Investigating Indoor Ventilation in Multi-habited houses: A case of Ogbomoso, Nigeria (Published)
The study investigated the indoor natural ventilation condition in multi-habited houses in the traditional core of Ogbomoso. Factors affecting natural ventilation in buildings such as orientation, external spacing, landscape and opening conditions were assessed through physical observations and direct measurements. Data on indoor air movement (velocity) was obtained with the use of kestrel 4500 pocket weather and environmental metre after due calibration with the climatic data of Ogbomoso which had earlier been obtained from the Nigeria meteorological station; the data was obtained in order to assess the level of ventilation and air movement in their various spaces. A living room, a bedroom and a kitchen (which are spaces where residents spend most time) were randomly selected in each multi-habited building for the purpose of the study. Obtained results were compared with the standard values given by scholars Borda-Dias and Chand. The study found all factors affecting natural ventilation to be grossly inadequate when compared with standards just as low air velocity level was also recorded in all their spaces (0.08 minimum and 0.48m/s maximum observed as against minimum of 0.50m/s recommended by Borda-Dias). The study concluded that there is a likelihood of high dependency on active driven mechanical devices in the study area if suitable indoor thermal comfort is to be achieved. The study recommended that a more awareness level on natural ventilation systems should be created and a rehabilitation of multi-habited homes in the study area is suggested.
Citation: Abdulrasaq Kunle Ayinla and Ilelabayo Ismail Adebisi (2021) Investigating Indoor Ventilation in Multi-habited houses: A case of Ogbomoso, Nigeria, International Journal of Civil Engineering, Construction and Estate Management, Vol.9, No.3, pp.1-15
Keywords: Energy, Natural Ventilation, Thermal Comfort, multi-habitation, natural cooling
Modelling Energy Recovery from Wastewater Treatment by Anaerobic Digestion (Published)
In this study, attempt was made to model gas production process from an anaerobic digestion of sewage sludge in a treatment plant. Apart from the issue of environmental cleanup this process of sewage treatment offers, it has become a viable tool to solving energy problems that exist in many parts of the world. Nigeria has much wastewater and this constitutes environmental pollution when channelled to the freshwaters body. Some wastewater; domestic and industrial, has to be treated before channelling them into waterways and in doing this, biogas can be tapped from the system if anaerobic digesters are designed and incorporated into the treatment plants. In this study, this process of biogas production was modelled to ascertain the amount of energy that can be recovered from wastewater treatment plant, for economic usage in the operation of the treatment plant and municipal consumption. To achieve this objective, equation was derived and its application yielded a positive result. Results from two different experimental reactors, reactors 1 and 2 (see Table 4.2 above) were used in comparison with the model reactors to investigate performance of the model. Figure 4.1 shows the gas yield for the different reactors investigated. Statistical analysis of the overall results shows that model reactor 1 has a coefficient of correlation (CORR) of 0.95, this demonstrate a good fit with the experimental results obtained from reactor 1. However, a mean absolute percentage error (MAPE) and root mean square error (RMSE) of 2.15 and 7.49 respectively, was recorded during this process. These values indicate a significantly low error of estimates and shows that the model is reliable.Similarly, model reactor 2 gave a CORR of 0.96 with errors of estimate (MAPE) of 1.34 and RMSE OF 3.12. Meanwhile, it can be observed that both experimental reactor 1 and 2 have a slightly higher values of gas yield than their corresponding model reactors. This trend is rather good in relation to safety in gas production estimate using the model. An overestimating model would be misleading and give a false data when such is needed for energy generation design and operation. . The biogas yield obtained were used to power a micro gas turbine in order to determine electrical energy output from the system, a process that have now been commercialized for economic benefits. Equation 3.24 was derived and its consequent solution, equation 3.27 was used for that purpose. Figure 4.6 shows the energy output for experimental reactor 1. The result obtained shows a close fit between the turbine output and the model output. Precisely, a CORR value of 0.96 was obtained with a small error of estimate of 2.34 and 8.00 respectively for MAPE and RMSE. Similarly, figure 4.7 shows energy output for experimental reactor 2. In this, the coefficient of correlation was found to be 0.94 with MAPE and RMSE being 2.15 and 3.55 respectively. Figure 4.8 and 4.9 shows the energy output for model reactors 1 and 2 respectively. The CORR, MAPE and RMSE were 0.95, 3.78 and 5.51 respectively for model reactor 1 while a similar value of 0.97, 1.73 and 5.02 were recorded for model reactor 2 respectively. In all, a very good correlation values was obtained to show that energy generation from treatment plant can be modelled given the biogas yield data. It should be noted that turbine plant operational mechanism may vary slightly depending on their capacities; consequently, an updated recalibration of the model would be necessary.
Keywords: Anaerobic reactor, Digestion, Energy, Sewage, Treatment.