Icarus Hybrid Solar Photovoltaic/Thermal Energy Storage and Power Boosting

M. Anderson, E. Gonzalez
Icarus RT, Inc.,
United States

Keywords: solar photovoltaic, solar thermal, energy storage, thermal energy storage, organic Rankine Cycle, ORC

Summary:

The Icarus project will overcome limitations of solar photovoltaic (PV) by extracting, collecting and storing heat energy to improve power output daily. The proposed technology effectively converts common PV arrays into hybrid photovoltaic/thermal (PV/T) systems using Organic Rankine Cycle (ORC) to increase availability, capacity and output through clean thermal energy storage. The system will generate power from stored heat energy. The safe thermal battery is designed to maintain and provide at least four-hours of power generation at array capacity (i.e., 400-kWh for a 100-kW array) and enable increased integration and operation flexibility without the downsides of traditional batteries. This research will verify using ORC to recover waste heat from PV panels, store thermal energy without consuming photovoltaic power, and generate additional power from recovered low-grade waste heat to match demand. The work includes analysis, design optimization and testing. Focus is on thermal energy storage and on boosting PV array performance in real time. Research includes process simulation using multi-physics computational fluid dynamics modeling and simulation for design verification and optimization of: 1) Thermal energy storage/power generation; 2) PV panel heat extraction; 3) Control and monitoring. Simulations using ASPEN and COMSOL show array power output improvements of 8 to 42% in real time. During POC testing panel cooling up to 5.5oC and power output increase up to 20.8 W (170-watt panels) due to cooling were measured. The PV/T system aims to produce 25% more power (i.e., a 100-kW system will become a 125-kW with Icarus) during production plus four hours on-demand production from storage, at 44% of the cost/kW installed compared to traditional PV with storage. Icarus has designed, built, and is testing proof-of-concept equipment for panel cooling at Icarus Solar Lab with Jacobs School of Engineering at University of California, San Diego. The storage system, the thrust of this research, has not been built or tested. Rudimentary testing reduced panel temperature 2.6oC, and increased power generation up to 20.8W from 170W panels (spot panel temperature reduction up to 5.5oC). Results confirm the feasibility and usefulness of panel cooling. The team measured heat extraction and demonstrated stored fluid heat up as much as 40oF daily. The optimized design is predicted to cool panels 20oC. Anticipated outcomes: 1) Design verification/optimization based on virtual 100kW photovoltaic array, thermal energy extraction and storage using natural stratification to store heat energy for 36 hours to provide at least four hours power at array capacity (i.e., 400kWh on a 100kW array) during peak demand or when needed using ORC; 2) Verification of predicted amount of energy that can be stored and produced (preliminarily estimated at 4 hours at 25kW or 100kWh) and the amount of additional power (estimated to be at least 25% or 25kW) that can be produced using ORC in real time, while charging the thermal battery (i.e., not consuming PV output), and; 3) Determination of the cost benefit (estimated at less than $1/watt installed with storage, compared to $1.85/watt for commercial photovoltaic (PV) without storage).