By Paul G. Blystone, Sunnyvale, California, USA

Coal and natural gas power plants and oil-based transportation emissions are main contributors to man-made CO₂ levels in the earth's atmosphere. In February 2007, I wrote an article published in Celsias entitled "The Coming Energy Shift" that focused on scenarios for reducing transportation emissions. The main takeaways from the article were:

1. Battery powered electricity-to-wheels technologies will begin to lower transportation petroleum usage, shifting fuel emissions to power plant emissions as plug-in cars become numerous.
2. If plug-in vehicles become numerous, grid reliability becomes even more important to satisfy increased demand for home and transportation needs.
3. Vehicle battery recharging from renewable energy sources combined with non-food based bio-fuels could begin to reduce man-made CO₂ emissions within 5-10 years.

 + 

 = Lower Man-Made CO₂ Emissions

Nearly 18 months have passed since that article. With oil prices reaching record levels, an update to the original article is warranted. In addition, I will provide interested readers with a home solar photo-voltaic guideline for plug-in vehicle battery recharging using real-world energy consumption data. Even without the use of solar energy, purchasers of plug-in hybrid vehicles in the year 2010 can expect to lower gasoline consumption by 42% vs. today's non plug-in hybrids. While all-electric vehicles will be more expensive than their internal combustion engine counterparts in the near term, owners can expect operating electricity costs for the vehicle to be approximately 84% less than gasoline costs.

March of Electrons

For electrons to displace petroleum in significant quantities there must be continued advancements in batteries as well as affordable plug-in cars for the masses. For these same electrons to offset significant man-made atmospheric CO₂ emissions there will need to be readily available renewable energy for battery recharging. In the last 18 months there has been slow but steady progress on each of these fronts. Although slower than many might wish for, all change begins with first steps.

Battery Update

The key to widespread electron usage in transportation is safe, robust batteries. Important battery parameters include: power (necessary for vehicle speed, heavy loads or inclined driving), energy density (necessary for greater distance), energy discharge profile (determines battery drawdown limits while driving), energy recharge cycle (determines the recharge time and the number of total lifetime cycles), and safety. Battery cost is another important criterion; for example, the Tesla Roadster contains nearly $30,000 in battery costs alone.

Although lithium based batteries dominate the press, improvements have been made on other battery chemistry schemes as well, such as lead-acid, nickel, metal-air, and polymers. For Toyota Prius owners, plug-in conversion kits are available today using nickel, lead, or lithium based batteries.

Below are some of the advancements made in the past 18 months.

• Power: Perhaps the best commercial advancements of power have been made by A123 Systems, EnerDel and Altairnano. Think of power as the rate at which electrons can be discharged for work; the faster the electron flow, the greater the power. A123 Systems and MIT have produced a nano-phosphate lithium battery with higher power than previous products. It is used for cordless power tool high torque applications, as well as for electrified vehicles. This flux of energy was recently demonstrated in sensational fashion when Bill Dube shattered drag racing records on his all-electric motorcycle using A123 Systems batteries. The bike went from 0-60 miles per hour in under 1 second, and passed a quarter mile at 168 miles per hour in 7.824 seconds. 
• Energy Density: Think of energy density as the total number of electrons available in the battery for work. This is different from energy power. If you doubled energy density, you would double the length of time that notebook computers could run before recharging. Improved energy density is what will increase the total miles that plug-in cars can drive before needing a recharge. Recently, researchers have demonstrated improved battery density using anode doping with nano-materials. There is a good chance that this and other developments will result in a doubling of energy density in vehicle batteries in the next 4-8 years.
• Safety: Highly publicized notebook computer lithium battery fires have caused understandable concern for consumers and design engineers. High energy storage is inherently a potential hazard, much like that which exists with your vehicle gasoline tank. Internal safety devices can greatly reduce the chance of battery explosion or fire. Using cathode materials less sensitive to temperature is another approach to safety. The author is now convinced that the safety advancements being made in automotive batteries will render them as safe as or safer than your current gasoline tank.

