Joule Jotter: An interactive energy meter for metering, monitoring and control Prabhakar T.V, Nisha Bhaskar, Tejas Pande Department of Electronic System Engg, Indian Institute of Science, Bangalore Chaitanya Kulkarni National Institute of Technology, Surathkal, Karnataka [email protected] (tvprabs, nisha.b, pandet) @dese.iisc.ernet.in ABSTRACT Utility companies worldwide are adopting Demand Side Management (DSM) methods to cope with unpredictable demands. Demand Response (DR) is a common strategy in which the utility encourages users to change their demand patterns dynamically, so as to have short-term reductions in aggregate energy consumption. While users are concerned about rising costs of electricity bills, utilities are concerned about shortage of power and the real time-pricing they have to pay energy generating companies to meet the peak demand and supply. In this paper we describe “Joule Jotter” (JJ) a smart energy meter that bridges the gap between utility providers and domestic users equipped with such smart meters. We show the scalability of our protocol integration. Simple algorithms are implemented that work with utility requests. Our evaluation results indicate that such energy meters suffer additional time overhead of 1.5s due to Smart Energy Profile (SEP) 2.0 protocol implementation. Keywords DRLC, SEP 2.0, DER, SMS, TOD, Pricing 1. INTRODUCTION In India, technology adoption in electricity usage has seen success in several interesting ways. For example, monthly bills generated by the utility company required transparency. Human error in reading the electricity meter now uses a camera picture to digitally record the reading. This picture is transmitted to the central database for generating the monthly consumption bills. Pre-paid electricity payments have seen the adoption of scratch cards that are available at convenient outlets such as gas stations, shops and retail outlets. While users are concerned about their monthly bills, utility companies have issues to source power by way of higher payments to generating companies. Utilities pay for power based on “real-time” price but only charge “flat rate” Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Copyright 20XX ACM X-XXXXX-XX-X/XX/XX ...$15.00. from domestic users. In the event of peak demand exceeding the supply, utilities target home segments by temporarily cutting power supply; commonly called “load shedding”. It is not uncommon to have 6 to 8 hours of load shedding in suburban areas, followed by many hours of low voltage. Thus utilities earn the wrath of domestic consumer who constitute the 30% of market segment of power consumption. Rising costs of electricity bills and lack of empathy by the utilities has prompted home users to look for new solutions. Several brands of “smart energy meters” have appeared in the markets with the end user in focus. Users are seeing benefits because instantaneous energy consumption feedback is now available. Interestingly, the smart energy meter appears to have arrived like a boon to utility companies as well. Utilities are now offering the domestic users with incentives with a view to reduce the gap between peak demand and supply. For example, the user may switch on the electric geyser in the late evening instead of the regular morning peak hours. Washing machines might have to be operated late afternoon for “cupboard dry” clothes. For utility companies, DSM mechanisms and DR programs are required to handle and service short time scale increases in peak energy consumption. This requires that users have to face the reality of real-time pricing and thus move away from the traditional “average annual cost” model based flat pricing. Electricity consumers have to adjust to prices and create elasticity by altering the demand, particularly over short time frames. For example, on a particular day, between 8PM-9PM the price from was 2.9 cents/kWh and 1.9 cents/kWh between 12 am - 1 am [1]. The Bangalore Electricity Supply Company (BESCOM) in the state of Karnataka, India, is perhaps one of the earlier utility companies to recognize the need for enabling DSM in its power distribution network to manage the peak energy consumption. BESCOM services extend to about 30% of the state’s 60 million population and serves 8 districts out of the 30 districts with 3 zones to administer. The domestic users are offered flat pricing with 3 or more slabs. One of the tariff categories from BESCOM is the Time of Day (TOD) pricing for Low Tension supply users. There can be an increase or decrease in pricing from the normal price between 06-00 Hrs and 22-00 Hrs. Recent statistics indicate that the month of July 2013 observed a 1000MW shortage between 06-00 and 09-00 Hrs [2]. BESCOM has also launched “Happy Hours” for home users in the month of August 2013. The goal of this pilot project is to observe if consumers can bring down their consumption by 10% on