IEEE Electrification - December 2020 - 42

The mix of wind, flow
batteries, diesel, fuel
cells, and natural
gas generators
allows for the
removal of 500 kW
of diesel generation,
which reduces
emissions by more
than 43%.

the MG. A wind turbine is modeled in
HOMER as a device that converts
kinetic energy of the wind into electricity according to a specific power
curve, assuming a standard air density of 1.225 kg /m 3. The monthly average wind speed data was obtained
from NASA's database. The economical and technical input parameters
for the model in HOMER are presented in Table 4.

Flow Batteries

A battery is modeled in HOMER as a
storage device with a fixed round-trip
energy efficiency that limits the rate
of charge and discharge, the depth of
discharge, and its lifetime. The batteries used in the MG model were alliron flow batteries with 50- and 100-kW peak power,
which can deliver up to 400 kWh. This type of storage
offers cost-effective, safe, and environmentally friendly
solutions due to the abundance of iron and its nontoxic
nature. The parameters for the implemented flow battery
model in HOMER are presented in Tables 5 and 6.

Natural Gas Generator
In this study, two types of natural gas generators (NG)
were considered at the ac side of the MG, which were

TABLE 4. The parameters and costs of wind

generators.

O&M
Cost
(CAD$/ Hub
Cut-In
(CAD$/u) Year)
Height Speed
178,069

5,342

23 m

Cut-Out
Speed Lifetime

2.75 m/s 20 m/s 20 years

u: unit.

integrated into the planning problem to analyze the impact of this
type of generation in RCs. The price
of the natural gas was assumed to be
fixed at CAD$0.3/m3 for all years.
The economical and operational
input parameters for the models
in HOMER are presented in Table 7.

Hydrogen System

Fuel cells are continuously operating
batteries which generate electricity
from a fuel, such as hydrogen, and an
oxidant, such as air. To model a hydrogen system, an electrolyzer and a
hydrogen tank need to be implemented, with the electrolyzer generating
hydrogen through water electrolysis,
which involves the consumption of
electricity, while the tank stores this hydrogen at high
pressure to be used later by the fuel cell. The costs and
main characteristics of these elements are presented in
Tables 8, 9, and 10.

Results
In this section, the optimal and some feasible simulation
results are compared with the base case which contains
only diesel generators. The obtained results show different combinations of renewables, storage, gas, and fuel
cells, for two case-studies, considering different storage
capacities. The following is the criteria used to perform
the study:
xx
The load was assumed to grow at 1.41% per year.
xx
The optimization module was used to obtain the optimal and feasible results by assuming 10% error from
the predicted values of the model, such as demand
and solar irradiation.
xx
An additional cost of CAD$2.35 million with 5% per
year growth was added to the variable and capital
cost of investment, since HOMER does not consider

TABLE 5. The parameters and costs of 50-kW flow batteries.
Cost (CAD$/u)

O&M (CAD$/Year)

SoCo

SoCmin

Nominal Voltage

Round-Trip
Nominal Current Efficiency

Lifetime

370,936

7,418

50%

15%

500 V

120 A

25 years

78%

SoC: state of charge.

TABLE 6. The parameters and costs of 100-kW flow batteries.

Cost
(CAD$/u)

O&M (CAD$/
Year)

SoCo

SoCmin

Nominal Voltage

Nominal Current

Round-Trip Efficiency

Lifetime

372,873

7,457

50%

15%

500 V

240 A

78%

25 years

I E E E E l e c t r i f i cati o n M agaz ine / DECEMBER 2020

IEEE Electrification - December 2020

Table of Contents for the Digital Edition of IEEE Electrification - December 2020