Microgrids: Smart or Dumb?
At present, regulations governing energy have not kept pace with emerging microgrid islanding technology, frustrating immediate progress. Most of the public and private investment dollars pouring into modernization of the globe's electric grid have been soaked up by utility smart grid deployments, with very little funding filtering down to the microgrid level of design and deployment.
Academics from the University of Wisconsin-Madison -- an institution often credited with the birthing of the microgrid concept (at least in engineering terms) -- predict it could take 30 years for the microgrid to become ubiquitous. Yet current trends appear to make microgrids an inevitable augmentation of today's centralized grid infrastructure. Aggregation platforms similar to microgrids will be absolutely necessary if our energy infrastructure follows in the footsteps of telecomm and the evolution of today's Internet. No doubt the existing radial transmission grid will still provide the majority of power supplies to the industrialized world. But renewable distributed energy generation (RDEG) will also play a larger role in providing energy supply, reliability, security and emergency care services.
Given consumer pushback on smart meters -- the very underpinning of the utility-dominated "smart grid" -- in California, Texas, Colorado and elsewhere, the microgrid represents an alternative business model for boosting the quality of grid services. It is becoming self-evident that the hype behind the Obama Administration's stimulus spending on smart grid upgrades raised expectations to unrealistic heights. Furthermore, utilities focused too much on the benefits meter data might bring to their own operations -- and forgot to connect the dots with consumers, many of which only saw higher bills, and no coordinated programs and tools to respond to real-time price signals with more efficient consumption patterns and protocols. And then there were the concerns about data security.
The goals of both the smart grid and the microgrid are the same: to maximize generation assets through embedded intelligence while dramatically boosting efficiencies, thereby minimizing costs. However, they appear to offer two potentially different paths forward.
Both "supergrid" and "microgrid" will need to get smarter, though it is the distribution system that is currently the prime source of outages and unreliability. Today's distribution grid network is clearly inadequate to support the type of innovation now occurring with distributed resources, including devices such as plug-in hybrid electric vehicles (PHEV) serving as distributed storage batteries. The question is: Do we need bottom-up or top-down innovation?
Microgrids installed in developing nations or rural regions of the United States may be quite simple, even "dumb" if compared to the hyperbole often attached to descriptions of the smart grid. The Consortium for Electric Reliability Solutions' (CERTS) demonstration projects show that microgrids do not necessarily need to rely on all of the sensors and fast, real-time communication protocols that are hallmarks of the smart grid.
Among the current microgrid control options are centralized management systems requiring high-bandwidth links between the inverters and central controller. Other prototype microgrids rely upon distributed on-board control that reduces the bandwidth needed -- but at the cost of synchronization difficulties. More recent work has investigated a hybrid control scheme where proximate inverters operate in a master-slave arrangement. Still others are focused on remote or smaller microgrids are sticking with common frequency droop method, commercialized through the CERTS work, which greatly reduces the need for any high-bandwidth communications over large distances.
Control systems fall into two major camps. The purists -- epitomized by the CERTS software -- believe that microgrids should operate without any central command and control system, with generators and loads harmonizing autonomously based on local information. This is the view espoused by leading academics and localization advocates and the rationale is compelling. This system will work for the majority of smaller microgrids with a single owner and whose top priority is reliability and sustainability during emergencies. These are the "dumb" microgrids, if you will.
In the other camp are what you might call the pragmatists. They lean toward systems that can be described as "master/slave," (whereas the CERTS approach has been described as being "like a commune.") These operating systems are much more focused on optimization of services outside the microgrid. The benefits of reliability may come second to generating new revenue streams from excess generation (or even demand reductions.)
There are also those systems that can straddle these two views. There are few clear cut direct competitors in the space since no standards exist and microgrids are so modular, diverse and optimize such a broad array of energy-related services. It is these control systems -- still literally being defined -- where the fiercest competition may reign within the microgrid space. This is the guts of the microgrid, if you will, and the focus of current software innovation.