Optimizing PV Systems January 2015 - Part 2: Energy Storage | Page 16

Overall, lead-acid is the proven and cost-effective technology most frequently used in renewable energy and can provide high energy densities at a lower price per kWh compared to other energy storage technologies. Lead-acid designs can be credited with lowering the cost of entry for energy storage to the point where solar electricity systems can fully leverage storage to operate 24/7 and during emergencies. In regions with very high utility electricity prices, such as Hawaii and other island locations, lead-acid battery-based systems help PV/solar owners achieve grid parity.

Lead Acid Technology Overview (1)

Lithium-Ion

Lithium in its natural state is volatile and very unstable. When a non-metal solution is applied to the lithium to create an alloy, a stable construction is formed with the ability to safely store energy.

Figure 2 - Lithium Ion Chemical Diagram (Source: Andy Chu)

A lithium ion battery consists of positive electrolyte called a cathode which is metal oxide and negative electrolyte called anode which is made up of carbon. The ions between the two electrodes (cathode and anode) travel back and forth during the recharge and charge cycles, creating energy.

There are several raw materials and chemical components made up of a lithium-ion battery, but the 3 most common chemistries are

OPTIMIZING PV SYSTEMS - PART 2: ENERGY STORAGE

Innovative off-grid solar energy storage in Madagascar

Case study

Saft Sunica . plus nickelcadmium batteries store solar energy in a scheme set up by Schneider Electric to provide safe and clean electricity to residents of an isolated village .

Isolated and remote locations

Schneider Electric ’ s programme of social responsibility , named BipBop ( Business , Innovation and People at the Base Of the Pyramid ) aims to use the electrical systems firm ’ s expertise to provide safe , affordable and green energy to the people who need it most . With an operation in Madagascar serving the mining industry , Schneider saw an opportunity to provide a reliable off-grid power supply to the population

of the village of Marovato , on the east coast of the island .

• Marovato ’ s 120 residents are spread across 20 houses and used only 490 W .

• Schneider specified a system to generate 1,400 W at peak times .

• 18 of Saft ’ s Sunica . plus 920 Ah cells were specified to store energy for night-time use .

• Batteries were selected for their long life , rugged design , operation in extreme temperatures and suitability for photovoltaic applications .

With 1.6 billion people worldwide having no access to electricity , solar energy storage can play a part in providing reliable energy .

www.worldofphotovoltaics.com

Energy Storage eFeature | January 2015