System Unavailability Research Articles

Interplay of the ubiquitin proteasome system and the innate immune response is essential for the replication of infectious bronchitis virus.

Infectious bronchitis virus (IBV) is the only coronavirus known to infect poultry. The replication and pathogenesis of IBV are poorly understood, mainly because of the unavailability of a robust cell culture system. Here, we report that an active ubiquitin proteasome system (UPS) is necessary for efficient replication of IBV in Vero cells. Synthesis of IBV-specific RNA as well as viral protein is hampered in the presence of chemical inhibitors specific for the UPS. Like other coronaviruses, IBV encodes a papain-like protease (PLpro) that exhibits in vitro deubiquitinase activity in addition to proteolytically processing the replicase polyprotein. Our results show that the IBV PLpro enzyme inhibits the synthesis of interferon beta (IFNβ) in infected chicken embryonic fibroblast (DF-1) cells and that this activity is enhanced in the presence of melanoma differentiation-associated protein 5 (MDA5) and TANK binding kinase 1 (TBK1). IBV PLpro, when overexpressed in DF-1 cells, deubiquitinates MDA5 and TBK1. Both of these proteins, along with other adapter molecules such as MAVS, IKKε, and IRF3, form a signaling cascade for the synthesis of IFNβ. Ubiquitination of MDA5 and TBK1 is essential for their activation, and their deubiquitination by IBV PLpro renders them unable to participate in antiviral signaling. This study shows for the first time that there is cross-talk between the UPS and the innate immune response during IBV infection and that the deubiquitinase activity of IBV PLpro is involved in its activity as an IFN antagonist. This insight will be useful for designing better antivirals targeting the catalytic activity of the IBV PLpro enzyme.

A renewal process model with failure based PM and imperfect CM for unavailability exploration

PurposeThe paper aims to explore unavailability of dormant systems that are under both preventive and corrective maintenance. Preventive maintenance is considered as a failure based maintenance model, where full renew is realized at the occurrence of every nth failure. It proposes the imperfect corrective maintenance model, where each restoration process deteriorates the system lifetime, probability distribution of which is gradually changed via increasing failure rate.Design/methodology/approachBasic reliability mathematics necessary for unavailability quantification of a system which undergoes a real aging process with maintenance has been derived proceeding from renewal theory. New renewal cycle was defined to cover the real aging process and the expectation of its length was determined. All events resulting in the failure of studied system were explored to determine their probabilities. An integral equation where the unavailability function characterizing studied system is its solution was derived.FindingsPreventive maintenance is closely connected with the occurrence of the nth failure, which starts its renew. The number n can be considered as a parameter which significantly influences the unavailability course. The paper shows that the real aging process characterized by imperfect repairs can significantly increase the unavailability courses in contrast with theoretical aging. This is true for both monitored and dormant systems.Originality/valueAlthough mathematical methods used in this article were inspired and influenced by the work of reference (van der Weide and Pandey, 2015), derivation of final formulas for unavailability quantification considering the new renewal cycle is original. Idea of the real aging process is new as well. This paper fulfils an identified need to manage the maintenance of realistically aging systems.

Availability Modeling and Performance Improving of a Healthcare Internet of Things (IoT) System

Internet of Things (IoT) is improving human life in a more convenient and simpler way. One of the most promising IoT applications is healthcare. In this paper, an availability model of a healthcare IoT system is proposed which is composed of two groups of structures described by separate Markov state-space models. The two separate models are analyzed and combined to implement the whole IoT system modeling. The system balance equations are solved under a given scenario and some performance metrics of interest, such as probabilities of full service, degraded service, and the system unavailability, are derived. Detailed numerical evaluation of selected metrics is provided for further understanding and verification of the analytic results. An availability performance improving (API) method is also proposed for increasing the probability of system full service and decreasing the system unavailability. The proposed system modeling and performance improving method can serve as a useful reference for general IoT system design and evaluation.

A systematic method to develop three dimensional geometry models of buildings for urban building energy modeling

Three dimensional (3D) geometric models of buildings are foundational for urban building energy modeling. A complete 3D geometric model contains building-relevant information like building footprint, height and Window-to-Wall Ratio (WWR). Existing methods creating these models have certain limitations, such as unavailability of Geographic Information System (GIS) databases and Light Detection and Ranging (LiDAR) data for many cities, and restricted flying space for Unmanned Aerial Vehicles (UAV). To tackle these issues, this study has developed a systematic method developing 3D geometric models, with 1) building footprint acquired from combination of two internet maps, namely Baidu Map and OpenStreetMap; 2) building height estimated from the number of storeys for residential buildings and determined using the building vertical edge method for non-residential buildings, and 3) building WWR calculated from buildings’ elevation images using an Artificial Intelligence (AI). The validation work revealed that more than 85 % of acquired building footprints had absolute relative errors less than 10 %, and this percentage was 87 %, 74 % and 75 %, for height of residential buildings, height of non-residential buildings and WWR, respectively. To demonstrate the application of the method, a newly developed urban district in Nanjing, China was used as a case study.

