Large cooling systems consume up to 25% of the total electricity used on deep level mines. These
systems are integrated with the water reticulation system to provide chilled service water and cool
ventilation air. Improving the energy efficiency of these large cooling systems is an important
electrical demand-side management initiative. However, it is critical that the service delivery and
system performance be maintained so as to not adversely affect productivity.
A novel demand-side management strategy, based on variable water flow, was developed to improve
the energy efficiency of large cooling systems like those found on deep mines. The strategy focuses
on matching the cooling system supply to the demand through the use of modern energy efficient
equipment, such as variable speed drives. The strategy involves the modulation of evaporator,
condenser, bulk air cooler and pre-cooling water according to partial load conditions.
A unique central energy management system was developed to integrate the proposed strategies on
large cooling systems. The system features a generic platform and hierarchical network architecture.
Real-time energy management is achieved through monitoring, optimally controlling and reporting
on the developed strategy. The system is robust and versatile and can be applied to various large
cooling systems.
The feasibility of the strategy and energy management system was first investigated through the use
of an adapted and verified simulation model and a techno-economic analysis. The strategy was then
implemented on four large mine cooling systems and its in situ performance was assessed as
experimental validation. The results of the Kusasalethu surface cooling system are discussed in detail
as a primary case study while the results of the Kopanang, South Deep South Shaft and South Deep
Twin Shaft cooling systems are summarised as secondary case studies. The potential to extend the
variable water flow strategy to other industrial cooling systems is assessed through an investigation
on the cooling system of the Saldanha Steel plant. Results indicate that, over a period of three months, average electrical load savings of 606-2 609 kW
(29.3-35.4%) are realised on the four systems with payback periods of 5-17 months. The average
electrical load saving between the sites is 33.3% at an average payback period of 10 months. The
service delivery and performance of the cooling system and its critical subsystems are not adversely
affected. The potential to extend the method to other large cooling systems is also shown. The
developed variable water flow strategy is shown to improve the energy efficiency of large cooling
systems, making a valuable contribution towards a more sustainable future.
This thesis is presented as a detailed discussion of the entire research process. The key results have
also been summarised in a series of five research articles attached as independent annexures. Three
articles have been published in international scientific journals, one has been presented at and
published in the proceedings of an international conference and one is still under review. / Thesis (PhD (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/9509 |
| Date | January 2013 |
| Creators | Du Plessis, Gideon Edgar |
| Publisher | North-West University |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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