Siemens offers ORC for waste heat at 300°C

The Siemens Organic Rankine Cycle (ORC) module enables owners/operators of industrial plants to generate power from waste heat with temperatures of around 300° Celsius.

The ORC process uses an organic working medium obtained from the group of silicon oils with a substantially lower vaporization enthalpy than water. The vaporized oil is used to drive a steam turbine.

Siemens’ initial ORC module employs a model SST-060 steam turbine. The ORC modules currently offered by Siemens have a capacity of up to 2 megawatts (MW), but the company is planning to expand the ORC product portfolio to higher capacities over the medium term.

The ORC-Module essentially comprises the turbine (with generator), recuperator with condenser combined in a functional unit, feed pump, pre-heater(s), evaporator and the interconnecting piping. The vapor produced in the evaporator is supplied to the ORC-turbine which drives the generator. After leaving the turbine the vapor enters the recuperator to transfer the energy from the superheated exhaust vapor to the liquid side of the process. Afterwards it is condensed in the condenser. Cooling water supplied by the customer is used for the condensing process.

The condensate collected in the condenser hotwell is discharged by the feed pump back to the evaporator via pre-heater(s). The speed of the feed pump is controlled via a frequency converter to maintain the level in the condenser hotwell. For start-up and (emergency) shutdown purposes a bypass system is included.

Arrangement Concept Example

In below shown example, the base frame connects the evaporator and pre-heaters to one functional unit whereas; the turbine and the generator are on a separate turbine frame as an extra functional unit.The recuperator is directly placed on the foundation and the feed pump is located in a separate room or cellar below the ORC-Module. This construction is necessary due to the requirements of the feed pump. Small modules below approx. 700 kW are completely placed on one common base frame.*

Main characteristics of the working medium:

• Low freezing point and high temperature stability
• High heat of vaporization and density
• Low environmental impact
  • Ozone depletion potential (ODP) £ 0
  • No global warming potential
• Safety
  • The fluid is non-corrosive, and non-toxic
• Good availability and low cost