A Feasibility Study - Aaltodoc - Aalto-yliopisto

8 AaltoRO concept
The main purpose of AaltoRO concept is to produce fresh water with wave power and
reverse osmosis. The concept comprises of two major components: the Wave Energy
Converter (WEC) and the Reverse Osmosis (RO) unit connected by a hydraulic system.
The fundamental operating principle is that the WEC absorbs energy from the waves,
pressurizes seawater, which is then led to the RO unit where salt ions and fresh water
are separated. End results from the process are fresh water and brine (water with a high
concentration of salts).
The process proposed by AaltoRO can be achieved through many different assemblies.
Most of the components can for instance be located in the WEC, so that it would be as
autonomous as possible. Depending on the location and the suitable materials, it might
be cost-effective to pressurize the water only to e.g. 20 bar at the WEC and increase the
pressure onshore. Another alternative would be to use the energy from the brine to
produce electricity or to transfer the pressure directly to the incoming seawater.
The choice of the optimum configuration is not easy to determine, since each variable
has its own advantages and disadvantages and they also interact. The following
restrictions on the configuration of AaltoRO have been decided: The majority of the
components will be situated onshore in order to ease maintenance and repair work. Only
the direct pressurization of seawater is examined, not electricity production. All the
other choices of the configuration will be made according to each situation.
This Chapter presents the major components of the AaltoRO concept in the following
order: First the Wave Energy Converter (WEC) is discussed. Second is a detailed
description about the hydraulics (e.g. adaptive pressure generator (APG) and the
pressure drop during the transfer of seawater to shore). Third is the reverse osmosis
(RO) unit, which encompasses e.g. pre- and post-treatment options for seawater, the
function of the actual reverse osmosis membranes and utilization of the highly energetic
brine with an Energy Recovery Device (ERD). A schematic of AaltoRO is given Figure
25.
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