Douala being the economic capital of Cameroon has many industries located within the Bassa and Bo... more Douala being the economic capital of Cameroon has many industries located within the Bassa and Bonaberi areas. In this paper, the power quality and disturbances are analysed on the Douala 90 kV electrical network and the 380/220 V distribution system. Network disturbance statistics are given over the past few years. Different back-up levels within the Douala area are investigated too.
Recently, thermal energy storage (TES) has received increasing attention for its high potential t... more Recently, thermal energy storage (TES) has received increasing attention for its high potential to meet cities' need for effective and sustainable energy use. Traditionally, energy was stored in the form of sensible heat which requires large volume of storage material. The storage volume can be significantly reduced if energy is stored in the form of latent heat and thus can benefit enormously practical applications. The existing approaches in the design, integration and application of phase change materials (PCMs) in domestic hot water tanks (HWT) and transpired solar collector (TSC) using water/air as the heat transfer media are reviewed. Crucial influencing factors are considered, including thermo-physical properties of different PCMs, different configurations of PCMs in HWT and TSC, and the limitations of each technique. This paper also discusses the existing simulation, design tools and experimental studies related to PCMs usage in HWT and central thermal storage.
2007 9th International Conference on Electrical Power Quality and Utilisation, 2007
Sub-Saharan African countries are today confronted with the problem of urban and demographic grow... more Sub-Saharan African countries are today confronted with the problem of urban and demographic growths thus needing to reach a sustainable rate of positive economic growth. In order to meet this sustainability, many reforms are being carried out among which is the energy sector which will lead to future energy supply in an open globalised energy market as well as providing the basic energy needs. One of such methods involves the use of distributed generation (DG) which is always located closed to consumption points for rapid electrification. How ever, the use of DG involves the need of a stable network which most often is lacking in Sub-Saharan African countries thus growing concern of DG on their loosely integrated grids.
An optical evaluation and analysis of an internal low-concentrating evacuated tube heat pipe sola... more An optical evaluation and analysis of an internal low-concentrating evacuated tube heat pipe solar collector designed to enhance the collection of solar radiation for medium temperature applications is presented in this paper. The internal low-concentrating evacuated tube heat pipe solar collector was designed with an acceptance angle of 20 given a geometrical concentration ratio of 2.92. The truncation of the upper part of the reflector giving a geometrical concentration ratio of 1.95 was carried and enabled the internal low-concentrating evacuated tube heat pipe collector to be enclosed by a borosilicate glass tube with 100 mm and 93 mm outer and inner diameters, respectively. Ray trace analysis at different transverse angles determines optical efficiencies, related optical losses and flux distribution on the absorber of the internal low-concentrating evacuated tube heat pipe solar collector. A detailed two dimensional ray trace techniques considering only the direct insolation component predicated overall ray's acceptance of 93.72% and optical efficiency of 79.13% from transverse angles of 0 to 20 .
Heat transfer fluids (HTFs) play an essential role in solar water heating systems by transferring... more Heat transfer fluids (HTFs) play an essential role in solar water heating systems by transferring collected energy from the collector, perhaps via a heat exchanger to the store. If the store is at a much higher temperature than the fluid, the store acts as a heat source, ...
Performance evaluation of internal concentrator augmented solar collectors is presented. Two diff... more Performance evaluation of internal concentrator augmented solar collectors is presented. Two different heat extraction methods were used and experimental collection efficiency provided. To reduce heat loss, augmented concentrators were evacuated. Heat pipe augmented concentrators proves better than to direct flow augmented concentrators.
