Geothermy to heat and cool metro in Nagpur, India.

The Maharashtra Metro Rail Company Limited (Maha-metro) has decided to use geothermal AC system to reduce operating costs by 10 to 15 %.
In Nagpur, India, Mahametro intends to lower the energy costs for heating and cooling metros thanks to geothermal heat pumps. The system is expected to reduce operating cost by 10 % to 15 %. This central cooling system will transfer heat to the ground or from the ground.

A Mahametro official explained that the heat pump consists of an array of 80-100 meter deep bore wells with a double u-tube, along with manifolds for connection of array of such boreholes. He explained that “The vertical bores provide heat dissipation medium in the ground. Since, water at 80-100 meter depth below ground is at constant temperature, the cooling water temperature from geo-exchange are in a constant zone of temperature between 25 to 30°C".

The official further said, “Whereas cooling water temperature from cooling tower has large variation based on varying ambient wet bulb temperature and are typically 4-5°C higher than the cooling water temperature available from the geothermal /geo exchange system. This provides saving of operating cost of air-conditioning system up to 10-15%. Experts say that with a 1°C rise in temperature, the operating cost can rise up to 8%.”

MahaMetro managing director Brijesh Dixit said the agency has decided to go in for this system due to increasing concerns over cost and availability of electricity and water. “We will install a 175 thermal response (TR) cooling system. The installation of a test borehole and a thermal response test (TRT) was conducted. The rest of the closed loop borehole field is under progress,” he added.

“The ground loop array will be connected to a water cooled chiller that primarily delivers cooling to the building. A significant element in the evolution of this installation is the procurement of the borehole field material from Indian manufacturers and suppliers. Use of this technology will offer a significant reduction in CO2 emissions compared to the existing systems,” Dixit further said.

Source : Times of India