Isolated Diesel Grids – Renewable Integration Marc Mueller-Stoffels, PhD

Hybrid-Diesel Power Generation Diesel-only cost: between 0.35 and 1+ $/kWh Wind in rural AK Average $10,700/kW Large, commercial wind farms: < $3000/kW PV in rural AK We don’t really know the cost yet Target: $5000/kW – makes it commercially viable in many places avoided fuel cost) Note Diesel generators: (relatively) low initial investment, but then… RE sources: high initial investment, but then…

Customer Requirements Rural AK sees large variability in demand Mostly high winter loads But, in some places, industry drives high summer demand Power has to be of decent quality Outages are always unacceptable Especially at 50 below

Diesel Powerhouse Generally: Provides prime power (forms the grid, i.e., one diesel is always on) Provides electricity AND heat Diesels have sweet spot, outside this, efficiency suffers Usually pretty well ‘dialed-in’ 100+ years of operation Cost break-down Fuel cost Cost of operation Investment

Integration of RE – Basic Rules Operational envelope of diesel generators Never under-load diesels (20 to 40%) Do not risk overload (>110%) [keep spinning reserve] Sudden large load swings should be avoided Without control of RE resource Only small amounts of RE power can be allowed Example: distributed PV can quickly become detrimental

Hybrid-Grid Control: Source Management Curtail RE source to remain in operational envelope Spinning reserve: Largest sudden load rise, or amount of RE on grid, which ever is bigger

Hybrid-Grid Control: Load Management Loads that are controlled by the utility do not require spinning reserve Examples: Pumps, electric heaters, cooling equipment Allows operation with less or smaller diesel generators Maximizes RE power use

Diesel-off -- Game Changer? Affordable Energy Storage < 0.10 $/kWh Need to replace diesel by power-electronics as prime mover Diesel-off mode Additional 30% fuel savings Reduced O&M cost Permanent diesel-off – cheaper diesel packages

And the value of RE power? Displaced Fuel Not a linear function, but direct savings Reduced O&M on diesels ‘Small’ maintenance can be scheduled based on gallons of fuel used Hedging Volatile fossil fuel prices are a direct risk RE power can hedge against variation (usually fixed cost)

Why? Model development Model validation Model verification Performance Assessment Control Strategy Development 15

Questions? Marc Mueller-Stoffels, PhD Research Assistant Professor Alaska Center for Energy and Power University of Alaska Fairbanks