Impressive Material that Stores Solar Energy for Months or Years

material stores solar energy for months

The Light-Activated Material can Store Solar Energy for a Very Long Time

We know about batteries that can store energy for hours or days or advanced insulation systems that can store energy as heat for hours or days but with a visible loss.

What if this solar energy can be stored for months together at room temperature and that too without any loss? Sounds crazy!

The new material developed by the Researchers at Lancaster University can store energy for several months, or even for years. The light acts as a trigger that signals material to release the stored-up energy on demand in the form of heat.

The Science behind the Innovation

The material is based on a type of ‘metal-organic framework’ (MOF). These comprise a network of metal ions connected by carbon-based molecules to form 3-D structures. These MOFs are porous, and this property enables them to form composite materials by hosting other tiny molecules inside their structures.

Image Credit: nanowerk
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The researchers started with a previously prepared MOF by a different research team at Kyoto University in Japan to find if it could store energy.

Molecules of azobenzene are loaded in the MOF pores.  Azobenzene is a compound that is known to strongly absorb light. These molecules function as photoswitches, –  a kind of ‘molecular machine’ that is shape-shifting i.e. it can change shape when an external stimulus is applied in the form of heat or light.

This process stores the energy in the MOFs like the potential energy stored in a bent spring. Since the azobenzene molecules are trapped in their strained shape, the potential energy can be stored for long periods at room temperature.

This stored solar energy is again released with the application of external heat that acts as a trigger to change or ‘switch’ its state. The release of energy can be very quick like a spring snapping back to its original shape. This provides a heat boost that could heat other devices.

Test Done

The material was exposed to UV light. The exposure caused the azobenzene molecules to get strained inside the MOF pores.

Findings of the Test

  1. The tests demonstrated that the material could store the energy for at least four months. This makes this technological development promising as many light-responsive materials release the stored energy within hours or a few days. This successful development for long-duration solar energy storage opens up many interesting possibilities, cross-seasonal storage being one of them.
  2. Although the material’s ability to store energy for long periods is quite promising, it’s energy density is modest


It will have interesting applications across different avenues such as:

  1. Heating solutions in off-grid systems or remote locations
  2. Solar Energy based environmentally-friendly supplement to conventional heating solutions for houses and offices. 
  3. Its thin coating can be applied to the surface of buildings. 
  4. The coating on the car windscreen to de-ice the glass on cold winter mornings.
  5. In drug delivery – Using photoswitches, drugs could be locked inside the material and then released inside the body on demand using a heat or light trigger 


  1. The MOF composite is solid and hence chemically stable and easily contained. Their solid form makes it much easier to develop into standalone devices or coatings. The previous photoswitches were required to be in a liquid.
  2. It does not have any electronic or moving parts making the system highly reliable. It also ensures no loss in the storage and release of solar energy.
  3. Solar energy can be stored in summers and used in winters

Next Step

Researchers wish to find other MOF structures along with alternative types of crystalline materials with higher energy-storage potential.

Once the technology matures for commercialization, it will uncover many profitable businesses that are currently hidden behind the scenes especially in renewable energy generation and storage.

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