Financial Assessment of Microgrid’s Independence using RES and
Hydrogen-Based Energy Storage
MARIOS NIKOLOGIANNIS1, IOANNIS MOZAKIS2, IOANNIS ILIADIS2,
YIANNIS KATSIGIANNIS2
1Institute of Energy, Environment and Climate Change,
Hellenic Mediterranean University,
Estavromenos Campus 71410 Heraklion,
GREECE
Department of Electrical and Computer Engineering,
Hellenic Mediterranean University,
Estavromenos Campus 71410 Heraklion,
GREECE
Abstract: - The main difficulty that microgrids face is an economically feasible state of self-sustainability. The
unpredictable behavior of dispersed Renewable Energy Sources (RES) and their stochasticity along with the
usually high variability of electricity demand is a challenge for the stability of a microgrid. Therefore,
innovative models for the development of energy systems that integrate new technologies in optimal and
sustainable ways are required. Green hydrogen production is an emerging technology aiming to solve such
problems through its use as a storage system within a viable business scheme. Integrating hydrogen production
with RES and storage systems can enhance energy independence and economic opportunities. The focus of
this paper is the proposal of a profitable financial scheme that leads to sufficient levels of the system’s
independence from a main grid. Such an approach is implemented by a cost-effective pathway for a microgrid
located in Crete through the simulation and investigation of its system that achieves high levels of self-
sufficiency by incorporating RES backed by hydrogen-based energy storage. The proposed methodology relies
on assessing the system's sizing through the calculation of values that replicate its operation, with Net Present
Value (NPV) serving as an indicator of the scheme's profitability. The financial evaluation of the investment
predicts, under specific assumptions, a total initial cost equal to 12,037,150.00 EUR, and an NPV of 20 years
equal to 2,489,862,897.40 EUR.
Key-Words: - RES Penetration, Green hydrogen, Hydrogen storage, Energy Storage, Electrolysis, Fuel Cell,
Microgrids, Self-Sustainability.
Received: May 15, 2023. Revised: May 19, 2024. Accepted: June 23, 2024. Published: July 30, 2024.
1 Introduction
The primary goal of a microgrid is to cover its
electricity needs in a viable manner. A promising
solution is the local generation of power, aiming for
independence from the main grid. This shift is
advantageous because the microgrid’s financial
stability can be affected by the grid's price
fluctuations. When prices are low, buying electricity
from a grid-connected provider is cost-effective,
whereas local generation becomes more favorable
when prices rise. To optimize the microgrid's
performance in a rapidly changing energy market,
the development of advanced control systems is
essential.
RES can enhance a microgrid's independence by
supplying locally produced, low-cost electricity,
offering economically advantageous solutions.
However, a significant drawback is the frequency
instability that arises with a higher share of RES in
the energy mix and the limited forecasting accuracy
due to the unpredictable nature of RES production.
Additionally, the restricted size of the microgrid's
premises and the surrounding area may hinder the
efficient installation of RES, making a desirable
energy transition challenging.
A crucial component of a microgrid is its energy
storage subsystem, which stores energy produced by
RES during periods of low demand and discharges it
when needed. However, installing traditional
storage systems, such as lithium batteries, incurs
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2024.19.27
Marios Nikologiannis, Ioannis Mozakis,
Ioannis Iliadis, Yiannis Katsigiannis
E-ISSN: 2224-350X
307
Volume 19, 2024
high costs, making this investment impractical for
small-scale microgrids or projects with limited
resources. Hydrogen-based storage technologies
offer both sustainable and cost-effective solutions.
Green hydrogen is produced through water
electrolysis using electricity generated from
renewable sources like wind and solar power.
Various types of electrolyzers, such as alkaline
electrolyzers (AEL), proton-exchange membrane
electrolyzers (PEMEL), and anion-exchange
membrane electrolyzers (AEMEL), can produce
hydrogen in a gaseous state. These electrolyzers can
be paired with a hydrogen storage tank and a fuel
cell system to increase storage capacity and use the
stored hydrogen gas as fuel for electricity
generation. Beyond reducing carbon emissions, this
design can be appropriately scaled to achieve energy
independence, enhance grid stability, and provide
financial benefits.