average and by 15% during peak hours. It is now apparent that end users have to learn more about tariffs almost on a daily basis if they have to check their growing monthly bills. BESCOM will soon start collecting “Fuel Cost Adjustment” charge from end users to pass on the burden of real-time pricing. This will appear as a variable component in bills and is essentially short time scale changes in cost of energy generating fuels. Clearly utilities and customers have to work in tandem if peak demand and supply have to match in the long term. Figure 1: loads The big picture: Managing deferrable Fig 1 shows the big picture of a smart grid based home energy supply system. Power from the utility is supplied to a home through an energy meter that records the household consumption. Assume for the moment that the utility company makes available the pricing profile to the smart meter connected to the Home Area Network Gateway(HAN). The HAN is expected to have the knowledge about the possible list of electrical appliances and the time at which they can be turned on to support the utilities pricing profile. Although final decisions are made by humans in the loop, most smart energy meters are unable to interface successfully with smart grid based utilities. In this paper, we build a smart energy meter called “Joule Jotter”(JJ) that can interface well between domestic user and their utility companies. Apart from building the JJ, our contributions in this paper are: (a) SEP 2.0 implementation on the embedded Wi-Fi based JJ smart energy meter. (b) Seamless integration between the Internet and mobile phone operators (c) Seamless mapping between utilities and end users. TOD charging, happy hours and other models available from utilities are supported within pricing profiles. These are then used by end users to effectively manage their electrical appliances. 2. LITERATURE The importance of smart meters for users and utilities is brought out in work of [4] where the benefits to users include transparency in billing and information about energy consumption. For utilities it is a way to ensure real-time pricing and change in user behavior to reduce the peak demand. Most literature mention that energy consumption feedback is extremely important since it brings the end user into the loop. For instance, in [5] the authors describe an android smartphone application that provides feedback on energy consumption profile of several home appliances. Load disaggregation is required since a single energy meter is used. The value proposition comes because of comparison of energy consumption with peer user homes and consumer organizations. The data obtained from the energy meters is provided as a feedback to influence user’s behavior. The work in [6] stresses the need for energy meters with reduced usage barrier. User feedback is provided on a real-time basis at a device level and thus biggest energy guzzlers are easily identified. A load disaggregation algorithm from Markus et al [7] propose a disaggregation algorithm called “AppliSense” that breaks down the energy consumption to a device level. Prior to the SEP 2.0, there were several works that proposed middleware frameworks. The authors in [8] propose a middleware framework called “Hydra” that facilitates intelligent communication through a P2P network. Smart energy plugs called “Ploggs” were used to gather energy usage statistics from electrical loads. However, the proposed architecture does not integrate utility providers and end users. GSM Automatic Power Meter Reading System (GAPMR), a prepaid payment based system is proposed in [9]. The number of units consumed is communicated to utility companies with help of GSM to monitor power theft. Manisa et al [10] have performed a thorough analysis of the load profiles of typical house-hold appliances and have suggested that while electric clothes dryers and water heaters provide the highest DR opportunity and clothes washers, refrigerators and electric range ovens offer the least potential. Field trial in 50 households by Smartcity M´ alaga [11] studies the effect of energy monitoring. It is found that 42% of the participants have achieved over 10% consumption reduction, 33% have seen minimal change (within 10%) and the remaining 25% have increased their consumption more than 10%. As stated earlier, this corresponds to the figures BESCOM is attempting to achieve. PEAKSAVE [12] has implemented a similar system using their smart meter named S Plug. It provides both monitoring and control functionalities. The work in nPlug [13], shows that it is possible to reduce peak energy demand for utilities by formulating Demand Side Management (DSM) strategies and schedule high power consuming appliances. nPlug, a inexpensive smart plug, runs a decentralized DSM strategy by assessing supply-demand gap. Users are expected to physically key-in their preferences indicating the starting and end timings to schedule their appliances. The JJ on the other hand provides users feedback about their consumption aligned to the pricing profile of the utility provider. Thus there is a seamless interaction between utility providers, home users, Internet cloud and the mobile networks. 