The world’s cheapest and most scalable energy storage technology has reached an important milestone as solutions for a reliable operation for at least 25 years and other key design requirements has now been certified by an independent third party. Danish renewable and energy storage specialist, Aalborg CSP has received the certificate for the unique Pit Thermal Energy Storage (PTES) lid technology – the world’s first commercial and now certified PTES lid technology. The certificate and stamp of quality is the final important step for the cheapest energy storage technology in the world as a fully commercialized and bankable investment in low-temperature thermal energy storages.

Aalborg CSP has just received the certificate for its PTES technology, a Technology Qualification Certificate which proves that the PTES technology and unique lid solution fulfills the requirements for design and functionality. Among other things this include a minimum lifetime of 25 years, a minimum energy loss and an availability factor of 100% without risk of stoppages. Moreover, a minimum 90% of all materials used in a PTES are recyclable.

Throughout the past years, low-temperature heat storage investments have been made to, among other things, further develop, optimize, and commercialize the complete PTES technology including the insulating lid cover. The latest achievements in improving the insulated PTES lid cover have further matured the PTES technology making it a bankable investment for utility companies worldwide.

Investments in energy infrastructure around storage of excess heating and low-temperature energy is an important building block in the sector-coupling and provides municipalities and energy operations companies with the necessary flexibility as a response to the increasing electrification of our society. Without flexibility, we become much too dependent on a volatile electricity market, which can cause significant variations in the heating cost from the utility companies, states Svante Bundgaard, CEO at Aalborg CSP.


Special lid technology creates long lifetime and high availability

Historically, the PTES lid technology has caused technical issues, un-wanted thermal losses and in worst case breakdowns. The now certified insulating lid from Aalborg CSP was developed with the purpose of creating a commercial and well-documented solution that would address key issues experienced during previous deployment of PTES projects. The lid technology addresses and solves issues related to water accumulation inside the lid, water ponding on top of the lid, air accumulation below the lid and thermal expansion. It controls internal vapor, external rainfall and has an automatic ventilation system that prevents air from accumulating inside the PTES.

Regardless of the types of materials or design solutions used, it has resulted in issues with the insulation ability and durability as well as a significant number of unexpected manual operations and maintenance hours each week to avoid water reservoirs on top of the PTES – or even worse, hidden inside the insulation layers. At Marstal Fjernvarme the newly installed PTES lid is replacing a defect and older generation lid and based on this Marstal Fjernvarme has gained a full-automatic plant which requires a minimum of maintenance and supervision. Likewise, the heat loss from the PTES has been reduced, thereby increasing the efficiency of the overall energy system.

To validate the technology, Lloyd’s Register has inspected the project site in Marstal as well as reviewed and evaluated all technical solutions, critical components, and calculations.  Moreover, performance tests from Marstal have been reviewed to confirm the functional performance, durability, and quality of the PTES lid technology. All specifications, such as the 25-year service life, the maximum heat loss of 10% and the 90% recyclability have thus been checked and verified by Lloyd’s Register.


Low-cost storage technology enables commercialization of PTES technology

The certification was issued shortly after Aalborg CSP received an order for an 11,000 m2 customized lid solution for the 70,000 m3 Integrated PTES system in Høje Taastrup near Copenhagen, Denmark. The PTES in Høje Taastrup is a thermal storage functioning as a thermal battery with a capacity of 3,300 MWh. The thermal battery is charged by heat from the transmission grid and discharged to the district heating network when the demand for heating increases. The lid solution from Aalborg CSP will ensure a lower heat loss inside the PTES resulting in higher performance and reliability of the storage.

The PTES technology has great opportunities and several projects within 200,000 to 1,000,000 m3 have already been identified in what is considered a promising pipeline within the European countries; this, despite the fact that the technology is still not implemented in many countries. However, with the new design concepts, a technology qualification certification and a large-scale commercial project already implemented, the PTES technology will be a key element in the energy infrastructure development in the years to come.