2.4 Mathematical representations for various costs and emissions
For calculations of NPC, COE and CO2 emissions HOMER follows some mathematical formula as discussed in [7].
HOMER calculates the NPC for all possible combinations of the system using:
(12)
Here,
CNPC = Net Present Cost.Cann.tot = Total annualized cost.i = Real interest rate (annual)Rproj = Lifetime of the project.CRF (.) =Capital recovery factor.
HOMER also calculates the Cost of Energy for the simulated system. For this it uses [7] this relation below:
(13)
Here,
Cann.tot = Total cost on annual basis. Amount of energy per year sold to the grid. The total primary load amounts. The total deferrable load amounts.
How much CO2 is emitted from the hybrid system is also calculated. To do so the following formula is being used [7]:
(14)
Here,
The total amount of COemitted from the system. The value of heating of Fuel in MJ/L. Quantity of Fuel in Liter. Fraction of Oxidized carbon. The emission factor of Carbon in ton carbon/TJ.
For this calculation it should be kept in mind that 1 g of carbon is contained by 3.667 g of CO2.