This study proposes a methodology for
integrating a green hydrogen storage system into a
microgrid located on the island of Crete. Along with
the hydrogen system, its energy system uses RES, a
diesel generator, and imported energy from the grid.
The integration is designed to be profitable under
specific assumptions, minimizing imported energy
in a viable manner.
2 Literature Survey
2.1 Microgrid Energy Systems
Microgrids consist of small-scale energy generation
systems and have distinct energy load profiles.
Typically, they are low or medium-voltage
distribution grids that rely on a combination of
conventional fuel-consuming generators and RES.
The reliability of energy generation can be enhanced
by installing energy storage systems, which help
address the irregular power output from
photovoltaic (PV) and wind turbine (WT) systems,
[1], [2]. Several studies have focused on optimizing
energy systems at the local level. For instance, a
comprehensive overview of recent advancements,
methodologies, and future research directions in this
field has been compiled, [3]. A multi-objective
optimization model that minimizes energy
consumption while supporting economic growth
was also developed [4]. Similarly, a multi-objective
optimization model for integrated energy systems,
aiming to achieve both economic and environmental
benefits through reduced carbon emissions has been
implemented, [5]. To address the challenge of the
intermittency of resources like wind and solar
power, the optimization of RES was investigated,
[6]. The proposed solution involves a strategic
combination of diverse RES types and the
integration of energy storage systems. The
methodology employs a multi-pronged approach,
thoroughly analyzing existing literature on optimal
RES deployment.
2.2 Hydrogen Power and Storage Systems
In many cases, the optimal choice of an energy
system, due to the stochasticity of RES plants
combined with their dependence on climatic
conditions and meteorological phenomena, is the
hybrid energy system with a combination of at least
one form of RES and storage with batteries and
even diesel generators, [7]. Despite their benefits,
microgrids present significant challenges, such as
their isolation, the uncertain variability of RES
plants, the stability of the electricity grid, and their
economic and technical adequacy. Hydrogen
production and storage as an energy carrier is a
promising economic solution, especially in
combination with RES infrastructure such as WT
and PV farms. Several techniques for the production
of 'green hydrogen' such as alkaline electrolysis
(AEL), proton exchange membrane electrolysis
(PEMEL), and anion exchange membrane
electrolysis (AEMEL) are proposed in the literature.
Embedding any of the techniques in combination
with fuel cells as an alternative electricity generator
offers a viable prospect for improving the stability
and independence of microgrids.
A critical review of hydrogen storage systems
focusing on the feasibility of this technology is
provided while emphasizing the necessity to reduce
costs to be commercially competitive, [8]. It also
highlights the importance of hybrid systems
combining hydrogen with short-term energy storage
technologies and discusses the challenges related to
low energy efficiency and high costs. The potential
for economies-of-scale effects to reduce costs in the
future is mentioned, but uncertainty prevails
regarding their commercial attractiveness. The
discussion of Japan's challenge with fossil fuel
dependence after the earthquake and the proposal to
develop and utilize renewable energy sources,
underscoring the vulnerability of renewable energies
and the proposed solution of hybridization with a
storage system is summarized, [9]. The recent
advances in hydrogen technology, including its
application in transportation, industry, and power
generation, as well as the challenges, barriers, and
recommendations for the development of hydrogen
technology and environmentally friendly smart
energy systems in Vietnam are discussed, [10].
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Marios Nikologiannis, Ioannis Mozakis,
Ioannis Iliadis, Yiannis Katsigiannis
E-ISSN: 2224-350X
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Energy management in a microgrid encompasses
a sophisticated computerized framework targeted
primarily at providing optimized resource planning,
[11]. It uses modern computer technology to boost
the operation of distributed energy sources and
energy storage systems, [12].
This paper aims to optimize the sizing of a
microgrid's RES and hydrogen system to achieve
independence and profitability. Unlike other
publications, this study employs a detailed
simulation algorithm that performs hourly
calculations of storage state of charge and power
allocation. The algorithms are designed to be
flexible, allowing for the customization of installed
capacities and overall system properties, such as
generator lower and upper limits, interconnection
capacity, prices, etc. This adaptability enables a
financial evaluation of specific systems based on
distinct energy profiles and photovoltaic production.