Two profiles of concentrated evacuated tube heat pipe solar collectors made of single-sided and d... more Two profiles of concentrated evacuated tube heat pipe solar collectors made of single-sided and doublesided absorber have been analyzed and compared under control conditions and results presented in this paper. These innovative concentrated evacuated tube heat pipe solar collectors were experimentally tested at a tilt angle of 60°to the horizontal. Using indoor solar simulated experimental conditions temperature response, collection efficiency, heat loss coefficients and energy collection rates as well as the incident angle modifier (IAM) were recorded and compared at five different transverse angles (0-40°) at 10°increments. The use of concentrated single-sided and double-sided absorber evacuated tube heat pipe solar collectors is seen to be feasible for integrating solar thermal energy into buildings for heating demands. The concentrated double-sided absorber evacuated tube heat pipe proves better compared to the concentrated single-sided absorber evacuated tube heat pipe solar collector due to higher outlet temperature with greater temperature differential and improved thermal performance. The integration of this innovative system implies that the number of the evacuated tube heat pipe collectors needed to attain higher temperature is reduced. Furthermore, the size of reflectors and related reflector losses are reduced due to the truncated nature of the reflectors providing a low concentration ratio.
International Journal of Energy Technology, Aug 29, 2019
The millions of users in developing countries often live far off the electric grid (rural areas) ... more The millions of users in developing countries often live far off the electric grid (rural areas) which seems not very cost effective extending the national grid to these rural areas as per respective governments. Africa’s total primary energy supply has seen an increasing annual rate of about 3%, seeming to be the highest among all other continents. The African continent as a whole is endowed with large renewable energy potential, varying in type across diverse geographic locations. These resources, and the settings in which they exist, can point to country or regional specific renewable energy solutions to fit each nation’s strengths and needs. In Sub-Saharan Africa, reliable access to electric power must be consider a basic precondition to improve people’s lives as it further promote education, health care and economic growth via the creation of sustainable and clean energy jobs. Until recently, renewable energy technologies (RETs) have been confronted with a huge up-front cost and technologies in development but massive and global deployment of renewable energy systems has led to significant cost reductions and performance improvements and the hope is to see increasing uptake of RETs by African countries. Cameroon a Central African country is heavily reliant on hydropower, which contributes an estimated 60% to the country’s total installed 1,400MW capacity in 2015. In addition, there is constants power failure due to the non-reliability of the electric grid and load shedding to meet increasing demand. However, climate change poses additional huge risk (large reservoirs and dams drying up) and to meet the increasing demand, Cameroon is being forced to seek alternative power sources. This paper proposes the need for a sustainable hybrid energy system design and the development of an effective design, simulation and analysis approach of stand-alone off-grid in Cameroon as a potential optimal solution to help power community electrical loads. Finding an optimized mix of renewable energy technologies for Bandjoun and Muyuka were the goals of this paper.
The paper describes the system and experimental evaluation of an evacuated tube heat pipe collect... more The paper describes the system and experimental evaluation of an evacuated tube heat pipe collector array augmented with a novel design internal concentrator having a direct flow absorber and tested in the north-south and east-west align configurations under real outdoor conditions. External and internal concentrators have the potential to supply higher generator inlet temperatures needed for solar driven cooling systems. However, internal concentrator augmented solar collectors can further reduce heat losses and increase output temperatures. It is shown that collector outlet temperatures of 110°C or more is possible and can be efficiently used to drive solar cooling systems with higher coefficient of performance (COP). The evacuated tube collector array augmented with a novely designed internal concentrator having a direct flow absorber in the north-south alignment was found to be more energy efficient with larger temperature lift and outlet and inlet temperature differential and substantial improvement in thermal performance compared to its east-west align configuration due to shorter connection piping connecting the internal concentrator augmented CPC to the evacuated tube heat pipe collector array.
Standard energy systems for individual dwellings nowadays are still mostly conventional in North ... more Standard energy systems for individual dwellings nowadays are still mostly conventional in North America and other places. Heat generation for a larger part is commonly met by using mostly natural gas while the use of renewable energy systems to replace fossil fuels is starting to become widespread, especially in Alberta, Canada, which is an oil driven region. It is of interest to evaluate the seasonal performance of a hybrid thermal energy system at NAIT, which is being used to meet the heating needs of the lab space in the D building and aid for teaching purposes. Seasonal performance of a hybrid thermal energy system (geo-exchange, solar thermal energy systems and air source heat pumps) at NAIT, will help analyse and describe the concepts and the parameters affecting the design and optimization of a heat source hybrid energy system, identify key parameters to help determine the optimal design of individual component as part of a larger system; highlight year-to-year performance o...
Until recently, renewable energy technologies (RETs) have been confronted with a huge up-front co... more Until recently, renewable energy technologies (RETs) have been confronted with a huge up-front cost due to technologies in development. However, massive and global deployment of renewable energy systems has led to significant cost reductions and performance improvements and the hope is to see increasing uptake of RETs by African countries. Cameroon a central African country is heavily reliant on hydropower, which contributes an estimated 60% to the country’s total installed 1,400MW capacity in 2015. In addition, there is constants power failure due to the non-reliability of the electric grid and load shedding to meet increasing demand and or to relieve stress on the primary energy source when demand for electricity is greater than the primary power source can supply. However, climate change poses additional huge risk (large reservoirs and dams drying up) and to meet the increasing demand, Cameroon is being forced to seek alternative power sources. In January 2014, Cameroon welcomed ...
To reduce greenhouse gas emission, solar cooling is an attractive and environmentally friendly ap... more To reduce greenhouse gas emission, solar cooling is an attractive and environmentally friendly application since there is a direct match with cooling demand and peak incident solar radiation. In addition, solar absorption refrigeration technologies are regarded as a promising way to meet the growing refrigeration needs related to thermal comfort, vaccines, conservation of foods and medicines as well as crop drying. Presently, two systems in common used are, the single and double effects absorption chillers with the difference between the two systems being the operating temperature range. This comprehensive review looks at the available methods (theoretical modeling/simulation and experimental) that have been used for the powering of single and double effects solar absorption chillers, other solar cooling systems and their merits, system integration, design optimization and cost effectiveness of each system.
Being a cost effective solar application, Transpired Solar Collector (TSC) system has been widely... more Being a cost effective solar application, Transpired Solar Collector (TSC) system has been widely used in North America and Europe. In order to estimate the energy performance of TSC system, software programs such as RETScreen and SWift are currently available. These software programs’ empirical models are specifically designed for the analysis of TSC. However, TSC estimation tools have rarely been critically analysed by other researchers. This paper introduces a new estimation tool for modelling the energy performance of building integrated TSC. The program is called SBET (Sustainable Building Estimation Tool). This paper focuses on three parts of calculation algorithms, i.e. the capture of solar energy delivered, together with destratification and insulation savings. The calculation algorithms for these savings are presented here together with an explanation of their derivation. Lastly, the TSC thermal performance results of SBET estimation tool is compared with those of currently available software programs, using a consistent benchmark design parameters and weather data.
Douala being the economic capital of Cameroon has many industries located within the Bassa and Bo... more Douala being the economic capital of Cameroon has many industries located within the Bassa and Bonaberi areas. In this paper, the power quality and disturbances are analysed on the Douala 90 kV electrical network and the 380/220 V distribution system. Network disturbance statistics are given over the past few years. Different backup levels within the Douala area are investigated too.
The continuous increase in disturbances on the Cameroon Southern interconnected electric power sy... more The continuous increase in disturbances on the Cameroon Southern interconnected electric power system resulting in its inability to reliably meet demands due to improperly protected and old unmaintained transmission and distribution systems, insufficient investment and upgrade of infrastructures. Furthermore, rapid load growth and low water levels of the reservoirs create much stress on the power balance problem and on the existing transmission lines. In this paper, a protection system for transmission lines using series capacitors is discussed in detail.
The performances of solar water heating systems have improved steadily over recent years due to i... more The performances of solar water heating systems have improved steadily over recent years due to improved component quality and design. Solar water heating systems in Northern Maritime climates, however, are still not viable economically. In order to make a significant impact on the domestic hot water heating market, solar water heaters must be innovative, cost-effective, and adaptable for retro-fit installation. This paper investigates experimentally the performance of a novel heat exchanger (the “Solasyphon”) designed and developed for external connection to an existing traditional single-coil hot water cylinder. The connection of the novel heat exchanger to an existing system reduces the cost of installation as it avoids the need to replace the existing single-coil hot water cylinder with a twin-coil system. However, the connection of this Solasyphon to a solar water heating system has negative effects on heat losses especially at higher temperatures based on the size of the solar...
