1 Introduction

In recent times, environmental risks and energy production issues have prompted nations around the world to begin implementing initiatives that focus on creating and using renewable energy sources. There has also been a global push to reduce the current amount of fossil fuels being used (Ratlamwala and Dincer 2013; Ahmadi et al. 2013). This is because fossil fuels are known to release lethal pollutants that are extremely harmful to the environment. Therefore, the application of alternate energy sources such as geothermal, solar, hydropower, nuclear energy, and wind energy is an important step for the future (Ahmadi et al. 2013; Khalid et al. 2015; Kaviri et al. 2013). Solar energy, in particular, has become one of the most popular alternative energy sources because it is free and does not harm the environment (Atikol et al. 2013). Today, there are many power plants which are being run using solar energy. When looking into the different ways of creating power with solar energy, there are a variety of techniques. These include solar towers, solar dishes, and parabolic trough solar collectors (PTSCs). PTSCs have been used in large power plants since the 1980s. Nowadays, many thermal solar power plants choose to work with PTSCs (Al-Sulaiman et al. 2012). A PTSC has been selected for this system because it is able to increase the heat transmission at a faster rate.

Many researchers have worked on the multi-generation systems. Suleman et al. (2014) developed a novel multi-generation system that integrated geothermal and solar. Their results showed that the overall exergetic efficiencies of ORC 1 and 2 are 82.3 and 77.1%, respectively, whereas the energetic efficiencies are 38.3 and 23.2%, respectively. Exergetic COP of the absorption cooling cycle was 0.41, while the energetic COP was 0.77. Furthermore, the overall exergetic efficiency of the cycle was 76.4%, and the energetic efficiency of the system was 54.7%. In their study, Ozturk and Dincer (2013) presented a multi-generation system based on solar and studied energy and exergy analyses. The organic Rankine cycle efficiency was found 13.51%, Rankine cycle efficiency was calculated as 40.94%, utilization system efficiency and hydrogen production were determined as 21.30%, and absorption cycle efficiency was found 32.75%. Energy efficiency of the system was determined as 52.71%, while exergy efficiency of the cycle was determined as 57.35%. Absorption, organic Rankine, Rankine, and hydrogen production and utilization cycles had exergy efficiencies of 14.31, 19.62, 44.88, and 20.32%, respectively. Bicer and Dincer (2015) have designed and analyzed an integrated system for syngas, bitumen, electricity, and hydrogen production at the same time with steam-assisted gravity drainage and underground coal gasification. The proposed system highlights the significance of multi-generation systems. In their study, energy efficiencies of components were determined as 75% for UCG process and 50% for Brayton cycle. Exergy and energy efficiencies of the overall system were 17.3 and 19.6%, respectively. Khalid et al. (2015) developed a new renewable system-based multi-generation through energy and exergy analysis. The overall exergy and energy efficiencies of the proposed system, which use solar energy and biomass, were 39.7 and 66.5%, respectively; on the other hand, the exergy and energy efficiencies were 37.6 and 64.5%, respectively, when the system operated with only biomass, while they were 44.3 and 27.3% when the system operated with only solar.

In this study, the solar power plant is integrated with a dryer and an electrolyzer, as well as SEAS, which generates hot water, heat, dry air, cooling, hydrogen, and electricity. This study proposes a new multi-generation system that uses new working fluids involving 58NaCl_42MgCl2 for parabolic trough solar collector cycle, LiBr–water for the single-effect absorption system (SEAS), and R134a for the drying cycle. As previously stated, this system can be used in the future in the residential sector in places such as hotels.

2 System Description

According to Fig. 1, the system consists of five subsystems such as a single-effect absorption system, a parabolic trough solar collector, a dryer, an electrolyzer, and an organic Rankine cycle (the main productions of the system are dry air, heating, cooling, electricity, hot water, and hydrogen). Solar energy was selected as the source of energy for this study. The parabolic trough collector consists of two components such as collector and receiver, and the heat engine is selected to collect the thermal energy of the solar radiation. The 58NaCl_42MgCl2 is selected as a molten salt to use as a working fluid in PTSC cycle. The organic Rankine cycle consists of six components including a heat exchanger, a pump, a turbine, a condenser, and a steam generator. The working fluid which is in ORC should have high temperature to certify an efficient process. The isobutane is selected as the working fluid for ORC due to the high thermal capabilities and easy availability. Moreover, R134a and LiBr–water are selected as working fluids in the dryer cycle and absorption chiller, respectively.

