Profiles for the Economic Actors in Distributed Energy

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.

As this series continues its survey of Transactive Energy, we get, at last to what I see are the essential agent personalities. The Agent Personalities are a mid-level abstraction that makes it easier for the appliance supplier and the EMS/BMS maker to know what is being attached. Every appliance at the local store could be a pluripotent transactive agent, but this does not aid the brain-developer in understanding what you just bought. A wine cellar may not be on the list of known appliances, but it is useful to know that it is similar to the refrigerator and to an air conditioner in how it approaches the in-home energy market.

http://www.theenergymashuplab.org/blog/8agents 

These agent types interact based on the principals of transactive energy. The non-power services provided and mechanisms used by each system are not known to the energy market. The precise mechanism of each system is not known to the market. Each system uses the market to achieve its own goals.

The creator of a system can identify which economic best suits the system. Some systems may be most easily represented by aggregate roles, wherein each role remain simple.

For example, an air conditioning system and a refrigerator may each act as intermittent consumers. When in the same market, each system can optimize its own costs by buying when the other does not. The air conditioner produces an equilibrium of comfort, the refrigerator produces an equilibrium of the conditions to store food safely, and the market achieves a punctuated equilibrium of power use with lower peaks. An ice maker may act as a pre-consumer, buying power when it is cheap to have a supply of ice at the target time. A pre-consumer buys when others do not, so long as its delivery time and product (ice) can be met. These two agent types may coexist in a single interface just as the two roles coexist in the same refrigerator.

These agent profiles indicate patterns for market interaction. But the market doesn’t care what kind of agent you are. User interfaces, which is to say human interfaces, that want to augment information beyond market summaries, will need to look for another means to discover that information.

The ASHRAE Facility Smart Grid Info Model (FSGIM) allows for communication of expected forward load curves, I think. A controller needs to know more than a partner’s present state. The partners trading position is Inflexible until when? Shiftable until when, then available for how long? How adjustable (shed levels)? Etc. These are all things that higher-level controllers need to get from lower-level controllers. A higher level controller could pass DR-related signals to lower level controllers: it may choose to alter them for its own purposes.

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.

Introducing DERA

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.

Demand response (DR) is the capability of systems that consume or supply power to respond to messages from the power grid. While DR can include using more or less power, or supplying more or less power, for most practical purposes it refers to nodes on the grid reducing the power they are using when they receive a request from a grid operator who anticipates a looming shortage of electrical power.

Many DR programs originally relied on phone calls and other manual processes. Automated Demand Response (ADR) has long been a request of the utilities. A decade ago, the California Energy Commission (CEC) and others funded a project to develop OpenADR 1.0. This work was contributed to the OASIS Energy Interoperation Technical Committee for incorporation into the Energy Interoperation specification. Energy Interoperation specification also defined the common transactive services for transactive energy. The OpenADR Alliance is a trade association that developed OpenADR 2.0 based on the OASIS specification, as well as maintaining interoperability and conformance requirements to insure interoperability of systems that use OpenADR.

The common transactive services (CTS) were designed to offer sufficient communication to operate the North American bulk power markets. Because CTS concerns effects on the market (services) rather than the mechanisms of operation, systems built around CTS can incorporate any technology. Components of CTS-based systems can evolve rapidly, can have their own security, and can support their own internal purposes. At the May 2016 Transactive Energy Conference, representatives of the open-source European initiative PowerMatcher acknowledged that their published services are fundamentally compatible with CTS.

In the fall of 2016, FERC proposed a ruling granting Distributed Energy Resource Aggregates full and unprejudiced access to wholesale power markets. The Federal Energy Regulatory Commission (FERC) is the US agency charged with the safety and reliability of the grid, encouraging energy markets between the states free of manipulation, promoting safe, reliable, secure, and efficient infrastructure. Distributed Energy Resources (DER) names decentralized systems that supply or store energy, as compared to centrally owned and operated generators. Practically, DER refers to systems attached to the distribution network, that is, the power grid that works within neighborhoods.  Many DERs are too small to draw much attention, although their cumulative effect is large and growing. DER Aggregates (DERA) refer to groups of DER the can be marshalled by a common entity. This proposed FERC ruling directs the utilities commission of each state to develop rules that permit DERAs to buy and sell power.

CTS is sufficient for DERAs to communicate with grid operators and with each other to operate a power grid. Energy Interoperation specifies communications sufficient to operate DR and CTS. Power interactions are abstracted to nine (9) services with a half dozen methods apiece. These services can be used to operate resource markets, where resources are commodities whose value is determined by time of delivery. Electric Power, the grid Ancillary Services, as well as the carrying capacity of the distribution network are each resources under this definition.

Local Markets and the Common Transactive Services

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 Common Transactive Services (CTS) simplify integration of a facility into the grid, managing the interactions between facilities and the larger market. CTS can work within a Facility, using the market to smooth and shape the external load curve. This potentially reduces the integration costs of bringing new equipment and technology into a facility that is participating in larger markets.

In proposed regulation on Distributed Energy Resource Aggregates (DERA), directs each state to promulgate rules to allow DERAs full participation in power markets. But what does this mean? One came easily manage the market within the distribution loop, driven by the LMP, and residing under a single injection point from Transmission to Distribution, but what does this mean? We are all waiting for the regulators in each state to tell us.

The Common Transactive Services were defined in the OASIS Energy Interoperation Technical Committee.

There are numerous groups studying the internal market design for agent-based markets, including market rules, and anti-gaming, and … The CTS messages include the means to advertise parameterized market rules for machine understanding. The rule set was defined so as to be extensible. New rules and new rule types is the portion of the CTS most likely to see change.