The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

Solar Engineering Of Thermal Processes

Hybrid energy systems are being utilized for supplying electrical energy in urban, rural and remote areas to overcome the intermittence of solar and wind resources. A hybrid renewable energy system incorporates two or more electricity generation options based on renewable energy or fossil fuel unit. The techno-economic analysis of the hybrid system is essential for the efficient utilization of renewable energy resources. Due to multiple generation systems, hybrid system analysis, is quite complex and requires to be analyzed thoroughly. This requires software tools for the design, analysis, optimization, and economic viability of the systems. In this paper, 19 softwares with their main features and current status are presented. The softwares studied are HOMER, Hybrid2, RETScreen, iHOGA, INSEL, TRNSYS, iGRHYSO, HYBRIDS, RAPSIM, SOMES, SOLSTOR, HySim, HybSim, IPSYS, HySys, Dymola/Modelica, ARES, SOLSIM, and HYBRID DESIGNER. The research work related to hybrid systems carried out using these softwares at different locations worldwide is also reviewed. The main objective of the paper is to provide the current status of these softwares to provide basic insight for a researcher to identify and utilize suitable tool for research and development studies of hybrid systems. The capabilities of different softwares are also highlighted. The limitations, availability and areas of further research have also been identified.

Review of software tools for hybrid renewable energy systems

Public awareness of the need to reduce global warming and the significant increase in the prices of conventional energy sources have encouraged many countries to provide new energy policies that promote the renewable energy applications. Such renewable energy sources like wind, solar, hydro based energies, etc. are environment friendly and have potential to be more widely used. Combining these renewable energy sources with back-up units to form a hybrid system can provide a more economic, environment friendly and reliable supply of electricity in all load demand conditions compared to single-use of such systems. One of the most important issues in this type of hybrid system is to optimally size the hybrid system components as sufficient enough to meet all load requirements with possible minimum investment and operating costs. There are many studies about the optimization and sizing of hybrid renewable energy systems since the recent popular utilization of renewable energy sources. In this concept, this paper provides a detailed analysis of such optimum sizing approaches in the literature that can make significant contributions to wider renewable energy penetration by enhancing the system applicability in terms of economy.

Optimum design of hybrid renewable energy systems: Overview of different approaches

Renewable energy becomes a key contributor to our modern society, but their integration to power grid poses significant technical challenges. Power quality is an important aspect of renewable energy integration. The major power quality concerns are: 1) Voltage and frequency fluctuations, which are caused by noncontrollable variability of renewable energy resources. The intermittent nature of renewable energy resources due to ever-changing weather conditions leads to voltage and frequency fluctuations at the interconnected power grid. 2) Harmonics, which are introduced by power electronic devices utilized in renewable energy generation. When penetration level of renewable energy is high, the influence of harmonics could be significant. In this paper, an extensive literature review is conducted on emerging power quality challenges due to renewable energy integration. This paper consists of two sections: 1) Power quality problem definition. Wind turbines and solar photovoltaic systems and their power quality issues are summarized. 2) Existing approaches to improve power quality. Various methods are reviewed, and the control-technology-based power quality improvement is the major focus of this paper. The future research directions for emerging power quality challenges for renewable energy integration are recommended.

Emerging Power Quality Challenges Due to Integration of Renewable Energy Sources

Simulation and Implementation of Micro Hydro Generation for Small Rural Loads

The main focus is to model and simulate the portion located in the ULMAZI suburb of the Durban municipality network incorporating FACTS devices, in order to improve the stability of the whole network. Instead of doing modeling and simulation for each generator while they all have the same characteristics, a simplified dynamic model of a power system is used in this study, named Single Machine Infinite Bus (SMIB) power system. This model consists of a single synchronous generator connected through a parallel transmission line to a very large network which is UMLAZI approximated by an infinite bus. For the design purpose, the model of example power system which is a SMIB power system installed with the TCSC device and SSSC connected in series is developed in MATLAB/Simulink. Simulation results in terms of power system responses prove the enhancement of power system performance and fast damping of power system oscillation.

Modeling and simulation of Umlazi suburb of Durban municipality network (South Africa)

A model of electricity cost minimization is proposed which can be implemented in small farming activities where boreholes are present for water supply. In this case, a hybrid system composed of solar photovoltaic and pico hydro supplied by a pumped storage system are used minimize the electricity cost in a dynamic electricity pricing environment. The varying price of electricity, the load demand, the reservoir state of water stored as well as the solar resource at any instant determine the optimal power flow from the different power sources to the load; these are the control variables to be optimised with the aim of reducing the power consumed from the grid. The optimization problem can be solved using linear programming. The system can be implemented in real-time to investigate the impact of the proposed model on the electricity cost reduction of small loads in the South African farming sector.

Using PV with borehole pumped hydro storage systems for small farming activities in South Africa

Hybrid PV-Wind with Groundwater Pumped Hydro Storage System for Electricity Cost Minimization

Wastewater treatment plants (WWTPs) require a significant a significant amount of energy to operate. Currently, several opportunities for energy recovery and electricity generation purpose in wastewater treatment plants have been studied and implemented. This paper presents a case study of implementing a hydropower system at the Zeekoegat wastewater treatment plant. The WWTP is situated in the north-east of Tshwane, South Africa, and using such set up to generate power has not yet been implemented in the country. The WWTP’s electrical load demand, the water resources as well as the potential energy that can be recovered using the proposed hydropower plant has been evaluated to determine to projected cost savings over a proposed operation period of 20 years. The economic analysis shows that the breakeven point occurs after 6, 35 years at $ 327600.Fortheprojected20years,thepotentialcostsavedis $ 1 437 554, 98 which corresponds to 45, 63% of the total amount that would have been consumed if the grid is used as the sole supply.

Kanzumba Kusakana

Papers

Simulation and Implementation of Micro Hydro Generation for Small Rural Loads

Modeling and simulation of Umlazi suburb of Durban municipality network (South Africa)

Using PV with borehole pumped hydro storage systems for small farming activities in South Africa

Hybrid PV-Wind with Groundwater Pumped Hydro Storage System for Electricity Cost Minimization

Hydropower Energy Recovery from Wastewater Treatment Plant: Case of Zeekoegat Plant