In industry, there are many sources of low-temperature heat—heat which is often found in connection with waste products such as the hot exhaust gases from a ship’s combustion engine. This waste heat can be used to produce electricity by employing a special technology.
It is possible to get far more energy out of the same amount of diesel fuel. This can be done by employing a new technology which can convert the excess heat into electricity. Because using this technology makes it possible to utilize the share of the energy from the combustion of diesel fuel which is otherwise lost as heat.
In his research project, Jesper Graa Andreasen, PhD student at DTU Mechanical Engineering, focuses on developing and optimizing the new technology called ORC, Organic Rankine Cycle. To utilize the low-temperature sources, the principle behind the ORC technology is to pump a working liquid having a boiling point below that of water into a boiler where it evaporates and is passed through a turbine. Electricity is thus produced by means of the turbine. The working liquid is then passed through a heat exchanger where the liquid condenses and restarts the cycle.
“We’re studying various organic working media in the project to be able to document their different properties and to find the most effective ones,” explains Jesper Graa Andreasen.
“Mixtures of different working media have been shown to give the best results, so we’re working on finding the best compositions.”
The technology is interesting in connection with ship engines, among other things. In a ship engine, a large part of the energy from the combustion of diesel fuel is wasted as heat, for example as heat loss in the exhaust gas. Using waste heat for electricity production makes it possible to utilize the oil even better than is the case today; the electricity produced by the ORC plant can be used for propulsion of the vessel (through a shaft motor) or to cover the power consumption on board the ship (e.g. for cabin lighting, airconditioning, or refrigerated containers), thus making it possible to reduce the consumption of fossil fuels in an industry which accounts for a large share of carbon emissions
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The electricity produced by the ORC plant can be used for the propulsion of the ship via a shaft engine or to cover the power consumption on board the ship for cabin lighting, airconditioning, or for refrigerated containers, thus making it possible to reduce the consumption of fossil fuels. Photo: Ingrid Marie Vincent Andersen.
The waste heat from a ship engine can be used to produce electricity by means of ORC, Organic Rankine Cycle. Photo: Ingrid Marie Vincent Andersen.