Smart Grid technologies promise a major overhaul of the aging energy infrastructure. With the addition of alternate, sustainable energy sources to smart meters in homes and businesses, changes are sure to come fast and furious. And one of the more critical aspects of the Smart Grid is the emergence of electric vehicles (EVs) and plug-in hybrid vehicles (PHEVs).
These mobile loads and potential energy sources will have to tap into the Smart Grid, but not necessarily at the same location on a daily basis. Imagine several EV owners gathering at a meeting or a party, and during this time they want to charge their vehicles. The impact on the local transformer could be quite significant. As a result, EVs and PHEVs need to connect and communicate for an effective Smart Grid. For that to happen, standards must fall into place and technologies need to advance.
The success of EVs and PHEVs, collectively called plug-in electric vehicles (PEVs), depends heavily on an effective charging infrastructure. For example, GM has deployed three EVs into outer space, said Tony Posawatz, vehicle line director for the Chevrolet Volt and global electric vehicle development at General Motors during his presentation at the Plug-in 2009 Conference and Exposition last August in Long Beach, Calif. In fact, the Apollo 17 vehicle achieved 22 miles of “real world” EV range. But the program was scrapped due to the lack of a recharging infrastructure on the moon.
READY OR NOT, HERE COME PEVs
While 2010 marks just the beginning of OEM introductions of PEVs in the 21st century in the U.S., the federal government wants to have as many as 1 million EVs and PHEVs on the road by 2015. However, an EV’s requirements for energy could increase a household’s electricity consumption up to 50% or even more.
The Electrification Coalition, a not-for-profit group of business leaders promoting the deployment of EVs, created a 91-page report called the “Electrification Roadmap.” The report envisions that by 2040, 75% of light-duty vehicle miles traveled in the U.S. should be electric miles. To avoid problems down the road, utilities and carmakers are assessing the potential impact of these vehicles on the infrastructure.
An unlikely combination before this decade, utility and automotive companies now frequently share the stage at industry events such as the SAE 2010 World Congress, held April 13-15 in Detroit, Mich. Oliver Hazimeh, director and head of the Global e-Mobility Practice at PRTM, a management consulting firm, organized and chaired a panel titled “Smart Grid Technology: Are Electric Vehicles Part of the Problem or Part of the Solution?”
“In terms of just the barriers that still need to be overcome, clearly there is enough that needs to be happening around the infrastructure, battery costs and educating the customers, actually integrating the whole thing across the ecosystem,” he says. “Those are formidable challenges still ahead.”
THE PERVASIVE NEED FOR STANDARDS
Standards represent a critical first step toward interoperability and seamless integration of PEVs onto the grid. Several standards organizations are working to develop specifications for the Smart Grid, including the SAE for automotive-related standards.
The National Institute of Standards and Technology (NIST) is championing and directing the consolidation of all standards activity. Its NIST Framework and Roadmap for Smart Grid Interoperability Standards, Release 1.0, dated January 2010, identifies eight priorities to implement an effective Smart Grid:
• Demand response and consumer energy efficiency
• Wide-area situational awareness
• Energy storage
• Electric transportation
• Advanced metering infrastructure
• Distribution grid management
• Cyber security
• Network communications
Based on the impact of vehicle charging loads, at least three of these priorities integrally involve vehicles. The SAE has several specifications in the works that specifically target automotive requirements. In addition to the recently approved J1772-SAE Electric Vehicle and Plug In Hybrid SAE Electric Vehicle and Plug In Hybrid Electric Vehicle Conductive Charge Coupler, there are:
• J2293/1 & /2: Energy Transfer System for Electric Vehicles
• Part 1: Functional Requirements and System Architectures
• Part 2: Communication Requirements and Network Architecture as well as new SAE documents:
• J2836: Use Cases & General Information
• J2847: Detailed information (messages, state diagrams, etc.)
The connector specified in J1772 (Fig. 1) will be on the Chevrolet Volt and the Nissan Leaf to be introduced at year’s end. Initially, two ac levels are defined for onboard chargers, but work is underway for higher-voltage, fast-rate dc charging (see the table). Unlike the 1990s battle of conductive versus inductive charging for EVs, the present specification only defines conductive charging and is supported by GM, Chrysler, Ford, Toyota, Honda, Nissan, and Tesla Motors.
Still in development, J2847 has five segments. According to George Bellino, staff project engineer at GM, the /1 segment identifies the message structure for electric vehicle communications to the grid. The /2 segment addresses the communications between off-board dc chargers that will provide higher-level charging for significantly reduced charging times. Segments not yet started include the /3 for vehicle-to-grid communications, /4 for diagnostics for the system, and /5 for active load management. The /5 defines a higher level of messages for future vehicle-to-grid interaction.
