Introduction: Especially when the recent studies are examined, it is seen that the focus is on energy efficiency and time optimization in the heating and cooling stages of the molds. Considering the scenarios where the energy shortage, environmental pollution caused by high carbon emissions, and the climate crises caused by these, will seriously affect the costs in the near future, in the face of increasing demands and production capacities in our world's industry, the optimization of sustainability targets in terms of the both commercial and global climate in these types is considered. Considering the total energy consumed in the production techniques of the products used in many sectors today, it is known that the vast majority of them are produced with thermoset plastic and thermoplastic raw materials. Since the energy spent in the production of these products is generated during the heating and cooling processes of the molds used, the energy efficiency of the processes comes to the fore.

In this study, the costs associated with carbon emissions are also evaluated together with the energy cost, accounting for cost elements that will change in the future. While the use of a solar energy system lowered the expenses associated with emissions, an optimization study that uses a hybrid natural gas and solar energy system was conducted, taking into account the investment cost and the limited panel area.

Modelling: In the manufacture of fiber-reinforced thermoset plastics with the autoclave method, there are many raw material types with the combination of glass, carbon, kevlar, and aramid fiber raw materials and resins such as polyester, vinyl ester, and epoxy, and many methods such as vacuum bagging and mold compression using these raw materials. The curing temperatures of the composite materials used in these methods vary between 100-200 °C depending on the resin systems, and the curing times can vary between 90 minutes and 300 minutes. Especially in the vacuum bagging autoclave method, the curing process is approximately 120 °C and the curing time is approximately 160 minutes. After the prepreg carbons cut according to the lamination plan are laid on the product surface of the mold, the mold is closed and compressed, and the mold is placed in a nylon bag and vacuumed. The mold is opened after 160 minutes and the product inside is taken out. In mass production, the same processes are repeated after the mold is cooled to 60 °C. In this method, energy consumption, source, and efficiency of energy to be used in heating and cooling directly affect carbon emissions.

In this study, the cost optimization of the heat cycle of the composite materials manufactured with the furnace was studied. For the calculations, a double-sided steel mold with an internal volume of 1 m³ furnace, surface area of 1x0.5m, and a thickness of 0.1m was taken as an example. The curing temperature of this mold was determined as 160 minutes at 120°C, and the temperature of placing the product in the mold was determined as 60°C. When the mold temperature is increased to 60°C at the beginning of production, the composite lamination will be placed inside the mold and the mold will be closed. Then the mold will be vacuumed with a nylon bag and heated in the oven. The mold temperature will be increased to 120°C at a certain speed and waited for a total of 160 minutes, and the mold will be taken out of the autoclave and cooled up to 60°C, and the production process will be repeated serially.

Results: In these manufacturing stages, it is aimed to reduce the cost of carbon emissions and reduce energy costs by reducing the use of electricity energy provided by solar panels, energy provided by natural gas and water heating systems, and grid electricity. The average sunshine duration by months for the solar energy electricity generation and natural gas water heating system to be established by accepting the manufacturing factory in Istanbul is given in Table 3.

According to Table 4, when the solar panel system is installed on 16 m², it is seen that the electricity consumption and therefore the emission cost will be completely zero. However, when the investment costs of the solar panel system are calculated annually by accepting the interest rate as 30%, it is seen that the panel system should be installed over 34 m². Considering that more than one furnace and heater systems are used in a facility that manufactures composites, it is not possible to allocate 34 m² of space for the solar panel on the roof of the facility to operate only one oven in this facility, due to the limited area of the roof when it is aimed to operate with the same system in other tools and equipment. For this reason, it should be aimed to minimize the use of solar energy and to provide savings with different systems.

In the costs calculated according to Table 5, since the natural gas investment cost is fixed up to 24 kWh, it is accepted as 15000 TL. Since natural gas can only be used for heating, the power used for cooling from the network has not decreased at all. At the same time, there was no change in the cost of carbon emissions. In the calculation of the annual cost of the investment cost, the annual interest rate was accepted as 30% and the annual interest cost of the investment cost was accepted. According to these calculations, it has been seen that it is possible to reduce the monthly annual costs from 41975.64 TL to 19396.24 TL.

In the costs calculated according to Table 6, the annual interest rate was accepted as 30% in the calculation of the cost of natural gas and solar energy investment on an annual basis, and the investment cost was accepted as the annual interest cost. Natural gas was used only for heating and the solar panel system was used only for cooling. At the same time, only the use of solar panels has reduced the cost of carbon emissions. It has been calculated as a panel area of 4 m², which meets the power of the solar panel cooling system to be used in this hybrid system. It has been accepted that it is possible for this calculated area to install a solar panel system for an oven on the roof of the facility with limited space. The hybrid system has been determined as having an annual cost of 13956.91 TL, which is lower than the use of only the natural gas system.

Conclusions: It has been seen that the hybrid system is an optimum system in terms of cost and sustainability for valid reasons such as being more environmentally friendly than the natural gas system, the facility to benefit from the energy produced by the solar panel system when the furnace is not working, the risk of increase in carbon emission prices in the coming years, the advantage of continuing to work with other systems in case of system failures.