H2OneTM OFF-GRID SOLUTION

- HYDROGEN-BASED ENERGY SUPPLY SYSTEM FOR ISOLATED AREAS -

Toshimitsu Kumazawa1, Daigo Kittaka2, Masahiro Tsuji2, Junichi Mori2, Ryo Nakajima2 1Toshiba Corporation, 183-8511 Japan

2Toshiba Energy Systems & Solutions Corporation, 212-8585 Japan

This paper presents the purpose, benefits, operation method and feasibility evaluation of H2OneTM Off-Grid Solution. Central to this study problem is confirmation whether it is possible to supply electric power to meet the electricity demand only by renewable energy in the isolated areas. Therefore, we have evaluated economic efficiency using specifications and costs based on actual data. As a result, we are sure to make the feasibility of power cost below 40cent/kWh with H2OneTM Off-Grid Solution.

Keywords: Renewable Energy, Photovoltaic, Wind Turbine, Hydrogen Energy, Off Grid

INTRODUCTION

Toshiba developed Hydrogen-Based Energy System aiming "Energy Localization" for the key to resolve the issue of Energy Security and Economic Independence. Energy Localization stands for an area is not depends on imported resources and generates the electricity in the area. During fossil resource centuries, 19th and 20th century, it is difficult to be free from Energy Security as the resources were located "uneven places". The reason is uneven distribution of resources. The uneven distributed resource in the Earth causes the economic strength and weakness as the resources is the starting point of economic activity in the industry. In the 21st century, Photovoltaic and Wind Turbine would be common tool to generate electricity. However these energy sources are not able to be controlled so that the balance is adjusted generation reserve by fossil fuel generation system such as Gas Turbine and Diesel Generator.

The system aims supplying energy by 100% Renewable Energy for regional energy issue. There are issues regarding stable energy supply in part of isolated and abandoned areas e.g. in islands or un-electrified areas. The residents in some remote islands use diesel generator. However, its fuel cost is expensive because of high transport cost. With unstable Renewable Energy the Hydrogen Energy System is designed for supplying stable energy without grid adjust force or diesel generator. It has been often discussed that electricity self‐sufficiency of the isolated region.

It had been shown that the system capacity for minimizing power generation cost in consideration of supply reliability and environmental performance [1]. Other studies have concluded that Economic evaluation in a system combining battery and hydrogen facility [2]. However, these studies are not evaluated based on the value of the actual system. Therefore, in this study, we will evaluate economic efficiency using specifications and costs based on the actual system.

BENEFIT OF H2OneTM OFF-GRID SOLUTION

Case1: Extrication from Electrical Feeder Line and Cost Subheadings

Localized Energy shall make the society which is free from construction of Electrical Feeder Line and its cost. Construction of Electrical Feeder line requires the social impact.

1) Huge Cost

2) Environmental Impact

3) Human settlements are forced to be moved

Case2: Extrication from Fuel Supply Chain

Regional Energy shall make the resilience society which is free from the risk of collapse in fuel supply chain. Fuel supply chain has 4 kind of issue to be resolved.

1) Pricing Fluctuation due to currency fluctuation or other influential issue such as the war and economic problem.

2) Supply chain shall be damaged by natural disaster such as Typhoon and flood.

3) Cost of Logistics makes the deference in competiveness with main land.

4) The logistics also cause Greenhouse Gas issue for Global warming.

Fig. 1. H2OneTM Off-Grid Solution.

GRAND RENEWABLE ENERGY 2018 ProceedingsJune 17(Sun) - 22(Fri), 2018Pacifico Yokohama, Yokohama, Japan

EVALUATION METHOD

In this paper, we evaluate the economic efficiency of Off-grid Solution by simulation calculation. As a simulation method, the discrete event simulation is adopted.

