POWER GENERATION FROM COOLING TOWER

Introduction

World energy demand has shown a remarkable increase over the past century due to population growth and economic development.  However the over consumption of fossil fuel brings harmful impact on the world’s climate due to greenhouse gas (GHG) emission.  Two thirds of the anthropogenic GHGs emission is accounted by the Power Generation by the Thermal Power Plants.

In order to reduce the dependence on fossil fuels for energy generation, renewable energy (RE) plays a critical role in reducing the GHGs emission.

Wind energy is the second biggest source of RE after Solar Energy.  It is the fastest growing RE source in the world.  The share of wind energy is 14% at the global scale.

Project Overview

An assembly of two vertical axis wind turbines (VAWTs) and an enclosed casing  is installed above a cooling tower to harness the kinetic energy of the discharged wind from exhaust fan for electricity generation.  The enclosure consists of guide vanes and diffuser plates are used to enhance the rotational speed of the turbines for power generation.  The angle of the guide vanes is optimized to ensure the up-coming wind steam impinges the rotor blades of the turbine at an optimum angle.  The diffuser plates are tilted at an optimum angle to increase the discharged flow rate.  The performance of the system is tested in the laboratories scale.

Working Principle

It is comprised of 2 vertical axis wind turbines (VAWTs) mounted in cross-wind orientation on the top of an induced Draft counter flow cooling tower’s outlet to tap the kinetic energy in the discharged air for electricity generation.  The normal discharge velocity from an induced draft cooling tower is about 9m/sec.

Each cooling tower possesses a designed mass ratio of water flowing through the tower to the air flow, according to the cooling tower heat load and size,  for best cooling tower efficiency.

Since there is a defined amount of discharged air flow from the cooling tower, VAWTs are mounted on top of the cooling tower to utilize the discharge air kinetic energy which is higher and more consistent as compare to the natural wind.

In addition the diffuser plates are tilted outwardly at an optimum angle relative to their vertical axis causing a flow augmentation effect which greatly helps to increase the discharged air flow.

Based on Bernoulli’s principle a venturieffect is created,  allowing wind velocity augmentation to be achieved,  as a result from a drop in pressure within the diffusers.

This feature is beneficial to VAWTs in terms of their performance as they are capable of self-starting sooner and rotating closer to its rated speed.

Both the VAWTs are capable of spinning at a higher rpm above the cooling tower, and a suction effect is created due to low pressure region around the rotor.  As a consequence, the volumetric flow rate of air increases for integration with the VAWTs, resulting in a higher energy output.

This way we can tap a huge amount of energy, which otherwise is wasted.