Organic Rankine Cycle (ORC)
Project DescriptionEnergy recovery system for low temperature heat sources.
The Kaymacor ORC project was born from the request of Kaymacor srl, which at the time was prototyping a machine for the recovery of energy from “waste” heat available at low temperatures (100-200° C). One of the possibilities to exploit these energy sources, which often come from the heat generation, or are a side product of an industrial process, is to use fluid machines called Organic Rankine Cycle. Although the method is relatively well-known and used in medium- or large-sized plants, there are very few solutions on the market for low power levels (from a few kW to a few tens of kW), a range that is usually defined as “micro generation”.
Koala Electronics is a partner of Kaymacor for all the electronic part of the ORC machine (now in production), from the power conversion to the control, visualization and user interface. The customization of the various parts allows our partners, such as Kaymacor, to have electronic boards on which functionalities can be expanded or reduced by selectively mounting electronic parts, as well as to use control software and interfaces specific to the target application. In particular the control action, the work sequences of the machine and the monitoring of process variables are implemented to specification. Thanks to the range of internal skills, Koala Electronics is able to provide support to the modelling and implementation of algorithms and control logics for different types of machinery, including fluid machines such as ORCs.
In the ORC application, the machinery consists of the actual ORC machine and a combination of power conversion and external interfaces. The ORC machine includes a device for the absorption of heat (from various sources, such as waste hot fluid or solar thermal) and an expander that, by cooling the fluid through a heat exchanger, generates mechanical power and moves the synchronous three-phase permanent magnet (PMSM) electric generator. The electrical power generated is brought to a DC bus by means of an inverter, operating from a perfectly controlled rectifier, i.e. with a sinusoidal current of controlled amplitude (it follows that the braking torque will be controlled). The control of the electric machine is “sensorless”, i.e. it does not require a rotor position sensor. The power available in DC is then fed into the grid through a single-phase inverter, suitably equipped with filters and real-time controlled. The electrical power conversion and high-speed control functions are implemented in an iPCS (Integrated Power Converter System) device.
The interfaces to the outside world are either via communication buses such as CAN (internal, for control and supervision and external for any remote control), or via a HMI card, which allows a user to view real-time machine parameters and interaction through commands or parameter settings. The supervisor (SVS card) controls the entire machine, interfacing with both the converter (iPCS) and the display (HMI).