From daytime irrigation to selling surplus energy: solutions to optimize the use of solar energy in irrigation communities
Hydraulics and Irrigation researchers present strategies for the use of energy in the Lower Guadalquivir Valley, which boasts the largest photovoltaic plant for self-provisioning
IMAGE:
RESEARCHERS JUAN ANTONIO RODRÍGUEZ, MAAIKE VAN DE LOO AND EMILIO CAMACHO FROM THE UNIVERSITY OF CORDOBA
view moreCREDIT: UNIVERSITY OF CORDOBA
Irrigation faces the challenge of making its activity more sustainable, both environmentally and economically. In this context, energy self-sufficiency is proposed as a path to follow for the agriculture of the future. The Lower Guadalquivir Valley Irrigation Community, covering almost 19,000 hectares and with more than 2,000 irrigators, began self-supplying through solar energy in 2019 through the installation of a 6-megawatt photovoltaic plant, the largest of all irrigation systems in Spain. This has made it a trailblazer and testing ground available to the scientific community as efforts are being made to shift towards an environmentally and economically sustainable irrigation model.
The most recent example is its close collaboration with the María de Maeztu Unit of Excellence's Hydraulics and Irrigation research group, in association with the University of Cordoba's Department of Agronomy (DAUCO), which has proposed different strategies to maximize the use of the solar energy it produces, prevent the surplus from being lost, and reduce dependence on external energy sources.
The researchers responsible for the study, Maaike van de Loo, Emilio Camacho and Juan Antonio Rodríguez, explain that more solar energy is currently produced than is used, generating a surplus of around 50%, while a secondary source is necessary to meet energy needs when solar energy is not being produced; at night, for example. To resolve this situation, two possible solutions have been studied that would contribute to reducing the volume of energy lost and optimizing its use, ideas having been published in the journal Renewable Energy.
The first one proposes a change in growers' habits, adjusting irrigation schedules to coincide with the daytime hours when solar energy is produced, and avoiding nighttime irrigation. This approach, the research team explains, represents a paradigm shift since traditionally the Lower Valley Community had opted for irrigation at night due to the advantages it entailed: cheaper energy rates and milder temperatures, which reduce water evaporation levels. However, the drop in energy costs thanks to the construction of the photovoltaic plant, and the expansion of drip irrigation, which reduces water consumption by up to 60% compared to other conventional methods (by allowing for more precise application, thereby minimizing losses) means that irrigators have reason to change their routines.
The strategy that the research group proposes is to abandon on-demand irrigation (24 hours of water availability) and concentrate its use in a space 8 to 12 hours, when there is sunshine, which would significantly increase the ready supply of photovoltaic energy, above 90%. The researchers clarify that, even if this model is implemented, it would always be necessary to have an additional energy source to supplement solar due to its dependence on weather and environmental conditions. However, in a region like Andalusia, with more than 3,000 hours of sunshine per year, the strategy would significantly reduce dependence on external sources and contribute to a more sustainable irrigation model, both economically and environmentally.
The second scenario is economic and consists of selling surplus energy, something that the Lower Valley Community has been doing since the plant's installation. An increase in solar energy production at the national and European levels, however, has led to lower prices, which reduces its profitability.
The study concludes that, thus far, there is no solution that guarantees 100% exploitation of solar energy, though it constitutes a valuable resource. Nevertheless, the researchers are confident that research like this, together with the experience of the Lower Valley Irrigation Community, can pave the way for the irrigation of the future, one capable of combining environmental protection with economic profitability by taking full advantage of the territory's potential.
JOURNAL
Renewable Energy
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Defining the optimization strategy for solar energy use in large water distribution networks: A case study from the Valle Inferior irrigation system, Spain
How to avoid wasting huge amounts of energy
Surplus heat from industry is a underused resource that can be used to purify some types of industry wastewater while providing heat to homes and businesses
IMAGE:
KIM KRISTIANSEN HAS JUST RECEIVED HIS DOCTORATE FROM THE NORWEGIAN UNIVERSITY OF SCIENCE AND TECHNOLOGY ON A TECHNOLOGY THAT CAN PUT TO WORK SOME OF THE WASTE HEAT THAT TODAY IS SIMPLY WASTED.
view moreCREDIT: PHOTO: ALEKSANDER STOKKE BÅTNES, NTNU
Norway wastes huge amounts of energy. Surplus heat produced by industry is hardly exploited at all.
Researchers at the Norwegian University of Science and Technology (NTNU) have been looking at the possibilities for doing something about this.
“Surplus heat from industrial processes is a huge resource,” says Kim Kristiansen.
He has just completed his PhD on a technology that can harness some of the surplus heat that currently goes to waste. Almost all the heat generated by industrial processes is currently released directly into the air or the ocean, and we are not talking about small amounts. In Norway alone, industry produces around 20 TWh of waste heat each year.
