battery and a 21.6m3 H2 tank [110]. The main characteristics of these devices are available in Tables2.9,2.10and2.11.
This hybrid P2P solution substantially reduces the use of diesel generators to a value of around 4.4 %. However, the main target is to cover 100 % of the load by using the available RES, keeping the diesel machines switched off the entire year. This is yet to be achieved [110].
Table 2.9: Demo 1: Technical details of the electrolyser and fuel cell [110].
Equipment Rated Power [kW] Efficiency Max. Pressure [bar]
Alkaline Electrolyser 50 75 % 30
PEM Fuel cell 50 60 % 1
Table 2.10: Demo 1: Technical details of the battery bank [110].
Rated Energy [kWh] Ch/Dch rate [kW/kWh] Efficiency SOCmin SOCmax
600 0.5 C 95 % 20 % 80 %
Table 2.11: Demo 1: Technical details of the hydrogen tank [110].
Tank volume [m3] Pressure [bar] H2Capacity [kg] Total energy [kWh]
21.6 3-28 49 1948
According to Table2.12, when the solar power is not enough to supply the load the deficit is mainly met by the battery, which is the most efficient storage option [110].
Table 2.12: Demo 1: Annual RES usage [110].
Load coverage Energy [MWh] Share
Covered by RES 82.02 47.8 %
Covered by fuel cell 6.05 3.5 %
Covered by battery 75.92 44.3 %
Covered by external source 7.56 4.4 % Total residential load 171.54 100 %
The fuel cell is mostly used in the months of July and August, as depicted in Figure2.14a, which are characterized by higher energy demand.
(a) (b)
Figure 2.14: (a) Monthly distribution of load coverage and (b)H2SOC over the year [110].
The operation of the fuel cell led to the consumption of the storedH2and, therefore, theH2 State Of Charge (SOC) is greatly reduced in the summer period, with the usage of almost all the stored gas, as confirmed in Figure2.14b[110]. The situation here depicted is a clear example of the use of hydrogen-based solutions as a long-term ESS.
The second demonstration site, DEMO 2, is located in Agkistro, in northern Greece. There, the owner of a local 0.9 MW HPP, wants to build an agri-food processing unit, and they intend to make the building completely energy-autonomous. Electricity is expected to be supplied directly by the hydroelectric plant, with the P2P system acting as a form of backup. Thus, the only available RES is the 0.9 MW hydroelectric power plant. It used to provide electricity to the main grid, but after the completion of the project, it will also feed the agrifood building [110].
The solution elaborated for the Agkistro location is not substantially different from the one used in Ginostra. Now, there is a 25 kW electrolyser, a 50 kW fuel cell, a 30 kWh battery bank and a 12m3 H2 tank [110]. The technical data of these elements are stated in Tables2.13,2.14 and2.15, respectively.
Table 2.13: Demo 2: Technical details of the electrolyser and fuel cell [110].
Equipment Rated Power [kW] Efficiency Max. Pressure [bar]
Alkaline Electrolyser 25 75 % 30
PEM Fuel cell 50 60 % 1
Table 2.14: Demo 2: Technical details of the battery bank [110].
Rated Energy [kWh] Ch/Dch rate [kW/kWh] Efficiency SOCmin SOCmax
30 2 C 95 % 20 % 80 %
Table 2.15: Demo 2: Technical details of the hydrogen tank [110].
Tank volume [m3] Pressure [bar] H2Capacity [kg] Total energy [kWh]
12 3-28 27 996
Contrarily to the Ginostra DEMO, the battery bank has a rated capacity of only 30 kWh.
Instead of working as an energy buffer, storing the fluctuating power from the intermittent RES, its main functions are only related to supporting the system’s start-up and operating auxiliary devices and a control unit [110].
Since the Agkistro site benefits from a continuous energy source, it was possible to select the smallest available electrolyser. In order to cover the highest load request, which is slightly below 40 kW (Figure2.15a), a 50 kW fuel cell is also selected [110].
Considering the average of the four days given in Figure2.15a, a daily load value of 282.5 kWh is computed. By taking into account the efficiency of the inverter, the DC/DC converter and the fuel cell, a value of around 615 kWh ofH2 is found to be needed for the satisfaction of the load request of one single day. Therefore, aH2 storage system of about 996 kWh was chosen to be installed, guaranteeing enough backup energy for between 1 and 2 days [110].
