ShipPowerModel.Rd
The ShipPowerModel package by the U.S. Environmental Protection Agency
provides functions for estimating the propulsive power of commercial marine
vessels (CMV). It also provides functions for estimating auxiliary and boiler
engine loads. This package can be used in conjunction with vessel
characteristics and emission factors (see the ShipEF
package) to
estimate CMV air emissions.
The four functions below represent different methods for estimating vessel power:
calcPropPwr
- Propeller law, which was used as the basis
for load factor estimates in the U.S. EPA's 2014 National Emissions Inventory
calcAdmPwr
- Admiralty formula, which was used as the
basis for load factor estimates in the Third IMO Greenhouse Gas Study
calcHMPwr
- Implementation of the Holtrop & Mennen model
as used in the U.S. EPA's 2017 National Emissions Inventory
calcKristPwr
- Implementation of Kristensen's SHIP-DESMO
vessel power model
In addition, calcAuxBoilerLoad
is another primary function,
which assigns auxiliary and boiler engine loads based on ship type, ship
subtype, and operating mode.
Every function in this package has been optimized to work on vectors of data. This is because the input datasets required to calculate instantaneous ship power are very large. For example, the resolution of the ship activity data may be as fine as every 5 minutes--or even more. Multiply this across the hundreds or thousands of vessels that may be included in the analysis, and the data become to large to handle via individual function calls per row of data.
Therefore, it is recommended that users store their data in data.table
objects and pass columns from the data.table as arguments to the functions in
this package. Other forms of vectorization work, as well, such as using
data.frame
. The function documentation specifies which arguments can
be vectorized, and the vignettes introduced below provide examples on how to
do simple vectorization using data.frame
.
An overview of each model can be found in the following vignette:
vignette("OverviewOfPowerModels", package="ShipPowerModel")
Each model also has its own vignette: