Renewable energy sources and grid integration in Ghana : issues, challenges and solutions

Abstract: Due to the high cost of fuel and as unfavourable weather conditions which have affected power generation in Ghana, the country has experienced power crises for the past seven years. Renewable Energy Resources (RES) like wind and solar are being considered by many countries as alternatives for the energy requirements of the country. Ghana’s Energy Commission’s (EC) report in October, 2017 indicated that, RE contributes 2MW of power to the country’s energy mix, representing about 1.73% of the total installed capacity. However, the current EC’s energy policy has projected 600MW power through RE in 2030. 340 MW from solar and 260 MW from wind energies. The then Ministry of Energy through the Energy Commission started the rooftop PV programme implementation in early 2016 in some government institutions. The main aim of the rooftop programme was to produce about 200 MW maximum load respite on the national grid as a medium term programme through PV solar technology. However, RE and grid integration has various issues and challenges, large scale RE power generation are mainly connected to the transmission systems and small scale generation are mostly linked with the distribution system. Direct integration these systems poses a lot challenges and issues. This paper examines the main issues and proposes some probable solutions for future RE generations and integration

Analysis of femtocell for better reliability and high throughput

Abstract: An unrelenting need for mobile broadband data has become the norm for end users. Mobile operators are now faced with a challenge to deliver higher data rates thus has prompted developments for new innovations in mobile technology to satisfy this data hungry generation. Poor indoor building penetration have been a major stumbling block in achieving higher data rates as good signal strength of better quality influences higher data rates. Methods to solve indoor penetration problems such as cranking up power on existing base stations can be an alternate but this can potentially introduce high interference to the system and effectively decrease system capacity. Like in any other wireless communication environment, having a transmitter and receiver closer to each other will potentially increase signal strength thus effectively increasing signal quality and potentially higher data rates. This inevitably means more base stations need to be installed to improve coverage. This idea is not feasible ! in practice based on financial constraints using traditional macro and micro sites thus the emergence of FemtoCell seems to be a feasible endeavour. A FemtoCell BS is a self-installed low powered base station connected to the mobile operator via backhaul using IP connection. This device brings a lot of benefits such as Opex savings, increased spectral efficiency, improved battery life and higher data rates for customers resulting from increased signal Strength. In this paper an overview of advancement of cellular networks from legacy standards 2G to 4G-LTE/LTE-A and benefits/challenges of FemtoCell are analysed

Mitigation of impulse noise in powerline systems using ANFIS technique

Abstract: The use of OFDM channel for the transmission of data in power line communication (PLC) system has been of several importance to technology development. However, during transmission, the OFDM channel is greatly disturbed by impulse noise that causes a wrong information to be received. Several techniques such as iteration, coding, clipping and nulling methods have been used to lessen the upshot of impulse noise in OFDM channel. However, these techniques still suffer some drawbacks and require a high signal-to-noise (SNR) power for high performance. This paper presents an advanced use of artificial neuro-fuzzy inference system (ANFIS) technique in removing the complete impulse noise and some of the additive white Gaussian noise (AWGN) that were mixed with the transmitted data in an OFDM channel and using the minimum SNR power. Obtained results propose that ANFIS technique can be used to mitigate impulse noise from a powerline communication channel

Inter-building PLC-VLC integration based on PSK and CSK techniques

Abstract: This paper presents the implementation of an integration technique used to combine power line commu- nications (PLC) and visible light communications (VLC) channels in inter-building scenarios. It considers the narrow band PLC (NBPLC). Phase-shift keying (PSK) is used to convey the information over the PLC link and colour shift keying (CSK) technique is used on the VLC link. The colour wheel method is exploited to map PSK symbols to colours.We define a parameter x, which represents different magnitudes of the PSK complex symbol observed over the PLC channel. x is adjusted to an optimal value to meet the requirement of the CSK design. The bit error rate (BER) is analysed and the performance of the system is presented for multiple values of the modulus of the detected PSK symbol. A practical implementation is performed to verify the PSK-CSK mapping method. The impact of the sun’s rays on the red-green-blue (RGB) symbols is analysed and the interference source is highlighted

