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ELECTRIC VEHICLES Electric vehicles substitute a battery (or other device capable of storing electricity in some form) and electric motor for the gas tank/ICE/transmission components of a conventional vehicle. The key drawback of Electric vehicles has been the inability of batteries to store sufficient energy to allow a large enough range capability. Although batteries can store only a small fraction of the energy in the same weight and volume of gasoline, Electric vehicles may gain back some of this disadvantage because of several efficiency advantages. First, conventional ICE vehicles use about 10.8 percent of their fuel during braking and at idle when the engine contributes no useful work; electric motors need not work during ELECTRIC VEHICLES braking and idling. Second, most of the accessories used in an ICE-powered car, such as the water pump, oil pump, cooling fan, and alternator can be eliminated if battery heat losses are not high, as motor and electronics cooling requirements do not require much power. In addition, the hydraulic power steering in a conventional vehicle must be replaced by electric power steering, which consumes only a fraction of the power of conventional systems.14 The reduction in accessory use saves as much as 9.5 percent of fuel consumption on the EPA test cycle. (Real world fuel efficiency and range are considered following the discussion of the Electric Vehicle’s efficiency on the EPA test) And although the ELECTRIC VEHICLES may need some power for the brakes, this requirement is probably small owing to the use of regenerative braking, as described below. Third, some of the energy lost during braking can be recovered by an Electric Vehicle, because the motor can act as a generator when it absorbs power from the wheels. The energy can be stored in the battery and later released to drive the motor. As noted earlier, the energy lost to the brakes in a conventional car is about 35 percent of total tractive energy. For various reasons—transmission and generator losses, battery charge/discharge loss, requirement for some conventional braking capacity--the actual energy recovery is considerably less than this.15 Actual systems in the Toyota Electric Vehicle16 and the Cocconi CRX,17 which have the best regenerative braking efficiencies reported, provide range increases of about 17 to 18 percent maximum. An 8 to 10 percent range extension is more typical of current Electric vehicles, such as the BMW El. Fourth, the motor is quite efficient in converting electrical energy to shaft energy, with cycle average efficiencies for good motors in the 75 to 80 percent range in the city cycle, as opposed to gasoline engines, which have an efficiency of only 20 to 23 percent on the fuel economy test cycle. There are several factors working in the opposite direction. Losses from the primary energy source to energy delivered to the vehicle--critical for concerns about greenhouse gas production -- generally are much higher for Electric vehicles than for gasoline vehicles, because electricity generation efficiency is quite often low (about 34 percent for a conventional coal-fired powerplant), and electricity generation may add another 10 percent in losses. Additional losses occur at the battery charger, in losses in discharging the battery, and in battery internal self discharge, wherein the battery (or flywheel, or ultracapacitor) gradually suffers losses over time. Another important factor is that Electric vehicles may be much heavier than an ICE-powered vehicle of similar performance (and have lower range18), because battery size is critical to range and power--the added weight then creates higher rolling resistance and higher inertia losses (of which only a portion are regained from the regenerative braking). Considering the fill range of energy losses, an ELECTRIC VEHICLES may well be less efficient on a primary energy basis than a conventional vehicle of equal size and acceleration performance, especially if the ICE vehicle is particularly fuel efficient. One such primary energy comparison between a BMW El and VW Polo diesel,19 which are comparable in size, is shown in figure 4-1. In this comparison, the overall BMW El motor efficiency is very low, at 66 percent rather than 75 to 80 percent; if this were changed to 80 percent, then the ELECTRIC VEHICLES would have the same primary energy efficiency as the diesel car. The BMW comparison also shows some real world effects of energy loss owing to battery heating--the battery is a high-temperature Na-S battery--and includes accessory losses. Internal self discharge or battery heating losses reduce efficiency in inverse proportion to miles driven per day. Accessories such as the power steering and power brake consume