A Comprehensive Hydraulic Gravity Energy Storage System – both for Offshore and Onshore Applications

Valerie Neisch, Markus Aufleger, Robert Klar, Simon Lumassegger

Friday 3 july 2015

12:36 - 12:39h at Europe 1 (level 0)

Themes: (T) Hydro-environment, (ST) Renewable energy resources, Poster pitches

Parallel session: Poster pitches: 15G. Environment - Renewable & Wetland

The lack of efficient and cost-effective energy storage technologies is a serious barrier at present for expanding renewable energy investments in Europe. At the University of Innsbruck there are two different Hydraulic Gravity Storage Systems under development. The POWERTOWER is a new hydraulic energy storage method based on the well-established pump storage technology, which can be installed independent of the topography. The Powertower consists of a closed system, which can be positioned close to onshore sites where volatile renewable energy is generated. Its main feature is a water-filled cylinder, which houses a vertically movable load. The load causes a constant pressure in the lower reservoir regardless of its position. In order to store energy, water is pumped from the upper to the lower reservoir. As a consequence the load rises in the cylinder and the energy content increases (load at the top = system fully charged). In order to release the stored energy, the flow direction is reversed. The load is lowered and drives a turbine. With this arrangement, electrical energy can be stored with high efficiency (around above 85%) and significant sustainability. BUOYANT ENERGY complements this technology perfectly for offshore applications. While conventional pump storage plants consist of an upper and a lower reservoir, Buoyant Energy uses a small reservoir (floating structure), which is located within a larger reservoir – typically the Sea. Water can be moved from one reservoir to the other by means of turbines and pumps or pump-turbines. The energy is stored entirely as potential energy in the floating structure. In order to store energy, water is pumped from the smaller to the larger reservoir. As a consequence the floating structure of the smaller reservoir rises. In order to release the energy, the structure is lowered and the inflow powers a turbine. Marine renewable energy is a growing field which expects to contribute significantly to the European energy mix. However, so far no suitable local energy storage solution for the direct integration of those volatile energy sources exists. Buoyant Energy does have the potential to solve this problem.