Tuesday, December 21, 2010

Using Small Wind Turbines in Underground Mines

In underground mines, it has been recognized that there is a requirement for an independent battery charging system other than the AC power source that can be used in case of emergency since the radios located through the underground mines can’t stay charged for sufficient periods to insure the safety of trapped mineworkers.

Since it was a necessity to always have air distributed throughout the mine in order to supply oxygen and remove unwanted gases, it was suggested to use this air (wasted energy) to charge the batteries using small wind turbines that can be installed in the path of moving air that is forced into the underground mine.

It was necessary to determine the feasibility of the idea of using small wind turbines that are placed in the airflow path to charge batteries especially since the airflow will not be much variant. It was found that it was feasible and a numerical model was developed utilizing Blade Element Momentum theory to produce optimal battery charging system to aid in case of emergency mine communications.

The power requirements to charge the batteries were 4 Watts and several rotor configurations have been found to produce the amount of power required. However, due to safety issues and structural concerns in an underground mine, the required wind turbine should be designed and shielded to protect mine workers. It was possible to provide the structural protection with the use of a diffuser shroud which also helped in increasing the power output of the wind turbine system.

Results from the model and the physical parameters needed to efficiently design a wind turbine system for underground mines was addressed by this thesis and has been published in this book: Feasibility and optimum design study of a low speed wind turbine rotor system for underground communication power.

Solar Air-Conditioning: Solar Case Study

This solar air conditioning case study pertains to the sizing of an indoor solar conditioning system that uses an absorption chiller unit operating with water and lithium bromide (Li Br) for a hypothetical 3 bedroom Villa or house.

Hypothetical Villa Solar Air-Conditioning Case Study

Input Data for Sizing:

Climate data for the calculation of solar radiation related to a selected hot climate city. The data relates to a hypothetical two-family dwelling (or large apartment) and to the building’s energy performance as assumed below.

Indoor conditioned volume    562,5 [m3]
Net surface area    187,5 [m2]
Maximum heat loss    100 [kWh/day]

Month Average daily
air temperature
Average daily
cooling demand
January 20.7 54
February 20.6 53
March 22.3 59
April 25.8 71
May 30.1 86
June 32.2 93
July 33.6 98
August 34.2 100
September 32.9 96
October 30.2 86
November 26.8 75
December 23.2 62

Design Stage for Solar Air-Conditioning Case Study:

The sizing calculations of the absorption chiller and the solar field was determined taking into account a daily design energy demand due to heat loss of approximately 100 kWh.

Electronic Wind Speed Meter

There are a lot of electronic wind speed meters on the market, however; the Davis Turbo Electronic Wind Speed Meter measures wind speed and provides maximum sensitivity and accuracy for your convenience which is vital for your wind turbine site. The unit measures wind speed from 0 - 99.9 mph . The turbine rotation is sensed by an infrared light beam which adds no friction to your reading and gives you the accuracy you desire.

Advanced Control System for Wind Turbine

Variable speed drives in modern wind turbines are used to maximize wind turbine efficiency when the turbine is running below rated power and to reduce loading on the drive-train.

In addition, there is something called a pitch control of the blades which is usually used to limit the energy captured when the turbine is operation above rated wind speed.

The benefits of a more complex variable-speed drive, variable-pitch control of wind turbines is offset by control flexibility. That is, higher efficiency, better power quality, in addition to a longer useful life of the wind turbine.