Hybrid Energy Systems

by Clint Ouma

The word hybrid is used to refer to something made by combining different elements [1]. Modern science has seen dramatic advances in hybrid technology, giving birth to hybrid cars such as the Toyota Prius [2] and incorporating information and communications technology (ICT) systems that automate smart-houses and eco homes.

Similarly, hybrid energy systems have been designed to generate electricity from different sources, such solar panels and wind turbines.

Hybrid energy systems often consist of a combination between fossil fuels and renewable energy sources, and are used in conjunction with energy storage equipment (batteries).

This is often done either to reduce the cost of generating electricity from fossil fuels or to provide back up for a renewable energy system, ensuring continuity of power supply when the renewable energy source fluctuates.

One of the biggest downfalls of renewable energy is that energy supply is not constant [3]; sources like solar and wind power fluctuate in intensity due to the weather and seasonal changes [3].

Therefore, a reliable backup system is necessary for renewable energy generating stations that are not connected to a national power grid.

These systems consist of a variety of power control methods and storage equipment which include battery banks and diesel generators among others.

The power systems that are connected to the national grid don’t have this problem because, in most cases, there are many different sources of power contributing to the national electricity supply.

Different Hybrid Power Technologies

There are several types of hybrid energy systems such as wind-solar hybrid, solar-diesel, wind-hydro and wind-diesel.

The design of a system or the choice of energy sources depends on several considerations.

The factors affecting the choice of hybrid power technology can also tell us why people use hybrids and some of the advantages. The main factors are cost and resources available.

The cost hybrid power technology greatly affects the choices people make, particularly in developing countries.

This also depends on the aim of the project. People who are planning to set up a hybrid energy project for their own use often focus on lowering the total investment and operational costs while those planning to generate electricity for sale focus on the long-term project revenue.

As such, systems that incorporate hydrogen storage and fuel cells [4] [5] are not very common with small scale projects. The viability of one hybrid energy system over another is usually pegged on the cost of generating each kilowatt.

The availability of the natural resources plays an enormous part when selecting the components of a hybrid energy system – the right power generation location and method must be chosen.

Often, a hybrid system is opted for because the existing power resource is not enough to generate the amount of power needed – which is often the case when using micro-hydro plants.

In some developing countries, such as parts of Ethiopia, a wind-solar hybrid power system, consisting of wind turbines and solar photovoltaics was found to be most viable. This was because the wind resource alone was not sufficient to meet the electric load. Solar P.V. cells were very expensive, so it wasn’t feasible for the project developers to use solar power alone [6].

Hybrid systems are most suitable for small grids and isolated or stand-alone systems as hybrid power generation is, by definition, a solution for getting around problems where one energy source isn’t sufficient.

The popularity of hybrid energy systems has grown so much that it is now a niche-industry in itself – with custom systems being engineered for specific functions. For instance, Enercon, a German wind power company, has come up with unique factory-designed hybrid power technology, including the world’s first hybrid wind-diesel powered ship, the E-Ship 1 [7].

Article References

[1] Oxford English Mini dictionary ISBN 0-19-860255-3

[2] Toyota – Prius V Specs: http://www.toyota.com/priusv/specs.html

[3] Zero emission Project – The Problem of Renewable Energy Fluctuation by Lorenzo Polidori, May 2010: http://zeroemissionproject.com/blog/article/27/the-problem-of-renewable-energy-fluctuation

[4] U.S. Department of Energy – Fuel Cells Technologies Program: https://www1.eere.energy.gov/hydrogenandfuelcells/pdfs/doe_h2_fuelcell_factsheet.pdf

[5] M. Khan, M. Iqbal; Pre-feasibility study of stand-alone hybrid energy systems for applications in Newfoundland – Memorial University of Newfoundland St. John’s Canada June 2004: Elsevier Renewable Energy Issue 30 (835 – 854).

[6] Feasibility for a standalone Solar-Wind-Based hybrid energy system for application in Ethiopia by Getachew Bekele and Bjorn Palm Department of Energy, KTH, Stockholm, Sweden; Elsevier – Applied Energy 87 (487-495) 2010.

[7] Got Powered – Enercon E-Ship 1: Wind-powered ship: http://gotpowered.com/2011/enercon-e-ship-1-wind-powered-ship/

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