3. PROTOCOL INTEGRATION: SEP 2.0 WITH INTERNET AND MOBILE NETWORKS Our hardware comprising of the JJ and HAN together ensure that all protocols are integrated and run in a seamless manner. The SEP 2.0 standard [3] supports several resources such as subscription and notification, end device and response. The SEP 2.0 supports the RESTful architecture. Such an architecture does not differentiate between a client and server in terms of resource representation, both in terms of resource exposure and interaction. SEP 2.0 is built around the concept of resources and function sets. Re- sources can be described to be the properties of a physical meter. A set of resources when used together to implement a specific function make a function set. Function sets such as metering, demand response and load control (DRLC) and pricing provide the seamless communication between utilities and home user smart meters. The load control is enforced using the DRLC protocol using the publish-subscribe resource available under SEP 2.0. Here, the load side JJ is the DRLC client that runs the subscription server and the HAN is the DRLC server that publishes resources and sends notifications. The JJs are also equipped with actuators to enable turning off the loads. Figure 3: Joule Jotter Figure 2: Overview of System Implementation The SEP 2.0, although available on hardware (for instance CC2538) platforms, we chose to implement the standard on Wi-Fi. The idea is to support scalable architectures ranging from single homes to multiuser dwellings. Fig 2 shows the overall protocol integration in our implemented system. The outermost ring has the communication protocols to end user and utility provider. The second ring exposes the user to the SEP 2.0 implementation. For example, the control of loads and metering information is available to the user as a simplified service. These work closely with the prepaid and post paid payment models to which the user might have subscribed. The SEP 2.0 implementation on JJ and HAN is shown in the third ring. Finally, the physical hardware is represented in the innermost circle. The HAN implements the pricing profile and directly interacts with the utility companies. It also has the SMS gateway capability. Thus the complete system facilitates integration of various services and payment models e.g. flat rate, TOD, happy hours, prepaid, postpaid etc. The end user can easily use these services via SMS, Email. In the event the user is at home, an android application running on the phone connects to the home network to manage the electrical appliances. 4. JOULE JOTTER: SMART ENERGY METER Fig. 3 shows a snapshot of JJ, the smart energy meter. The controller chosen is MSP430F5438A from Texas Instruments. It supports a single phase electronic energy meter sensor chip ADE7953 from Analog Devices that meters almost all electrical parameters such as current, voltage, power factor, etc. The current input is obtained from a current transformer (CT) and the voltage input is obtained from a step down potential transformer (PT). The JJ has a pro- vision for local storage of all metered data. Additionally, the board has support for TCP/IP communication protocol stack over a IEEE 802.11b/g Wi-Fi interface. The system clock frequency is 25 MHz with support for 16 bit timers. The system has support for SPI, UART and I2C modes. The ADE samples at a rate of 895 kHz. The Wi-Fi chip CC3000 operates over the 2.4GHz frequency range with +18dBm of maximum transmission power. We measured the current consumption of the JJ first during a write operation and then during a Wi-Fi transmission. We found that it requires average of 60mA and 170mA respectively. Figure 4: Wash cycle of a washing machine Fig. 4 shows the load profile for a washing machine. The system is rated for 545 watts. Power consumption data for four wash cycles were recorded by the JJ on its SD card. When water is pumped into the machine for soaking the clothes and rinsing at the end of washing, a power of 4 watts is required. A wash cycle and a spin dry cycle require significantly higher amounts of power. Often, the power drawn exceeds the rated power from the manufacturer; although only for a short interval of time. In the event of a power failure after the start of the program, the washing machine is able to “auto-restart” from wherever it stopped. This is just an example of all the loads for which we are able to record the power consumption in time. 4.1 Support for SEP 2.0 SEP 2.0 is the application level protocol that we have implemented to support all the algorithms. Our implementa- tion works on top of Wi-Fi and TCP/IP supported CC3000. The data is encapsulated as “XML” packets and transferred over HTTPS. The application protocol was developed to run on the MSP430 microcontroller. The CC3000 is accessed by the controller through API’s(application programming interfaces). The host issues API function calls to CC3000 and the module responds by performing the appropriate activity. Events are triggered by the CC3000 device as it issues interrupts to the host. Command response events are in response to commands issued by the host and unsolicited events are triggered asynchronously by the CC3000 device to indicate occurrence of a system event. 