3 Methodology
The proposed installation entails the incorporation
of RES production, comprising photovoltaic (PV)
installations, a pre-installed diesel generator system,
and the implementation of a hydrogen system. The
methodology is structured to accommodate input
data related to the system’s operation, including
annual load hourly data ranging up to a few hundred
kW, normalized hourly data from a solar farm on
the island of Crete, and parameters related to the
operation and costs of each component's installment
and operation.
The microgrid’s design prioritizes the system’s
independence from the main grid to which it is
connected. Both in load satisfaction and handling of
power produced locally by RES, the local
production strives to maintain the majority of power
contribution to the system’s demand and its
financial profitability, while the connection to the
grid serves as a reserve or complimentary source of
income. The microgrid’s independence relies on the
usage of solar panels, fuel-consuming generators,
and a hydrogen-based storage system coupled with a
fuel cell subsystem. The microgrid’s design is
shown in Figure 1.
For the study, the proposed energy demand
response sequence takes into account the following
stages:
The sequence commences by activating the
minimum essential load from conventional units.
This ensures stable operation while minimizing
reliance on conventional fuels. Following minimum
conventional generation, available energy from RES
that is produced locally is utilized to directly supply
the grid. If real-time RES production is insufficient
to meet the remaining demand, the strategy
incorporates the use of stored energy.
The energy system aims to capture the remainder
of RES production and store it in a tank in the form
of compressed hydrogen gas. The conversion is
realized through the electrolysis of water, powered
by the energy to be stored. The purpose of the
proposed storage method is to be used to address the
deficiency of the RES system in case of reduced
weather potential through the conversion of the
compressed gas into electricity with the use of a fuel
cell system integrated into the overall hydrogen
subsystem. However, the combined contribution of
RES-hydrogen coupling may not suffice for the
hourly electricity demand. In such a case, the diesel
generator subsystem’s operation can be
proportionally increased up to its maximum
technical limits or until the hourly load is satisfied.
If all previous measures are inadequate to meet
demand, controlled electricity import stemming
from the external grid can be implemented as a last
resort. The specified priority chain is summarized in
Figure 2.
Fig. 1: Illustration of the microgrid’s design
Fig. 2: Load satisfaction’s hourly priority design
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Marios Nikologiannis, Ioannis Mozakis,
Ioannis Iliadis, Yiannis Katsigiannis
E-ISSN: 2224-350X
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An alternative process chain is activated to
capitalize on the excess RES production, in case of
demand satisfaction from the generator system’s
lower limit and current hourly RES energy. First,
any surplus is prioritized for conversion into
hydrogen and storage in available hydrogen tanks,
adopting the efficiency of the electrolysis process
equal to 60%, [13]. After excluding the electrolyzed
energy and accounting for the associated losses, the
remaining available energy is allocated for export to
the main grid. This export is limited to 200kW, as a
hypothetical limit determined by the supplier and
microgrid representatives, and adheres to technical
limitations to ensure grid stability. If a surplus of
RES energy remains even after storage and export,
the design proposes its sale through hydrogen
production, mainly for industrial use, up to the
electrolysis system’s remaining availability of the
total capacity. The remainder of the production is
rejected from the system. The specific power flow
produced by RES is depicted in Figure 3.
Fig. 3: Power flow of RES hourly production
For this particular analysis, the annual demand
and production are assumed to remain constant,
leading to consistent annual cashflows, except for
the replacement cost of the electrolysis and fuel cell
subsystems in the 10th year. The hourly simulation
of the energy system is conducted using the
flowcharts outlined below.
Direct RES is the RES hourly production
contributing directly to load satisfaction, calculated
in Figure 4 (Appendix).
The computation of the storage subsystem’s state
of charge is divided into separate flowcharts, Figure
5 and Figure 6 in Appendix, describing the instances
of charge and discharge respectively.
If the stored quantity of compressed gas is
sufficient, the energy produced by the fuel cell
subsystem in each hour of the simulation is
described in Figure 7 (Appendix).
