Search

This paper discusses the application of distributed energy resources (DERs) at water resource recovery facilities (WRRF). The DERs considered include solar photovoltaic (PV) systems, biomass electricity generation, and energy storage systems (ESS). The financial and demand management implications of the deployment of various DER combinations are analyzed. The load profile of a single plant is studied in order to draw conclusions regarding the optimal size for energy storage solutions based on the goals of the WRRF. A case study of a Medium sized WRRF, located in a large metropolitan area, is used to compare different financial and technical implementation strategies. An ideal combination of DERs is determined based on analysis of various scenarios for nine distinct use cases. The overarching goal of this paper is to understand the potential of various combinations of DERs for managing peak demand and resilience at WRRFs. Elements in the financial models are compared to determine the combination that creates a financially viable project while providing tangible benefits in resilience and/or demand management to the WRRF. • Energy efficiency is key for urban regions to combat global warming. • Distributed energy resources (DERs) improve resiliency during power failures. • Energy efficiency is possible through deployment of DERs and better use of biogases • Distributed energy resources (DERs) improve resiliency during power failures. [ABSTRACT FROM AUTHOR]

Sorption thermal energy storage (STES) is perceived as one prospective way of thermal energy storage (TES) owing to the advantages of high energy density, negligible heat loss, flexible working modes and long-term storage capability. Based on STES, this paper exhibits an innovative resorption thermal energy storage (RTES) system, and the experimental prototype is established for heat and refrigeration cogeneration. Working pair of MnCl 2 CaCl 2 NH 3 is chosen, 4.8 kg MnCl 2 and 3.9 kg CaCl 2 impregnated in expanded natural graphite treated with sulfuric acid are filled in two sorption beds respectively. Experimental results indicate that the largest energy storage density reaches 1706 kJ/kg when charging and discharging temperature are 160 °C and 30 °C, respectively. The maximum average cooling power achieves 1.07 kW during discharging phase and corresponding SCP is 27.33 W/kg within the overall cycle period. When charging temperature increases from 135 °C to 160 °C, the energy efficiency of the resorption system for heat and refrigeration cogeneration augments steadily from 0.72 to 0.87 while the exergy efficiency rises slowly from 0.29 to 0.35. [ABSTRACT FROM AUTHOR]

Abstract: Portugal is a country with an energy system highly dependent on oil and gas imports. Imports of oil and gas accounted for 85% of the country’s requirements in 2005 and 86% in 2006. Meanwhile, the share of renewable energy sources (RES) in the total primary energy consumption was only 14% in 2006. When focusing only on electricity production, the situation is somewhat better. The share of RES in gross electricity production varies between 20% and 35% and is dependent on the hydropower production in wet and dry years. This paper presents, on a national scale, Portugal’s energy system planning and technical solutions for achieving 100% RES electricity production. Planning was based on hourly energy balance and use of H2RES software. The H2RES model provides the ability to integrate various types of storages into energy systems in order to increase penetration of the intermittent renewable energy sources or to achieve a 100% renewable island, region or country. The paper also represents a stepping-stone for studies offering wider possibilities in matching and satisfying electricity supply in Portugal with potential renewable energy sources. Special attention has been given to intermittent sources such as wind, solar and ocean waves that can be coupled to appropriate energy storage systems charged with surplus amounts of produced electricity. The storage systems also decrease installed power requirements for generating units. Consequently, these storages will assist in avoiding unnecessary rejection of renewable potential and reaching a sufficient security of energy supply. [ABSTRACT FROM AUTHOR]

This paper proposes an energy management strategy for a residential microgrid comprising photovoltaic (PV) panels and a small wind turbine. The microgrid is connected to the main grid, allowing for a controlled power exchange through a battery system and its control strategy. As input data, the proposed control strategy uses the battery state of charge (SOC), the power at each microgrid node as well as the load and renewable generation forecasts. By using forecasted data and correcting any forecasting errors according to the SOC of the battery, the strategy manages to make a better use of the battery resulting in a better grid power profile. The simulation of the system using a one-year data period shows that the proposed energy management strategy results in a better grid power profile for a given storage system when compared with other state-of-the-art strategies. Finally, the proposed strategy was experimentally validated in the microgrid built in the Renewable Energy Laboratory at the UPNa. [ABSTRACT FROM AUTHOR]

