The PVE Lipno – Aschach Project
Typically, PVE (Pumped Storage Hydroelectric Equipment) systems are used during daily cycles and are governed by the availability and capacities of the upper and lower storage reservoirs. Constructional costs are usually high, and the available energy from a full, upper reservoir is usually no more than a few hours. Ideally located between the Czech Republic, Austria and Germany, we in Central Europe now have a unique opportunity to construct a PVE with a capacity that would enable weekly cycles of a 1000 MW. Note that both upper and lower reservoirs have already been built.
Water levels in the Lipno (upper Vltava) river range from 716.5m to 726m above sea level. The stored energy differential between Lipno and Aschach ranges from 442m to 456m over a distance of 27km between both reservoirs. These capacities would enable a flow-rate through a reversible pump/turbine arrangement of 260m3/second from Lipno to the Danube in its turbine state, and 200m3/second from the Danube to Lipno in its pumping state. The capacity of the reservoirs is such that construction of PVEs with cycles of weekly or longer is achievable. An input imbalance equal to four hours of continuous demand would cause the water level in the upper reservoir to fall by as little as 7.8cm. However, to compensate for this disparity, a five-hour pumping regime would be required in order to replenish the levels between the Danube and the Lipno.
Statistics show that during periods of extreme drought, the Lipno would show a serious negative imbalance. Equally, replenishment by natural means would not accommodate the evaporation rate. Even so, existing hygienic water demands on the Lipno reservoir require a minimum of 7.5m3/second into the Vltava, meaning that the water levels would continue to fall accordingly. In such extreme circumstances, the existing peak-load hydroelectric plant, Lipno-1, can only process 6m3/second. At full power, this equates to 1.6 hours of continuous operation. For these, and other reasons, releases from the Danube by PVE L-A are very important.
Apart from the potential to improve the flow rates of the rivers, Vltava and Elbe during drought, this PVE will also have a positive impact upon the currently undesirable fluctuations in the Lipno reservoir water levels. When comparing identical operating requirements with the existing hydroelectric plant Lipno-1 (offering a gradient of 160m), and the new PVE L-A (offering a gradient of 450m), the new PVE demands 2.8 times less water. This figure also equals the reduced rate of fall in the Lipno reservoir.
During times of extreme flood, as experienced in 2002 when damage costing billions was caused, the new PVE will enable 260m3/second of water to be transferred to the Danube throughout the flood, thereby protecting the river basin at the upper levels of the Vltava, located below the Lipno-1 dam. At the same time, the new PVE will supply the public Czech-Austrian network with 1000MW of ecologically produced energy.
Following numerous studies and expert analyses ongoing since 1998, we propose an arrangement of four, reversible turbine sets that are almost identical to those used in the PVE Dlouhe Strane arrangement. Our new PVE will enable a combined total supply of 4 x 250MW of power, afforded by a single, vertical conduit to a subterranean turbine hall located some 500m below the Lipno level. Three additional shafts are required (ventilation shaft, cable shaft, and assembly shaft). Drainage will be via a 27km long drainage tunnel running between the turbine hall and the Danube. With a DN of 10.5m, the drainage tunnel will be constructed of specially made, pre-fabricated concrete sections.
Thus far, all of the studies and analyses support the feasibility of the proposed PVE. Moreover, the proposal is based upon 50 years of proven success at the Lipno-1 project, and 20 years of operation at the PVE Dlouhe Strane plant, both of which are conceptually similar to the proposed PVE.
The Danube is, primarily, a glacial river capable of excessive flow rates during the summer, whereas the Vltava is not. Positioned along both the Vltava and the Elbe (all the way to Strekov in Usti n L which is 140m above sea level), numerous barriers and dams have already been constructed. These provide a combined total of 800MW of available energy to the Czech Republic, and more are already in various stages of construction. However, during periods of drought, water levels are such that these are unable to meet demands. In fact, in the location below Strekov, it is not even possible for boats to float during those periods. From Strekov upwards, along both the Elbe and the Vltava, there is a well-constructed waterway for cargo boats. However, two weirs are missing, due to years of protestations from environmentalists. During such times of drought, releases from the PVE L-A into the Vltava would increase the river levels below Strekov by up to 31cm. This significant amount would benefit not only to the shipping fraternity, but would also help complete crucial sections of our waterways, thereby offering significant savings.
Financial returns for this 1000MW project have been calculated over a 12 to 15 year period of continuous plant operation. Designed from an ecological standpoint, the project will have minimal effect upon the environment. It is important to note that while the Vltava is generally acidic, water from the Danube is alkaline. Mixing of the two waters will help enhance the development of flora and fauna in the Vltava. The acidic effects upon the Danube should be minimal, due to the very considerable flow rates. In reality, since 1823, water from the Vltava has been conveyed to the Danube via the Schwartzenberg Canal. Implementation of this project will enable connection of 400kW of existing networks between the Czech Republic and Austria, a benefit to Central Europe as a whole.
