Jon Longtin Department of Mechanical Engineering SUNY Stony Brook

Jon Longtin Department of Mechanical Engineering SUNY Stony Brook

Jon Longtin Department of Mechanical Engineering SUNY Stony Brook jlongtin@ms.cc.sunysb.edu 631 632-1110

Overview The Neglected Gas Meter Current State of the Art Proposed Innovations SMART Technology Security Conclusions and Future Work

The Neglected Gas Meter Smart Metering is the most advanced area of Smart Grid Technology Electric Meters get all the attention State-of-the-art replacements available Costs $30 50 with installation Active area of research Gas and Water meters have been neglected

The Three Utilities Electricity Water Gas Metering Principle No. of Appliances Variable Usage Electrical Mechanical Mechanical 30-50 15-25 3-4 Often Sometimes Seldom Usage Range uw-kw (~10 9 ) 10 0z/min-10 GPM (~10 3 ) 1-250 ft 3 /hr (~100) Annual Cost (relative to electricity) 100% 10% 50-125%

Gas and Water meters Reasons for neglect Are mechanical in nature Replacement costs $100 150 with installation (> 1hr installation time) Requires service interruption. A retrofit module that can be attached to existing meter is the most feasible solution

Problem Statement To monitor usage of gas appliances: Usage/cost reporting to consumer Efficiency / suggestions for cost reduction Leaks / theft / problems Energy budgeting Appliance-specific rates ($ heat < $ drying) Current billing of 1/month too coarse to make meaningful energy adjustments Even AMI/AMR data too course to determine behavior of single appliances

Current State of the Art J1 No High Resolution Capability on currently available AMR Current commercial players include ITRON, CellNet, Elster, others All use one or more of the following Dedicated frequency space (FCC) Proprietary hardware/protocol They provide: Tx, Rx, trunks, relay points, etc. Competing technologies not compatible

Slide 8 J1 This needs to be updated. Itron has a new system out about a year ago that does a lot of things. Jon, 07/02/11

The S.M.A.R.T. Concept SMART - Single-Meter Appliance Resource Tracking Most gas appliances use gas in a binary (ON/OFF) fashion (boiler, hot water, dryer, pool heater, oven) Small number of gas appliances (N = 4) Total combinations of appliances = 2 N 1 (7 for N = 3; 15 for N = 4) Manageable! By monitoring usage signal of each appliance, can determine usage

S.M.A.R.T. Illustration Cycling of a boiler and hot water heater vs. time (top) Gas usage rate plotted (middle) Total gas consumption (bottom)

Key Components Retrofit to existing gas meter Hardware requirements: High-resolution encoder / gear train Microcontroller and clock Housing and power (Standard wireless package for AMI) Retrofit module

Comparison

System Architecture

Residential Gas Meters American Meter : AC-250 Standard diaphragm / bellows design Meters popular for residential metering because of the lack of alternatives. Measure gas in the 1000 s of a cubic feet Very low friction and highly reliable

Meter Operation & Anatomy Slide valves divert gas through each diaphragm in alternate fashion Mechanism is timed to correctly positions the slide valves in open and close positions

Meter Operation & Anatomy Mechanism transfers the diaphragm movement to a counter or index through gear train Internal gear ratio 18:1 Output shaft: 1 revolution (360 o ) = 2.0 ft 3 of gas

Hardware Overview High Resolution optical Encoder 720 PPR Atmel AVR microcontroller 4kb memory, 256b non-volatile, 20 MHz, 16 bit timer, interrupts and power management: ~$1.00 in quantity. Dallas Semiconductor DS1307 RTC TelosMote (Zigbee) Radio 802.11 modules w/ RS-232 interface Li batteries (4 x 1.5V) Housing and switch: American meter retrofit

System Overview Retro fitted module will have all hardware required Meter readings are communicated wirelessly local broadband router cellular site or telephone interface

Experimental Setup Replicate actual flow rates & pressures w/ compressed air Independent flow meter for validation Clear plastic top to visualize motion

Non-linear Meter Motion 720 PPR/18 = 40 PPR internal meter Constant flow of 49 L/min Over 2x variation in mechanism speed!

