7-17-2014 New PV Storage Options
PV storage is rapidly becoming one of the highest priorities in the solar industry. The ability to store excess power produced by solar panels during the day to be used at night helps to keep power more consistent. PV storage is also important to the utilities, because the intermittence of solar power and other renewables such as wind would normally require an infrastructure upgrade or redesign.
PV Storage: Electrical and Thermal
The two ways to store energy are electrical and thermal. Thermal storage is currently the most commonly used storage system. Residential hot water heaters with storage, underground thermal energy storage (UTES), cold water storage, and pit storage are in use, and ice storage and molten salt are becoming popular. Thermal-chemical storage is also being researched, and is thought to be both an efficient and indefinite way to store solar energy.
Thermal storage works by either heating or cooling a material that doesn’t easily change temperature and the heat or cold created helps to regulate the temperature inside of buildings. Ice storage and cold water storage are used by cooling water or making ice at night and offsetting the large amount of electricity needed for air conditioning. The same principle applies to heating something like certain kinds of salt, which can be used as heating in the winter. The efficiency of this kind of storage is over 90%, and can be used in both small scale and large scale projects.
The most common forms of electrical energy storage are pumped storage hydropower, compressed air energy storage, sodium-sulfur batteries, flywheel (low speed), and lithium-based batteries. There are many more electrical PV storage systems in the research and development phase. These systems are flow batteries, flywheel (high speed), supercapacitor, superconducting magnetic energy storage (SMES), adiabatic compressed air energy storage, hydrogen, and natural gas. Of those listed, the SMES is the most efficient way to store energy, with an efficiency of greater than 95%.
The Drive for Storage
Policy makers in California have created a law where the “California Public Utilities Commission to consider creating an energy storage procurement mandate for utilities.” The law also requires that “any storage that is mandated must also be cost-effective,” and the CPUC has accepted this challenge. “CPUC created a new program requiring utilities to procure 1.325 gigawatts of new storage by 2024” which is enough storage to produce energy at peak output for over 1 million California homes. The GreenTech Media article “Is an Energy Storage Tsunami About to Hit California?” talks more about the programs being used to add energy storage to utilities.
Other states and even other countries are likely to follow California in acquiring storage, especially if the various programs developed make a difference. PV storage is getting cheaper and more efficient, and most materials used are earth-abundant. Other options, such as the hydrogen and natural gas electrical storage can even be used to create renewable fuels. The ability to effectively and efficiently store clean energy that is usually intermittent is a huge step in changing the way we get energy.