Fig. 1
figure 1

Schematic diagram of the multi-generation system

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In this system, solar collectors collect the thermal energy from the sun by circulating molten salt throughout the cycle. When the molten salt is processed in the cycle, it attracts the thermal energy from the sun and becomes hot. Once it has captured the heat, the molten salt will disperse a high-temperature transfer to the isobutene, which is the working fluid in the organic Rankine cycle. This process runs the turbine to produce electricity and can eventually create hydrogen production as well. Moreover, the heat can be transferred to the single-effect absorption system by the generator, which can run the SEAS and produce hot water, cooling, and dry air.

3 Thermodynamic Analysis

In this paper, the following assumptions are made:

  • Air is treated as an ideal gas.

  • The reference environment state has a temperature of \(T_{0} = 297\) K and a pressure of \(P_{0} = 101\) kPa.

  • The turbine is adiabatic.

  • The heat exchangers do not have any heat losses.

  • The pressure losses in all heat exchangers and pipelines are negligible.

  • Moreover, the solar multi-generation system is supposed to operate in a steady-state condition.

According to Dincer and Rosen (2012), the balanced equations for mass, energy, and exergy are defined for major components. Also, coefficients of performance (COP) are determined for the SEAS.

3.1 Rankin Cycle

3.1.1 Turbine

Mass, energy, and exergy balances for the turbine can be written as follows:

$$\dot{m}_{15} = \dot{m}_{16}$$
(1)
$$\dot{m}_{15} h_{15} = \dot{m}_{16} h_{16} + \dot{w}_{T}$$
(2)
$$\dot{m}_{15} ex_{15} = \dot{m}_{16} ex_{16} + \dot{w}_{T} + \dot{E}xd_{T}$$
(3)

3.1.2 Condenser i

Mass, energy, and exergy of the condenser i can be calculated from:

$$\dot{m}_{16} = \dot{m}_{17}$$
(4)
$$\dot{m}_{16} h_{16} + \dot{m}_{25} h_{25} = \dot{m}_{17} h_{17} + \dot{m}_{26} ex_{26} + \dot{Q}_{ci}$$
(5)
$$\dot{m}_{16} ex_{16} + \dot{m}_{25} ex_{25} = \dot{m}_{17} ex_{17} + \dot{m}_{26} ex_{26} + \dot{Q}_{ci} \left( {1 - \frac{{T_{0} }}{{T_{ci} }}} \right) + \dot{E}xd_{ci}$$
(6)

3.1.3 Pump ii

Mass, energy, and exergy balances for the pump ii can be written as follows:

$$\dot{m}_{18} = \dot{m}_{19}$$
(7)
$$\dot{w}_{pii} = \dot{m}_{18}\times v_{18} (p_{19} - p_{18} )$$
(8)
$$\dot{m}_{18} ex_{18} + \dot{w}_{pii} = \dot{m}_{19} ex_{19} + \dot{E}xd_{pii}$$
(9)

3.1.4 Heat Exchanger i

Mass, energy, and exergy of the heat exchanger i can be calculated from:

$$\dot{m}_{9} + \dot{m}_{19} = \dot{m}_{10} + \dot{m}_{20}$$
(10)
$$\dot{m}_{19} h_{19} + \dot{Q}_{HEXi} = \dot{m}_{20} h_{20}$$
(11)
$$\dot{m}_{9} ex_{9} + \dot{m}_{19} ex_{19} = \dot{m}_{20} ex_{20} + \dot{m}_{10} ex_{10} + \dot{E}xd_{HEXi}$$
(12)

3.1.5 Steam Generator

Mass, energy, and exergy balances for the steam generator can be written as follows:

$$\dot{m}_{8} + \dot{m}_{20} = \dot{m}_{9} + \dot{m}_{15}$$
(13)
$$\dot{m}_{20} h_{20} + \dot{Q}_{SG} = \dot{m}_{15} h_{15}$$
(14)
$$\dot{m}_{20} ex_{20} + \dot{Q}_{SG} \left( {1 - \frac{{T_{0} }}{{T_{SG} }}} \right) = \dot{m}_{15} ex_{15} + \dot{E}xd_{SG}$$
(15)

3.1.6 Generator

Mass, energy, and exergy of the generator can be determined from:

$$\dot{m}_{12} = \dot{m}_{13} + \dot{m}_{6}$$
(16)
$$\dot{m}_{17} h_{17} = \dot{m}_{18} h_{18} + \dot{Q}_{G}$$
(17)
$$\dot{m}_{17} ex_{17} = \dot{m}_{18} ex_{18} + \dot{Q}_{G} \left( {1 - \frac{{T_{0} }}{{T_{G} }}} \right) + \dot{E}xd_{G}$$
(18)

