It is impossible to imagine what the world will be like without electric energy in our daily life. Over the past, human beings have innovated multiple ways to generate electricity and electricity has been widely applied to many living areas. Nonetheless, the usage of electricity is obviously uneven when comes to reality, so the matter of how to store the excess energy becomes especially critical, as ‘electricity’ is usually unsavable due to its genetic attributes.

Even it is impossible to save it directly but this is achievable by other conversion methods. Scientists and electrical engineers already have a couple of solutions at hand:

Theoretically and practically, it covers the following three branches:

Mechanical energy storage: Pumped hydro energy storage (PHS), Gravity energy storage, Compressed air energy storage, Flywheel energy storage.

Electrochemical energy storage; Sodium-sulfur batteries, Lead-acid batteries (LAB), Flow batteries, Lithium-ion batteries (LIB).

Electromagnetic energy storage; Superconducting energy storage, Supercapacitor energy storage.

The demand for economic development and the large scale of using renewable energy has been part of energy safety and sustainable development strategy for countries worldwide. For a common goal of carbon-neutrality by 2050 or 2060 (depends on each country’s timeline). Solar and wind have been the rookie of the power generation army marching for over decades. Their irreplaceable positions have been proved from industrial, commercial, and household recognition. However, due to the instability of photovoltaic and wind power generation, it cannot be connected to the grid at a considerable scale.

Energy storage technology

Energy storage is a market at a macro level and thus needs to be segmented into smaller fields: Photovoltaic energy storage, Wind-generated energy storage, Industrial energy storage, Commercial and Database energy storage, Recharge station energy storage, Communication base backup battery, and Household energy storage……

We can also simplify the list by grouping them into two categories: On-grid energy storage and Off-grid energy storage. The way in how to refine these two categories implicate special logical comprehension on these two categories. We find out the following details may help you to draw a clear picture:

Normally On-grid ESS needs to meet 3 basic criteria: first, high standard of safety, second, long time cycle, and third, outstanding ROI in terms of the cost of construction. The majority of on-grid ESS consumers are national power grids, local power generation agencies, corporate giants who share a common interest: long-term and sustainable revenue and social benefits as well.

There are two options on On-grid side scale: Pumped storage hydropower (PSH) and vanadium redox flow (VRB) energy storage. The benefits of VRB method are aimed at high safety with a scale that can reach from Kwh to Mwh. The principle behind this is by utilizing ‘vanadium’, a natural metal, to make “vanadium” into a compound aqueous solution. The life of this “vanadium” electrolyte is semi-permanent (p.s. the special difference between semi-permanent and permanent). After the battery and the stack are run out of their lifetime, the electrolyte can be recycled repeatedly. The all-vanadium liquid flow energy storage can achieve an energy density of 300 MA per square centimeter, with a pack-stack can achieve a level of about 40-50 kilowatts.

PSH is the mainstream and most matured technology compare with other Grid energy storage tech-methods. And it also represents the highest energy storage market installation rate with 89.3% of the total market share. The working principle of PSH can be understood with three cooperated parts: the upper reservoir and the lower reservoir, the middle is the water transmission power generation system, and the last there is a certain gap between the upper and the lower reservoir. By taking advantage of peak time and off time, we use electricity to pump up the water from lower reservoir to the upper reservoir and then store the water, later release the water from the upper to the lower which converts the hydraulic potential energy into electrical energy. PSH acts similarly to a giant battery which charges and discharges through the two water reservoirs at different elevations that can generate power. Why PSH is still holding a leading energy storage position may be because of several incomparable advantages: a PSH station can operate up for a hundred years with a high energy conversion rate between 70% to 80%, the installation capacity normally starts from the Gwh level. For the most important reason, it is massively affordable technology so far which is vitally important to bring it to a massive market. The cost of PSH is only needs $21 per kWh compared to Lithium battery $90-$110 per kWh. However, PSH remains several limitations, it requires such as specific site to meet the working principles, relatively long construction cycle by at least 3-5 years, and high capital investment threshold, etc.

In recent years, electrochemical energy storage became a new market star especially for Residential energy storage (RESS). Thus, it is widely applied in home energy storage sector. In other hand, electrochemical energy storage overcomes HSP shortcomings by offering flexible installation, less geographical limitations. Whereas the complexity and advanced technology requirements of EES brought many other market challenges for both end-consumer and industrial players.

Lead-acid batteries (LAB) account for the largest market share of BESS. LAB is a relatively well-developed technology with low cost and high safety. However, the lifecycle is much shorter than its competitor lithium-ion battery (LIB). Withholding its leading position during the past decade the LAB has certain strengths that can dominate the market with its unique strengths. The core strengths of acid lead are safe, require less maintenance job, high stability system, and large capacity in relation to its size.

Zinc–bromine battery. The major reason to develop Zinc-bromine battery mainly because of the abundant storage of Zinc minerals on the Earth. So, the cost of the battery can be controlled. Another reason is that the zinc deposition potential is relatively low which contributes to a high energy density.

Lithium Iron Phosphate which also named as LiFePO4 . The cathode material is Lithium iron phosphate. This type of battery uses lithium as a material source has higher safety and a longer lifetime. IC charge and discharge cycle-life can reach 2000 times. The LiFePO4 batteries are the safest type of Lithium batteries as they will not overheat, and even if punctured they will not catch on fire, and the cost is lower than the ternary lithium battery.

A forward-looking analysis

Credit: SunEnergy1

As every country is accelerating its energy transformation in order to increase the reliability & resilience of rechargeable energy generation. Wind and photovoltaic energy generation is on their way to step into an outbreaking period. As wind and sun has their special routines and seasonal fluctuation, the power grid cannot effectively control the energy generation gap between aforementioned factors. The only solution is through storing the excess energy when the wind is blowing and the sun is shining and recharging them when we need the most electricity. In the future, if we successfully shift from traditional energy generation methods to rechargeable ones, we will enjoy our life in regards to how we use electricity during our daily life.

If we observe the above from an evolutionary view of point, photovoltaic combined with BESS will be part of the new generation of home electronics and literally needed by most households. Its importance will be like today’s household applications such as TV, wash machine, vacuum cleaner, etc. Undoubtedly, the penetration of BESS will reach a significant number as well.

By taking an example, we need maybe $100 dollar to fully tank our conventional car. Whereas with a rise of ownership rate of EV, and further electrification evolution, another price system towards a world where power generation is decarbonized, extended electrification will change how we evaluate BESS’s  financial advantages. Besides, global governments are working hard on various incentive programs to promote domestic adoption of BESS to build a new era of consumer-produced power generation.

P.S. Part of this article is revised and referred by