Modeling of a High-Efficiency, Resilient, Dual-Battery Microgrid combined with Diesel GenSet and Solar PV
Clemens van Zeyl | AccordEl, Inc
The objective of Phase I will be the modeling of a high-efficiency, resilient, dual-battery microgrid combined with diesel generator set ("Genset") and solar photovoltaic (PV) generating system. Specifically, for the five selected installations, the model will forecast the economics of each installation by calculating, as a minimum:
- revenue generation,
- operating costs,
- terminal value, and
- internal rate of return before cost of capital and taxes ("IRR").
The model will also include a "Performance Model" that will calculate, as a minimum:
- critical load coverage probabilities,
- power flow, and
- battery state of charge.
These, and other variables, will be visually presented for understanding of the microgrids performance.
The electrical energy storage solution involves the combination of a "power" battery with an "energy" battery. A power battery is generally considered to have a power to energy ratio of 2:1 or more (i.e. 30 minutes of storage or less) (a "Power Battery"), whereas an energy battery is generally considered to have a power to energy ratio of less than 2:1 (i.e. more than 30 minutes) (an "Energy Battery"). Energy Batteries can be further divided into low, (0.5 to 1 hr) medium (I to 4hrs), high (4 to 12 hrs) and bulk (>12 hours). By combining a power battery with an energy battery the benefits of each can be optimized in terms of the total solution. Li-Ion Power Battery and Redox/Redox Flow Energy Battery technologies will be modeled, and ultimately deployed as part of Phase II.
To integrate the PV generation, initially the design will be AC connected with a second inverter controlling the power of the PF generator. Ultimately, the design will couple the solar PV generation to the DC bus using DC converter, similar to the energy battery. This concept lends itself to scalable module ratings from 10kW to 1000kW with different amounts of plug and play energy storage.
The resilient microgrid illustrated in Figure G (below) offers an opportunity to deploy standard Renewable Energy Power (REP) Modules to form Autonomous Microgrids that can be deployed as either, a standalone power plant, or interconnected to form a Resilient Microgrid. The Autonomous Microgrids can be scaled down to lOkW or up to lO00kW which can be scaled up to multi-megawatt systems. Resilient Microgrids can be interconnected to the main electric grid, or islanded for the provision of backup power. The modular approach enables the system to be used throughout the military, including "hardened" uses.
The batteries offer a highly robust energy storage solution including a high-degree of safety and wide range of environments (i.e. a wide range of temperatures).
The configuration of the energy storage system within the REP Module lends itself to "plug and play" Energy Battery that can rapidly deploy depending on site specific energy storage requirements. The same is true for PV generation.
Typical economic paybacks, depending on location of deployment, are typically in the range of two to 10 years. In case of combat, a Resilient Microgrid is able to "self-heal" and can be of immense value in terms of loss of life and equipment.
Deployment of REP Modules will dramatically extend the life of diesel Gensets through minimal operation at their optimum point of efficiency and maintenance.