3 item(s) found.

Desalination for agriculture using wind energy in Gran Canaria [Illustrations of MuSIASEM]

Desalination for agriculture using wind energy in Gran Canaria [Illustrations of MuSIASEM]

UAB & ITC

Aim of the case study

The aim of this pilot study is to define a procedure for integrated and multi-level accounting of the nexus (water, energy, food and land use) in relation at the use of freshwater from desalination powered by windmills to irrigate crops in a farm in Gran Canaria.

 

Innovative results

This case illustrates how to implement a Water-Energy-Food (WEF) NEXUS assessment using the MuSIASEM 2.0 approach: It shows the usefulness of the tool with some clear evidences as example of the type of outputs obtained. It explains in details the various steps required for quantifying the production of energy, water and food and the associated requirements and resources. It explains how to make a system representation in order to arrange the elements required to represent the various relations of exchange within the WEF system and between the WEF system and outer systems (purchased water, electricity or crops sold to the market). This figure (next page) makes it possible to distinguish between functional and structural elements useful to scale up the information, or to make extrapolations of the analysis to other territories.

The innovative analysis based on the concept of “processor” – a data array describing the profile of expected inputs and outputs, that can be scaled across functional and structural elements - makes it possible to integrate:

  • technical analysis (technical coefficients);
  • economic analysis (costs and revenues in monetary terms);
  • biophysical analysis of the external constraints (requirement of inputs on the supply side and sink capacity).

 

Policy relevant insights

Even though the contribution of alternative energy to generate an alternative fresh water source improves the productivity of the agricultural system (an important aspect in the Canary Archipelagous) the results of the analysis carried out in this pilot case flags two relevant aspects to consider, when assessing this technology:

  1. desalination using wind energy is economically viable in this case only because of the existence of high agricultural subsidies making it possible to cover the high costs of this type of freshwater source. So the viability of this system elsewhere depends on the level of water scarcity and the possibility of providing subsidies to agricultural production.
  2. the considered WEF system is not fully self-sufficient, it still relies on water and electricity from external suppliers.

 

Future steps

In the rest of the project we will develop more complex analysis and carry out participatory processes to test the usefulness of this approach in real situations.

Location

Gran Canaria
Spain

Resources

The Water-Energy Nexus Issue

The Water-Energy Nexus Issue

The Magic Nexus team

There is an increasing demand for energy to alleviate water scarcity pressures, and, vice-versa, a growing water footprint required to produce many energy forms – including new energy technologies. The governance of water and energy then is crucial if we are to safely manage these finite resources into the future.

In our first article, Zora Kovacic explores the origins of the term ‘nexus’ from its original use spearheaded by the food and beverage industry as part of the ‘green growth’ agenda, to become attached to applications as diverse as water modelling to multidisciplinary social-ecological systems analysis initiatives today. She uses the context of these varied applications to question whether the ‘nexus’ concept will help or hinder future water governance efforts.

Broaching the topic of hidden water flows, Maddalena Ripa and Violeta Cabello crunch the numbers to investigate the characteristics and size of an often invisible, yet important water flow – non-consumptive use in the energy sector.  These authors highlight the shortcomings and challenges in quantifying water flows in the energy sector today, and break down the sectors that are not – and should be - properly accounted for. The article then explains how we can improve water governance using better-defined and more comprehensive accounting methods.

Finally, Juan de La Fuente and Baltasar Peñate explore the topic of desalination as a water-energy nexus technology in the Canary Islands, Spain. These authors explain how this controversial technology, known for its large energy footprint, is a viable technology in cases where renewable energy sources are readily available. They show how the Canary Islands archipelago has alleviated its water scarcity problem using desalination technologies, thanks to solar and wind resources available in the area together with effective management to balance costs, energy availability and environmental effects.

We hope you enjoy this our final issue for 2018. Don’t forget to subscribe to receive future issues coming in 2019. You can subscribe at the bottom of the homepage https://magic-nexus.eu/.

Desalination is a viable nexus technology: but local conditions are key

Desalination is a viable nexus technology: but local conditions are key

Juan A. de La Fuente and Baltasar Peñate

The world population is expected to increase from the current 8.5 billion to 11.2 billion by 2100 (World Population Prospects, United Nations 2017). By 2050, global demand for energy will nearly double, while water demand is set to increase by over 50%. To overcome the increasing constraints the world faces, we need to rethink how we produce and consume energy in relation to the water sector.

