The energy demand values have been calculated based on the end-user energy values using the actual energy demand values that are previously supplied by diesel generators, battery storage, kerosene, and solar technologies in the village community. In this case, the amount of power required at a particular time in a day is multiplied by the time of usage and the number of electrical items. If a certain amount of power is needed during a particular hour of the day, then its value is called the hourly energy demand. The hourly energy demand is determined using the following equations (Kaunda et al., 2020a):

where P_D(hourly) = the hourly power demand value (kW), t = the time of usage (hour) and

n = number of electrical items

Then, by using the above equation with average hourly energy demand, the daily average energy demand can be determined using the following equation:

where P_D(hour1) = the demand power at time t₁ and t₁ = the time at the first hour.

P_D(hour2) = Power at time t₂ and t₂ = Time at the next hour

At any particular time, when there is a prolonged period of energy usage of more than a month, the monthly average energy demand is determined by the daily average energy demand (P_D(hourly)) × 24 hours/day.

Based on the actual analysis and using the above equations, the summary of the daily and monthly energy demand in the research study villages and its equivalent total in kWh are summarized in Table 1 below.

In this research study and by referring to the schematic diagram below, for the system design configuration options, the consumer load demand power is supplied by the microhydro turbine system while the peak demand power is supplied from the hydrogen engine-generator with hydrogen gas being supplied by the electrolyser system using energy storage from the micro hydro turbine system as shown in the block diagram in Figure 3 below.

The design configuration for micro hydro turbine systems has focused on supplying power to meet consumer load demands. However, the results from the existing system design shows that the micro-hydropower plant without energy storage cannot supply enough power to the peak hours of the day, hence causing a power deficit. This effect in power shortage and the option of supplying additional power to the load demand during peak hours has been analysed and evaluated in detail with the results from HOMER optimization model (Menezes et al., 2014) for renewable energy in the sections below by integrating the micro-hydropower plant with hydrogen enginegenerator system.

The analysis of the load demand curve reveals distinctive features of a typical load demand curve with low power demand (off-peak hours) during midnight hours and increased demand during morning hours (breakfast time) and midday hours (lunch time). The results also show peak power demand values during the evening hours at approximately 19:00 hours to 20:00 hours, which reflects the typical high-power demand values in most houses at a particular time of day. The daily total energy consumption also considered the general energy usage between weekdays and weekends, on which weekend households consumed more energy than weekdays, as shown in Figure 4 below for the computed hourly power demand values for the research study village communities.

The results of the analysis of the research study village’s power demand values reveal that the community area is characterized by two (2) major distinct power demand patterns. The first part is the hours with the maximum power demand values for which the peak value reaches 101.8 kW at approximately 19:00 hours. This is when most of the family members are at home and therefore use electrical equipment, especially in the kitchen, for cooking; watching TV and electrical lights is switched on at this time of day. Most of these electrical equipment consumes a considerable amount of electricity at this particular time of day; hence, when considering the total load demand in the village area, a high peak demand for electricity consumption occurs. On the other hand, the second part shows the minimum power demand values (low demand hours) on which the lowest power demand value dropped to approximately 8.42 kW during the midnight hours. Based on the analyzed data, the daily average power demand in the village community is 46.43 kW. The general trend shows that the power demand values are not constant and are characterized by a high power fluctuation, which results in a large power range of 93.38 kW between the high peak and low peak power demand values; this effect needs to be taken into consideration during the resource assessment of power supply options. The total daily energy demand for the village community in the research area is estimated to be 1,114.38 kW/h.

