Journal of Energy Engineering

Efficient use of a large quantity of low-grade energy that is available in the earth surrounding a typical residential structure can be realized by designing a HVAC system directly integrating the ground source with a dynamic building envelope. A continuous air duct constructed within the dynamic envelope is configured such that preconditioned air in the basement can be circulated between the shells of the wall. The result is that a large portion of the heat loss through the wall is the geosolar heat extracted from the ground, reducing the load of the home heating system. Air in the ventilation system may also be passed through the heat reservoir such that make-up air is prewarmed and cleaned before entering the interior. This geothermal component of the heating system is further enhanced by increasing the ambient temperature of the earth with unwanted heat absorbed by the roof of the structure during the summer months. The roof of the structure is fitted with narrowly spaced runs of cross-linked polyethylene (PEX) pipe just below the roof surface. Water circulating between these coils and the ground serve to transfer summer heat into the ground while cooling the building. A horizontal blanket of insulation around the perimeter of the building allows heat removed from the roof to be retained for winter use. In addition, cool air from the ground can also be circulated through the dynamic walls during the summer to keep the structure cool. An extensive study involving this integrated building system has been carried out for the last 3 years, and observations of system performance are reported in this paper.

Small-scale model houses were built with different masonry products in order to investigate the environmental performance of sustainable construction materials. Three model houses were designed and developed as per the standards one with recycled paper mill waste (RPMW)-cement bricks, another with fly ash bricks and the third with ferrocement wall panels. In order to assess the indoor temperature for these particular sustainable building materials, the temperature inside the model houses was monitored over the study location for the period of a year. The economic viability for the developed model houses was also analyzed. Wall surface temperature readings on the exposed south facade were used to estimate thermal conduction of the wall assembly. Detailed analysis revealed that the developed RPMW-cement brick model house was more thermally resistant and economical than the fly ash brick and ferrocement wall panel model houses. Energy efficient building minimizes energy consumption through the reduction of indoor temperature, making the RPMW-cement brick model house the best choice for construction.

The electrical performance of a photovoltaic system is influenced by the spatial layout of its components. As a result, designers must understand how to identify layouts that maximize power performance and best utilize land area. In response, this paper presents power performance analyses for a range of typical layout strategies, direct current (DC) power block sizes, and other related engineering considerations for large-scale photovoltaic systems. The results of this study suggest layout strategies that produce squarer DC power block footprint areas and/or that minimizing DC wiring lengths maximize the power output of the photovoltaic system. Additionally, these strategies are likely to minimize construction costs and cost-to-performance ratios. Ultimately, this paper is meant to further communicate the influence of layout on system performance and convey related trends to guide layout optimization explorations within large-scale photovoltaic construction projects.

The system dynamics approach is an object-oriented simulation method based on feedback loops, flow diagrams, and flow and state variables, which can be used in the development of a water system’s operational policies and water-resource management. In reservoir operation simulations, there are iterative procedures (feedback loops) due to the dependency of reservoir release on both initial and final reservoir storage. System dynamics can successfully satisfy this need. Given the complex implicit and nonlinear relationships that exist in hydropower reservoirs, the system dynamics approach can be efficient in the planning and management of those reservoirs. This paper develops a system-dynamics simulation model using Vensim for the operation of a hydropower reservoir system (Khersan 1, Karoon 4, and Karoon 3) that is located in series and in parallel in the Karoon river basin, Iran. Steps of the model design include definition of decision variables, formulation of model, and method of solution to compute the output of the hydropower reservoirs. To assess the effects of the reservoirs on each other and the importance of each reservoir, operational scenarios are considered. Reservoir performance criteria (reliability, resiliency, and vulnerability) and mean energy production over a 44-year simulation period are calculated for each operational scenario. The results show that addition of the Khersan 1 reservoir to the system composed of Karoon 4 and Karoon 3 reservoirs increases the average amount of energy production by 20% without a significant loss in performance criteria. The sensitivity analysis for Khersan 1 is conducted in two states. The amounts of installed capacity of the power plant and maximum storage volume of the reservoir are increased by 20% and decreased by 20%, respectively. The results show that, in terms of energy production, the effect of increasing the installed power-plant capacity of Khersan 1 is greater than that of increasing the maximum reservoir storage volume of this reservoir. Therefore, by considering the same percentage increase (20%) in both installed capacity and maximum storage volume, it is preferable to increase the installed capacity of the power plant at Khersan 1 reservoir.

