Diesel engines, battery requirements

Gas turbines are usually started by a DC motor or an air motor. Either system is available for most turbines up to about 20 MW. Occasionally AC motors are used. Beyond 20 MW, when heavy industrial machines tend to be used, it becomes more practical to use air motors or even diesel engine starters. DC motors require a powerful battery system. The DC motor and battery systems tend to be more reliable and less space consuming, which is important for offshore systems. Air motors require air receivers and compressors. The compressors require AC motors or diesel engines. Air start and diesel start systems are more popular for onshore plants especially remote plants, e.g. in the desert. This is partly due to the fact that batteries tend to suffer from poor maintenance in hot, dry locations. Air systems require regular maintenance and must be kept fully charged in readiness for a quick start. Air system receivers can become very large if more than three successive starting attempts are required. More starts can probably be obtained by a battery system that occnpies the same physical space. 

The combined means to provide emergency power (such as by means of water, steam or gas turbine, diesel engines or batteries) shall have a reliability and form that are consistent with all the requirements of the safety systems to be supphed, and shall perform their functions on the assumption of a single failure. It shall be possible to test the functional capability of the emergency power supply. 

Efficient autonomous portable power generators are required due to the common use of portable electrical and electronic devices, such as laptop computers and cell telephones. Currently, rechargeable batteries are the predominant technology for these applications. Moreover, mobile power generators are needed for residential and recreational purposes to replace small combustion engines, for example diesel generators on board (sailing) yachts. In all these applications, small FP-FC systems are convenient alternatives. 

In selected cases described in this section, batteries provide the main source of propulsion of the vehicle. However, hybrid systans are beconung more popular due to their specifications flexibility and variety of different power source devices available for hybridization [45]. In hybrid power systems, batteries can be coupled with fuel cells, capacitors, supercapacitors, hydrocarbon fuel engines, or diesel generators. The role of the battery in such hybrids is typically to assist in loadbalancing and/or to provide more efficiency in meeting power requirements [46]. More detailed discussion of hybrid power systems is included in Chap. 6 of this book. 

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