The present paper investigates a Kalina cycle using low-temperature heat sources to produce power. The main heat source of the cycle is provided from flat solar collectors. In addition, an external heat Source is connected to the cycle, which corresponds to 5% up to 10% of the total thermal energy supplied to the cycle. The cycle operates at low pressure levels (0.2-4.5 bar) and low maximum temperature (130 C) The NH3 mass fraction at the turbine inlet varies along with the expansion pressure and the effects on the cycle efficiency are studied. For given conditions, an optimum range of vapor mass fractions and operating pressures can be identified that result in optimum cycle performance. Simple equations have been derived that link the operational parameters with the independent variables as well as with the cycle efficiency. (C) 2008 Elsevier Ltd. All rights reserved.