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WATER SYSTEMS Renske Kind & Henk Lodder – Deerns


Safe and simple hot water supply system


In current hospital design practices the hot water supply system is usually based on a centralised concept. To control the risk of Legionellacolonisation, high temperatures and continuous circulation is required, leading to issues concerning safety and control, as well as substantial energy losses. The Deerns Save & Simple (DSS) hot water offers an alternative, based on decentralised, individual hot water generation using electric instantaneous water heaters.


Calculations have shown that the DSS concept can be beneficial in terms of energy consumption and, depending on local price levels, life cycle costs. Considered from a wider perspective, the DSS hot water concept could accelerate the development of the all- electric hospital. It is widely believed that future energy infrastructures will be based on electricity as the main energy carrier, induced by the increasing exploitation of renewable energy resources. Issues surrounding safety, comfort and


sustainability are getting more attention in hospital design practices today. In this context, the usual centralised hot water supply system is becoming increasingly outdated. The system is a potential hotbed of


Legionella bacteria which constitutes a major health risk that requires extensive control measures. In addition, the system leads to substantial energy losses. These problems can be largely eliminated by applying a system based on decentralised, individual hot water generation using electric instantaneous water


‘At a temperature of 50°C, multiplication of Legionella bacteria is inhibited, but bacteria that are already present can survive for several hours.’


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Figure 1: Typical profile of the electric power demand of a hospital in The Netherlands, during a warm summer day and a winter day. The grey areas represent the expected peak periods in the use of hot water, mainly caused by showering.


heaters. Application of the DSS hot water concept, results in a safe and simple hot water supply system, to meet local hot water demands. To assess the feasibility of the concept, the


energy performance of the DSS hot water concept was modelled and compared to the performance of a conventional, centralised system containing a gas-fired water heater.


Centralised system In a centralised system hot water is generated at a central location and distributed via an extensive piping system. Depending on the level of usage, part of the water is pumped


Renske Kind


Renske Kind studied at Delft University of Technology where she obtained a double degree in Architecture and Applied Sciences, majoring in Sustainable Energy Technology. After completing her academic degree, she started working at Deerns. She has worked on various hospital engineering projects and within this complex field she focuses on integrated design, with the ultimate goal to reach more sustainable energy supply systems and sustainable buildings in general.


back to the water heater. The function of this circulating system is


twofold: • The hot water delay is reduced and • The water temperature can be maintained.


The minimum temperature is dictated by Legionella control requirements. At a temperature of 50˚C, multiplication of Legionella bacteria is inhibited, but bacteria that are already present can survive for several hours. In order to quickly inactivate Legionella bacteria, the temperature should be over 60˚C.1 In our model, we assumed that Legionella is removed from the water at the point of entry


Henk Lodder


Henk Lodder is an expert in plumbing engineering at Deerns. He has 30 years of experience in hospital engineering and is recognised as an authority in this specialised field. He is a visionary who looks critically at technical aspects and issues such as operating costs, reliability and durability.


IFHE DIGEST 2015


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