The author foresees realistic and achievable improvements in battery technology in the coming years. Since 1991, Lithium ion density has improved 6-8% per year without any dramatic technology advances. In the future we should expect more fundamental battery energy density improvements. Cost still remains an issue for automobile applications. While battery commodity curve price reductions have occurred in portable consumer devices such as mobile phones and iPods, this has not yet translated to automotive applications. However, two factors will likely bring these prices down. The first is the purchasing power and efficiency of the auto industry supply chain, as was demonstrated in the historical adoption of antilock brakes, air bags, electronic fuel injection, etc. The second is the likely positive outcome from heavy investments taking place in battery energy density R&D.

Plug-in Vehicle Availability Update

At the time of the first article the Toyota Prius was already demonstrating the use of battery electrons to displace petroleum, although it was not then and still is not a plug-in car. Toyota has now sold over 1 million Prius cars and introduced hybrid options on many other models such as the Camry. Edmunds.com lists 19 hybrid vehicles available to the public in 2008, such as Toyota's Lexus, Highlander, and Camry, Honda's Civic, Nissan's Altima, Saturn's Aura, Ford's Escape, Mercury's Mariner, Chevy's Malibu, and Mazda's Tribute.

Today, many automobile manufacturers have plug-in models in the production pipeline. While the Chevy Volt and Toyota Prius dominate the headlines with their plans for a year 2010 rollout, others are also in the mix, such as Mercedes-Benz, Nissan, VW, Mitsubishi, and upstarts Tesla Motors and Fisker. In all likelihood, steady incremental improvements will advance the safety, robustness, and ubiquity of automobile battery technology. In 2010, plug-in vehicle availability should mark the beginning of much greater displacement of combusted liquid gasoline through battery use. But it will take 10-15 years before the current fleet of worldwide vehicles is significantly converted.

Renewable Energy Availability Update

In order to truly reduce man-made CO₂ emissions, countries will need to reduce fossil fuel consumption in both electrical generation and transportation sectors, or learn to sequester those emissions. The premise of this article is the belief that an energy shift is just beginning to occur whereby transportation energy from oil will begin to be replaced with electrons from power plants (with additional contribution from bio-fuel blending). When this happens in significant quantities world-wide electrical generation will need to be increased in proportion.

It can be argued that trading oil tail-pipe emissions for power plant emissions alone will result in a net reduction of CO₂ emissions. However, a much greater reduction can be achieved through the use of renewable energy. Available renewable sources and grid tie-in for various geographies will determine how well this goal can be met. Sources include hydropower, geothermal, wind, solar thermal, solar PV, biomass energy, and various wave/ocean schemes.

NOTE: Nuclear energy is generally not considered to be a renewable energy resource due to the need for "mined" fuels such as uranium. The author also makes no attempt to categorize or predict the prospects of CO₂ capture schemes, such as that advocated by "clean coal" proponents.

In 2006, the total share of global electricity from new renewable sources was 3.4% (pdf) excluding large hydro, or 18.4% including large hydro. While small in comparison to fossil fuel sources such as coal and natural gas, growth and investment trends for renewable energy are strongly in an upward direction (Source: REN21 Renewable 2007 Global Status Report).

Growth in Global Renewable Energy Investments

According to Eric Martinot, lead author for The REN21 Renewables 2007 Global Status Report, "an estimated US$71 billion was invested globally in new renewable power and heating capacity in 2007 (excluding large hydropower), of which 47% was for wind power and 30% for solar PV. Countries with the largest amounts of new capacity investment were Germany, China, United States, Spain, Japan, and India". An extreme example is Iceland. With its abundance of hydroelectric and geothermal energy, Iceland generates 99.9% of its electricity from renewable sources. According to a report from the UN's Environmental Programme (UNEP), clean energy represented 23% of all new installed capacity in 2007.

