Off-grid Site Research Articles

Identifying and Analyzing the Technical Challenges of Grid Tide Inverters for PV System: A Case Study of Ethiopia and Zambia

Zambia and Ethiopia are two countries from southern and eastern of Africa due to their geographical location and other factor the environment condition is different. The research aims at identifying and analszing the technical performance issues of Grid tide Inverter (GTI) for PV system due to operating climate and others factors. In Zambia the study focused on the two main solar plants which is under ZESCO national grid at malty facility zone (MFZ), the first one is the 54 megawatts Bangweulu solar power plant by Neon Investment of France, second one is 34MW Ngonye solar photovoltaic (PV) plant. In Ethiopia eight min off-grid site under Ethiopian Electric Utility(EEU) is included. Beltu, Behima, Mino, Ungoge, Korhele,Tum, Omorate and Kofetu. A survey is conducted focusing on identifying and analyzing the technical performance issues of GTI in the above-mentioned area.
 Using Microsoft excel the environmental \climate condition, Solar radiation, Air temperature, Rain falls and Wind of the two country Zambia and Ethiopia is investigated and analysedfor each selected site. A questionnaire and a Sime structure interview is conducted. The basic inverter challenges are investigated from the collected data and the problem is analyzed based on the specific inverter data sheet. The data sheet of the inverter for each site under this study.
 Finally, the real-time performance of the inverter of the off-grid PV mini-grid system installed in a small remote town in Ethiopia and on-grid PV system from Zambia at multi facility zone is analysed using measured meteorological data. From on- grid and off-grid inverter performance challenges, which the researcher collected from different plant the main ones are climate or environmental effect and also over load. Overload is one of the frequent challenges in koftu, behama and amorita this can be due to high population growth and unexpected power demand from the community. 
 Environmental condition affects almost all solar plant site which is under this study. If we compere the climate of east which is Addis Ababa Ethiopia and southern of Africa Zambia Lusaka. The temperature of Lusaka is higher than Addis Ababa by 5.63°C and even in the plant under this study, temperature rise is one of the challenges on the inverter performance, sensitive electronic component bent due to excessive temperature.
 On the other side in Ethiopia Addis Ababa excessive rain affect the inverter. Finally, Addis Ababa has about 1.32 times more rainfall than Lusaka, (Addis Ababa’s 79.54mm vs Lusaka’s average of 60.34mm). For that reason, most of the inverter in Ethiopia on the mini off-grid site are affected by heavy rain condition.

Current Mode Control of Non-Isolated Multi-Phase Interleaved Buck-Boost Converter for Military Battery Charging Application.

Power conversion devices are essential in a remote off-grid site, typically for military purposes where several types of equipment with varying input characteristics are supplied essentially by the same energy source, necessitating the use of a buck-boost converter for DC-DC applications. Because the conventional buck-boost converter's inverting output voltage is incompatible with some applications, the two-switch buck-boost converter is recommended for battery charging in military applications. The nominal input voltage range of the five-phase interleaved buck-boost converter is 9 – 36 V, the output voltage is 28 V, the output power is 3.3 kW, and the switching frequency is 100 kHz. The simulation of the converter with current mode control in the MATLAB/Simulink simulation environment was performed to confirm validity of the operational theory and the simulation results show consistency with theoretical values. Maximum of 74.41 ms and 51.35 % were recorded under all conditions of operation for the settling and overshoot respectively. The obtained data indicates a 1–2 % variation between the measured and theoretical duty cycle.

Hydrogen storage alloys for stationary applications

• An alternative option to store hydrogen in a more compact and safer way than compressed gas systems, applied to a hybrid H2 – Li-ion Power-to-Power plant built in an off-grid site. In off grid locations the energy supply has always been a problem in terms of infrastructures and costs. Power-to-Power (P2P) energy systems could assume an important role especially in these sites, in order to make these places energetically independent and mostly based on renewable sources exploitation. P2P have in fact a great potential to help fixing the problem of intermittent production of RES like wind and PV. This paper aims to describe a real hybrid H 2 -battery P2P system with special focus on the topic of hydrogen storage. Today, H 2 is conventionally stored in high-pressurized vessels and this solution is linked to several technical and regulatory problems (encumbrance, safety, metal embrittlement, too large volumes going above regulatory limits in some cases, etc.). Instead, hydrogen can be absorbed in large quantities using metal hydrides, reaching volumetric density values often higher than liquid hydrogen. Discovered in the late 70 s and extensively studied in the last decades, this kind of solution has never reached a proper commercialization principally due to the limited gravimetric density values, making them unsuitable for automotive and transport purposes. But hydrogen storage alloys (HSA) can raise significant interest for stationary applications. Two of the most promising alloys are considered as applicable in a real P2P plant that will be built in Italy (Ginostra – Sicily) in the framework of the H2020 project REMOTE, modelled, designed and compared to the state-of-the-art solution based on a compressed hydrogen vessel. The final part of the paper covers the preliminary economic assessment of this new kind of plant and a future (optimistic) price trend, plotting a hypothetic learning curve.

