WAVENERGY.it S.r.l.

The WAVENERGY.it S.r.l. is a limited-liability engineering company, which was set up in September 2005. The company is at present an academic Spin-off of the “Mediterranea” University of Reggio Calabria, with registered office in Via Francesco Baracca, trav. De Salvo , n. 8/a, 89123, Reggio Calabria (Italy).

The WAVENERGY.it S.r.l. has been established with the purpose to work in the design, maintenance, control, monitoring, and management of:

1. Plants for the conversion of wave energy into electrical power; that are the classical OWC (Oscillating Water Column) devices or the innovative REWEC3 (REsonant Wave Energy Converter realization 3) systems;
2. Plants producing electricity from renewable energy sources in the marine field (such as, for example, offshore wind farms or plants for the production of energy from sea currents);
3. Plants for the absorption of wave energy (such as submerged breakwater, like the REWEC1 systems, which can be adopted also for the protection of coasts).

The company Wavenergy.it LTD was founded by prof. Felice Arena in September 2005 and, as previously mentioned, it is an academic Spin-Off: all promoting members were teachers and doctor (PhD) at the “Mediterranea” University of Reggio Calabria. The request for recognition as a spin-off company was made at the “Mediterranea” University of Reggio Calabria in June 2009. The Wavenergy.it LTD has been recognized as Spin Off of the Mediterranean University in July 2010. The REWEC3 device was conceived by Professor Paolo Boccotti (full professor on Ocean Engineering at Mediterranea University of Reggio Calabria) and patented by him both in Italy (Patent N.1332519) and in Europe (Patent N.EP1518052B1). Wavenergy.it LTD is the licensee exclusive of the patents. For further details on the open and past projects please go to the projects&events section on the website.

A brief overview of the REWEC3 technology

The REWEC3 device is composed by a chamber containing a water column in its lower part and an air pocket in its upper part. The air pocket is connected to the atmosphere via a small duct hosting a self-rectifying turbine. In addition to that, a REWEC3 includes a small vertical U-shaped duct for connecting the water column to the open sea. The working principle of the system is quite simple: by the action of the incident waves, the water inside the U-shaped duct is subject to a reciprocating motion (Fig. 1). This motion induces alternately a compression and an expansion of the air pocket, which generates an air flow in the air duct. A turbine coupled to an electrical generator, installed into the air duct, is driven in this way to produce electrical energy. From a design perspective, the main feature of the REWEC3 is the fact that the natural period of the water column inside the plant is determined at the preliminary design stage in order to match a desired period.

Figure 1. Working principle of a Resonant Wave Energy Converter 3. Left panel: behaviour under wave crest action. Right panel: behaviour under wave trough action.

From an engineering perspective, the REWEC3 compared with a conventional OWC introduces substantial improvements, useful in the perspective of wave energy exploitation. Specifically,

• The opening is closer to the sea surface. This feature induces less attenuation in the wave pressure exciting the device. So that, more energy is available being equal the incident sea state.
• The REWEC3 cross-section, compared to a classical OWC, is U-shaped. This new configuration does not introduce significant modifications in the structural feature, but radically changes the physics of the plant with respect to classical OWCs. Sea waves do not propagate to the inner pneumatic chamber, but the oscillations of the water surface inside the chamber are induced by the wave pressure fluctuation at the opening of the vertical duct. Further, an additional mass is provided to the system. This fundamental property allows for achievement of the natural resonance without the use of any phase control devices required in the conventional OWC.
• The natural resonance significantly enhances wave energy absorption in comparison with conventional OWC; that is related to the facts that: a) the resonance could be achieved also at high frequency (low period) useful for the exploitation of the wave energy resource even in the Mediterranean Sea characterized by small incident mean wave power (in deep water in Civitavecchia that is about 2.25 kW/m in average during the year, when in the Atlantic coasts of Spain and Portugal it is between 30 and 60 kW/m in the year); b) the natural period of oscillation of the water column inside the pneumatic chamber can be tuned, during the design stage, to the desired period (to which the greatest amount of available wave energy resource is associated), allowing for maximizing the energy harvested by the REWEC3 collector at the considered location. In Civitavecchia, the seas with significant wave height between 2 m and 3.5 m are the design sea states utilized for tuning the eigen-period of the water column oscillations.

Some estimation of electricity production of the new REWEC3/U-OWC

Some examples of production of electrical power from REWEC3 devices are shown in Table 1 both for locations in the Central Mediterranean Sea as well as off the West coast of USA (California).

Table 1: The mean production (in 1 year) for a REWEC3 plant with a length of 1 kilometer