Thermal energy storage (TES) is a load management technology with a significant potential to shift load from peak to off-peak demand hours.
Until recently, renewable energy sources accounted for a small share in the power generation portfolio across the globe. Increasing greenhouse gas emissions and rising fuel prices are some of the primary reasons behind the efforts to effectively employ the various sources of renewable energy. However, most of the renewable energy sources, particularly wind and solar are by nature intermittent. Concerns regarding their intermittent/variable nature are becoming prominent due to their increased adoption for power generation.
Thermal Energy Storage Concept and Benefits
Energy Storage technologies are increasingly being adopted as a mean to reduce the time or rate mismatch between energy demand and energy supply. These technologies can capture/store renewable energy when it is available and save its use for a period of its requirement, which increases the availability of renewable energy.
Thermal energy storage (TES) is a load management technology with a significant potential to shift load from peak to off-peak demand hours. These technologies are being deployed in large number of applications, including private commercial and industrial facilities, government buildings, universities, research institutes, medical facilities, and other institutional facilities. Commercial buildings are the major end users of electricity, and thus utilities across the globe are focusing their strategies towards resource – planning activities. Thermal energy can be stored on the basis of three basic principles: as sensible heat in the heat storage media, as latent heat in phase-change materials (PCMs) or as thermochemical energy arising from chemical reactions at operating temperatures ranging from 233.15K to 673.15K.
Thermal Energy Storage: Technology Comparison
Large capacity additions of concentrating solar thermal power (CSP) are being planned across the globe with the additional benefit of energy storage. TES technologies are playing an important role in moving solar power into the mainstream of the power generation portfolio. These technologies are designed to improve the overall reliability and availability of the solar facility – thus increasing its overall value. TES provides operational flexibility required for the CSP facility to be more competitive and create the most value as a project. TES allows the plant to be optimized to address the peak load profile of the electric utility. TES also allows a shift in dispatch of the electrical power from off-peak hours to a period when peak electricity demand occurs.
Demand and Growth Drivers
According to a lead researcher at market intelligence firm Transparency Market Research (TMR), “TES capacity installation stood at 2,038.3 MW in 2013 and is projected to reach 6,070.2 MW by 2020”. Electrical power systems are undergoing significant changes as a higher number of renewable energy sources are being integrated into these systems. Industry drivers such as increased adoption of renewable energy sources, deferral of transmission and distribution electrical network upgrades, and increasing access to efficient, reliable, and quality electricity are creating demand for TES technologies across the globe.
Large Scale TES Projects
There are nearly 166 TES projects across the globe. Of this, 64 are sensible heat, 92 are latent heat, while 10 are thermochemical storage projects. North America had 108 TES projects by 2013 followed by Europe with 31 TES projects, Asia Pacific with 9 TES projects, and Rest of the World (RoW) with 18 TES projects. The U.S. accounts for the major portion of the global thermal energy storage projects. The country held nearly 67.4% share of the overall thermal energy storage projects installed in 2013. The U.S. had the maximum number (107) of operational TES projects. The country was followed by Spain with 24 operational TES projects in 2013.
Solana Generating Station (U.S.)
Located in Arizona (the U.S.), the Solana solar generation plant has the gross turbine rated capacity of 280MW. It was the first solar plant with thermal energy storage capabilities in the U.S. The plant employs parabolic trough technology that is used in conjunction with thermal energy storage systems. This enables it to generate electricity for six hours without the concurrent use of the solar field. This is the largest energy storage project and first in the U.S., to store over 1000MWh of energy that can be dispatched upon demand without sunlight. This project is estimated to reduce Arizona’s need for fossil-fuel based power generation, will generate up to 1,095 TWh of clean renewable energy annually, and would eliminate nearly 650,000 MT of CO2 from being emitted into the atmosphere each year. The deployment of this project would help the state to contribute to goals for renewable energy deployment and targets to reduce the negative impact of climate change. It is estimated that the deployment would also generate revenues between USD 300 million and USD 400 million in 30-year tax and more than USD 1 billion in gross state revenues.
Andasol Solar Power Station (Spain)
Spain is largely dependent on imported energy to satisfy its energy demands. However, the country has more than enough of one of the most environmentally friendly and cheapest sources of energy in the world – the sun. The Spanish government provides funding supports for renewable energy, especially for solar production, which makes Spain as the most favorable and attractive solar-thermal power markets. Located in Andalusia, Spain, the Andasol Solar Power Station is the major thermal energy storage project in Europe. Solar Millennium AG initiated and developed the Andasol power plants. It is the first commercial parabolic trough project employing the molten salt thermal energy storage technology in the region. The Andasol solar power plant (phase 1 to 3) can store energy for about 7:30 hours with molten salt storage technology. The annual operating hours of the solar power plant through thermal energy storage can almost be doubled particularly in peak load conditions. This plant would reduce carbon emissions by 450,000 tons per annum compared with conventional coal-fired power plants.
With 1 operational plant (Ice Energy Toronto Zoo Storage Project) located in Canada, North America reported 108 thermal energy storage projects by 2013. The Extresol Solar Power Station, another notable project in Spain, also uses the molten salt thermal storage technology. This project generates 150 MW of power through commercially available parabolic trough solar thermal technology and can store thermal energy for at least 7:30 hours. Asia Pacific is an emerging market for thermal energy storage technologies. The region has 9 TES projects with 3 projects each in Australia, China, and India. India is expected to emerge as one of the strongest players in the thermal energy storage technologies market in Asia Pacific in the near future. South Africa (3), Morocco (2), Chile (2), and Israel (1) account for the highest number of under construction thermal energy storage projects. Countries such as Chile and South Africa have a higher number of thermal energy storage projects in pipeline. The rationale behind the increased adoption of thermal energy storage technologies in these countries is to effectively utilize intermittent renewable energy sources, without threatening grid stability or the ability to meet demand for energy.
Adoption of thermal energy storage technologies could help ensure frequency stability and grid balance. Thermal energy storage technologies also support the integration of variable energy sources such as wind and solar into the electricity grid. TES include a number of different technologies, each with its own specific application, performance and cost. Technologies based on sensible heat storage provide storage efficiency from 50% to 90% and storage capacity from 10 kWh/t to 50 kWh/t, depending on thermal insulation and the specific heat of the storage medium. Phase change materials (PCMs) have comparatively higher performance and better efficiencies of 70% to 90%. Thermochemical storage (TCS) can provide efficiencies from 70% to nearly 100% and storage capacities up to 250kWh/t with an operation temperature of more than 300°C. The cost of TES technologies depends on application, size and thermal insulation technology. The costs of both PCMs and TCS are usually higher in comparison to the capacity of storage they provide. The cost of storage systems constitutes nearly 30% to 40% of the total system cost. Continued research into energy storage technologies to drive down the upfront capital requirement is anticipated to make thermal energy storage technologies more competitive in the near future.
(This news story is from altenergymag.com)