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Daedalus was the mythical great architect and artificer of the classical world. Today, embedded intelligence is enabling the most profound changes in the way we create and use buildings since his day.

Building Intelligence meets the Intelligent Building. The Intelligent Building negotiates with the Intelligent Grid. How will this transform how we interact with the physical world?

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Monday
Jun122017

DER systems in the house and small business

This post is part of the continuing Paths to Transactive Energy series. You can find them all listed by clicking on the matching metatag at the bottom of each post.

The purpose of an energy management system (EMS) or building management system (BMS) in a home or commercial is to serve the owner or occupants of the home or building. Only secondarily is its purpose to “serve the grid”—and then only to the extent that it is rewarded for doing so in a way that supports its owners or occupants.

Every system in a house or building is a legacy system from the moment it is installed (manufactured, actually). No matter what standard we may posit for future use in home systems and home integration, most systems managed by the EMS or BMS will be legacy for some time to come.

The makers of EMS and BMS will compete based on user (and system) interfaces as much as on performance. What is the easier-to-use interface? Which system gives me reporting that I like better? Which system can I connect to my corporate scheduling system? The inputs through these interfaces will inform the EMS/BMS as it responds to market signals from outside.

A common information model will make this market (interfaces) more competitive. The first draft of that information model was delivered last year by ASHRAE 201. Today’s EMS and BMS will work through local direct control and increasingly through a descriptive framework supplied by ASHRAE 201.

Early adoption of transactive services in the home and office will most likely to be for integrating DER inside the facility. The resource frameworks defined in the transactive energy specifications enable a device or system to express capabilities over time and to make forward commitments. The direct control system in the EMS/BMS can negotiate for future requirements without getting into the weeds of understanding a battery management system.

Battery management systems are increasingly supporting complex internal ecosystems of their own, embedded with integrated circuits and composed of hybrid technologies. These circuits manage battery life through creative monitoring of charge rates, temperature, and power factor. The BMS may take a cell off-line, recondition it over much of a day, and then restore the rejuvenated cell to full service. Flow batteries manage different chemistry and physics to manage dendrite development. Hybrid systems combine systems optimized for long slow charging and discharging with more nimble technologies able to take and provide fast charges.

No businesses will benefit more from virtuous markets for the rapid development and evolution of storage systems than those of the EMS/BMS developer. Rapid evolution and thriving markets could mean the unending development new drivers for new batteries. Even with drivers in place, batteries change in capabilities over time, and based on usage patterns; a full understanding of this year’s capabilities may not be adequate for optimum interaction with the same system after a year’s use. The solution is for battery management systems that are self-managing, can express their capabilities over time.

This requirement describes a transactive node able to describe its forward capabilities and make forward commitments. A battery system must be able to commit to service directives such as “be ready to provide a specific power curve for the 12 hours beginning at dusk”. A battery system must be able to communicate that if it commits to a transaction, it will needs six hours of charging to recover. It must be able to commit to standing requirements (“always have four hours available”) while fully discharging individual cells to maintain capability.

Renewable generation can pair with such systems, and will sometimes interact with a storage system to provide a single hybrid service. (This may well be structured as a transactive nanogrid interacting as a single node within the microgrid). Renewable generation, like battery management systems, is most likely to be part of a new installation. Such systems will likely follow the transactive model for behind-the-meter integration as soon as intelligent power controllers support integration by semi-skilled labor.

This describes a hybrid model, with the bulk of legacy and consumer equipment under direct control of the EMS/BMS, but informed by the transactive commitments of the newer systems. In this hybrid microgrid, the market is shallow, so the resource descriptions are useful.

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