Douala being the economic capital of Cameroon has many industries located within the Bassa and Bo... more Douala being the economic capital of Cameroon has many industries located within the Bassa and Bonaberi areas. In this paper, the power quality and disturbances are analysed on the Douala 90 kV electrical network and the 380/220 V distribution system. Network disturbance statistics are given over the past few years. Different back-up levels within the Douala area are investigated too.
Recently, thermal energy storage (TES) has received increasing attention for its high potential t... more Recently, thermal energy storage (TES) has received increasing attention for its high potential to meet cities' need for effective and sustainable energy use. Traditionally, energy was stored in the form of sensible heat which requires large volume of storage material. The storage volume can be significantly reduced if energy is stored in the form of latent heat and thus can benefit enormously practical applications. The existing approaches in the design, integration and application of phase change materials (PCMs) in domestic hot water tanks (HWT) and transpired solar collector (TSC) using water/air as the heat transfer media are reviewed. Crucial influencing factors are considered, including thermo-physical properties of different PCMs, different configurations of PCMs in HWT and TSC, and the limitations of each technique. This paper also discusses the existing simulation, design tools and experimental studies related to PCMs usage in HWT and central thermal storage.
2007 9th International Conference on Electrical Power Quality and Utilisation, 2007
Sub-Saharan African countries are today confronted with the problem of urban and demographic grow... more Sub-Saharan African countries are today confronted with the problem of urban and demographic growths thus needing to reach a sustainable rate of positive economic growth. In order to meet this sustainability, many reforms are being carried out among which is the energy sector which will lead to future energy supply in an open globalised energy market as well as providing the basic energy needs. One of such methods involves the use of distributed generation (DG) which is always located closed to consumption points for rapid electrification. How ever, the use of DG involves the need of a stable network which most often is lacking in Sub-Saharan African countries thus growing concern of DG on their loosely integrated grids.
An optical evaluation and analysis of an internal low-concentrating evacuated tube heat pipe sola... more An optical evaluation and analysis of an internal low-concentrating evacuated tube heat pipe solar collector designed to enhance the collection of solar radiation for medium temperature applications is presented in this paper. The internal low-concentrating evacuated tube heat pipe solar collector was designed with an acceptance angle of 20 given a geometrical concentration ratio of 2.92. The truncation of the upper part of the reflector giving a geometrical concentration ratio of 1.95 was carried and enabled the internal low-concentrating evacuated tube heat pipe collector to be enclosed by a borosilicate glass tube with 100 mm and 93 mm outer and inner diameters, respectively. Ray trace analysis at different transverse angles determines optical efficiencies, related optical losses and flux distribution on the absorber of the internal low-concentrating evacuated tube heat pipe solar collector. A detailed two dimensional ray trace techniques considering only the direct insolation component predicated overall ray's acceptance of 93.72% and optical efficiency of 79.13% from transverse angles of 0 to 20 .
Heat transfer fluids (HTFs) play an essential role in solar water heating systems by transferring... more Heat transfer fluids (HTFs) play an essential role in solar water heating systems by transferring collected energy from the collector, perhaps via a heat exchanger to the store. If the store is at a much higher temperature than the fluid, the store acts as a heat source, ...
Performance evaluation of internal concentrator augmented solar collectors is presented. Two diff... more Performance evaluation of internal concentrator augmented solar collectors is presented. Two different heat extraction methods were used and experimental collection efficiency provided. To reduce heat loss, augmented concentrators were evacuated. Heat pipe augmented concentrators proves better than to direct flow augmented concentrators.
