The Feedstock page inputs define the biomass resource of the location you specify on the Ambient Conditions page, and the physical content of the resource.
For a technical description of the biopower model, see Jorgenson, J.; Gilman, P.; Dobos, A. (2011). Technical Manual for the SAM Biomass Power Generation Model. 40 pp.; NREL Report No. TP-6A20-52688. http://www.nrel.gov/docs/fy11osti/52688.pdf
You can use any combination of the following options to specify the feedstock:
•Download feedstock data from the NREL Biofuels Atlas (http://maps.nrel.gov/biomass) to determine the feedstock available for common agricultural and wood residues at the location you specify on the Location and Ambient Conditions page.
•Specify feedstock availability, obtainability, and moisture content by hand.
•Specify elemental composition and heating values for up to two user-specified feedstocks.
•Specify properties of a supplemental coal feedstock.
Biomass Feedstock Resource
Describes the amount of biomass available as an energy resource within a certain radius of a the location specified on the Location and Ambient Conditions page.
Collection radius, miles
The collection radius defines a circle with the location specified on the Location and Ambient Conditions page at its center.
Increasing the collection radius increases the amount of available biomass, but also causes the distance-dependent feedstock delivery costs (specified on the Feedstock Costs page) to increase. Generally, a collection radius of greater than 50 miles is unrealistic.
Resource Available
Quantity of each resource available in bone dry tons/year.
Resource Obtainability
The obtainability percentages apply to the quantities under Resource Available to define the obtainable resource.
Note. The available resource data from the NREL Biofuels Atlas assume that a certain amount of harvest residue remains on the field to prevent soil erosion and maintain nutrients. The resource obtainability percentages apply to the portion of the residue that does not remain on the field.
Moisture (wet %)
The average annual wet moisture content of the crop or wood residue as collected.
SAM uses the wet basis moisture (Mwb), which is the ratio of the weight of water to the weight of the wet biomass weight.
Biomass moisture can also be quantified using the dry basis moisture (Mdb), which is the ratio of the weight of water to the dry biomass weight. The following equations show the relationship between the two moisture content quantities:
Mwb = Mdb ÷ (1 + Mdb)
Mdb = Mwb ÷ (1 - Mwb)
Traditional Residues
Traditional residues generally fall into two categories: field residue and process residue.
•Bagasse is a residue that is product of sugarcane and sorghum processing.
•Barley straw, corn stover, rice straw, and wheat straw are all field residues that remain after harvest.
•Forest residues usually refer to lumber that is unfit for sawmill processing, such as smaller-diameter branches or stumps, misshapen trees, and undergrowth that may fuel forest fires.
•Primary mill residues are wastes generated by mill processes.
•Urban wood waste includes prunings from residential areas, as well as woody construction materials and used pallets.
Dedicated Energy Crops
Dedicated energy crops are grown specifically for use as a fuel. These crops typically have high yields and densities per acre.
•Woody crops are trees such as willow and poplar.
•Herbaceous crops are grasses such as miscanthus and switchgrass.
User-Specified Biomass Feedstocks
You can specify up to two custom feedstocks for biomass resource for locations with biomass resources not listed under Traditional Residues and Dedicated Energy Crops.
Specify Additional Feedstocks
Check the box to specify custom feedstocks.
Feedstock Resource
The annual total obtainable resource quantity in dry tons per year.
Moisture Content (% wet basis)
The average annual wet moisture content of the crop or wood residue as collected.
SAM uses the wet basis moisture (Mwb), which is the ratio of the weight of water to the weight of the wet biomass weight. See above for equations relating the wet and dry moisture content.
Input dry higher heating value (HHV)
Choose this option to specify the feedstock's higher heating value in Btu per dry pound.
Calculate HHV based on elemental composition
Choose this option to have SAM calculate a higher heating value based on the elemental composition values you specify.
Carbon content (wt %)
The mass percent carbon content of the feedstock.
This value is used for defining the combustion reaction and determining the higher heating value.
For biomass, typical carbon content is around 45%-50%. For coal, the carbon content may be as high as 75%-80%.
Hydrogen content (wt %)
The mass percent hydrogen content of the feedstock.
SAM uses the hydrogen content in combustion calculations, and to determine the latent heat loss when hydrogen in the sample is combusted.
Hydrogen content for most solid fuels is 5%-6%.
Nitrogen content (wt %)
The mass percent nitrogen content of the feedstock.
The typical nitrogen content for some biomass and coal can be up to 2%. Many biomass types can be as low as 0.1% nitrogen.
Supplemental Coal Feedstock
In some cases, you may be interested in comparing the performance of biomass feedstocks to traditional fossil fuels. Alternatively, for regions of scarce or costly biomass feedstocks, coal may be used to augment plant capacity.
SAM determines whether a plant is co-fired based on the resource availability quantities you specify. If you specify zero for all of the biomass feedstocks, SAM will model the plant as a coal-fired plant with no biomass.
For co-fired plants, SAM assumes direct co-firing, where coal and biomass are fed to the same boiler.
Use a coal feedstock to augment plant capacity
Check this box to model a plant with coal.
To model a coal-only plant, change all of the biomass feedstock availability values to zero.
Bituminous Coal Resource
Bituminous coal is the most prevalent rank of coal in the United States. It has a high heat content and is found mostly in the eastern US.
Sub-bituminous Coal Resource
Sub-bituminous coal has a slightly lower heat content than bituminous coal and is most commonly mined in Wyoming.
Lignite Coal
Lignite coal is the cheapest and lowest quality rank of coal. Lignite coal mining occurs primarily in Texas and North Dakota.
Resource Available
The annual availability of the coal feedstock in dry tons/year.
Higher Heating Value (HHV)
The coal resource higher heating value in Btu/dry pound. The default values are Bituminous = 13272, Sub-bituminous = 10958, and Lignite = 7875.
Moisture (wet %)
The wet-basis moisture content of the coal feedstock in percent. The default values are Bituminous = 10, Sub-bituminous = 25, and Lignite = 39.
Overall Feedstock Characteristics
Total estimated plant capacity with selected feedstock
The estimated nameplate capacity calculated based on type of biomass, amount of biomass, and performance parameters specified on the Feedstock and Plant Specs pages. In order to increase the capacity, the biomass supplied on the Feedstock page must be directly increased.
SAM does not use the estimated max gross nameplate capacity value in simulations. It is shown purely for reference. The simulation engine computes the actual efficiency, whereas the estimated nameplate capacity is based on an estimated efficiency. The simulation engine takes into account variations like ambient conditions or the dispatch schedule. To capture this temporality, the simulation engine averages the hourly efficiencies.
Average HHV and LHV
SAM calculates and displays the weighted average of the HHV and LHV for each feedstock based the obtainable biomass that you specify. Changing the resource availability or obtainability for one or more feedstock changes the average HHV and LHV values.
Typical heating values for biomass are generally between 7000-8000 Btu/lb (or about 16,000 – 19,000 kJ/kg).
Wt frac of total feedstock
The weight of the biomass and coal feedstock as a fraction of the total feedstock weight.
