The present study aims to develop a novel optimal design of hybrid energy systems based on exergy and lifecycle concepts using genetic algorithms. The model consists of both stand-alone and on-grid options with scenarios for exchanging energy with the grid. The objectives include cost minimization or benefit maximization primarily

and lifecycle exergy efficiency

i.e.

cost as the sustainability index secondarily. This research considers renewable sources such as solar

wind

hydropower

and hydrogen production and storage in addition to conventional diesel generators. The optimization was performed subject to weather conditions and solar radiation profiles

demand

and environmental or economic aspects. Also

the model contains various modules such as water-heating

waste energy utilization

as well as the options of power exchange with the distribution network and injection of hydrogen produced from excess renewable sources into the gas network. The application was demonstrated in a case study

where specific demands and the climate of Tehran were assumed. The case study considers four scenarios

including standalone

completely on-grid

on-grid with a non-backup generator

and on-grid without an energy sale option. The first optimal objective

the levelized unit cost of energy for the standalone system

is $0.22 per kWh. Moreover

the second optimal objective

the lifecycle exergy cost

ranges from 1.93 to 4.13 in different grid-connection states.