
Moisture Content (w et w eight basis)
• Need
N d tto understand
d t d fuel
f l moisture
it
content
t t (MC)
• For wood ranges from <10% for wood residues up to 65%
• Numerous factors influence MC
– climate, species, harvesting method, time of harvest, length and method of
storage
Moisture Effects
• If a conversion facility has been designed to use high moisture
fuels no technical problems will occur but high moisture
fuels,
content will impact the overall feasibility of the energy
production:
– the more water fuel contains ->
> lower heating value ->
> fuel
efficiency is lower
– the more water fuel contains -> bigger boiler volume
needed -> more expensive boiler
– transportation of water is expensive because there is no
benefit to the overall energy system
– most automated systems cannot react to rapid variations in
moisture content resulting in incomplete combustion,
which can change emission profiles
Energy Density
• Knowing the LHV and the bulk density of your
biomass fuel allows you to determine its energy
density
• Useful to know when planning a bioenergy project
since it will effect the size of the plant, storage area
needed, transportation systems, costs etc.
• Biomass energy density is lower than oil or medium
grade coal and is a limitation that increases their
delivered energy costs
Biomass Supply
pp y
Range of Sizes
Wood Heating System Cost-Effectiveness
• Biomass systems are most cost effective when:
– Cost of alternative fuels is high
– Facilityy energy
gy demands are relativelyy large
g
– When they are an alternative to another new system rather
than a replacement for an existing system
– When
h hot
h water or steam heating
h i systems are already
l d in
i
place
Cost Effectiveness vs
vs. Electric
Life cycle costing study using assumptions from Appendix D in Maker (2004).
Cost Effectiveness – vs.
vs Fuel Oil
Life cycle costing study using assumptions from Appendix D in Maker (2004).
Cost Effectiveness vs.
vs Natural Gas
Life cycle costing study using assumptions from Appendix D in Maker (2004).
Questions?
Biomass Energy System
Components – Fuel Storage
• Design for immediate and
long term needs
• Usually below ground
– E
Easy unloading
l di
– Below forest level
– Less obtrusive
• A
Accommodate
d a variety
i off
delivery vehicles
• Size to accommodate 3050% more than one full
load for small systems
• Larger systems based on
available storage space
Berlin, VT and Newport, VT (Maker 2004)
Delivery Options
• Walking floor
trucks are common
• Design system with
some flexibility for
different vehicles
and types of fuels
Delivery Options
Biomass Energy System
Components – Fuel Storage
• Storage size needed
• Need to know
–
–
–
–
–
Wood storage facility (GSES 2005)
system s energy output
system’s
amount of load
fuel’s heating value
Bulk density
Heating efficiency
Storage Space
Boiler output x hours of load
LHV x bulk density x system
efficiency
Cost Effectiveness – Case Studyy
• Conversion from oil to new wood-chip
heating system
• 220,000
,
ft2 high
g school
• Capital costs (boiler system, building, hot
water, engineering) - $590,000
• 30% VT state aid to schools for capital
costs
• Interest rate – 4.6%
• Term – 20 years
Cost Effectiveness – Case Studyy
• Discount rate of 5.6%
• 85% off hheatt for
f school
h l from
f
wood,
d
rest from oil backup system
• Oil price - $1.00/gallon, 3% inflation
• Wood-chip - $28/ton, 2% inflation
Bulk Density
• Lower end is for softwoods, higher end of range is
generally hardwoods
Measuring Moisture Content
• Measure fresh or wet weight of material, dry at
105oC to a constant weight
i h
m.c. wet basis = Total wet weight of wood – oven-dry weight X 100
Total weight weight of wood
g of wood – oven-dryy weight
g X 100
m c dry basis = Total wet weight
m.c.
Oven-dry weight
Moisture Content
• For a sample with a wet weight of 1200 g
and an oven dry weight of 650 g the m.c.
what is the moisture content on
– A wet basis?
– A ddry bbasis
i
Moisture Content
• Wet basis is 45.8%
• Dry basis 84.6% on a dry basis
• Other characteristics of the biomass are the
same regardless of how it is reported
• Moisture content is usually reported on a wet
weight basis, but be sure you know what
values are being used