Nowadays, conventional coal or gas fired power plants are the dominant way to generate electricity in
the world. In recent years there is a growth in the field of renewable energy sources in order to avoid the
threat of climate change from fossil fuel combustion. Solar energy, as an environmental friendly energy
source, may be the answer to the reduction of global CO2 emissions. This paper presents the concept of
Solar Aided Power Generation (SAPG), a combination of renewable and conventional energy sources
technologies. The operation of the 300 MW lignite fired power plant of Ptolemais integrated with a solar
field of parabolic trough collectors was simulated using TRNSYS software in both power boosting and fuel
saving modes. The power plant performance, power output variation, fuel consumption and CO2 emissions
were calculated. Furthermore, an economic analysis was carried out for both power boosting and
fuel saving modes of operation and optimum solar contribution was estimated.