The economic viability of wave energy converters (WECs) depends on the cost and performance of their associated structural assemblies, ability to withstand large hydrodynamic loads, reliability, and design to minimize installation and maintenance activities. State-of-the-art rigid-body WECs suffer from high costs associated with construction, deployment, environmental fatigue, and premature failure. Inflatable wave pumps developed at NREL can produce power outputs that are comparable to those of traditional point-absorber technologies. However, unlike traditional rigid-body devices, NREL’s inflatable wave pumps have the potential to be significantly less expensive, more durable, and meet minimum operational lifetimes while minimizing logistic hassles of maintenance and repairs.
The National Renewable Energy Laboratory’s (NREL’s) inflatable wave pump is a wave energy converter (WEC) that uses low cost, flexible materials to absorb wave energy through the varying hydrostatic and hydrodynamic pressures at or below the water’s surface. The inexpensive materials may be rubber, rubber-coated fabrics, or other similar materials, which may reduce the need for marine-resilient coatings typically associated with steel or composite structures. NREL’s inflatable wave pump may include a low cost wave powered pump without mechanical seals or traditional rigid materials that have been correlated with corrosion and fatigue of state-of-the-art rigid-body WEC technologies.
NREL’s inflatable wave pump may operate as a constant-volume system that transfers energy, in the form of air pressure, into a diaphragm-type positive displacement pump with a spring that is used to provide a restoring force. As a wave passes over the submerged device, it compresses the air chamber, which expands the diaphragm. The diaphragm pushes and pulls water through a series of check valves to fill the pump chamber. As the pressure in the chamber is reduced, the spring restoring force from the diaphragm pushes air back into the air chamber and the cycle continues. Otherwise, the inflatable wave pump may have an air chamber that drives a piston, bellow, turbine, and/or linear generator.
To learn more about Inflatable Absorption Pressure Wave Actuated Pumps, please contact Erin Beaumont at:
Applications and Industries
- Pneumatic or hydraulic pumps,
- Desalination pumps,
- Electrical generators, and
- Shallow or deep-water installations
- The National Renewable Energy Laboratory’s (NREL’s) inflatable wave pumps’ structures can be more easily transported, either on land or by ship, to their final deployment location, as their reduced weight and compacted volume allow multiple devices to be transported at once. Ease of transportation may contribute to a drastic reduction in transportation and maintenance costs.
- NREL’s inflatable structures enable load-shedding techniques not possible with rigid-body wave energy converters (WECs), such as pressure releases via relief valves used during extreme wave conditions. Flexible load shedding can reduce the required design loads, translating into less expensive structural assemblies.
- NREL’s flexible bellow design eliminates the need for mechanical seals, a common failure mode for fluid power systems. Only static seals, which have the potential for a much longer design life, exist in NREL’s design.
- NREL’s flexible bellow also eliminates many moving parts increasing the reliability potential for the system, ultimately resulting in higher system availability and capacity factors.
- NREL’s design enables tuning of the spring constant and damping coefficient to tune an inflatable wave pump’s natural frequency and damping ratio to ambient wave frequencies for maximum power at resonance.