<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>donarb</author><text>Yard service is a perfect application for these types of locomotives. Diesel fired locomotives tend to sit around idling and burning fuel many more hours than they are being used every day. Diesel locos also tend to not be very fuel efficient when constantly stopping&amp;#x2F;starting around the yard.</text><parent_chain><item><author>bobthepanda</author><text>The lede is a bit buried here:&lt;p&gt;&amp;gt; Union Pacific plans to purchase 20 battery-electric locomotives for &lt;i&gt;yard service&lt;/i&gt;&lt;p&gt;If all they&amp;#x27;re doing is moving around a yard, they&amp;#x27;re not ever very far from a charging station and they&amp;#x27;re moving at very low speeds.</text></item></parent_chain></comment><story><title>Union Pacific to buy 20 battery-electric locomotives for yard service</title><url>https://railfan.com/union-pacific-to-buy-20-battery-electric-locomotives/</url></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>seanp2k2</author><text>Yep, battery energy density is still far off from fossil fuels.&lt;p&gt;This is from 2012 but still relevant and why we don’t have electric commercial passenger planes, and probably never will until we make 10x gains in energy density:&lt;p&gt;“””
Stored energy in fuel is considerable: gasoline is the champion at 47.5 MJ&amp;#x2F;kg and 34.6 MJ&amp;#x2F;liter; the gasoline in a fully fueled car has the same energy content as a thousand sticks of dynamite. A lithium-ion battery pack has about 0.3 MJ&amp;#x2F;kg and about 0.4 MJ&amp;#x2F;liter (Chevy VOLT). Gasoline thus has about 100 times the energy density of a lithium-ion battery. This difference in energy density is partially mitigated by the very high efficiency of an electric motor in converting energy stored in the battery to making the car move: it is typically 60-80 percent efficient. The efficiency of an internal combustion engine in converting the energy stored in gasoline to making the car move is typically 15 percent (EPA 2012). With the ratio about 5, a battery with an energy storage density 1&amp;#x2F;5 of that of gasoline would have the same range as a gasoline-powered car. We are not even close to this at present.
“””&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.aps.org&amp;#x2F;publications&amp;#x2F;apsnews&amp;#x2F;201208&amp;#x2F;backpage.cfm&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.aps.org&amp;#x2F;publications&amp;#x2F;apsnews&amp;#x2F;201208&amp;#x2F;backpage.cfm&lt;/a&gt;</text><parent_chain><item><author>bobthepanda</author><text>The lede is a bit buried here:&lt;p&gt;&amp;gt; Union Pacific plans to purchase 20 battery-electric locomotives for &lt;i&gt;yard service&lt;/i&gt;&lt;p&gt;If all they&amp;#x27;re doing is moving around a yard, they&amp;#x27;re not ever very far from a charging station and they&amp;#x27;re moving at very low speeds.</text></item></parent_chain></comment><story><title>Union Pacific to buy 20 battery-electric locomotives for yard service</title><url>https://railfan.com/union-pacific-to-buy-20-battery-electric-locomotives/</url></story>