Software Tools Supporting Village Power System Design

Jean Ku

APEC Village Power WorkshopNovember 9, 2004

Why do we need new models?

• Traditional Rural Electrification– Grid extensions, micro-hydro or diesels

• New and Renewable Alternatives– Small-scale individual DC systems

• Solar Lanterns, Solar or Wind Home Systems

– Hybrid Power AC Systems• Wind, PV, Biomass, Gensets, Batteries• Mini-grids, Micro-enterprise Zones, Battery Recharging

Stations

The Role of Models• Objective and subjective criteria

– Computers analyze objective criteria– People analyze subjective criteria

• Offers simplicity and transparency

• It’s easier to weigh the quality of service issues when you have comparable cost estimates for each alternative

The Modeling Process

What is the most economical way to meet a community’s power needs?

Data InputsLocal energy resources

Community loadsBasic component costs

General maintenance costs

Modeling Tools

Power System Design

HOMER, Hybrid2

ResultsBasic system design

Installation and O&M costsBase line cost of alternatives

Yearly power productionFuel consumption

Modeling Tools

Distribution system configuration (on- vs.

off-grid)

ViPOR

NREL’s Suite of Models

• ViPOR: An optimization model that determines the best mix of centralized and isolated power generation for a particular village.

• HOMER: An optimization model that determines the least-cost system configuration.

• Hybrid2: A simulation model to determine the cost and performance of a wide variety of power systems given the load and available resources.

Village Power Optimization Model for Renewables

• Optimize the mix of centralized and isolated generation

• Select between grid extension and stand-alone systems for centralized power

• Select the optimal placement of the centralized power system(s)• Determine the optimal placement of transformers• Design the optimal MV and LV distribution grid

An optimization model to design village electrification systems, ViPOR will:

ViPOR’s optimization procedure considers costs and revenues.

ViPOR: Inputs

• Location & energy requirements for expected loads• Potential locations of centralized power system(s)• Wire and transformer costs• Power generation costs for isolated and centralized

power systems (can be calculated by HOMER)• Expected revenues from each load (on-grid and off-

grid)• Terrain description (spatial map)• Maximum low voltage line length

ViPOR: Sample village

• Water is shown in blue, forest green, grass white, and trail gray. • Green dots are houses, brown are stores, orange is church.• Yellow triangles are high-wind sites, orange is low-wind site.

ViPOR: Solution for sample village

• ViPOR has chosen a high-wind site to power the centralized system• Houses not on the grid are to be given PV home systems• Red lines are MV wires, blue are LV wires• Red dots are transformers

ViPOR: Numeric Output

ViPOR: Numeric Output

ViPOR: Future enhancements

• Explicit calculation of voltage drops• Calculation of power losses in

distribution system• Multiple transformer sizes• Multiple wire sizes• Tighter integration with GIS and

HOMER

What is HOMER?

• A tool for comparing and evaluating micropower technology options for a wide range of applications– Village power systems– Stand-alone applications– Grid-connected systems– Conventional technologies– New technologies

What does HOMER do?

• HOMER finds the combination of components that can serve a load at the lowest life-cycle cost

• Shows how this result can vary given different assumptions

Technologies HOMER Can Model

• Single technology systems and multiple-technology (hybrid) systems

• Compare multiple combinations of different technologies

Generators• Fossil fuels

• Biofuels

• Cofired

• Cogeneration

• Up to three generators

Grid Extension• Compare to stand-alone

system• Breakeven grid extension

distance

Grid-connected Systems

• Rate schedule

• Net metering

• Demand charges

Renewable Technologies• Solar PV

• Wind

• Biomass and biofuels

• Hydro

Emerging Technologies• Fuel cells

• Microturbines

• Small modular biomass

Questions HOMER can Answer

– Should I buy a wind turbine, PV array, or both?

– Will my design meet growing demand?– How big should my battery bank be?– What if the fuel price changes?– How should I operate my system?– And many others…

Inputs

• Component cost and performance data

• Resource availability

• Loads

Simulation - Optimization - Sensitivity Analysis

• Simulation– Estimate the cost and determine the feasibility

of a system design over the 8760 hours in a year

• Optimization– Simulate each system configuration and

display list of systems sorted by net present cost (NPC)

• Sensitivity Analysis– Perform an optimization for each sensitivity

variable

[Energy Balance]

Simulation

Optimization

Sensitivity Analysis

Sensitivity Analysis

• Important information is very uncertain– Loads

• Even if you have data loads will change with system

– Resources• Data for a different place, natural variability

– Costs• Fuel prices, O&M costs

• Policy and market analyses requires input ranges not point estimates

Simulation Results

• Cost and performance of a particular system configuration

Optimization Results

• Ranked list of system configurations

Sensitivity Results

• Graphs and tables

The Hybrid2 Simulation SoftwareA tool designed to accurately predict the long

term performance of a wide variety of power

systems made up of conventional fuel generators, wind generators, photovoltaics and energy storage through batteries

Hybrid2 Data Requirements

• Loads– Primary time series or daily load profile, including deferrable and

optional loads

• Site/Resource parameters– Wind speed and incident solar time series– Ambient temperature time series or nominal value– Elevation, site position and wind turbulence parameters

• Power System– Configuration and components– Component performance parameters (Library)– Dispatch Strategy (Library)

Hybrid2 Analysis Procedures

Power SystemConfiguration and components

Component performance parameters (Library)Dispatch Strategy (Library)

Site/Resource parametersWind and solar time seriesAmbient temperature data

Elevation, site position and wind turbulence parameters

LoadsPrimary time series or

daily load profile

Performance ResultsSystem design

DetailedModeling

Economic ResultsCapital costO&M cost

Hybrid2 Software Features• Probabilistic/time series model: Accounts for the

fluctuations of the wind and load during each time step • Very diverse system architecture

– AC, DC and combined systems can be modeled– System can include multiple wind turbines, multiple

diesels, batteries, PV and 4 different types of power converters

• Detailed economic analysis• On line library of manufactures equipment• Detailed dispatching options: 17 different control

parameters• Hybrid systems glossary of commonly used terms • Energy audit/estimation tool• Resource data gap filler

Hybrid2 Power System Design

The power system is designed to meet the required loads using the resources available. This requires a fair amount of hybrid system and design experience.

Hybrid2 Results Interface

Simulation results displayed in a graphical format as well as a summary file which includes power flows from each component, loads, and system losses.

HOMER and Hybrid2• Design philosophy: Simplicity vs. flexibility• Use: Optimization vs. performance

predictions• System configuration:

– HOMER output, Hybrid2 input

• Main differencesHybrid2 HOMER- Intra-hour variability - Easy initial use- Bus voltages - Dispatch optimization- Dispatch flexibility - All DG technologies- Engineering tool - Options analysis

These are only models!

• ViPOR, HOMER, and Hybrid2 do not provide "the right answer" to questions. It does help you consider important factors, and evaluate and compare options.

Model Availability

• ViPOR: Available from www.nrel.gov/vipor.• HOMER: Available from www.nrel.gov/homer.

Inquiries, email peter_lilienthal@nrel.gov.• Hybrid2: Send e-mail to Hybrid2@nrel.gov.

Provided with software, manuals and user support.

These models were developed with funding from the US Department of Energy and the

National Renewable Energy Laboratory