# Concentrating Solar Collectors for a Trigeneration System--A Comparative Study
## 4 Conclusions  
The goal of this analysis is the investigation of three different solar concentrating technologies in a trigeneration system. Parabolic trough collectors, linear Fresnel reflectors and solar dishes are compared in energetic, energetic and financial terms. The trigeneration unit consists of an ORC and an H\({}_{2}\)O/LiBr absorption chiller for producing cooling and heating. The present investigation is conducted for the weather data of Athens in Greece. The main conclusions of the present paper are included in the next bullets:  
* The PTC is found to be the best technology from an energy and financial point of view. The solar dish is second, with a small difference to the PTC, while the LFR is the least efficient technology.
* The solar dish is able to provide a more uniform production profile throughout the year compared to the other systems.
* The performance of the LFR is extremely low during the winter and it is not recommended to be used in winter applications in Greece.
* The yearly energy performance is found to be 64.40%, 35.78% and 62.41% with the PTC, LFR and dish, respectively.
* The yearly exergy performance is found to be 16.63%, 9.24% and 16.12% with the PTC, LFR and dish, respectively.  
\begin{table}
\begin{tabular}{l c c c} \hline \hline
**Parameters** & **PTC** & **LFR** & **DISH** \\ \hline Electricity production—E\({}_{\text{el}}\) (kWh) & 19,328 & 10,737 & 18,730 \\ Heating production—E\({}_{\text{heat}}\) (kWh) & 50,417 & 28,008 & 48,858 \\ Cooling production—E\({}_{\text{cool}}\) (kWh) & 46,636 & 25,908 & 45,195 \\ Collector heat production—E\({}_{\text{u}}\) (kWh) & 93,361 & 55,331 & 90,622 \\ Solar energy—E\({}_{\text{sol}}\) (kWh) & 180,705 & 180,705 & 180,705 \\ Energy efficiency—\({}_{\text{len}}\) (-) & 64.40\% & 35.78\% & 62.41\% \\ Exergy efficiency—\({}_{\text{lex}}\) (-) & 16.63\% & 9.24\% & 16.12\% \\ Simple payback period—SPP (years) & 6.25 & 10.92 & 6.95 \\ \hline \hline \end{tabular}
\end{table}
Table 4: The final comparative results of the present work.  
* The investment simple payback period is found to be 6.25, 10.92 and 6.95 years with the PTC, LFR and dish, respectively. These results indicate that all cases lead to viable systems.  
Conceptualization, E.B.; methodology, E.B.; software, E.B.; formal analysis, E.B.; investigation, E.B.; writing--original draft preparation, E.B. and C.T.; writing--review and editing, E.B. and C.T.; supervision, C.T. All authors have read and agreed to the published version of the manuscript.  
This research is co-financed by Greece and the European Union (European Social Fund--ESF) through the Operational Programme <<Human Resources Development, Education and Lifelong Learning>> in the context of the project \"Reinforcement of Postdoctoral Researchers--2 nd Cycle\" (MIS-5033021), implemented by the State Scholarships Foundation (IKY).  
[PERSON] would like to thanks the State Scholarships Foundation (IKY) for its financial support (MIS-5033021).  
The authors declare no conflict of interest.  
el electricity en energy evap_in evaporator inlet evap_out evaporator outlet ex exergy f fluid heat heating LFR Linear Fresnel reflector loss storage tank losses mg electromechanical protocol PTC Parabolic trough collector sol solar st storage sun sun thermal thermal u useful Abbreviations EES Engineering Equation Solver HRS Heat Recovery System IAM Incident angle modifier LFR Linear Fresnel Reflector ORC Organic Rankine Cycle PTC Parabolic Trough Collector SD Solar Dish