20 Oct A Smart Hybrid Energy System Grid for Energy Efficiency in Remote Areas for the Army
The current energy inefficiencies in relocatable temporary camps of the Armed Force troops create logistic challenges associated with fuel supply. The energy needs of these camps are primarily satisfied by diesel engine generators, which imply that a significant amount of fuel needs to be continuously provided to these camps, often built in remote areas. This paper presents an alternative solution, named Smart Hybrid Energy System (SHES), aiming towards significantly reducing the amount of fuel needed and minimizing transportation logistics while meeting camp energy demands. The SHES combines the existing diesel generators with solar power generation, energy storage, and waste heat recovery technologies, all connected to a microgrid, ensuring uninterrupted electricity and hot water supplies. All components are controlled by an energy management system that prioritizes output and switches between different power generators, ensuring operation at optimum efficiencies. The SHES components have been selected to be easily transportable in standard shipping 20 ft containers. The modularity of the solution, scalable from the base camp for 150 people, is designed according to available on-site renewable sources, allowing for energy optimization of different camp sizes in different climates.
The Armed Forces operate in remote locations for training and military operations, even under natural disaster conditions or in foreign territories during conflicts, and must be ready to deploy on short notices, in any climate and for prolonged periods. As such, they currently rely on relocatable temporary camps (RTCs) for their deployments through extreme operational and environmental conditions. To sustain operations, as there is no utility grid, RTCs depend on logistics for the continuous supply of fossil fuel (primarily diesel) as the main source of energy. Inefficiencies in current practices lead to vulnerabilities in energy infrastructures, such as shortfalls in power generation and higher requirements for fuel resupply, with the knock-on effect of greatly increasing the transportation logistics during operations. Moreover, RTCs typically use spot generation by connecting loads to a common set of generators, where each generator is oversized to satisfy peak loads, even when these loads are infrequent. Consequently, generators typically are selected at a significantly higher capacity, resulting in an inefficient and costly source of power, increased maintenance, and wet sacking, a condition resulting from poor fuel combustion.
In recent years, military engineers have therefore encountered several operational challenges associated with energy logistic convoys and infrastructure, limited supplies, and climate change. Scientific literature identified a spectrum of approaches and technologies to address energy consumption under these conditions. Few combinations of components have been proposed according to the site-specific characteristics, however, the definition of further integrated configurations remains rarely investigated, although it is evident that the Armed Forces could benefit from holistically assessing these approaches as integrated systems. Significant gains in the efficiencies of RTC utility systems (renewable energy systems; improved generators and energy storage or grid efficiency) and energy conservation measures (e.g., insulation of the camp tent fabric, building controls, etc.) would have an overall increasing benefit on the deployed operations. Meanwhile, stand-alone hybrid energy systems have been proposed as valuable means of supplying energy to remote areas, such as isolated rural villages, and for various other purposes, such as medical clinic practices or military operations. Some researchers investigated solutions aiming at reducing the dependency on fossil fuels during prolonged emergencies by proposing self-contained demonstration units that make use of hybrid generation from solar, wind, and biomass and, minimally, fossil sources. Some of these systems have already been introduced to the market, as described below. Besides microgrids, clusters of electricity sources and load operating systems are being used to improve the reliability of electrical grids, manage the addition of distributed clean energy resources like wind and solar photovoltaic generation, reduce fossil fuel emissions, and provide electricity in areas not served by centralized electrical infrastructure. Some models described the components of a microgrid, but not much is known about its behavior as a whole system. Some studies aimed to model microgrids at steady-state and study their transient responses to changing inputs. However, researchers have built a full-scale microgrid model, including the power sources, power electronics, and load and mains models.
One of the main challenges towards the development of isolated microgrids is the management of various devices and energy flows to optimize their operations, particularly regarding the hourly loads and the availability of power produced by renewable energy systems. Energy management systems could be a solution to tackle these issues. Regarding the provision of energy services with modular and transportable systems by making use of microgrid technology, some examples can be found in the market. The Cross-Power unit, e.g., uses modular hybrid wind and solar systems, integrated with battery storage, to produce electricity in remote locations. However, most of the existing solutions use black box intelligent energy management systems to ensure a continuous supply and avoid shortfalls in power generation.
