Introduction from: Dr Markides of Clean Energy Process at Imperial College London (ICL)
The OTELLO™ Power Box thermal hydraulic generator (THG) is a heat engine system owned by IIL, with significant similarities to their MOREAMPS Power Box THG system. Both systems are based on sound thermodynamic and operational principles, and can be used to recover waste heat in order to produce useful work and generate electricity. They both comprise a "refrigerant circuit", which contains the working fluid (liquid-vapour) that undergoes a thermodynamic cycle similar to a Rankine cycle, and a "hydraulic circuit‟ that transforms the displacement work output from the piston or bladder accumulator in the refrigerant circuit to electrical power. In this document we focus on the OTELLO™ Power Box THG system.
The OTELLO™ Power Box cycle, as described in previous literature, comprises: isentropic compression, followed by constant pressure and then constant volume heat addition, followed by isentropic expansion, and finally constant pressure heat rejection. In the OTELLO™ Power Box THG system heat is obtained from a bath of hot liquid that acts as an intermediary heat store between the external waste heat source and the system. This is expected to make the OTELLO™ Power Box THG a relatively versatile system, in that it will be possible to adapt with relative ease to a diverse range of waste heat sources. On the other hand, the MOREAMPS Power Box THG system does not use a thermal bath. Here, the working fluid is externally heated and vaporised as it flows through heat exchanging components before entering the piston or bladed accumulators where it expands displacing the hydraulic fluid and producing mechanical work. Both THG systems can also be powered by solar heat.
An advantage of both the OTELLO™ Power Box and MOREAMPS Power Box THG systems is their use of standard components available from international suppliers such as Hydac and Honeywell. The THG systems can be constructed entirely from off-the-shelf components. Using standard components lowers the overall cost, but also allows the warranties and replacement of parts to be covered by the suppliers. At the heart of these systems are the "pneumatic hydraulic accumulators".