Of course, renewable energy will only begin to significantly replace fossil fuels when it can achieve base-load consistency. That requires technologies that can deliver energy during times when the sun is not shining and the wind is not blowing. Energy for homes, buildings and transportation needs to be stable and consistent. The chart below shows the relative role of renewable energy consumption versus other sources in the U.S. in 2006.

The Role of Renewable Energy Consumption in the U.S. Energy Supply, 2006

If there is to be a true energy shift as I describe, the 40% petroleum area shown above (predominantly used for transportation) would decline in favor of growing electricity from coal, natural gas, nuclear and renewable energy. For renewable sources to gain a significant share of this growth in electricity, they will need to demonstrate reliable and consistent base-load contributions.

The author believes electrical energy for plug-in vehicle use can be met from five sources:

1. Tapping night-time spare capacity from new and existing power plants
2. Increased power generation from utility scale renewable resources
3. Increased power generation from natural gas power plants
4. Reduced home and building energy consumption through efficiency gains
5. Increased power from local sources such as rooftop solar

Tapping night-time spare capacity

Many studies have concluded that a significant percentage of electrical energy for transportation is already available at existing power plants, because there is a great surplus of unutilized electricity during the nighttime hours when many vehicle batteries would be "plugged in" for recharging. A statement by the American Electric Power Co. indicates the nation's current grid could withstand an immediate turnover of at least 20% of the nation's vehicle fleet to plug-in technology. One optimistic study finds that "off-peak" electricity production and transmission capacity could fuel 70% of the U.S. current fleet of 220 million vehicles if they were plug-in hybrids. If this were to happen to any large extent, the term "off-peak" would become a misnomer. Such a huge shift could cut U.S. oil consumption by 6.2 million barrels a day; eliminating 52% of current U.S. imported oil. A shift of this magnitude would also have profound global trade and security implications.

Increased power generation from utility-scale renewable resources

The following areas show good potential for increasing the total energy output from renewable sources within a 10-15 year timeframe:

• Utility scale Solar thermal electrical power generation with energy storage schemes
• Expanding the number of high and low temperature geothermal power plants
• Utility scale solar PV and wind combined with storage schemes
• Closed loop hydroelectric plants with pumped storage schemes from renewable power
• Power generation from waste biomass gasification (gasification/pyrolysis/plasma)
• Blending biomass with coal (pdf) at existing coal fired power plants

There are obvious geographical constraints for each power scheme, meaning solar works best in sunny locations, wind in windy locations, geothermal where the geology allows it, pumped storage where there are changes in elevation or existing dams, biomass co-firing where there is available biomass near coal power plants, and gasification formulas based on regional available biomass stocks^(a,b,c,d). Because of regional variability, a blending of all options with a smart grid sharing infrastructure would seem the most appropriate path to take.

Increased power generation from natural gas power plants

There are good reasons to buffer the above renewable sources with on-demand available base-load power. In the U.S., a careful array of newer combined cycle natural gas power plants would be a prudent hedge against any shortfalls from the renewable sector as the demand for electrical energy for transportation increases. It also provides a means to "smooth out" sporadic energy production curves from renewable solar and wind sources without storage schemes. While natural gas is more efficient and less polluting than coal fired power plants, burning any fossil fuel still adds to man-made CO₂ emissions. This is perhaps the strongest argument for using nuclear power in careful measure, although in the U.S. this is highly unlikely in today's economic and political climate. Other countries would have to make similar choices.

Reduced home and building energy consumption through efficiency gains

The easiest and most cost effective way to reserve electricity for transportation is to reduce use in buildings and homes. This can be done with no discernable change in quality of life for industrialized nations, and would go a long way to improve the quality of life in under-developed nations. In the U.S., local governments are taking the lead in setting energy efficiency policies for new homes and buildings. As an example, progressive energy efficiency standards and policies by the California Energy Commission have reduced 12 GW from the State's annual peak demand. The cost of these avoided kilowatt hours was about one-fifth the cost of electricity generated from new nuclear, coal and natural gas-fired plants.