The authorities responsible for water and energy are generally separated. Each has its own priorities and there seems to be little incentive to collaborate in the planning and development of new policies. At the same time, the water and energy sectors have always operated independently and there may be some resistance to a better integration of both sectors. Often, studies on the interconnection between water and energy have been initiated and driven by specific local circumstances, such as water and energy crises.

Seawater desalination is an important option for addressing the world's water supply challenges, but current desalination plants use huge quantities of energy causing several environmental issues. The energy intensity of desalination processes has dramatically decreased over the past 30 years, from slightly more than 15 kWh/m3 in the 1970s to approximately 2.5 kWh/m3 today thanks in large part to reverse osmosis (RO) technology improvements. Still, several physical constraints limit the ability to reduce the energy intensity of RO much further. This means that energy efficiency in RO has almost reached its biophysical limits.  

Brine discharge into the sea can have a negative environmental effect on the marine ecosystems due to its high salt concentration and other chemicals. Devices like Venturi diffusers for brine discharge can be used to improve the dilution process and reduce their environmental impact. It has been shown that the capacity to improve the dilution of Venturi system is greater than 2.3 times the dilution obtained with conventional diffusers. Another option could be the valorisation of brine, by using it for the culture of the microalgaes for the production of molecules such as β-carotene and polyunsaturated acids. The biomass obtained can be used in animal nutrition and Nutraceutics.

It is very likely that the water issue will be considered, like fossil energy resources, to be one of the determining factors of world stability. Desalination processes involve a recurrent energy expense which few of the water-scarce areas of the world can afford. Even if oil were much more widely available, could we afford to burn it in such a manner so as to provide everyone with fresh water? Given the current understanding of the greenhouse effect and the importance of carbon dioxide levels in the atmosphere, environmental pollution caused by burning fossil fuels for desalination is a major concern.

Renewable energy (RES) technologies, mostly solar and wind energy systems, can provide access to a cost-effective, secure and environmentally sustainable supply of energy that can be used for water desalination. As RES technologies continue to improve, and as freshwater becomes scarce and fossil fuel energy prices rise, utilising RES for desalination becomes more viable economically. RES may provide water desalination cost reductions due to lower greenhouse gas emissions. For example, a seawater RO desalination system operating on traditional fossil fuel-based energy sources produces 1.78 kg and 4.05 g of CO2 and NOx per 1 m3 of desalted water, which can be reduced to 0.6 kg/m3 – 0.1 kg/m3 and 1.8 kg/m3 – 0.4 kg/m3, respectively, with electricity generated from wind or solar energy  (Raluy RG, Serra L, Uche J. 2005. Life cycle assessment of desalination technologies integrated with renewable energies. Desalination 183(1–3):81–93).

On the other hand, the role that desalination could play in the integration of electricity produced by renewable sources in the electricity grid is also an interesting topic.

The major constraint on increasing penetration of RES is their availability and intermittency, which can be addressed through using energy storage or smart control, when available, to balance renewable energy generation with energy demand.

The Canary Islands archipelago in Spain is a perfect example of how a region with water shortage and presence of RES resources has alleviated its water scarcity problem using desalination technologies, exploiting in turn the sun and wind resources available in the area.

The water – energy nexus has been one of the key R&D lines of the Canary Islands Institute of Technology (ITC). The ITC has developed and tested prototypes of different renewable energy driven desalination systems, operating in off-grid mode, since 1996. The ITC facilities in Pozo Izquierdo (Gran Canaria Island) are an ideal platform for testing RES desalination systems thanks to the excellent local conditions: direct access to seawater, annual average wind speed of 8 m/s, average daily solar radiation of 6 kWh/m2. Up to 18 different combined systems of renewable energy generation and desalination processes have been tested at the ITC.

Depending on the local environmental conditions, regulation and policy, desalination is a viable technology where RES resources are readily available. With planning and an adequate policy, desalination should be an alternative water resource. However, the energy dependence and the relatively high water cost must be analysed on a case by case basis before proposing specific arrangements.