HOMER
Introduction Assist in the design of micropower systems Facilitate the comparison of power generation technologies. Models a power system’s physical behavior and it’s life cycle cost (total cost of installing and operating the system over its life span). Compare different design options based on their technical & economic merits, including input uncertainties.
Why use HOMER? To overcome uncertainties: Design options Key parameters: Load size & fuel price Power output: Intermittent, seasonal. Availability of renewable resources
3 Principle tasks Simulation: Models the system & determine technical feasibility & life cycle cost. Optimization: Determines the best possible system configuration. Sensitivity analysis: Performs multiple optimizations with different input assumptions to gauge the effect of uncertainties.
NPC Total Net Present Cost Represent life-cycle cost. Includes all costs and revenues within the project lifetime, with future cash flow discounted to the present. Includes initial capital cost of components, cost of replacement, maintenance & fuel, & cost of purchasing power from the grid. The optimal configuration is the one that satisfies the user-specified constraints at the lowest NPC.
How to determine Optimal? The overall optimization results tends to show many system configurations whose NPC is slightly higher than that of the optimal configurations. The modeler may decide that one of those suboptimal configurations is preferable in some way to the configuration that HOMER represents as optimal.
Physical Modeling How HOMER models the physical operations of the system? Loads Resources Components
Generators Can be scheduled to force it ON or OFF at certain times. If it is not scheduled, HOMER decides whether it should operate based on the needs of the system & the relative costs of the other power sources.
Battery Bank Nominal voltage Capacity curve Lifetime curve Minimum state of charge Round trip efficiency
Dispatch Strategies How the battery is charged. 2 types of strategies: Load-following Renewable energy charges the battery, generator does not. Battery is only charged by surplus electricity. Cycle charging Whenever generator operates, extra electricity is produced to charge the battery while serving the load.
Operating Reserve = Operating capacity – Electrical load Provides safety margin ensures reliable electricity supply despite variability in electric load & renewable power supply. Very important for standalone system. Outage!!! Grid-connected system? Don’t worry, be happy! Applies to system with large battery banks.
Q & A