Fig. 2 shows the configuration of the evaluated system. The operation process of these constituent equipments is implemented on the simulation and a one-year simulation is carried out on hourly step. Photovoltaic generation (PV), Wind Turbine (WT) and Power Demand are given as time series pattern data according to equipment capacity. The Power Demand is fixed at 300kW maximum, and the annual total demand is 1,682MWh/year. The capacity of Fuel Cell (FC) is a fixed 600kW considering Power Demand and the auxiliary power consumption. The capacity of PV, WT and Battery (BATT) are variable within the range given in Fig. 2. We evaluate how the unit cost of electric energy changes when these capacities change by simulation. The unit cost of electric energy is calculated by dividing the 20 years operating total cost by the total electric power demand. The capacity of Electrolyzer (EC) and Hydrogen Storage Tank (TANK) is determined by calculating the minimum capacity required to satisfy the electricity demand throughout the year by simulation.

EVALUATION CONDITION

Fig.3 shows the electricity energy by month of PV, WT and Power Demand. We used data from Okinawa's small scale island (Hateruma). The pattern change of renewable energy generation in Okinawa is the same as in Tokyo. On the other hand, Okinawa's Power Demand in winter is small because Okinawa has a temperate climate. In Tokyo, the Power Demand increases in the winter when the renewable energy generation is small, so the supply-demand balance deteriorates. The advantage of the hydrogen system is to store the energy during the summer and use stored the energy in the winter. Therefore, this input condition is a severe condition for the hydrogen system. However, we carried out an evaluation in Okinawa where there are many isolated islands. Other conditions are shown in Table 1. We set the cost and specification assuming several years later, based on our actual values and the authorized values such as research report released by the ministry.

Fig. 2. System Configuration.

Table 1. Specification of Components.

Fig. 3. Monthly Electric Energy.

Fig. 4. Operation method of BATT, EC, and FC.

GRAND RENEWABLE ENERGY 2018 ProceedingsJune 17(Sun) - 22(Fri), 2018Pacifico Yokohama, Yokohama, Japan

SYSTEM OPERATION

Our system aims to provide stable energy to absorb energy seasonal time shift. The surplus energy in summer is stored, and the stored energy would supply in winter using by the combination of H2EMSTM, FC, EC and BATT technologies. So H2OneTM system can provide the stable energy through a year by using the renewable energy. Storing & using the renewable energy wisely to absorb seasonal fluctuation. H2OneTM store short term fluctuation by battery and long term fluctuation by hydrogen. As a result, it can realize stable, 100% grid independent CO2 free power supply.

Fig.4 shows H2OneTM system operation method. The graph at the top of Fig.4 shows the power input/output of each device at hourly intervals during winter 10 days. In this graph, positive values represent supply power and negative values represent demand power. The graph at the bottom of Fig.4 shows the SOC (State of Charge) of BATT. When the SOC of the BATT is within the operation threshold value, the BATT preferentially deals with supply / demand adjustment of electric power (The span of light blue background). When the SOC of the BATT reaches the lower limit of operation, FC is activated and electric power is supplied using the stored hydrogen (The span of pink background). On the other hand, when the SOC of the BATT reaches the operation upper limit, EC uses electric power to generate hydrogen (The span of green background). When the system is operated as described above, in the summer, the PV energy generation is larger than the electric demand, so the operating time of the EC increases. And since the PV energy generation is small in winter, FC operation time increases. Therefore, looking at the year over, the electricity energy is shifting from season to season by Hydrogen.

RESULT

Fig.5 shows a graph plotting the unit cost of electric energy with the cheapest configuration when PV 5MW without WT. The smallest EC and TANK configurations is calculated according to the capacity of BATT. The configuration of BATT 9MWh is the minimum cost configuration. In order to supply electric energy for isolated island only by BATT without hydrogen related equipment, BATT 31MWh is required.