3.2 Absorption Chiller Cycle

3.2.1 Heat Exchanger ii

Mass, energy, and exergy of the heat exchanger ii can be calculated from:

$$\dot{m}_{11} + \dot{m}_{13} = \dot{m}_{12} + \dot{m}_{14}$$
(19)
$$\dot{m}_{11} h_{11} + \dot{Q}_{HEXii} = \dot{m}_{12} h_{12}$$
(20)
$$\dot{m}_{11} ex_{11} + \dot{m}_{13} ex_{13} + \dot{Q}_{HEXii} \left( {1 - \frac{{T_{0} }}{{T_{HEXii} }}} \right) = \dot{m}_{12} ex_{12} + \dot{m}_{14} ex_{14} + \dot{E}xd_{HEXii}$$
(21)

3.2.2 Condenser ii

Mass, energy, and exergy balances for the condenser ii can be written as follows:

$$\dot{m}_{6} = \dot{m}_{7}$$
(22)
$$\dot{m}_{6} h_{6} = \dot{m}_{7} h_{7} + \dot{Q}_{cii}$$
(23)
$$\dot{m}_{6} ex_{6} = \dot{m}_{7} ex_{7} +\dot Q_{cii} \left( {1 - \frac{{T_{0} }}{{T_{cii} }}} \right) + \dot{E}xd_{cii}$$
(24)

3.2.3 Pump i

Mass, energy, and exergy of the pump i can be determined from:

$$\dot{m}_{3} = \dot{m}_{11}$$
(25)
$$\dot{w}_{pi} = \dot{m}_{15} (h_{11} - h_{3} )$$
(26)
$$\dot{m}_{3} ex_{3} + \dot{w}_{pi} = \dot{m}_{11} ex_{11} + \dot{E}xd_{pi}$$
(27)

3.2.4 Evaporator

Mass, energy, and exergy balances for the evaporator can be written as follows:

$$\dot{m}_{2} = \dot{m}_{5}$$
(28)
$$\dot{m}_{2} h_{2} + \dot{Q}_{eva} = \dot{m}_{5} h_{5}$$
(29)
$$\dot{m}_{2} ex_{2} + \dot{Q}_{eva} \left(\frac{{T_{0} }}{{T_{eva} }} - 1\right) = \dot{m}_{5} ex_{5} + \dot{E}xd_{eva}$$
(30)

3.2.5 Absorber

Mass, energy, and exergy of the absorber can be calculated from:

$$\dot{m}_{4} + \dot{m}_{5} = \dot{m}_{3}$$
(31)
$$\dot{m}_{4} h_{4} + \dot{m}_{5} h_{5} = \dot{m}_{3} h_{3} + {\dot{Q}_{abs} }$$
(32)
$$\dot{m}_{4} ex_{4} + \dot{m}_{5} ex_{5} = \dot{m}_{3} ex_{3} + \dot{Q}_{abs} \left(1 - \frac{{T_{0} }}{{T_{abs} }}\right) + \dot{E}x d_{abs}$$
(33)

3.3 Drying Process

$$\dot{Q}_{Dryer} = \dot{m}_{29} *h_{29} - (\dot{m}_{30} *h_{30} + \dot{m}_{water} *h_{water} )$$
(34)
$$\eta_{Dryer} = \frac{{ \dot{m}_{30} *h_{30} }}{{\dot{Q}_{Dryer} }}$$
(35)

3.4 Electrolyzer

$$\dot{m}_{{H_{2} }} = \frac{{\eta_{elec} * \dot{w}_{net} }}{HHV}$$
(36)

where \(\eta_{elec}\) is 0.56 and HHV (higher heating value of hydrogen) is 235.15 (kJ/g-mol).

3.5 The Energetic COP of Absorption Chiller

$$COP_{En} =\, \frac{{\dot{Q}_{eva} + \dot{Q}_{Cii} }}{{\dot{Q}_{G} + \dot{w}_{Pi} }}$$
(37)

3.6 The Exergetic COP Absorption Chiller

$$COP_{En} = \frac{{\dot{EX}_{eva} + \dot{EX}_{Cii} }}{{\dot{EX}_{G} + \dot{w}_{Pi} }}$$
(38)

3.7 The Energetic Efficiency of ORC

$$\eta_{ORC} = \frac{{\dot{W}_{net} }}{{\dot{Q}_{in} }}$$
(39)

3.8 The Exergetic Efficiency of ORC

$$\varPsi_{ORC} = \frac{{\dot{W}_{net} }}{{\dot{EX}_{in} }}$$
(40)

4 Results and Discussion

Comprehensive energy and exergy analysis of the system has been done, and the results are given in Tables 1 and 2. A comparative study was carried out using results found in similar studies. The effects of energy and exergy efficiency of the components were compared to other similar studies (Islam et al. 2015; Ozlu and Dincer 2015; Ozturk 2012), and respectable agreements are created. In particular, the exergy destruction of some components is compared with the Ozturk system (2012), and the results are shown in the Table 3.

