UW-HYBRID  

PV/Wind/Diesel Hybrid Simulator

Overview

 

UW-HYBRID is a quasi-steady performance simulation tool. It calculates energy production and flows per timestep; totals are obtained by Euler integration over time. TRNSYS is an ideal software environment for the modeling of hybrid systems composed of various interconnected devices because TRNSYS itself is composed of linked modules. These modules are:

A detailed multiple-unit wind turbine performance simulator with selectable hardware,

A detailed diesel engine performance and fuel consumption model with selectable hardware,

A detailed PV module array system and peak power tracker performance model with selectable hardware,

A general diesel engine dispatch controller employing cost optimization algorithms,

Selectable time series weather data,

Selectable time series loads data, and

Various output formats, diagnostic calculations, summaries and measures of performance.

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UW-HYBRID 1.0 includes a wind turbine performance model which accurately calculates the performance of a real wind turbine, based on data read in from a power curve file. Up to five different types of turbines can be included in the current version. The model includes the effects of elevation wind shear and time varying temperature and wind speed to calculate the appropriate performance of the wind turbine over time. Cumulative loss factors can be incorporated as well. The diesel engine performance model determines fuel output, fuel cost, power ou\ tput, engine hours and waste heat delivered over time as a function of controller setpoints. These calculations are made subsequent to reading in power output and fuel consumption performance specifications from files describing actual diesel systems. The PV performance model simulates the performance of a PV system at a user-specified array slope azimuth and module type. The calculations are based on data obtained from actual time series weather files for the location. The calculations of system performance utilize the methodologies developed at the Solar Energy Laboratory for calculating radiation on the tilted surface and net electrical power resulting from the system. A peak power tracker is included. The diesel engine dispatch controller can accept up to five generators in any sequence or configuration. The controller determines the net load to be provided by the diesels, by subtracting renewables output from the demand. The controller programs itself by reading the performance specification data used by the diesels to describe their operational characteristics. Subsequently, the controller determines the least-cost ranking of the units, and dispatches the diesels in a sequence which satisfy the criteria of minimum cost to meet load. The controller also determines the amount of dump energy per timestep. This occurs because the diesels cannot operate at less than their minimum load, typically 40%.

 

Description of the TRNSED Implementation

 

UW-HYBRID 1.0 provides a configurable user-interface, running under TRNSED. The user can specify the start, timestep, and length of the simulation period, as well as the load and weather profiles. Time steps of .1 hour to one hour are permitted. Pop-up menus are provided. The user selects the PV array tilt, azimuth and manufacturer. If desired, the user can elect to have no PV wind or diesel units simulated, in order to allow simulations of a wide variety of systems. The software permits the selection of identical diesels generators, if desired. A fuel cost is entered, per liter. Finally, the wind characteristics are entered by the user. The site elevation and data height are entered in. For each turbine, the hub height and local wind shear are entered. Similar to the diesels, zero to five units as well as similar units are acceptable.

 

 

Outputs

 

After selecting "Calculate" from the TRNSED main menu item, UW-HYBRID presents an on-screen plot as the simulation progresses. The plot shows the individual power output of each diesels, as well as the addition of PV power and wind turbine power to meet demand. Whenever demand is sufficiently met by the renewables, it can be seen that diesels are taken off line, in order of greatest to least cost. The lower plot shows the cumulative demand, as well as the output of the wind systems, cumulative diesels and PV. Also shown is the amount of dump energy and energy deficit. Energy deficit is defined as the amount of unserved demand during the simulation. In addition to the on screen output, UW-HYBRID creates disk files of a number of parameters. Most can be plotted, without quitting UW-HYBRID, using the plot menu in TRNSED. Others, including histograms of data and time series outputs, are stored as text for viewing by other applications.