This paper presents a co-simulation platform which combines a building simulation tool with a Cyber-Physical Systems (CPS) approach. Residential buildings have a great potential of energy reduction by controlling home equipment based on usage information. A CPS can eliminate unnecessary energy usage on a small, local scale by autonomously optimizing equipment activity, based on sensor measurements from the home. It can also allow peak shaving from the grid if a collection of homes are connected. However, lack of verification tools limits effective development of CPS products. The present work integrates EnergyPlus, which is a widely adopted building simulation tool, into an open-source development environment for CPS released by the National Institute of Standards and Technology (NIST). The NIST environment utilizes the IEEE High Level Architecture (HLA) standard for data exchange and logical timing control to integrate a suite of simulators into a common platform. A simple CPS model, which controls local HVAC temperature set-point based on environmental conditions, was tested with the developed co-simulation platform. The proposed platform can be expanded to integrate various simulation tools and various home simulations, thereby allowing for co-simulation of more intricate building energy systems.

This work addresses the development and construction of a sustainable alkaline membrane fuel cell (SAMFC). The SAMFC couples an alkaline membrane fuel cell (AMFC) with a hydrogen generation reactor that uses recycled aluminum from soda cans to split the water molecule through the oxidation of aluminum catalyzed by sodium hydroxide. An innovative cellulosic membrane supports the electrolyte, which avoids the undesirable characteristics of liquid electrolytes, and asbestos or ammonia that are substances that have been used to manufacture alkaline electrolyte membranes, which are knowingly toxic and carcinogenic. Aluminum is an inexpensive, abundant element in the earth’s crust and fully recyclable. Oxygen is supplied to the cell with atmospheric air that is pumped through a potassium hydroxide (KOH) aqueous solution in order to fix CO 2 , and in this way avoid potassium carbonate formation in order to keep the cell fully functional. A sustainable alkaline membrane fuel cell (SAMFC) system with one unitary cell, the reactor, and CO 2 purifier was designed and built in the laboratory. The results are presented in polarization and power curves directly measured in the laboratory. Although recycled aluminum was used in the experiments, the results demonstrate that the cell was capable of delivering 0.9 V in open circuit and approximately 0.42 W of maximum power. The main conclusion is that by allowing for in situ sustainable hydrogen production, the SAMFC could eventually become economically competitive with traditional power generation systems.

Wastewater treatment plants (WWTPs) are a significant energy consumer, yet there are several opportunities of implementing on-site power generation systems. Within the treatment process, the high flow rate of effluent is produced and discharged to a nearby water body by gravity. Thus, hydro turbines can be utilized to generate power in such application due to a difference in elevation and high flow rate. This paper presents a case study of introducing a hydro turbine in wastewater treatment plant in Wisconsin and evaluating the power output in addition to determining the energy savings. The wastewater treatment plant considered in this study has an effluent flow rate of 190 MGD (million gallons per day) and elevation difference of 3 meters (10 feet) between the final stage of treatment and the discharge point. Based on the aforementioned parameters; hubless rim-drive Kaplan type hydro turbine (RDT) is the optimal choice to be used in such application. The RDT is designed and optimized by using in-house code. A computational fluid dynamics (CFD) software is applied to evaluate the performance of the proposed model, and the system is simulated through HOMER software to validate the results generated by the CFD. The expected savings is estimated to be 1,564 MWh/year.

In order to reduce CO 2 emissions in the residential sector, the installation of photovoltaics (PV) has been increasing extensively. However, such large-scale PV installations cause problems in the low-voltage distribution grid of the residential sector, such as PV related voltage surges. In this study, the utilization of suppressed PV output through energy storage devices was proposed. Using demand side energy storage devices reduces voltage surge, transmission loss, and CO 2 emissions from the residential buildings. The objective of this study was to add voltage constraints of the low-voltage distribution grid to an operational planning problem that we developed for the residential energy systems, and to quantitatively evaluate the potential of heat pump water heater (HP) to utilize the PV surplus electricity, while considering the electrical grid constraints based on the minimization of CO 2 emissions. We found that when a 4.5 kW HP with 370 L storage, which utilizes PV output, was added to the system, the reduction in CO 2 emissions was more than twice compared with that in the case of adding 4 kWh battery (BT) to a PV and gas fired water heater configuration. Further, the effect of utilizing the suppressed PV electricity by HP was almost equivalent to that by the BT. Therefore, the potential of HP in utilizing PV surplus electricity is higher than that of the BT in terms of CO 2 emissions reduction in the residential sector.

