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Session: Parallel Session: Operational Experience I
Session starts: Thursday 22 September, 10:00
Presentation starts: 10:40
Room: Frans van Hasseltzaal

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Hartmut Kiehne ()

Abstract:
Small capacity combined heat and power (CHP) plants are suitable for efficient energy conversion. CHP is arguably the only way to use fuel or thermal energy optimally, and the only way to optimally use fuel or thermal energy and the only way to operate ORC plants efficiently. ORC plants for cogeneration are less electrically efficient than plants designed for electricity generation only, as the higher condensation temperature penalizes the thermodynamic cycle. As a result, investors for electricity-only projects demand ORC plants with higher electrical efficiencies, and manufacturers attempt to fulfill this demand with so-called low-condensing temperature ORC plants. Selecting a suitable ORC fluid can help reducing the condensation temperature and thus increasing the electrical efficiency. However, this rules out cogeneration due to the low condensation temperature. Notably, the assumed improved economy deriving from higher electricity production is often offset by the increased electrical power demand for the condenser cooling. In low-temperature ORC plants for generating electricity only, the condenser is generally cooled by means of air-water coolers. The lower the temperature difference between the condenser cooling water and the ambient temperature, the more electricity is required for cooling, i.e. the assumed advantage of increased electrical efficiency is compensated by the higher system electricity demand. The use of so-called low-condensation temperature ORC plants is not advantageous in projects with no heat requirements, as the system electricity requirement can be reduced significantly via higher condensation temperatures, thus achieving higher net electrical efficiency. As ORC plants are often implemented in areas with higher ambient temperatures, a larger temperature difference between the condenser cooling water and the ambient temperature is beneficial.