## 3 Comparative Study of Systems
### Dehumidifier with Desiccant Wheel  
Dehumidifiers with adsorption systems, or desiccant systems, are coated with materials of high absorption (hygroscopic) that remove moisture from the air as needed, as shown in Figure 5.  
The advantages of desiccant wheels are [22]:  
* Long lifespan;
* Digital and accurate control according to application needs;
* Automatic adjustment of relative humidity according to indoor environmental situations;
* Performance is not reduced in environments with a temperature range from 0 \({}^{\circ}\)C to 45 \({}^{\circ}\)C;
* High performance in critical situations when precision is required;
* No accumulation of liquid (water) in the compartment;The dehumidifier must be able to operate even without energizing the reactivation heater for long periods, and without damaging the desiccant cylinders. In this study, the dehumidifier model FFB 300 Ecodry [22] is used and consists of three high-efficiency desiccant cylinders with a dehumidification capacity of 80 kg/day and electrical power of 3.8 kW each, thus totaling 11.4 kW of electricity consumed. Figure 6 shows an inside view of a desiccant wheel [22]. In the first instance, refrigeration dehumidification seems more advantageous because, for the same capacity (240 kg/day), it has an energy demand of 7.8 kW. Regarding environmental sustainability, the TEWI (Total Equivalent Warming Impact) considers indirect and direct emissions produced through energy consumption in the equipment's operation. The TEWI index measures, in kg, the chemical compound carbon dioxide (CO\({}_{2}\)) equivalents. The TEWI is calculated as the sum of the two parts:  
1. Direct emission--This includes part of the refrigerant fluids available during the equipment's useful life, including until the end of its life, all unrecovered losses. Figure 4: Air flow equipment 4 Pool (Adapted from [18]). Figure 5: Schematic of a desiccant wheel (adapted from [22]). 2. Indirect emission--There is a huge impact on CO\({}_{2}\) emissions from the use of fossil fuels, which generates the electricity used to operate equipment over its lifetime. The TEWI calculation is given by Equations (3) and (4) [28]):  
\[\mathrm{TEWI}=\mathrm{GWP}(\mathrm{direct,~{}refrigerant~{}leaks~{} includig~{}EOLC})+\mathrm{GWP}(\mathrm{indirect,~{}operation}) \tag{3}\]  
\[\mathrm{TEWI}=(\mathrm{GWP}\cdot L_{annual}\cdot n)+\mathrm{GWP}\cdot m\cdot \left(1-\alpha_{recovery}\right)+\left(E_{annual}\cdot\beta\cdot n\right) \tag{4}\]  
where:  
TEWI = Total Equivalent Warming Impact. GWP = Global Warning Potential of refrigerant, relative to CO\({}_{2}\) (GWP CO\({}_{2}\) = 1). EOLC = End-of-life cycle. \(L_{annual}\) = Leakage rate (leakage) p.a. (kg). \(n\) = System operating life (years). \(m\) = Refrigerant charge (kg). \(\alpha_{recovery}\) = Recovery/recycling factor, from 0 to 1. \(E_{annual}\) = Energy consumption per year (kWh pa. a.). \(\beta\) = Indirect emission factor (kgCO\({}_{2}\)/kWh) [29]. The GWP (Global Warming Potential) is essential information for calculating the TEWI, but it is a more complete indicator, as it addresses the demand for gas leaks and indirect emissions from energy matrices. The cost of the dehumidification system is very important, but the most integral indicator for deciding is the environmental operation, which has a life cycle cost. The result of the TEWI is the formula that gives total CO\({}_{2}\) emissions and life cycle energy. The effect and impact of these variables show that refrigerants have a greater consequence in Brazil than in other important world markets. Emissions by sources (indirect emission factor, \(\beta\), given in kg CO\({}_{2}\)/kWh, varies according to the energy available to be transformed (energy matrix). For example, in Brazil, the electricity system matrix is divided into the same transmission throughout the country, from north to south; therefore, with the National Energy Balance of Brazil (BEN) [30], Brazil emits 0.088 kg (CO\({}_{2}\))/kWh.