Introduction

Thermal energy storage (TES) involves storing heat or cold for later use in heating and cooling applications. As more renewable energy sources like solar and wind power become prevalent on the grid, TES plays a crucial role in optimizing their potential by time-shifting energy production to better match demand. By capturing excess heat or cold during off-peak generation periods, TES helps reduce emissions and lowers electricity costs overall.

Types of Thermal Energy Storage

There are several major types of TES systems currently in use depending on the medium used to store thermal energy.

Sensible Heat Storage: The most common form of TES, sensible heat storage utilizes the intrinsic heat capacity of a solid or liquid medium to absorb and release thermal energy. Materials like water, minerals, ceramics, and phase change materials (PCMs) are often used to store heat in their internal structure via temperature changes.

Latent Heat Storage: Also known as thermochemical storage, latent heat TES takes advantage of the latent heat released or absorbed during phase changes of materials from solid to liquid or liquid to gas. Common examples include melting salts, paraffin wax, and water/ice. These provide higher storage density than sensible methods.

Thermochemical Storage: A less developed but promising approach, thermochemical storage relies on reversible chemical reactions to store energy in chemical bonds. Reactions like sorption of gases onto solids are used to absorb and release large amounts of heat without significant temperature changes.

Applications of Thermal Energy Storage

TES finds usage across several thermal energy applications:

Space Heating and Cooling: Large-scale TES integrated with renewable energy plants helps shifting thermal loads for commercial building heating/cooling. PCM wallboards directly store solar thermal gains for delayed space heating.

Power Generation: Molten salt TES is frequently used in concentrating solar power plants to store heat collected during the day for electricity production at night. Geothermal and solar thermal power also employ TES.

Industrial Processes: Many industries with high thermal energy demands like food/beverage processing, chemical/petrochemical, and pulp/paper manufacturing utilize TES to shave peak loads and reduce costs.

District Heating and Cooling: District energy systems coupled with TES can leverage diverse energy sources for residential and commercial heating/cooling around the clock.

Cooling of Electronic Devices: Latent heat storage embedded in servers and data centers helps regulate thermal loads and improves energy efficiency of it infrastructure.

Advantages of Thermal Energy Storage

TES offers several environmental and economic benefits compared to conventional energy production and distribution methods:

Renewable Integration: Allows renewable sources to deliver energy beyond generation times by storing surplus power for later use. This significantly boosts their capacity factors.

Load Shifting: Shifts thermal loads from peak to off-peak periods when energy costs less, reducing demand charges and peaker plant reliance.

Emissions Reduction: By better aligning renewable output with demand, TES lowers emissions from fossil fuel peaker plants that otherwise meet fluctuating thermal loads.

Energy Security: Diversifies the overall energy supply and decreases dependency on a single source through time-shifting storage capabilities.

Flexible Design: TES technologies can be deployed at multiple scales—e.g. at power plants, district/building level, or behind-the-meter—based on specific requirements.

Economic Incentives and the Future of Thermal Energy Storage

To promote the widespread adoption of cost-effective TES solutions, governments across the world offer various incentives.

Incentives: Europe leads with substantial subsidies for renewable+TES plant investments under initiatives like ETS. The US provides ITC/PTC credits combined with state-level rebates.

Innovation: Heavy R&D is ongoing to develop advanced PCMs, thermochemical reactions, low-cost thermal transfer media, and integrated storage systems. This will boost efficiencies and drive down costs.

Codes and Standards: Uniform standards and guidelines streamline the TES certification process and quality installation practices paving the way for mass commercialization.

Market Growth: The global TES market valued at $2 billion in 2020 is projected to flourish at 10-15% CAGR to surpass $5 billion by 2030 on the back of net-zero emissions goals.

With concerted efforts towards policy push, technological breakthroughs, and enabling business models, thermal energy storage has immense long-term potential to revolutionize how we produce, distribute and utilize thermal energy – in an affordable and sustainable manner.