PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 97 NR 9/2021 141
Fig. 6 A flowchart
of HOMER simulation process
Fig. 7
HOMER Schematic for grid connected model (on-grid)
Fig. 8 HOMER Schematic for standalone model (off-grid)
The hybrid power model designed in the HOMER program is
shown in Fig. 7 & Fig. 8 respectively. This model consists of
Generic 3 kW wind turbine, Generic PV flat plate, electronic
converter, Generic Li-ion 1kWh battery and residential load.
Optimization analysis
HOMER simulates all the achievable solutions for the
system, then shows a list of all feasible system patterns
planned gradually from lowest to highest in NPC (Net
Present Cost) and excludes all the infeasible configurations.
HOMER use a proprietary derivative-free algorithm to
exploration for the optimum solution among all these
feasible systems. The least NPC is the optimum design for
the system [18],[19],[20].
Many researchers have utilized
HOMER for analyzing
[21],[22],[23],[24]. Analysis with HOMER needs a wide
range of data on renewable resources, energy storage
systems, control algorithms and economic restrictions. The
evaluation criteria of the HOMER assessment are the Net
Present Cost (NPC) and the Cost of Energy (COE). The
COE is defined in HOMER as the mean cost/kWh of
valuable power generated by the system. To compute the
value of COE, Homer program will divide the yearly cost of
electricity production by the beneficial generated electricity.
the COE can be calculated by the relation in the following
equation (6):
(6)
,
/
,
,
,
Where (
E
grid,sales
) is the overall
sold energy from the grid
in(kWh/year), (
E
prim,DC
) is the DC primary load served in
(kWh/year), (
E
prim,AC
) is the AC primary load served
in(kWh/year) and (
C
ann,tot
) is the overall yearly cost in
($/year).
The total NPC is calculated in HOMER using the relation
in the following equation (7), where (
C
ann,tot
) is the overall
yearly cost in ($/year), (
CRF)
is the capital recovery factor,
(
R
proj
) the project lifetime in year, (
i) the interest rate %,
While the (
CRF) is calculated by the equation (8) [11].
(7)
,
,
(8)
( + 1)
(
+ 1)
In order to calculate the optimal cost, the model has been
configured to simulate the same electrical load with the off-
grid and on-grid design.
Table 1. The Data Input for Proposed Model.
Inputs PV
1kW
Wind
Turbine
Li-ion
Battery
(167Ah)
Converter
1kW
Capital Cost
500 $
5000 $
100 $
200 $
Replacement Cost
400 $
4400 $
80 $
160 $
Operation &
Maintenance
8 $
10 $
1 $
1 $
Lifetime 25
year
25 year
-
25 year
Hub Height
-
17m
-
-
Efficiency
13 %
-
-
95 %
Derating
Factor
80 %
-
-
-
Operating
temperature
47°C -
-
-
Initial SOC
-
-
100 %
-
Minimum SOC
-
-
20 %
-
Nominal Voltage
-
-
6 V
-
Nominal Capacity
-
-
1 kwh
-
Maximum Capacity
-
-
167 Ah
-
142 PRZEGLĄD ELEKTROTECHNICZNY, ISSN 0033-2097, R. 97 NR 9/2021
Fig. 9 Capital & Replacement cost curve for the Li-ion battery.
A Generic PV flat panel is utilized, these
photovoltaic
panels are flat plate builds by Generic, the wind unit is an
A.C Generic 3 KW, also a generic lithium-ion battery has
been utilized with a nominal capacity of 1 kWh, and a
generic converter this is important to supports the hybrid
system design in off-grid configuration. From observing the
cost curve in Fig. 9, it is clear
that varying the amount of
batteries will affect the cost, which will ultimately affect the
total NPC.
The grid model unit is a local grid with 10kW capacity,
power rate definition is 0.1$\kWh and sellback rate of
0.05$\kWh, when there is power shortage, the grid provides
electricity to achieve a load request. Further, it receives
electrical power when excessive energy is available.
