Author: Sacha Fontaine, PE

A low-cost, long-life battery empowers individuals to use solar at their homes.

The incentive towards renewable energy has been driven by the German Renewable Energy Act which has heavily funded the use of solar panels; helping to reduce the production price of photovoltaic (PV) panels. Germany aims to have at least 35% of its electricity produced from green sources by 2020. By 2050, green energy is to comprise over 80% of German energy use. To attain these goals, Germany is consistently injecting $2 billion per year in energy research. All these factors have produced far-reaching positive repercussions well beyond the German frontier regarding the global cost of PV panel components.

Closer to home, the Department of Energy (DOE) launched the “SunShot” initiative with the aim of reducing the global costs of PV energy systems by 75% by 2020. The ultimate goal for the initiative is to permit solar energy to be cost-competitive with other traditional forms of energy and maintain this competitive edge without subsidization. This reduced cost would equate to roughly 6 cents per kilowatt-hour making solar energy a very attractive source for individuals interested in preserving the environment as well as those interested in grid independence. Furthermore, this applies to similarly-minded utilities interested in strengthening their grid whilst promoting their green image.

A last factor that has helped to encourage the development of solar energy are the unstable fluctuations in gas and oil prices. This has been crucial in driving renewed interest in green energies and becomes apparent each time fossil fuels costs flare up.

With the cost of solar equipment being driven down, one of the last remaining obstacles to widespread use of solar energy is the intermittency of power. Solar power can go from 90% generation to less than 5% with the passing of a singular large cloud, putting the electrical supply and demand equilibrium completely out of sync. The solution for solar and other types of intermittent power is to level out this equation and the best approach thus far is energy storage systems. The energy storage systems would help to smooth out the peaks and valleys of the intermittent generation by storing excess energy and discharging it when needed. The issue with this has been the inhibitive cost of large scale use or large capacity batteries compounded by their limited lifespan.

According to the DOE, a new promising battery design could address these limitations which in turn would give hope to finally see mainstream adoption of PV at an international level both for residential consumers and utilities.

Dr. Yi Cui, an associate professor of Material Science and Engineering at Stanford University, has created a prototype battery that would regulate the natural fluctuations of renewable energies.

Conventional Redox flow batteries use two liquids, a cathode liquid and an anode liquid, separated by a membrane. The liquids interact via the membrane when undergoing the chemical reaction generating or when storing energy. A few problems arise from this design, the first being that regular maintenance is required for the membrane. The major hurdle is the very high cost of the materials needed to manufacture the membrane as well as the liquids which are typically made of dissolved vanadium, a rare metal.

The new battery designed by Dr. Cui’s team called Lithium-Polysulfide Flow Battery has multiple advantages over the traditional battery design. It uses only one liquid, a polysulfide cathode consisting mostly of lithium and sulfur which are both inexpensive materials. Additionally, the liquid is dissolved in an organic solvent which entirely sidesteps the corrosion issues found in today’s batteries. The new design does not require a membrane, hence eliminating the frequent maintenance while making the entire design more compact. Instead of a membrane, a plate of coated lithium metal creates the chemical reaction where lithium-polysulfide molecules absorb lithium ions when discharging and release them into the liquid when charging.

battery diagram

The team reports that in lab tests, the new design successfully cycled through 2000 charges and discharges, indicating that the new battery would have an ideal use coupled with solar or wind generation.

This new low-cost, long-life battery could bridge the final gap in making widespread use of solar and wind energy a reality.

Sacha Fontaine is the Head of Smart Grid Practice at Theorem Geo Associates, an engineering consulting firm focused exclusively on the electric utility industry. He has 13 years of Transmission & Distribution experience leading EMS/DMS and SCADA integration teams. He has helped utility clients prepare their DOE grant proposals and subsequently managed the projects through their entire lifecycle. Through Theorem Geo, Sacha has supported several of the largest Smart Grid initiatives including the 2 largest US power utilities, one of the largest engineering firms in the world and the 2nd largest Smart Grid Systems manufacturer. Sacha Fontaine holds a bachelor’s degree in Electrical Engineering from McGill University.

Sources:

1. German Renewable Energy Act: http://www.nature.com/news/renewable-power-germany-s-energy-gamble-1.12755

2. US Department of Energy’s SolarShot Initiative: http://www1.eere.energy.gov/solar/sunshot/news_detail.html?news_id=16701