Two profiles of concentrated evacuated tube heat pipe solar collectors made of single-sided and d... more Two profiles of concentrated evacuated tube heat pipe solar collectors made of single-sided and doublesided absorber have been analyzed and compared under control conditions and results presented in this paper. These innovative concentrated evacuated tube heat pipe solar collectors were experimentally tested at a tilt angle of 60°to the horizontal. Using indoor solar simulated experimental conditions temperature response, collection efficiency, heat loss coefficients and energy collection rates as well as the incident angle modifier (IAM) were recorded and compared at five different transverse angles (0-40°) at 10°increments. The use of concentrated single-sided and double-sided absorber evacuated tube heat pipe solar collectors is seen to be feasible for integrating solar thermal energy into buildings for heating demands. The concentrated double-sided absorber evacuated tube heat pipe proves better compared to the concentrated single-sided absorber evacuated tube heat pipe solar collector due to higher outlet temperature with greater temperature differential and improved thermal performance. The integration of this innovative system implies that the number of the evacuated tube heat pipe collectors needed to attain higher temperature is reduced. Furthermore, the size of reflectors and related reflector losses are reduced due to the truncated nature of the reflectors providing a low concentration ratio.
International Journal of Energy Technology, Aug 29, 2019
The millions of users in developing countries often live far off the electric grid (rural areas) ... more The millions of users in developing countries often live far off the electric grid (rural areas) which seems not very cost effective extending the national grid to these rural areas as per respective governments. Africa’s total primary energy supply has seen an increasing annual rate of about 3%, seeming to be the highest among all other continents. The African continent as a whole is endowed with large renewable energy potential, varying in type across diverse geographic locations. These resources, and the settings in which they exist, can point to country or regional specific renewable energy solutions to fit each nation’s strengths and needs. In Sub-Saharan Africa, reliable access to electric power must be consider a basic precondition to improve people’s lives as it further promote education, health care and economic growth via the creation of sustainable and clean energy jobs. Until recently, renewable energy technologies (RETs) have been confronted with a huge up-front cost and technologies in development but massive and global deployment of renewable energy systems has led to significant cost reductions and performance improvements and the hope is to see increasing uptake of RETs by African countries. Cameroon a Central African country is heavily reliant on hydropower, which contributes an estimated 60% to the country’s total installed 1,400MW capacity in 2015. In addition, there is constants power failure due to the non-reliability of the electric grid and load shedding to meet increasing demand. However, climate change poses additional huge risk (large reservoirs and dams drying up) and to meet the increasing demand, Cameroon is being forced to seek alternative power sources. This paper proposes the need for a sustainable hybrid energy system design and the development of an effective design, simulation and analysis approach of stand-alone off-grid in Cameroon as a potential optimal solution to help power community electrical loads. Finding an optimized mix of renewable energy technologies for Bandjoun and Muyuka were the goals of this paper.
The paper describes the system and experimental evaluation of an evacuated tube heat pipe collect... more The paper describes the system and experimental evaluation of an evacuated tube heat pipe collector array augmented with a novel design internal concentrator having a direct flow absorber and tested in the north-south and east-west align configurations under real outdoor conditions. External and internal concentrators have the potential to supply higher generator inlet temperatures needed for solar driven cooling systems. However, internal concentrator augmented solar collectors can further reduce heat losses and increase output temperatures. It is shown that collector outlet temperatures of 110°C or more is possible and can be efficiently used to drive solar cooling systems with higher coefficient of performance (COP). The evacuated tube collector array augmented with a novely designed internal concentrator having a direct flow absorber in the north-south alignment was found to be more energy efficient with larger temperature lift and outlet and inlet temperature differential and substantial improvement in thermal performance compared to its east-west align configuration due to shorter connection piping connecting the internal concentrator augmented CPC to the evacuated tube heat pipe collector array.
Standard energy systems for individual dwellings nowadays are still mostly conventional in North ... more Standard energy systems for individual dwellings nowadays are still mostly conventional in North America and other places. Heat generation for a larger part is commonly met by using mostly natural gas while the use of renewable energy systems to replace fossil fuels is starting to become widespread, especially in Alberta, Canada, which is an oil driven region. It is of interest to evaluate the seasonal performance of a hybrid thermal energy system at NAIT, which is being used to meet the heating needs of the lab space in the D building and aid for teaching purposes. Seasonal performance of a hybrid thermal energy system (geo-exchange, solar thermal energy systems and air source heat pumps) at NAIT, will help analyse and describe the concepts and the parameters affecting the design and optimization of a heat source hybrid energy system, identify key parameters to help determine the optimal design of individual component as part of a larger system; highlight year-to-year performance o...