Video Measurements To analyze internal meter motion independently of the output shaft

Different Flow Rates Reasonable separation for different flow rates Data is repeatable over several cycles Must compensate (software lookup table)

Error Analysis x36 Results from an error analysis over 36 cycles of the Internal Meter Motion Results also demonstrate repeatability

Scaling Meter rotation rates normalized by their flow rates fall onto one single curve Scaling is done by a flow rate of 49 LPM

Scaling cont. Flow rate Scaling factors based average pulse width Scaling factors based on flow rate ratio 9 LPM 4.19 49 LPM/9 LPM = 5.44 16 LPM 2.39 49/16 = 3.06 26 LPM 1.58 49/26 = 1.88 49 LPM 1.00 49/49 = 1.00 58 LPM 0.84 49/58 = 0.84 64 LPM 0.75 49/64 = 0.77 73 LPM 0.67 49/73 = 0.67 Higher flow rates as ratios of their actual flow rates. For lower flow rates, the values are not as predicted. Can use multiple reference tables to overcome this issue

Flow separation Flow rates separated by using the table Noise in data but the different flow rates are distinct

Calculation Procedure 1.Wait until encoder reaches home position 2.Record time of the first encoder pulse 3.Record time of next encoder pulse 4.Calculate current position of internal meter mechanism based on encoder position, and multiply the correction factor with measured time interval between two most recent pulses. 5.Use time interval from previous step and scale factors from Ref. Table and get actual flow rate. 6.Go to step 3 to repeat.

Averaging Averaging techniques can be used for smoothing the data System responds quickly to changes

Encoder Concepts Reed-switch based for low power and cost Gear train will have 18:1 or 36:1 gear ratio

Encoder Concepts Housing Gears Rapid prototyping of housing was done to confirm dimensions and fit Commercial nylon or equivalent gears will be purchased for final prototype

Security Electronic tamper indicators trigger a security event if opened logged, time stamped and reported Traditional tamper deterrents tamper plugs used on regular meters provide a permanent, visual indication of tampering. Retain mechanical dials and current meter rdg. original meter index is retained, not changed during the retrofit

Security Data Encryption 128 Bit AES Encryption (NIST approved) prevent insider and outsider attacks Meter Authentication Ability to validate meter Network and device level authentication Freshness and Integrity Checks Prevent replay attacks Anomalous Usage Detection Abrupt changes can be assessed by comparing usage to historical trends

Benefits Real-time usage Lower reading cost Detect leaks, theft, furnace failure Can detect 2 ft 3 vs. 20,000 ft 3 Remote energy control (fires, turn off/on) Feedback to consumer Behavior modification

Challenges Stove / grill non-binary usage 2 appliances with similar consumption rates Cannot tell apart Can use additional data (time of use), or equip one with a sensor, or simply count both and average Backlash, friction and play in gear train Cost must be economically viable Encoder / housing / gear train ~$10 (in qty) Electronics (microcontroller / radio) ~$20 (in qty)

Challenges cont. Power Issues Battery charges a concern Battery life Ideas Long-life Li-ion batteries Solar cell to recharge Wall wart with fiber cable for dark areas (no electricity!) Aggressive power management Interrupt-driven processing, synchronized data collection to minimize on times, etc.

Conclusions and Future Work Patent filed March 27, 2010 (Stony Brook University) Opportunities to Commercialize? Partner with established AMI/AMR company? Partner with smaller company? New venture? Funding: NYSERDA Wireless Utility Monitoring, Control, and Response (MCR) for Efficient Energy Utilization, Agreement No. 10908 (J. Love) Jon Longtin Department of Mechanical Engineering SUNY Stony Brook jlongtin@ms.cc.sunysb.edu 631 632-1110