4.1.1 Pricing Profile SEP provides a very flexible and scalable structure for pricing profile implementation which the utility service provider issues. Each pricing profile itself is given by TariffProfile. Each TariffProfile will have a list of RateComponents. Each RateComponent specifies the type of user depending on the consumption rate. Since the pricing profile is a generic package which can be customized depending on the resource being metered, for electricity metering applications, RateComponent is measured in terms of kWh. Each rate component has a list of TimeTarifIntervals. For example, when a time-of-use tariff with rates varying for each hour is being used, the list will have a total of 24 TimeTariffIntervals (tti). Now, each of these tti can further have a list of ConsumptionTariffIntervals (cti). These again are split up depending on the energy consumed. The idea is that the price changes (increases) when the energy consumed increases. The cti can be used in case the tariff profile requires it, otherwise, we set the list to hold one object which has a price associated with it. 4.1.2 Demand Response Load Control(DRLC) Function Set sets a threshold for the power consumed by the load. On start of the event, the DRLC client will indicate the same to the server. If the threshold is exceeded, then the Subscription server notifies the client. The DRLC server exposes its EndDeviceControl object to the DRLC client indicating for the client load to be turned off. This implementation can be easily extended to multiple smart appliance scenario. The server can set thresholds for each of these appliances or for the entire system. The server is notified every time the threshold is exceeded to ensure that the condition is satisfied at all times. While this implementation is a general protocol, its elegant use mostly relies on control algorithms and mechanisms that exploit it. For example, client can switch on once the EndDeviceControl replies with a “yes” under conditions such as:(a) automatic increase in threshold, (b) Price tariff changes in time and (c) a time-out occurs. 4.1.3 5. In our implementation of DRLC, each smart appliance will serve as the DRLC client. The DRLC server is implemented on the HAN. The DRLC function set is supported by the SubscriptionNotification resource. Fig. 5 is a snap shot of our implementation. It shows that soon after the discovery procedure, the subscription client will first subscribe to the server’s metered resource. The subscription SCENARIOS FOR DEPLOYMENT Our protocol integrated architecture is exploited in several ways that demonstrate its scalability. In this section, we present three scenarios for our home energy monitoring system. Our implementation stresses on a highly flexible architecture which can be customized depending on user preferences and requirements. We look mostly at integrating the Internet and mobile network based protocols with the SEP 2.0 based existing infrastructure. The user is of paramount importance in our architecture. The complete user application was built over a smart phone as an android app. The basic requirement is that user should be able to respond to the requirements of the house with minimal inconvenience caused either due to physical location or any other restrictions. In the event the user is at home, direct HTTP communication is enabled. All deployment scenarios are capable of running simple algorithms. 5.1 Figure 5: DRLC with multiple clients Metering Function Set SEP’s metering function set requires implementation of the metering client on the HAN which regularly pulls the metered values from the metering server implemented on the JJ. The HAN also implements the pricing function set which receives the price tariff from the utility provider. As an example, the profile can be a TOD profile with consumption slabs; the prices being higher for a higher consumption slab. Since the HAN already knows the power utilization of the appliances from the metering function, the appropriate price for that overall consumption can be extracted. Subsequently, the DRLC function set can be used to switch off any of the appliances when the power utilization exceeds a certain set threshold on the HAN. This threshold can either be specified by