Performance analysis of stand‐alone solar photovoltaic thermal dryer for drying of green chili in hot‐humid weather conditions ofNorth‐EastIndia

AbstractIn the present study, an innovative stand‐alone solar photovoltaic thermal (PVT) dryer has been designed and tested in hot‐humid weather conditions of North‐East India for drying green chili. The electrical output of the hybrid PVT solar dryer has been utilized to operate the blower for the dryer making the system self‐sustained. A comparative analysis of the drying phenomena under the open sun and in the PVT based dryer is performed. Mathematical modeling is also done to investigate the drying kinetics of green chili for both drying conditions. Results indicate that the moisture content of 0.030 (d.b.) in the solar dryer and 0.035 (d.b.) in the open sun has been reduced for a span of 21 and 37 hr, respectively. Hybrid PVT solar dryer has achieved an average thermal efficiency of 31.37% and an average specific moisture extraction rate of 0.228 kg/kWh. The overall energy consumption for drying green chili is calculated to be 4.90 kWh/kg. Also, the overall thermal efficiency of 64.16%, thermal efficiency of 30.15%, and average electrical efficiency of 12.92% are secured. The results demonstrate the improved performance of the present PVT dryer for green chili drying in comparison to some of the conventional direct/indirect solar dryers.Practical ApplicationsThe present PVT solar dryer system can be utilized for drying the products using thermal energy produced by PVT air collector as well as generating electrical power in the decentralized off‐grid areas. Solar drying is not adequately popular in the North‐Eastern part of India due to the unavailability of solar drying systems for farmers. The agricultural products can be dried in the farming areas by installing this system. This PVT solar dryer provides a solution to the farmers for drying at zero energy cost and can be used as a source of income generation. This PVT solar drying system can be used to increase the storage life and reduce the spoilage and deterioration of agricultural commodities. Energy efficient solar drying process, high‐quality products, and faster drying rate compared to traditional drying method can be achieved with the help of using this system.

Simultaneous transmission of clock and data signals in photonic-assisted WDM passive optical networks

This work reports on the use of a gain-switched vertical cavity surface-emitting laser (VCSEL) optical frequency comb (OFC) to generate multiple optical carriers for applications in future wavelength-division multiplexing (WDM) passive optical network (PON) systems. The VCSEL-based OFC system was tested for its ability to simultaneously transmit error-free data signals up to 30 Gbps, and a 50 MHz clock signal proposed to be used for latency monitoring of the network. The system was demonstrated over a fiber distance beyond 20 km. Four optical carrier signals were filtered from the generated OFC. Three of the four optical carriers were combined and amplitude-modulated with 5 and 10 Gbps on–off keying (OOK) data signals. The fourth optical carrier was amplitude-modulated with a 50 MHz clock signal. These four modulated optical carriers were multiplexed and transmitted over 21 km of standard single-mode fiber. When the three data-carrying optical carriers were modulated with 5 Gbps OOK data and multiplexed with the clock-carrying carrier, a negligible transmission penalty was achieved after fiber transmission. When these three data-carrying optical carriers were modulated with 10 Gbps OOK data and multiplexed with a clock-carrying carrier, a maximum transmission penalty of 4.8 dB was achieved after fiber transmission. The system was investigated at a minim bit error rate (BER) of 10 − 9 . A receiver sensitivity of less than − 11 d B m was achieved at both bit rates. The clock signal suffered little effect when transmitted with the three optical carriers at both 5 and 10 Gbps data rate. A power penalty of 15.37 dB, mainly due to fiber attenuation, was experienced in the clock after fiber transmission. Due to the unavailability of the numerical system to quantify the clock performance in terms of phase noise, the phase-noise results could not be provided. Nevertheless, the provided qualitative results were able to show that the transmitted clock integrity was able to be retained after being multiplexed with transmission on the 21 km fiber channel. For the first time, to the best of our knowledge, we have simultaneously reported on data and clock transmission results using a low-power, VCSEL-based OFC to realize a WDM-PON system. These results are attractive as they demonstrate and motivate the possibility of using gain-switched VCSELs as OFC sources in future WDM-PON networks requiring enhanced channel capacity and stringent network latency monitoring to realize intelligent, simple, and power-efficient PON networks.