In this research, the optimized system integration consists of a micro hydropower system that is used to supply the base load; additionally, because of surplus power, additional systems have been added to use excess energy produced most of the time. This includes an electrolyser system and a hydrogen ICE engine generator. An electricity surplus during low demand is used to power this additional system, especially during the night hours. An electrolyser is used to produce hydrogen gas by electrolysis of water. During the peak hours of the day, the micro hydro turbine is not able to supply the required electricity demand; in this case, the peak electricity demand is supplied by the ICE engine-generator system, which is fuelled by hydrogen gas. In this design layout, no electricity storage is provided; instead, the excess power produced is supplied to an electrolyser system. To stabilize the system, ballast loads are installed to surge power due to abrupt changes in consumer load and load rejection. The electricity supplied from the micro hydro turbine to the consumers, electrolyser and ballast loads is controlled and managed by an automatic transfer switch (ATS). During operation, the hydrogen gas produced from the electrolyser is stored in a storage tank and is used to power the engine-generator system, which supplies additional electricity needed during the peak hours of the day. On the other hand, the excess hydrogen gas produced by the system will be sold to the local fertilizer and oil industries for use in the production of fertilizers and oil refinery processes, respectively, while the produced oxygen gas will be supplied to the local health centers and hospitals in the nearby villages to support life for the patients who are in need of oxygen in the emergency and ICU wards.

The system design configuration based on the optimized combination and operating condition is shown in Figure 5 below.

The system model has been developed and optimized by Homer Energy System Software, and based on the energy supply and demand results, the system consists of a 75.5 kW micro-hydroturbine as the primary power supply, a 40 kW hydrogen gas engine-generator system as the secondary power supply, a 70 kW electrolyser system, a 1,114.38 kWh/day consumer load demand and a dump load (ballast). The electrolyser system is operated during the low-demand hours of the day and supplied with excess electricity from the micro hydro turbine. The produced hydrogen gas in the system design is stored in a hydrogen tank with a maximum storage tank capacity of 30 kg, as shown in Figure 6 below.

In this system design layout, an additional source of electricity production occurs from the hydrogen ICE enginegenerator system with a 40 kW rated capacity, which will operate during the peak hours and power deficit hours of the day. A comparison of the two electricity production sources reveals that the hydro turbine will make the greatest contribution to approximately 95% of the power supply, while the engine generator can only supply approximately 5% of the required load, which occurs mainly during the peak energy demand hours of the day.

Energy consumption is also divided into two main categories: the AC primary load, which accounts for approximately 63% of the total load demand, and the electrolyser load for hydrogen production, which accounts for approximately 37% of the total load demand. These two consumer loads are the main energy consumption for the system on which there is no excess electricity that is produced and sent to the ballast loads, as shown in Table 2 below.

This resulted in the proper optimization of the power supply from the micro hydro turbine system to supply energy to the AC load demand and electrolyser system that produces hydrogen gas, which is the fuel for the power engine-generator system that supplies peak power, as shown in Figure 7 below.

To highlight the operational effects of the micro hydro turbine system, the relationship between the dumping coefficient and the load demand power of the system have been simulated during the 24 hours period based on the actual load demand power (dynamic loading condition). The results analysis confirm with the daily profile of the load power demand which shows that during low demand hours of the day (night hours), the dumping coefficient is at its highest while during the high demand and peak hours of the day (evening time), and the dumping coefficient is at its lowest value as shown on Figure 8 below.

In doing this research and according to the research objectives, there are few research studies that are worth mentioning for the future works, as follows:

In micro hydropower system design and development, modeling and simulation are needed to determine system performance characteristics. In most system designs, static simulations are conducted, which do not reflect the actual operational characteristics of micro-hydropower plants. Therefore, to obtain the true performance characteristics of a micro hydropower systems, additional dynamic simulations (Moselane et al., 2022) must be performed to evaluate turbine and generator performance due to load demand changes or load rejection.

The introduction of a hydrogen engine generator into the system maintains the renewable energy fraction due to the zero emission of pollutants from the engine. However, due to the high temperature available from engine exhaust systems, an additional system, such as an absorption chiller (absorption refrigeration), could be added to the engine exhaust system to increase energy efficiency (Pesaran et al., 2018).