IN recent times, the increasing demand of energy, insufficiency of conventional energy sources, such as coal, oil and gas, to meet the energy demand and the increased environmental degradation resulting from the excessive utilisation of conventional resources has triggered the idea of utilisation of renewable energy as a propitious alternative to conventional resources.

Despite the environmental friendliness, the most frequently used renewable energies — solar and wind — have low energy density. Moreover, their instability and weather-dependent intermittency impose limits on stable operation of renewable energy systems.

This causes the output to fluctuate. In the presence of such technical confines, a single renewable energy source is inadequate for the sustenance of a continuous energy supply system. Thus, in order to get around such limitations, the concept of integration of various renewable energy sources is gaining popularity.

Such a hybrid renewable energy system (HRES) is a combination of various energy sources. With its high efficiency, a HRES is regarded as a potential solution to the issues, such as regional distribution, etc. The utilisation of HRES is mainly aimed at ensuring continuous power generation.

HRES is composed of one renewable and one conventional energy source or more than one renewable with or without conventional energy sources that work in a stand-alone capacity. Either one or both of the renewable sources, solar photovoltaic (PV)/wind, can be used in combination with back-up devices, such as batteries. Back-up energy device, also called secondary sources, are introduced into the system to supply the deficit power and to take care of transient load demands.

The primary and secondary sources are used to obtain regulated power output from the sources and to maintain a constant supply. The proper interfacing of power conversion methods and corresponding devices are indeed crucial for the hybrid system. To make the system economically attractive, sustainable and capable of providing continuous energy the coupling of wind and solar PV systems is quite significant.

Furthermore, the integration of biomass energy and geothermal energy is also possible. Such hybridisation of different renewable energy sources has grabbed immense attraction.

The important feature of HRES is thus to combine two or more power generation technologies to make best use of their operating characteristics and to obtain efficiencies higher than that could be obtained from a single power source. HRES are highly useful for water/building heating, power generation, drying, etc.

Moreover, HRES can address limitations in terms of fuel flexibility, efficiency, reliability, emissions and economics. The issues on fiscal feasibility and interconnection are the major challenges for HRES. Recent global boost to renewable energy markets has vividly invigorated research and development in this area.

There is an immediate need for the widespread use of HRES to solve the energy issues and to ensure a green revolution. To accomplish this, the system configuration, specific device, operation procedure and performance studies are essential and must be conducted in a thorough manner.

Dr Intikhab Ulfat
Karachi

Published in Dawn, April 26th, 2022