a few hundred watts of power typically, but the air conditioner, heater, and window defrosters are major drains on power. Some Electric vehicles, such as the GM Impact, have replaced the conventional air-conditioner or heater with a heat pump which increases accessory load to 3 kW.20 A typical advanced ELECTRIC VEHICLES will consume about 12 to 15 kW at 60 mph (see table 4-621), so that accessory load represents a substantial fraction of the total power demand of the vehicle. Thus, with these accessories on, highway range can be reduced 20 to 25 percent; range in city driving can be reduced 50 percent. Cold or hot temperatures also impact the battery storage capacity, so that the range reductions owing to accessory power loss are only one part of the picture. In very cold weather, alkaline batteries and lead-acid batteries have significantly lower energy storage capacities, as discussed earlier. Peak power is also affected, so that both range and acceleration capability suffers. At 20oF, the effect of accessory loads is also very high, as it is not unusual to need headlights, wipers, defroster, and passenger heating in such situations. The combined effect of reduced battery capacity and higher loads can reduce the range in city driving by as much as 80 percent. In hot weather, the battery can be power limited owing to the difficulty of removing the heat created when high power is demanded from the battery, and internal self discharge of batteries can also be higher. Unfortunately, hard data on battery losses in hot weather is not available publicly. The analysis of overall vehicle weight, and the tradeoffs among range, performance, and battery weight are especially important for an electric vehicle. Generally, adding more battery weight allows greater vehicle range and power. However, there is a limit to this relationship: as battery weight increases, structural weight must also increase to carry the loads, and a larger—and heavier--motor is required to maintain performance. This weight spiral effect leads to rapidly declining benefits to each additional battery weight increment, and finally to zero benefit. It is possible to examine these tradeoffs by using energy balance equations similar to those used for ICE engines, coupled with some simplifying assumptions about motor output requirements for normal performance requirements (50 kW/ton of vehicle weight to allow normal levels of acceleration and hill climbing), and using a “best-in-class” specific traction energy measured in kilowatt hours per ton-kilometer (kWh/ton-km), that is, assuming the vehicle being analyzed attains the energy efficiency of the best available Electric vehicles with regenerative braking, which is about 0.1 kWh/ton-km. Figure 4-2 shows the relationship between battery weight and range times the specific energy of the battery, battery weight gets impossibly weight of the battery does not provide enough energy to increase performance. What does this figure say about the relationship between battery As range approaches six large, because the added range while maintaining weight and range for a particular vehicle? If an ELECTRIC VEHICLES were made by using a 1995 Taurus as a “glider,” with beefed-up structure and suspension if necessary, obtaining a 90-mile range with an advanced semibipolar lead acid battery22 would require 1,600 lbs of battery, and the total weight of the car would increase from the current 3,100 lbs to 5,240 lbs (in reality, useful range would be only about 70 miles since lead acid batteries should be discharged only to 20 percent of capacity). 23 In contrast, a nickel-metal hydride (Ni-MH) battery, with an SE of 72 Wh/kg, of the same weight will provide a range of more than 150 miles. The weight of nickel-metal hydride battery to provide a 100-mile range is 957 pounds, while the car weight falls to 3,305 lbs, illustrating the importance of weight compounding effects in an Electric Vehicles. The second constraint on the battery size is that it must be large enough to provide the peakpower requirement of the motor, or else some peak-power device such as an ultracapacitor or flywheel may be necessary. Using the same assumptions as before (about vehicle power requirements and energy efficiency): to obtain a range of 100 miles, the specific power capability of the battery divided by its specific energy must be at least 3.125 hr-1, or else the power requirement becomes the limiting factor on battery size. If the range requirement is doubled to 200 miles, then the minimum ratio declines to 1.56 hr-1. For a 100-mile range, only the advanced semi-bipolar lead-acid battery meets this requirement, with an SP/SE ratios of almost 5, while the Ni-MH battery has a ratio of about 3. The existing “hot-battery” designs provide ratios of only 1.25, while