Fig.6 shows a graph plotting the unit cost of electric energy when PV capacity is changed. The unit cost of electric energy is reduced by reducing the capacity of PV. This result is contrary to our hypothesis. In the evaluations based on the current specifications that we have done so far, it has been found that the unit cost of electric energy is reduced by increasing the PV capacity. The reason for this result is that the cost of BATT, EC, FC and TANK set this time is smaller against PV cost. The cost of BATT and TANK, which is reduced by increasing PV, has become higher than the PV cost increase. Therefore, the influence of PV capacity on power cost changed. For any PV capacity, BATT 9MWh is the lowest unit cost of electric energy. As PV capacity decreases, the sensitivity of change in the unit cost of electric energy due to changes in BATT capacity decreases. If PV capacity is set to 3MW, Power Demand and system power consumption cannot be

satisfied, and electric power independence of the year is not established.

Fig. 7 shows a graph plotting the unit cost of electric energy when WT is added with PV capacity of 4MW. When WT is added, the required capacity of BATT and TANK is reduced and the unit cost of electric energy is reduced. Compared with PV capacity changed case, the reduction amount of the power cost is increasing when the BATT capacity is small. The reason for this result is that the renewable energy leveled by the addition of WT and supported the short-term supply and demand adjustment ability of BATT.

Fig. 5. Result of Optimization for BATT and EC (PV 5MW, WT 0kW).

Fig. 6. Result of PV Variation (WT 0kW).

Fig. 7. Result of WT Variation (PV 4MW).

GRAND RENEWABLE ENERGY 2018 ProceedingsJune 17(Sun) - 22(Fri), 2018Pacifico Yokohama, Yokohama, Japan

DISCUSSION

According to the results so far, in order to reduce the electricity cost by the off-grid solution system, it is not enough to merely expand a specific device. It is necessary to calculate the optimal combination of the capacities of BATT, EC, TANK, PV and WT according to the conditions such as Power Demand.

Fig.8 shows the annual energy flow in the configuration of the smallest unit cost of electric energy with combining PV and WT. The amount of electricity energy supplied to Power Demand is one-third of it can be generated by renewable energy. In order to further reduce the cost for electric power independence by renewable energy, it is necessary to reduce the power that is not effectively utilized. In order to reduce the renewable energy curtailment, it is necessary to improve energy management smarter and more efficiently. Alternatively, it is also effective to utilize it as energy other than electric power. In order to reduce auxiliary power consumption of the system, improvement of engineering is necessary. In order to reduce the loss of BATT and P2G2P, it is necessary to improve the efficiency of the device by developing the cell material and improving the mechanism.

Table 2 shows the target costs for achieving a power cost of 40 cent/kWh in the future only by reducing the cost of the equipment without considering the above improvement measures. These costs are the equipment costs set based on official materials assuming 2035 years. Fig. 9 is a breakdown of the result of trial calculation of power cost in cost setting targeting 40 cent/kWh. This

evaluation does not consider degradation of equipment. Especially BATT is likely to need to be exchanged during the amortization period of 20 years used in this evaluation. Simple calculation doubles the cost of BATT, in which case the power cost is 60.6 yen/kWh. On the other hand, in this evaluation, the annual operating time of the EC was 770 hours, and the FC annual running time was 377 hours. Operation for 20 years is specification feasible. The operation and the maintenance of the equipment need to be examined in the future.

CONCLUTION

We showed the features of H2OneTM Off-Grid Solution realizing "Energy Localization". And, we evaluated economic efficiency using specifications and costs based on actual data. As a result, we clarified issues to reduce power cost. We also propose necessary conditions to achieve 40cent/kWh and show its feasibility.

References

[1] H.Suryoatmojo et al., "Economic and Reliability Evaluation of Wind-Diesel-Battery System for Isolated Island Considering CO2 Emission", IEEJ Trans.PE. Vol.129 No.8, 2009, pp.1000-1008.

[2] Zhuomin Zhou et al., "Capacity Planning and Economical Evaluation of a Renewable Power System for Remote Island", IEEJ Trans.PE. Vol.133 No.1, 2013, pp.19-25.

Table 2. Cost Configuration

Fig. 9. System Cost Breakdown.

Fig. 8. Annual Energy Supply and Demand.

GRAND RENEWABLE ENERGY 2018 ProceedingsJune 17(Sun) - 22(Fri), 2018Pacifico Yokohama, Yokohama, Japan