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Wave energy conversion is a promising field of renewable energy, but it still faces several technological and economic challenges. One of these challenges is to improve the energy efficiency and adaptability of Wave Energy Converters to varying wave conditions. A technological approach to solve this efficiency challenge is the negative spring mechanisms illustrated in recent studies. This paper proposes and analyzes a novel negative spring technological concept that dynamically modifies the mass and inertia of a Wave Energy Converter by transferring seawater between its compartments. The added value of the presented technology relies on interoperability, ease of manufacturing and operating, and increased energy efficiency for heterogeneous sea states. The concept is presented in two analyzed alternatives: a passive one, which requires no electrical consumption and is purely based on the relative motion of the bodies, and an active one, which uses a controlled pump system to force the water transfer. The system is evaluated numerically using widely accepted simulation tools, such as WECSIM, and validated by physical testing in a wave flume using decay and regular test scenarios. Key findings include a relevant discussion about system limitations and a demonstrated increase in the extracted energy efficiency up to 12.7% while limiting the maximum power extraction for a singular wave frequency to 3.41%, indicating an increased adaptability to different wave frequencies because of the amplified range of near-resonance operation of the WEC up to 0.21 rad/s.

Wave energy conversion is a promising field of renewable energy, but it still faces several technological and economic challenges. One of these challenges is to improve the energy efficiency and adaptability of Wave Energy Converters to varying wave conditions. A technological approach to solve this efficiency challenge is the negative spring mechanisms illustrated in recent studies. This paper proposes and analyzes a novel negative spring technological concept that dynamically modifies the mass and inertia of a Wave Energy Converter by transferring seawater between its compartments. The added value of the presented technology relies on interoperability, ease of manufacturing and operating, and increased energy efficiency for heterogeneous sea states. The concept is presented in two analyzed alternatives: a passive one, which requires no electrical consumption and is purely based on the relative motion of the bodies, and an active one, which uses a controlled pump system to force the water transfer. The system is evaluated numerically using widely accepted simulation tools, such as WECSIM, and validated by physical testing in a wave flume using decay and regular test scenarios. Key findings include a relevant discussion about system limitations and a demonstrated increase in the extracted energy efficiency up to 12.7% while limiting the maximum power extraction for a singular wave frequency to 3.41%, indicating an increased adaptability to different wave frequencies because of the amplified range of near-resonance operation of the WEC up to 0.21 rad/s.

A schematic diagram of a transport hybrid power plant using a new design RPE-4.4/1.75 rotary piston air engine is proposed. Its external speed characteristic is determined, according to which the maximum engine power is 8.75 kW at 850 rpm and the maximum torque is 127.54 N∙m at 400 rpm. For various gears and speeds, all the components of the power balance were determined and the dynamic characteristic of the hybrid car was obtained when operated on an air engine. According to the dependences of the power balance, the total traction force from the rotary piston air engine on the driving wheels is 5 kN. The performance of acceleration of a hybrid car while working on an air engine is estimated, namely, the dependences of acceleration, time,and acceleration path are obtained. In urban traffic, the required time to accelerate the car to a speed of 60 km/h is 15.2 s and the path is 173 m. The possible drive range of the hybrid car on compressed air without additional recharging is analyzed. On one cylinder with compressed air with a volume of 100 liters, an initial pressure of 35 MPa, and a final pressure of 2 MPa, the hybrid car can travel about 26 km.

A schematic diagram of a transport hybrid power plant using a new design RPE-4.4/1.75 rotary piston air engine is proposed. Its external speed characteristic is determined, according to which the maximum engine power is 8.75 kW at 850 rpm and the maximum torque is 127.54 N∙m at 400 rpm. For various gears and speeds, all the components of the power balance were determined and the dynamic characteristic of the hybrid car was obtained when operated on an air engine. According to the dependences of the power balance, the total traction force from the rotary piston air engine on the driving wheels is 5 kN. The performance of acceleration of a hybrid car while working on an air engine is estimated, namely, the dependences of acceleration, time,and acceleration path are obtained. In urban traffic, the required time to accelerate the car to a speed of 60 km/h is 15.2 s and the path is 173 m. The possible drive range of the hybrid car on compressed air without additional recharging is analyzed. On one cylinder with compressed air with a volume of 100 liters, an initial pressure of 35 MPa, and a final pressure of 2 MPa, the hybrid car can travel about 26 km.

AbstractThis paper assesses how parameter uncertainties in the model for rise velocity of CO2 droplets in the ocean cause uncertainties in their rise and dissolution in marine waters. The parameter uncertainties in the rise velocity for both hydrate coated and hydrate free droplets are estimated from experiment data. Thereafter the rise velocity is coupled with a mass transfer model to simulate the fate of dissolution of a single droplet.The assessment shows that parameter uncertainties are highest for large droplets. However, it is also shown that in some circumstances varying the temperature gives significant change in rise distance of droplets.

AbstractThis paper assesses how parameter uncertainties in the model for rise velocity of CO2 droplets in the ocean cause uncertainties in their rise and dissolution in marine waters. The parameter uncertainties in the rise velocity for both hydrate coated and hydrate free droplets are estimated from experiment data. Thereafter the rise velocity is coupled with a mass transfer model to simulate the fate of dissolution of a single droplet.The assessment shows that parameter uncertainties are highest for large droplets. However, it is also shown that in some circumstances varying the temperature gives significant change in rise distance of droplets.