A Microgrid of One
Thursday, November 12, 2009 at 12:41PM
Toby Considine in Decomposition & Disintegration, Intelligent Buildings, Microgrids and Distributed Systems, Re-thinking things, Services, Smart Grid, System Architecture, Zero Energy Buildings

The target of smart grid communications, particularly in collaborative energy space, should always be the microgrid. Some microgrids may contain a single home, or commercial building, or and industrial site—those are irrelevant details. Microgrids have a number of systems inside them that must work within the economic environment of that microgrid—and I am thinking of old economics, before the distinction of economics and ecosystem arose. Some microgrids may have a single entity inside, say a legacy BAS (Building Automation System), but the unitary microgrid is merely an artifact of the way we have always done it. The energy services interface is the gateway to a microgrid.

Microgrids contain collections of systems that may not share common technology. Some of these systems are small, self contained, and serve special purposes, such as appliances. Some are large and complex and span significant space, such as HVAC or an industrial line. Some look alike, are built from the same components, but have different missions; the laboratory fume hood and the air conditioning system are run for different purposes and have different constraints. Some may rely on different energy markets to do the same work; heat may come from electricity, gas, or solar thermal in the same building. Some systems may store generate energy used by other systems. All of these coexist in the ecosystem of the microgrid.

Diversity is the source of resilience in the economy and ecosystem. Monocultures fail badly in either. The diversity of systems in a microgrid is a source of stability. This is as true of the microgrid spans a campus or spans a high-rise. One source of diversity is diversity of response, which is tied to diversity of business service provided. A unitary system all too often has too few response options. Without expensive and non-standard integration, these simple systems are unable to expose nuanced and diverse services for manipulation by the humans, and human processes, they serve.

Diversity within kind (read Darwin for a definition) in building systems can come from multiple technologies (hard to maintain), or from multiple systems programmed quite differently (expensive to integrate) or from identical systems responding to different users. Diverse systems can be much more agile, just as individuals can be more agile than a committee. I posit that a collection agile systems is better able to respond to heterogeneity of environment, including unpredictability of power supply, than is a single committee of systems.

Diversity of services can provide new assets to the commercial building owner. Green leases seek to tie technology, capital, and performance together to please the tenant. Green leases require separate metering and operations for each tenant to be credible. Green leases in a high rise might work best with a number of identical systems, one for each tenant, rather than a monolithic system that responds only to all. Diversity is an amenity that enhances tenant service and leas ability.

How do we distinguish a microgrid from a grid? The external interface should be the same. Inside, microgrids are more intimate, they are the safe neighborhood the kids can go out and play in. Alternately, they may be more dangerous, the prison society in which no inmate must reveal anything. A microgrid defines a security context and a security posture. Intimacy and sharing and collaboration are all a part of some contexts—and not of others.

To me, the most interesting question of the week is what information do the systems within a microgrid need to share as they support their divers purposes and work within their mutual constraints. I know it starts energy usage, and predictions of energy usage, because that is the common resource they share within their environment, the basis of their economy and their ecosystem. I suspect they need currency, to negotiate their access to resources within the constraints of the microgrid—although I am not sure that currency is always expressed in legal tender. Some systems may only be able to buy at certain stores, or sell to certain buyers.

I’m not sure what else they share.

Article originally appeared on New Daedalus (http://www.newdaedalus.com/).
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