The total production of the HPP is much higher than the electrical consumption of the agri-food unit. Considering three indicative years the annual energy produced by theHPP is around 3165 MWh for a dry year, 3739 MWh for a medium one and 4232 MWh for a wet one, while the overall annual electrical consumption by the agri-food company is around 87.4 MWh. For each month, the energy produced by the HPP and the required load are shown in Figure2.15b. It is easily noticeable that a higher consumption occurs between December and February and from June to August. This variability is caused by the seasonal use of certain mechanical equipment and by the winter heating and summer cooling needs [110].
(a) (b)
Figure 2.15: (a) Daily load in 4 different months (b) HPP production and load [110].
To summarize, in a situation characterized by a RES production much superior to the load request and a steady, predictable and stable load, the P2P system can be treated as a backup unit.
As a consequence, it is viable to satisfy the peak load and supply backup energy for between one and two days [110].
At last, the third demonstration site, DEMO 3, is in Ambornetti, a small village located in the mountains of northern Italy. This place, which was abandoned for more than 50 years, is now the object of a project aiming to turn the site into a completely off-grid community powered by RES without any kind of fossil fuel backup. In this case, the primary energy sources are biomass and solar energy, which, together with aH2storage system, are excepted to fully supply the load.
The RES used to supply the community are 40 kW PV plant and a 50 kWe biomass-based CHP generator [110].
The H2 system is made of a 25 kW electrolyser, a 50 kW fuel cell, a 30 kWh battery and a smaller 6m3H2tank [110], as described in Tables2.16,2.17and2.18.
Table 2.16: Demo 3: Technical details of the electrolyser and fuel cell [110].
Equipment Rated Power [kW] Efficiency Max. Pressure [bar]
Alkaline Electrolyser 25 75 % 30
PEM Fuel cell 50 60 % 1
Table 2.17: Demo 3: Technical details of the battery bank [110].
Rated Energy [kWh] Ch/Dch rate [kW/kWh] Efficiency SOCmin SOCmax
30 2 C 95 % 20 % 80 %
Table 2.18: Demo 3: Technical details of the hydrogen tank [110].
Tank volume [m3] Pressure [bar] H2Capacity [kg] Total energy [kWh]
6 3-28 13 541
The annual estimated energy required by the community is approximately 96.6 MWh, and the annual energy supplied by the PV system is around 86.8 MWh [110]. Their monthly distribution is given in Figure2.16a.
(a) (b)
Figure 2.16: (a) Monthly PV production and load (b) Monthly energy surplus and deficit [110].
The data concerning the amount of PV energy directly used by the load, energy surplus (from PV) and deficit are summarized in Table2.19. Around 55 % of the total load is directly met by solar power, and around 37 % of the annual energy coming from the PV system is in excess. As presented in Figure 2.16b, the PV energy surplus is higher during the summer and the energy deficit is higher in the winter [110].
Under this scenario, the HSS can be effective in storing the RES excess energy, making use of it when a deficit takes place. If the energy supplied from both the PV and the fuel cell is not enough to satisfy the load, the biomass generator shall be employed to cover the remaining portion. The battery is used for starting the system, not acting as an ESS [110].
Table 2.19: Demo 3: Yearly load and RES supply data [110].
Variable Energy [MWh]
Total load 96.63
PV RES production 86.75
Direct RES consumption 54.01
PV surplus 32.74
Deficit 42.61
The main advantages derived from the new hydrogen systems used in REMOTE are to increase and optimize the exploitation of local RES, reduce the consumption of fossil fuel, decrease local pollution and increase energetic independence, lower the cost of electricity for local consumers, improve the reliability of the electricity service and reduce power outages and avoid new and expensive grid connections [110].
2.9.1.2 Don Quichote
The Don Quichote (Demonstration Of New QUalitative Innovative Concept of Hydrogen Out of wind Turbine Electricity) was implemented at a logistic centre (Figure 2.17a) in the city of Halle, Belgium. The purpose of this project was to demonstrate that the use ofH2as a renewable energy storage solution can be technically and economically viable, with the connection of RES to transport applications. In this demonstration plant (Figure2.17b), hydrogen was produced using energy from on-site wind turbines totalling 1.5 MW and an 800 kW PV system [107].
Running from 2012 to 2018, this initiative was divided into three different phases, which are now described. Prior to the start of the project, there was already aH2refuelling infrastructure at this logistic centre. It was equipped with an alkaline electrolyser, a compressor (450 bar), a steel tank that could hold 50 kg of hydrogen at a maximum pressure of 450 bar, aH2dispenser at 350 bar and two MHE as end users. This system was analysed and tested during the first phase of the project [107].
