## 3 Thermal Aspects for Improving Energy Performance
### Maintenance of the Greenhouse Environment
#### 3.1.5 Maintenance of Carbon Dioxide \(CO_{2}\) and Light  
Control of \(CO_{2}\) and lighting constitute essential elements in the greenhouse environment, playing crucial roles in facilitating photosynthesis as well as optimal plant growth and development. These factors, along with careful regulation of temperature and humidity, form the basis for a growing environment that promotes plant health and productivity [PERSON] et al. (2019). Effective management of \(CO_{2}\) levels is vital to optimize photosynthesis and stimulate vigorous growth. Strategies to adjust the concentration of \(CO_{2}\) involve the controlled injection of this gas, using advanced technologies that allow precise application, fundamental for the photosynthetic process [PERSON] et al. (2019). Adequate ventilation is also essential, keeping \(CO_{2}\) levels within optimal limits to avoid saturation or deficiency, which could adversely affect photosynthetic efficiency and plant development. When it comes to light, careful management of its quantity, intensity and duration is necessary to meet specific plant growth requirements. As can be seen in (Equation (1)), light plays a critical role in agricultural greenhouses, acting as an essential catalyst in the process of plant growth and development. The quality, intensity and duration of light in the greenhouse directly influence the rate of photosynthesis [PERSON] et al. (2019). Light not only provides the energy necessary for photosynthesis but also regulates other important physiological processes, such as photomorphogenesis, which is the development of plants in response to the quality of light [175]. For example, different wavelengths of light can affect flowering, stem elongation, leaf development and other aspects of plant development. In agricultural greenhouses, where environmental control is paramount, artificial lighting becomes an indispensable resource, often used to complement natural light. This type of lighting is essential to optimize plant growth and extend growing cycles, regardless of external light [175]. This is particularly important in regions with low sunlight or during periods with less natural light. The implementation of adequate lighting systems is essential to increase the photosynthetic efficiency of plants and, consequently, the productivity of the greenhouse [75; 92]. Using techniques such as shading systems, supplemental lighting, curtain control and strategic crop positioning helps maximize light absorption, crucial for photosynthesis, without excessively increasing the greenhouse's internal temperature [176]. The interaction between light and \(CO_{2}\) highlights the complexity of managing these elements in greenhouses, indicating the need for a carefully controlled environment to support vital physiological processes and ensure healthy plant development. Therefore, the implementation of advanced technologies to control \(CO_{2}\) and light is a critical aspect of modern agronomy, allowing the creation of ideal growing conditions that promote efficiency and sustainability in agricultural production in controlled environments [177]. Maintaining optimized \(CO_{2}\) concentration is vital to maximizing plant photosynthetic efficiency, resulting in accelerated growth and greater agricultural productivity. \(CO_{2}\) maintenance systems are employed to adjust \(CO_{2}\) concentrations within greenhouses, using methods ranging from conventional solutions to technological innovations [178; 179; 180]. The most conventional method of \(CO_{2}\) enrichment involves the use of propane or natural gas burners [178; 181; 182]. These devices burn fossil fuels to generate \(CO_{2}\), releasing it directly into the greenhouse environment. Although effective in increasing the concentration of \(CO_{2}\), this method requires careful ventilation to prevent the accumulation of harmful by-products of combustion [183]. A more controlled approach involves direct injection of compressed \(CO_{2}\) from cylinders or storage tanks.