To reduce global greenhouse gas emissions, the world must find intelligent solutions to maximise the utilisation of carbon-free renewable energy sources. In this paper, multi-agent reinforcement learning is used to control a microgrid in a mixed cooperative and competitive setting. The agents observe fluctuating energy demand, dynamic wholesale energy prices, and intermittent renewable energy sources to control a hybrid energy storage system to maximise the utilisation of the renewables to reduce the energy costs of the grid. In addition, an aggregator agent trades with external microgrids competing against one another and the aggregator to reduce their own energy bills. For this, the algorithm deep deterministic policy gradients (DDPG) and multi-agent DDPG (MADDPG) are used to compare the use of a single global controller versus multiple distributed agents, along with the single and multi-agent variants of distributional DDPG (D3PG) and twin delayed DDPG (TD3). The research found it is significantly more profitable for the primary microgrid to sell energy on its own terms rather than selling back to the utility grid, and is also beneficial for the external microgrids as they also reduce their own energy bills. The methods that produced the greatest profits were the multi-agent approaches where each agent has its own reward function based on the principle of marginal contribution from game theory. The multi-agent approaches were better able to evaluate their performance controlling individual components of the environment which allowed them to develop their own unique policies for the different types of energy storage system. • Novel use of MADDPG for mixed cooperative and competitive microgrid environment. • Compare use of a central controller or multiple distributed agents in microgrids. • Hybrid energy storage system for long, medium, and short-term storage. • Case studies for renewable utilisation and trading with neighbouring microgrids. • Showcase the benefit of using rewards based on marginal contribution in a MAS. [ABSTRACT FROM AUTHOR]

Desalination has become imperative as a drinking water source for many parts of the world. Due to the large quantities of thermal energy and high quality electricity requirements for water purification, the desalination industry depends on waste heat resources and renewable energy sources such as solar collectors, photovoltaic arrays, geothermal and wind and tidal energy sources. Considering the mismatch between the source supply and demand and intermittent nature of these energy resources, energy storage is a must for reliable and continuous operation of desalination facilities. Thermal energy storage (TES) requires a suitable medium for storage and circulation while the photovoltaic/wind generated electricity needs to be stored in batteries for later use. Desalination technologies that utilize thermal energy and thus require storage for uninterrupted process operation are multi-stage flash distillation (MSF), multi-effect evaporation (MED), low temperature desalination (LTD) and humidification–dehumidification (HD) and membrane distillation (MD). Energy accumulation, storage and supply are the key components of energy storage concept which improve process performance along with better resource economics, and minimum environmental impact. Similarly, the battery energy storage (BES) is essential to store electrical energy for electrodialysis (ED), reverse osmosis (RO) and mechanical vapor compression (MVC) technologies. This research-review paper provides a critical review on current energy storage options for different desalination processes powered by various renewable energy and waste heat sources with focus on thermal energy storage and battery energy storage systems. Principles of energy storage (thermal and electrical energy) are discussed with details on the design, sizing, and economics for desalination process applications. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a novel energy storage system which stores excessive energy in the form of compressed air and thermal heat. It is different from the conventional compressed air energy storage (CAES) technology in that the new system allows trigeneration of electrical, heating and cooling power in energy releasing process. Uniquely, the cooling power from this system is generated by direct expansion of compressed air instead of the use of absorption chilling technology. In addition, the system can meet the end users’ demands for electricity, and heating and cooling powers through controlling the inlet pressure and temperature of an air based expander. A new parameter, the comprehensive efficiency, is proposed to evaluate the performance of the trigeneration system. Energy requirements of a small office building located in Chicago is used for the evaluation. The results show that the comprehensive efficiency of the system is very high (∼50%) in winter months when no cooling is needed. In summer months, due to the high power consumption in air compression process and inefficient expansion of the compressed air (for cooling power production) the comprehensive efficiency decreases to about 30%. However such a value is still higher than the conventional trigeneration system based on absorption chilling technology. The system is therefore very promising for practical applications particularly for the use of renewable energy due to good flexibility and simple configuration. [Copyright &y& Elsevier]