Frequently Asked Questions
The main difference regarding the investment costs compared to other energy storage systems is the much cheaper storage material rock/gravel (approx. 6 - 12 €/t compared to e.g. solar salt approx. 500 - 800 €/t). An additional point is the wide use of standard components that can be bought on the market (Heat exchangers, fans, storage vessel, etc.). As a result, STORASOL is able to follow a multisourcing strategy to reduce costs for the main components.
The operational costs for the storage systems mainly depend on the electricity demand of the fan. Based on the innovative arrangement of the storage material (large surface area of sand ==> low required air velocity ==>exponential decrease of the pressure loss) the power consumption of the fan (and therefore the electricity demand) is low.
The use of relatively simple standard components results in low maintenance costs. Based on our experience, these costs can be estimated as 0.2 - 0.6 % of the investment cost of the overall HTTES-system.
The main reason for the low pressure loss is the increase in the cross-sectional area of the of the fluid flow when passing through the sand layers which results in a decrease in speed from about 25 - 40 m/s to 0,5 - 1,5 m/s. The relationship between fluid velocity and pressure loss is quadratic, resulting in a very high pressure loss at high fluid velocities. Furthermore, modules of the HTTES are charged individually, as soon as one module is charged the following module is charged. The optimization of the fluid flow through the modules combined with the design of the system are areas of expertise of STORASOL.
The STORASOL-HTTESS can cover a temperature range of approx. 50 - 650 °C with the current setup (compared to molten salt approx. 270 - max. 560 °C). Regarding the storage material, the possible temperature range could be extended to temperatures above 1.000 °C.
Recent projects with a high investment volume of more than 100 Mio €, including a commercial scale high-temperature storage system, are usually financed by banks. High scale project financing by banks is only possible for projects using exclusively state-of-the-art technology. To reach this status, the construction and successful operation of demonstration plants is required. With additional positive due-diligence of the technologies (regarding technical functionality and operational capability) it is possible to finance, build and operate the technology in a commercial scale. The STORASOL system has been successfully in operation in a large-scale (megawatt) demonstration facility at the University of Bayreuth since 2015.