Providing adequate ventilation for high occupancy buildings is necessary to maintain proper air quality in the conditioned space. However, ventilation increases energy consumption, especially when the outside conditions are hot and humid. Also reheating may be necessary if ventilation leads to increased latent load fraction. The implementation of a suitable energy recovery system can reduce the energy consumption due to ventilation. A dedicated outdoor air unit (DOAU) system comprises an enthalpy wheel, a cooling coil, and a passive desiccant wheel, can be used both for energy recovery as well as reducing reheating requirements. The enthalpy wheel reduces the coil load by pre-cooling the outdoor air, while the passive desiccant wheel eliminates the need for a reheat coil. However, the addition of the DOAU system increases the initial capital investment of the cooling system substantially. Therefore, its use has to be justified through proper performance evaluation. The current study analyses the performance characteristics of a centrally conditioned educational building using a DOAU. To quantify the savings in annual cooling load and energy consumption with DOAU, a detailed analysis of the building is carried out using the well-known Transient System Simulation Tool, TRNSYS. Building simulations are carried out from February to November for hot-humid and hot-dry climates, represented by Kolkata, West Bengal and Jodhpur, Rajasthan, respectively, to assess the suitability of the DOAU system across diverse climatic zones in India. The results show that the required building total load and latent load are maximum in the months of May and July for both Kolkata and Jodhpur. However, Kolkata has a higher building latent load than Jodhpur. Results also indicate 18.0% and 17.5% reductions in annual chiller load and energy consumption for Kolkata, and 6.2% and 5.9% for Jodhpur, with the DOAU system. Implementation of the DOAU system yields better performance during the monsoon compared to the summer months. The overall performance of the DOAU system is better for a hot-humid climate. Therefore, the study is further extended to analyse the performance of the DOAU system under hot-humid conditions. As the performance of the enthalpy wheel deteriorates in terms of sensible and latent effectiveness, the required cooling coil capacity increases. Degradation of latent effectiveness of enthalpy wheel has stronger effect on cooling capacity. The economic analysis is carried out for hot–humid and hot–dry climates. The simple payback period with implementation of the DOAU system, considering constant effectiveness of enthalpy wheel and electric tariff is found to be 4.9 years for Kolkata. The economic analysis shows that the DOAU system is suitable for other climates, such as Jodhpur, only with a higher electricity tariff.
Ramgopal et al. (Mon,) studied this question.