Flexible and Scalable Energy Management of Islanded Renewable Energy Sources Storage Systems

Power management in islanded off-grid hybrid power-to-power (P2P) systems is challenging due to multiple decisions that need to be taken at each time instance within a perpetually changing environment. In this work, an energy management strategy (EMS) is proposed as a supervisory control framework that relies on a finite state machine (FSM) approach. The FSM offers a systematic way to develop a flexible decision-making algorithm that is combined with propositional-based logic in order to describe the transitions between the different operating states of the integrated system’s components. Easy extension of the EMS to larger and more complex systems without compromising the operational objectives is the major contribution of the developed algorithm. The proposed approach is implemented in an off-grid demonstration site located in Ginostra, Italy. At this site, the only source of power is a photovoltaic (PV) installation array that supports the specified residential loads. An operation analysis is conducted accompanied by an assessment of the site’s environmental footprint. The results indicate that power is supplied without interruption to the load, and CO2 emissions are decreased by 95.6 % in comparison with the former energy solution applied (diesel generators – DSG).

Enabling Collaborative Decision Making through Applied Systems Engineering Tools, Methods, and Processes

AbstractIncreasingly complex problems involved in systems development drive systems engineers to develop novel decision making processes. The breadth of complex problems demands the interaction of various stakeholders, including both decision makers and subject matter experts, each focusing on specific areas but all addressing a higher level common cause. The process brought forth in this tutorial integrates a series of methods, some widely accepted and others which are novel in nature, in order to enable a collaborative process for technology selection. Quality Function Deployment is used to capture customer desires and focus engineering level requirements. Multi‐Attribute Decision Making is used to identify system configurations when multiple and competing objectives exist, which is a situation where traditional system optimization struggles. System modeling is a necessary step to analyze and understand the impact of various systems options. This seminar therefore introduces the process of surrogate modeling in order to rapidly access elements of modeling and simulation, a necessary step to analyze system options. The very integration of these applied systems engineering methods enables collaborative decision making throughout system development. A proof of concept is presented where each of these methods is applied in the technology selection portfolio analysis of renewable energy system options for a remote off‐grid site.

4.3.3 Enabling Collaborative Decision Making: A Process for Integrating Novel Systems Engineering Tools and Methods for Renewable Energy Portfolio Analysis

Increasingly complex problems drive systems engineers to develop novel decision making processes. The breadth of complex problems demands the interaction of various groups, each focusing on specific areas but all addressing a higher level common cause. The process brought forth in this paper integrates a series of methods, some widely accepted and others which are novel in nature. Quality Function Deployment is used to capture customer desires and focus engineering level requirements. Multi-Attribute Decision Making is used to identify system configurations when multiple and competing objectives exist, which is a situation where traditional optimization struggles. The process of surrogate modeling is introduced to rapidly access elements of modeling and simulation, a necessary step to analyze system options. The very integration of these methods enables collaborative decision making. A proof of concept is presented where each of these methods is applied to aid in the portfolio analysis of renewable energy system options for a remote off-grid site.

On the policy of photovoltaic and diesel generation mix for an off-grid site: East Malaysian perspectives

The recent policy of the Malaysian government to promote use of renewable, especially photovoltaic, energy has warranted a feasibility study on supplementing diesel generation in off-grid sites by solar (photovoltaic) electricity to be done in the Malaysian context. This paper addresses the technical viability and economy of using a photovoltaic (PV) system to supplement an existing diesel generator-based supply in a typical secondary school located at an interior, off-grid and rural site of Sarawak state in East Malaysia. The findings of the present study, would therefore, help the Government with a realistic picture of the techno-economic aspects in implementing its vision regarding renewable energy. Presently, a 150 kW diesel generator supplies electricity to the considered school. The study required simulation of the load sharing pattern of the PV–diesel hybrid system taking into account varied weather and insolation conditions of the chosen site. Also, the purchase price as well as the size of the supplementing PV system that would give the lowest life cycle cost have been determined. The PV system was considered in both forms, i.e. with and without battery back-up. It has been found that if the market price for purchasing a PV system would drop to RM 11.02/W P (Ringgit Malaysia; US$1.00=RM 3.80) i.e. US$2.90/W P, a 35 kW P PV system without battery back-up in conjunction with the diesel generator would be able to supply the selected school’s demand at a marginally lower energy cost than the existing diesel-only system. With continuous research and developments, PV price would keep falling in the near future so that a PV–diesel hybrid system with a higher sized PV is expected to be economically more viable. The reported feasibility study can serve as a guideline for making similar studies in the context of another off-grid site.