The quantity of excess energy effectively stored
in the hydrogen tank, after losses, for every hour is
computed in Figure 8 (Appendix).
The total hourly contribution of the diesel
generator system for each hour T (TOTAL CONV.)
is calculated in Figure 9 (Appendix).
The import of energy required to satisfy the
remaining demand is calculated in Figure 10
(Appendix).
The amount of excess energy sold to the national
grid shall be determined by the processes in Figure
11 and Figure 12 in Appendix.
If, by the end of the electrolysis storage stage,
the electrolyzed energy has not reached the
subsystem’s nominal value, the remaining energy
after export allocation is used to produce green
hydrogen for industrial sector trade, contributing to
the system's profitability. The produced amount is
calculated in Figure 13 (Appendix).
To estimate the relevant income, the hydrogen
mass (in kg) produced during the process of Figure
13 (Appendix) was calculated using the lower
heating value of hydrogen (LHV H2) equal to
33.33kWh/kg. The produced hydrogen mass to be
compressed for sale is calculated:
MassH2=Electricity used*Electrol. Eff.
LHV H2 (1)
Due to the limited efficiency of the hydrogen
system's components, some energy is lost during
allocation to and from these components, mainly
due to heat conversions. These losses are accounted
for by following the process outlined in the chart
shown in Figure 14 (Appendix).
The estimated rejected the power of the system
for each hour of operation is achieved through the
flowchart described in Figure 15 (Appendix).
To approximate the amount of diesel fuel
required for the operation of the conventional
system, [14] was referred to, utilizing the value of
34% efficiency for all hours for simplicity.
All relevant costs and prices necessary for
calculating the NPV are compiled in Table 1. Most
prices correspond to contemporary market data;
thus, the methodology can yield results suitable for
decision-making applied to the current market
structure. The interconnection price is equal to the
agreed-upon price for both the imported power to
the microgrid and the exported power to the grid,
stemming from local RES production. Since the
specific scenario under investigation concerns the
location of Crete, the hydrogen selling price was
calibrated to be equal to the optimal price for a
hypothetical hydrogen production facility situated
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on the island of Crete, per the study examined in
[15].
Table 1. Types of investment costs
Type of expense
Cost
Interconnection price
0.18 EUR/kWh
Hydrogen gas price
3.5 EUR/kg
H2 Tank Installation Cost
6.0 EUR/kWh
PV Installation Cost
600.0 EUR/kW
WT Installation Cost
1,000 EUR/kW
Electrolyzer Installation
Cost
1,500 EUR/kW
Fuel Cell Installation Cost
1,500 EUR/kW
Compressor Installation
Cost
50.0 EUR/kW
Inverter Installation Cost
100.0 EUR/kW
RES O&M cost rate
5%
Total O&M cost rate
2%
Diesel Price
2.00 EUR/lt
Annual Discount Rate
3.0%
The total lifetime of the investment is 20 years,
equal to the estimated lifetime of the PV
installation. The durability of both the electrolyzer
and the fuel cell subsystems is considered equal to
10 years. For the specific simulation, the decision
variables are the PV installed capacity (in kW) and
the hydrogen tank’s storage capacity (in kWh), since
the electrolyzer and fuel cell’s capacity were
calibrated equal to the PV capacity, to achieve
theoretically total RES utilization. The diesel
generator’s lower limit was set to the minimum
value of the load time series, while the upper limit
was 20% higher than the lower, permitting ample
RES penetration to the energy mix.
The NPV was calculated using:
NPV= ∑Cashflows(t)
(1+r)t
L
t=0 -CAPEX (2)
Where L is the investment’s lifetime,
Cashflows(t) represent the income and expenses of
the business during the year t, and CAPEX is the
initial expenditure.
The CAPEX includes the expenses for the PV
installation and its inverter, along with the hydrogen
subsystem. These costs encompass the installation
of the water electrolysis system at its nominal
capacity, the fuel cell system at its nominal power,
the hydrogen storage compressor, the tank’s total
energy capacity, and the inverter connected to the
fuel cell for current conversion.
The total income generated by the proposed
installation is calculated as the sum of the products
of the exported energy quantity and hydrogen mass
(in metric tonnes) by their respective prices. On the
other hand, negative cash flows encompass
expenses such as grid import costs, diesel costs for
conventional system operation, total operational and
maintenance expenses of the RES system (estimated
as an annual percentage of the installation cost), and
likewise, operational and maintenance costs of the
hydrogen system.
For the calculation of the NPV, the discount rate
for the calculation of the future income in present
value is crucial. In the specific scenario, its value is
assumed to be equal to 3%.
4 Results
For a wide range of the two decision variables, the
graph of NPV values is drawn, depicted in Figure
16.
Fig. 16: NPV with respect to PV power and
Hydrogen tank storage
Negative NPV values imply net loss for the
investment, while positive values exhibit profit for
the period of the investment. The NPV does not
converge to a specific value, due to the assumption
that the microgrid can sell the entirety of each
hour’s industrial hydrogen production. In this
context, the optimal solution is the set of
independent variables that yield the maximum NPV,
with minimal CAPEX and at least 90% annual self-
sufficiency. The approach employed was brute
force, commencing from values resulting in nearly
zero NPV, persisting until the criteria were met and
the maximum NPV was attained. The identified set
is 3100kW of PV installed power and 1500 kWh
hydrogen tank capacity.
The annual energy mix determined by the
solution is shown in Figure 17.
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E-ISSN: 2224-350X
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Volume 19, 2024
Fig. 17: Load satisfaction’s hourly priority design
A little less than half of the total energy arises
from the diesel generator system, meaning a heavy
dependence on the specific technology and a
considerable impact of diesel price fluctuations on
the microgrid’s logistics. As required, the imports
are limited to 10% of load satisfaction, while the
fuel cell increases RES penetration by 10.32%. The
daily energy mix for an entire simulated year is
shown in Figure 18.
Fig. 18: Load daily mix
For the specific energy profile, the vast majority
of imports are met during the summer period when
the load demand is at its peak and local production
is insufficient to cover it.
In Figure 19, the annual RES production and its
allocation are depicted.
Fig. 19: Annual microgrid’s RES production
The vast majority of the produced energy is
converted to hydrogen for sale, explaining the high
value of NPV. The rejections of the system are zero,
attributed to the costly, yet profitable high installed
capacity of the electrolysis subsystem. The above
can be observed on a daily scale in Figure 20.
Fig. 20: Load satisfaction’s hourly priority design
The RES production reaches its peak during the
summer, characterized by minimal day-to-day
variations. In contrast, the winter months exhibit
substantial daily fluctuations in total RES
production. This is unlike the energy mix shown in
Figure 18, where all contributors display more
consistent output patterns.
The resulting CAPEX is calculated equal to
12,037,150.00 EUR. In Figure 21, the CAPEX
attributed to RES and the hydrogen system is
depicted.
Fig. 21: CAPEX breakdown
The vast majority of expenses concern the
hydrogen system, the main obstacle in hydrogen-
based energy investments. At the same time, the
hydrogen system is the main contributor to the
microgrid’s income, while the fuel purchases are the
costliest annual expense, as can be seen in Figure
22.
The NPV is equal to 2,489,862,897.40 EUR, a
substantial value attributed to the assumption that
the entirety of the hydrogen produced for sale to the
industrial sector can be sold. A more realistic
simulation, reserved for future endeavors, should
include additional constraints regarding the market’s
demand and general status regarding hydrogen
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DOI: 10.37394/232016.2024.19.27
Marios Nikologiannis, Ioannis Mozakis,
Ioannis Iliadis, Yiannis Katsigiannis
E-ISSN: 2224-350X
312
Volume 19, 2024
transactions. The market’s landscape regarding
taxation upon produced hydrogen, current demand,
and competitive prices would make such a
simulation more realistic by limiting the traded
hydrogen gas and introducing another layer to the
optimization problem.
Fig. 22: Annual cashflows
5 Conclusion
This paper investigates a proposed business strategy
aimed at attaining self-sufficiency in meeting the
energy demands of a microgrid. The suggested
enhancements to an existing energy system, initially
reliant solely on a diesel generator, involve
integrating RES through photovoltaic technology
and implementing energy storage using green
hydrogen produced via electrolysis. This hydrogen
can be utilized both as a commodity and as fuel for
additional electricity generation. The evaluation of
this scheme's financial viability employs the NPV
metric. The methodology successfully identifies
decision variables within the model regarding the
sizing of the RES and hydrogen subsystems to be
installed. The solution results in a positive NPV of
2,489,862,897.40 EUR over 20 years. It achieves
90% self-sufficiency and a 41.36% contribution
from RES, optimizing the utilization rate of the PV
system and significantly reducing diesel costs.
Consequently, this leads to a substantial increase in
the estimated profits. The findings of the
methodology should be interpreted considering the
assumptions of unlimited hydrogen demand and the
absence of restrictive policies that could impose
taxation schemes or limitations on the production of
hydrogen gas.
Declaration of Generative AI and AI-assisted
Technologies in the Writing Process
During the preparation of this work the authors used
Grammarly in order to improve the clarity of text
and minimize grammatical errors. After using this
tool/service, the authors reviewed and edited the
content as needed and take full responsibility for the
content of the publication.
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Contribution of Individual Authors to the
Creation of a Scientific Article (Ghostwriting
Policy)
The authors equally contributed to the present
research, at all stages from the formulation of the
problem to the final findings and solution.
Sources of Funding for Research Presented in a
Scientific Article or Scientific Article Itself
This work received financial support from the
project “Enhancing resilience of Cretan power
system using distributed energy resources
(CResDER)” (Proposal ID: 03698) financed by the
Hellenic Foundation for Research and Innovation
(H.F.R.I.) under the Action “2nd Call for H.F.R.I.
Research Projects to support Faculty Members and
Researchers”.
Conflict of Interest
The authors have no conflicts of interest to declare.
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WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2024.19.27
Marios Nikologiannis, Ioannis Mozakis,
Ioannis Iliadis, Yiannis Katsigiannis
E-ISSN: 2224-350X
314
Volume 19, 2024
APPENDIX
Fig. 4: Direct RES calculation
Fig. 5: Hydrogen tank’s charge level after discharge activation
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2024.19.27
Marios Nikologiannis, Ioannis Mozakis,
Ioannis Iliadis, Yiannis Katsigiannis
E-ISSN: 2224-350X
315
Volume 19, 2024
Fig. 6: Hydrogen storage state of charge after electrolysis process
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2024.19.27
Marios Nikologiannis, Ioannis Mozakis,
Ioannis Iliadis, Yiannis Katsigiannis
E-ISSN: 2224-350X
316
Volume 19, 2024
Fig. 7: Fuel Cell’s contribution for each hour T
Fig. 8: Hourly Electrolysis production
Fig. 9: Conventional system’s hourly contribution
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2024.19.27
Marios Nikologiannis, Ioannis Mozakis,
Ioannis Iliadis, Yiannis Katsigiannis
E-ISSN: 2224-350X
317
Volume 19, 2024
Fig. 10: Imports from the grid
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2024.19.27
Marios Nikologiannis, Ioannis Mozakis,
Ioannis Iliadis, Yiannis Katsigiannis
E-ISSN: 2224-350X
318
Volume 19, 2024
Fig. 11: Power exported to the grid (part 1)
Fig. 12: Power exported to the grid (part 2)
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2024.19.27
Marios Nikologiannis, Ioannis Mozakis,
Ioannis Iliadis, Yiannis Katsigiannis
E-ISSN: 2224-350X
319
Volume 19, 2024
Fig. 13: Industrial hydrogen produced in energy units
Fig. 14: Hourly microgrid’s losses
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2024.19.27
Marios Nikologiannis, Ioannis Mozakis,
Ioannis Iliadis, Yiannis Katsigiannis
E-ISSN: 2224-350X
320
Volume 19, 2024
Fig. 15: Hourly rejections of the system
WSEAS TRANSACTIONS on POWER SYSTEMS
DOI: 10.37394/232016.2024.19.27
Marios Nikologiannis, Ioannis Mozakis,
Ioannis Iliadis, Yiannis Katsigiannis
E-ISSN: 2224-350X
321
Volume 19, 2024