more recent advanced designs provide ratios closer to 2. The important point of this discussion is that doubling the specific energy (e.g., by substituting a battery with better energy storage capability) does not automatically lead to half the battery size, if the battery’s power capability is inadequate to provide “average performance.” Relaxing the performance requirement reduces the required ratio, illustrating that hot batteries with good specific energy but low specific power are best applied to commercial vehicles, where range is more important than performance. One alternative is to include peak-power devices such as ultracapacitors with these batteries to provide adequate peak power. In Electric Vehiclealuating the characteristics of Electric vehicles in each of the four market classes, OTA made several assumptions about ELECTRIC VEHICLES production. We assumed that each ELECTRIC VEHICLES make/model could be manufactured on a “conversion” assembly line to produce 2,000 vehicles per month (24,000 per year), implying total ELECTRIC VEHICLES sales (across all models and manufacturers) of at least several hundred thousand vehicles per year. This assumption is required to establish economies of scale, and the assumption that Electric vehicles will be based on “gliders” (conventional vehicles stripped of their drivetrain and modified as necessary) is required to establish that the vehicle body technology will be similar to the technology of the baseline vehicles. Total investment in assembly line equipment, tooling, development, and launch is estimated at $60 million for this type of facility based on recent DOE studies24 and is amortized over a four-year cycle. It should be noted, however, that total costs are dominated by battery costs, so that ELECTRIC VEHICLES cost is not greatly affected by modest errors in the $60 million estimate. GM and BMW, among others, have displayed purpose designed Electric vehicles, which are vehicles designed from the start to be electrically powered. It is unclear, however, how the design and engineering costs for such vehicles can Electric Vehicleer be amortized over their likely low production rates, and GM officials have publicly stated that the $250 million invested in the Impact to date will never be recouped.25 The advantage of purpose designed Electric vehicles is that design decisions about items such as lightweight materials would tend to be different depending on whether the end result was a gasoline-powered vehicle or an electrically powered one; ELECTRIC VEHICLES designers would favor energy efficiency to a greater extent than gasoline vehicle designers. Building Electric vehicles from gliders based on OTA’s advanced vehicle designs eliminates these differences, however, as these designs also are geared toward maximum energy efficiency. Table 4-7 shows the battery and total vehicle weight, energy efficiency, and incremental price of several Electric vehicles in each market class in 2005. In each case, the level of body technology and tire technology is identical to the level used in the advanced conventional vehicle scenarios, and prices are calculated as an increment over the advanced conventional vehicle in the same scenario, consistent with the “glider” approach to manufacturing Electric vehicles. Note that the vehicles’ price increments over the business-as-usual vehicles (which may be the better comparison) would be higher than the values given in the table. In 2005, an ELECTRIC VEHICLES powered by an advanced semi-bipolar lead-acid battery with an 80-mile range appears to be a viable though expensive prospect for the subcompact and intermediate car, but less viable for the compact van or a standard pickup truck. The ELECTRIC VEHICLES version of the intermediate car is about $11,000 more than the gasoline-powered car, which is consistent with the results of some other studies.26 In going from gasoline to electricity, weight increases from less than 1,300 kg (2,860 lbs) to over 2,030 kg (4,400 lbs). An ELECTRIC VEHICLES pickup truck could weigh over 6,400 lbs, rendering it an unrealistic proposition. Very significant weight reductions would occur, if the battery used were a Ni-MH design and range restricted to about 100 miles. Incremental prices are almost twice that for the lead acid battery-powered ELECTRIC VEHICLES if the Ni-MH battery costs the expected $400 per kilowatt hour.27 However, if Ovonic’s claims for the Ni-MH battery28 prove correct, the Electric vehicles powered by the Ni-MH battery at $200/kWh would be lower in cost than those powered by the lead-acid battery (at $150/kWh) owing to the weight compounding effects, and the incremental vehicle price would be about $8,800. Table 4-8 shows how the costs were calculated for the year 2005 mid-size Electric Vehicle. Battery and motor/controller costs are as specified in chapter 3, while incremental costs of electric power steering and heat pump air conditioner over conventional systems were derived from supplier quotes. 