HOMER

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Logo: HOMER Energy Modeling Software
HOMER is used for designing and analyzing hybrid power systems, which contain a mix of conventional generators, cogeneration, wind turbines, solar photovoltaics, hydropower, batteries, fuel cells, hydropower, biomass and other inputs.



 



Overview

The HOMER Hybrid Optimization Modeling Software is used for designing and analyzing hybrid power systems, which contain a mix of conventional generators, cogeneration, wind turbines, solar photovoltaics, hydropower, batteries, fuel cells, hydropower, biomass and other inputs. The tool can analyze either grid tied or standalone systems and can also perform greenhouse gas calculations for the measures being considered. HOMER allows the user to input an hourly power consumption profile and match renewable energy generation to the required load. This is allows a user to analyze micro-grid potential, peak renewables penetration, ratio of renewable sources to total energy, and grid stability, particularly for medium to large scale projects. Additionally, HOMER contains a powerful optimizing function that is useful in determining the cost of various energy project scenarios. This functionality allows for minimization of cost and optimization of scenarios based on various factors (e.g., CO2 minimization).

To meet the renewable energy industry’s system analysis and optimization needs, NREL started developing HOMER in 1993. Since then it has been downloaded free of charge by more than 30,000 individuals, corporations, NGOs, government agencies, and universities worldwide.

About

HOMER is a computer model that simplifies the task of evaluating design options for both off-grid and grid-connected power systems for remote, stand-alone, and distributed generation (DG) applications. HOMER's optimization and sensitivity analysis algorithms allow the user to evaluate the economic and technical feasibility of a large number of technology options and to account for uncertainty in technology costs, energy resource availability, and other variables. HOMER models both conventional and renewable energy technologies:

  • Power sources
    • solar photovoltaic (PV)
    • wind turbine
    • run-of-river hydro power
    • generator: diesel, gasoline, biogas, alternative and custom fuels, cofired
    • electric utility grid
    • microturbine
    • fuel cell
  • Storage
    • battery bank
    • hydrogen
    • flow batteries
    • flywheels
  • Loads
    • daily profiles with seasonal variation
    • deferrable (water pumping, refrigeration)
    • thermal (space heating, crop drying)
    • efficiency measures
Licensing

In 2009 NREL granted a license to distribute and enhance HOMER to HOMER Energy. HOMER Energy provides a highly visible commercial outlet for NREL's renewable energy simulation tools, with the goal of enhancing the use of HOMER by industry and decision makers. HOMER Energy will distribute HOMER worldwide through its affiliates and will provide customization, training, and technical support for its global user base.

NREL retains ownership of the licensed software, and retains the right to use HOMER on government projects. In addition, users will always be able to download version 2.68 Beta free of charge from HOMER Energy. [1]

Worldwide HOMER User Data

Inputs and Outputs

Below are descriptions of the inputs and outputs for the tool.

Inputs include:

The user must input load data (primary, deferable, thermal, or hydrogen). Hourly load (kW) data is required and the user can enter day-to-day and time-step-to-time-step variability, scaled annual average (kWh/day), or an efficiency multiplier.

The user must select the system components to be analyzed, and data is required for each component.
For PV (as an example), the following data is input [remainder of section]:

  • Size (kW)
  • Capital cost ($)
  • Replacement cost ($)
  • O&M ($/yr)
  • Sizes to consider (kW)

The user can use default values or can input data for:

  • Output current (AC or DC)
  • Lifetime (years)
  • Derating factor (%)
  • Slope (degrees)
  • Azimuth (degrees W of S)
  • Ground reflectance (%)

The user can specify whether the system is tracking (horizontal, vertical, or two axis tracking with monthly, daily, or continuous adjustment) or not tracking, and whether the analysis should consider the effect of temperature (the effects can be defined or default values can be used).

For inverters, the user must input:

  • Size (kW)
  • Capital cost ($)
  • Replacement cost ($)
  • O&M ($/yr)
  • Sizes to consider (kW)

The user can use default values or can input data for:

  • Lifetime (years)
  • Efficiency (%)

and the user can select whether or not the inverter can operate simultaneously with an AC generator.

For batteries, the user must select a battery type from a library of batteries, or input a new battery. The user must input:

  • Quantity
  • Capital cost ($)
  • Replacement cost ($)
  • O&M ($/yr)
  • Sizes to consider (kW).

The user can use default values or can input data for:

  • Batteries per string
  • Minimum battery life.

If the user wishes to analyze other components, such as generators or other renewable technologies, additional inputs would be necessary.

The user must define or input resource data for all components and loads being considered. For PV the user can enter latitude and longitude of a location and import a time series data file from the internet, or the user can enter monthly average resource data (in kWh/m2/day). The user can scale the annual average data if desired.

The user can use default economic data or input values for:

  • Annual real interest rate (%)
  • Project lifetime (years)
  • System fixed capital cost ($)
  • System fixed O&M cost ($/year)
  • Capacity shortage penalty ($/kWh)

The user can define a variety of system controls, including the simulation time step (in minutes) and other considerations for generators, thermal loads, and wind turbines which are not directly applicable to PV. The user can define emissions inputs for emissions penalities and limits on emissions (carbon dioxide, carbon monoxide, unburned hydrocarbons, particulate matter, sulfure dioxide, and nitrogen oxides).

Outputs include:

HOMER outputs all technically feasible component combinations in order of increasing net present cost. For each system of components a variety of outputs are available, including:

  • A cost summary including
    • Capital
    • Replacement
    • O&M
    • Fuel
    • Salvage
    • Total displayed by annualized or net present costs and categorized by component or by cost type
  • Cash flow
    • Nominal or discounted and displayed by totals, component, or cost type
  • Electrical output data for PV
    • Grid purchases (if system is grid-tied)
    • AC primary load
    • Excess electricity
    • Unmet electric load
    • Capacity shortage
    • Renewable fraction
  • For the inverter data is output about:
    • Capacity
    • Mean, minimum and maximum output
    • Capacity factor
    • Hours of operation
    • Energy in and out
    • Losses
  • For the electrical grid, if the system is grid-tied, HOMER outputs:
    • Monthly energy purchased (kWh)
    • Energy sold (kWh)
    • Net purchases (kWh)
    • Peak demand (kW)
    • Energy charge ($)
    • Demand charge ($)

HOMER outputs the emissions (kg/year) for the entire system.
HOMER is also able to output and display a variety of hourly and monthly data as well as DMap, energy profile, probability density function (PDF), cumulative distribution frequency (CDF) and load duration curves (DC).

Highlights

HOMER is a valuable hourly simulation tool for analyzing a variety of system components, including: PV, wind, hydro, biomass, generators, electric utiltiy, microturbine, fuel cell, flywheel, battery, flow battery, and hydrogen. Although an hourly simulation model, it has flexibility and can be used with average annual data or with more detailed, 15-minute load or resource data. HOMER's optimization functionality makes it a very helpful tool for comparing project implementation scenarios.

Users of HOMER typically have mid to high level knowledge of RE technologies. The tool requires many data inputs (costs and sizes of technologies, efficiency, resource availability, etc) and so a user with no knowledge of RE or with no idea of where to get this data will have a hard time utilizing this tool fully.

Resources

References

  1. 1.0 1.1  "HOMER NREL website"