That number might not mean much to you, but according to the Norwegian Water Resources and Energy Directorate (NVE), this amount of energy corresponds to half of the electricity consumption of all Norwegian households combined. In other words, approximately the entire heating demand.
Kristiansen is part of the thermodynamics research group at PoreLab in the Department of Chemistry. Academic supervisor Signe Kjelstrup and research group manager Øivind Wilhelmsen are co-authors of the articles in question.
Drinking water as an added bonus
The technology also has another effect that may not be as relevant in Norway, but which might be a game changer in countries with limited drinking water.
“The technology doesn’t just recycle the waste heat energy, it can also purify the waste water produced by industry,” says Kristiansen.
In many parts of the world, drinking water is becoming an increasingly scarce resource.
“According to UNICEF, four billion people are already experiencing severe drinking water shortages for at least one month of the year, and there is a high demand for technology that can meet these challenges,” says Kristiansen.
A lack of drinking water is therefore a problem for approximately half of the world’s eight billion people.
Producing clean water
So what is this new technology?
“The waste water produced by industry is often contaminated. If we evaporate this impure water through small pores in a water-repellent membrane, the condensed water that emerges on the other side is drinkable,” says Kristiansen.
This method is best suited for purifying water with so-called non-volatile impurities, such as salt. This is in contrast to alcohols and a number of other organic substances that can evaporate along with the water through the membrane.
“The most important area of application for this technology is therefore desalination of seawater. The treatment of process water is not being ruled out, but it involves additional challenges depending on its content,” says Kristiansen.
So, the technology can produce drinking water, but what about exploiting the waste energy?
Exploiting temperature differences to pump up water
When water is heated on one side of the membrane, it evaporates and releases heat on the other side through condensation. A pressure difference may then arise between the two sides of the membrane
“The temperature difference is used to pump the water up, and the pressure difference represents mechanical energy that can be used to power a turbine,” says Kristiansen. The phenomenon is called thermal osmosis.
Seemingly simple, but ingenious.
“We have investigated the interactions between water and the pores in the membrane, and what happens when the water evaporates, is transported through the pores, and condenses,” says Kristiansen about the doctoral research.
He has designed theories on membrane properties and the effect they have on the entire process. He has also systematically measured this effect in the laboratory.
“The conclusion is that the technology has great potential. Through modification of the membranes, we can help address both the increasing challenges associated with energy efficiency requirements and the lack of clean drinking water,” says Kristiansen.
A Dutch idea
Kristin Syverud at the RISE PFI research institute is interested in improving the membranes used in this technology.
“The starting point for the work was an idea that TNO in the Netherlands gets the credit for,” says Kristiansen’s academic supervisor Signe Kjelstrup.
She is Professor Emerita and former Head Researcher at PoreLab – Centre of Excellence. TNO is an independent institute that works to translate research findings into real-life applications.
TNO experimented with the concept called ‘MemPower’ (simultaneous production of water and power) and the prototype was made at their facilities. The researchers wanted to collaborate but had no funding. The solution was to continue the project as open research at NTNU.
“Leen van der Ham from TU Delft got in touch with me and I introduced the idea to the group I then had at the Department of Chemistry, and later at PoreLab.”
Van der Ham took his PhD in Chemistry at NTNU a few years ago, which shows just how important it is to have contacts. They worked with Luuk Keulen, a student at TU Delft, and the research was continued by Kristiansen and Michael Rauter from PoreLab.
Practical challenges
“Industry is showing interest in the concept of membrane distillation, but so far, there are only a few pilot plants worldwide,” says Kristiansen.
The main reason industry is lagging behind academia is related to practical challenges associated with membrane technology, he explains. For example, this applies to the lifespan of membranes under harsh industrial conditions.
“A lot of work is being done internationally in both academia and industry to meet these challenges and commercialise the technology,” says Kristiansen.
The MemPower concept involves converting waste heat into mechanical energy based on differences in temperature.
“My impression is that industry is not yet fully aware of this concept and the opportunity it offers,” says Kristiansen.
One of the conclusions in the latest article is that the potential for energy production is competitive in relation to more established membrane-based energy processes. He believes this could help increase commercial interest.
Reference: Kristiansen, Kim and Wilhelmsen, Oivind and Kjelstrup, Signe, Thermo-Osmotic Coefficients in Membrane Distillation experiments and Theory for Three Types of Membranes. Desalination, Volume 586, 2024, 117785, ISSN 0011-9164, https://doi.org/10.1016/j.desal.2024.117785
Kim Roger Kristiansen at the lab in the Natural Science Building at the Norwegian University of Science and Technology (NTNU) Gløshaugen campus. Kristiansen studied membrane technology that can recover the energy in waste heat, and at the same time purify water.
CREDIT
Photo: Aleksander Båtnes/NTNU
USAGE RESTRICTIONS
JOURNAL
Desalination
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Thermo-osmotic coefficients in membrane distillation: Experiments and theory for three types of membranes
No comments:
Post a Comment