HOMER Knowledge Base
How to design a PV fuel-saver system in HOMER Pro
A PV fuel-saver system is a hybrid system that consists of solar PV and diesel generator. As the name suggests, this hybrid system is intended to reduce the diesel generator’s fuel consumption. The output from PV serves the load whenever available thus curtailing the use of diesel generators.
To build a PV fuel-saver system in HOMER Pro, you will need a generator component, a PV component, and a load. A fuel-saver will allow the PV to serve any load above the minimum output of the generator. In HOMER, the minimum output is set by specifying the generator’s minimum load ratio. This ratio prevents the generator from operating at low load levels. For most diesel gensets, this is important to prevent damage to the genset. Most manufacturers provide recommendations on the appropriate value, which typically ranges between between 25-40%.
The figure below shows how PV shares the load with the diesel genset. Notice that the generator output remains above minimum output, which results in excess electrical production. The excess electrical production results because the PV output added to the minimum power output from the generator exceeds the primary load. Excess electricity is surplus electrical energy that must be dumped (or curtailed) because it cannot be used to serve a load or, in the general case, charge batteries. Excess electricity occurs when a surplus power is produced (either by a renewable source or by the generator when its minimum output exceeds the load) and the batteries are unable to absorb it all.
A PV fuel-saver will typically require the generator to run at all times to serve the load. There are two ways to accomplish this:
1. Under the generator’s schedule tab, force the generator to run on a specific schedule.
OR
2. Set the PV operating reserve requirement to 100%. This will require the HOMER software to operate other components—in this case the generator—to satisfy the load reserve requirements, regardless of the amount of PV production.
Please open HOMER Pro and go to File > Open Samples > Sample_MiningOperationRetrofitWithPV.homer to view an example.
To build a PV fuel-saver system in HOMER Pro, you will need a generator component, a PV component, and a load. A fuel-saver will allow the PV to serve any load above the minimum output of the generator. In HOMER, the minimum output is set by specifying the generator’s minimum load ratio. This ratio prevents the generator from operating at low load levels. For most diesel gensets, this is important to prevent damage to the genset. Most manufacturers provide recommendations on the appropriate value, which typically ranges between between 25-40%.
The figure below shows how PV shares the load with the diesel genset. Notice that the generator output remains above minimum output, which results in excess electrical production. The excess electrical production results because the PV output added to the minimum power output from the generator exceeds the primary load. Excess electricity is surplus electrical energy that must be dumped (or curtailed) because it cannot be used to serve a load or, in the general case, charge batteries. Excess electricity occurs when a surplus power is produced (either by a renewable source or by the generator when its minimum output exceeds the load) and the batteries are unable to absorb it all.
A PV fuel-saver will typically require the generator to run at all times to serve the load. There are two ways to accomplish this:
1. Under the generator’s schedule tab, force the generator to run on a specific schedule.
OR
2. Set the PV operating reserve requirement to 100%. This will require the HOMER software to operate other components—in this case the generator—to satisfy the load reserve requirements, regardless of the amount of PV production.
Please open HOMER Pro and go to File > Open Samples > Sample_MiningOperationRetrofitWithPV.homer to view an example.