But much more can be done. Homes and buildings can utilize geothermal heat pumps that use the constant temperature of the earth as the heating/cooling exchange medium instead of outside air temperature (where applicable). Promoting passive solar for daytime lighting, and assisting space and hot water heating makes complete sense for building codes. Readers are encouraged to review all the benefits that energy efficiency can provide at the Rocky Mountain Institute and LEED web sites.

Increased power production from local sources such as rooftop solar

There continues to be a growing build-out of point-of-use power generation, mainly from solar PV. A growing number of individual companies and home owners have already installed mini-power generation PV and wind schemes. Much of this local power will find its way to transportation use.

The largest market deterrent to greater local power growth is the relatively poor return on investment (ROI). Rooftop solar ROI varies greatly depending on local solar irradiation, utility rates and rebate availability. Paybacks typically fall between 8 to 30 years. This is a rather unattractive ROI for most home/building owners. But when electricity is used for transportation in lieu of building/home use, the ROI can be significantly improved. This will be demonstrated later in this article.

It is plausible that a combination of the above five areas will provide the necessary electrical power to facilitate a large penetration of plug-in vehicles.

Grid Update

The transportation energy shift will require more electricity from wall outlets. However, a large factor to be considered is outlet availability. Many drivers do not have access to a wall outlet where they park. Consider apartment dwellers as an example. Even when available, the plug-in concept for the masses requires a convenient procedure that should include standardized wall outlets, auto inlets, and electrical cords between them. The wall outlet circuit also needs to have available amperage to handle the increased load. The author foresees the need to secure outside electrical outlets. Gasoline thievery has risen along with gasoline prices. Those same thieves will certainly try to tap available outdoor electrical outlets for plug-ins, each of them a potential mini-fuel pump. These are not trivial matters. It is hoped that automobile and electric hardware manufacturers and utilities can solve many of these issues so that your vehicle can safely plug in wherever you might be.

Depending on the number of battery miles driven, those with available home outlets could see increased home electricity usage of at least 30-40 %, a staggering projection for which utilities must plan. For early adopters of plug-in cars, the energy can easily come from night-time excess capacity already discussed. But daytime recharging (when demand is high) would force utilities to generate or purchase more electricity. Some regions of the world could handle this, while for other regions it will be more difficult.

It is likely that multiple and shifting energy sources will require an electrical grid delivery system with greater capacity, flexibility and reliability. In the near term, utilities are planning to encourage off-peak vehicle recharging through the use of smart-meters and variable rate plans, as pointed out in this Wall Street Journal article. However, given today's current infrastructure, grid tie-in and energy balance management issues pose limitations on the growth of widespread renewable energy production, distribution and use by businesses, homes and vehicles.

Another critical issue facing the management of large grid networks is power flux "vibration" caused by intermittent energy from solar and wind sources. Utilities in the U.S. are currently rushing to meet renewable energy goals set by local governments. Much of the energy to meet these goals will come from intermittent sources. Without smart grid management systems in place, there will be a growing need to place energy storage requirements on solar and wind farms, a move that will increase capital and operating costs. Large scale industrial batteries, thermal storage, compressed air, and pumped hydro are all possible technologies for energy smoothing storage, but all suffer from a lack of R&D funding.

The author believes that improving grid infrastructure and reliability is an area that needs much greater emphasis. Large investments in the grid are clearly going to have to be a significant part of any country's future energy plans.

Plug-in Vehicle Owner Electric Bills: What to expect

In the U.S., advanced car batteries will plug into standard wall outlets for recharging (110 or 220 Volt). Since plug-in vehicles are not yet commercially available to the masses, recharge energy consumption data could only be obtained from older RAV-4 EV, GM EV-1, and plug-in converted vehicles. These early numbers are the best data we have to gauge future electricity demands from plug-in vehicles. Through published and personal correspondence, the author obtained wall outlet-to-wheels consumption data from a variety of plug-in vehicle owners. The sampling of vehicles was divided into two groups: converted plug-in hybrid Prius' and all electric vehicles.

