## 3 Materials and Methods  
### Description of the System  
This study considers the solar-integrated CCHP system described by [PERSON] et al. [5]. The system comprises three gas turbines, two compressors, a Kalina cycle, absorption chiller, solar collectors, heat recovery steam generator unit (HSRG) and a hot water generator (Figure 2). Figure 2: Diagram illustrating the solar-integrated CCHP system. The system is operated in such a way that air is compressed by two two-stage compressors (AC-1 and AC-2) with an intercooler in between them. Waste heat from the intercooler is used to drive the absorption chiller via transfer of heat in a desorber. Following that, the air leaving the second compressor is heated through air preheater 1 (APH-1) and air preheater 2 (APH-2), powered by solar energy and exhaust combustion gases from gas turbine 3 (GT-3), respectively. Once the air warms up to the required temperature and pressure, it is reacted with combustion fuel (methane) to produce hot gases in the combustion chamber. The hot gases flow into three consecutive gas turbines, where the first two turbines supply the power needed to drive the compressors while the third is responsible for rotating the shaft of a generator to generate electrical power. Furthermore, exhaust gases from GT-3 are recovered back to the APH-2 and are used to provide heating power to the HSRG, the Kalina cycle through evaporator 1 (Eva-1), and to the domestic water heat exchanger, before being released to the environment. In the Kalina cycle, pump 1 increases the pressure of its working fluid (ammonia water mixture), which is then passed into two successive heat exchangers (low temperature recuperator (LTR) and high-temperature recuperator (HTR)) to improve its thermal energy and reduce the energy input to Eva-1 subsequently. The resulting two-phase mixture at Eva-1 is sent to the separator where separation into saturated vapour and saturated liquid occurs. The saturated vapour is supplied to the steam turbine to generate further work output while the saturated liquid is sent back to the HTR to recover some thermal energy before being passed to expansion valve 1 (Ev-1) where its pressure is reduced. Subsequently, the low-pressure saturated liquid enters the mixer where it is combined with the output from the steam turbine. This mixture is passed through the LTR to dissipate its energy before being discharged to the atmosphere through the condenser (cond-1), thus completing the cycle. A series of processes is employed in the single-effect absorption chiller to acquire energy at the desorber (provided by rejected gases from the intercooler) used to supply cooling capacity at the associated evaporator (Eva-2). The working fluid (saturated LiBr-H\({}_{2}\)O liquid) is pumped into pump 2 before its entrance into the solution heat exchanger (SHE) where it gains thermal energy. In water vapour state, the working fluid enters the condenser (cond-2) from the desorber and condenses into saturated liquid before being throttled from the expansion valve (Ev-3) into Eva-2. At Eva-2, it gains energy to become a saturated vapour before being absorbed into the solution in Ev-2, where it transforms back into the saturated liquid specified at the start of the cycle. The following assumptions were made--that the system operates in a steady state; kinetic and potential energy changes are negligible; and heat losses from component systems, except the combustion chamber, are insignificant. Response Surface Method  
This is a mathematical and statistical approach that aims to determine the design factor settings in order to enhance the accurate implementation of a procedure [41]. The regression models generated portray the relationship between a certain response variable and the associated design factors. The general procedures undertaken are:  
* Design of experiments: This is carried out to establish the experimental conditions. It involves selecting the relevant input factors that would affect the response variable.