For the second phase, a more efficient PEME was added, along with a composite storage tank with a capacity for 40 kg of H2 and a 120 kW fuel cell. In the third and last phase, a state-of-the-art electrochemical compressor was installed, replacing the mechanical compressor, which
(a) (b)
Figure 2.17: (a) Colruyt Group logistic centre [111] (b) Don Quichote demonstration plant [107].
allowed for a performance comparison between the two [107]. The complete layout of the system is displayed in Figure2.18.
Figure 2.18: Don Quichote technical layout [107].
Upon completion, this infrastructure was able to supplyH2to vehicles, store energy from RES in the form of green hydrogen (P2G) and convert it back to electrical power by means of the fuel (G2P), supplying it to the grid (P2P) when the economic conditions are more favourable [107].
In order to determine the economic viability of Don Quichote some expenses related to the first phase of the project (the testing of the existing system) were disclosed, being studied in detail. It should be taken into consideration that for this analysis some simplifications were done:
the lifetime of different components tends to vary and depends on factors such as operating hours and maintenance, so it was simply assumed that each component has a lifetime of 20 years and their salvage value was ignored [112].
In this way, the alkaline electrolyser accounts for 37 % of the initial investment, the compressor and the dispenser both take up 19 % each and the storage unit takes up 14 %. The remaining factors only account for 10 % of the total [112]. This information, which provided an overview of the expenses linked withH2production sites, is summarized in Table2.20.
Table 2.20: First phase investment expenses (without VAT) [112].
Cost factor Size Total Cost ( C) Electrolyser ≈156 kW 422,760
Compressor 450 bar 216,000
H2storage 50 kg (450 bar) 157,500
Dispenser 350 bar 218,000
Integration - 41,800
Certification - 8,000
Civil work - 75,000
Permits - 14,000
Total 1,153,060
2.9.1.3 HyBalance
HyBalance is another project that intends to demonstrate the use of green hydrogen in the energy systems of the future, enabling the storage of electricity from wind turbines [113].
For this purpose, aH2facility was built in Hobro, Denmark (Figure2.19a), with the construc-tion starting in 2016 and the plant being inaugurated in 2018. The project itself was concluded in October 2020, but its coordinator continues to run the site [114].
(a) (b)
Figure 2.19: (a) HyBalance facility and (b) Tube trailer to transportH2to customers [114].
This plant is not equipped with fuel cells, so it is not capable of generating electrical power.
Instead, the gas is supplied to industrial clients and to the Danish network of HRS. But, apart from producing green H2, this unit can deliver another important service. During the course of the project, the HyBalance facility demonstrated thatH2production can help to balance the power grid [114].
The selected electrolyser has the necessary flexibility and reaction time to ramp up and down its production in less than 10 seconds (which is required by the Danish authorities in order for the plant to provide balancing services). These short ramp times make it feasible to increase/decrease the consumption of electricity from the grid by the electrolyser when it is desirable to regulate elec-trical frequency. By virtue of this situation, the Danish energy authorities approved the HyBalance facility as a bidder in all electricity markets, particularly on the primary reserve containment where few installations are able to react [115].
Regarding its structure, the most relevant components of this plant are the 1.25 MW dual stack PEME, the high-pressure compressor and the storage tanks. Since fuel cells are not present, there is no need to store great quantities ofH2 to power them, so the storage units act only as buffers.
There is also a pipeline connection to a nearby industrial site, which allows to continuously deliver H2to a local client, with the remaining gas being transported by tube trailers (Figure2.19b) [116].
The chosen electrolyser already includes purification systems [117], which provides aH2 pu-rity of around 99.998 % [118]. Once the construction of the facility was completed and the system was functional, the performance of the electrolyser was assessed with its ramp-up and ramp-down rates being evaluated. As stated before, this device is made of two stacks: stack A and stack B. To test its ramp-up rate, stack A had its power raised from 10% to 100% while the power of stack B was raised from 0% to 100%. It was noticeable that the load change took place within 1 second.
To test the ramp-down rate both stacks were lowered from 100% to 10% which took 4 seconds [116]. The results are shown in Figures2.20aand2.20b.
(a) (b)
Figure 2.20: Current of stack A and B andH2flow during [116]: (a) ramp up (b) ramp down.