Google operates the largest fleet of after market, plug-in Prius' through their RechargeIT project. The Google team has done a masterful job of logging data for these vehicles, as well as others for comparison. For our purposes, I have concentrated on just the Prius plug-in conversions.

Obtaining electrical consumption data for the plug-in Prius is complicated by the fact that the vehicle uses both gasoline and battery power, sometimes at the same time. Fortunately, Google has provided the breakdown of gasoline and electricity usage driven in various conditions. Taking these numbers, the author has projected the monthly energy costs (gasoline + electricity) for a current Prius version vs. a converted Prius plug-in. The consumption numbers for 1,000 miles/month of combined driving conditions (highway and city) are shown below using a California average gasoline cost of $4.52 per gallon as of July 14, 2008 and a California average electricity cost of $0.148 per kWh:

The monthly combined fuel cost for a plug-in Prius was 26% less than the current non-plug-in Prius hybrid. From this analysis, it is clear that adding wall powered batteries lowers overall fuel cost, as $45.10 worth of gasoline/month was displaced with only $20.70 of electricity. If that electricity were to come from renewable sources, it would represent a 48% decrease in the vehicle's fossil fuel CO₂ emissions (20.7 gallons vs. 10.7 gallons).

The second group of plug-ins investigated was all-electric cars. Electrical energy use for these vehicles is expressed in terms of watt hour per mile driven (Wh/mile). A summary of collected wall outlet to wheels data is shown in the table below:

While the sample size is small, the data does confirm common sense assumptions about plug-in vehicles. For instance, even using older lead-acid batteries, the light weight GM EV-1 used fewer wall outlet electrons than heavier vehicles like the RAV-4 EV. As expected, converting a heavier vehicle like the Volvo car would need far more wall outlet power per mile than lighter designed models.

The Wh/mile figures above were derived from actual measurements taken at wall outlets. Note that all plug-in wall outlet numbers will always be higher than what are actually discharged while driving the vehicle, because the recharging process is not 100% efficient. The battery charger and the battery circuit all yield energy losses due to internal resistance. These losses are defined by the I²R law of electricity whereby the square of the current is multiplied by the resistance of the entire electrical circuit from the wall outlet to a fully charged battery, such as the charger, inverter, cables, anode, cathode, battery chemicals, etc. For instance, Tesla's fast 220 volt lithium battery recharging is approximately 75% efficient, while the slower 110 volt lithium battery recharging used by Google's Prius plug-in fleet is about 90%. Even so, the least efficient vehicle still had cheaper electricity costs per mile than equivalent gasoline usage, as shown below. Plus, EVs have 10 times fewer moving parts than an ICE vehicle, which will likely result in fewer component failures.

*  Based on $0.102/kWhr average US electricity rate, not including battery maintenance costs

** Based on 20 MPG and $4/gallon fuel costs, not including engine maintenance costs

Today's available hybrid cars from major automobile manufacturers do not plug into the grid. As a result, their operating cost advantage from the batteries does not offset the purchase price difference that batteries add without government incentives. However, as the above numbers would suggest, newer fully integrated plug-in vehicles with advanced battery technology (and longer battery life cycles) will make much greater economic sense than today's non plug-in hybrids, as the payback timeframe for improved battery technology will be much shorter.

Personal Power

The earlier article predicted that a significant portion of the increased electron demand from transportation will come from private owned, grid-connected PV and wind systems on homes, businesses, and parking structures. Theoretical calculations showed that the return on investment from a home installed solar PV system was greatly improved when factoring in transportation use. Today, the author believes this even more, as gasoline prices in California increased by nearly 50% since then. Replacing gasoline at $4.00/gallon with solar PV electrons is far more economical than replacing utility electrons for home use. This is because on a relative basis home use electricity savings are less than gasoline cost savings using those same electrons.

