PhD Defence: Efficient Management of Compact Storage Systems

Newly designed compact storage systems can substantially reduce storage space, land and energy consumption as well as CO2 emissions while shorter response times to the customers can also be achieved, according to PhD research by Nima Zaerpour at Erasmus University Rotterdam.

In his dissertation, entitled <link doctoral-programme phd-in-management phd-projects detail>Efficient Management of Compact Storage Systems, Zaerpour provides new models and methods for storage facility managers which are aimed at better use of the increasingly scarce availability of storage space and land. He focuses on new types of 3D compact storage systems, in particular live-cube storage systems, where each unit load rests on a shuttle which can move in horizontal and depth directions - saving much footprint, but still allowing products to be easily accessed individually.

The key performance measure for compact storage systems is response time, which is also the focus of this dissertation. Zaerpour analyses these systems at two decision-making levels. At the tactical (design) decision level, he focuses on the system-dimensioning problem aiming at short response times. At the operational decision level, he studies storage assignment and retrieval sequencing problems to shorten the response time of compact storage facilities (e.g. unit load throughout time or makespan).

Zaerpour finds that optimising design and operational decisions can significantly reduce the response time to customers. In addition, optimal configuration of these automated storage facilities is independent of the followed storage assignment policy. Practitioners benefit from this, as it greatly simplifies finding optimal configuration.

Nima Zaerpour defended his dissertation on 22 February 2013. His supervisor was <link people rene-de-koster>Professor René de Koster. His co-supervisor was Yugang Yu. Other members of the Doctoral Committee were Professor John Bartholdi (Georgia Tech), <link people leo-kroon>Professor Leo Kroon (Erasmus University Rotterdam) and Professor Kees Jan Roodbergen (University of Groningen).

About Nima Zaerpour

Nima Zaerpour (Iran, 1983) received his BSc in Industrial Engineering from Sharif University of Technology in 2005 and his MSc in Industrial Engineering from University of Tehran in 2008 both in Tehran, Iran. He joined RSM in September 2008. His research interests are next generation storage systems, e-commerce order fulfilment systems, sustainable warehouse operations, facility logistics, distribution logistics, etc.

He was a visiting scholar at the H. Milton Stewart School of Industrial and Systems Engineering at Georgia Tech in 2012, where he attended the Global Supply Chain Scholars Program. Moreover, in 2011, he was a visiting scholar in the Department of Information Management and Decision Science at the University of Science and Technology of China. His research findings have been presented in many international conferences including INFORMS Annual Meetings (2009, 2010, 2011, 2012), POMS (2012) and EURO (2009, 2010). He is currently a postdoctoral fellow at RSM where he will continue working on compact storage systems with close collaboration with logistics companies.

Abstract of Efficient Management of Compact Storage Systems


Warehouses are important nodes in supply chains. They decouple supply from demand in time, assortment, quantity, and space. By doing so, economies of scale can be achieved in transport, as warehouses allow to regroup transport flows leading to lower cost. They also allow postponement of value addition, increasing service levels at lower inventory levels. Warehouses are particularly needed in densely populated areas, close to where demand is generated and labour is available. Warehouses require much space to realise economies of scale. Warehouse buildings are often quite large, more than 10,000 m2 built space is common, and much infrastructure outside the building is needed. Unfortunately, in many of the urbanised areas, space for such large facilities has become short. In order to address this issue, enterprises are moving toward next generation storage systems, namely “three-dimensional (3D) compact storage systems”. These systems are designed with the objective to save floor space and labour costs, and increase the reliability of the order picking process. Several types of 3D compact storage systems exist with different handling systems, such as S/R machines, conveyors, shuttles and elevators. They take care of horizontal, vertical and depth movements. Zaerpour’s dissertation focuses on new types of 3D compact storage systems, in particular live-cube storage systems, where each unit load rests on a shuttle that can move in horizontal and depth directions, in co-operation with shuttles of other unit loads. In such a system, at least one empty storage slot per level is required.

One of the key performance measures for compact storage systems, which is also the focus of this dissertation, is response time. Zaerpour analyses these systems at two decision-making levels. At the tactical (design) decision level, we focus on the rack-dimensioning problem aiming at short response times. At the operational decision level, he investigates storage assignment and retrieval sequencing problems to shorten the response time.