Energy recovery from the water cycle: Thermal energy from drinking water

Jan Peter Van Der Hoek,Stefan Mol,Sara Giorgi,Jawairia Imtiaz Ahmad,Gang Liu,Gertjan Medema

doi:10.1016/j.energy.2018.08.097

Abstract

Greenhouse gas (GHG) emissions contribute to climate change. The public water utility of Amsterdam wants to operate climate neutrally in 2020 to reduce its GHG emissions. Energy recovery from the water cycle has a large potential to contribute to this goal: the recovered energy is an alternative for fossil fuel and thus contributes to the reduction of GHG emissions. One of the options concerns thermal energy recovery from drinking water. In Amsterdam, drinking water is produced from surface water, resulting in high drinking water temperatures in summer and low drinking water temperatures in winter. This makes it possible to apply both cold recovery and heat recovery from drinking water. For a specific case, the effects of cold recovery from drinking water were analyzed on three decisive criteria: the effect on the GHG emissions, the financial implications, and the effect on the microbiological drinking water quality. It is shown that cold recovery from drinking water results in a 90% reduction of GHG emissions, and that it has a positive financial business case: Total Cost of Ownership reduced with 17%. The microbial drinking water quality is not affected, but biofilm formation in the drinking water pipes increased after cold recovery.

Highlights

It is generally accepted that emission of greenhouse gases (GHG) contributes to climate change
The objective of this study was to analyze the potential of cold recovery from drinking water originating from surface water on three decisive criteria: 1) the effect on the GHG emissions of Waternet, as it has to contribute to the target of Waternet to operate climate neutrally in 2020; 2) the financial effects, as an important condition is that measures to operate climate neutrally have to be cost neutral and 3) the effect on microbiological drinking water quality, as the technology may not result in a deterioration of the drinking water quality
The results reveal similar microbiological water quality in both systems with a heat exchanger, before and after the heat exchanger, and in the reference system

Summary

Introduction

It is generally accepted that emission of greenhouse gases (GHG) contributes to climate change. Already in 2007 the International Panel on Climate Change (IPCC) recommended to strive for an ambitious reduction of carbon dioxide-equivalent (CO2) emission levels in order to stabilize global warming [1]. In 2013 the IPCC stressed again that continued emissions of GHG will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of GHG emissions [2]. Based on the conclusions of the IPCC, targets and ambitions have been formulated at many levels, ranging from a worldwide level (United Nations) to a city level and public utility level, e.g. water utility Waternet in Amsterdam.

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Conclusion