Exergoeconomic and Enviroeconomic Analyses of Hybrid Electric Vehicle Thermal Management Systems

Abstract

Thermal management systems (TMSs) are one of the key components of hybrid electric vehicles in terms of their impact on vehicle efficiency, as well as the vehicle’s overall cost and environmental footprint. In this paper, exergoeconomic and enviroeconomic (environmental cost) analyses of hybrid electric vehicle thermal management systems are conducted with respect to various system parameters as well as operating conditions. In the exergy analysis, balance equations are applied to each system component of the TMS, in order to determine exergy destruction rates and calculate the exergy efficiencies of the system and its individual components. In the economic analysis, investment cost rates are calculated with respect to equipment costs, which are determined by cost correlations for each system component, and capital recovery factors. Thus, by combining the two analyses, an exergoeconomic model is created whereby the exergy streams are identified, fuel and productsare defined and cost equations are allocated for each component. The costs from the economic analysis are used to determine the unit cost of exergy, cost rate of exergy destruction as well as other useful exergoeconomic variables for each component. Moreover, an enviroeconomical (environment cost) analysis is also conducted based on the established carbon price associated with the released CO₂ to the environment, corresponding to the indirect emissions from the electricity used in the TMS under varying carbon prices and electricity generation mixes.

Nomenclature

A:

Area (m²)

C:

Cost per unit of exergy ($/kj)

$\dot{\mathrm{C}}$ :

Cost rate associated with exergy ($/h)

C _CO2 :

CO₂emissions price per year ($/year)

D:

Diameter (m)

$\dot{E}\mathrm{x}$ :

Exergy rate (kW)

f :

Exergoeconomic factor

h :

Specific enthalpy (kJ/kg)

k :

Cost per mass flow rate ($s/kg)

K :

Energy storage capacity (kW)

$\dot{m}$ :

Mass flow rate (kg/s or L/min)

N :

Annual number of operation hours (h)

P :

Pressure (kg/m s²)

Pr:

Prandtl number

$\dot{Q}$ :

Heat transfer rate (kW)

r:

Relative cost difference

Re :

Reynolds number

s :

Specific entropy (kJ/kg K)

t :

Total working hours per year (h/year)

T :

Temperature (K or °C)

T ₀ :

Ambient temperature (K or °C)

$\dot{\mathrm{W}}$ :

Work rate or power (kW)

Z :

Purchase equipment cost ($)

$\dot{\mathrm{Z}}$ :

Cost rate associated with the sum of capital investment ($/h)

Δ:

Change in variable

φ :

Maintenance factor

ψ :

Exergy

n :

Equipment lifetime (years)

0:

Ambient

act :

Actual

bat :

Battery

cool:

Coolant

c cond :

Condenser

ch :

Chiller

comp :

Compressor

D :

Destruction

e :

Exit

elect :

Electricity

en :

Energy

ex :

Exergy

evap :

Evaporator

F :

Fuel

gen :

Generation

i :

In

k :

Component

P :

Product

q :

Heat

ref :

Refrigerant

s :

Isentopic

txv :

Thermal expansion valve

w :

Work

wg :

Water/glycol mix

COP:

Coefficients of performance

CRF:

Capital recovery factor

EV:

Electric vehicle

GHG:

Greenhouse gas

GWP:

Global warming potential

TMS:

Thermal management system

TXV:

Thermal expansion valve