From the utility side, ZigBee wireless communications is a leading frontrunner for connecting to the automated metering infrastructure (AMI). Carmakers have determined that some environments might require powerline communications (PLC) for improved reliability. Also gaining traction is HomePlug, a PLC solution for home AMI applications.
The ZigBee Alliance and HomePlug Powerline Alliance members working with utilities, regulators, suppliers, and technology providers developed the ZigBee/HomePlug Smart Energy profile. NIST accepted it as an initial interoperable standard for the Smart Grid in 2009.
Recently, the Smart Energy Version 2.0 Technical Requirements Document was announced and made available for public comment. With Smart Energy 2.0, an application layer standard was established rather than a specific protocol. This allows the rest of the stack—all other communications aspects—to be protocol-independent.
With a common communication technique through Smart Energy 2.0, wireless, PLC, Ethernet, or Wi-Fi can be used with a bridge for interconnecting. “It will be part of SAE J2836 and 2847 and on the utilities’ side, as a part of the IEC 61968, 61970 distribution management system and application program interfaces for energy management systems (EMS) specifications,” says GM’s Bellino.
CHARGING LOAD IMPACT ON THE GRID
EVs like the Nissan Leaf and plug-in hybrids or range-extended vehicles like the Chevrolet Volt have quite a different impact on a home and the local transformer. The typical full electric small sedan will have a battery in the 22- to 26-kWh range. Ford has a 24-kWh battery, as does the Nissan Leaf.
Depending on the location, the daily use of energy consumed in a home can differ from 30 kWh/day in Arizona to 20 kWh/day in the Detroit area. “If I drove 100 miles per day in my vehicle, my home and my car would draw about the same amount of power,” says Mike Tinskey, manager of Sustainability Activities at Ford Motor Company.
The power consumption of the EV varies across the country depending on the climate, and its impact on the home depends on the home’s energy requirements. According to Electric Power Research Institute (EPRI) data, average peak summer demand per household without an EV can range from 3.0 kW in San Francisco or 4.3 kW in Hartford, Conn., to 6.0 kW in South Bend, Ind., and even 7.7 kW in Springdale, Ark. (The data was presented at the SAE 2010 Hybrid Vehicle Technologies Symposium, Feb. 10-11, 2010, in San Diego.) This compares to a PEV load of 7.7 kW when charged at 240 V at 32 A, 3.6 kW when charged at 240 V at 15 A, or as little as 1.4 kW when charged at only 120 V at 12 A.
With electrical rates of about 10.5 to 11 cents per kilowatt-hour nationwide, “filling up” an EV costs about $1.80 for a battery that needs 18 kWh to recharge, since a 24-kWh battery is never fully discharged. “Even though they draw as much as a home, if you use the full battery capacity every day, the actual current could be much, much higher,” says Ford’s Tinskey.
Today’s typical EV chargers are rated at 3.3 kWh or at 6.6 kWh. Drawing 3.3 kW to replenish the 18 kWh in the battery would take about six or seven hours. “Where a house uses that much power over a 24-hour period, the vehicle could use that much power across a seven-hour period and potentially in a three-hour period if it’s using one of the larger chargers,” says Tinskey.
The problem at an individual residence quickly progresses to the local transformer. Mark Perry, director of Product Planning, Nissan North America, explains that EV customers tend to be clustered in the same neighborhoods. “We are already seeing it and we are sharing that information with our utility partners kind of at the zip-code plus four level,” he says.
With 110,000 consumers expressing interest in the Leaf, Nissan created a density map that shows where concentrations are developing. Utility companies are looking at the same levels of demographics, using their forecasting tools to identify the hot spots within their service areas. By sharing the information, the utilities can upgrade transformers on a block-by-block basis where concentrations first occur, rather than across their entire service area.
In contrast to an EV, a plug-in hybrid presents a much smaller load to the grid. “The Volt has an 8-kWh battery. At 240 V, it’s drawing about 15 A,” says Britta Gross, director of Global Energy Systems, GM. “A typical clothes dryer is drawing 30 to 40 A.”
Thus, a Volt is much different than a pure electric vehicle—and the difference is by intent. “We wanted to seamlessly blend into the grid. We did not want to introduce something that caused upstream issues with the grid,” says Gross. EPRI estimates that compared to the annual residential energy consumption of 12,231 kWh, the Chevy Volt will consume 1890 kWh.
The smaller battery is easy to charge at 120 and 240 V. Even with this much smaller charging load, utilities will have to monitor transformer loads. “That’s their business,” says Gross. “You upgrade for air conditioners. You upgrade for flatscreen TVs.” The PEV is just one more appliance.