Cyber-physical systems (CPS) are smart systems that include engineered interacting networks of physical and computational components. The tight integration of a wide range of heterogeneous components enables new functionality and quality of life improvements in critical infrastructures such as smart cities, intelligent buildings, and smart energy systems. One approach to study CPS uses both simulations and hardware-in-the-loop (HIL) to test the physical dynamics of hardware in a controlled environment. However, because CPS experiment design may involve domain experts from multiple disciplines who use different simulation tool suites, it can be a challenge to integrate the heterogeneous simulation languages and hardware interfaces into a single experiment. The National Institute of Standards and Technology (NIST) is working on the development of a universal CPS environment for federation (UCEF) that can be used to design and run experiments that incorporate heterogeneous physical and computational resources over a wide geographic area. This development environment uses the High Level Architecture (HLA), which the Department of Defense has advocated for co-simulation in the field of distributed simulations, to enable communication between hardware and different simulation languages such as Simulink ® and LabVIEW ® . This paper provides an overview of UCEF and motivates how the environment could be used to develop energy experiments using an illustrative example of an emulated heat pump system.

With the shortage of fossil fuels and its negative effects on the environment, solar energy as one type of renewable energy has attracted increasing attention both socially and politically. There are two approached to use solar energy for generating electricity, i.e., using solar energy to directly to make work or integrating solar energy into fossil-fueled plant. The solar-aided coal-fired power generation (SACPG) mechanism is proven an effective way to use solar energy efficiently. In this paper, SACPG system and solar-alone parabolic trough CSP plant are modelled respectively. A comparison discussion related to TES system between SACPG system and solar-alone CSP plant is presented. The aim is to find what role of TES system will play in these two different systems. Through analysis, the role TES system plays varies in solar-alone power generation system and SACPG system. For solar-alone power generation system, the main function for TES system lies in storing surplus solar heat. Besides, there exists an optimum loop number with highest annual SEE with a specific TES hour. However, TES system for SACPG system not only stores the surplus solar heat, but also adjusts working condition. With the help of TES system, the working condition could be set as the high-pressure extraction steam could be totally replaced by solar heat. By doing so, annual solar power generation and annual SEE could be improved compared with that without TES system.

Nuclear reactor systems present a promising sustainable energy source for the future. Simply, a nuclear reactor heats a coolant that powers a turbine to create electricity. The coolant then can either be re-cooled or can be used for process heat applications. By utilizing the heat off the reactor less energy is wasted. A few of the proposed uses of the wasted heat are water desalination, hydrogen production, or pyrolysis. Nuclear power plants most often provide baseload power and are very inflexible. One way to address this is to use nuclear hybrid energy systems. The goal of this research is to create a system that mimics the waste heat from a reactor, demonstrates how to utilize that heat, and shows that when energy demand is low the reactor does not need to reduce power; the energy can be directed elsewhere to create goods. We have developed an Energy Conversion Loop to act as a testbed for experimentation of the aforementioned processes and test the possibility of nuclear hybrid energy systems. The current design consists of a series of heat exchangers that transfer heat between hot air 427 °C (800 °F) and room temperature water. Each loop of the system mimics a type of process that can be tested with a waste heat application. Early models show the system is capable of producing air temperatures near 427 °C (800 °F) and steam temperatures of 154.4 °C (310 °F). These temperatures match needed process heat temperatures for pyrolysis, multi-effect distillation, and multi-stage flash distillation and can be used to simulate other processes for lab scale testing of wasted process heat. Physical testing will be completed in the future to confirm these results.

A higher number of research institutions work on solutions for energy storage systems. Therefore a large number of differing approaches in competition among each other to develop storage technologies. At the TU-Wien, Institute for Energy Systems and Thermodynamics a novel thermal energy storage concept based on an active fluidized bed technology — the so called sandTES-heat exchanger technology — has been developed. The present paper describes the basic idea behind the key technology and the design methodology of a test rig in semi-industrial scale. In addition the results of selected preliminary experimental and numerical investigations are presented and discussed.