Attitudes of Spanish-speaking veterinarians interested in anaesthesia towards use of total intravenous anaesthesia in dogs: a survey study

ObjectivesTo describe Spanish-speaking veterinary anaesthetists’ attitudes towards use of total intravenous anaesthesia (TIVA) in dogs. Study designProspective online voluntary survey. PopulationData from 300 answered surveys. MethodsAn anonymous questionnaire was sent via e-mail to representatives of the four largest Spanish-speaking veterinary anaesthesia and analgesia associations. It was distributed through mailing lists (Spain, Argentina, Mexico) or social media (Spain, Chile) to gather information on the use, opinions and perceived advantages of TIVA, as well as on preferred alternatives to isoflurane for providing general anaesthesia. Logistic regression was used to test for response associations. ResultsA total of 275 (92%) respondents had used TIVA (24% rarely, 36% sometimes, 40% very often or always). There was an association between a higher rate of TIVA usage and a low specialization level, less clinical experience and unavailability of anaesthetic gas scavenging systems. The main reasons for not using TIVA were lack of familiarity with the technique (92%), unavailability of infusion pumps (32%), established institutional anaesthetic protocol (32%), and technical difficulty (20%). Among frequent TIVA users, a higher proportion reported the greater ease of TIVA use (52%) compared to those that did not perceive such benefit (17%) [odds ratio (OR) = 5.2; 95% confidence interval (CI95), 1.7–16.6; p = 0.004). More respondents did not consider TIVA more expensive (60%) (OR = 2.1; CI95, 1.0–4.3; p = 0.034), more difficult to perform (59%) (OR = 2.5; CI95, 1.3–4.9; p = 0.006) or to manage the equipment (53%) (OR = 3.3; CI95, 1.4–7.8; p = 0.008), than inhalational anaesthetics. During isoflurane shortages, respondents reportedly preferred using an alternative inhalational agent (59%) rather than TIVA (47%). Conclusions and clinical relevanceTIVA use is widespread among veterinarians within the surveyed associations. Frequent TIVA users reported greater perceived advantages. In situations of isoflurane shortage, an alternative inhalational anaesthetic was preferred over TIVA.

Long-lasting infectivity of Plasmodium vivax present in malarial patient blood to Anopheles aquasalis

Experimental studies for understanding the relationship between Plasmodium vivax and its vector hosts are difficult, because of to the lack of a long-term, in vitro continuous culture system unavailability of infected blood samples, seasonality of the disease, and the concentration of most cases in remote areas. This study evaluates the duration of the infectivity of P. vivax to Anopheles aquasalis after collecting blood from malaria-infected patients. Blood was collected from patients and stored at 4 °C and 37 °C. Every day, for 4 days, the blood was fed to An. aquasalis adult females, and a Giemsa-stained thick blood smear was mounted to account for sexual (gametocytes) and asexual (trophozoites and schizonts) stages and calculate parasitemia. Oocysts in the midgut of the mosquitoes were counted on the seventh day after feeding. Kruskal-Wallis test was used to compare the mean number of oocysts (MO) and the parasite density (PD) in each storage condition and post-infection time-points. The Mann-Whitney test was used to compare the number of oocysts for each day between temperatures. The results show that P. vivax stored at 4 °C and at 37 °C has its infectivity to An. aquasalis preserved for 2 days and 3 days, respectively. Infection rate (IR), PD and MO were higher on the day of blood collection and decreased gradually over time. The parasite density (number of parasites/μL) diminished faster at 4 °C than at 37 °C. In this study, a preservation protocol is shown for long-lasting infectivity of P. vivax in a blood sample taken from malaria-infected patients. These results show that infectivity of P. vivax stored at 4 °C and at 37 °C to An. aquasalis persist until 3 days after blood collection, but parasite density, infection rate, and mean of oocysts decreased 24h after blood collection. Since the malaria cases are increasingly far from the urban areas these results indicate that is possible, losing some infectivity, to realize experimental infections several dozen hours after the blood collection. However, it is necessary to improve the procedures for preserving P. vivax gametocytes for mosquito infection in the laboratory.

