Category: C&I Generation
C&I customers are starting to be able to take control of their own electric power supply with hybrid systems, such as solar plus storage (S+S) systems. Although more complex than simpler solar systems without storage, these systems will offer C&I facilities the potential to achieve higher levels of reliability, while reducing the facilities carbon footprint and potentially lowering their ongoing energy and demand charges.
To realize this potential facility managers and the engineering firms and equipment suppliers hoping to help them need to understand the design trade-offs that are inherent in hybrid power system design. For example, backup generation can substantially reduce the cost of a S+S power system that can economically support a facility during a grid outage. If resilience is one of the goals of that microgrid, then the designer must have a clear understanding of the trade-off between the size of the battery bank and amount of fuel consumption and deliveries.
Another trade-off exists when sizing the solar array. Photovoltaic panels have become so inexpensive that least cost systems often produce more energy than can be used and utilities are beginning to push back on accepting whatever excess energy a facility wants to export. Sizing a solar array and an accompanying battery bank requires understanding how much curtailment is acceptable. This in turn requires careful modeling of both the facility load and the solar resource.
Load management is another solution where system designers distinguish between high priority loads that must always be served, even in a grid outage, and lower priority loads that can be temporarily curtailed. Having loads that can be curtailed for a few minutes can significantly reduce the cost of a microgrid by alleviating the need for operating a backup generator just to provide spinning reserve.
One of the most important economic drivers for S+S systems is the reduction in demand charges they can enable. Demand charges are typically determined by the highest 15-minute demand. This also requires detailed modeling to accurately predict the demand charge savings from a S+S system. Furthermore, discharging the batteries to minimize demand charges creates a trade-off with the goal of maximizing resilience because it will mean that the batteries are depleted during part of the day and not available in case of a grid outage.
This presentation will show how to analyze these trade-offs with examples from the HOMER software.
Peter Lilienthal– CEO, HOMER Energy