A Scenario for Sustainable Energy and Water Systems Integration in Urban Areas

by Renata Mikalauskiene

Figure 1: Water-energy nexus: Water is used
to produce energy, and energy is used
to treat water.
Reliability and quality of energy and water is a global concern that impacts the daily life of the 21st century civilization.

Water and energy are intricately linked and should be managed as interrelated resources. The concept of the energy and water nexus refers to the relationship between the water used for energy production including both electricity and sources of fuel and the energy consumed to extract, purify, deliver, treat and dispose of water or/and wastewater.

Rising demand for energy has the potential to significantly increase water consumption. Energy producers and consumers seek to evaluate their energy options and developing policies that apply appropriate financial carrots and sticks to various technologies to encourage sustainable energy production, including cost, carbon, and security considerations. Energy and water nexus needs to be part of this debate, particularly how communities will manage the trade-offs between water and energy at the local, national, and cross-border levels.

Although the energy and water nexus theme has been of interest to a handful of people in the Mediterranean region for two decades, it was only recently (in the past 5 years) brought up in a more serious way. Local governments are aware of the issue and specific efforts in specific regions have been carried out throughout the countries, and of course, with the awareness of the issue, challenges arise.

Energy and water integration in a single and efficient system is the main topic of the EdgeWise (Energy and Water Systems Integration and Management) project. The experimental pilot will be used to check the applicability and assess the socio-economic impact of the work developed by the research teams.

In Portugal, it is of major importance to change national policies in order to articulate energy and water sectors and to create beneficial synergies to increase both resources efficiency and to sustain the generations to come. 
The basic idea of the proposed scenario for urban areas is simple enough: water is energy intensive, and energy is water intensive, so addressing both in an integrated way should lead to innovative, more efficient solutions.

The public park located in Covilha (Portugal) city will be used to build a water-energy combined system to support the city’s night demand of water and electricity to power its public lights.

Figure 2: Energy Water Nexus pilot implementation site – Alexandre Aibeo Park, Covilha, Portugal (HWT: Upper water reservoir; LWT: Lower water reservoir; PV: Photovoltaics; WT: Wind turbine; PAT: Pump as turbine)

The general objective of the developed pilot is to transform solar and wind energy to gravitational potential energy (GPE) by raising water to a level higher than its reference level. The height difference of the already existing water reservoirs will be used to store energy by elevating water from the bottom of the park to the top. The work that will be used to elevate the water will be supplied by solar and wind sources.

Figure 2 represents the pilot in its most basic configuration. Two water reservoirs (HWT and LWT) are managed throughout the day taking into account two factors: the need for water by consumers and maximizing the energy storage capacity in the upper level reservoir. According to operation, during the day produced energy from sun (PV) and wind (WT) will be used to supply power to the pump in order to store the energy in the upper reservoir. During the night, the pump as a turbine (PAT) will produce energy to supply the public illumination in the park area. This kind of energy transformation is anticipated to be of interest to water and utility providers of mountain cities and towns.

Energy and water nexus research has a number of benefits when compared to traditional energy storage mechanisms that use an electrochemical approach. Water storage is low maintenance, low cost, environmentally friendly, and it comes with easily available components that do not require frequent replacements.

Renata Mikalauskiene
Malta College of Arts, Science and Technology (MCAST) Energy

ACKNOWLEDGEMENTS The author wishes to thank for their financial support the Malta Council for Science and Technology (MCST) (Grant ENM-2016-001) through the ERANETMED initiative of Member States, Associated Countries and Mediterranean Partner Countries (EdgeWise Project ID eranetmed_nexus-14-044).

If you have questions or comments concerning Renata’s post, please leave a comment below or send her an email.


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