A Moving Target Defense Strategy for Internet of Things Cybersecurity

Internet of Things (IoT) systems are becoming more common and present in our daily lives. The increase of Internet-connected devices has caused attackers to focus their attention more on these devices. Therefore, new and more sophisticated attacks on IoT systems are discovered every day. Currently, to ensure reliability and operability, most IoT systems are designed to operate in a relatively static configuration in a highly heterogeneous environment. However, a system that does not continuously change its configurations, i.e., a static system, gives an advantage to attackers; with enough time and resources, an attacker will eventually find and exploit the vulnerabilities of any static target. This work proposes a Moving Target Defense (MTD) strategy that randomly shuffles the communication protocols through which a node communicates to a gateway in an IoT network. The system’s configuration changes have an associated cost. The objective of the proposed MTD strategy in this work is to balance the increase in system performance overhead, the increase in business impact (system unavailability), and, at the same time, the decrease in the probability of success of a given attack. A framework is proposed to design this strategy; this framework can guide any MTD strategy for IoT systems. The framework’s objective is to find, after several iterations, the MTD strategy parameters that achieve a balance between five different measurable variables of an IoT system.

АКТУАЛІТЕТИ ВПРОВАДЖЕННЯ 5G-ТЕХНОЛОГІЙ У КНР В УМОВАХ ЦИФРОВІЗАЦІЇ ЕКОНОМІКИ

The study examines the main trends in the digitalization of the economy that includes implementation of 5G technologies in various spheres of life on the example of the People's Republic of China. To estimate the readiness of the Chinese economy an analysis of the main indicators characterizing the level of development of information and communication technologies and the presence of positive factors for the successful implementation of innovations was conducted. The first part of the article presents advantages and possible risks of 5G mobile network and its value for various life areas and different countries (by development level). The main issues concerning 5G implementation into existing business models and design of new business structures are defined as system unavailability. That`s why, the second part is based on research of the level of 5G distribution in the socio-economic spheres in China at today`s level. Also, the study examines the projects planned under the strategy "Made in China 2025". As 5G technology is an important component of future competitiveness, it can be the ground for a new round of confrontation between the two largest economies, the United States and China. The third part of the study represents the analysis of the main events took place during trade conflict in 2018 and aspects of its exacerbation because of competition for leadership in production and supply of ICT products that require connection to 5G. The study displays the modern ICT market conjuncture, inclusive of restrictions and sanctions imposed on some Chinese companies and forecast of potential ways of situation changes and revision of China`s place in world trade structure. The analysis proposed a set of measures for the improvement of labor market and financial and technical sector functioning, and the development of digital infrastructure, aimed at further improving the digital economy and competitiveness of China. The prospects in this direction include broadening the law and regulation framework, increasing in the state investment connected with innovations and development and extension of 5G mobile network.

Distributed Mixed Voltage Angle and Frequency Droop Control of Microgrid Interconnections With Loss of Distribution-PMU Measurements

Recent advances in distribution-level phasor measurement unit (D-PMU) technology have enabled the use of voltage phase angle measurements for direct load sharing control in distribution-level microgrid interconnections with high penetration of renewable distributed energy resources (DERs). In particular, D-PMU enabled voltage angle droop control has the potential to enhance stability and transient performance in such microgrid interconnections. However, these angle droop control designs are vulnerable to D-PMU angle measurement losses that frequently occur due to the unavailability of a global positioning system (GPS) signal for synchronization. In the event of such measurement losses, angle droop controlled microgrid interconnections may suffer from poor performance and potentially lose stability. In this paper, we propose a novel distributed mixed voltage angle and frequency droop control (D-MAFD) framework to improve the reliability of angle droop controlled microgrid interconnections. In this framework, when the D-PMU phase angle measurement is lost at a microgrid, conventional frequency droop control is temporarily used for primary control in place of angle droop control to guarantee stability. We model the microgrid interconnection with this primary control architecture as a nonlinear switched system and design distributed secondary controllers to guarantee stability of the network. Further, we incorporate performance specifications such as robustness to generation-load mismatch and network topology changes in the distributed control design. We demonstrate the performance of this control framework by simulation on a test 123-feeder distribution network.

