On-Field Operation and Maintenance of Photovoltaic Systems in Cameroon

The objectives of this work are to examine the causes of the breakdown in the photovoltaic power systems, to propose strategies to solve them, and to evaluate the field lifetime of some elements of the PV systems. The data analyzed were obtained from maintenance records and measurements over a period of 9 years (from 2007 to 2015) for the backup PV systems and 2 years (from 2016 to 2018) for photovoltaic water pumping (PVWPS) systems. It appears from this analysis that 29% of the batteries went bad (leading to curative intervention); this contributed to about 64.9% of the total breakdown registered. Using the failure modes, effects and criticality analysis (FMECA) method for PVWPS, criticality is 252, 402, and 504 for inverters, PV module, and motor pump, respectively. This demonstrates that motor pumps are more sensitive than other elements in the PVWPS. This study also permitted not only to evaluate the quantity of preventive and corrective maintenance impacts on solar PV systems but also to propose maintenance strategies to rapid diagnosis of PV systems

A field study on thermal comfort in naturally - ventilated buildings located in the equatorial climatic region of Cameroon

The purpose of this research is to create a thermal comfort data base in three climatic regions in Cameroon. This will help to define guidelines for constructing more comfortable buildings in Cameroon. There is not enough data regarding comfort in residential environment in the inter tropical sub Saharan Africa. Thus experimental and subjective results of hygrometric thermal comfort conducted in 290 buildings located in three cities of the equatorial climatic zone of Cameroon is presented. An adaptive approach according to ASHRAE55/2004, ISO7730 and 10551 was adopted. A specific questionnaire has been elaborated for the investigation. 710 questionnaires in the dry season and 410 in the rainy season were distributed to inhabitants and filled while different experimental value of indoor parameters were measured. The comfortable temperature ranges for the three cities was found between 22. 1 C and 29.1 C. The 61.24 % of voters found acceptable their thermal habitat, the 13.72% considered it neutral

Effects of Solar Shading on Thermal Comfort in Low-income Tropical Housing

This paper evaluates the effects of solar shading strategies on thermal comfort in low-income tropical housing in Uganda. Dynamic thermal simulations are conductedand the effects of various shading strategies including curtains, roof and window overhangs, veranda and tress on solar heat gain and thermal comfort are investigated.Adaptive approach for naturally ventilated buildings defined by CEN standardis used to assess theconditions in the case study buildings. According to the results, although shading significantly reduces solar heat gain, it is less effective inmeeting thermal comfort requirements in low-income tropical houses. Solar shading is however considerably effective during the hottest periods of the year reducing the risk of extreme overheating by up to 52%.In this respect, a north-south building orientation with the main openings on the north elevation is recommended. Due to excessive solar heat gain, large openings on east- and west-facing walls should be avoided

Design of a new PID controller based on Arduino Uno R3 with application to household refrigerator

A refrigeration system to maintain a desired compartment temperature usually uses a thermostat as an on-off controller. In fact, the thermostat has some disadvantages. The main problem of system which is related to the thermostat is the biggest energy consumption in household appliances. In this paper, to solve the problem was designed a new PID controller based on an Arduino Uno R3 with application to a household refrigerator. In this case, the Arduino Uno was uploaded with PID controller algorithm. Then, in implementation to determine controller parameter values was defined new criteria. After that, to obtain the best refrigeration system performance was also proposed new performance criteria based on experimental data. The experimental results showed that the proposed control system was able to maintain the desired temperature with steady-state error of about 0.044°C. In addition, in steady state the control system for the refrigerator was able to the energy saving of about 30% and it almost did not depend on cooling load quantity

Performance Assessment of Two-parameter Weibull Distribution Methods for Wind Energy Applications in the District of Maroua in Cameroon

Wind speed is the most important parameter to be considered when designing wind energy conversion systems (WECS), since its probability density distribution greatly affects the performance. In this paper, five numerical methods were analysed and their performance evaluated for effectiveness in determining the parameters for the Weibull distribution. Twenty eight years (198

Comparison of Different Models to Estimate Global Solar Irradiation in the Sudanese Zone of Chad

