## 4 Energy and Environmental Evaluation of the System Retrofitting Variants
### Annual Emissions of Carbon Dioxide  
Another important parameter in the evaluation of sustainable energy management is the level of carbon dioxide emissions. The annual carbon dioxide emissions for the basic variant of chilled water production in the pharmaceutical plant could be calculated as follows:  
\[E_{\text{CO2}}=e_{\text{CO2}}^{\text{WK}}\cdot E_{P,0} \tag{6}\]  
where:  
\begin{tabular}{c c c c} \hline \hline \(E_{\text{CO2}}\) & - & annual CO2 emissions connected with producing cooling energy for the basic variant, in MgCO2/a, & \\ \(E_{P}\) & - & annual consumption of primary energy for the purpose of producing cooling energy, in MWh/a, & \\ \(e_{\text{CO2}}^{\text{WK}}\) & - & carbon dioxide emission ratio for a given primary fuel in the basic variant (coal) \(e_{\text{CO2}}^{\text{WK}}=0.35\) MgCO2/MWh. & \\ \hline \hline \end{tabular}  
In Variants 1 and 2, the annual carbon dioxide emissions were derived from Equation (7), again applying the principle of avoided cost:  
\[E_{\text{CO2}}=\frac{1}{\eta_{\text{TOT,1}(2)}}\cdot\frac{Q_{\text{ch,r}}}{ \text{SEER}_{\text{1}(2)}}\cdot(1+e)\cdot\epsilon_{\text{CO2}}^{\text{GZ}}- \frac{1}{\eta_{\text{TOT,0}}}\cdot\frac{Q_{\text{ch,r}}}{\text{SEER}_{\text{1}( 2)}}\cdot e\cdot\epsilon_{\text{CO2}}^{\text{WK}} \tag{7}\]  
where:  
\begin{tabular}{c c c} \hline \hline \(E_{P}\) & - & annual consumption of primary energy for the purpose of producing cooling energy, in MWh/a, & \\ \(e_{\text{CO2}}^{\text{GZ}}\) & - & carbon dioxide emission ratio from primary fuel used in variants based on absorption water chillers (natural gas) \(e_{\text{CO2}}^{\text{GZ}}=0.20\) MgCO2/MWh. & \\ \hline \hline \end{tabular}  
The annual carbon dioxide emissions stemming from cooling energy generation in the pharmaceutical plant were calculated according to Equation (7) and are compared in Table 5. Annual carbon dioxide emissions associated with chilled water production.  
\begin{tabular}{c c c c} \hline \hline \multicolumn{1}{c}{**Parameter**} & **Variant 0** & **Variant 1** & **Variant 2** \\ \hline Annual consumption of primary energy & 3000 & 662.3 & 0 \\ \(\text{forcompression water chillers, in MWh/a}\) & & & & \\ \hline Annual consumption of primary energy & 0 & 2158.6 & 2648.7 \\ \(\text{for absorption water chillers, in MWh/a}\) & & & & \\ \hline \hline \(E_{\text{CO2}}\)—total annual CO2 emission for & 1050.0 & 156.0 & \(-\)93.0 \\ chilled water production, in Mg/a & & & & \\ \hline \hline \end{tabular}  
According to Table 5, the application of absorption water chillers as the core source of cooling energy production in the pharmaceutical plant would allow for a significant reduction of carbon dioxide emissions to the atmosphere. Compared to system modernization based on compression water chillers (Variant 0), annual CO2 emission related to chilled water production could be reduced by over 900 Mg/a (in the case of Variant 1) and 1140 Mg/a (in the case of Variant 2). The negative CO2 emissions in Variant 2 were due to both the application of the avoided cost principle, which greatly reduced primary energy  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{1}{c}{**Parameter**} & **Variant 0** & **Variant 1** & **Variant 2** \\ \hline Annual consumption of primary energy & 3000 & 662.3 & 0 \\ \(\text{forcompression water chillers, in MWh/a}\) & & & \\ \hline Annual consumption of primary energy & 0 & 2158.6 & 2648.7 \\ for absorption water chillers, in MWh/a & & & \\ \hline \hline \(E_{\text{CO2}}\)—total annual CO2 emission for & 1050.0 & 156.0 & \(-\)93.0 \\ chilled water production, in Mg/a & & & \\ \hline \hline \end{tabular}
\end{table}
Table 5: Annual carbon dioxide emissions associated with chilled water production.  
consumption, and replacing coal with natural gas, which has a much lower index of carbon dioxide emissions per unit.  
The analysis of primary energy consumption and carbon dioxide emissions led us to the recommend the implementation of Variant 2, i.e., the installation of a 1.6 MW dual-stage absorption water chiller.