2.3.1　Why PHEV

Text（课文）

The PHEV，as the name suggests，differs from an HEV only by the fact that it allows one to plug in a cable running from the vehicle to a household utility wall socket at home or elsewhere to charge the vehicle's battery.To extend the flexibility of the system，it is also possible in principle to use the engine and/or the battery system in the vehicle to generate AC power and feed it back to the utility grid.Since plug-in allows a fair amount of external utility system energy to drive the vehicle，it is helpful to use a larger battery than in a regular HEV.A larger battery is not a required part of the PHEV，but having one definitely benefits fuel economy and also increases the range of the vehicle when fully charged.In an HEV，using a much larger battery may not necessarily be the optimal choice in terms of design，since the ICE is always capable of kicking in，when the battery needs to be charged.People sometimes think that a large battery is mandatory for a PHEV，which may not be the ease.How large the battery can be depends on the packaging space available in the vehicle.If the battery size is small，the benefits from the PHEV will be merely incremental，whereas if it is too big it can be very expensive and will take longer to recharge from the utility system.Note also that the household utility system may have some limitations on how much current it can sustain in charging a battery system，hence some safeguards are necessary for the plug-in.Since the cost of utility energy at present is much lower than the price of gasoline，it makes sense to use the PHEV，where possible.

New words and expressions（单词和短语）

1.New words（单词）

2.Expressions（短语）

Notes to the text（难点解析）

★1.In a HEV，using a much larger battery may not necessarily be the optimal choice in terms of design，since the ICE is always capable of kicking in，when the battery needs to be charged.在HEV上，当蓄电池需要充电时，由于内燃机总能够介入，因此从设计来看，使用更大的蓄电池不一定是最佳的选择。

★2.Note also that the household utility system may have some limitations on how much current it can sustain in charging a battery system，hence some safeguards are necessary for the plug-in.我们也应当注意，居民用电系统在为蓄电池系统充电时，其提供的电流大小有限制，因此有必要为插电方式设计保护装置。

Exercises（练习）

◆1.Translate the following passages（expressions）into Chinese（英译汉）

（1）How large the battery can be depends on the packaging space available in the vehicle.

（2）plug-in hybrid electric vehicle

◆2.Translate the following passages（expressions）into English（汉译英）

（1）如果电池较小，那么PHEV的成本较低；反之，电池较大，成本就会很高，也需要花很长的时间利用电网充电。

（2）原则上，PHEV能够利用发动机和/或蓄电池系统产生交流电，反哺公用电网。

◆3.Directions:Answer the following questions briefly according to the text

What are the differences between HEV and PHEV？

Reading material（阅读材料）

PHEVs are hybrid electric vehicles that can draw and store energy from an electric grid（or a renewable energy source），to eventually propel the vehicle.

This simple functional change allows a PHEV to displace petroleum with multisource electrical energy，including renewable energy resources，such as wind and solar energy.Such a change has critical beneficial impacts on the overall transportation sector petroleum consumption，total emissions，as well as on the performance and makeup of the electrical grid.PHEVs are seen as one of the most promising means to improve the near-term sustainability of the transportation as well as stationary energy sectors.Surveys have shown that there exists a considerable market for PHEVs.Renault and Daimler-Chrysler have produced limited production PHEVs.General Motors and Ford Motor Co.have developed and displayed PHEV concept vehicles.