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Energy Integration Briefing

  • Integration2
  • Integration1
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Integration refers to the changes made to a microgrid in order to incorporate a new energy source, not including transmission or distribution. The goal of integration is to maintain a stable grid while generating the lowest-cost electricity. Energy sources can be categorized by whether they are dispatchable (can generate power according to a schedule and follow demand within its operating range) and if they have a synchronous front end (able to control real and reactive power flow, either with a synchronous generator or a grid-forming inverter). Energy sources that are both dispatchable and have a synchronous front end do not need any special integration beyond dispatch control, which is fairly straightforward and part of any modern powerhouse. Energy sources that do not have a synchronous front end require other components in the grid to supply reactive power to maintain an acceptable power factor and to provide voltage and frequency reference. Energy sources that are not dispatchable require available spinning reserve capacity (SRC) and standby generation for times when the energy source can no longer meet the load. Spinning reserve capacity can supply instantaneous power while standby generation is brought online. Diesel generators, and usually hydropower, are dispatchable and have a synchronous front end. Biomass and geothermal power generation systems are dispatchable, but often do not have a synchronous front end. Wind and solar photovoltaic (PV) power are not dispatchable and generally do not have a synchronous front end. Integration costs for nondispatchable, variable energy sources such as wind and solar PV power also depend on the nature of their variability. Solar PV power can be more variable than wind, with higher ramp rates, which may result in higher integration costs per installed capacity ($/kW) for solar PV power compared with modern wind turbines. Energy Integration Briefing This wind turbine simulator helps ACEP researchers study ways to integrate wind energy into small, isolated microgrids that rely on high-cost diesel. Integrating high penetrations of renewable energy onto small grids is one of the main challenges of reducing energy costs in rural Alaska. ACEP studies this issue at its Energy Technology Facility in Fairbanks, Alaska.

Current Installations in Alaska

ACEP’s research largely relies on data extracted from applications to the Alaska Energy Authority Renewable Energy Fund, Rounds 1 through 8, and thus may not always represent actual as-built costs. However, the data provide an indication of integration costs.

Key Performance Metrics

Analysis shows that the cost of integration goes up as the amount of wind energy increases on a grid. Specifically, integration costs rose $27/kW per 1 percent increase in wind energy penetration. However, these higher integration costs can be offset by the economy of scales gained for larger renewable energy systems. For integration systems incorporating thermal or electrical storage, the average control integration is around 66% of the total cost, while storage makes up 34%. Control integration equipment includes SCADA, hardware, integration, and testing costs. Different components used in integration have varying efficiencies. A significant example is energy storage, which experiences losses while charging and discharging and during storage (see the Energy Storage for more information). Other components such as switchgear and inverters represent smaller energy losses, typically in the mid and high 90% efficiency, respectively. A well-designed integration scheme will result in much higher energy savings than losses.

Technology Trends

Trends that are being used to integrate higher penetrations of renewable energy in grids include demand-side management, excess generation to heat, energy storage with grid-forming inverters, and advanced control systems. Demand-side management allows electrical loads to be turned on and off, depending on the presence of excess electrical generation. Excess generation can be stored in thermal and electrical energy storage. Electrical energy storage and grid-forming inverters can be used to maintain grid stability and allow diesel generators to be turned off with sufficiently high penetration of renewable energy. Advanced control systems are being developed for microgrids. However, they are often designed for gridconnected microgrids, and it is uncertain how well they will work for remote microgrids.

Images
Left: This wind turbine simulator helps ACEP researchers study ways to integrate wind energy into small, isolated microgrids that rely on high-cost diesel. Middle :Integrating high penetrations of renewable energy onto small grids is one of the main challenges of reducing energy costs in rural Alaska. ACEP studies this issue at its Energy Technology Facility in Fairbanks, Alaska. Right: Integrating variable energy sources such as wind power is more complicated and expensive than sources like biomass or hydropower.