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The present research focuses on heat recovery from hot kitchen wastewater to fulfil the dual objective of reducing energy consumption and CO2 emissions, while simultaneously improving the fat, oil and grease (FOG) removal efficiency of the grease trap (GT). A GT was retrofitted with a novel heat exchanger design (termed as a hybrid GT device) to enhance wastewater thermal recovery and FOG removal capabilities. Hot wastewater containing FOG was assessed in a full-scale experimental GT. The governing parameters of temperature, mass flow rate and FOG content were monitored. Results indicate that the hybrid GT improves FOG removal performance by lowering the temperature of GT hot wastewater by approximately 25%. The hybrid GT enables improvement in energy efficiency and cost savings for commercial kitchens/wastewater generators, lowering the carbon footprint and cost of food preparation. [ABSTRACT FROM AUTHOR]

Coupling pressure management strategies with energy generation in water distribution networks could provide an opportunity to reduce energy dependency. Recent laboratory prototypes attested the capability of Pump-As-Turbines (PATs) to manage pressure and generate energy in these settings. When selecting an optimal pump/PAT unit from the market to maximize energy recovery at a Pressure Reduction Valve (PRV) site, the first step usually represents the definition of its optimal design point in turbine mode, i.e., its best efficiency point (BEP) for a selected rotational speed. There are many very different strategies on how to define the optimal design point of PATs, and by far the simplest is to define it as the average operating condition (AOC) at an investigated site. However, the literature does not provide the answer if such a definition is valid. More importantly, of whether it is valid for a general case, meaning regardless of the site's size, level of variations of operating conditions and other site-specific characteristics. To address this research question, a large database of high-resolution recordings from 38 PRVs was compiled. The optimal design point for each PRV was assessed using an upgraded version of a methodology from the literature employing the Nelder–Mead Simplex Direct Search algorithm and hydraulic control strategy. The upgrade includes the addition of a new design variable representing the maximal operating flow of the PAT. The optimization of this variable also results in the optimization of the size of the generator. The results suggest that the selection of the optimal PAT from the market using the AOC could lead to the selection of the same models as when using the true theoretical optimal design point in the case of 77.14% of the investigated sites. Furthermore, the PAT models selected using the AOCs of the investigated sites were at least the second optimal for 99.14% of sites. Consequently, it was concluded that, for practical purposes (i.e., when a PAT database is not available and the optimal model is found from pump selection charts), it is appropriate to use the AOCs of the investigated site for the selection. [ABSTRACT FROM AUTHOR]

One of the hardest challenges in irrigation systems is to reduce the use of water resources. The goal "more crop per drop" has fostered the improvement of hydraulic infrastructure by replacing old open channel networks with pressurized systems (e.g., drip and sprinkler irrigation). This has resulted in reduced water losses, as well as the possibility for farmers to benefit from on-demand water. On the other hand, this improvement in water efficiency has controversially resulted in a large increase in energy consumption, since pressurized systems demand large flows with high pressures. The high energy requirements, along with the investment and operational costs, may compromise the viability of such irrigation systems. Several strategies to save both water and energy resources have, therefore, been proposed in the recent literature. Among these, the exploitation of excess pressure to produce energy by means of energy production devices (EPDs) has been proven to be a very effective strategy. Pumps-as-turbines (PATs) are, by far, preferred over traditional EPDs, such as pico- or micro-turbines, being very cost-effective solutions. In this study, the optimal location of PATs within an irrigation system is investigated with reference to a whole irrigation season. A case study network, the Zújar Canal irrigation district, is considered, for which accurate records of hourly water demands are available due to a diffuse telemetry system over the irrigation area. The aim of the optimization is to search for the best number and location of PATs within the irrigation network in order to maximize the energy production and minimize the investment costs. The hydraulic resolution of the network is coupled with the optimal location problem in one single mathematical model and the optimization procedure is performed via the use of a global optimization solver. The promising results in terms of the hydropower potential prove the effectiveness of the PAT installation within the case study network. [ABSTRACT FROM AUTHOR]

The potential for the generation of pico- and micro-hydropower through hydraulic energy recovery has been demonstrated across many sectors of the water-energy-food nexus, often termed hidden hydropower. The potential to recover energy from hidden hydropower in water supply, crop production, food processing, and energy production has been demonstrated via numerous in-depth case studies, regional assessments, and physical experiments. This paper presents a holistic overview of the potential role and impacts of micro-hydropower energy recovery on the water-energy-food nexus in the context of climate change. The paper comprises a review and synthesis of the available literature. The paper outlines the potential impacts of hidden hydropower on cost of water supply, energy and food production, considering also the potential impacts on crop yield and food supply. Policy and technological barriers to the exploitation of hidden hydropower resources within the nexus are outlined and recommendations to overcome these are provided. The results of this investigation highlight the potential of micro-hydropower energy recovery in water systems to reduce energy consumption by 0.005–3.7% across various sectors and regions, with consequent impacts in the operating and consumer costs of food, water and energy, as well as on the CO2 emissions of these activities. This hidden hydropower has the potential to ease the pressures of the water-energy-food nexus and is an important element of the route towards sustainability within the nexus. [ABSTRACT FROM AUTHOR]