The effect of coupling circuits on impulsive noise in power line communication

Abstract: Most researchers in the Power Line Communications (PLC) field have adopted the practice of using idealized impulse noise models directly at the input of the demodulator, as is widely done in simulations. The effect of the coupling circuit on the impulse noise tend to be ignored. However, coupling circuits produce transients. This paper focuses on investigating the effect of the coupling circuit on the impulse noise. Experimental measurements are used to determine the effect of the coupling circuit. An equivalent circuit of the coupling circuit is developed and further simulations are conducted to gain in-depth knowledge on how the impulse noise is affected by the coupling circuit. A literature survey suggests that this topic has not been studied yet

Mitigation of impulsive noise in OFDM channels using ANN technique

Abstract: Orthogonal frequency division multiplexer (OFDM) is a recent modulation scheme used to transmit signals across power line communication (PLC) channel due to its robustness against some known PLC problems. However, this scheme is greatly affected by the impulsive noise (IN) and often causes corruption with the transmitted bits. Different impulsive noise error correcting methods have been introduced and used to remove impulsive noise in OFDM systems. However, these techniques suffer some limitations and require much signal to noise ratio (SNR) power to operate. In this paper, an approach of designing an effective impulsive-noise error-correcting technique was introduced using three-known artificial neural network techniques (Levenberg-Marquardt, Scaled conjugate gradient, and Bayesian regularization). Findings suggest that both Bayesian regularization and Levenberg-Marquardt ANN techniques can be used to effectively remove the impulsive noise present in an OFDM channel and using the least SNR power

Separation of kimberlite from waste rocks using sensor-based sorting at Cullinan Diamond Mine

Abstract: Near-infrared (NIR) spectroscopy sorting technology is incorporated in an automated optical mineral sorter that can discriminate between materials using the differences in characteristics when exposed to near-infrared radiation. During September 2014 to April 2015, a pilot plant that utilized NIR technology to discriminate between kimberlite and waste materials was commissioned to determine the viability of including this technology in the diamond winning process flow sheet at Cullinan Diamond Mine. The plant was used to minimize the waste content in the size fraction -70+35 mm that reports to the crushing section and then to the dense media separation process. This paper describes the initial test work, conducted at Mintek, that led to the decision to conduct a pilot-scale study. The mineralogical characterization of the feed and product streams to establish the sorting criteria and the operational data obtained during the pilot plant campaign are described. The results indicated a good possibility of discriminating between the kimberlite and waste material using NIR technology. However, the consistency of discrimination was not good enough to avoid the risk of potential diamond loss. Furthermore, a lower than expected availability of the machine reduced the throughput capabilities

Good synchronization sequences for permutation codes

For communication schemes employing Frequency Hopping/Multiple Frequency Shift Keying modulation, we present an algorithm for finding good non-binary synchronization sequences, which are permutations, to be used with permutation codes to synchronize/resynchronize data in channels with background noise and interference(frequency jamming/fading). For the synchronization sequences, new analytical expressions for the probability of false acquisition are also given. Using simulation results, we show that our synchronization sequences perform better than some conventional non-binary synchronization sequences, in the presence of background noise and interference

Impulsive Noise Evaluation on PLC-VLC based on DCO-OFDM

Abstract: Power line communications (PLC) and visible light communications (VLC) are two emerging communication technologies which have several similarities. Among them, the advantage related to cost effectiveness is considered as strong research motivation. These two technologies are also characterized by the fact that each one of them barely form a complete communication system without the need of other supporting technologies. In this paper, based on the positive aspect of VLC technology, we exploit the Hermitian symmetry to design an hybrid system combining PLC and VLC technologies using orthogonal frequency division multiplexing (OFDM). A DC biased optical OFDM (DCOOFDM), employed in VLC, is investigated when combined with PSK-OFDM (used in PLC). In the hybrid PLC-VLC system proposed in this paper, we exploit the inherent clipping feature of DCO-OFDM to combat impulsive noise found in the PLC channel, where the optimal combination of the DC bias level for optical communication, DC and impulse noise clipping threshold, Tc are investigated through simulations. We also exploit the fact that both DCO-OFDM and PSKOFDM employ the FFT, to simplify the system