What’s in place for the Smart Grid on the infrastructure side when the Chevy Volt and Nissan Leaf arrive later this year? “At this point, the straight answer is not much,” says Sunil Chhaya, senior manager for PHEV Development Programs at EPRI. “But I need to qualify that because the vehicles are going to be benign to get started with.” Even with annual vehicle sales in the 100,000-plus range, the impact on the total grid will be almost negligible.
In addition to the activities underway to establish future communications (Fig. 2) and security (see “Smart Grid Security”), initial PEVs will come with a dash and wireless (either PC or cellular) interface so consumers know off-peak rates. Armed with that knowledge, consumers can program the PEV in the car. Each automaker takes a different approach.
As an alternative to a fully functional Smart Grid, GM’s Gross says the Chevy Volt can take advantage of the built-in communications capability of OnStar. “With OnStar, we have the ability to get all kinds of information off a vehicle and all kinds of information on a vehicle,” Gross says.
Though OnStar (Fig. 3) isn’t the “do-it-all” desired by GM engineers, they have given lots of consideration to the kind of information they want to send to, and retrieve from, a PEV. The Volt offers GM an alternative to the longer-term potential of connecting a vehicle to the Smart Grid.
Even though GM may have substantial communication with the Volt through the OnStar capability, sharing communications and dialog with the grid and utility companies doesn’t appear likely this year. “But EPRI has an extensive program with General Motors extending both the capabilities on the OnStar side and also adding Smart Grid-specific technologies on the car,” says EPRI’s Chhaya, who is managing the project.
Ford recently announced that it will use Microsoft’s Hohm software so customers can connect to their local utility provider to understand and manage their home’s energy usage. The 2011 Focus Electric will be the first vehicle to use the software. The connectivity should also allow utility companies to better manage the added demands of EVs.
Based on the deployment status of smart meters at the nation’s 3100-plus utility providers, Ford’s Tinskey thinks the Microsoft solution is more than a short-term alternative for today’s Smart Grid. “We believe it’s a long-term solution,” he says.
Instead of communicating directly with smart meters, the approach establishes communication with the utilities’ servers. Since the utilities’ servers already communicate or will communicate with smart meters, the cloud-to-cloud solution avoids all of the diversity issues surrounding today’s smart meters.
The customer can set a timer onboard Nissan’s Leaf to take the best advantage of local utility rates or time-of-use (TOU) rates. “It triggers based on when you know those rates go into effect,” says Nissan’s Perry. This is similar to what people have been doing for other large-current-draw home appliances, such as heating and air-conditioning systems and pool filters. In addition, Leaf owners will be able to remotely control some loads on their vehicles and receive ample information through a cell phone or PC.
The Smart Grid plan for vehicles (Fig. 2 again, bottom) calls for a meter that communicates through a wireless technique, such as ZigBee. To communicate with the HomePlug transceiver in the vehicle, a PLC-ZigBee gateway, perhaps in the electric vehicle supply equipment (EVSE), will provide the bridge.
Any semiconductor technology that winds up on the vehicle must be automotive qualified. That could cause problems if the silicon wasn’t designed to meet the automotive temperature range and other unique automotive requirements that typically go well beyond consumer applications. “All of these manufacturers are a part of SAE J2847, so they are trying to understand the requirements and they are working in that direction. They understand that they need to develop an automotive-grade component,” says GM’s Bellino.
Thanks to all of the efforts being made today, the Smart Grid should strongly interact with the vehicle in perhaps five or 10 years. “I think it’s going to evolve and it’s going to be a smart evolution and features are going to be added one after the other,” says GM’s Gross. One future possibility is the use of PEV batteries to provide storage for the grid and return power under peak load conditions, to be called the Generation 3, or Gen3, Smart Grid.
PRTM’s Hazimeh thinks that many years of PEV experience are required before Gen3 will happen, though. The Nissan Leaf’s 24-kWh lithium-ion battery costs about $600 to $700 per kilowatt-hour, or about $15,000 to $17,000. “You don’t let someone come in and just manage the cycling, taking energy in and out, unless we have enough data to say what is really happening regarding the life of the battery,” says Hazimeh.
Overall, in the short term, the smart consumer charging in an intelligent manner will be a big part of the Smart Grid. “I think that even longer term, it is going to remain consumer-centric,” predicts EPRI’s Chhaya. The premise is that informed customers will make intelligent choices, especially once the rates change from uniform to graded. It will be in their best interest to select the time for charging based on the lowest rate whenever possible.
Therefore, the communication task of carmakers and utilities will be to keep their customers informed and continue working together toward a common energy-saving goal. As Ford’s Tinskey concluded his presentation at Plug-in 2009, “Once our customers begin to make the leap into plug-in vehicles, success of electrification will become a team sport.”