Placing Energy In A Battery Results In A Loss Of Power

Anyone that thinks we can simply store huge amounts of energy in large banks of batteries to use at any time has lost touch with reality. The brave new world of energy storage may not prove to be all it is cracked up to be. At this point, and for the foreseeable future storing the power we need in batteries is just another part of the "green delusion" that has infected society.  We seldom think about it but the energy we put into a battery is not what we get out. There is a loss of energy in the transfer and during the time it is stored. 

An article published on the naked scientists.com years ago states, not all of the energy which you use to charge a battery will come out of the battery in the end. That remains true today. If you look at the efficiency of charging standard, nickel cadmium, or nickel metal hydride battery, the efficiency is about 60 to 70%, so you're wasting 30 or 40% of the energy you're putting into the battery itself.

If you feel that a battery while it is being charged you will find it gets warm. This indicates energy is being wasted. You're also wasting some more energy in the charger because the "transfer" is not 100% efficient either. So, you might be talking about half the energy you're using actually ending up in that battery. While 60% efficiency doesn't sound very good, it's far, far better than what is achieved in a throw-away battery, they are often said to be only 1 or 2% efficient. That's because you've got to get materials to make the battery, you've got to refine them, and you've got to put them all into a case.

It also seems that the amount of charge already in a battery affects charge efficiency. With the battery at half charge or less, the charge efficiency may be over 90%, this drops to nearer 60% when the battery is above 80% charged. Also, it has been found that if a battery is only partially charged, efficiency may be reduced with each charge. This leads to the issue of a battery's life expectancy which is a whole separate matter but still very important when it comes to its potential in addressing our energy problems.

Unfortunately, the charge/discharge efficiency of a battery tells us next to nothing about the real efficiency, because we have to take into consideration where the energy is most likely to come from, and how efficient it is to convert our starting fuel into electricity. The most efficient natural gas generator, the GE H series gas turbine, is 60% efficient at converting gas into energy.

Battery Charge/Discharge Efficiency Li-ion 80% - 90% Pb-Acid 50% - 92% NiMH 66%

Table 1: Battery efficiencies [1-3]

Simply put, the whole process of placing power in a battery will result in a loss of energy. In truth, it is difficult to find solid information about how efficient batteries really are. Adding to the confusion is the fact that there are many different ways to calculate efficiency, and that there are many factors that can be overlooked. 

The efficiency of a battery can be calculated as the amount of power discharged by the battery divided by the amount of power delivered to the battery. This takes into account the loss of energy to heat, which warms up the battery. The charge-discharge efficiencies of various batteries vary greatly. Li-ion efficiencies are extremely high, Pb-acid efficiencies have a huge range, and NiMH efficiencies are rather low.

However, there are many confounding variables other than the charge/discharge efficiency that must be considered when comparing different battery types. For instance, the Li-Ion batteries have a much higher energy density than Pb-Acid batteries, and slightly more than NiMH batteries. This means that for the same weight of batteries, the Li-Ion batteries will be able to produce much more energy, which is a big factor in making car batteries. 

Also, there is the issue of what materials are needed to make the battery and if disposing of it, in the end, is harmful to the environment. Another factor that we have to consider, is that these batteries all depend on a source of energy to be charged and even the temperature is important. When making calculations, we often assume these all optimal and we are using the most efficient way to get electricity, if not, we might see a significant drop in what is achieved. 

Global warming and climate change is considered an increasingly pressing problem by many people and a big "go green" movement is in full swing. To tackle this problem, researchers around the world are constantly looking for new technologies that will help minimize the effects of global warming, such as reducing energy consumption, facilitating the transition to renewables, and how better to store energy. 

While this may be viewed as only a layman's opinion on a complicated subject, it is rooted in reality. It appears an often overlooked but obvious fact is that society is not going to achieve utopia any time soon by rushing to store energy in batteries rather than using it directly from its source. While progress is being made in how to better store energy it does not seem a silver bullet in our answer in achieving environmental bliss. We might better consider how better to use the energy we generate at the time it is produced and by simply cutting waste.

(Republishing of this article welcomed with reference to Bruce Wilds/AdvancingTime Blog)