Analysis and Evaluation of Cyber-attack Impact on Critical Power System Infrastructure

ABSTRACT This paper identifies and proposes two novel indices for cyber-attack impact evaluation. It focuses to create a simple common platform to compare cyber intrusion impact among different critical infrastructure using time as a base parameter. The first index is ‘Service Unavailability Cyber Impact Factor (SUCIF)’ having score range from 0 to 1, where 0 indicate cyber disaster and 1 indicates no breach. To estimate the score, detail information regarding system unavailability or malfunctioning is required. It can be used to analyze those systems whose detail cyber-physical infrastructure is not available. The second indicator named ‘Time Based Cyber Impact Factor (TBCIF)’ uses graph-based bad node detection technique to determine the score point similar to SUCIF. For this, optimal time and expected time for incursion detection plays a vital role to generate impact score. This index is suitable for test systems whose physical or cyber layer architecture is known. This research uses SUCIF index to compare hacking impact on Ukrainian Power Grid (UPG) and Saudi Aramco Oil and Gas Company (AOGC). To legitimize TBCIF score, it has been used to compare the intrusion impact of different IEEE test systems. This index is more consistent for the smart grid network.

A reliability assessment for emergency switchgear systems improvementment of LNG plant

The LNG plant essential load to support the operationality is taken from the emergency system. The major challenge is to ensure the reliability level of its emergency system required. The improvement of the emergency system can result in operationality of LNG production. The calculation of component or system unavailability is the essential of the emergency system reliability evaluation. This paper presents a reliability analysis for LNG plant emergency switchgear system by comparing the existing configuration and proposed new configuration. The analysis is using the software modeling with Fault Tree Diagram. Therefore, by the concept of proposed design, it can improve the reliability of emergency system by reducing the unavailability.

DESIGN AND IMPLEMENTATION OF WEB SERVICES FOR THE INTEGRATION OF INFORMATION SYSTEMS FOR THE DISTRIBUTION OF COVID-19 CASES

Several terms are used by the Government to collect data on the spread of covid-19's cases, namely People Under Surveillance (ODP), Patients Under Supervision (PDP), dead and positively infected. The Aceh government provides information on the spread of the covid-19 case through the official website media. Data of the cases are displayed daily based on the reports from districts / cities. District / city governments provide information based on reports from hospitals, health centers and from existing posts in each village. The unavailability of a data collection information system that can be used jointly in recording the spread of Covid-19 cases can lead to data duplication, because data collection is carried out according to individual needs. To overcome this problem, it is necessary to design and build a dissemination information system that can be used jointly between the village posts, sub-district offices, community health center (puskesmas) and hospitals. This research produces a website-based information system prototype for data collection on the spread of Covid-19 cases and API data services in the form of REST web services. Web Services are built using REST web services that generate request and response data using the JSON data format. The web services built can be used for integration with district / city and provincial government information systems, so that data changes can occur in real time.

Education governance in Pakistan: A critical analysis of challenges

The socioeconomic development of a country depends upon a sound education system. The current era of technology increases its demand to survive in this globalized world. However, several drastic measures have been taken by Pakistan’s government but are still unable to acquire the goals and struggle with low literacy. On this account, a critical analysis was done to understand the root causes of bad governance of education and propose suggestions to resolve those challenges. The study specified several challenges such as unequal access to education, insufficient resources, unavailability of trained teachers, scared accountability and examination system, socioeconomic gap and private supplementary education. In accordance with the findings, the study also proposed useful suggestions for policymakers and educationists.

Evaluation of Nonconformity To Pedestrian Safety Measure in Immediate Area of LRT Cawang-Dukuh Atas Construction Site

The practice of providing safe temporary facilities for pedestrians during the execution of infrastructure projects is still challenging due to project complexity and the management of existing traffic flow. The challenge of ensuring pedestrian safety also becomes a concern in Jakarta, Indonesia, which currently has many ongoing infrastructure projects. The execution of these projects along existing main roads demands contractors to close some road lanes including pedestrian accesses. The circumstance highlights the importance of investigating the current practice in providing safe temporary pedestrian access. This study aims to investigate the safety and comfort measure of pedestrian access adjacent to the construction site. Nonconformities to safety findings from the field later are used as a basis for expert interviews in order to acquire recommendations. This research took a case study of the Light Rail Transit (LRT) project with a section length of 3.6 km. Observations took place every 100 meters and all nonconformities to safety data were recorded. Findings showed that among the potential nonconformities to safety, only six of those factors occurred frequently which later became the basis of questionnaire development for semi-structured expert interviews. Three experts from different backgrounds were chosen. Content analysis was used to analyze the data. Field observation result shows that among the six factors of nonconformity to safety, the unavailability of the separator system between the pedestrian access and road lane becomes the most occurred factor. The research demonstrates that in order to provide safety for pedestrians, access should be prepared with a minimum width of 90-100 cm, durable and stable surface, as well as a barrier that ensures safety against traffic and construction work. This study recommends the practical considerations for pedestrian safety as well as policies in terms of contractor’s organization and government in a broader perspective.