Smart Hybrid Energy System (SHES) Design
The SHES is designed to work in stand-alone mode or connected to the local grid. The SHES combines into a single, integrated system of the following technologies: (a) photovoltaic (PV) array, (b) an energy storage system, (c) existing diesel generators, (d) waste-to-heat energy recovery system (WHRU) for space heating, (e) solar hot water (SHW) system for domestic hot water, and (f) energy management system (EMS) that actively monitors and manages base camp equipment and zones.
The reliable and energy-efficient system helps to manage generator output. By transforming an independently operating system of generators into a demand-managed microgrid, SHES provides power only where and when it is needed, instead of completely relying on fuel-burning generators. The system also provides the Armed Forces with critically needed power surety by utilizing intelligent load management technologies to prevent grid collapse in the event of generator fault, as the SHES prevents a stoppage of energy flow by shifting demand onto supporting generators if one generator fails. The system is designed to manage the energy needs of a 150 to 1500-person RTC, operating in a temperate climate zone and allowing for the occasional deployment to extremely hot or cold climatic zones. Finally, this paper considers the energy savings achievable through technologies that improve the accommodation’s insulation, such as a thermoreflective multilayer system developed for emergency architecture, or that provide additional layers of solar protection, reducing the heat transfer through the shelter exterior thus reducing the daily air conditioning loads and reliance on diesel fuel.
One of the main challenges towards the development of isolated microgrids is the management of the various devices and energy flows to optimize their operations, particularly regarding the hourly loads that must be served, and the availability of power produced by renewable energy systems depending on daily and seasonal variations. The SHES combines the existing diesel generators with solar power generation, energy storage, and waste heat recovery technologies, all connected to a microgrid, ensuring uninterrupted electricity and hot water supplies. The reliable, energy-efficient system helps to manage generator output. By transforming an independently operating system of generators into a demand managed microgrid, SHES provides power only where and when it is needed, instead of completely relying on fuel-burning generators. A critical part of designing SHES was understanding the electric and thermal load and generation profiles to identify the most cost-effective energy management strategy while maximizing the renewable generation, without significantly increasing the initial costs of system while considering army spatial and logistic requirements. It is crucial to identify the parts of the system that carry these loads at different times of the day and different seasons, particularly at peak loads. The peak electric load typically occurs during the warmest period of the year due to increased cooling loads, while thermal loads during the same period would be low due to the absence of heating requirements. For these purposes, various dispatching strategies were considered for energy management purposes of controlling generator and battery operation in periods of insufficient renewable energy to supply the load, including “cycle charging” and “load following” strategies. A cycle charging dispatching strategy was found to be the most cost-effective. The cycle charging strategy implies that the generator runs at its maximum power output when it is needed to serve the electrical loads, while any surplus electrical production is diverted towards charging the battery until the battery setpoint state of charge of 80% is reached. This is accomplished by selecting the optimal combination of power sources, based on fixed and marginal costs, to serve the electric and thermal loads at the minimum cost and excess electricity production, while still satisfying the operating reserve requirements. On the other hand, a load following strategy, which implies that the generator produces enough power only to serve the load while the battery is charged by the renewable sources, would be more cost-effective in situations where the renewable generation is comparable to the magnitude of the served load.
The SHES reduces the dependency on fossil fuel lowering the environmental footprint of RTCs since the transportation logistics are minimized and the consumption of vehicle-fuel transporting fuel to the base campsite is also reduced. The generators, rather than being fueled by diesel (as currently done in Canadian Armed Forces), could be powered by LPG (Liquefied Petroleum Gas) to produce lower amounts of harmful greenhouse gases. However, the risks due to the transportation of more hazardous materials must be considered.
This is an excerpt of the journal article: A Smart Hybrid Energy System Grid for Energy Efficiency in Remote Areas for the Army, by Umberto Berardi, Elisa Tomassoni and Khaled Khaled. Published: 05 Mai 2020 in Energies 13(9), 2279; DOI: https://doi.org/10.3390/en13092279 under a Creative Commons Attribution License (CC BY 4.0).