Power Mobility and Storage - ESEC Lecture Extension

By: Graham Hoyes

Published on: February 25, 2017

At the 2017 Engineering Science Education Conference (ESEC), Dr. Donald Sadoway, John F. Elliot Professor of Materials Chemistry at MIT and EngSci alumnus, described his work developing a “liquid metal battery”. Batteries, in their simplest form supplying a voltage resulting from redox reactions occurring at electrodes connected by an electrolyte, are essential to modern society. Batteries power our smartphones, flashlights, laptops, and even pacemakers. Typical batteries are well-suited for small applications: They can be designed to provide a steady voltage for most of their lifetime, with little energy being lost while the batter is not in use. However, on the large scale, power is typically not stored. Rather, it is produced, sent into the electrical grid, and consumed nearly instantaneously. Advancement in energy storage such as liquid metal batteries aim to alter this cycle of instant production and consumption. This article will seek to explore the potential for large-scale energy storage in our power-hungry society.

World energy production in 2014 (The Shift Project, 2014)

As of 2014, world electricity production was in the range of 22 PWh (The Shift Project, 2014). Over 60% of this power was produced from the combustion of hydrocarbons. 17% was from hydroelectric power and another 11% from nuclear. The remaining power consumption, including all other renewables, made up only 7% of world electricity production in 2014. With regards to this breakdown, we consider the question of when can the power be provided? Combustion of hydrocarbons can produce power around the clock, and production can be adjusted to meet peak demands. Current and historical abundance of hydrocarbons, combined with relative inexpensiveness, make them the energy source of choice for many power producers, especially where such resources are abundant. Nuclear energy provides some of the flexibility of hydrocarbons with regards to power generation as well, with generally less harm to the environment (except for the fact that when something goes wrong, it goes really wrong). Notice that hydroelectric is the leading renewable means of power generation. Disregarding the different land requirements of hydroelectric vs. other renewable sources like wind and solar, what makes hydroelectric power more favourable over other renewable sources? Energy storage, allowing producers to alter output to meet the grid demand.

While combustion of hydrocarbons works off the principle of converting chemical to electrical energy, hydroelectric power generation converts the gravitational potential energy of water stored behind a dam to electrical energy. When more energy is needed, more water is let through. When there is excess energy in the grid, it can even be used to pump water back up the dam, converting that electrical energy back to gravitational potential energy to be harvested later. With methods such as wind and solar, it’s not as simple. Storing extra energy for use when none is produced, such as during the night in the case of solar power, requires extra infrastructure and ingenuity.

Consider the Tesla Powerwall 2, the company’s current offering for home power storage (usually for use with solar panels or tiles). Their Powerwall 2 battery can supply 14 kWh of energy on a full charge (enough to power lights and appliances) (Tesla, 2017), which would take around 12 hours to charge with six 200 W solar panels. 3.7 L or 3.3 kg of petroleum, which requires about 0.26 L to produce 1 kWh (U.S. Energy Information Administration, 2017), would be required to produce an equivalent amount of energy.

This makes it evident that, if we are to reduce consumption of hydrocarbons and increasingly rely on renewables, we will need some means of storing surplus energy for use when supply doesn’t meet demand. This may mean individual household batteries such as Tesla’s offering, or large-scale power storage with electricity producers, such as could be offered by technology like liquid metal batteries. Once such a technology is developed significantly, it is likely that our ability to store power on smaller cases will be greatly improved, making electric cars far more practical, or just giving us a longer batter life on smartphones and laptop.

References

  • Tesla. (2017). Powerwall 2. (Tesla) Retrieved February 24, 2017, from https://www.tesla.com/en_CA/powerwall#design
  • The Shift Project. (2014). Breakdown of Electricity Generation by Energy Source. (The Shift Project) Retrieved February 24, 2017, from http://www.tsp-data-portal.org/Breakdown-of-Electricity-Generation-by-Energy-Source#tspQvChart
  • U.S. Energy Information Administration. (2017). How much coal, natural gas, or petroleum is used to generate a kilowatthour of electricity? (U.S. Energy Information Administration) Retrieved February 24, 2017, from http://www.eia.gov/tools/faqs/faq.cfm?id=667&t=8