Quote:
Originally Posted by Big Dave
Tell you what, StorminMatt. Why don't you hit these guys websites and post to this forum the heat rates for these little turbines and prove me wrong.
I would be astonished if any of them get under 12,000 BTU/Kwh. A common diesel works in the 7,000 to 9,000 BTU/Kwh range.
Airplane designers like turbines for their reliability. A PT6 will has a MTBF of three pilots' careers. They are easy to maintain.
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Capstone does not provide this figure on their website. But according to Capstone, their 200KW turbine operating at 59F, 14.696psia, and 60% humidity has an exhaust gas temperature of 535F, and rejects heat at a rate of 1 350 000 BTU/hr. Under these conditions, the ELECTRICAL output is 190kW. If you divide 1 350 000 BTU/hr by 190kW, you get a heat rate of 7105 BTU/kWH - certainly not bad at all. Of course, this does not take into account ALL possible heat losses. But, unlike a piston engine, the VAST majority of heat produced by a turbine is lost through the exhaust.
Quote:
Originally Posted by jamesqf
The PT6 is also a design that's about 45 years old. Comparing it to what might be done today seems rather like comparing the O-360 in my Cherokee to my Insight's engine.
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Good point. Turbines in those days couldn't even achieve 20% efficiency, and were HORRIBLY dirty. High power output, light weight, low maintenance, and sleek, aerodynamic profile were the only things turbines had going for them at that time. But when Barcroft Labs at over 12000ft in California's White Mountains decided to ditch their aging diesel genset a couple of years ago, they chose a pair of Capstone turbines over another diesel genset. This certainy speaks volumes about modern gas turbines.