Rapid growth in air conditioning uptake has led to an increase in carbon emissions. This research proposes a solution for sustainable cooling using Earth Air Tunnels (EAT) powered by biofuels. Learn more about this solution by reading this article.
Abstract
The rapid growth in air conditioning uptake, particularly in hot and densely populated cities like Delhi, India, has led to a significant increase in carbon emissions and energy demand for cooling. To address this issue, this research proposes a solution of sustainable cooling using Earth Air Tunnels (EAT) powered by biofuels. EAT utilizes the natural cooling properties of the earth to provide indoor comfort without heavy reliance on conventional HVAC systems. By integrating renewable biofuels with EAT, carbon emissions can be reduced significantly, promoting environmental sustainability and climate action. This report outlines the implementation strategy for EAT, including its feasibility, benefits, limitations, and the specific energy required to power the system with biofuels. The findings indicate that EAT powered by biofuels offers a promising and energy-efficient approach to sustainable cooling, contributing to achieving the UN Sustainable Development Goals 7 (affordable and clean energy) and 13 (climate action.)
Introduction
The increasing use of air conditioning for cooling households in Delhi, India, has resulted in a surge of carbon emissions and rising energy demand. To combat this issue, we propose the implementation of Earth Air Tunnels (EAT) powered by renewable biofuels. This sustainable cooling solution aims to reduce carbon emissions associated with cooling while ensuring indoor comfort and energy conservation. The maximum drop in air temperature across the earth air tunnel is found to be 8.7°C with an air velocity of 2.69 m/s during peak summer and during winter season the room air temperature is raised by 5-7°C. On the other hand, the system is capable of maintaining room temperature in the range of 27-30°C during peak summer when outdoor temperatures are in the range of 33-41°C1. We hypothesize that EATs can be powered by biofuels, and this study includes an investigation of the energy efficiency of different biofuels.
Energy Consumption Comparison: EAT vs. HVAC
The energy consumption of EAT powered by biofuels is compared to conventional HVAC systems. EAT requires a minimum power of 33 watts2, while HVAC systems typically require 3000-4000 watts3. Hence, EATHE would require a maximum of 1040 MJ of energy, while HVAC would require 110376 MJ. Thus, EATHE powered by biofuels consumes only 0.94% of the energy needed to run HVAC systems annually.
Environmental Impact Analysis
The implementation of EAT powered by biofuels offers several environmental benefits, including reduced greenhouse gas emissions, renewable energy integration, reduced refrigerant use, and improved indoor air quality through natural ventilation. EATHE integration with the building can significantly reduce the electrical power consumption by 96.63 MWh annually, needed for space heating and cooling load. It is discovered from the study that this EATHE has the potential of reducing global warming by substantially mitigating CO2 to the tune of 95 tonnes annually4. However, there are limitations, such as climate suitability, initial costs, and maintenance requirements.
Gasification for Biofuels
Gasification is proposed as a viable method to produce biofuels. The specific energy of four biofuels (coconut bark, bamboo, cashew shells, and mustard) was measured, and it was found that cashew shells had the highest specific energy, making them the most efficient fuel for gasification.
Calculations for EATH Powered by Biofuels
Energy consumption by Fans/ Blowers in EATH Tunnels: Minimum energy required is 33 watts to create a wind speed of 3 m/s and have temperature rise upto 14 degrees5. Power required by EATH is = 33 Watts = 33 j/s
Energy required annually 24/7 by EATH =
33 x 60 x 60 x 24 x 365 = 1040 Megajoules Now the Specific energy of Cashew Shells = 93.49 J/g 1040000000 J / 93.49J/g = 11124184.4 grams = 11124.1844 kilograms Hence around 11 thousand Kilograms of Cashew Shells are required to power the earth air tunnel heat exchanger system 24/7 annually for a household.
Feasibility and Scalability of Gasification
The feasibility of gasification in Delhi depends on feedstock availability and technological readiness. While gasification plants require significant upfront investment, successful waste-to-energy initiatives could utilize municipal solid waste and agricultural residues as feedstocks.
Conclusion
The research concludes that sustainable cooling using EAT powered by biofuels is a promising solution to reduce carbon emissions and energy consumption associated with cooling households. Although initial costs and maintenance considerations need to be addressed, the long-term benefits and potential for wider adoption make EATHE a viable option for achieving energy conservation and sustainable cooling. The integration of gasification to produce biofuels further enhances the environmental benefits of the proposed solution. Embracing these technologies will contribute to mitigating climate change, promoting energy conservation, and building a greener and more sustainable future.
Diagrams and Tables
Data processing - moisture content (Average)
Moisture Content = Initial mass - Final mass (After the moisture has vapourised)
Data Collection - Partial Combustion
Data Processing - Partial Combustion
Bibliography
1. “Thermal Performance Prediction and Energy Conservation Potential of Earth Air Tunnel Heat Exchanger for Thermal Comfort in Building.” Www.teriin.org, www.teriin.org/research-paper/thermal-performance-prediction-and-energy-conservation-potential-earth-air-tunnel.
2. Ahmad, Hijaz, et al. “Experimental Study of the Efficiency of Earth-To-Air Heat Exchangers: Effect of the Presence of External Fans.” Case Studies in Thermal Engineering, vol. 28, 1 Dec. 2021, p. 101461, www.sciencedirect.com/science/article/pii/S2214157X21006249, https://doi.org/10.1016/j.csite.2021.101461.
3. “How Much Electricity Does an Air Conditioner Consume?” Www.tcl.com, www.tcl.com/global/en/blog/how-much-electricity-does-an-air-conditioner-use#:~:text=How%20Muc. Accessed 19 Aug. 2023.
4. Ahmad, Hijaz, et al. “Experimental Study of the Efficiency of Earth-To-Air Heat Exchangers: Effect of the Presence of External Fans.” Case Studies in Thermal Engineering, vol. 28, 1 Dec. 2021, p. 101461, www.sciencedirect.com/science/article/pii/S2214157X21006249, https://doi.org/10.1016/j.csite.2021.101461.