Fresnel Solar Cooling System
MTN Headquarters Datacentre – 484 m2 Concentrating Linear Fresnel Solar Cooling System – REACH Renewable
Short Description of the Solar Cooling System
REACH Renewable designed and installed the first Concentrating Linear Fresnel Solar Cooling system in the commercial telecommunication industry. The system generates 242 kW(thermal heat) peak and provides 330 kW(thermal cooling) peak.
Principle and Solar Cooling System Characteristics
An absorption chiller uses heat instead of electricity as the driving energy source to produce cooling (chilled water). The extraction of heat happens through a repeated process of evaporation under vacuum, whereby water is separated from a lithium bromide solution and the water becomes the refrigerant in the system. This means that the ozone depletion potential (ODP) as well as the global warming potential (GWP) of the refrigerant are “zero”. The heat in this system is generated from the sun.
22 modules with a peak heat generation capacity of 11kW each are installed in a series of two 11-module strings to produce 242 kW(thermal heat) peak. Each module consists of 11 mirror rows, who uniaxially track the sun to focus the sunlight onto a central vacuum absorber tube. The tracking is based on a close-control system, which follows a program based on GPS coordinates, date & time and orientation of the solar array. A secondary receiver on top of the absorber tube collects and refocuses the sun rays that missed the absorber tube in the first attempt.
In the absorber tube the water is heated to 180 degrees Celsius, which is the required heat input temperature to a double-effect absorption chiller and after transferring the heat to the absorption chiller, the water returns to the solar array at 165 degrees Celsius. The operating pressure of the solar loop is 12 barg.
The system is controlled on supply temperature and can be precisely regulated by either adjusting the flow rate through the system or by defocussing the mirrors.
In the event of any safety chain breaches (eg: high wind loads, high&low pressure, low/no flow, no power) the mirrors move into the protective stow position. A UPS unit is installed to drive the mirrors, if power to the system is cut.
In case of rain the mirrors automatically move into a self-cleaning position.
On the cold side of the absorption chiller the chilled water is circulated to the datacentre space for equipment cooling. The capacity of the solar system is around 50% of the total datacentre cooling requirement once fully occupied.
The medium temperature heat is rejected via a cooling tower.
The Linear Fresnel technology provides a solution to the South African Industrial sector for process heating and cooling or direct steam generation.
CLIENT INFORMATION AND AGREEMENT TO FILM THE SYSTEM
Frank has indicated it will be challenging but possible. (after 9th of July 2014)
- Wally Weber
- Cell: 082-871 4049
MTN Unveils Another Africa First Cooling System
What is Concentrating Solar Power (CSP)?
CSP uses heat generated from the sun to generate electricity, and in the case of MTN, it is used for cooling the data centre.
How are mirrors utilised and how does the system work?
The system consists of 242 solar mirrors covering a total area of 484 square metres. The mirrors track the sun to generate pressurised hot water at 180 degrees Celsius. The hot water powers an absorption chiller that produces chilled water which is circulated into MTN’s data centre for cooling of IT equipment. The cooling capacity of 330 kW.
How do the mirrors maximise the sun’s power?
The mirrors follow the movement of the sun based on the GPS location, orientation, and the date and time. This information guides the system to track the sun to concentrate on the central absorber tube where heat is generated.
What happens in the absorption chillers?
The absorption chillers use a lithium bromide water solution, with water as the refrigerant. A small pump is used as an electrical consumer in the chiller, hence the electrical COP (coefficient of performance) of the chiller itself is greater than 100.
What is the environmental impact of the plant?
This is a completely green solution that has zero global warming potential (GWP=0) and no ozone depletion potential (ODP=0).
CSP Press Pack