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Solar energy battery storage: what it is and how it works

One of the perceived weaknesses of solar energy is that when the sun is not shining, there is no power. While this may have been the case in the past, nowadays it no longer is – thanks to solar energy solutions paired with battery energy storage systems (BESS), generally called solar-plus-storage systems. As the name implies, these are basically solar energy storage systems that are powered by our favorite star. In these solar-powered BESS renewable energy platforms, the solar power that is not used during the day is stored in batteries, which can then release it at nighttime, either supplementing or entirely replacing grid-provided energy. Battery storage for solar power is a reliable technology which can help users cut down on electricity expenses while offering resiliency in case of blackouts. And, of course, being based on renewable sources, solar battery storage enhances sustainability by helping reduce greenhouse gas emissions.

How does a solar battery system work?

Solar battery energy storage systems work very much like the more traditional kind. Photovoltaic (PV) panels capture the sun’s light, transforming it into direct current (DC) electricity. This electricity passes through an inverter, a device that transforms the direct current into the alternating current (AC) that is used by final users. At this point, the energy produced is consumed immediately or sold to grid operators, if the end user doesn’t need it. Adding batteries to the system enables accumulating the energy for later use, for example for nighttime hours when the sun no longer powers the PV panels or during peak hours when grid power is in heavy demand (and, therefore, more expensive). 


For those who want to know how to add battery systems to solar panels, the answer is simple: they should call specialized companies who have the experience and know-how and whose solar batteries storage characteristics best match their needs. The specialized firm will first of all carry out an inspection of the client’s site to determine which solution is the most appropriate. Factors that must be considered are: 

  • The location where the panels and the batteries will be installed

  • How much sun the location is exposed to

  • The client’s power consumption needs.

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Once the panels have been installed, the supplier will also install an inverter that – as explained above – will convert the PV-produced direct current into the alternating current used in households and other premises. Lastly, the storage batteries are connected to the system and begin to accumulate excess energy to be used when needed.

How much energy can a solar battery store?

Enel X solar energy storage batteries come in three sizes: 5.8 kWh, 8.7 kWh and 11.6 kWh. In terms of functionality, Enel X’s smallest battery can, for example, cover an average family’s electricity consumption for about four hours. Clearly larger sizes offer greater storage capacity and, therefore, more usage time.

How long can solar energy be stored in a battery?

In general terms, a solar battery will be able to hold its charge for anywhere between one and five days. Some producers claim their batteries can provide up to seven days' continuous use. As with the battery’s lifespan, there are many factors impacting the actual amount of time a battery charge will last, including usage, battery size, the quantity of recharging cycles, ambient temperature and battery maintenance.

How long does a solar battery last?

The answer to this question is: depends. The lifespan of a solar energy storage battery can range anywhere from five to 15 years, on average. The main factors influencing battery duration are:

  • The technology used, as each different battery technology has different characteristics

  • How much the battery is used, as measured in usage cycles. Most batteries that are hooked up to PV systems are "deep cycle batteries", which means that they discharge up to 80% of their energy before needing to be recharged.

  • The operating temperature: exposure to extreme temperatures (both high and low) negatively impacts a battery's performance and lifespan. In places characterized by temperate climates - optimal for batteries - the batteries will last longer and perform better

  • Finally - but not least importantly - proper maintenance, which helps extend the solar BESS lifespan.

What are the main benefits of solar battery storage and when is it advisable?


What is solar panel efficiency?

The classic scenario - a blackout caused by a nighttime storm - is just one of the many examples where photovoltaic systems backed up by solar battery energy storage systems (BESS) come in handy. When the grid is out, the batteries take over, automatically and seamlessly, with no supply interruption to the end user. But this is not the only benefit of such a system. Indeed, solar battery energy storage systems paired to solar panels offer many advantages - in terms of environmental sustainability, user economics and resilience – including, but not limited to:
  • Solar energy paired with battery storage systems also help keep consumers’ utility bills lower, by ensuring they need less grid power and also through programs that reward efficient energy use and the re-purchase by grid operators of excess power stored in batteries
  •  Solar energy offers residential and business users a clearcut way to reduce their carbon emissions and, therefore, decrease the size of their carbon footprints
  •  Solar battery energy storage systems increase grid resiliency by on the one hand helping reduce demand loads on energy grids, on the other by using excess energy stored in the batteries to boost grid supply when there are demand peaks
  •  By automatically and seamlessly taking over energy supply for short periods of time, such systems ensure businesses and residential users aren’t left without energy when there blackouts caused by grid faults or when photovoltaic panels can’t generate power (for example, during nighttime).

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