Organic Rankine Cycle |
Expanding applications in geothermal power and LNG regasification
An EXERGY perspective
When it comes to producing useful power from low- to medium-temperature heat sources of moderate capacity the Organic Rankine Cycle (ORC) has a strong track record in various applications, thanks to its high efficiency due to the low boiling point and high vapour pressure of the organic working fluid (relative to the water employed in the conventional steam cycle).
Geothermal power applications One ORC application already well established and attracting increasing interest is geothermal energy. ORC technology provider Italy-based EXERGY International (now part of the Chinese TICA group) and STRABAG Umwelttechnik GmbH have recently entered into a partnership agreement with the aim of developing, building and operating turn-key ORC-based geothermal power plants. The initial focus is Germany – one of the largest and most rapidly evolving markets for geothermal power plants in Europe – with expansion of the partnership to other markets, in particular central and south-eastern Europe, where STRABAG Group is well established, also under consideration in the medium term. Strabag has already built a turn-key geothermal power plant employing ORC technology in Germany, in Garching an der Alz (for Silenos Energy), while in the area of advanced binary
geothermal power plants, EXERGY is the world’s second largest ORC technology provider and can boast a project portfolio amounting to around 450 MW of installed capacity.
EXERGY has also recently signed a partnership agreement with GDI (Geothermal Development and Investment Inc) for provision of turn-key ORC based geothermal power plants in Japan (estimated to have the world’s third largest potential geothermal market).
A distinguishing feature of EXERGY’s ORC system is the use of its patented multi-pressure- level Radial Outflow Turbine. Developed by EXERGY and introduced to the market in 2009, this allows multiple admission pressures to be accommodated with a single turbine disc (rather than requiring one turbine per pressure level, as traditionally employed in geothermal binary systems). Among the benefits are increased efficiency and power output.
A recently inaugurated EXERGY project on Mindanao island in the Philippines has seen an ORC system deployed to recover otherwise wasted heat from the return brine flow of two existing geothermal flash power plants, Mindanao 1 and 2. The new ORC based system, Mindanao 3, generates an additional 3.6 MWe. The Mindanao units are owned and operated by EDC, the world’s largest vertically integrated
exchanger Heat Preheater Recuperator
Air cooled condenser
Pump
Above: ORC process scheme, with ACC, for waste heat recovery
geothermal energy producer, boasting over 40 years of history and over 1180 MW of geothermal capacity in its portfolio. The new ORC based brine waste heat recovery power plant is its first such facility.
It was designed and supplied by EXERGY in less than 12 months, including successfully passing the performance test and compliance testing by the system operator, National Grid Corporation of the Philippines.
EXERGY sees many further opportunities for ORC deployment in geothermal brine waste heat recovery projects, considering that there are more than 10 GW of flash steam turbine geothermal power plants installed worldwide, of which over 6 GW employ single flash technology and are thus suitable for brine recovery .
Cold energy recovery for LNG As well as enabling power generation from low grade heat that would otherwise be wasted, in, for
Turbine Evaporator
Organic vapour out
Generator
Organic vapour in
Left and above: EXERGY Radial Outflow Turbine
22 | June 2022|
www.modernpowersystems.com
Generator
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