We have probably all read of hybrid cars and buses powered by a combination of petrol or diesel with batteries. The same approach to making electricity is being taken in the operation of hybrid power plants. Such plants often combine renewables, such as solar or wind power with fossil fuel generation. They are designed to overcome the intermittency of modern renewable energy.
However, still in its infancy, the global market is forecast to reach $1.92 billion by 2019. [i] This is facilitated by increasingly productive renewable technology and falling costs.[ii] These plants are to be found as stand-alone power systems in urban and remote areas, particularly in developing countries where, very often, they augment expensive diesel with solar or wind power. By 2020, combined solar and diesel plants will account for just over half of the world’s hybrid plants.[iii]
What is hybrid power?
Typically, a hybrid power plant combines a reliable fossil fuel such as diesel or gas generation, with an intermittent renewable energy source. This is done to increase system efficiency and provide a better balance of energy supply. Whilst some schemes solely use renewables like wind and solar power, [iv] the majority combine conventional fossil-fuel generation with a renewable, most commonly diesel with wind or solar energy. However, increasingly gas is replacing diesel in many projects.[v] In addition, with the declining cost of batteries, hybrid power plants may include batteries to store surplus power for later use.[vi]
Hybrid power schemes offer a range of benefits including reduced dependence on fossil fuels such as expensive diesel alongside lower operating and maintenance costs. Above all, hybrid power plants provide energy security through a diversity of energy sources and responsiveness to load fluctuations. They ensure a reliable electricity supply[vii] for both private and public customers.
Here are three examples that highlight the current possibilities for using hybrid power plants. One, the Danish city of Aarhus, [viii] is integrating all its renewable and heat generation units with existing conventional power systems. Aarhus is doing this in order to improve energy self-sufficiency, and export surplus power to the grid. Another, is in South Africa, where several mines have converted their existing diesel generation plants into hybrid power operations by adding wind and solar singly or in combination. The Crominet mine, [ix] for example, has added solar PV to provide 60 percent of the 1.6 megawatts of power needed to run this remote mine. This conversion has saved the operators the cost of 3 million litres of diesel fuel a year. Thirdly, in Chile, Enel’s Ollagüe hybrid power plant [x] encompasses a combination of solar, wind and diesel inputs as well as batteries. During the day, surplus renewable power charges the batteries. At night, when battery power is exhausted, diesel kicks in.
According to William Ross Williams, CEO Altresco Companies,[xi] power generation has undergone a transformation. Williams says, “What would have been a 10 million dollar grid control centre a decade ago can now fit on a laptop?” Technological advances in equipment, computing and growing experience are steadily improving the costs of hybrid power plants over more conventional one-mode systems such as diesel alone. Even so, installing the right control systems and optimising the equipment to produce competitively priced energy remains a challenge.[xii]
— By Nicholas Newman, Energy Writer