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Renewable Penetration Metrics

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The Renewable Penetration tab in the Simulation Results window is available when the system contains renewable components. It provides a variety of metrics for quantifying the renewable penetration of the system. Which metrics are most relevant depends on your system and its application. Depending on excess electricity, unmet load, and other factors, the values calculated with the various metrics can differ significantly.

Capacity-based Metrics

The nominal renewable capacity and usable renewable capacity are divided by the total capacity to produce the two renewable penetration figures listed in this table, Nominal renewable capacity divided by total nominal capacity and Usable renewable capacity divided by total capacity. The total capacity includes the renewable capacity, and adds the total nonrenewable capacity, which is the sum of the capacities of all of the non-biofuel generators in the system.

These values are calculated based on the specifications of the system components, and do not reflect the operation of the system in simulation. The nominal renewable capacity is the sum of the rated capacity of PVs, wind turbines, hydroelectric generators, hydrokinetic generators, and biogas-fueled generators or regular generators, plus a value for each custom component and biogas-cofired generator. The usable renewable capacity is similar to the nominal value, but takes into account the PV derating factor, the actual peak of the wind turbine power curve, the maximum capacity and pipe head loss of hydroelectric components, and the actual peak of the hydrokinetic power curve.

Custom Components contribute to the nominal renewable capacity and the usable renewable capacity in the same way. The renewable percentage specified for the Custom Component is multiplied by the maximum output of the component during simulation, and the product is added to the total renewable capacity. For example, a Custom Component with a peak output of 10 kW in simulation and 45% renewable percentage contributes 4.5 kW to the renewable capacity. Although the capacity-based metrics are based on component specifications and not simulation behavior, the custom component does not have a rated capacity, so HOMER uses the maximum power output from simulation as a substitute.

Biogas generators is considered as 100% renewable for this metric. Biogas-cofired generators are partially renewable according to their minimum fossil fraction. For example, a 100 kW biogas-cofired generator with a minimum fossil fraction of 20% has 80 kW of renewable capacity and 20 kW of nonrenewable capacity.

Energy-based Metrics

The penetrations reported in this table reflect the total energy (i.e., kWh) produced and consumed in the simulation. They are Total renewable production divided by load, Total renewable production divided by generation, and One minus total nonrenewable production divided by load.

The total renewable production is the sum of all energy generated by the PVs, wind turbines, hydroelectric components, hydrokinetic components, and biogas-fueled generators over the simulation. Production from each custom component is multiplied by the renewable percentage of that component and then added in to the total renewable production. The effective renewable fraction of each biogas-cofired generator is calculated based on the biogas energy input relative to fossil energy input. The production is divided up accordingly.

The renewable production is divided by the load, which is the total electrical consumption (found under the Electrical tab) for one metric. It is divided by the total electrical production (found under the Electrical tab) for the second metric. Finally, for the third metric, the total nonrenewable production is the sum of all production from generators (excluding biogas).

Peak Values

The Peak Values table reports the largest value from each of the time series plotted in the three DMaps. The values are Renewable output divided by load (HOMER standard), Renewable output divided by total generation, and One minus nonrenewable output divided by total load.

These time series metrics are calculated similarly to the energy-based metrics. The generation from PVs, wind turbines, hydroelectric, and hydrokinetic are all added together to calculate the renewable production in each time step. The output from Custom Components are divided between renewable output and nonrenewable output according to the component's renewable percentage. Generator production is considered renewable if the generator uses biogas. For a cofired generator, the production is divided between renewable and nonrenewable categories according to the fossil fraction in that time step.