Towards 100% visibility in lensless ghost imaging with sunlight

Lensless ghost imaging using sunlight could be used to take a picture of a distant object with features of 130 µm image resolution (the resolution of 130 µm is for a peak wavelength of 500 nm of sunlight). Because of the unavailability of a detection system to distinguish the very wide bandwidth of sunlight, the visibility of the ghost image is very low. This article reports on a study of lensless ghost imaging with sunlight to achieve 100% image visibility by taking advantage of the intensity-fluctuation correlation of sunlight.

Systematic classification of commonly used timber species for finger-joint mixed panels in Sri Lanka

Off-cut wood pieces are often dumped or used as fuel wood. A certain portion of timber has to be removed also due to inadequate length of sawn timber material. Finger joint, a method which connects two small pieces of timber is identified as a sound technique to minimize timber wastage. At the finger joint production process, different timber species are bonded together for making finger-jointed mixed panels. In this connection, the selection of the best possible combination of timber species is vital as the success largely depends on the mechanical and physical properties of the pieces. Workability, on the other hand, is another key factor which minimizes manufacturing defects. However, expansion of the finger joint industry is restricted due to the unavailability of a reliable timber classification system based on wood properties. Therefore, the present study focused on developing a classification system for selected 32 clear timber species based on physical, mechanical and anatomical properties of wood. Factor analysis was used in preparing the Total Wood Index (TWI) and timbers were grouped into four categories as low, medium, high and very high based on TWI. It is recommended for selecting suitable timber species from the TWI-based groups to ensure the best matching thereby the attractive aesthetic appearance in finger-joint manufacturing can be achieved.

Thermal Hydraulic Analysis of a Nuclear Reactor due to Loss of Coolant Accident with and without Emergency Core Cooling System

This paper evaluates the thermal hydraulic behavior of a pressurized water reactor (PWR) when subjected to the event of Loss of Coolant Accident (LOCA) in any channel surrounding the core. The accidental break in a nuclear reactor may occur to circulation pipe in the main coolant system in a form of small fracture or equivalent double-ended rupture of largest pipe connected to primary circuit line resulting potential threat to other systems, causing pressure difference between internal parts, unwanted core shut down, explosion and radioactivity release into environment. In this computational study, LOCA for generation III+ VVER-1200 reactor has been carried out for arbitrary break at cold leg section with and without Emergency Core Cooling System (ECCS). PCTRAN, a thermal hydraulic model-based software developed using real data and computational approach incorporating reactor physics and control system was employed in this study. The software enables to test the consequences related to reactor core operations by monitoring different operating variables in the system control bar. Two types of analysis were performed -500% area break at cold leg pipe due to small break LOCA caused by malfunction of the system with and without availability of ECCS. Thermal hydraulic parameters like, coolant dynamics, heat transfer, reactor pressure, critical heat flux, temperature distribution in different sections of reactor core have also been investigated in the simulation. The flow in the reactor cooling system, steam generators steam with feed-water flow, coolant steam flow through leak level of water in different section, power distribution in core and turbine were plotted to analyze their behavior during the operations. The simulation showed that, LOCA with unavailability of Emergency Core Cooling System (ECCS) resulted in core meltdown and release of radioactivity after a specific time.

Integrated system efficiency in reducing redundancy and promoting residential renewable energy in countries without net-metering: A case study of a SHS in Ghana

One of the key factors affecting progress of renewable energy (RE) in the residential sector in Africa is the unavailability of net-metering systems in many of its member-state countries. Huge battery storage would have to be put in place by individual households owning solar home systems (SHS) to store energy for early morning and night-time use, making the systems not cost-competitive. In this study, a new concept based on “integrated system efficiency (ISE)” has been developed to maximize direct use of electricity from SHS without net-metering. In a case study, real-time power consumption and solar PV electricity generation were monitored for an installed SHS in Ghana. The result showed that, in the absence of net-metering system, sustainable hybrid SHS can be realized if high consumption electrical loads comprising refrigeration systems, water pumping, and washing machines are shifted to daytime use, using ISE. The significant contribution of this study is that, for SHS without net-metering, a new performance parameter called “solar system redundancy factor” is identified as more appropriate indicator for measuring the actual usage of the PV electricity generation. Using the ISE concept developed in this study, the redundancy factor was minimized from 63.2% to 39.8% for the SHS.