2.9.1.4 Haeolus
In Haeolus (Hydrogen-Aeolic Energy with Optimised eLectrolysers Upstream of Substation), the plan is to integrate a 2.5 MW PEME in a pre-existing 45 MW wind farm, the Raggovidda Wind Park (Figure2.21a). This power plant is located in the Varanger Peninsula (Norway), in deep Northern Europe, above the Arctic circle. Unsurprisingly, this is a region that is very thinly populated, and while the wind park has a concession for 200 MW, only 45 MW have been built so
far due to the underdeveloped transmission grid in this region [62]. Nowadays, similar scenarios are not uncommon, with many valuable wind resources being located in sparsely populated areas with weak power grids and sometimes far away from regions where energy could be stored us-ing PHES. Takus-ing this situation into account, the owner of the Raggovidda Wind Park initiated this project in order to develop a new business model, which is selling hydrogen in addition to electricity [62].
(a) (b)
Figure 2.21: (a) The Raggovidda wind park and (b) the Raggovidda wind-Hydrogen facility [62].
Briefly, the wind-Hydrogen system of Raggovidda (Figure2.21b), which is under develop-ment, consists of a PEME, a H2 storage unit and a fuel cell. There is also a control system re-sponsible for monitoring all the relevant variables and controlling the operation of the mentioned devices. The produced hydrogen can be re-electrified, used as fuel for transport or employed in the chemical industry [43]. An overview of the system’s organization is given in Figure2.22.
Figure 2.22: Diagram Raggovidda wind-Hydrogen facility [119].
The electrolyser is a 2.5 MW PEME (made of two 1.25 MW modules) which has an output pressure of 30 bar. The 65m3tank has a storage capacity equivalent to approximately 170 kg of H2(T = 0 ºC, p = 30 bar) At last, the fuel cell has a rated power of 120 kW, but it is restricted to 100 kW due to limitations in the connection point [43].
The technical and economical details of the electrolyser are given in Tables 2.21 and2.22, respectively. Meanwhile, the technical details of the fuel cell are provided in Table2.23.
Table 2.21: Technical data of the electrolyser [43].
Parameter Value
Nominal Power 2.5 MW
Minimum Power 0.3 MW
Efficiency ≈70 %
Hydrogen delivery pressure 30 bar Hydrogen production rate 45 kg/h
Start-up time (cold start) 1200 s Response time (warm start) 30 s
Shut down time 1 s
Ramp rate up/down 60 MW/min
Table 2.22: Economic data of the electrolyser [43].
Parameter Value
Calendar life 20 years Lifespan 40,000 operation hours
CAPEX 1328 C/kW
OPEX 60 C/MW year
Stack replacement 354 C/kW
Table 2.23: Technical data of the fuel cell[43].
Parameter Value
Nominal Power 120 kW (limited to 100 kW)
Minimum Power 12 kW (10%)
Efficiency ≈50 %
Hydrogen consumption 9 kg/h
Response time (warm start) 300 s
Warm start time < 5 s
Ramp rate up/down < 3 s to full power
There is a proposal to replace this lower-pressure tank with a 300 bar storage unit. Using a compressor, theH2would be compressed from 30 bar to 300 bar, but this is not part of the current scope of supply [43].
2.9.2 Scientific papers review
Numerous works were and are still being made to evaluate the economics behindH2 produc-tion across multiple countries. A set of relevant scientific papers are summarized next.
In [120], the authors analysed the cost of producingH2 in Spain and Portugal and its conse-quences for the Mercado Ibérico de Eletricidade (MIBEL). Multiple scenarios, based on both the Spanish and Portuguese energy and climate plans were tested. To this end, the CEVESA sim-ulator was used to reproduce optimistic and pessimistic scenarios. The authors concluded that hydrogen production can help to reduce spillages by increasing the demand for hours of higher non-dispatchable generation.
Meanwhile, in [121], the authors executed several Monte Carlo simulations to calculate the cost of green H2 production in Poland. Employing large-scale hydrogen production facilities, driven by wind and solar power plants, present costs were estimated to be between 6.37 C/kg and 13.48 C/kg. The cost of producingH2 in 2030 and 2050 was also projected, resulting in an estimated cost between 2.33 C/kg and 4.30 C/kg, in 2030, and ranging from only 1.23 C/kg to 2.03 C/kg, in 2050.
In [122], the authors evaluated the viability of using a P2P solution to replace diesel generators.
The Homer software was used to carry out the simulations, which analysed theH2storage strategy across different seasons. More exactly, the plan was to use an electrolyser to produce H2 from DER surplus during the Winter in a P2G process. Later, when the demand was higher during the Summer months, the previously obtainedH2would power a fuel cell and supply electricity back to the grid. In the economic analysis, several CAPEX and Operational Expenditure (OPEX) values were used for the electrolyser,H2tank and fuel cell. In this work, the usage of H2 for end-uses other than electrical energy production was not assessed.
