Energy Aggregation and Information System
City of Cedar Rapids IA, 2002
Full text of article in Sensors, June 2003

This small city's energy bills were based on demand peaks from each of about 50 meters. When compared to billing based on the peak of the aggregate demand, the City calculated they were charged an excess of $24,000 per month. To provide the information to address this issue the city energy manager wanted real-time and historical data on electric use and emergency electric generation. Updates every 4-sec and at 15-minute time boundaries were required with internal and external web based data access. Even without a billing change the city expected to realize immediate significant savings by identifying cases of excessive peaks at individual meters and reducing them through better activity scheduling.

The City's aggregate electric use and backup generation readings were to be made available to energy suppliers serving the city. Theoretically such information would allow suppliers to better manage reserves and distribution resources, lowering cost of production and earning a rebate to the City.

The City solicited innovative solutions that would allow them to obtain data from their existing older meters and utilize their current IT infrastructure. Most potential system vendors suggested that the first requirement would be to replace all the existing meters with IP enabled units. That alone would have exhausted the city's project budget and yielded not one piece of data. Vendors also suggested that a new dedicated IP network would be required to support the bandwidth intensive 4-second data collection.

DR DAS innovative design was selected and they developed and installed a solution in which stand alone meters were IP enabled with the addition of meter gateway devices that interfaced to the meters via digital contacts or serial ports. The gateways then pushed XML data documents over any existing IP enabled media to a central Microsoft SQL Server 2000 database.

Meters that were already connected to a data highway were accessed through an add-on OPC server node. These approaches made use of the existing infrastructure and thus had an inherently lower cost. By only transmitting 4-sev values when changes occurred network traffic was kept to a minimum.