(355a) Design and Optimization of Hybrid Geothermal-Solar Power Systems

Mitsos, A., RWTH Aachen University

A semi-detailed model is developed for an existing binary geothermal organic Rankine cycle (ORC). The model is
validated with an available set of measured data for one year operation of the ORC. The performance characteristics
of all the components of the ORC is included in the model. The condensation system of the ORC is of ACC type and
consequently the net output power of geothermal system is limited by ambient temperature. The operation of the
ORC is optimized maximizing the net output power of system. The ORC is hybridized with a solar trough system
with two approaches: (i) solar-heating (ii) solar-cooling. A hybrid  model for  each  approach  is developed  and  implemented  in AspenPlus. The solar system is of trough medium temperature type and is modeled in Aspen Custom Modeler. The solar  system  in nominal  condition  provides  only  7.3  % additional  thermal  energy  to the ORC. 

In the solar-heating approach, a hybridization strategy is offered and its performance is optimized maximizing the net
output power of the system. The optimal operation of this hybrid system suggests between 10-40 % boost in net
output power compared to the geothermal ORC depending on ambient temperature.

The solar-cooling system is of absorption chiller type with water-LiBr as its working fluid (WF) and no optical concentration. The solar cooling system is utilized in parallel with the ACC system. The optimal operation of the hybrid solar-cooling system offers
up to 4% boost in the net output power of the system.