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Harvesting Heat

For over one hundred and thirty years people have used heat to create electricity through the combustion of coal, gas or oil, however, this has come at a cost to the environment. Modern thermal generating systems are limited to their ability to utilise heat. For example, steam turbines require steam at specific temperatures and pressures to operate efficiently. If temperatures are not maintained, traditional turbines can be damaged by water condensing inside fast-moving machinery. Internal combustion engines forgo the use of steam for motive force, but leak more than half their heat into the structure of the engine itself and the exhaust products of combustion.

This means that traditional systems for generating electricity can only use 'high grade' heat. Once temperatures or pressures fall, residual heat is diverted to cooling loops that vent in to the atmosphere. Each year, more energy in heat is discarded by the global electricity industry than the energy contained in all the coal burned to create that electricity. Together with solar thermal, geothermal and other industrial sources of energy, heat represents a vast, largely untapped resource.

This thermal resource has remained largely untapped because 'low grade' heat has traditionally been difficult to harvest. New technologies have, however, resulted in some lower temperature heat now being viable and commercially attractive as they are easily transported and applied to remote area power plants.l Harnessing low grade heat also requires the use of specialist equipment which is specific to each situation. One of Enerji's core capabilities is providing the right range of devices in neat, packaged solutions that meet our customers' requirements. Its skid-mounted, containerised equipment modules may use:

  1. a wet steam turbine for heat already carried by steam
  2. a backpressure turbine to extract energy from steam as its pressure is changed for reticulation around a site
  3. an ORC unit for capturing heat from generator exhaust or 'spent' steam that may contain impurities which may be damaging to other equipment.

These are combined with simple, yet sophisticated, interfaces and controls that create a complete power delivery package, capable of working with customers' existing equipment with little or no required supervision or maintenance.

Wet steam turbineWater droplets inside steam turbines can erode the turbine's blades: the outside edges of large turbine blades can reach supersonic speeds. Enerji's wet steam turbines are specifically designed, through lower rotational speed and erosion-resistant internal parts, to resist water droplet erosion and function well with steam at lower temperatures.