1. Software Tools Supporting Village Power System Design
Jean Ku
APEC Village Power Workshop
November 9, 2004

2. 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

3. 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

4. The Modeling Process
What is the most economical way to meet a community’s power needs?
Data Inputs
Local energy resources
Community loads
Basic component costs
General maintenance costs
Modeling Tools
Distribution system configuration (on- vs. off-grid)
ViPOR
Results
Basic system design
Installation and O&M costs
Base line cost of alternatives
Yearly power production
Fuel consumption
Modeling Tools
Power System Design
HOMER, Hybrid2

5. 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.

6. Village Power Optimization Model for Renewables
An optimization model to design village electrification systems, ViPOR will:
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
ViPOR’s optimization procedure considers costs and revenues.

7. 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

8. 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.

9. 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

10. ViPOR: Numeric Output

11. ViPOR: Numeric Output

12. 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

13. 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

15. 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

16. Technologies HOMER Can Model
Single technology systems and multiple-technology (hybrid) systems
Compare multiple combinations of different technologies

17. Generators Fossil fuels Biofuels Cofired Cogeneration
Up to three generators

18. Grid Extension Compare to stand-alone system
Breakeven grid extension distance

19. Grid-connected Systems
Rate schedule
Net metering
Demand charges

20. Renewable Technologies
Solar PV
Wind
Biomass and biofuels
Hydro

21. Emerging Technologies
Fuel cells
Microturbines
Small modular biomass

22. 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…

23. Inputs
Component cost and performance data
Resource availability
Loads

24. Simulation - Optimization - Sensitivity Analysis
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

25. 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

26. Simulation Results
Cost and performance of a particular system configuration

27. Optimization Results
Ranked list of system configurations

28. Sensitivity Results
Graphs and tables

29. The Hybrid2 Simulation Software
A 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

30. 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)

31. Hybrid2 Analysis Procedures
Site/Resource parameters
Wind and solar time series
Ambient temperature data
Elevation, site position and wind turbulence parameters
Loads
Primary time series or daily load profile
Power System
Configuration and components
Component performance parameters (Library)
Dispatch Strategy (Library)
Performance Results
System design
Economic Results
Capital cost
O&M cost
Detailed
Modeling

32. 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

33. 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.

34. 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.

35. HOMER and Hybrid2 Main differences
Design philosophy: Simplicity vs. flexibility
Use: Optimization vs. performance predictions
System configuration:
HOMER output, Hybrid2 input
Main differences
Hybrid2 HOMER
- Intra-hour variability - Easy initial use
Bus voltages - Dispatch optimization
Dispatch flexibility - All DG technologies
- Engineering tool - Options analysis

36. 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.

37. Model Availability ViPOR: Available from www.nrel.gov/vipor.
HOMER: Available from Inquiries,
Hybrid2: Send to 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