This research focuses on the supply chain network design of a fast pyrolysis and hydroprocessing production pathway by utilizing corn stover as feedstock to produce gasoline and diesel fuel. A mixed integer linear programming (MILP) model was formulated to optimize fast pyrolysis and hydroprocessing facility locations and capacities to minimize total system cost, including the feedstock collecting costs, capital costs of facilities, and transportation costs. The economic feasibility of building a new biorefinery in Iowa was analyzed based on the optimal supply chain configuration and savings in bio-oil logistic costs to the centralized upgrading facility.

In this paper, the main aim is to optimize the heliostat layout in central receiver solar power plants in order to achieve the maximum heliostat field efficiency using a genetic algorithm as an optimization tool. First, an algorithm is developed based on vector geometry in order to select an individual heliostat and then calculate its characteristic angles at any time and location. The process of the program will be applied to track the Sun as a control function. The best configuration is obtained by considering the radial staggered layout of the heliostat field. The locations of the heliostats are determined, and the efficiency of each heliostat is calculated to find the most appropriate condition with the highest efficiency. Calculating the power of each heliostat supplied on the receiver will make it possible to determine the absorbed total heat power. At this stage, the genetic algorithm is applied to find the best heliostat layout to obtain the maximum efficiency of the field for a specific absorbed power supplied on the receiver. The results show that by changing the design parameters, i.e., increasing the tower height and decreasing the heliostat height by 7.7 and 19.5%, respectively, the total efficiency of the field is increased by almost 4% and the total area of heliostats is decreased by 17%. In other words, a more efficient heliostat layout can be achieved by choosing new design parameters.

This work investigates the feasibility of a renewable energy sources (RES)-based stand-alone power system for electricity supply, to several simulated buildings, where energy is stored in a flywheel energy storage system (FESS). The system is assumed to be located on Naxos Island, Greece, due to the island’s high wind and solar potential and was designed to cover both the load of a typical house and a country house, where the excess electricity could be sold to the grid. An innovative storage device type, consisting of flywheels and electrochemical batteries, was selected as the energy buffer. The energy produced by hydrogen used in the proton electrolyte membrane (PEM) fuel cell (FC) charges the flywheel. This apparatus is compared to diesel generators commonly used in stationary applications. Optimization of the system, in terms of energy efficiency and economic feasibility, is also considered. The two systems were simulated using sensitivity, optimization, and simulation modeling software, and custom calculations of both energy and finance were carried out. It was found that a one-way grid connected project using state-of-the-art and totally green technologies, including hydrogen-fed PEM-FC and flywheels, can totally cover the electrical demands of a typical house and country house, obtaining cost per consumed energy as low as 1.374 and $0.097\$/\mathrm{KWh}$, respectively. These results actually indicate that hydrogen technology could be a reliable energy alternative in the near future.

This paper presents a method for estimating the fixed and variable speed turbine performance index. The approach is based on Weibull wind probability distribution function and manufacturer-provided power curve. It is further shown that the existing turbine performance index formulation is only valid in case of variable speed turbines. A general approach to calculating the turbine performance index is derived, suitable for both fixed and variable speed wind turbines. Instead of choosing a particular model for approximating the power curve, commonly used polynomial fitting is employed. It is suggested to determine the best site for a given off-the-shelf turbine rather than finding the best theoretical turbine for a given site.