Global concerns and increase in awareness on the effects on climate change as a result of increased fossil fuel utilization have inspired much research in innovative alternative energy sources and possible counteractive measures. Renewable energy output has been steadily increasing; in fact, in 2017, an estimated 178 GW was added to the global power generating capacity and renewables accounted for an impressive 70%. Incentives and government policies are being put in place so as to de-carbonize energy systems. Consequently, over the last decade renewable electricity generation from solar energy has grown rapidly and hence measures to deal with its non-dispatchable nature. Integrating solar plants in conventional fossil power plants is a widely researched solution to tackle solar energy intermittency. This results in hybrid power plants whose total electricity production consists of two different contributions (solar and fuel-electricity) that can be evaluated by implementing numerical methods based on the so called “with and without solar energy” approach. Nonetheless, such evaluation cannot be carried out in actual power plants operation where fossil and renewable contributions are not discernible from each other within the overall production.
To overcome this limitation, and consequently allow the total electricity generated to be properly partitioned among energy sources, researchers from the Department of Industrial Engineering at University of Rome “Tor Vergata” in Italy: Professor Marco Gambini and Professor Michela Vellini developed an alternative and innovative “on-line and real-time” method to quantitatively assess solar and fuel-electricity by subdividing the overall cycle efficiency into subsequent ones related to the different energy conversion processes during real plant operation. Their goal was to deliver a rigorous yet simple method that could distinguish both solar and fuel-electricity productions based on parameters easily accessible during hybrid power plant operation. Their work is currently published in the research journal, Energy Conversion and Management.
In brief, their work involved; first, the application of the “with and without solar energy” approach for allocation of the total electricity generated to each energy input. Next, the two scientists defined an alternative and innovative “on-line and real-time” procedure, where fossil and solar electricity shares were estimated during real plant operation by subdividing the whole hybrid cycle into subsequent ones. They estimated loss factors in thermodynamic cycles with respect to a Carnot cycle with the same maximum and minimum temperatures; they introduced a new parameter, called “factor of internal losses” able to describe and to quantify internal irreversibilities of any thermodynamic cycle. They proposed a method to calculate this parameter and they demonstrated the validity of the new proposed procedure comparing it with the “with and without solar energy” procedure.
The authors highlighted that unlike “with and without solar integration” approach, implementable exclusively via numerical calculations, the proposed method allowed one to estimate fossil and renewable electricity shares with high accuracy but extended to real plant operations. In addition, they pointed out that by using the new approach, the contribution of solar energy could be assessed rigorously under effective conditions of solar integration.
In summary, the Gambini -Vellini study defined and validated a novel innovative ‘on-line and real-time’ procedure to quantitatively assess fuel and solar generation within hybrid power plants overall electricity production.. In a statement to Advances in Engineering, the two long time research collaborators added that their novel approach offered advantaged in two folds; first, it could be conveniently establish the exact amount of electricity produced by renewable energy sources and thus a public authority can calculate the correct economic support for renewable electricity generation second, each country can ultimately determines renewable target reached supporting this declaration by the application of a rigorous method.
M. Gambini, M. Vellini. Hybrid thermal power plants Solar-electricity and fuel-electricity productions. Energy Conversion and Management, volume 195 (2019) page 682–689.