Steam Turbines as a mechanical driver can reduce operating costs by maximizing energy from fuel used in a facility.
The waste heat or process steam, created by the fuel can be converted into the power to drive the turbine,
 and replace, or avoid the need for an electric motor to drive equipment in the facility.

• Electric motors have been used as general purpose mechanical drivers for pump, compressors and other rotating equipment. Though they are usually inexpensive to install, they have a drawback that has an impact on the overall facility energy costs. It is the continual cost of electrical energy required to power the motor. When electricity and plant fuel costs were not as high as they are today, they were a good choice. Steam turbines provide the same power as motors, and the steam used to drive the turbine may be generated by utilizing the facilities' waste heat or process steam. The funds spent on fuel are well spent when the maximum amount of energy is used from it. See calculation at the bottom of this page for an example of the potential the savings of steam turbines and electric motors.

• When you produce steam at pressures above 50 psig, and then use it only for heat or a process, you have wasted an opportunity to reduce energy costs by either generating electricity or driving plant equipment. The steam pressure passed through a NESTCO turbine mechanical driver, reducing the pressure is worth three to four times the value of the heat removed from the steam. As an example of the overall economics, say you have a situation where you reduce 10,000 pounds of steam per hour from 150 psig to 15 psig today, using a pressure-reducing valve. Our turbine will produce 175-kilowatt hours of energy every hour for 1.27 cents per kWh, if your fuel cost is as above. If you are paying 4.0 cents per kWh from the electric company, this will save $4.78 per hour, or $40,000 per year. Such an installation will typically cost about $110,000, so it pays back the capital in less than 3 years. After that, you simply have $40,000 less to pay for energy every year.

• Large facilities such as medical centers, universities, and office buildings that generate heat can use the waste heat to generate electricity. These thermal users burn more fuel to make the heat that was just thrown away, in doing so they throw away the potential to make electricity, which is much more valuable than heat. Thermal users typically generate their steam at relatively high pressures so that they can feed their campus or large building with small steam pipes that carry a lot of energy, due to the high pressure. When the steam reaches the building where it will be used, and a pressure-reducing valve (PRV) is installed to lower the pressure, making it suitable for producing hot water or steam that goes to radiators or processes. The potential to make electricity is wasted. This raises the cost of energy and pollution.

• Our engineering staff can help you select a NESTCO turbine mechanical driver that will operate to capture the potential of your steam or waste heat to save electricity. The turbine removes the pressure portion of the energy of steam made, leaving just the heat that you need. This is the most efficient way to save electricity. 95% of the energy removed from the steam by our turbine replaces the electrical energy needed to drive you equipment. If your boiler converts fuel energy to steam with 85% efficiency, the overall efficiency of our turbine driver generators will exceed 70%. Compare this to the 33% average utility industry. It all happens because you will be using both the heat and electric potential always present whenever fuel is converted to steam.

• The value of electricity is typically much higher than your cost of making the extra steam. If you are paying $3.00 per million British thermal units for your fuel, (typical natural gas price) adding a million British thermal units of steam will cost you an extra $3.53. Our turbine generator set will convert that million Btu's into 278-kilowatt hours of electricity. At the average commercial price for delivered electricity throughout the U.S. of 6.5 cents per kWh, you will have produced electricity worth $19.64 with $3.53 worth of fuel. When using a steam turbine, a cost is allocated in the steam used to drive it. The cost in generating the heat or steam is incurred in the facility already. The overall costs in the facility operating costs don’t change, the return on investment in fuel costs are maximized.

• Steam cogeneration is the simultaneous production of electricity and useful thermal energy.  This means that you can generate electricity with the same steam you are now using for heating or a process. Cogeneration has also come to mean using waste fuel for in-plant electricity generation. Steam turbine generators make electricity by converting a steam pressure drop into mechanical power to spin a generator. High-pressure steam enters the turbine, drives the generator or other rotating equipment, and exhausts at a lower pressure for use in plant heating or process. Cogeneration saves money by allowing you to produce your own electricity for a fraction of the cost of utility power. Cogenerated power is cheaper because cogeneration systems can achieve fuel efficiencies of up to 80%, whereas the best utilities can do is about 40%.  Any company with a significant process steam use or surplus waste fuel.  Many companies are unaware of their great cogeneration potential.  Cogeneration systems can be designed into new boiler plants or can be easily added to existing boilers. Except with a cogeneration system installed, you need to buy much less from the utility.

• Many companies produce steam for process needs at a higher pressure than it is ultimately used for efficiency reasons in steam generation. This steam is usually passed through a pressure-reducing valve (PRV), which lowers its pressure and increases its temperature. A steam turbine can take that same energy available, reduce the pressure, and turn it into valuable electricity or power to drive equipment. A steam turbine does not consume steam; it only reduces its pressure. Most companies continue to buy some power from the utility and use the utility as a supplement to their cogeneration system.  Since the typical cogeneration system is connected in parallel with the utility, you can buy as much electricity as you need at any given moment, just as you do now. 

• In most cases, your existing boiler can be used to make the steam for cogeneration if it is operated at 100 psig or greater. The amount of fuel used depends upon the system design.  The turbine generator sets from NESTCO, for example, are ideal for use with oil or gas boilers and increase fuel use by only a few percent. When oil was inexpensive the need to generate power in discrete locations was not financially sound.  With the 1973-74 Arab Oil embargo everything changed and electricity prices and fuel prices have continually risen. Many companies are using internal sources of power; steam or waste heat to generate steam As utility rates increase, more companies are adding cogeneration systems to their power plants. If you have a waste fuel such as wood, waste elimination of waste disposal costs can be a very important benefit.

• Payback on a cogeneration project is often between one and a half to three years.  Payback is a function of power, system price, and electric savings.  The higher your current electric rates, the shorter the payback. Also, since equipment price per kW declines as power increases, the higher the power, and the more cost effective the system. Steam turbines have a service life of 20-years minimum; and are designed for 3 or more years of continuous duty at full load without shutdown for maintenance.  A generator features a service life of 20-years minimum. A small system generating 50 kW may cost $30,000.

Steam turbines drive pumps and other equipment for several reasons:

 Potential for lower operating cost versus electric drive.

Replacing a pressure reducing valve in the plant process and capturing mechanical energy in return.

Elimination of load losses normally encountered with a constant speed drive.

Return the maximum value for the costs incurred in generating the waste facility heat.

Steam turbines return savings when compared to electric motors. The savings can be substantial, relative to steam and electricity costs.

In example, if a pump or other rotating equipment requires a 300-horse power drive, an motor driver would cost roughly $94,232 annually, assuming 5 cents/KWH and 8,000 hours of operation.

If steam is generated from a gas fired boiler and the gas cost is $4.00/MCF, this same equipment could be operated for only $32,147, a savings of  $62,085 per year.

The following equations will yield the results referred to above in comparing the annual operating cost of a 300 HP pump using a steam turbine versus electric motor: