Highlights

• Kyiv has considerable potent solar and wind energy for green hydrogen production.
• HOMER evaluates the techno-economic feasibility of a hybrid HydESS for renewables.
• The lowest LCOE is 0.245 $ kWh⁻¹ from the Wind-HydESS-BESS hybrid system.
• The HydESS system consists of a 250-kW PEM fuel cell and a 250-kW electrolyzer.
• An additional benefit of HydESS is a reduction of CO₂ to 4,132 tons for 25 yrs.
• The lifetime sensitivity of proton exchange membrane fuel cells is reduced, but the on-off time of 600 seconds is anticipated to be more severe.

1. Introduction

2. Methodology

2.1. Research framework & Flow

Figure 1. Schematices of Technoeconomic analysis using HOMER platform.

Figure 1. Schematices of Technoeconomic analysis using HOMER platform.

To analyzing the techno-economic research for hydrogen society, many approaches were applicated to quantification for hydrogen technologies. NREL invented the software HOMER for public research. It provides accurate climate data from the satellite in the specific region. The foremost advantage of the tool was the proposal of an optimized energy system via techno-economic analysis. The techno-economic study was carried out using HOMER to examine PEMWE’s LCOH for renewable energy-linked operation as well as LCOH change relied on system unit costs.

2.2. Literature Review

The carbon emission of thermal plants (Diesel power plant), including systems, exclude the plant in the literature survey. In any case, the benefit is mainly GHGs reduction, which is unsuitable energy storage compared to this work. The location of renewable energy generation site was limited to land and onshore due to the city. Offshore wind or floating PV were possible to transfer electricity, but the additional infrastructure cost could be added. There are many literature reviews including “Homer”, “hydrogen”, “Fuel cell” “electrolyzer”, “PV”, and “wind” in previous bibliometric analysis. By Scopus, total19 literatures were listed and then excluded the system containing diesel plant, and the finalized as six papers (17-22) are tabulated in Table 2.

Table 1. Summary of publications conducting the technoeconomic analysis of energy storage systems including hydrogen using HOMER.

Table 1. Summary of publications conducting the technoeconomic analysis of energy storage systems including hydrogen using HOMER.

Ref	Item	COE	NPC	PV	Wind	BESS	PEMWE	PEMFC	H2 tank	Region	AC load or Hydrogen demand
	Objective	$ kWh−1	$	kW	kW	kW	kW	kW	kg		kWh day−1 kgH2 day−1
[17]	BESS vs. HydESS comparison	1.208	75,428	4	2	0	3	2	1	Saudi Arabia	14 kWh day−1
[18]	BESS vs. HydESS comparison	0.52	7,160,000	469	1500	396	350	100	500	USA	70 kgH2 day−1
[19]	HydESS feasibility	0.8399	1,006,293	120	-	-	60	13	20	Spain	200 kWh day−1
[20]	HydESS case study	1.901	910,415	1	1	-	150	1	100	Oman	12 kWh day−1
[21]	PV vs. Wind comparison	0.374	2,990,000	69	88	581	250	450	700	Canada	125 kgH2 day−1
[22]	PV vs. Wind comparison	0.366	5,276,069	900	700	1088	300-kW	100	300	Korea	2187.6 kWh day−1
This work	BESS vs. HydESS comparison	0.245	4,508,672	0	1,000	441	250	250	700	Ukraine	3,900 kWh day−1

Al-Sharafi et al. [17] evaluated the economic factor, LCOE as 1.208 $ kWh⁻¹ in Abha area for the hydrogen production storage system, In the reference, the result of System #6 exhibits the minimum LCOE with 1.208 $ kWh⁻¹ and LCOH is 43.3 $ kg⁻¹. The optimum configuration has 4 kW PV array, two wind turbines, 2 kW converter, 2 kW fuel cell, 3 kW electrolyzer and 1 kg hydrogen tank. Another case by Abdin et al. [18] calculates the minimum COE as 0.5 $ kWh⁻¹ for Golden Colorado equipped with 400 kg H₂ tank. Peláez-Peláez et al. [19] simulated the LOCE as 0.8399 $ kWh⁻¹ containing 20kg tank with PV coupled electrolyzer and fuel cell. Okonkwo et al. [20] conceptualized the system as PV, wind, fuel cell and hydrogen tank with LCOE, 1.901 $ kWh⁻¹ in Oman and the hydrogen storage capacity was set to 100 kg tank. Babaei et al. [21] acquired LCOE 0.374 $ kWh⁻¹ with the hydrogen based microgrid composed with PV, wind, fuel cell, hydrogen tank, and batteries in Saint Pierre Island caseRecently, Zhang et al. [22] optimized the off-grid hybrid energy system in Ui island. The system was composed of 990-kW PV panels, 700-kW wind turbines, a 1088-kWh Li-ion battery bank, 534-kW converter, 300-kW PEMWE system, 300-kg hydrogen tank, and 100-kW PEMFC. The total NPC of the system is $5,276,069, and the LCOE is 0.366 $ kWh⁻¹. This case study proved that the self-sufficient energy system in isolated area for community demand without any auxillary power supply, and the hypotheses of the simulation results are limited by the low capacity factor of electrolyser. And the system showed the good feasibility compared to diesel plant, but the fuel cell was adopted as PEM type with 40,000 lifetime span. Moreover, the Battery cost is increased within a few years up to 596 $ kWh [23].

2.3. System and site outline

In this study, the optimum specifications of water electrolysis capacity and other ancillary devices were derived based on the system’s actual operation results, including the 1,000 kW-class wind turbine power generation. As simulation results, the NPC and the levelized cost of electricity (LCOE) were calculated. The optimized system result is resulted in Figure 2 from system (a) to system (c). The difference between system (a) and (b) is photovoltaic panel and the difference between (a, b) and (c) is HydESS usage. The most optimized system is (a), and it will be discussed in result and discussion section.

Figure 2. Basic hybrid hydrogen energy storage system (HydESS) and battery energy storage system(BESS) configuration with renewable energy sources, PV, wind turbine.

Figure 2. Basic hybrid hydrogen energy storage system (HydESS) and battery energy storage system(BESS) configuration with renewable energy sources, PV, wind turbine.

Figure 3. Location of Igor Sikorsky Kyiv polytechnic institute in Kyiv, Ukraine (50°40.0’N, 30°59.5’E), (a) load view, (b) arial view, and (c) Igor Sikorsky Kyiv polytechnic institute building.

Figure 3. Location of Igor Sikorsky Kyiv polytechnic institute in Kyiv, Ukraine (50°40.0’N, 30°59.5’E), (a) load view, (b) arial view, and (c) Igor Sikorsky Kyiv polytechnic institute building.

The capital city of Ukraine, Kyiv (50°40.0’N, 30°59.5’E) is studied as the subject of the analysis in Figure 4. This study limited on local area point is technoeconomic comparison between HydESS and BESS for renewable energy storage in Kyiv, capital of Ukraine, as center of culture and economy. The NASA satellite data was used to obtain statistics on average solar radiation and wind speed during a one-year period. According to Figure 4a, the yearly average solar radiation on Kyiv is 3.10 kWh m⁻²day⁻¹. Additionally, clearness nearly cloudy independent on the season, from 0.367 in November and 0.496 in Aug. Referring to Figure 4b, the average wind speed was around 6.20 m s⁻¹ when the wind turbine was erected at the height of 65 m above sea level. Temperature is coldest in January as −6.14 ℃ and hottest as 20.83 ℃ in July as shown in Figure 4c.

Figure 4. Climate profile of Kyiv, (a) daily solar radiation and clearness index per month, (b) wind speed, and (c) temperature of Kyiv, Igor Sikorsky Kyiv Polytechnic Institute location in Ukraine.

Figure 4. Climate profile of Kyiv, (a) daily solar radiation and clearness index per month, (b) wind speed, and (c) temperature of Kyiv, Igor Sikorsky Kyiv Polytechnic Institute location in Ukraine.

Figure 5. AC Primary load profiles of Kyiv, (a) daily, (b) monthly, and (c) yearly of Kyiv, Igor Sikorsky Kyiv Polytechnic Institute location in Ukraine.

Figure 5. AC Primary load profiles of Kyiv, (a) daily, (b) monthly, and (c) yearly of Kyiv, Igor Sikorsky Kyiv Polytechnic Institute location in Ukraine.

Power demand was set as a residence load provided as a sample case from HOMER to select the AC (alternating current) electric load scale size. As shown in Figure 4, the total daily load of 3,900 kWh day⁻¹, and the maximum peak load is 482.3 kW and load factor is 0.34. This AC load is calculated from the average electricity consumption per capita data and capacity of dormitory building . Average power (electricity) consumption per capita in Ukraine is 2,844 kWh year⁻¹ , 7.8 kWh⁻¹ according to world data [24]. Recently opened dormitory in Igor Sikorsky Kyiv Polytechnic Institute about 500 students and staffs are capable to residence in 2021 [25].

Table 3. Energy storage system components cost, technical data, and lifetime.

Table 3. Energy storage system components cost, technical data, and lifetime.

System data
PV Unit
Capital expenditure	1252	$ kW−1
Operation and maintenance expenditure	18	$ y−1 kW−1
Lifetime	25	years
Derating factor	85	%
Wind turbine system
Capital expenditure	1500	$ kW−1
Operation and maintenance expenditure	50	$ y−1 kW−1
Lifetime	25	years
Batteries (100 kWh Li BESS)
Nominal voltage	480	V
Nominal catacity	90.7	kWh
Maximum capacity	189	Ah
Captial expenditure	415	$ kWh−1
Replacement expenditure	280	$ kWh−1
Operation and maintenance expenditure	25	$ y−1 kWh−1
Lifetime	10	years
Converter
Capital expenditure	90	$ kW−1
Replacement c expenditure	90	$ kW−1
Operation and maintenance expenditure	0	$ y−1
Lifetime	15	years
Efficiency	95	%
Electrolyzer
Capital expenditure	1400	$ kW−1
Replacement expenditure	650	$ kW−1
Operation and maintenance expenditure	60	$ y−1
Lifetime	25	years
Storage tank (High pressure)
Capital expenditure	635	$ kg−1
Operation and maintenance expenditure	3	$ y−1
Lifetime	25	years
Fuel cell
Capital expenditure	4800	$ kW−1
Replacement expenditure	3800	$ kW−1
Operation and maintenance expenditure		$ y−1
Lifetime	5	years

The cost information of system components is listed in Table 2. The cost of new PV is estimated as $ 1,252 kW⁻¹ and the annual OPEX is estimated as18 $ kW⁻¹ from the reference [26]. The panel lifetime is expected to be 25 years and the derating factor is set to 85%. The wind turbine is the Leitwind LTW77 1,000 kW model used in the existing literature, and the cut in speed is around 11~12 m s⁻¹ [27]. It can be seen from Figure 6; the manufacturer provided the wind turbine’s power curve and the capital expenditure (CAPEX) is $ 1,500 kW⁻¹. The operation and maintenance expenditure (OPEX) cost is annually $ 50 kW⁻¹ and the total lifetime is 25 years.

Figure 6. Wind turbine (a) Leitwind AG / Leitwind LTW77 / 1000 kW wind turbine generator / Melfi, Italy (maker‘s web site), (b) Power curve of wind turbine LWT77 from Leitwind 1,000 kW model.

Figure 6. Wind turbine (a) Leitwind AG / Leitwind LTW77 / 1000 kW wind turbine generator / Melfi, Italy (maker‘s web site), (b) Power curve of wind turbine LWT77 from Leitwind 1,000 kW model.

BESS adopted the Li ion battery such as LG Energy Solution, the 10-kWh class model [23]. The nominal voltage and capacity are 48 V and 9.8 kWh and the maximum capacity is 189 Ah. CAPEX is $ 596 kWh⁻¹ [28] and replacement expenditure is $ 280 kWh⁻¹, O&M cost is $ 23.3 kWh⁻¹ [29]. The battery lifespan is 10 years [30]. The CAPEX of converter is $ 80 kW⁻¹ form NREL’s report for grid energy storage technology cost [29]. The efficiency is 95% and the lifetime of converter is expected to 15 years. The converter system and installation cost is estimated as 90 $ kW⁻¹ and the replacement cost is identical to CAPEX. Operation and mainternance cost of the converter is 0 in practically according to other research [31].

The water electrolyzer is adopted as PEM type in this study, easily operable compared to other electrolysis, counting on the relatively high capital expenditure as 1,400 $ kW⁻¹ [32] and the OPEX is estimated as 2% of CAPEX [33]. Solid oxide fuel cell (SOFC) is chosen for its highest efficiency and adaptability for stationary applications. The specific power generation is 27.52 kWh kg⁻¹H_2, if the voltage efficiency of SOFC is 79.3% from the reference [34]. And the specific fuel consumption is calculated in HOMER following the procedure [35]. The capital cost and maintenance expenditures become more higher c.a. 4,800 $ kW⁻¹ [36,37] than that of PEM fuel cell, 3,300 $ kW⁻¹ [22]. The capital and maintenance cost of Hydrogen tank is referenced by NREL’s previous report [38]. Life time span of SOFC is based on the literature as 40,000 hrs [39,40] and expected optimum value as 50,000 hrs [41].

3. Results and Discussion

3.1. Optimized system configuration

According to Table 4, the NPC for the optimized system is $4,584,704, and the LCOE is 0.245 $ kWh⁻¹ (Figure 7a). Without PV, the full system consists of WT, HydESS, and BESS. Additionally, PEMFC fuel cells with a lifespan of 50,000 hours have been programmed into the system. Due to the low PV power of the system in Figure 7b, the LCOE and NPC are very similar to those in Figure 7a.

Table 4. Simulated optimization system with different fuel cell type as proton exchange membrane fuel cell and solid oxide fuel cell and different life time.

Table 4. Simulated optimization system with different fuel cell type as proton exchange membrane fuel cell and solid oxide fuel cell and different life time.

Case	FC type	Lifetime	Levelized cost of energy (LCOE)	Total net present cost (NPC)	PV	Wind turbine	FC	Li-ion battery	Converter	PEMWE
Units	-	hrs	$/kWh−1	$	kW	kW	kW	kWh	kW	kW
(a) HydESS-1	PEMFC	40,000	0.249	4,584704	0	1,000	250	499.8	474	250
	PEMFC	50,000	0.245	4,508,672	0	1,000	250	441	464	250
	SOFC	40,000	0.369	6,794770	0	1000	250	2,274	632	250
	SOFC	50,000	0.289	5,316,831	0	1,000	250	911	481	250
(b) HydESS-2	PEMFC	40,000	0.250	4,591,366	1	1000	250	509.6	466	250
	PEMFC	50,000	0.246	4,526,294	2	1,000	250	450.8	524	250
	SOFC	40,000	0.348	6406074	140	1000	250	1,744	500	250
	SOFC	50,000	0.282	5,179,203	10	1,000	250	755	573	250
(c) BESS	none	-	0.516	9,483,948	518	2,000	-	3,959.2	677	-

Figure 7. System configurations, target configuration consist of hybrid ESS with BESS and HydESS, (a) optimized system with WT-HydESS-BESS (b) second optimized system with PV-WT-HydESS-BESS, and (c) comparison configuration including BESS.

Figure 7. System configurations, target configuration consist of hybrid ESS with BESS and HydESS, (a) optimized system with WT-HydESS-BESS (b) second optimized system with PV-WT-HydESS-BESS, and (c) comparison configuration including BESS.

On the other hand, the presence or absence of PV has a greater effect on the LCOE difference when using SOFC than when using PEMFC. A system with 140 kW of PV was calculated to be the most cost-effective over a 40,000-hour lifetime at 0.348 $ kWh⁻¹ versus a 0.369 $ kWh⁻¹ in without PV system.

Only the BESS system without HydESS, as shown in Figure 7c, has the highest LCOE of 0.516 $ kWh1 and NPC of 9,483,948 $. The renewable energy sources, which include PV and WT, have been optimized to the maximum size of 518 kW PV and 2,000 kW WT. Furthermore, the Li ion BESS has the largest capacity of 3,959 kW. Too large a Li ESS usually causes thermal runaway and fire problems, so minimizing risk is critical when installing and operating BESS [49].

3.2. Electricity production

The total electricity produced by system configuration (a), lowest LCOE, 0.245 $ kWh⁻¹ is 3,895,029 kWh yr⁻¹ with 9.25% of PEMFC and 90.8% WT plant as shown in Figure 8a. At the point of excess electricity, the excess fraction is 45.0% of total production, as 1,754,632 kWh yr⁻¹. The PEMFC with 50,000 hrs lifetime shows 189 kW mean electrical output. And the hydrogen production is 13,349 kg per year and the 12,751 kg hydrogen is supplied to fuel cell. The electrolyzer exhibits the mean output as 75.1 kW with capacity factor 30.1 % equal to 3,612 hrs operation per year.

Figure 8. Electricity production from optimized system HydESS-BESS and BESS adopting PEMFC and 50,000 hrs life time, (a) Monthly production profile with WT-HydESS-BESS, (b) hourly production profile with WT-HydESS-BESS, (c) monthly profile with with PV-WT-HydESS-BESS, and (d) hourly production profile with PV-WT-HydESS-BESS, (e) Monthly production profile with BESS, and (f) hourly production profile with PV-WT-BESS.

Figure 8. Electricity production from optimized system HydESS-BESS and BESS adopting PEMFC and 50,000 hrs life time, (a) Monthly production profile with WT-HydESS-BESS, (b) hourly production profile with WT-HydESS-BESS, (c) monthly profile with with PV-WT-HydESS-BESS, and (d) hourly production profile with PV-WT-HydESS-BESS, (e) Monthly production profile with BESS, and (f) hourly production profile with PV-WT-BESS.

Secondly optimized system as shown in Figure 7b, the PV generates 0.04% electricity, and FC takes 9.18% and WT produces 90.8% electricity as total 3,893,588 kWh yr⁻¹. And the excess electricity 1,758,397 kWh yr⁻¹ is equal to 45.2% of total electricity production.

In contrast, the BESS system in Figure 7c generates electricity with 8.14% PV power and 91.9% WT power for a total of 7,418,136 kWh yr⁻¹ as displayed in Figure 8 c and d. The excess electricity of 5,960,755 kWh yr⁻¹ (80.4% of total electricity generation) is roughly 3.4 times that of HydESS, implying that the system’s rated power is over-specified.

Figure 8 depicts a monthly profile of production, showing that higher wind speeds in January and March result in greater output compared to June and July. The pattern is identical in all system configurations such as a, b, and c because wind power accounts for 90% of total production.

Table 5. Electrolyzer operation results.

Table 5. Electrolyzer operation results.

Quantity	Case 1 WT-HydESS-BESS	Case 2 PV-WT-HydESS-BESS	Units
Rated capacity	250	250	kW
Mean input	75.1	74.6	kW
Total input energy	658,185	653,062	kWh yr−1
Capacity Factor	30.1	29.8	%
Hours of operation	3,612	3,657	hr yr−1

3.3. Operation strategy

Figure 9. Day operation profiles for the cycle charging dispatch strategy with WT-HydESS-BESS system.

Figure 9. Day operation profiles for the cycle charging dispatch strategy with WT-HydESS-BESS system.

The most optimized result is adapted the charge cycling (CC) mode rather than load following (LF) mode. The CC mode, power generator is always operated to meet the primary AC load in priority, and then the excess power is dispatched in electrolyzer, battery, and flywheel etc. Therefore, the maximum output power of generator is set to meet the average AC load on demand side.

As shown in Figure 8, the AC load requirement increases during day 1 from 240 hr to 264 hr, but the WT power supply is insufficient. Same operation pattern is observed in 264 hr to 288 hr in day 2. The fuel cell will then begin to produce insufficient electricity for the residence. The electrolyzer, on the other hand, typically operated at night and early morning with excess WT power to produce hydrogen for fuel cell operation. The daily profile of hydrogen production and utilization demonstrates a suitable ESS system for variable wind energy.

3.4. CO₂ Emissions

From an economic perspective, this can be elucidated as a significant cost reduction, taking into account the prevailing European market value of CO₂, which stands at approximately 7 € ton⁻¹ [50]. This aspect will exhibit greater significance in the foreseeable future due to the anticipated implementation of CO₂ taxation. 94.66 $ ton⁻¹ of CO_2eq total carbon tax during the project period will be 528,295 $ as depicted in Table 6.

Table 6. Emission data comparison between Diesel generator (DG)-BESS and HydESS-1.

Table 6. Emission data comparison between Diesel generator (DG)-BESS and HydESS-1.

Material	DG-BESS	HydESS-1	Units
Carbon dioxide	223,297	0	kg yr−1
Carbon monoxide	1,408	2.61	kg yr−1
Unburned hydrocarbons	61.4	0	kg yr−1
Particle matter	8.53	0	kg yr−1
Sulfur dioxide	547	0	kg yr−1
Nitrogen oxides	1,322	0.261	kg yr−1

Oxygen cost is based on the literature 168.55 $ ton⁻¹ [51]. The optimized system WT-HydESS-BESS produces 13.349 ton of H₂ annually, so the O₂ produces auxiliary 6.675 ton annually. During the project years, the total O₂ production sales is expected to 28,124 $ with 250-kW PEMFC and PEMWE configuration.

5. Conclusion

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