29 Those “costs” are the costs to an auto manufacturer buying the components at a sales volume of 20,000 to 25,000 per year for this model, but there is an implicit assumption that total battery and motor sales across all models is over 100,000 units per year. Costs of engine, transmission and emission control systems are based on earlier studies by Energy and Environmental Analysis, Inc. for DOE, adjusted for inflation. Analysis of fixed costs is based on the formula presented in appendix A. Note that learning curve effects are included in the costing of batteries, motors, and controllers, but there is no learning curve effect for assembly. Computations for a range of 200 miles were performed with the Ni-MH and sodium sulphur (Na-S) batteries; only the Na-S battery appears to be a realistic proposition from a weight standpoint. However, the Na-S battery-powered ELECTRIC VEHICLES is estimated to cost from $27,000 to $54,000 more than an advanced conventional vehicle, depending on vehicle type; the ELECTRIC VEHICLES powered by Ni-MH would cost Electric Vehicleen more if the projected $400/kWh proves correct. These prices could be lowered significantly, if the range and power criteria were relaxed. Using the same methodology as for the analysis above, a lead acid battery-powered subcompact ELECTRIC VEHICLES can be produced for an incremental price of about $3,000, if range is relaxed to 40 miles and power degraded to about 40 HP/ton. Hence, many of the disagreements about future ELECTRIC VEHICLES prices can be resolved on the basis of vehicle performance and range assumptions, or owing to the fact that some estimates cite “cost” instead of price. In fact, Renault and Peugeot have chosen the limited-range, low-performance ELECTRIC VEHICLES to reduce incremental prices to about $3,000, consistent with this estimate. The Citroen AX Electric Vehicle, for example, has a range of about 45 to 50 miles and a top speed of about 55 mph, with poor acceleration.30 Table 4-9 shows the ELECTRIC VEHICLES characteristics for 2015. As body weight is reduced with new materials technology, and modest battery improvements to increase specific energy are expected to occur by 2015, the weight compounding effects provide for more reasonable prices by 2015. Incremental price for an intermediate-sized lead acid-powered ELECTRIC VEHICLES with a range of 80 miles and with reasonable performance is estimated at less than $3,200 over a similar conventional car with advanced technology, while a Ni-MH powered version could retail for $2,750 to $8,83031 more and offer a range of 100 miles. In a more optimistic scenario, Electric Vehicleen a 200-mile range is possible with Ni-MH batteries at price differentials of about half the 2005 levels, while sodium sulphur batteries can also provide this range for about half of the 2005 price differential, although this is still expensive at nearly $18,000. If the lithium polymer batteries succeed in meeting U.S. Advanced Battery Consortium (USABC) expectations, however, an ELECTRIC VEHICLES with a 300-mile range could become available at an incremental price of $10,400 for a mid-size car, Electric Vehicleen after accounting for the fact that these batteries are likely power limited and will need ultracapacitors to provide the peak power requirements for acceleration. These price estimates clearly explain the reason for the interest in the lithium polymer battery. To model the case where the battery is power limited, we have sized the battery to be able to indefinitely sustain a 60 mph climb on a 6 percent grade, and provided for peak acceleration power capability to be sustained for two minutes. All of these estimates are based on a set of assumed performance levels and OTA’s best guesses about future battery costs and component efficiencies. Ongoing research programs, such as the USABC, have as their goals improving ELECTRIC VEHICLES component costs and efficiencies to values below OTA’s values, and success at achieving these clearly would impact ELECTRIC VEHICLES price and performance. Moreover, some ELECTRIC VEHICLES advocates have concluded that vehicle purchasers can be convinced to purchase vehicles with generally lower performance than current vehicles, in particular with lower range. To examine the implications of R&D success and shifts in vehicle purchasing behavior, we estimated the effects of battery cost reductions, performance reductions, range reductions, and component efficiency changes on the 2005 lead acid-battery-powered, intermediate-size Electric Vehicle. Range reductions have a very large