Integration of non-dispatchable renewable energy sources such as wind and solar into the grid is challenging due to the stochastic nature of energy sources. Hence, electrical hubs (EH) and virtual power plants that combine non-dispatchable energy sources, energy storage and dispatchable energy sources such as internal combustion generators and micro gas turbines are getting popular. However, designing such energy systems considering the electricity demand of a neighborhood, curtailments for grid interactions and real time pricing (RTP) of the main utility grid (MUG) is a difficult exercise. Seasonal and hourly variation of electricity demand, potential for each non-dispatchable energy source and RTP of MUG needs to be considered when designing the energy system. Representation of dispatch strategy plays a major role in this process where simultaneous optimization of system design and dispatch strategy is required. This study presents a bi-level dispatch strategy based on reinforced learning for simultaneous optimization of system design and operation strategy of an EH. Artificial Neural Network (ANN) was combined with a finite state controller to obtain the operating state of the system. Pareto optimization is conducted considering, lifecycle cost and system autonomy to obtain optimum system design using evolutionary algorithm.

The central receiver power tower (CRPT) with a particle heating receiver (PHR) is a form of concentrating solar power (CSP) system with strong potential to achieve high efficiency at low cost and to readily incorporate cost-effective thermal energy storage (TES). In such a system, particulates are released into the PHR, and are heated to high temperature by concentrated solar radiation from the associated heliostat field. After being heated, the particles will then typically flow into the hot bin of the TES. Particulates accumulated in the hot bin can flow through a heat exchanger to energize a power generation system or be held in the hot TES storage bin for later use such as meeting a late afternoon peak demand or even overnight generation. Particles leaving the heat exchanger are held in the low temperature bin of the TES. A critical component in such a PHR system is the particle lift system, which must transport the particulate from the lower temperature TES bin back to the PHR. In our baseline 60 MW-thermal (MW-th) design, the particulate must be lifted around 70 m at the rate of 128 kg/s. For the eventual commercial scale system of a 460 MW-th design the particulate must be lifted around 138 m at the rate of 978 kg/s. The obvious demands on this subsystem require the selection and specification of a highly efficient, economical, and reliable lift design. After an apparently exhaustive search of feasible alternatives, the skip hoist was selected as the most suitable general design concept. While other designs have not been dismissed, our currently preferred somewhat more specific preliminary design employs a Kimberly Skip (KS) in a two-skip counterbalanced configuration. This design appears to be feasible to fabricate and integrate with existing technology at an acceptably low cost per MW-th and to promise high overall energy use efficiency, long service life, and low maintenance cost. A cost and performance model has been developed to allow optimization of our design and the results of that study are also presented. Our developed design meets the relevant criteria to promote cost effective CSP electricity production.

The importance of integrating renewable energy sources into standalone energy systems is highlighted in recent literature. Maintaining energy efficiency is challenging in designing such hybrid energy systems (HES) due to seasonal variation of renewable energy potential. This study evaluates the limitations in minimizing the losses in renewable energy generated mainly due to energy storage limitations and minimizing fuel consumption of the internal combustion generator (ICG). A standalone hybrid energy system with Solar PV (SPV), wind, battery bank and an ICG is modeled and optimized in this work. Levelized Energy Cost (LEC), Waste of Renewable Energy (WRE) and Fuel Consumption (FC) are taken as objective functions. Results highlight the importance of considering WRE as an objective function which increase the mix of energy sources that can help to increase the reliability of the system.

Thermal storage in an important operational aspect of a solar thermal system which enables it to deliver power or energy when there is no sunlight available. Current thermal storage systems in solar thermal systems work based on transferring the generated heat from sunlight to a thermal mass material in an insulated reservoir and then withdraw it during dark hours. Some common thermal mass materials are stone, concrete, water, pressurized steam, phase changing materials, and molten salts. In the current paper, a hybrid thermal energy storage system which is based on two metal hydrides is proposed for a solar thermal system. The two hydrides which are considered for this system are magnesium hydride and lanthanum nickel. Although metal hydride Energy Storage Systems (ESS) suffer from slow response time which restricts them as a practical option for frequency regulation, off peak shaving and power supply stabilization; they can still demonstrate significant flexibility and good energy capacity. These specifications make them good candidates for thermal energy storage which are applicable to any capacity of a solar thermal system just by changing the size of the ESS unit.