the user or the utility provider. Scenario 1: Joule Jotter with DNS support In the first scenario, we assumed our user to have deployed one or two (a very small number) smart meters at home. The pricing profile along with DRLC runs directly on one of the JJs and is represented as home server in Fig. 6. The steps shown in Fig. 6 were implemented to control the appliances. To ensure that there is complete protocol integration, we subscribed to an online tool called SMS Global service; also shown in Fig.6. This service accepts HTTP connections from the home server JJ and delivers an SMS to end user. The SMS from the end user is forwarded to a play in our implementations and is part of the loop. The android app is built in such a way that the user can check the power consumption details in either energy units(kWh) or in terms of money. The algorithms interact with the user by providing options for the load(s) to be controlled. 6.1 Flat Rate Threshold Algorithm Uniform Resource Locator (URL). This URL is registered to the server JJ with a free dynamic domain name system (dynDNS) service. This scenario supports direct communication with the JJ and load control is possible either one-to-one or one-to-few. Assume that the utility offers a fixed rate pricing profile for the first 100 units consumed by the user. The HAN has the power profile of each appliance. In this implementation we set a threshold for the average power (including all appliances). Algorithm 1 will compute the total energy consumed in real time and ensure the average does not exceed the set threshold (3 units/ day). In the event of exceeding the threshold, the system presents the user with a choice of presently active appliances (single or a set of them) that can be turned off to optimally lower the consumption below the threshold. The appliance(s) that brings the power consumption below the threshold and closest is recommended to the user. The user selected option is used to control the appliance. 5.2 6.2 Figure 6: A protocol integrated architecture Scenario 2: HAN - JJs in star topology In this scenario, we have a HAN that runs the pricing profile and the SMS gateway service shown in Fig. 6 as the home server. It is however still possible to use external SMS service with the HAN registered with the DynDNS. This scenario is envisaged for multi dwelling units and large homes where several smart meters are required for plugged loads. 6. EVALUATION AND RESULTS Algorithm 1 Flat Rate Threshold T Ep ← T otal energy consumed till now T h ← T hreshold energy JJArray ← Array of active appliances JJT empArray ← T emporary array Ep ← Energy of an appliance in JJArray Ensure: T Ep ≤ T h if T Ep > T h then for i = 0; i < sizeof (JJarray) − 1; i + + do if (T Ep − JJArray[i]− > Ep) < T h then JJT empArray[k] = JJArray[i] k++ end if end for if JJT empArray 6= Φ then sort(JJTempArray wrt energy value) end if Energies of two or more devices are added and compared with TEp The group of devices which crosses threshold are sorted inJJTempArray send the JJTempArray to user and control the appliance(s) based on his feedback end if To demonstrate that our integrated approach has the necessary freedom to adjust the JJ to upcoming business models, we implemented three control algorithms. We now describe them in detail. The user has an interactive role to Happy Hours The “Happy Hours” algorithm is also utility provider driven and provides an option to users to reschedule their appliances. The algorithm computes the tariff a user incurs in happy hours compared to time outside these hours. Algorithm 2 shows our implementation. Algorithm 2 Happy Hour Pricing C[i] ← Rate f or ith consumption interval n ← Span of device operation h ← Happy hour consumption interval E[k] ← Energy consumption in kth interval k ∈ (1, n) JJArray ← Array of active appliances JJT empArray ← T emporary array Cwoh ← M oney spent at current time Ch ← M oney spent in happy hours Cmin ← M in. money f or user to consider rescheduling JJT empArray = JJArray sort (JJTempArray wrt Energy) n,i+n P Cwoh = E[k] ∗ C[t] Ch = k=1,t=i n,h+n P E[k] ∗ C[t] k=1,t=h if Ch − Cwoh > Cmin then send user notification to schedule the appliances end if if user rejects then Repeat the algorithm for next element in JJTempArray end if 6.3 Pre-Paid Accounts In this algorithm user can top-up his account for any amount and the home monitoring system keeps track of his balance. Algorithm 3 shows that the pricing profile supported by SEP 2.0 is amenable for this support. Once the time tariff interval is recognized based on time of the day, the energy consumed is compared with the consumption slabs for that time interval and the appropriate price is extracted. Table 1 shows the results of our SEP 2.0 stack evaluation. The table shows the average delay with and without the SEP 2.0 stack. As can be seen, E-mail takes a 1 sec more with the protocol integrated stack. With