A new technology from Heart Transverter is changing the way we look at the Smart Grid. The Transverter uniquely addresses problems associated with Demand Response and the integration of Renewable Energy with the utility grid.

The new paradigm for Smart Grid implementations leverages homes and light commercial business for the purpose of networked energy storage, providing the basis for widespread Demand Response capability. A typical home or business will have 5 kWh of battery storage. A thousand homes will in turn provide 5 Megawatt hours of storage for Demand Response. A million homes or businesses will provide 5,000 Megawatt hours of storage.

The Demand Response function in the Transverter is unique in that it can be used both for supplementing the grid from stored energy and for managing interruptible loads.

Let’s start with the approach of managing interruptible loads, and examine some statistics from the ISO New England Demand Response Reserve Pilot [1].

“The central objective of this document is to describe performance of assets that participated in the Demand Response Reserve Pilot (DRRP). Performance was assessed by measuring how quickly and consistently participating assets, individually and as a whole, could reduce load in an amount relative to the quantity of interruptible capacity enrolled in the DRRP.

The DRRP was designed to test the ability of smaller demand response (DR) resources to respond to ISO dispatch instructions in a manner similar to resources providing Operating Reserve. While there is some data available from other areas on the performance of certain DR resources providing Operating Reserve, those resources are not similar to the types of DR resources participating in the New England markets. The DRRP was developed to acquire performance data for the types of DR resources that exist in New England in response to more frequent, short-duration activations like that of Operating Reserve resources. The DRRP also was intended to enable system operators to more accurately predict the likely performance of DR resources in varying system conditions, which would contribute to the analysis of contingencies and engender more confidence in the use of DR resources for enhancing system reliability at lower cost.”

The total Enrolled Amount varied between 47.3 MW (consisting of 37.3 MW of Load Reduction Assets, and 10 MW of Direct Load Control Assets) in the summer of 2009 to 18.6 MW (consisting of 13.7 MW of Load Reduction Assets and 5 MW of Generation Assets) in the winter of 2007/2008. As mentioned above, one session included 0 MW of enrolled capacity. The average Enrolled Amount was 26.4 MW per session. Generally, the Enrolled Amount reflected each asset’s maximum interruptible capacity.

Now consider this scenario. 13,500 homes or businesses are enrolled in an Aggregated DR program.

To exceed the average enrolled amount for a DR session of 26.4 MW per session, each home or business would have to shed 500 watts each for 4 hours. Alternatively they could shed 2,000 watts for an hour. This achieves a total 27 MW exceeding the average enrolled amount for a DR session!

Another issue to consider is response time. The response time in traditional Demand Response scenarios is typically 30 minutes to two hours. Some programs, such as ISO New England’s Real-Time Price Response program, call for up to one day ahead. The “Real Time” program is based on a 30-minute to two-hour response time.

By definition, demand response is a service to the grid to either supplement energy to the grid or reduce load. The Transverter can do both with response times on the order of 17 milliseconds or one wave shape.  This high speed response can mean the difference between a power outage in a grid sector or maintaining normal service.

The Transverter incorporates two primary devices to accomplish these tasks. One is the Transverter Power Module, and the other is the Smart Load Controller. The Power Module can inject power into the grid from energy stored in batteries, from a solar array or both. The Smart Load Controller can instantaneously shed loads and bring them back on based on programmable criteria. The Transverter will typically be the early responder which will serve to minimize the effect of the slowness of other demand response providers.  The Transverter responds to external demand response signals or can also create its own demand response signals based on the monitoring of the grid conditions locally, eliminating the time, expense and complexity of dedicated communication networks.

For more information about the importance of response time and the integration of intermittent renewable energy generation, consider this excerpt from a paper authored by Libin Jiang and Steven Lo, Division of Engineering & Applied Science at Caltech:

“We believe that demand response will not only be invoked to shave peaks, but increasingly be called upon to improve security and reduce reserves by adapting elastic loads to intermittent and random renewable generation. Indeed, advocate the creation of a distribution/retail market to encourage greater load side participation as an alternative source for fast reserves. Such application however will require a much faster and more dynamic demand response than practiced today.

This will be enabled in the coming decades by the large-scale deployment of a sensing, control and two-way communication infrastructure, including the ?exible AC transmission systems, the GPS-synchronized phasor measurement units and the advanced metering infrastructure, currently underway around the world. Demand response in such context must allow the participation of a large number of users, and be dynamic and distributed. Such dynamic adaptation is being practiced everyday on the Internet in the form of congestion control. Although the grid and the Internet are different in their engineering, economic, and regulatory structures, the precedence on the Internet lends hope to a much bigger scale and more dynamic and distributed demand response architecture and its bene?t to grid operation. Ultimately it will be cheaper to use photons than electrons to deal with a power shortage.”[2]

One problem that becomes evident is that consumers or small businesses are not going to be sufficiently incentivized by the current $0.10 - $0.20 kWh.

The answer may be in offering the consumer a completely different value proposition. One that simultaneously addresses the need for demand response programs for the utility grid and a system for the consumer that provides energy security in the form of back-up power.

Now let’s add to the value proposition, the integration of renewable energy into a Smart Grid system. The grid-tie solar market continues to grow, partially driven by consumers wanting to be “green” and partially driven by various economic incentives. Grid-tie solar systems, however, do not typically provide backup power.

Now consider the Transverter technology.

The Transverter is unique in that it can be used both for supplementing the grid from stored energy and managing interruptible loads.

A unique combination of functions enables Smart Grid implementations that generate revenue for the system operator, reduce electric utility costs with renewable energy while providing energy security for the end user. 

The Transverter provides this unique combination of functions:

• Bidirectional Grid-tie Inverter
• Demand Response
• Load Management
• Power Factor Compensation
• Uninterruptible Power Supply
• Solar Charge Controller with MPPT
• Data Logging and Communications
• Scalable Integration of Renewable Energy

A typical installation is shown in diagram 1-A. In this installation interruptible loads include a combination of loads from the Main AC Panel.   Energy from battery storage and/or the solar array can be used for demand response. An optional communications gateway provides for TCP/IP or GSM signals to be transmitted to the Transverter to initiate demand response.

Diagram 1-A Typical Transverter Installation

The Transverter also solves the problem of scalability of renewable energy. Renewable Energy sources such as solar and wind systems are unpredictable, and when they become significant (over 15% of grid capacity) it can destabilize parts of the grid.

In fact, Stephan Kohler (News - Alert), chief executive of the German Energy Agency (DENA), told Berliner Zeitung news network that the “skyrocketing solar PV capacities might cause the grids to collapse.”

In summary, the Transverter technology is capable of causing a paradigm shift in the Smart Grid through vastly improved demand response times and the integration of networked energy storage and renewable energy into the utility grid.

About Heart Transverter, S.A.

Heart Transverter is based in Costa Rica with offices in Boulder Colorado and Bellevue, Washington. Heart products have been in continuous service for over 23 years in residential solar, applications in telecom, back-up power and other markets. Heart has been in the inverter business since 1982, having started and created the original high efficiency inverter for solar and transportation markets - Heart Interface. The Transverter represents the next generation of inverter technology.