A methodology to investigate the generation, transport and storage of energy based on a multi-physics approach, tied to the end use application, is presented. Often little or no consideration is given to the end use or desired product of the energy used. Current energy generation, transport and storage are dominated heavily by a few large sectors, notably electricity and hydrocarbons. These are very effective and practical systems that facilitate the delivery of vast amounts of energy. It is then not surprising that most strategies for renewable energy generation and storage revolve around this centralized model in some way. In larger scale generation, power is usually fed onto the electrical grid with a current challenge being grid stabilization with increasing penetration of intermittent renewable resources. In small grid-independent system a mix of battery and hydrocarbon storage are often used to keep a micro-grid available for various end use applications. A paradigm shift in the thinking and design of energy systems based on the required end use or product is needed. The philosophy and motivation that lead to the consideration of this new approach are outlined in this article. Following this a summary of a methodical approach to developing the most energy and cost-effective solution to general processes by considering their end-use physics is presented. Examples of innovative energy generation, storage, and transport solutions based on the multi-physics approach are then outlined. Finally, a brief description of the Multi-physics Renewable Energy Lab (MPREL), a demonstration facility based on the approach and currently under construction at the Naval Postgraduate School, is given.

Anaerobic digestion (AD) involves the conversion of organic matter in the absence of oxygen to produce methane (CH 4 )-rich bio-gas that can be used for heating, vehicle fuel, or for generating electricity. The evolution of AD systems has historically followed two distinct paths: small residential-scale systems in the developing world to provide modest bio-gas resources for heating and cooking, and multi-million dollar facilities in the developed world for grid electricity production. However, there is a strong need to explore the possibility of applying AD technology in the medium-scale range (on the order of 100s of kW to 1 MW), which would be relevant to many farm installations and food processing plants that have significant organic waste resources. In this paper, technical and economic feasibility assessments have been conducted of two specific applications important to New York State: treatment of dairy farm resources in the Upstate region, and treatment of brewery and distillery waste in the New York City region where significant waste disposal barriers exist. In each case, a comprehensive analysis was first conducted of the available waste resources. Then, using data available in the open literature, an estimate of the total amount of renewable bio-gas that can be produced (bio-methane potential, BMP) was developed and used to compute the achievable size of a centralized AD system. For both the farm and brewery applications, it was determined that energy systems based on anaerobic digestion can be economically and environmentally viable, provided that ample organic resources are available, as well as incentives to offset the initial capital investment.

This paper presents a simulation of the thermal response of the off-grid zero emissions building at the Florida State University Energy and Sustainability Center in efforts to assess the development of effective thermal management strategies for the building. The paper describes the OGZEB and its energy systems and presents a thermal model to compute the temperature and humidity distribution using a volume element methodology. The energy characterization conducted in this paper will be used in future studies to develop control strategies and minimize energy consumption.

Residential and commercial buildings account for more than 40% of U.S. energy consumption, most of which is related to heating, ventilation and air conditioning (HVAC). Consequently, energy conservation is important to building owners and to the economy generally. In this paper we describe a process under development to continuously evaluate a building’s heating and cooling energy performance in near real-time with a procedure we call Continuous Monitoring, Modeling, and Evaluation (CMME). The concept of CMME is to model the expected operation of a building energy system with actual weather and internal load data and then compare modeled energy consumption with actual energy consumption. For this paper we modeled two buildings on the Georgia Institute of Technology campus. After creating our building models, internal lighting loads and equipment plug-loads were collected through electrical sub-metering, while the building occupancy load was recorded using doorway mounted people counters. We also collected on site weather and solar radiation data. All internal loads were input into the models and simulated with the actual weather data. We evaluated the building’s overall performance by comparing the modeled heating and cooling energy consumption with the building’s actual heating and cooling energy consumption. Our results demonstrated generally acceptable energy performance for both buildings; nevertheless, certain specific energy inefficiencies were discovered and corrective actions are being taken. This experience shows that CMME is a practical procedure for improving the performance of actual well performing buildings. With improved techniques, we believe the CMME procedure could be fully automated and notify building owners in real-time of sub-optimal building performance.

It is broadly accepted that current energy systems should become more sustainable in both a global and local context. However, setting common goals and shared objectives and determining the appropriate means by which to get there is the subject of heavy debate. Therefore, the American Society of Mechanical Engineers (ASME) and the German Association of Engineers (VDI) initiated a joint project aimed at providing a young engineers’ perspective to the global energy conversation. The young engineer project teams set a common goal of assembling a completely sustainable energy system for the U.S. and Germany by 2050. This includes not only the electricity market, but the overall energy system. Based on the current global energy paradigm, a completely sustainable energy system seems very ambitious. However, multiple analyses show that this path is possible and would in the medium to long run not only be desirable, but also competitive in the market. This future ‘energy puzzle’ consists of many important pieces, and the overall picture must be shaped by an overarching strategy of sustainability. Besides the many detailed pieces, four main critical issues must be addressed by engineers, politicians and everybody else alike. These challenges are: i) Rational use of energy: This uncomfortable topic is rather unappealing to communicate, but is a key issue to reduce energy demand and to meet the potentials of renewable energy carriers. ii) Balancing of electricity demand and generation: This is a challenge to the electricity markets and infrastructures that are currently designed for base-load, mainly fossil power plants. The overall mix of renewable energy generation, storage technologies, grid infrastructure, and power electronics will decide how efficient and reliable a future energy system will be. iii) Cost efficiency and competitiveness: It is a prerequisite for industrialized countries to stay competitive and to establish RE in the market. Developing economic technologies while at the same time establishing a strong RE market is the secret of success. iv) Acceptance of the system and its consequences: The best energy strategy cannot be realized without broad public acceptance for it. Therefore, the understanding of the energy technologies and an objective discussion must be promoted — without old fashioned emotionalizing of certain risks. The paper will present details on the four mentioned aspects, compare the situations between the U.S. and Germany, and propose solutions for appropriate political frame conditions to achieve a sustainable energy system.

