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Clean power when ORC system recovers waste heat

SWEP UK Representation by Dover Intercompany Services UK Ltd News and PR from SWEP UK Representation by Dover Intercompany Services UK Ltd - Published 20 October 2015 An affordable and sustainable supply of energy is the key to modern society as well as global economy.
However, with primary energy production all around us, there has been little focus on using the heat by-products as secondary energy sources. The most cost-effective yet unexploited resource is waste heat.

Many industrial processes are highly energy intensive and release a vast amount of exhaust gases and waste streams. Due to process inefficiencies and the inability of existing technologies to recover the waste heat, a vast deal of the energy used in modern industries is lost, either directly to the atmosphere or to cooling systems. Since the efficiency of generating energy from waste heat depends on the temperature of the waste heat source, it has to date not been practical or economical to recover waste heat to any larger extent. Current technology has limited the process to heat sources of medium- to high temperatures (above 500°F/260°C), when most of the waste has temperatures below 300°F/150°C. However, new technologies are emerging which allow for lower temperatures.

ORC: Financially feasible
One of these emerging technologies, the Organic Rankine Cycle (ORC), lowers the demand on the temperatures, making it economically feasible to recover waste heat and turn it into electricity. The working principle of the ORC is the same as that of the well- established Rankine Cycle describing steam turbine operation in power plants. Confined to a closed circuit, the working fluid is first pumped to a boiler where it is evaporated. When passing through a turbine the organic vapour fluid expands and is finally re-condensed, normally using a closed water loop in the shell-and-tube heat exchanger. The thermodynamic cycle is finished when the condensate is pumped back to the evaporator. Evaporation occurs at high temperature/high pressure side and condensing at low temperature/low pressure side, which is the opposite from the normal refrigeration cycle.

The variety of available working fluids (hydrocarbons or refrigerants) and energy converters, ranging from axial turbines to piston or Wankel expanders, opens up for designing systems with good performance for wide temperature ranges. This also challenges producers of heat exchangers, who need to cover complex combinations of flow capacities, pressures and temperatures in systems extremely sensitive to pressure drop. Historically, this has called for costly and bulky tailor-made solutions. Today, most cases can be solved with mass produced modular brazed plate heat exchangers. These technical advantages allow for simple start/stop procedures, automatic operations, minimum maintenance, good performance at partial loads and very reliable and quiet
Clean power when ORC system recovers waste heat

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