The Future
Pioneers
speed, the excess wind energy can be stored in the accumulator. This excess wind energy is released to the system when the wind speed is below the rated speed.
Power Regenerative HST wind turbine research platform: To demonstrate and validate the performance of the HST, we have successfully designed, constructed and commissioned a unique power regenerative test platform at University of Minnesota( UMN).
Figure3. Schematic of the testbed.
This testbed is one of a kind in the world. The testbed can simulate rotor torque generated from real wind profiles. It is a regenerative system consuming less power to operate. The testbed is instrumented with multiple sensors to accommodate and test a variety of hydraulic fluids, components and controls. It consists of two closed loop hydrostatic circuitsas shown in Figure 3. The block in dark gray is the HST under investigation. The other block is the hydrostatic drive( HSD), which is used to simulate the rotor driven by time varying wind. Instead of dissipating the turbine output power, the power is fed back to the HSD. A variable frequency driven electric motor is mounted
Figure4. PowerRegenerative HST windturbine research platform at UMN
on the turbine output shaft to make upfor the losses of the HST and HSD. Because of power regeneration, the research platform is capable of generating 105 kW output with only 55 kW of electrical input.
The power regenerative testbed is shown in Figure 4. It has pressure, temperature and flow sensor modules in the hydraulic line and torque sensors and speed encoders in the mechanical line. The testbed is equipped with 27 sensors to monitor the system performance and three analog inputs to control the testbed. It is incorporated with heat exchangers to maintain the temperature of hydraulic fluids. It is designed to operate at maximum pressure of 5000 PSI. It has safety valves to protect the hydrostatic circuit [ 5,6 ].
Significance of research:
This research will increase understanding of the HST for wind turbine applications. This will accelerate the development of wind power by increasing reliability, decreasing installation cost up to 12 %, reducing maintenance costs and improving the efficiency of distributed wind power generation. The main applications of distributed wind are residences, farms, small industries and institutions. With affordable prices, the distributed wind market will grow and contribute to our wind generation goal. This will also reduce millions of tons of CO2 emission and provide a cleaner environment for our next generation. The outcomes of the project will stimulate industry to develop more efficient hydraulic components, system and control for wind applications and contribute to our green economy.
Biswaranjan Mohanty PhD Candidate Department of Mechanical Engineering University of Minnesota, Minneapolis, MN 55455
References:
1. Wind vision report by Department of Energy, https:// energy. gov / eere / wind / wind-vision.
2. Distributed wind market report by Department of Energy, https:// energy. gov / eere / wind / downloads / 2015- distributed-wind-marketreport.
3. Sheng, S., Report on wind turbine subsystem reliability- a survey of various databases. National Renewable Energy Laboratory, Golden, CO, Tech. Rep. NREL / PR-5000-59111, 2013.
4. Thul, B., Dutta, R., Stelson, K. A., Hydrostatic transmission for mid-sized wind turbines, 52nd National Conference on Fluid Power, Las Vegas, USA, 2011.
5. Mohanty, B., Wang, F., and Stelson, K. A.,“ Design of power regenerative hydrostatic wind turbine test platform,” Proceedings of the 10th JFPS International Symposium on Fluid Power Fukuoka, Japan, Oct 2017.
6. Mohanty, B., and Stelson, K. A.,“ Characterization and calibration of a power regenerative hydrostatic wind turbine test bed using an Advanced Control Valve,” Proceedings of the 11th International Fluid Power Conference, Aachen, Germany, March 2018.
august-september 2018 | Global MDA Journal | 45