Capstone MicroTurbines Have Many Uses
Bill Siuru, PhD, PE, is a technical writer based in Temecula, California, U.S.A.
Capstone MicroTurbines have been used in a very large number of diverse applications. These range from the “Whisper Eco-Logic,” a prototype Ford S-Max crossover vehicle converted to a series hybrid, plug-in vehicle to a new C1000 MicroTurbine energy system that can produce up to 10 MW of power. Other applications include Secure Power (SP) systems to provide backup power for critical operations during grid outages, cogeneration, which is combined heat and power (CHP), and trigeneration, which provides cooling, heating and power (CCHP).
There are even Designline hybrid-electric urban transit buses that use MicroTurbines. To date, the company has sold some 4000 MicroTurbine systems to customers worldwide, which have logged millions of operating hours.
All these applications are based on one of three basic building blocks, the C30, C65 and C200 MicroTurbine models. The designations refer to their rated electrical outputs, which are 30,
60 or 200 kW, respectively. Their integrated generators can produce alternating current (AC) and direct current (DC) power. Exhaust from MicroTurbines, at about 300° to 400°C, contains approximately 70% of the energy that was originally stored in the fuel. This energy can be used for heating and cooling.
The Capstone MicroTurbine can operate on a very wide range of fuels including natural gas, biogas, diesel, propane and various forms of kerosene like JP4 commercial jet fuel or JP5/JP8
military fuels. Natural gas, both low and high pressure, is particularly attractive because of its widespread availability, relatively low cost and low polluting emissions. The MicroTurbines can also run on biogas, including methane produced at landfills and water treatment plants. For example, a system of 10 C30 MicroTurbines runs on methane at a Sheboygan, Wisconsin, U.S.A., wastewater plant and a C30 operates on methane produced from manure from 1000 dairy cows at the Den Dulk Dairy in Ravena, Michigan, U.S.A.
Capstone MicroTurbines can also operate on flare and wellhead gases. For instance, Capstone is supplying C30-based MicroTurbine systems for offshore oil platforms located in the Gulf of Mexico to provide 24/7 power and heat. Operating on wellhead they are one-third smaller than equivalent generators and are designed for use in hazardous areas.
The MicroTurbines are designed to be low maintenance, with only a single moving part a single turbine/ compressor shaft with an integrated generator. This moving part, rotating at 96 000 r/min, rides on patented air bearings that never require lubrication.
Air cooling eliminates the need for a radiator, water pump, thermostat, hoses, belts or external accessories needed by diesel or natural gas gensets. Recommended maintenance includes replacing the air filter at 8000-hour intervals and factory engine servicing after 40 000 hours of intermittent or continuous use.
The new C1000 Power Package can marry together up to 10 C1000 units to produce 10 MW of electric power as well as heat. Each C1000, in turn, uses five C200 MicroTurbines all contained
in a single 2.4 x 9.1 x 2.9 m ISO container. Operating on clean natural gas, the reduced CO2 emissions from each C1000 unit is equivalent to taking 700 average passengers off the road or
planting 730 acres of pine and fir forests. There are also significant reductions in other emissions and the system can meet stringent California Air Resources Board (CARB)requirements.
The C1000 provides 400 to 480 Vac, three-phase, four-wire power at 30 to 33% efficiency over the 200 to 1000 kW operating range. This is much higher than the typical turbine efficiency. By starting each C200 only when the load demands more power, each one can operate at peak efficiency, and not at lower partial load efficiencies, which is the case with a single turbine. Capstone also offers similar units with 600 and 800 kW capacities. As with other products, other fuels could be used.
Another interesting application is for peak-load reduction. Here, the MicroTurbine supplements or replaces grid power during peak load times. This results in cost savings by using lower-cost natural gas during high-rate daytime hours or reducing grid power
demands so electric power doesn’t have to be purchased at higher tier rates. This peak-load reduction technology is now in use at resorts, hotels, landfills and in industrial settings. Incidentally, landfills use methane from decaying refuse. As an example, Capstone uses such a system at its plant in Chatsworth, California, U.S.A. Here seven C65 units are online between 1 to 5 p.m. when loads are greatest, especially cooling loads. For cooling, Capstone has teamed
up with Carrier for the refrigerationrelated components.
Capstone sees even further applications for its technology. For example, in conjunction with another company, it is developing an “Eco-Pod,” which is a grid-independent, natural gas-fueled, self-contained electric vehicle charging station for all-electric and plug-in hybrid vehicles. The company is also working on integrating a MicroTurbine with a large solar collector that would concentrate sunlight on a receiver to heat air to drive it. At night, traditional fuels would be used to provide around the clock electrical power.