effect on vehicle cost and battery requirements; reducing the range to 50 miles (real) reduces ELECTRIC VEHICLES incremental price to $3,170 (from about $11,000), and reduces battery size to less than 40 percent the size required for a range of 80 miles. Reducing performance levels (with a range of 50 miles) provides only modest reductions in battery weight, but reducing motor and controller costs reduces incremental price to $2,130. If battery costs fall to $100 per kWh from $150, vehicle incremental price is reduced to $960, and including the maximum level of component efficiency of motor/controllers and drivetrain reduces vehicle incremental price to $410. Hence, it is theoretically possible to build a reduced range ELECTRIC VEHICLES for a very low incremental price in 2005, if the most optimistic assumptions were used in all facets of the analysis. Electric Vehicleen if range were kept at 80 miles, incremental price would be $4,125, if very optimistic assumptions regarding performance, component efficiency and battery cost wereused. These findings are summarized in table 4-10, but it is emphasized that the base attributes represent what OTA believes to be the most likely outcome of current R&D trends. OTA’s analysis of ELECTRIC VEHICLES performance and costs shows that the following four factors have significant influence on the analysis results. Range. Vehicle weight and costs increase nonlinearly with range increases. Battery specifications. The usable specific energy and power strongly affect battery size for a given range and performance level. Power requirements can set the minimum size for a battery in many applications. Performance requirements. Relaxing the continuous and peak performance requirement has only a small effect on battery and motor requirements, where batteries are sized for range, but can have a large effect, if batteries are power limited. Component efficiency. Assumptions regarding the overall efficiency of the drivetrain (including motors,power controllers, and gears) as well as the battery charge/discharge efficiency can affect the results, with very optimistic assessments reducing casts by as much as 30 percent over the median estimates. In summary, the analysis finds that in 2005, mid-size Electric vehicles with a range of 80 to 100 miles and reasonable performance would be priced about $11,000 more than an equivalent advanced conventional midsized car, assuming no subsidies. A reduced (50-mile) range ELECTRIC VEHICLES can be offered for a price of only $3,000 more than an advanced conventional car. Electric vehicles with a range of 200 miles however, are expected to be too heavy and unrealistically expensive in 2005. By 2015, incremental prices for an intermediate-size ELECTRIC VEHICLES with a 100-mile range could come down to the $3,000 range. A 200-mile range intermediate-size ELECTRIC VEHICLES would still probably be priced about $24,000 more than an equivalent conventional car, unless the lithium polymer cell battery becomes a reality. If this were the case, it is possible that an ELECTRIC VEHICLES with a 300-mile range could be priced about $12,000 more than an equivalent intermediate car. Note, however, that these comparisons are to OTA’s advanced conventional cars, which have costly body structures (especially the 2015 optimistic case, with a carbon fiber composite body). Public estimates of ELECTRIC VEHICLES prices are often not well documented in terms of the assumptions regarding battery size, vehicle size, vehicle range, and performance, which are all critical to the value of price obtained. For example, a major study for the Northeast Alternative Vehicle Consortium 32 used cost numbers with no specific estimate of motor size and rating, and used a fixed battery capacity (21 kWh) regardless of vehicle weight. In addition, the methodology used to convert cost to price does not follow standard costing guidelines; for example, a fixed amount of the investment is amortized each year instead of being allocated to each ELECTRIC VEHICLES produced, so that as production rises, unit costs fall. Other studies, such as one by the California Air Resources Board33 ignores the difference between cost and price, which understates ELECTRIC VEHICLES prices dramatically. Many estimates of very low ELECTRIC VEHICLES costs from environmental or conservation groups are, indeed, referring to manufacturer costs rather than vehicle prices, or do not control for range or performance. It is quite possible that, if these calculations were made more explicit in terms of assumed ELECTRIC VEHICLES size, range, and performance, and the methodology were corrected to transform cost to price, then much of the difference in price estimates could be easily explained.
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