Demand Energy's Demand Shifter

Technical Overview

Demand Energy's Demand Shifter is a distributed, flexible energy storage device, to and from which utility resource managers can dispatch load based on availability and need.

Our patent-pending Demand Shifter is a centrally managed, highly distributed electricity storage unit utilities deploy to locations across their service areas. The unit optimizes existing generation resources by creating load during off-peak times, stores the energy, and dispatches it on command back to the grid during periods of peak demand. By distributing the stored energy near the point of use, an electricity inventory can be monitored and dispatched by utility resource managers within seconds.

This process smoothes the traditional 'peak and valley' usage wave, effectively balancing the load, and relieves generation and transmission resources of stress and congestion. The Demand Shifter complements renewable sources, helps meeting spinning reserve mandates, drives down capital costs, and helps avoid peak pricing.

The storage technology is chemical battery media, typically an advanced form of lead-acid battery technology. The re-generation subsystem powers a rotating motor assembly that transforms into an induction generator. The generator mechanism is a specialized DC motor with auxiliaries.

Available Configurations

Demand-Shifters are presently designed for high density and custom site deployment.

High Density deployments range through three basic output capabilities; 5kw, 30kw and 110kw (it is also possible to sequence devices together for additional flexibility and special requirements). Typical high density deployment scenarios vary from neighborhood residential, high concentration/population load centers, to small to medium industrial, commercial and agricultural applications.

Custom site deployment units are supplied for sizes over 500kW (up to 500kW, the cost-per-kilowatt and kWh favors multiple linked high density unit installations). Base unit sizes will have 2-hour runtime battery storage capacity. Additional capacity is available in hourly increments.

Grid Connectivity

The electric utility interconnection requirements vary with the Demand Shifter unit size and state-by-state regulation, however all Demand Shifters have points in common that simplify interconnection. Those points are:

• All units are supplied with integral non-directional over-current detection circuit breaker subsystems that meet service entrance requirements.
• All units connect to the utility system using industry accepted motor-starter technology.
• The induction generator self synchronizes with the grid utilizing both voltae and frequency from the grid. An “energized-line” is required by the electro-mechanical design for generation to occur.
• Loss of the utility energy source results in mechanical shut down by design. No “islanding” detection subsystem is needed.
• When generating, all units provide positive power system stability response to system disturbances. Optional unit control system parameters allow for automatic unit startup in response to frequency deviations.
• Transient response to external system fault conditions mirrors similar sized induction motor response. This allows for standard utility distribution fusing and fault-study responses while deploying distributed generation devices.
• Units use induction-generation and are incapable of powering a local grid.
• Units do not function as “UPS” for local loads.

Energy Inventory Control

Energy Inventory Control Interface

The Demand Shifter population is managed from the utility's centralized, web-based energy inventory control center. Resource managers have full-time access through a fully secured network that employs proprietary encryption and Demand Shifter ID protocols.

Precise inventory control is managed through a feature rich, user friendly software interface where device storage and dispatch metrics are viewed and controlled in real time. Automatic capabilities allow operators to store and dispatch at optimal, pre-determined times.

Storing Energy in the Demand Shifter

The charger is “powered up” by the Demand Energy Controller initiating a “Charge Schedule” either ordered manually from Inventory Control, or scheduled on an automatic basis.

Shutdown occurs when the “Charge schedule” is complete or the battery is fully charged. A parallel charging system from solar or Wind chargers is available as an option.

Dispatching Energy from the Demand Shifter

The Demand Energy System Controller starts the Brushless DC motor spinning up to near synchronous speed upon initiating a “Generation Schedule” either ordered manually from Energy Inventory Control or scheduled on an automatic basis. For example on a four pole induction machine that would be about 1840 rpm. After reaching the speed set-point the Demand Energy Controller closes the AC Motor Starter placing the induction machine “on-line”. The induction machine operating above synchronous speed outputs full load as a generator. This method of start-up eliminates the typical start-up in-rush and associated voltage dips typical of induction machines.

Shutdown occurs when the “generation schedule” ends or power is lost. The motor starter opens and disconnects the induction machine from the grid and the dc controller shuts down the Brushless DC motor.