Sustainable future development relies on solar radiation, which is the main source of renewable energy. Thus, in this article, the monthly average global solar irradiation of four sites in the Sudanian zone region of Chad is estimated using different empirical models. The data used in this study were collected at the General Directorate of Meteorology of Chad. The reliability and accuracy of six models estimating global solar radiation were validated and compared by statistical indicators identifying the most accurate model. The results obtained show that the Allen model has the best performance for the Moundou site (5.760 kWh/m²/d, R2=0.843), the Angstrom Prescott model for the Sarh sites (5.658 kWh/m²/d, R2=0.805) and Pala (5.793 kWh/m²/d, R²=0.889), the Sabbagh model for the Bongor site (5.657 kWh/m²/d, R²=0.888). These models are validated against NASA data. The results show that the Sudanian zone of Chad has good solar potential and is therefore suitable for possible exploitation

Indoor comfort and adaptation in low-income and middle-income residential buildings in a Nigerian city during a dry season

This paper investigates occupants' comfort, adaptation and their responses during the dry season in low-income to middle-income residential buildings in Abuja, Nigeria. The study aims to provide empirical data on occupants' comfort through evaluating 171 households in four different locations in Abuja. The study considered a combination of different research methods for data collection. Post-occupancy surveys were used to evaluate the buildings and residents' adaptation within the thermal environment. Thermal comfort surveys were also carried out in eight low-income residential households to assess occupants' perception of the thermal environment. Based on the short duration of the physical measurements, building simulation was also used to examine thermal comfort of occupants for an extended period. The Post Occupancy Evaluation (POE) results revealed over 70% of the occupants were dissatisfied with their thermal environment. The comfort surveys reported similar results with over 65% of the responses revealed being ‘uncomfortably warm’. The results showed an overall mean temperature of all the measured case studies to be 31.7 °C and the average temperature (predicted) of 30.7 °C. The neutral temperatures were in a range of 28°C–30.4 °C compared to the preferred temperature range of 27.5°C–29.4 °C. The prevalence of thermal discomfort highlights the need to explore the possibilities of reducing internal temperatures, particularly by passive means (fabric, shading, insulation etc.) given the need to avoid or reduce the need for air conditioning to make the buildings energy-efficient for low to middle income groups

Multi-Objective Optimisation Framework for Designing Office Windows::Quality of View, Daylight and Energy Efficiency

This paper presents a new, multi-objective method of analysing and optimising the energy processes associated with window system design in office buildings. The simultaneous consideration of multiple and conflicting design objectives can make the architectural design process more complicated. This study is based on the fundamental recognition that optimising parameters on the building energy loads via window system design can reduce the quality of the view to outside and the received daylight – both qualities highly valued by building occupants. This paper proposes an approach for quantifying Quality of View in office buildings in balance with energy performance and daylighting, thus enabling an optimisation framework for office window design. The study builds on previous research by developing a multi-objective method of assessment of a reference room which is parametrically modelled using actual climate data. A method of Pareto Frontier and a weighting sum is applied for multi-objective optimisation to determine best outcomes that balance design requirements. The Results reveal the maximum possible window to wall ratio for the reference room. The optimisation model indicates that the room geometry should be altered to achieve the lighting and view requirements set out in building performance standards. The research results emphasise the need for window system configuration to be considered in the early design stages. This exploratory approach to a methodology and framework considers both building parameters and the local climate condition. It has the potential to be adopted and further refined by other researchers and designers to support complex, multi-factorial design decision-making

Occupant productivity and indoor environment quality: A case of GSAS

© 2017 Purpose: The purpose of the paper is to establish links between Indoor Environment Quality (IEQ) factors that affect occupant productivity and Global Sustainability Assessment System (GSAS) building rating system. The paper analyses the current state of GSAS using a desktop study, survey and brainstorming session organised in a workshop with GSAS Certified Green Professionals (CGP). Methodology/design/approach: The study was conducted in three steps. First, a comprehensive literature review was conducted to identify IEQ factors that influence occupant productivity in offices. The second step was a desktop analysis of current GSAS building rating system to identify criteria and submittals that may help to increase occupant productivity. It was followed by a facilitated workshop of GSAS CGPs that included a survey and a brainstorming session to highlight the current state of GSAS rated building performances on occupant productivity. The workshop was attended by 41 CGPs in Doha, Qatar. Findings: The paper highlighted that GSAS needs to be updated to increase occupant productivity in GSAS rated buildings. A periodic post-occupancy survey in GSAS buildings should be mandated to ensure better occupant productivity. The paper also presented various methods to make GSAS rated buildings more occupant-friendly. Originality/value: This study is the first study to analyse green building guidelines in the context of occupant productivity, especially in Qatar.This research is supported by the Qatar National Research Foundation NPRP NO: 7-344-2-146.Published versio