A Clean Energy Generation System of In-Tandem Combinations Each of Heat Pump, Compressor and Turbine in Wind Tunnel

Abstract

This is a series of in-tandem combinations each of heat pump, air compressor, and air turbine disposed in a wind tunnel, working together to generate clean/renewable electricity. The air compressor, located at downstream of the preceding air turbine, extracts air from this turbine thus reduces its backpressure and causes pressure drop at the turbine exit. Turbine output work Wtb is proportional to temperature difference (T3-T4) of turbine inlet/outlet air, which varies exponentially with turbine outlet/inlet air pressure ratio P4/P3 in adiabatic process as below: Wtb = MCp (T3-T4) = MCpT3{1-P4/P3(1-1/k)} as T4=T3(P4/P3)(1-1/k) where, M=mass flow rate of air; Cp&Cv=constant pressure/volume specific heat capacities of air; k= Cp/Cv=1.4. An ASME paper [1] verifies that a suction blower put at turbine exit reducing back pressure of 200 mbar can increase turbine inlet/outlet air pressure ratio P3/P4by 25%. Therefore, Wtb becomes more than those turbines without such blowers as (T3-T4) becomes larger, thus this unique Clean Energy Generation System of Heat Pumps, Compressors, and Turbines (HPCT system) achieves producing net useful electric power. In HPCT system, each air compressor works efficiently to reduce air pressure at preceding turbine outlet, as it extracts more air from the turbine than the blower mentioned in the ASME paper, because compressors have higher compression ratio than blowers. Thus, such feature gives higher turbine pressure ratio to each combination of HPCT system than those turbines without blowers (or compressors) to reduce back pressure at turbine exit. Therefore, HPCT system of higher turbine air pressure ratio P3/P4 achieves producing more turbine output work, as air temperature at turbine exit simultaneously drops more when P3/P4 becomes larger. Heat pump is an efficient device to move heat from low-temperature source to high-temperature sink, and geothermal heat source is preferable as it provides steady and warmer heat energy. This “moved” heat is used to heat up the air in wind tunnel to offset the energy extracted by turbine from HPCT system. Also, HPCT system is fully thermally insulated, thus theoretically being of zero heat loss, as it works adiabatically. P-V&T-S curves and performance of each combination of HPCT system working cycle are studied to compare it with actual gas turbine cycle and ideal Brayton cycle. Working examples of HPCT system are presented to simulate practical applications of HPCT system, and find out virtual net useful output work and energy efficiency. HPCT system is a “COLD” Engine of Zero Carbon Emission, works under moderate energy efficiency and with higher energy density than most existing renewable energy generation systems. More importantly, it is a simply designed system using only conventional knowledge, and can be made by the existing technology under the least investment risk.