Until recently, renewable energy technologies (RETs) have been confronted with a huge up-front co... more Until recently, renewable energy technologies (RETs) have been confronted with a huge up-front cost due to technologies in development. However, massive and global deployment of renewable energy systems has led to significant cost reductions and performance improvements and the hope is to see increasing uptake of RETs by African countries. Cameroon a central African country is heavily reliant on hydropower, which contributes an estimated 60% to the country’s total installed 1,400MW capacity in 2015. In addition, there is constants power failure due to the non-reliability of the electric grid and load shedding to meet increasing demand and or to relieve stress on the primary energy source when demand for electricity is greater than the primary power source can supply. However, climate change poses additional huge risk (large reservoirs and dams drying up) and to meet the increasing demand, Cameroon is being forced to seek alternative power sources. In January 2014, Cameroon welcomed ...
To reduce greenhouse gas emission, solar cooling is an attractive and environmentally friendly ap... more To reduce greenhouse gas emission, solar cooling is an attractive and environmentally friendly application since there is a direct match with cooling demand and peak incident solar radiation. In addition, solar absorption refrigeration technologies are regarded as a promising way to meet the growing refrigeration needs related to thermal comfort, vaccines, conservation of foods and medicines as well as crop drying. Presently, two systems in common used are, the single and double effects absorption chillers with the difference between the two systems being the operating temperature range. This comprehensive review looks at the available methods (theoretical modeling/simulation and experimental) that have been used for the powering of single and double effects solar absorption chillers, other solar cooling systems and their merits, system integration, design optimization and cost effectiveness of each system.
Being a cost effective solar application, Transpired Solar Collector (TSC) system has been widely... more Being a cost effective solar application, Transpired Solar Collector (TSC) system has been widely used in North America and Europe. In order to estimate the energy performance of TSC system, software programs such as RETScreen and SWift are currently available. These software programs’ empirical models are specifically designed for the analysis of TSC. However, TSC estimation tools have rarely been critically analysed by other researchers. This paper introduces a new estimation tool for modelling the energy performance of building integrated TSC. The program is called SBET (Sustainable Building Estimation Tool). This paper focuses on three parts of calculation algorithms, i.e. the capture of solar energy delivered, together with destratification and insulation savings. The calculation algorithms for these savings are presented here together with an explanation of their derivation. Lastly, the TSC thermal performance results of SBET estimation tool is compared with those of currently available software programs, using a consistent benchmark design parameters and weather data.
Douala being the economic capital of Cameroon has many industries located within the Bassa and Bo... more Douala being the economic capital of Cameroon has many industries located within the Bassa and Bonaberi areas. In this paper, the power quality and disturbances are analysed on the Douala 90 kV electrical network and the 380/220 V distribution system. Network disturbance statistics are given over the past few years. Different backup levels within the Douala area are investigated too.
The continuous increase in disturbances on the Cameroon Southern interconnected electric power sy... more The continuous increase in disturbances on the Cameroon Southern interconnected electric power system resulting in its inability to reliably meet demands due to improperly protected and old unmaintained transmission and distribution systems, insufficient investment and upgrade of infrastructures. Furthermore, rapid load growth and low water levels of the reservoirs create much stress on the power balance problem and on the existing transmission lines. In this paper, a protection system for transmission lines using series capacitors is discussed in detail.
The performances of solar water heating systems have improved steadily over recent years due to i... more The performances of solar water heating systems have improved steadily over recent years due to improved component quality and design. Solar water heating systems in Northern Maritime climates, however, are still not viable economically. In order to make a significant impact on the domestic hot water heating market, solar water heaters must be innovative, cost-effective, and adaptable for retro-fit installation. This paper investigates experimentally the performance of a novel heat exchanger (the “Solasyphon”) designed and developed for external connection to an existing traditional single-coil hot water cylinder. The connection of the novel heat exchanger to an existing system reduces the cost of installation as it avoids the need to replace the existing single-coil hot water cylinder with a twin-coil system. However, the connection of this Solasyphon to a solar water heating system has negative effects on heat losses especially at higher temperatures based on the size of the solar...
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Papers by Dan Nkwetta