The Energy-Water Nexus and a New Paradigm for Integrated Resource Management

May 8, 2024

Incorporating demand response programs could provide a solution for effective energy management


As the world’s energy system switches from more than 200 years of fossil fuel dominance to renewable energy sources, there’s a growing need to integrate renewable energy systems to the traditional power grid and the way we consume energy. Over the past decade, as technology has advanced, the prices for wind and solar generation have plunged with solar now the cheapest form of electricity generation in history. For the Gulf, a region bestowed with plenty of sunlight, renewables are a sensible way forward.


But the proliferation of distributed energy resources necessitates the radical transformation of how power systems operate, particularly since managing the impact of integrating renewable energy sources is a tricky task. 


The energy available from sun, wind, waves, and tides varies in ways which may not match variations in consumer energy demand. Assimilating these fluctuations can affect the operation and economics of electricity networks and markets. Much like the weather, electricity consumption can be reasonably well predicted, but not controlled. Reacting to demand in traditional fossil fuel power stations is as easy as adjusting supply: burning more fuel to produce steam to spin a turbine to run a generator. Making more electricity from non-renewable resources can happen at the relative push of a button.


Demand response applications can step up here, playing a critical role in shaping the day-ahead scheduling of electricity markets.


A team of researchers led by Dr. Ameena Saad Al-Sumaiti, Associate Professor, from Khalifa University’s Advanced Power and Energy Center (APEC) has developed a model that coordinates the operation of grid-connected water desalination plants and the operation of renewable-rich power systems with demand response options. The team includes Mohamed Elsir, Graduate Research and Teaching Assistant; and Prof. Mohamed Shawky El Moursi,  Director of APEC . Also participating: Ali Taleb Al-Awami from Saudi Arabia’s Interdisciplinary Research Center for Smart Mobility and Logistics. Their simulation results show that their system’s efficiency is enhanced by employing energy flexibility of water desalination, minimizing cost, facilitating the integration of renewable energy sources and smoothing the fluctuation in hourly electricity prices.


Their results were published in Applied Energy, a top 1% journal in the fields of engineering and environmental science.


This innovative approach, featuring hybridized operations of energy storage systems, enhances power system operation and avoids the need for additional peak-load power plants. When everyday consumers need power, it is supplied by renewable sources; but when it isn’t. the energy can still be generated and supplied to desalination plants instead. The goal is to meet water demand and power loads: Desalinated drinking water can be stored much more easily than electricity and it is cost effectively.


The research team also notes that significant attention has been focused on the energy-water nexus and the inter-dependencies between power and water systems. The power and water systems can mutually benefit each other: There’s the potential for water facilities’ responsive electrical loads to offer much-needed flexibility to power system operations. The potential is vast when water systems consume significant portions of a nation’s total electricity consumption.


Models already exist to reduce the curtailment of renewable energy sources during periods of oversupply by co-optimizing the scheduling of both systems in a centralized entity. However, these models can be enhanced with considering the role of demand response.


“Demand response indicates that end-use consumers can be motivated to positively change their electricity consumption based on a coordination program or tariff,” Dr. Al-Sumaiti said. “This tariff is influenced by the conditions of the electricity market. Demand response applications could reduce the demand peak and price volatility of the market.”


Demand response involves shifting or shedding electricity demand to provide flexibility in power markets, helping to balance the grid. In a smart grid, demand response programs can manage desalination plants’ energy consumption. Given the energy-intensive nature of desalination (and reverse osmosis is one of the least energy-consuming methods), running these facilities during times of low demand and therefore lower energy prices, can make this process more cost-effective and less taxing on the overall power grid.


Sounds simple, but implementing demand response and day-ahead scheduling in a smart grid is a complex task that requires advanced forecasting techniques and optimization algorithms. For everything to work, accurate forecasting of the next day’s energy demand, energy prices, and renewable energy-generation potential are essential. The next step is to plan the desalination plants’ operation accordingly, scheduling high-energy processes for the most advantageous times.


The KU research team took a novel approach, coordinating the day-ahead operation of desalination plants within the operation of power systems, incorporating a demand-response bidding framework. The teams’ model includes a centralized scheduling entity to organize the operation of both power and water system based on the received demand-response offers and the operational constraints of desalination plants. In addition, the proposed structure considers the energy flexibility of these plants and their associated components, such as water storage tanks, to influence system flexibility without compromising the reliable supply of water services.


In this context, the “offers” or “bids” refer to proposals made by demand-response aggregators to the centralized entity representing the willingness and capacity of their customers to reduce their load in a variety of ways. These offers are characterized by specific parameters related to each demand-response option and can include things like the amount of power that can be reduced, the price required for that reduction, and certain constraints or limitations. Each aggregator represents a group of customers that can contribute to demand response.


Customers could reduce their energy usage overall, without shifting this reduction to other times or shift their energy usage from peak hours to off-peak hours. Those with their own power generation sources (such as solar panels) can reduce the need for grid power, while those with energy storage can charge their batteries during off-peak hours and then discharge during peak hours. For water desalination plants, operation can be adjusted to reduce and shift power consumption in response to electricity prices.


Once all the bids are in, the information is used to clear the day-ahead electricity market. This involves scheduling the generation and consumption of electricity for the next day, aiming to balance supply and demand in the most cost-effective way.


The research team’s framework, formulated as a mixed-integer linear programming problem, offers a functional solution to demand response due to its high solution efficiency and significant computational time savings. The simulation results demonstrate that more flexible options can be made available and available energy resources can be scheduled to minimize system operation costs, maximize the harvesting of renewable energy sources generation, and reduce peak demand in the day-ahead energy market. Plus, the model substantially reduced electricity price volatility and increased revenues for aggregators.


“We recognize, however, that the scheduled operation of water desalination plants may not necessarily be the optimal solution here,” Dr. Al-Sumaiti said. “Future research could expand the operation model to handle more dynamic characteristics, such as varying hydraulic and osmotic pressures applied on the reverse osmosis membrane, as well as incorporate models for water and hydrogen networks. This would further enhance the adaptability and effectiveness of our proposed coordinated operation model, potentially providing even greater benefits for power systems and sustainability initiatives.”


The work has the potential to support the UAE’s strategic economic goals by enhancing the overall effectiveness of managing energy and water resources within a smart grid framework focused on demand-side management.


Jade Sterling
Science Writer
8 May 2024