In Slovenia, the prospect of greenH2production in a HPP was studied. Its price was compared with that of otherH2 production techniques [123]. The possibility of using theH2PP to provide ancillary services was also considered and led to a higher profit. Additionally, the authors exam-ined the competitiveness of green H2 within multiple sectors, such as industry, heat generation, and mobility.
In [124], the authors assessed a H2PP supplying multiple H2 customers. The electrolyser, which was powered by wind turbines and/or a PV power plant, suppliedH2to a fuel cell, a HRS for FCEV, a Biological Hydrogen Methanation (BHM) process and to be injected into the NG grid. The influence of the energy source (wind turbines or PV panels) was studied, and it was concluded that the replacement of the wind turbines by the PV plant led to a reduction in the cost of producingH2 production. Furthermore, the economic feasibility of this system was evaluated using the resulting Levelised Cost Of Hydrogen (LCOH). Before the addition of the BHM process, a LCOH around 7 C/kg was accomplished. With the installation of the BHM, the LCOH was cut down to approximately 5 C/kg.
An economic analysis of green hydrogen production in different Italian regions was carried out in [125]. The electrolysers were powered by electricity bought from the grid or by several
RES, including wind, solar and geothermal, through a Power Purchase Agreement (PPA) with a price between 50-100 C/MWh. The obtainedH2was used for mobility or injected in the NG grid.
It was concluded that, depending on energy prices, the LCOH could range between 6.90 C/kg and 9.85 C/kg.
At last, in [126], the authors presented a multi-state model for electrolysers, considering three states of operation (production, hot standby and idle) instead of only two (production and idle).
The produced H2 was supplied to a HRS. The three states model, which was simulated using data from a pre-existingH2PP, was compared with the two states model. The simulation scenarios assumed differentH2 demands, multipleH2 prices, various electricity prices, and multiple effi-ciency values for the electrolyser. The results show that the usage of the multi-state model led to a reduction in the cost of producingH2.
2.9.3 Overview of the reviewed projects and publications
In Table2.24it is presented an overview of the main services provided by the differentH2PP found in the presented works.
According to these data, the most common service is the usage of H2 for mobility (HRS), followed by the utilization ofH2 for electricity production (fuel cell). There are also multiple cases whereH2 is supplied to industrial facilities, to be used as a feedstock, or mixed with NG to be combusted. Only in one work, [124], hydrogen is used for BHM. Moreover, only in the HyBalance project is the producedH2directly loaded into tube trailers to be transported. However, this does not necessarily mean that in other worksH2cannot be transported to other locations by these trailers. For instance, in the Haeolus project, theH2PP is located in a relatively isolated location, so it can be inferred that the produced hydrogen is to be transported to other places.
Nevertheless, that is not clearly stated in this project, so this activity was not considered when identifying the services provided in that work.
Table 2.24: Services identified in the literature review.
Reference Production Fuel cell Feedstock NG mix HRS Transport BHM
Remote ! !
Don Quichote ! ! !
HyBalance ! ! ! !
Haeolus ! ! ! !
[120] ! unspecified
[121] ! unspecified
[122] ! !
[123] ! ! ! !
[124] ! ! ! ! !
[125] ! ! !
[126] ! !
Regarding the reviewed scientific papers, one common conclusion is that a reduction in the cost of the components ofH2PP is necessary to make greenH2competitive.
Hydrogen Power Plant Model
In this chapter, it is provided a detailed overview of the proposed and implemented simula-tion models. The mathematical formulasimula-tion behind the operasimula-tion of aH2PP is depicted, and two different optimization problems are described.
In the first problem, the optimization intends to maximize the profit of the operator of aH2PP when it participates in an electricity market, considering a strategic engagement with multiple customers. In other words, theH2PP operator assesses its engagement in the electricity market taking into account the different multi-energy services it can provide.
In the second problem, more advanced and with a higher degree of complexity, theH2PP is incorporated in a Medium Voltage (MV) distribution grid. Here, theH2PP is part of a VPP and it is controlled by the grid operator, who aims to minimize operating costs. Under this model, the impact of theH2PP in the operation of this network is assessed accounting for high penetration of RES.
This chapter starts with a description of the structure of theH2PP envisioned for this work.
This is followed by an explanation of the first model, where the steps of the implemented algorithm are traced, and the mathematical formulation behind it is exposed. Afterwards, the second model is presented, and again, the created algorithm is described and the mathematical formulation behind it is carefully outlined.