In the present paper, the possibility of using thermoelectric power generator modules (TEGs) to convert the heat generated by the photovoltaic/thermal (PVT) collector into electricity is investigated. A comprehensive heat transfer model for the combined PVT-TEG system is developed via MATLAB and simulated under different conditions. The hot side of the TEG module is considered connected to the top of the air channel which is attached to the backside of the solar panel and the cold side is cooled down by air flow through the air channel under the PV panel. The TEG modules convert the temperature gradient to electricity and generates extra power from the excess heat which results in higher total efficiency. The effect of using combined PVT-TEG on total generated power under different levels of irradiation is presented and discussed.

In the last twenty years, the exploitation of non-renewable resources and the effects of their applications on environment and human health were considered central topics in political and scientific debate on European and worldwide scale. This kind of resources have been used in different sectors, as energy systems, technological research, but also in private/public buildings and production of consumer goods, involving significantly domestic and ordinary life of every human being. Studies about the effect of this exploitation carried out discouraging results, in terms of climate changes and energy sustenance; this determined a progressive approach process to a new concept of development, able to couple the qualitative standard of modern life with the respect of planet and its inhabitants. Starting from this reflection, scientific community moved towards research on alternative resources and developed a new way to conceive planning process and technical innovations, in order to exploit renewable energies and recycled materials, promote energy savings and reduce environmental pollution. In this context the present paper aims at evaluating benefits relating to different solutions of thermal insulation in building envelope. In fact a high grade of insulation ensures better comfort conditions in inner spaces, reducing energy consumptions due to heating and cooling conditioning. The paper presents the results of a detailed Life Cycle Assessment (LCA) of the reflective foil ISOLIVING, conceived and produced by an Italian company. The Life Cycle Assessment methodology allows to consider all stages of the life cycle, from the extraction of raw materials to the product’s disposal, in an optics “from cradle to grave.” In particular, the study takes into account the production phase of the reflective foil ISOLIVING, the installation phase, the transport of all components to the production site and also the end of life scenario of the material. The possibility to collect many detailed information about the production phase adds value to the study. The analysis is carried out according to UNI EN ISO 14040 and UNI EN ISO 14044, which regulate the LCA procedure. The LCA modeling was performed using SimaPro software application. The results of the analysis allow to make an important comparison concerning the environmental performances, between the reflective foil ISOLIVING and other types of insulating materials.

Maui Island in the State of Hawaii faces land use and freshwater allocation challenges associated with a growing population and a changing economic base as plantation agriculture has declined. Debate about whether water should be restored to environmental flows, allocated to new urban development for residents and tourists, or be used to irrigate food or fuel crops has highlighted Maui’s opportunity to make integrated resource decisions that consider land, water, and energy in particular. One major potential water demand on Maui is for irrigation for biofuels crops, such as sugarcane for ethanol. While Maui’s energy system is currently low in water intensity, using irrigated biofuels could increase the need for local water investment in energy systems. This paper aims to characterize surface water supply on Maui in order to draw conclusions about supply adequacy for biofuel irrigation. Narrow-scope empirical equations linking streamflow and precipitation tend to produce more accurate estimates for individual streams: for example, equations based only on northeast Maui streams tend to predict northeast Maui stream flows better than equations based on all of Maui’s streams. However, specific equations do not exist for most regions of Maui. This paper finds that general and specific empirical equations for northeast Maui predict nearly identical aggregate streamflows. Irrigation ditch flow comprises aggregate streamflow from a given region, so it is likely that existing, general equations can predict irrigation ditch flows with acceptable accuracy.