No matter how much these cost, they are sure to be a bargain in the eyes of various California bureaucrats.

HG: Somebody will, sooner or latter, find ways to produce very low cost equivalent micro-turbines. They have the potential to become the ideal e-range extender, specially when powered with NG, SG, CNG or CSG or compressed hydrogen.

Capstone should not give up and create JVs with lower cost producers in China and/or India.

Right:
"they don't scale down well." (not true – they scale down really, really badly)

"They don't like starting and stopping" (esp. with foil bearings),

"they don't like running at part load" (efficiency, already very low, drops like a rock).

"Great for [quick reaction backup] at a central power plant," but only WITH, topping and/or bottoming, multiple $tages of regeneration and/or $$ reheat and/or $$ recuperation; all big buck$.

"they don't scale down well" - because nobody really invested into R&D same money as into any other ICE

A diesel engine may as well be called a gas turbine with a moving combustion chamber in-between. A piston engine does have more moving parts but it has simpler parts and possibly less parts (with few cylinders) and these parts are exposed to lower average temperatures and the power transmitting parts run at lower speeds.

One option could also be to use a large turbocharger with a high compression ratio (or 2 turbochargers in series) and a reciprocating engine with a low compression ratio (or atkinson-cycled): Essentially a gas turbine with a comparatively small moving combustion chamber and a high BMEP (= high power density). In a range extending application turbo-lag is irrelevant.

Small gas turbines are usually designed with centrifugal compressors to avoid the gas leakage problem around blade tips experienced with axial flow designs. This design choice also makes the compressor more compact since fewer stages are required to achieve a given pressure ratio.

A few thoughts on responses:

-Just Capstone PR doing there job to advertise whatever good news they can since there is so little of it.
-micro gas turbine generator makes little sense in this application. Bus market is extremely cost sensitive as their operators have little money of their own to spend and users aren't typically willing to pay a premium for better service. Buses are not weight limited so whatever advantage a gas turbine offers in weight savings is of little value. Any benefit in physical size reduction is moot given the poor energy storage efficiency of CNG and low efficiency of small gas turbines. if somebody wants or their is a need for a clean PHEV bus, they'd be better off using a simple ICE regardless of the fuel.
-@ToppaTom- Well said
-@Engineer-Poet- Right on
-@Harvey D- you can't discount heat engine efficiency if you are concerned with GHG. Except for a handfull of countries who are already invested on nuclear, geothermal, or other non HC fuel source, most countries electrical grid produces as much CO2 by the time it gets to an electric car as does a modern ICE. This can be improved but it will take decades and trillions of dollars so it can not be ignored.
-@SJC-stop start is definitely a great candidate for hybridization, but not so much for an ORC. Need high quality (high temp) heat and stop start is not conducive to this operating environment. Several recent studies have been conducted by NAS and other reputable scientific groups, all of which have shown that the economics don't come close to working for ORC until fuel prices increase by several times.
-@Mannstein- centrifugal compressors suffer tip leakage too. small gas turbines use centrifs to keep them simple and low cost. you can get upwards of 6:1 pressure ratio with good efficiency in a single stage on a centrif which would usually take 4 axial stages. multi-staging a centrif becomes tricky so it isn't often done so if you want to go to higher pressure ratios and use actively cooled turbines, then axial machines are the only way to go.
-@Aussie- Though i agree that $35/kw isn't a bad number for diesel engines, real engine costs are not well represented by such a simple metric. it depends heavily on other factors, such as emissions level, production volumes, BSFC, expected duty cycle, life. As an example, heavy duty engine costs have doubled in developed markets in the past decade due to emissions regulations with negligible improvement in fuel efficiency or durability. At any rate, suffice it to say that we looked at costing out a recuperated gas turbine in this power range for automotive use and came to a figure closer to 2-3X what an ICE costs in volumes 10,000 - 100,000/yr.

UA

globi, you just re-invented the Hyperbar engine.

EP, I was more thinking of a set-up similar to what was used in the JCB Dieselmax speed record vehicle (compression ratio of this diesel engine was only 10.5).
However, I don't think power to weight/volume ratio is really an issue in a bus application. But what if Chrysler needed a small gasoline or CNG range extending engine in a larger car and Fiat would provide its 2 cylinder gasoline engine with a relatively large turbocharger and lower this engines compression ratio accordingly. This would be more sensible than using an expensive gas turbine - as, for instance, was tested in the GM EV-1. Since the turbo-lag is irrelevant and the axis of the turboshaft is not connected to the crank, this system could also be arranged more flexibly. In addition, a heavier and larger IC-engine may be more efficient, but it will require more space and reduce the cars efficiency when the car runs on battery power.

Oh, by the way an EV emits significantly less CO2 per km than a conventional vehicle even with the US-mix and over 50% coal:
http://web.mit.edu/evt/summary_wtw.pdf
Needless to say that oil has to be imported and coal does not and an EV does not have any short-distance inefficiency issues.
Also, a photovoltaic carport produces enough electricity to power an EV. (Whereas a corn field on a roof would not provide lots of ethanol).

300 square feet of PV on a roof would go a long way towards helping the grid and charging EVs, but who will pay the $30,000 for the PV? Many people would rather spend that putting in a swimming pool that costs them $1000 per year than putting in a PV system that saves them $1000 per year. Until we can change that mindset we will make little progress.

28 m2 at 15% PV efficiency = 4.2 kW. 4.2 kW at 17% capacity factor = 6300 kWh = enough to drive over 45,000 km per year with an EV. In Germany complete PV systems are meanwhile sold for €2.2 /W. That's €6600 for a 3 kW system.
But of course people will only install these systems if they can benefit from feed-in tariffs (the US spends a 100 times more on its military than what Germany spends on feed-in tariffs with German jobs and reduction of fuel imports).

We have the equivalent to feed-in tariffs in the Phoenix area and installed PV still makes much less economic sense as you approach the break even point.

And we speend 100s of times less on it than Germany spends on its military.