Table 1 Comparison of the exergy destruction of the current study with previous study
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Table 2 Outputs of the system
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Table 3 Thermodynamic properties of the system at each state point
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As it is shown in the Table 1, the exergy destruction of the components is less than previous study. All modelings have been carried out by Engineering Equation Solver (EES) software.

4.1 Effect of Turbine Inlet Pressure on Efficiencies

The effects of turbine inlet pressure on the efficiencies of the system are shown in Fig. 2. It can be seen that by growing the inlet pressure of turbine both the overall and ORC efficiencies are falling. When the turbine inlet pressure is increased from 2500 to 5000 (kPa), the overall energetic and exergetic efficiency is decreased from 59 to 64% and the overall exergy efficiency of the multi-generation cycle increased from 69 to 66% and from 52 to 34%, respectively. In addition, the energetic and exergetic efficiency of ORC is decreased from 7 to 4% and from 27 to 24%, respectively. This is because a rise in the turbine inlet pressure produces additional work for the turbine pump.

Fig. 2
figure 2

Effect of turbine inlet pressure on the efficiencies

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4.2 Effect of Turbine Inlet Temperature on ORC Efficiencies

The influence of the turbine inlet temperature on the energetic and exergetic efficiency of ORC is presented in Fig. 3. It can be seen that by increasing the inlet temperature of the ORC turbine, the energy efficiency increases quickly while the exergy efficiency does as well, but at a much slower rate. By increasing the inlet temperature of turbine from 530 to 630 K, the energetic and exergetic efficiency of ORC increases from 4 to 31% and from 15 to 92%, respectively. This is due to increase in the inlet enthalpy of turbine and turbine work.

Fig. 3
figure 3

Effect of inlet temperature of turbine on the ORC efficiencies

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4.3 Effect of the turbine inlet temperature on the turbine work and hydrogen production

Figure 4 shows that an increase in the inlet temperature of the turbine causes a rise in both the turbine work and hydrogen production rate. It can be seen that by increasing the ORC turbine inlet temperature from 530 to 630 (K), the turbine work increases from 87 to 825 kW and also hydrogen production increases from 0.00015 to 0.0016 kg/s because of the increase in the inlet temperature of turbine case an increase in the inlet enthalpy of turbine.

Fig. 4
figure 4

Effect of the turbine inlet temperature on the turbine work and hydrogen production

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4.4 Effect of the Turbine Outlet Temperature on the ORC Efficiencies

Figure 5 shows that an increase in the outlet temperature of the turbine causes a decrease in the both efficiencies. It is obvious that when the outlet temperature is increased from 460 to 520 (K), the ORC energy efficiency decreased from 24 to 4%. Also, by raising the turbine outlet temperature, the ORC exergy efficiency is decreased from 84% to nearly 14%. It is due to a growth in the exergy destruction of the turbine.

Fig. 5
figure 5

Effect of the turbine outlet temperature on the ORC efficiencies

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4.5 Effect of Environment Temperature on the Efficiencies

The effects of ambient temperature on the efficiencies are shown in Fig. 6. It can be seen that there is, in fact, no direct effect on the energy efficiency of the ORC and energetic COP because they do not consider heat losses. On the other hand, the rise in the ambient temperature causes a growth in both the exergetic COP and exergetic efficiency of ORC. This is due to decreased temperature difference between ambient and system.

Fig. 6
figure 6

Effect of ambient temperature on the efficiencies

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4.6 Efficiencies of Subsystems

The Efficiencies of Subsystems are shown in Fig. 7. The energetic efficiency of dryer, energetic efficiency of electrolyzer, exergetic efficiency of ORC, and energetic COP of chiller are determined to be 48.71, 56, 27, and 60%, respectively.

Fig. 7
figure 7

Efficiency of subsystems

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5 Conclusions

The new multi-generation system, analyzed in this report, is capable of supplying energy to residential sectors such as hotels. It is able to provide the production of heating, cooling, hydrogen hot water, dry air, and electricity. The results of the study show that the energetic COP of single-effect absorption system is 60% while the exergetic COP is 10%. Also, the overall energy efficiency is found to be 70%, while the overall exergy efficiency is determined to be about 53%. Moreover, energy efficiency of the ORC is calculated to be 8%, and exergy efficiency of the ORC is determined to be 27%.

The exergy results, in particular, identify the generator as the component with the greatest exergy destruction rate, meaning that it is the main source of irreversibility. However, the system is inline with the renewable energy initiatives being implemented by the global community and is an important system for the future.