Residential solar ROI in the U.S. depends on a number of factors:

• Solar system performance - a function of orientation, pitch (slope) and shading issues
• Electrical rates (individual utility rates, time-of-use tiered rates)
• Availability of programs to sell solar power back to utilities at time-of-use rates
• Rate of annual price increase for electricity (typically 5%/year)
• Utility or state/local subsidies (usually referred to as rebates or tax credits)
• Federal investment tax credit (cap of $2,000 for U.S. residences)

Below are examples of a U.S. solar PV installation ROI assuming no local rebates/credits and a future average utility rate of $0.185/kWh.

The payback is roughly 30 years (although local rebates can reduce this to 8-12 years). But look what happens when you factor in using solar watts for a plug-in car that travels 20 miles per day on battery power, displacing 1 gallon of gasoline (@ $4/gallon).

 *965.3 kWh = 131 wh/mile x 20mile/day x 365 days/year

Even without rebates the plug-in vehicle lowers payback time from 30 to 10 years. A Prius-sized plug-in hybrid driven 20 battery miles per day using 131 Wh/mile from a wall outlet would roughly require a 784 watt solar system to bank enough electrons to the grid during the day for auto recharge, or approximately 4-5 high output solar panels for many regions in the U.S. A Tesla vehicle using roughly 310 Wh/mile from a wall outlet, would require a 1.855 kilowatt (kW) solar system (~ 9-10 panels) to drive those same 20 miles. The author estimates that a full size SUV plug-in would use approximately 475 Wh/mile, or a 2.84 kW solar system. (NOTE: Car type, driving profile, recharge schemes, local weather profile, solar pricing, and other factors can impact these numbers. This example is only meant as an approximate guideline)

Consumers thinking about investing in a home solar system should seriously consider capacity for a plug-in vehicle in their plans, particularly when attractive and affordable plug-in cars come to automobile showrooms in 2010. Replacing stops at a neighborhood gasoline pump with their own solar pump will begin to make more and more sense for many people.

Conclusion

The use of electrons for transportation will continue to increase, albeit at a slower pace than many wish. Current market forces favor this transition. Fossil fuel prices are trending upwards. Renewable energy growth is accelerating, although energy storage schemes and smart grid advances lag by comparison. Residential solar PV will become more attractive when plug-in cars are factored into the investment. Solar PV panels are currently being installed as fast as they are being produced, and will become cheaper and more ubiquitous as thin-film cells become mass produced. Fully integrated, factor built plug-in vehicles are on the very near horizon, beginning in 2010. And most importantly, battery technology is continuing to improve.

As written in the earlier article: "Electric cars don't have an internal combustion engine, gas system (tank, cap, filter, pump, line, carburetor), spark system (plugs, wires, distributor), exhaust system (manifold, pipes, catalytic converter, muffler), air filter, oil system (oil, pump, filter, reservoir, cap), cooling system (radiator, coolant, pump, temperature sensors), crude oil emissions, nor do they need smog inspection or tune ups. These components are replaced with a bigger battery, electric motors, and an advanced battery management system. The environmental and ownership cost benefits to an all electric car are compelling, and its development needs to be watched closely in the coming years."

A final point the author wishes to make is that the march of electrons under your hood has already been occurring, even with our existing internal combustion engine vehicles. Today's cars have many motors in them, but only one of them runs on gasoline. The rest are electric. Not all that long ago a car's fuel pump, power steering, power brakes, water pump, and fuel injection (just to name a few) were driven off of the mechanical energy derived from the engine (via belts). Today, most vehicles use electronic fuel injection, electronic brake assist, electronic power steering etc. Thus, we have already been following a clear evolutionary path towards plug-in vehicles.

If spurred on by government energy policies, the global transition away from transportation fossil fuels and their contribution to man-made CO₂ emissions can happen within 20 years.

Further Reading:

• A Vision for a Better Future - The Coming Energy Shift