SMS running on the HAN, the system takes a little over 1 s with the integration. The SMS Global solution resulted in an average delay of 48 minutes from the user to the home. Algorithm 3 Pre-Paid Tariff C[i] ← P rice f or ith consumption interval S[i] ← Start value f or ith consumption interval T Ep ← T otal energy consumed till now T c ← Consumpstion cost of appliance T h ← T hreshold balance BU pdate ← U pdated balance Ensure: BU pdate > T h for i=(noOfConsumptionTariffInervals-1);i>=0;i– do if T Ep > S[i] then S[i + 1] = T Ep for (j = i; j ≥ 0; j − −) do T emp = T emp + C[j] ∗ (S[j + 1] − S[j]) T c = T emp end for end if end for BU pdate = BU pdate − T c if BU pdate < T h then Send warning to user phone end if Table 1: Latency Email (custom) JJ to user 5.98 user to JJ – 7. Measurements (secs) Email SMS SMS (SEP) (custom) (SEP) 6.9 24.63 26 – 13.76 15 DISCUSSION The protocol integration has resulted in seamless and scalable solutions for home and multi dwelling units. Unlike the hardware version of ZigBee SEP 2.0, our software implementation of the stack yielded elegant and simple scenarios. For example, our experiments with the SMS Global service, although requires to improve the time guarantees, it provided insights that a smart energy meter is now manageable from anywhere in the world. The algorithms have shown that adding variants is easy. For example, the average power threshold could be replaced with peak power. The TOD can be replaced with happy hours. The pre-paid algorithm can be tuned to provide daily alerts for the post-paid scenario. The algorithm complexity of the flat rate algorithm is N + N logN , and that for happy hours is N logN followed by pre-paid tariff algorithm being n2 . Here, N is the number of JJ’s and n is the number of consumption tariff intervals(cti’s). 8. CONCLUSIONS In this paper, we built a smart energy meter called Joule Jotter from scratch and implemented Smart Energy Profile 2.0 in software over Wi-Fi. The integration with mobile networks and Internet has yielded many deployment options and seamless interaction between utilities and the end user. Existing algorithms running on smart meters use the philosophy “pay more use more”. The JJ makes a paradigm shift by aligning the power consumption to utility requests. We believe, quite like water consumption, energy consumption should be based on global optimization algorithms. 9. ACKNOWLEDGMENTS We thank ACM SIGCOMM - Community Grant for generously funding this IoT device, RBBCCPS, IISc for the seed funding and our partner TUDelft who have stood by us. 10. REFERENCES [1] “Ameran Illinois official website” Available: http://www.powersmartpricing.org/ [2] “BESCOM official website” Available: http://bescom.org/en/dsm-activities-in-bescom-2/ [3] ZigBee Alliance, Inc. and HomePlug Powerline Alliance, Inc. Smart Energy Profile 2: Application Protocol Standard, 13-0200-00, April 2013. [4] Jixuan Zheng, Li Lin, et al. Smart Meters in Smart Grid: An Overview. In 2013 IEEE Green Technologies Conference, pages 57-64 , Denver, CO , 4-5 April 2013. [5] Markus Weiss, Friedemann Mattern, et al. PowerPedia: changing energy usage with the help of a community-based smartphone application. Personal and Ubiquitous Computing, August 2012. [6] Markus Weiss, Friedemann Mattern, et al. Handy feedback: Connecting smart meters with mobile phones. Proceedings of the 8th International Conference on Mobile and Ubiquitous Multimedia, Cambridge, UK, November 22-25, 2009, ACM. [7] Markus Weiss, Adrian Helfenstein, et al. Leveraging smart meter data to recognize home appliances. IEEE International Conference on Pervasive Computing and Comm., pages 190-197, Lugano, 19-23 March 2012. [8] Marco Jahn, Marc Jentsch, et al. The Energy Aware Smart Home 5th International IEEE Conference on Future Information Technology, Busan, May 2010). [9] Rohit Nargotra, Ritula Thakur, et al. Design of a Prepaid Power Meter with Communication facility based on GSM Network International Journal of Scientific and Engineering Research, Jan 2013). [10] Manisa Pipattanasomporn, MuratKuzlu, et al. Load Profiles of Selected Major Household Appliances and Their Demand Response Opportunities. IEEE Transactions on Smart Grid, 07 August 2013. [11] Jaime Caffarel, Igor G´ omez, et al. Lessons Learned on Home Energy Monitoring and Management: Smartcity M´ alaga. Proceedings of the fourth international conference on Future energy systems, pages 263-264, ACM NY, USA, January 2013 [12] Jeonghoon Kang, Jaechul Kim, et al. PEAKSAVE: Energy Monitoring Service. Proceedings of the 10th ACM Conference on Embedded Network Sensor Systems, pages 367-368, NY, USA, November 2012 [13] Tanuja Ganu, Deva P. Seetharam, et al. nPlug: A Smart Plug for Alleviating Peak Loads. e-Energy ’12 Proceedings of the 3rd International Conference on Future Energy Systems, ACM NY, USA, May 2012
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